New World Winemaker Blog » Karien O'Kennedy

Lactobacillus – the good, the bad and the ugly

Karien O'Kennedy — Thu, 03 May 2012 10:12:08 +0000

My husband is obsessed with this movie and the theme song. It was his cell phone ring-tone for a while – a long while actually – drove me bonkers. I guess that is why it was the first title that popped into my head when I thought of how to describe Lactobacillus in winemaking. It used to be the bad and in many cases the ugly. If you look at articles on stuck fermentations and wine spoilage from a few years ago, Lactobacillus almost always features somewhere in the article as one of the main culprits. So it is not surprising then that sales attempts to sell Lactobacillus starter cultures for malolactic fermentation are often greeted with GREAT resistance, aggression, jaw dropping, gawking or a call for Security.

Well folks you can pick up your jaws because it seems that there are “good” guys amongst the bad and ugly ones. The two companies that are taking the lead on commercializing some good guys are Oenobrands and Lallemand. The Lallemand culture V22 is a pure Lactobacillus plantarum culture from European origin and can be used for both co-inoculation during alcoholic fermentation as well as sequential inoculation after alcoholic fermentation. The Oenobrands product, marketed under the Anchor brand and called Anchor NT 202 Co-Inoculant, is a blend of selected Oenococcus oeni and Lactobacillus plantarum strains. These strains are South African isolates.

Okay, I know what your minds are screaming…VA! Indeed something to scream about. But not in this case. These two commercial Lactobacillus plantarum cultures are homofermentative. That means they can utilize only malic acid as a carbon source to form mainly lactic acid. Other Lactobacillus strains (often present in spontaneous MLF’s) as well as Oenococcus strains are heterofermentative, meaning they can also utilize grape sugars and citric acid and as a result form acetic acid. However, reputable commercialized Oenococcus oeni MLF starter cultures, although heterofermentative, strongly prefers malic acid as carbon source (they have been selected because of this), even during co-inoculation where grape sugars and citric acid are present in high concentrations. Not all starter cultures are suitable for co-inoculation though.

Okay so why Lactobacillus? In the case of Anchor NT 202 Co-Inoculant the Lactobacillus plantarum in this mixed culture brings aroma and roundness to the party. The Oenococcus is the workhorse bringing, security and speed to the party. The application of NT 202 Co-inoculant is also rather simplistic. You add equal amounts of sachets of bacteria and packets of NT 202 wine yeast to the juice, at the same time, before the onset of fermentation. No waiting for 24 hours. No extra calculations. Scientific research has shown this Lactobacillus plantarum strain to have a very different enzyme profile to Oenococcus oeni in general and as a result the typical varietal character of red grapes, specifically monoterpenes and norisoprenoids, are released from their non-aromatic precursors, thereby increasing wine aroma and thus quality.

So while you still need to do your best to keep the “bads” and the “uglies” out of your wines, experimenting with the “good guys” might just give you that kick @$$ competitive edge you strive to achieve in your wines…

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Concrete egg tanks

Karien O'Kennedy — Wed, 04 Apr 2012 12:37:32 +0000

“Large egg-shaped vessels have been appearing in increasing numbers at high end wineries on the West Coast, stirring a mixture of bafflement, warm, return-to-the-womb associations and fears of an alien invasion…” Field Maloney, Wine & Spirits, February 2009

Very funny intro. Alien invasion is exactly what describes the image that went through my head when I saw these egg shaped tanks for the first time. I immediately thought of the 1993 movie: Coneheads, hence the image. From the moment I saw a picture of these tanks – and I must embarrassingly admit it was only last year – I have wanted to investigate this amusing (to me) new movement in winemaking. It looks rather funny in a cellar. It looks like a giant hatchery where large prehistoric flying reptiles are about to emerge from any second.

The tanks are made from concrete and they are in an egg shape. Why the concrete? Well apparently concrete allows for a micro oxygenation effect on the wine like barrels do, except without adding wood flavors. Why the egg shape? It apparently creates a vortex in the wine and allows for lees to stay in suspension so stirring is not necessary. Lees in suspension has various advantages, hence the practice of batonnage.

The mastermind behind these tanks is Marc Nomblot who on request of biodynamics winemaker, Michel Chapoutier, built the first one in 2001. This caught on quickly and to use the the description of Jeffrey Iverson, these egg shaped tanks are now “hatching in wineries all over the world.”

I recently visited the hatchery of Boekenhoutskloof winery in Franschhoek, South Africa (yes the eggs have reached the southern tip of Africa). They ferment Grenache blanc in their eggs. They start fermentation in stainless steel tanks on skins, so no settling, and press anywhere from 25 – 50% into the fermentation. The must is then pumped with all its lees into the eggs. Fermentation is conducted at 16 – 18°C; they use a coil for cooling (Franschhoek is a tad warmer than the Rhône). The coil only goes into the egg for about an hour at a time. These concrete eggs are great insulators, compared to stainless steel that is conductive. Fermentation is about seven to ten days with Lalvin ICV-GRE yeast (Lallemand). After fermentation the wine stays in the eggs for 10 months. To the winemaker the biggest attribute from using the eggs is the incredible mouthfeel one can obtain this way. This Grenache blanc forms part of of a white blend called Wolftrap white. Even though Boekenhoutskloof is not a biodynamic winery they do embrace some of the principles, such as these egg tanks, and plan to expand their hatchery on an ongoing basis. They have also started to expand the usage to other grape varieties.

So certainly with “biodynamic”, “natural” and “non-interventionist” winemaking being the buzz words at the moment, I reckon these eggs are here to stay for a while. Personally I believe in interventionist winemaking, but here is a concept that even makes sense to me. I’m just not so sure about racking during certain moon cycles though. ..

Boekenhoutskloof winemaker Jean Smit and some of their eggs.

Karien O’Kennedy is the Online Communications Manager for Oenobrands and knows the odd thing or two about fermentation and winemaking.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Wine yeast nutrients 101

Karien O'Kennedy — Tue, 14 Feb 2012 13:07:10 +0000

Various parts of dead yeasts can be used as a source of nutrition / alcohol tolerance for live yeast cells during fermentation. Sometimes they are used in combination with inorganic nitrogen such as DAP and sometimes they are used on their own. Here is a short explanation of the different types:

Inactivated yeast – the whole yeast cell has been killed by heat. It contains the cell wall, the cell membrane and the whole inside of the yeast. Inactivated yeasts are a source of vitamins, minerals and to a lesser extend amino acids. As the alcohol content of the must increases during fermentation the dead yeasts’ cell membranes become more and more “leaky” and more of the inside goodies of the dead yeasts leak out to the must where the live yeasts can take it up. This does not happen to live yeasts since live ones can regenerate their cell membranes. They can keep it together so to speak. Inactivated yeasts are found in products such as Fermaid K and E (Lallemand) and Maxaferm and Nutrivin (Oenobrands).

Yeast autolysate – the whole yeast cell is killed and then exposed to lytic enzymes at 45°C for a certain time period. The result is that the cell wall, that contains glucans, is partially degraded and the cell membrane and the “soluble inside” of the yeast are more exposed, and therefore more available, to the hungry fermenting yeasts (cannibals) lurking around for a bite. Commercial examples are Natuferm (Oenobrands), Go-FermProtect (Lallemand) and Dynastart (Laffort). These products are usually added separately from inorganic nitrogen. They are applied for specific purposes and they are more effective than normal inactivated yeast. Apart from the normal role of nutrition they also do the following: Natuferm = aroma enhancement, especially esters; Go-Ferm Protect = source of sterols and Dynastart = aroma enhancement, especially thiols.

Yeast cell walls /hulls / ghosts – this is the insoluble yeast cell wall fraction of yeast autolysate after centrifugation. Depending on the washing process used during the manufacturing of yeast hulls, they may or may not contain parts of the cell membrane. Commercial examples are Extraferm (Oenobrands) and Springcell (Bio-Springer). Technically they are not nutrients, they detoxify the must from medium chain fatty acids produced by sluggish yeasts.

Yeast extract – the supernatant of yeast autolysate or in plain English: the soluble insides of yeast cells once the insoluble cell walls and cell membranes have been removed. This is found in Superfood (Vinotec).

Specific yeast fractions – e.g. mannoproteins. Mannoproteins are a specific cell wall constituent and production thereof requires further processing of yeast cell walls. Technically they are not nutrients either. They assist with tartrate stabilisation and mouthfeel. Commercial examples are Claristar (Oenobrands) and Mannostab (Laffort).

For more detailed info on the topic go the technical article with the same title.

Karien O’Kennedy is the Online Communications Manager of Oenobrands and knows the odd thing or two about winemaking and fermentation.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

What’s in the bag?

Karien O'Kennedy — Fri, 03 Feb 2012 12:51:22 +0000

The cat is out of the bag so to speak. It seems that not all tannins are created equal and quality differences between suppliers exist. Best you make sure you buy from a trusted supplier…

I recently read an interesting (also from a date of publication point of view) article, published in a reputable scientific journal called: “Impact of exogenous tannin additions on wine chemistry and wine sensory character.” They analyzed the effects of a range of enological tannins in Merlot wine. First they analyzed how much of the product sold as tannin was indeed tannin. They found it to be “12 – 48%.” What is the rest of the stuff in the bag that you are adding to your wine??? They found that adding the recommended dosage of the supplier was too little to have a “measurable effect.” They then proceeded to add higher concentrations and concentrations exceeding the supplier’s recommendations. The latter did indeed have a measurable effect on the wine’s phenolic content but also had a “subsequent negative impact on wine sensory character.”

In case I misinterpreted the article, for which I then profusely apologize to all tannin suppliers, here is the link:

http://www.sciencedirect.com/science/article/pii/S0308814611013781

Your thoughts….

Karien O’Kennedy is the Online Communications Manager for Oenobrands. She also knows the odd thing or two about winemaking and fermentation.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Strange wine laws

Karien O'Kennedy — Thu, 21 Jul 2011 23:00:05 +0000

I attended a technical symposium of the South African “Metode Cap Classique” Sparkling wine Association on Wednesday. The first two talks of the day were on CMC (carboxymethyl cellulose) and its use in cold stabilisation. It is derived from a natural product that through a chemical process in a factory achieves its specific functionality and it has been around many industries including the food industry for many years. It is found in all ice-creams as the component keeping it “creamy” instead of becoming icy and is known as food additive E466. In food the legal dose is 10g/kg. In wine the legal dose according to the OIV is 10g/hl. Theoretically one can consume 1 kg of Häagen Dazs in one go (I can) but it is not possible to consume 100L of wine in one go (although many a university student has tried this). The product is not likely to cause any allergic reactions and the lethal CMC dose for a man of 80 kg is 100 000 L of wine. Death by alcohol poisoning will thus come first. HOWEVER, CMC is allowed by the OIV and in most wine producing countries except for the USA. It is considered safe for a three year old to eat it ice-cream but not for an adult to drink it in wine.

Another rather strange rule is that of Natamycin. It is prohibited for use in any wine imported into the European Union. It is an antimycotic (anti-fungus, anti-yeast) which is particularly useful to prevent re-fermentation in the bottle in the case of wines containing a fair amount of residual sugar. There are even speculations that it can be effective against Brett. I am not sure how true this is. The OIV views it as an “antibiotic” which is something that is effective against bacteria and not yeast. It is therefore not permitted for use in wine. The strange thing is that Natamycin is used in most cheese coatings to prevent cheeses from going mouldy. And Europe is a BIG cheese eating nation!

There are various other issues that I could speak my mind on but not without getting fired though. Look out for the pseudonym Poentjie Smit.

Karien O’Kennedy is the editor of New World Winemaker Blog

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

The power of yeast hulls!

Karien O'Kennedy — Wed, 11 May 2011 11:40:41 +0000

In the aftermath of the Southern hemisphere harvest, some poor unfortunates are still struggling with stuck fermentations. In most cases when looking at the facts one can pinpoint why the stuck occurred, but on the odd occasion the reason is not very clear. I had a situation last week where the winemaker, who also happens to be a consultant to other winemakers, had one of these un-explainable stucks. (I think I’ve just created a new word.) He did everything by the book, made all the right choices, grapes were of good quality, etc. Naturally, the first instinct of winemakers when they see the RS remaining the same for more than a week is to consider re-inoculation. Now, this is where the good news comes in. It seems that there is a miracle product, called yeast hulls, which can potentially save you this costly, time consuming, hair pulling, teeth gnashing, and no guarantee that it will work experience.

Yeast companies recommend the use of pure yeast hulls as part of a re-inoculation protocol. The science behind it is that the yeast that got stuck was under stress to survive and as a result produced medium chain fatty acids. These medium chain fatty acids are toxic to the fermenting yeast as well as to the new yeast used for re-inoculation, as well as to MLF bacteria. So one has to “detoxify” the must first before inoculating with new yeast. The recommended contact time with yeast hulls before starting the re-inoculation process is 48 hours.

However, I have seen on more than one occasion that the addition of yeast hulls can lift the inhibition on the stuck yeast, with fermentation starting again and completing without the need to re-inoculate. Over time I have come to identify a possible scenario where such a phenomenon is possible. It seems that if the total yeast count is more than one million cells per ml and the yeast viability is 30% or more, then there is a chance that the fermentation might pull through. Depending on the other existing must conditions it might not be possible for the fermentation to go bone dry, but it might get the wine into a “blendable” (another new word? poor English?) condition.

In the particular case I dealt with last week the wine had an RS of 12 g/l. The wine was stuck at that sugar for over a week. The winemaker added Bio-Springer yeast hulls at 40 g/hl and the residual sugar went down to 3 g/l in less than a week. His yeast cell count and viability were over one million cells per ml and 30% respectively. In other cases that I am aware off where yeast hulls allowed fermentation to complete, the product Extraferm from Oenobrands was used at a dosage of 50 g/hl.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Some advice on natural fermentations

Karien O'Kennedy — Fri, 15 Apr 2011 12:59:45 +0000

It’s the time of year after the southern hemisphere harvest when the unfortunate with stuck fermentations seek advice. There are various causes of stuck fermentations with “natural” fermentations being one of the more common ones. Working for a commercial wine yeast producer I am often viewed as not being supportive of this practice. This is not entirely true. I have tasted some exquisite wines produced via spontaneous fermentations. The times that I am critical of the practice it is merely because I am familiar with the risks involved with it. At the end of each harvest I have to help various winemakers to re-inoculate their stuck “naturally fermented” wines with commercial yeast. So over time I have come up with a few guidelines as to how to somewhat make your natural ferments more “secure.” Unfortunately success can never be guaranteed.

Karien’s advice on more secure natural ferments:

1. Do not attempt natural fermentation when the initial grape sugar is above 24°Brix. This works for some people – they are the exception to the rule. Most naturally occurring wine yeasts are not very alcohol tolerant.

2. Add some complex yeast nutrients containing inorganic nitrogen (DAP) at the start of fermentation as to increase biomass formation. One of the main differences between inoculating with commercial yeast and letting nature takes it course is the size of the yeast population starting the fermentation. You need a critical mass to finish a fermentation.

3. Do not stress the yeast by fermenting at extreme fermentation temperatures, i.e. below 17°C or above 25°C. Your specific mix might not be cold tolerant or very alcohol tolerant – the higher the fermentation temperature, the higher the alcohol toxicity.

4. Add yeast cell walls to adsorb medium chain fatty acids produced by stressing yeasts, thereby making the environment less toxic.

5. If you ferment only some tanks natural and others using commercial yeasts, make sure that the commercial yeasts you use are very strong/alcohol tolerant fermenters. That way you can add that lees (once it has completed fermentation) to the natural tanks in case you develop sluggish fermentations.

This advice is not based on my experience of conducting natural ferments, seeing that I have never done any. It is based on my technical knowledge of what yeasts can and cannot do. Use it, don’t use it. Oh, that reminds me, we once did a yeast trial in our lab (at the yeast factory) and the control – with no added yeast – fermented as fast as the experiments. Yeah….so much for that theory…

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Focus on Chardonnay: part 1

Karien O'Kennedy — Thu, 31 Mar 2011 23:00:42 +0000

On the 28^th of February 2011 I visited Groot Constantia wine estate, South Africa, to investigate how winemaker Boela Gerber plans to make his 2011 Chardonnay – the 2006 version of this wine having earned a place in the top 10 of the 2008 Chardonnay du Monde competition. I arrived just in time to see the grapes arriving in small crates.

Boela adds both 50 ppm SO₂ and Vinozyme skin contact enzyme at the crusher – a significant time apart as not to affect enzyme activity negatively. He does only a very gentle crushing so that a big percentage of whole berries enter the press. He prefers this softer action on the grapes and feels it helps him to minimise phenolic characters. He uses skin contact enzyme to improve yield and flavour. Enzymes according to him have a softer action on grapes than for instance pressing harder, in terms of improving juice yield. The grapes go through a mash cooler that cools it down to approximately 14 °C. Skin contact is as long as it takes to fill the Bucher press, which is about 4 hours.

His final yield is about 680 L / ton after the addition of some press juice. He adds Novoclair settling enzyme and 6 g/hl PVPP in the press sump before pumping it to the settling tank where he settles for 4 days at 3 – 4°C. The juice then has a NTU of approximately 10 and after racking he increases the NTU to 100 by the back addition of fine lees.

20 % of the wine is then fermented natural in old barrels and the remaining 80% is fermented with Lalvin D 47. He uses liquid ammonia (permitted in South Africa) as a source of nitrogen and Anchorferm as a source of complex nutrients during fermentation. The D 47 fermentation starts in tank and is moved to barrel after 1°B is fermented. He uses Francois Ferrer, Dargaud & Jaegel and Mercury barrels, 50 % new and 50% 2^nd and 3^rd fill. Fermentation lasts approximately 7 days. The wine then stays in barrel on the gross lees until November of each year and he battonages by rolling the barrels. Malolactic fermentation happens naturally and is usually 50 – 60% complete. The wine is then taken out of barrel and treated if necessary with Laffort casein and bentonite. In the years where Boela feels either the wine alcohol is too high or the acidity too low, or both, he blends some of his Chardonnay base wine for sparkling wine production from the same vintage into the final blend to assure a better balanced final product. The wine is then sterile filtered and kept in bottle for 6 – 9 months before release.

The wine retails for £11 – 14 in the UK.

PS: I got the title from a four yearly event that Sonoma Cutrer in California used to host/organise. Does anyone know if this is still happening? Google is not very forthcoming on the topic. As a harvest intern at SC in 1994 I had the pleasure of tasting the left over wines from this event every day. Too bad I did not fully appreciate the quality of what I was drinking at the time…

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

A malolactic starter BLEND? Huh?

Karien O'Kennedy — Fri, 18 Feb 2011 09:50:50 +0000

Yes yes, it has arrived. The first commercial bacterial blend has seen the shelves so to speak. It has been commercialised by Anchor Wine Yeast and is a blend of Oenococcus and Lactobacillus. This product is also to be used in co-inoculation with the wine yeast only and not for inoculation after alcoholic fermentation. Anchor takes it even a step further and recommends it with a specific yeast only. Okay so every man and his dog already have MLF cultures. Why should one even consider this product?

The Oenoccoccus and Lactobacillus cultures are South African isolates and the research was done by the Institute for Wine Biotechnology in Stellenbosch, South Africa. They were isolated from high alcohol high pH wines that underwent successful natural MLF. Why? These are often conditions associated with new world red winemaking; therefore making this bacterial blend very suitable for conditions such as these in other parts of the world. But I’m a European / New Zealand winemaker, I don’t have high alcohol, high pH conditions so what would I bother? Well I guess for the same reason that not everyone in the USA where the speed limit is 65 miles per hour drives a Ford Ka. Some people actually do drive faster, better performing cars in slow conditions. It’s about the ride they say – so much more comfortable in a Mercedes CLK. When you ferment a must with a potential alcohol of 14% its comforting to know that the yeast you use is actually resistant to 16%. The same goes for using this bacterial culture blend.

Okay moving along to the next argument as to why it’s a good idea – Lacotobacillus has a higher pH optimum (3.5 – 4) than Oenococcus (3.2 – 3.5). That means in higher pH conditions, faster onset of MLF since the Lactobacillus will kick off first. And no – the Lactobacillus is homofermentative meaning it only converts malic acid to lactic acid and not sugar to acetic acid. By the time alcoholic fermentation is finished MLF is either completed or down to 1 g/l or less of malic acid. MLF is then completed a few days later. Meaning much faster processing and protection of the wine against Brett for instance.

Not convinced yet? The Lactobacillus also smells and taste good. Trials done comparing the Oenococcus on its own and the blend shows increased aromatic complexity in the favour of the blend. The blend also shows increased aromatic complexity when compared to other commercial MLF starter cultures.

Another differential is that the culture is inoculated with the yeast at the same time. No need to wait 24 hours as long as sulphur addition at crushing does not exceed 50 ppm. That should not be a problem for most people. Anchor also recommends the bacterial blend, known as NT 202 Co-Inoculant, with the wine yeast NT 202 seeing the this yeast is very stimulatory for MLF, amongst various other positive attributes. The whole idea is to have completely trouble free MLF’s. We will just have to wait and see – this might just end up being the Holy Grail of MLF. Exciting times!

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Novel Nouvelle

Karien O'Kennedy — Fri, 11 Feb 2011 10:31:40 +0000

Nouvelle is a South African grape variety developed through hybridisation in the seventies sometime, by the late Professor Chris Orffer. The process was not conducted very scientifically and for years it was believed that Crouchen blanc and Semillon were the parents. A paternity test in 2007 however revealed that a certain mister Ugni blanc was indeed the dad. So not exactly very riveting parents but as it happens with genetics in nature sometimes, the off-spring turned out to be quite interesting and useful. It’s only really in the last 10 years or so (thumb suck) that people started to plant Nouvelle and make wine from it. Some belief it is a wine that can stand on its own. Bartho Eksteen from South African winery Hermanuspietersfontein thinks differently.

The 2010 Diner’s Club winemaker of the year feels Nouvelle is only a good blending component and uses it for his Sauvignon dominated white blend, “Die Bartho” (translated into English it is “The Bartho” and it has no relation to death). Bartho picks his Nouvelle at 19°Brix because in this unripe state it produces flavours of grass, parsley and Granny Smith apples. According to him if you pick it riper it has a waxy bubblegum aroma (almost makes you wonder why people bother with this variety). Well, grass (the type used for lawns and not the type you smoke) flavour is quite popular for South African Sauvignon blancs. Most producers seek somewhat of a green pyrazine character to balance the tropical character in their Sauvignons. Pyrazines are also common in New Zealand Savvies, as they call it.

After sorting and crushing Bartho does 48 hours skin contact at very low temperatures and therefore without enzyme seeing that it won’t work anyway. He then presses (660 L/ton yield) and add a Laffort settling enzyme and 4 – 5 g/hl PVPP, seeing that he works very reductively. He thus settles with PVPP and not ferment with it, which is apparently better. He settles for minimum 24 hours during which time he does lees rubbing – a technique where you mix the settled grape lees with the juice again to increase flavour. After racking the must is inoculated with Anchor VIN 7 since Nouvelle has Sauvignon-like characteristics and VIN 7 is a popular Sauvignon yeast in South Africa. After fermentation the wine spends some time on the thin lees and eventually forms a 9% part of the final blend of the “Die Bartho” that is 71% Sauvignon blanc and 20% Semillon. The wine is then matured in new french oak for about 5 months. It retails for £18 in the UK.

So… could Nouvelle with its grassy green character be of interest to the rest of the world’s wine producing areas?

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Yeasts to blame for wines tasting the same

Karien O'Kennedy — Thu, 16 Sep 2010 23:00:27 +0000

This is a favourite claim of the so-called “natural” or “non-interventionist” winemaking movement. One of the reasons why they claim it is better to do natural fermentation instead of using commercial yeasts is that commercial yeasts with their “predictable aromatic profiles” can make, say Sauvignon blancs from Europe, taste like New Zealand Sauvignon blancs. Or worse even, it can make Chenin blanc and Ugni blanc taste like Sauvignon blanc. I have personally been in a tasting with a group of oenologists representing most of the wine countries in the world where the Germans presented a Muller-Thurgau. Everyone, including the French (much to their despair) thought it was a Sauvignon blanc. I have also once given a South African Colombard to a group of French winemakers to taste and they also believed it to be a Sauvignon blanc.

So how does this happen and is it “wrong?” The “naturalists” feel it is wrong. Winery sales figures show it is “right.” Consumers like these aromas. Wines around the world can taste similar because we make wine mostly from one specie – Vitis vinifera. Then we also use yeast which originates from mainly one specie – Saccharomyces cerevisiae. Each grape variety is not equipped with a unique set of flavour active compounds. Only the combination is unique. This combination will differ between grape varieties as well as within the same grape variety in different vineyard blocks and vintages. The main aromatic compounds found in grapes are monoterpenes, C13 – norisoprenoid derivatives, pyrazines, thiols and certain amino acids that can be converted to aromatic higher alcohols and esters. The latter two groups are non-aromatic in grapes and converted by the fermenting yeast to a flavour active form. In some cases pyrazines found in Sauvignon blanc are seen as a positive. When present in reds such as Cabernet and Merlot it is seen as a negative.

Thiols smell like guava, passion fruit, grapefruit, black currant and gooseberry. Sauvignon blanc happens to have the highest thiol precursor concentration in the grapes. Wine yeasts convert these precursors to their flavour active forms and differ in their efficacy to do so. Many other white grape varieties contain these thiols but in lower concentrations. So unless you use yeasts that are very good in expressing these aromas and combine it with certain winemaking practices, these aromas will go unnoticed – as they did for many years. However, winemakers around the world are upping their game – competition is tough. They are using modern technologies and as a result they are tapping into these flavour profiles of their grapes that they did not know exist. As a result they can sell their wine in a bottle and not a box. Is this wrong?

Yes yes stone me, I work for a wine ingredients company and I have a commercial interested in winemakers using yeast. However, my clients who’s Chenins, Colombards, Ugni blancs, Muller-Thurgaus and Verdelhos that have “Sauvignon-like” aromas are certainly not complaining about their sales. If you have very good quality grapes then you have many other flavour active compounds that can “sell” your wine for you and you don’t necessarily have to make such an effort to express the thiols. When you have less than top quality grapes, then optimising what you have is a good idea and if that means optimising thiol expression then so be it.

Just for the record – contrary to popular belief I do support natural / un-inoculated fermentations when conditions are right for it. See my earlier blogpost: Natural vs. inoculated fermentations.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Different yeast rehydration procedures

Karien O'Kennedy — Thu, 29 Jul 2010 23:00:31 +0000

You may have noticed on wine yeast packets and in the literature that there are mainly two different ways to rehydrate active dried wine yeast. The one procedure is a water only procedure and the other a water juice mixture. The existence of two different procedures on different companies’ yeasts can be quite confusing to winemakers if they would like to standardize their cellar practices. Well the good news is you can. Just pick one that suits you best. The reason why one company – say Lallemand – has the water only rehydration and another company – say Anchor Yeast – has a water/juice rehydration is simply legacy. In the seventies when both companies started to produce and sell wine yeast they just happen to choose different methods and then stuck to it. What is very important is that you follow the method you choose exactly and not take short cuts. Yeast rehydration is extremely important for optimal yeast functionality.

So you might ask why two methods exist in the first place. Well, the best way for me to explain this is that water is what was taken out of the yeast when dried after production, so water is all that’s needed to restore the original cell form. However, water has no osmotic strength, which means that if you do not follow the exact protocol and add juice to the rehydration mixture after 30 minutes, then cell constituents (very small, but very important stuff on the inside of the yeast) can leak out from the high (inside the yeast) to the low (water) osmotic pressure. Simple chemistry. The yeast will lose some or all of its functionality, which could result in fermentation problems. So by adding one third juice to your rehydration mix you add some osmotic pressure – making rehydration more idiot proof. You also provide something for the yeast to start fermenting on right away.

In big co-operative wineries the yeasts for several tanks are rehydrated at the same time. So by the time the winemaker returns to the first tank’s mix – 30 minutes could have passed. In this case the water/juice rehydration would be the safer option.

I don’t have any evidence that one method is more effective that the other if both are followed exactly as prescribed. If anyone out there has experience of one being better than the other then please let me know.

This was a rather boring blog to write. Will have to bring in more humor and opinion in my next attempt. Its useful information though…

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

The German Paradox

Karien O'Kennedy — Thu, 01 Jul 2010 23:00:50 +0000

Most people have heard about the French paradox so I thought I’d inform you about the lesser known German paradox. I started travelling to Germany in 2001 as a fermentation consultant to the wine industry and did so on a yearly basis until starting a family put me out of international travel for a while. I tended to visit the same people every time I went and it was fascinating to monitor their progress year after year as they started implementing what I advised. I must admit I was sometimes quite surprised / relieved at the positive effects of my advice myself. Wines that I thought were beyond hope (some Muller-Thurgaus) were all of a sudden mistaken for a new world Sauvignon blanc! Now whether that is a good thing or not is a topic for another day. The mere fact that it went from unpalatable (in my opinion) to very pleasant indeed is what one should focus on.

In 2001 most of the cellars I visited (take note I am not generalising) fermented their whites at temperatures between 18 – 22°C. This is fine for what I call “forgiving” grapes such as Riesling. Riesling has a lot of varietal character not influenced by yeast and fermentation temperature and therefore top quality white wines can be produced at these fermentation temperatures. However, there were certain other candidates that I won’t mention by name out of fear for my safety and that of my family’s, that quite honestly were not so great. I focussed my advice on these wines, what the winemakers themselves viewed as “neutral” varieties. They were all German varieties that I had no experience in tasting so I had no idea if they were truly “neutral” or not. I decided to investigate by advising colder fermentation and more aromatic yeast strains. These winemakers gradually shifted their fermentation temperatures to between 15 – 17°C and changed to different, more aromatic, yeast strains. Some now even ferment at 13 – 15°C.

And this is exactly where the paradox set in… The wines were much more aromatic. All of a sudden the grape varieties were not so neutral after all. The winemakers loved it, the consumers loved it, their buyers loved it, I liked it, BUT they could not sell it. Why not? Because they could not pass the certification of the wines. They were refused their QBA numbers because the wines “were not typically German.” Some kept on submitting the wines for certification until they struck a “younger” panel that would then pass the wines – only just though. The irony of the situation was that these “new style” German wines would then sell out in three months!

The situation has subsequently become better and I believe it becomes easier every year for winemakers to pass their more modern style (but still identifiable as German) wines, especially in the southern wine producing areas. But it certainly is a very strange and frustrating position to be in – to struggle to get certification for your better quality wine. A paradox indeed.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Commercial wine yeast trials

Karien O'Kennedy — Fri, 11 Jun 2010 06:00:17 +0000

Ever wondered what goes into the launch of a new yeast strain? Well the answer is lots of research that costs lots of money, laboratory scale winemaking, small scale winemaking and then finally commercial trials. These commercial trials are usually done with a commercial production of the yeast, i.e. active dried yeast. Commercial trials happen in wineries off course, with winemakers conducting them and not researchers in a controlled environment. So one has to rely on these winemakers to follow your instructions precisely and fill in the required evaluation forms afterwards. OK so this is how it goes…

You phone a few winemakers. You ask if they are interested in a trial. They indicate they are. You lay the ground rules: same juice in two tanks, one tank inoculated with a control yeast of choice and one the experimental yeast. All juice analyses required beforehand and final wine analyses required afterwards. Fermentation graphs must be supplied as well as tasting notes and samples for the researchers or manufacturing company to taste. All willing winemakers agree to this. You give the yeast – for free off course.

After the harvest, this is what you get:

• Group A, the smallest group of winemakers, actually did what you asked
• Group B used the yeast, did everything you asked, except keep a control
• Group C used the yeast, kept no control, filled in no forms but managed at least to present a fermentation chart
• Group D used the yeast, no control, usually do have a fermentation chart, did not taste the wine and already blended it with something else
• Group E used the yeast, but has no record of where
• Group F did not use the yeast – it is still sitting in the store

And last but not the least a new group that materialised the last time I did trials actually used the yeast, kept a control but the cooling broke in the middle of a heat wave and both white wine tanks fermented at about 30°C. I am happy to report that the experimental yeast faired as badly as the control yeast and not worse.

So, commercial trials are, to say the least, quite challenging. The idea is to hand out enough yeast so that a critical mass can be obtained in Group A. And don’t think selecting a different group of winemakers next time round gives you any different statistics. Nope, this is how it is.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Why you should know what the Crabtree effect is…

Karien O'Kennedy — Fri, 21 May 2010 06:00:24 +0000

From Wikipedia, the free encyclopedia:

Named after the English biochemist Herbert Grace Crabtree, the Crabtree effect describes the phenomenon whereby the yeast, Saccharomyces cerevisiae, produces ethanol (alcohol) aerobically in the presence of high external glucose concentrations rather than producing biomass via the tricarboxylic acid cycle, the usual process occurring anaerobically in most yeasts eg. Kluyveromyces spp. Increasing concentrations of glucose accelerates glycolysis (the breakdown of glucose) which results in the production of appreciable amounts of ATP through substrate-level phosphorylation. This reduces the need of oxidative phosphorylation done by the TCA cycle via the electron transport chain and therefore decreases oxygen consumption. The phenomenon is believed to have evolved as a competition mechanism (due to the antiseptic nature of ethanol) around the time when the first fruits on Earth fell from the trees ^[1].

Yeah, congratulations to those of you that grasped all of that. Now for the rest of us in plain English the Crabtree effect is that yeast will always ferment and produce alcohol when the sugar concentration of must is higher than 9 g/l, despite the vast amounts of air/oxygen you might introduce into propagation or fermentation. Uh… okay, so how does knowing this improve my life? Well some winemakers believe that by giving the fermentation (or propagation) “lots of air” it will allow the yeast to respire and not form alcohol. Why don’t you want alcohol formation when you try to build biomass? Because, yeasts grown in the presence of alcohol (as with winery propagation and fermentation due to higher than 9 g/l sugar concentrations) have weaker cell membranes than yeasts grown in the absence of alcohol, as is the case of wine yeast production at yeast factories. Weaker cell membranes equal lower alcohol tolerance equal more stuck fermentations. I think you are starting to get my point why knowing what the Crabtree effect is might improve your quality of life by sparing you some stuck fermentations. It could also help you explaining the yeast bill to your boss. And hey, if you are already convinced that inoculating each tank at the recommended yeast dosage of factory grown yeast is better than propagating, then boasting that you know what the Crabtree effect is to your mates is a great conversation starter at cocktail parties – or maybe not…

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Think pink!

Karien O'Kennedy — Fri, 07 May 2010 06:00:49 +0000

Now I bet very few of you have given this any thought. After all a rosé and a blanc de noir is a “white wine” made from red grapes. So you use your normal settling enzyme. However, this “white wine” contains a certain amount of anthocyanin, which means this anthocyanin should preferably remain a stable colour to ensure the longevity of the wine. In plain English, the wine should preferably remain pink or onion skin, whatever our style is, for a year or longer. It should not turn slightly brownish. In the absence of tannin from the grapes, or ellagic tannin from wood, or oxygen from micro-oxygenation, how does one stabilise this colour? Well for one; keep stuff that can de-stabilise it in the first place away from it.

Anthocyanin, like I said in a previous blog, is stabilised by sugar molecules. When the sugar molecules are removed the colour becomes unstable and can lose it red tinge and become, well, less red. I am not a specialist on polyphenols and bless the souls of the people who are because I find the topic extremely complicated. I have tried and tried to fully comprehend the colour / tannin chemistry in wine and I am not sure if it is lack of intelligence or sheer boredom with the topic that makes it impossible for me to fully grasp it. Anyway having gotten that of my chest, lets stick to the very simple model of anthocyanin and its sugar molecules.

Settling enzymes (white wine enzymes) can contain a side activity, formed by the fungus during production, called glycosidase. This activity is also known as “anthocyanase.” It removes sugar molecules from more complex structures. Although very positive for white wine aroma, it can also potentially remove the sugar molecules from anthocyanin. Now granted, you need a certain concentration to have an effect and some settling enzymes may not contain high enough amounts to cause any damage to your colour. It is nonetheless a good idea to clear this matter with your enzyme supplier to make sure that there will be no effect on your rosé colour. There are quality and composition differences between suppliers and it is a good idea to be aware of these differences. To make absolutely sure that you don’t have this activity in the enzyme you use for settling, use a red wine skin contact enzyme, where the supplier specifies: anthocyanase free, for settling of your rosé or blanc de noir juice. Skin contact enzymes contain the basic ingredients of settling enzymes as well as added side activities needed for skin pectin breakdown. So, it is a very effective settling enzyme as well, more expensive, due to the added activities, but very effective.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

A new record for wine yeasts!

Karien O'Kennedy — Fri, 16 Apr 2010 07:09:16 +0000

I have been involved in “the world of wine yeast” since 1991 and the highest alcohol produced by a yeast during fermentation that I have ever encountered during all these years is 18.2%. I have however read that 18.6% has been observed in Japanese saké wine. During the past southern hemisphere harvest in the South African wine industry we experienced a massive heat wave in the first half of March which lasted a week and was disastrous for wine production. Cellars could not pick the grapes fast enough, and dehydration caused sugars to skyrocket. One poor chap phoned me requesting advice on how to ferment his 32 °Brix Cabernet Sauvignon. Since water addition is illegal in South Africa I suggested Anchor VIN 13 at 40 g/hl, Lallemand Go-Ferm Protect at the recommended dosage, a fermentation temperature of 23°C, the judicious use of complex yeast nutrients and prayer. The winemaker phoned me yesterday to report that the wine’s residual sugar is now indeed at 17 g/l and the alcohol at a staggering 19%! And the sugar is still dropping! This is the highest alcohol produced by wine yeast during fermentation of grape juice that I have personally ever encountered. I would be very curious to know if anyone out there has encountered something similar or even higher?

So, it seems the recipe for ludicrous sugars in the absence of the black snake (yellow snake…depending on the colour of the resident cellar hose) is VIN 13 wine yeast at 40 g/hl or more, Go-Ferm Protect, a low fermentation temperature to minimise alcohol toxicity, everything short of gold and diamonds in terms of yeast nutrition and faith in abundance.

VIN 13 – the first hybrid wine yeast patented and commercialised by Anchor Wine Yeast in 1993. It is a hybrid between S. cerevisiae subspecie cerevisiae and S. cerevisiae subspecie bayanus. It has the fermentation capability (and more it seems) of “bayanus” yeasts and the aromatic capability of “cerevisiae” yeasts.

Go-ferm Protect – a yeast rehydration protectant patented and commercialised by Lallemand. It is an inactivated yeast based product very high in sterols and long chain fatty acids for the purpose of enhancing alcohol tolerance in live yeast cells.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Yeast cell walls versus inactivated yeasts…

Karien O'Kennedy — Fri, 09 Apr 2010 06:50:49 +0000

Yeast cell walls are also known as yeast hulls or yeast ghosts. Many sales reps sell yeast nutrients that they claim contain yeast cell walls when in fact they contain the whole yeast that has been inactivated. So what is the difference in application between cell walls and the whole inactivated yeast?

First a basic lesson in yeast cell morphology: yeast consists of a cell wall, on the inside of that you get the cell membrane and on the inside of that, well… the rest of the yeast. The cell wall consists mainly of glucans and mannoproteins (so-called polysaccharides) and the cell membrane consists of lipids (the fancy scientific name for fat). The lipids are made up of sterols and long chain fatty acids.

Both cell walls used on their own, and inactivated yeast containing the cell wall, membrane and yeast insides, stimulate fermentation. They do this in different ways though. Inactivated yeasts serve as a yeast nutrient in that they can be a source of vitamins and minerals. They can also be a source of sterols and long chain fatty acids. Live yeasts are little cannibals feasting on their dead counterparts when the going gets tough, i.e. the alcohol gets higher. To survive they need to strengthen their cell membranes and to do this they need more sterols and long chain fatty acids. They produce the latter in the presence of oxygen only. During fermentation oxygen is limited so they go for option B and that is to obtain these components from their dead mates. Reminds me of the movie Alive about the soccer team whose plane crash landed in the Andes Mountains. Yummy… Inactivated yeast insides also contain compounds such as amino acids and nucleotides that can “leak” out into the must and serve as a nutritious bite to the live cells.

Yeast cell walls are not a source of nutrients. They detoxify the must by removing medium chain fatty acids from the must, making the environment nicer and easier to ferment in for the live cells. Okay…long chain, medium chain, what’s the story? Live cells need to have an intact cell membrane containing long chain fatty acids to survive increasing alcohol toxicity. As alcohol levels become higher during fermentation, the live yeast starts to produce more fatty acids; however this process requires oxygen, which is limited or completely absent. The manufacturing of the fatty acid gets interrupted and the result is a much shorter chain that cannot be used in the cell membrane. These chains either stay associated with the yeast cell or get secreted into the medium. They physically block sugar uptake. For some reason they bind to yeast cell walls added to the must and the inhibition gets lifted.

The commercial production of yeast cell walls is a much more complicated and expensive process than that of producing inactivated yeast. It is therefore usually a more expensive product. Depending on your specific fermentation conditions, you will use one or the other.

For a more comprehensive and slightly more serious explanation of the different types of yeast nutrients read the article, Wine yeast nutrients 101.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Glycerol: the myth

Karien O'Kennedy — Wed, 31 Mar 2010 08:54:44 +0000

As a fermentation consultant I have spoken to many winemakers form very large co-ops (5 million litre tanks in Spain) to very boutique wineries all around the world. I have visited wineries that are fully automated, state of the art and wineries using 100-year-old wooden vats with no cooling whatsoever. In the latter case one winery’s Sauvignon blanc, Chardonnay and Riesling all tasted the same. Now that is an achievement of note. Imagine the series of adjectives one has to come up with if you taste the wine with the winemaker: interesting, not familiar with this style, etc… During all these talks with winemakers I have come across certain myths surrounding the sales of wine yeasts. Glycerol is my favourite one.

Winemakers believe that some yeasts improve the mouthfeel of a wine because of high glycerol production. It is sold to them based on that trait. I don’t blame them – it makes a nice story. Marketing people conducting wine tastings also LOVE pointing out the “high glycerol content” of wines. Well I am sorry to burst your bubble but unless the wine under discussion is a natural sweet or a noble late harvest, it is not the viscosity of glycerol that is responsible for the mouthfeel. Glycerol is a colourless, aroma less “alcohol” that is viscous in nature. It has a sweet taste. I know this because I dip my baby’s dummy in it and then she sucks it like Maggie Simpson. In concentrations higher than 5.2 g/L in wine it can contribute to the “sweetness” of a wine. Wine yeasts produce between 5 – 14 g/L in dry wines. It is not possible for the human palate to distinguish between glycerol concentrations in this range. A concentration of 25.8 g/L of glycerol is needed to have an effect on the viscosity of a wine. Some Botrytis wines can have this concentration. There is also no relationship between the “tears” in a wine glass and the glycerol content of a wine.

So what does give mouthfeel? Alcohol content, polyphenol content, residual sugar, polysaccharide content, mannoproteins, certain esters etc. Glycerol is thus not responsible for mouthfeel, but does play a small contributing part due its “sweet” taste. The amount of glycerol a yeast can produce during fermentation should therefore not be the deal clincher in choosing a certain strain.

For further reading see what Tim Patterson has to say in his article: Many roads to mouthfeel.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

And now for something completely different – S. blanc part 4

Karien O'Kennedy — Fri, 26 Mar 2010 07:18:54 +0000

This blog entry concludes my feature on what yeasts are used for Sauvignon blanc fermentations. For the “grande finalé” I decided to move abroad and focus on the German Sauvignon blanc of all Sauvignon blancs. Why? Well the winemaker has a very interesting approach to the fermentation and the result is a spectacular wine.

Christoph Hammel, owner of Weingut Hammel in the Phalz, is quite an opinion leader in his area. He is very open to new ideas and experimentation and it is this very experimentation that has lead him to his winning recipe on Sauvignon blanc. Christoph has 53 ha of Sauvignon blanc that he harvests on average in mid October at a sugar level of about 21.5°Brix. He does not chaptilise, which is often the case in Germany, but rather concentrates the juice with a “concentration machine” – to use his words. He does 5 hours skin contact at 5 – 10°C with an addfood enzyme in the presence of SO₂, ascorbic acid, dry ice and un-toasted wood chips. He does not cold settle the juice but rather flotates it with Nitrogen gas. This practice is quite common in Germany.

Christoph uses two yeasts for fermentation that he inoculates at the same time for a co-fermentation. They are Anchor VIN 7 and Laffort X5. The yeasts are re-hydrated in Lallemand Go-Ferm and receive three additions of DAP during fermentation. They are therefore quite well fed. The yeasts are inoculated at 15°C and fermentation temperatures are kept between 15 – 17°C.

Why does he use these specific two yeasts in a co-fermentation? Over the years Christoph tried various yeast blends – with varying levels of success. This blend proves optimum for his Sauvignon blanc. Both yeasts are very effective in expressing the volatile thiols associated with S. blanc varietal character. They have slightly different aromatic profiles and X5 also consumes some of the volatile acidity produced by VIN 7.

Towards the end of the fermentation Christoph also adds B-Glucosidase (monoterpene aroma release) and B-Glucanase (yeast autolysis) enzymes. Fermentation lasts between 11 – 14 days. The wine is kept on the gross lees for 3 – 4 months until bottling.

The concept of co-fermentation originated with the 2005 AWRI research on Sauvignon blanc. There are very specific guidelines one must follow before attempting a co-fermentation. A common combination for S. blanc in Australia is Anchor VIN 7 and Lalvin QA 23. Recent results from AWRI research proved Anchor VIN 13 and Lalvin QA 23 to be a good combination for Chardonnay – unpublished results. Co-fermented wines have different aromatic profiles to wines made from two tanks that were blended after fermentation with the same individual yeasts. This is due to the interaction between the two yeasts during fermentation. Co-fermentation does not always have a more positive outcome and I suggest winemakers to consult with yeast suppliers first before attempting a co-fermentation.

The title of this blog was used without permission from Monty Python.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

What do you ferment your Sauvignon blanc with – part 3?

Karien O'Kennedy — Fri, 19 Mar 2010 08:52:33 +0000

Boschendal wine estate, probably one of the most picturesque wine estates in South Africa (and the world for that matter) produces three different Sauvignon blancs. With all three of these wines they try to achieve (and succeed if you ask my opinion) a more international / European style Sauvignon. They achieve this style by simply altering their fermentation conditions. As simple as that.

The grapes are picked on taste between 20.5 – 22°Brix. The rule is that all Sauvignon blanc grapes must be in the cellar by 12 noon to avoid the heat of the day. Winemaker, Lizelle Gerber, then adds the Laffort skin contact enzyme after which the grapes go through a mash cooler to cool them down to between 9 – 14°C. Skin contact is for 4 hours and not all grapes get deliberate skin contact. Some of the grapes only have “skin contact” the time it takes to fill the press. After pressing the juice settle for 48 hours at 10 – 12°C with an addition of Laffort settling enzyme. The juice is then racked and fine lees incorporated to achieve a final NTU of 130 on average. This is a big difference compared to the previous two producers mentioned in previous blog entries who aim for a final NTU of 50 – 80. The latter is more suitable for new world style wines and the 130 NTU is more in line with the NTU levels obtained in Europe. The reason for the 130 NTU objective is that it suits the yeast – Laffort VL3 better and it is better for mouthfeel development. According to Lizelle, mouthfeel is their main objective before aroma. In the case of typical new world wine production, aroma is usually the first objective and by decreasing NTU and fermentation temperature it helps one to achieve this objective.

After inoculation of the yeast the temperature rises to about 18°C and it is kept on average at about 17°C throughout fermentation. Once again this is a requirement of the yeast and is also different to the practices of the previous two producers who conducted fermentation at much lower temperatures. Boschendal does analyse for YAN before fermentation and do adjustments accordingly during fermentation. They use Lallemand Fermaid K (Laffort probably ran out of stock since they seem to like Laffort) and liquid ammonia – permitted in South Africa. Fermentation lasts between 14 – 18 days. VL3 is used mainly for its mouthfeel and tropical aroma contribution. Boschendal is not interested in emphasizing any pyrazine aromas typically associated with South African and New Zealand Sauvignon blancs.

The wines are kept on the gross lees for as long as the lees are healthy. After the blends are made up the wine is kept on the fine lees until stabilisation before bottling. Bottling is done on demand and usually starts in September of the same year. The single vineyard reserve is kept on the lees longer and bottled much later.

The Boschendal Sauvignon blanc is a typical example of how altering your fermentation conditions can influence your wine style. It does not mean that you will all of a sudden produce a Sancerre because you ferment like Sancerre (I’m not sure how winemakers ferment in Sancerre but I suspect it is not with new world wine yeasts at 13°C). The terroir is still completely different. It does however give you a style of wine that is more appealing to the European palate but with a flair of new world freshness.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

What do you ferment your Sauvignon blanc with – part 2?

Karien O'Kennedy — Fri, 12 Mar 2010 11:47:52 +0000

So I continue my quest to find out what yeasts winemakers use to ferment their Sauvignon blancs with. This is what winemakers Charles Hopkins and Elzette du Preez of De Grendel winery in the Durbanville winegrowing area in South Africa do.

De Grendel is a private winery and 90% of their Sauvignon blanc grapes come from their own vineyards. They start harvesting S. blanc in the first week in February and continue for three to four weeks depending on the location of the vineyard and therefore its ripening times. They pick the grapes on analyses (with the aid of infrared photography of the vineyards) and experience with the specific block. The minimum sugar at harvest is 22°Brix and an acidity of about 9 – 11 g/l. This results in a final wine of about 13 – 14% alcohol with a TA of 6 – 7 g/l. No tartaric acid adjustment is therefore needed. After crushing the grapes go through a mash cooler followed by 12 – 18 hour skin contact at 8 – 10°C (47 – 50°F). They use the DSM skin contact enzyme – Rapidase Expression. Only the grapes that came in at 25°C (77°F)or lower receive skin contact. If the grapes come in at a higher temperature, the mash cooler cannot lower temperature sufficiently enough and there is the danger of extracting phenolics. The long skin contact at low temperatures also promotes natural tartrate precipitation necessary to achieve the final desired TA.

Settling is for 2 – 3 days in horizontal settling tanks. The juice is also circulated during this time over the lees to enhance additional flavour extraction from the lees. After settling the NTU of the juice is about 20. To achieve a fermentation NTU of about 50 – 80 some of the fine lees is racked with the juice. This is monitored very carefully. The tanks are then warmed up to 16 – 18°C (61 – 65°F) before yeast inoculation.

45% of the wine is fermented with Anchor VIN 7. They use this yeast predominantly on the musts that contain more pyrazine aromas. They feel the gooseberry profile it delivers balances the “green” aromas from the pyrazines. Another 45% of the wine is fermented with Anchor Alchemy II yeast blend. This yeast blend also enhances volatile thiols but also produces esters and delivers a very tropical style Sauvignon blanc that is often the preferred style in the rest of the world. The additional 10% is fermented with Anchor VIN 13, Laffort X5 and a co-inoculation of VIN 13 and Lalvin QA 23 for complexity in the final blend. Fermentations are initiated at 17°C (63°F)and after 4°Brix has fermented, brought down to 14°C (58°F). Fermentations last for 10 – 14 days.

After fermentation the wine is kept on the gross lees for 100 days. The two blends are then made up and kept on fine lees until stabilisation before bottling. Bottling is done every two months starting end of June. The remaining wine is kept on the fine lees at 10°C (50°F). Throughout all the processing steps the oxygen levels in the wine are very carefully monitored to ensure a reductive environment.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

What do you ferment your Sauvignon blanc with – part 1?

Karien O'Kennedy — Thu, 04 Mar 2010 10:58:58 +0000

The choice of yeast strain used for S. blanc production has a big influence on the final aroma profile and wine quality. So depending on personal style, regional style, country style, styles your consumers prefer, style your grape quality allows you to produce – different winemakers use different yeasts to aid them in achieving this desired style. I decided to ask a few winemakers to share their fermentation secrets with me.

Erika Obermeyer, female winemaker of the year 2008 in South Africa and head of the South African Sauvignon blanc Interest Group has been very successful over the past few years with her Graham Beck Sauvignon blanc. Erika gets her grapes from seven different vineyards, all classified as coastal, with influence from the Atlantic Ocean. She starts tasting the grapes at 16°Brix and picks on flavour. Each vineyard delivers a specific aroma profile in the final blend. Harvest starts in the last week in January and continues for four weeks depending on the location of the vineyard.

Erika uses the Laffort skin contact enzyme for 5 hours at 8 – 12°C. She has an additional 7 – 13 hours of skin contact but at very low temperatures where the enzyme is obviously not active anymore. After pressing she settles for three days and achieves a juice clarity of 20 NTU this way. This, off course, is way too clear for fermentation and she therefore includes some of the fine lees when racking the juice. Her final juice clarity for fermentation is usually between 50 – 80 NTU, which is a typical NTU for new world wine fermentations.

Now for the juicy part: Erika uses 50% Anchor VIN 7, 40% Laffort VL3 and 10% Anchor Alchemy II for fermentation in different tanks (not co-inoculation). The vineyard the grapes derive from determine the yeast used. She uses Lallemand Fermaid K as a complete yeast nutrient for fermentation.

VIN 7 is used for its production of gooseberry, passion fruit and grapefruit aromas. Fermentation is conducted between 11 – 14°C at a sugar drop of about 1 – 2°Brix per day.
VL3 is used for its production of similar type aromas as well as more of a green fig contribution. It also produces very good mouthfeel and “respects” the pyrazines / green aromas. It is fermented at slightly warmer fermentation temperatures of 13 – 15°C.
Alchemy II has a similar profile to VIN 7 but with more esters – thus a “sweeter” profile. Erika uses Alchemy on the vineyard blocks she feels need a little bit of an “ester” boost.

The wines are kept on their gross lees, which is stirred twice a week. The final blend is kept on the fine lees until stabilisation before bottling. The first release of the wine is in June of the same year. Bottling is done on demand. The rest of the wine remaining in the cellar is kept at about 4 – 7°C.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

On colic, hope and stuck fermentations

Karien O'Kennedy — Fri, 26 Feb 2010 08:22:52 +0000

January to April 2009 was going to be my tenth South African harvest working as a technical consultant for a yeast manufacturer. However, due to the arrival of the stork with a 3.45 kg female parcel, I missed the entire season due to maternity leave. I was initially ecstatic about the “break” but that happiness was short-lived when I realised it was MUCH easier to advise on yeast than to handle a newborn with colic. Fortunately it passed, as all things do, and after four months I found myself back at work very impressed that I missed all the stuck fermentations…or so I thought.

In South Africa harvest is approximately from January until mid-April. It was June. I STILL had people phoning me with: “I have a stuck fermentation. Can you please help me?” Sigh…in my earlier years I was immediately sympathetic and offered advice into the greatest detail. In the last few years, being an opinionated person with a “sometimes problem with tact” the odd winemaker is subjected to the tiniest level of verbal abuse. Sometimes I only think it but sometimes when the situation calls for it, I say it: “Why on earth are you only phoning me now? At some point during the ferment you must have noticed that it is sluggish? Why did you not phone then?” The answer is always “hope.” Hope…all forms of religions and spiritual beliefs advocate that without hope, we are lost. Winemakers are a species with lots of hope it seems. They hope that after the wine got stuck it will miraculously start again and finish resulting in a top quality wine. I suppose there is some reasoning behind this since I have actually seen this happen in my ten years as a consultant, but “hoping” for this to happen is about the equivalent of me hoping that I will win the lottery.

In 2008 I published a series of articles in the Australian and New Zealand Grapegrower and Winemaker on how to avoid stuck fermentations, how to treat sluggish fermentations and how to restart stuck fermentations (view the pdf of the published article). I view the “how to avoid stuck fermentations” as the most important part in this trio of articles. In my humble opinion, 80% of stuck fermentations are preventable. I am going to say it again…80%. Got it? In my experience 60% of the time winemakers simply used the WRONG yeast for the prevailing fermentation conditions. There are many yeasts distributed by various yeast companies very well suited for the production of Cabernet Sauvignon. Very few of them can ferment 26°Brix to dryness. When a winemaker phones me with a stuck fermentation the first question I ask is: “what was the initial grape sugar at harvest?” The second question is: “what yeast did you use?” 60% of the time I have my answer as to what caused the stuck fermentation right there. In some cases the winemakers did not know that the yeast was not alcohol tolerant enough and in some cases they did know but they….you guessed it….HOPED. In my experience the other 40% of stuck ferments are mostly due to propagation, incorrect fermentation temperatures and/or nutrition.

Yeast is a living organism. There is a limit to what it can do. There is no point in me hoping that I will ever win an Olympic gold medal. Winemakers seem to have this type of hope on a regular basis. So how does one resolve this epidemic of false hope? Well if you read this blog you are halfway there. The answer is “information.” Read the information that is supplied to you and make an informed decision when it comes to yeast choice. Don’t just use a yeast because of tradition or fashion. That way you can potentially save yourself time, money and embarrassment. Stuck fermentations are a reality here to stay. They do sometimes occur for what seems like unexplainable reasons. However, most of the time they occur because of known reasons which means you can potentially prevent them. And for heaven’s sake get help when there is still time to prevent the wine from going south completely. Once you have to roll in the VA and alcohol removal machines the cost of that certain volume of wine skyrockets. Not to mention the potential quality of the wine afterwards.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

German dinner

Karien O'Kennedy — Fri, 19 Feb 2010 07:14:48 +0000

Working for a company who exports its products to all the major wine producing countries I have been exposed to a fair deal of international travel, mostly providing technical support to winemakers on all matters fermentation. Having done this for over ten years I have had some, well…, interesting experiences. I recall a certain dinner with German winemakers…

This concept of having a dinner with a group of winemakers started in 2005. About 10 – 13 winemakers get together and we taste their wines. They give a short description of how they produced it and then we discuss the taste. The evening usually starts very formal and ends in a bit of a brawl. In 2005 I did my powerpoint presentation before we tasted any wine. In 2006 we were at a different, much smaller venue and initially I could see no part of a wall that can be used as a backdrop for a powerpoint presentation. We also started tasting and eating immediately. The wines were of exquisite quality and I thought I was off the hook. About two hours into the tasting, with the decibels now being slightly elevated and more than one person speaking at a time, I was told that I will now indeed be doing my presentation. However, not being able to take part in the very German conversations (I don’t understand or speak any German) – I off course concentrated more on the tasting of the wines. All of a sudden there was a big commotion and various plants and murals were removed from the little room where we were sitting, revealing a perfectly big, suitable, white wall instantly decorated with my powerpoint presentation. A projector seemed to have materialised out of nowhere! I was horrified. Since I have had a few glasses of wine by this stage (fortunately German alcohols are not as high as new world wines) I quickly wolfed down about a litre of water and assumed the position. Fortunately presentations in Germany are very effortless because this one winemaker, if he is present, does them for you. I spoke about two sentences and he “translated” for the next 15 minutes; obviously added a significant amount of his own opinion.

After my presentation the evening went downhill very rapidly. Various people were talking at the same time as the winemaker presenting his wine, and the portions poured into the glasses for tasting became bigger and bigger. The speed of wines being hauled out from what seemed to be an endless reservoir increased dramatically. The table looked like the morning after a New Year’s Eve party. At twelve we still tasted wines and there was no indication that the evening was coming to an end – and this was a week night! At approximately 12h30 I took a taxi back to my hotel – leaving behind what seemed like a bachelor’s party at its peak. The next morning I learned that the party ended at 3h30 with beers at the hotel. All the winemakers looked very fragile.

The wines at the dinner were really good quality, fresh, aromatic and surprising very New World in style. They also retained the typical varietal character of these German varieties as well as the slightly minerally character that is synonymous with better quality European wines. In short – they were still very German – but much better quality than what I tasted in previous years. This had a lot to do with winemakers using wine yeasts that promote new world style wines at low fermentation temperatures (for the whites). This dinner was certainly very informative for me in terms of the quality of modern German wines, as well as to the winemakers and our distributors; despite it having been a bit of a twilight zone experience.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

The conversion factor issue

Karien O'Kennedy — Fri, 12 Feb 2010 08:58:20 +0000

Every year after harvest I get verbally abused by some winemaker or winemakers regarding the alcohol concentrations in their wines. Apparently they did everything exactly the same as previous years, used the same yeast and all of a sudden the alcohol is 15% instead of 14%. “What did you do to the yeast,” is usually the question. Doing this job for over ten years I am afraid my tact has become less – not that its ever been great – but my stock standard answer is usually that we decided to put some jet fuel into the growth media, whip out some old ACDC and Kiss records (had to dig for those), play them to the yeasts at full volume during production in order to put some hair on their little chests, thinking “this year we are going to nail the winemakers!”

OK so you get my sarcasm. We don’t “do” anything to the yeasts to increase its ability to convert sugar to alcohol. I will spare you the scientific detail but sugar to alcohol conversion is what it is. You cannot get more molecules of alcohol out of a particular amount of sugar molecules. The mystical figure of 0.55 as conversion factor between degrees Brix and alcohol is exactly that – mystical. I do see it making a guest appearance occasionally when people ferment red wine with a low sugar in an open top fermenter, in a well ventilated room, punching down every two hours. In this case the conversion “appears” to be low because a significant amount of alcohol evaporates. Using the same yeast on a higher sugar must in a rotor tank can result in a conversion rate of 0.62. So what does influence your final alcohol concentration?

Initial grape sugar – the real value, not the one your faulty hydrometer tells you, or your way of sampling. Actual g/l of sugar is also not directly proportionate to degrees Brix. ( see the Robert Paul article in PDF: Concentrate, this is serious)
The amount of whole berries and raisins in the must
Residual sugar at the end of fermentation
Type of fermentation vessel – how much evaporation can take place
Fermentation temperature – more alcohol evaporates from higher temperature juices

In my experience “conversion rates” fall between 0.58 – 0.63. I have seen 0.55, but rarely lately since red grapes are usually harvested at 24°Brix or higher where I come from. White wine fermentations are mostly cool to cold in closed stainless steel tanks allowing for very little evaporation so a conversion rate of 0.63 is more common than 0.55. In fact I have never seen 0.55 in white. I am sure it exists somewhere in countries where people still ferment whites without cooling. Maybe in barrel fermented wines? Let me know.

There can be slight differences between yeast strains in terms of conversion rates depending on how much of the sugar gets converted to by-products such as glycerol, acetic acid and esters, to name a few. However these differences in conversion rates are so minuscule that it is not worth while getting out of bed for, or base your choice of yeast on. Lallemand did a study a few years ago comparing the alcohol conversions of yeast strains under the same conditions. The biggest difference seen between the yeast with the lowest and the one with the highest conversion was 0.51. I suppose a 14.5% wine is better than a 15% wine but labelling laws allow you to print a lower than actual alcohol. Choosing a yeast with a lower conversion might not be very suitable for your wine style and you could end up having a “lower conversion” simply because your wine is semi-sweet.

So until researchers can figure out how to create a non-GMO yeast that naturally turns a percentage of the sugar into white light, you will just have to accept that the higher the sugar – the higher the alcohol, and find other ways to lower the alcohol concentration of wines.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

A case for co-inoculation of malolactic bacteria and wine yeast

Karien O'Kennedy — Fri, 05 Feb 2010 12:22:37 +0000

This morning I was looking at some results from MLF trials done in Italy during the 2009 harvest season and once again the benefit was overwhelmingly on the side of co-inoculation of the bacteria with the fermenting yeast. Over the past few years I have seen various research reports, published articles and powerpoint presentations at conferences on the topic of co-inoculation. Every time the co-inoculated MLF result is better than inoculation after alcoholic fermentation and certainly streets ahead of the spontaneous fermentation results. Why is everybody not doing it? Well the answer to that question in my humble opinion is two-fold:

1. "Fear” because people think that inoculating for MLF before alcoholic fermentation is completed, can have the bacteria grow on sugar instead of malic acid, and as a result form volatile acidity. This is after all what happens in the case of a stuck fermentation. So the fear is justified, but in the case of stuck fermentations it is the natural lactic acid bacteria present on the grapes that cause the havoc. The specific commercial bacteria trialled and tested in the case of co-inoculation do not produce VA. There exists enough evidence for this now.

“2. "Cost” because MLF can happen automatically and it won’t cost you a sent. In these economic times many winemakers go for this option. Some people buy a small amount of commercial cultures and then “mother tank” them. However, to ensure a successful MLF, just like a successful alcoholic fermentation, one needs to inoculate a certain population size. By inoculating less, you could run into a stuck MLF which will cost you more to resolve than what inoculating adequate amounts of the starter culture would have cost you in the first place. There are various other advantages of using specific bacterial starter cultures versus spontaneous – biogenic amines and sensory attributes to name but two.

Inoculating after alcoholic fermentation means you inoculate bacteria into very harsh conditions of high alcohol concentrations and possible non-optimal temperatures, since red wine production is towards the end of summer / autumn and cellar temperatures can drop quite substantially. So, you take your chances with a low inoculum due to “mother tanking” into harsh conditions and you expect it to work perfectly every time? These types of practices make me very nervous. I like things to work. My personal view on this is that if you are into quality winemaking you should not be taking any unnecessary chances. Companies selling bacterial starter cultures can only guarantee a successful outcome to some extend if you follow their instructions and use the bacteria under the conditions they are suitable for.

Personally I would go for co-inoculation. Why? Well you inoculate the bacteria into juice with no or very little alcohol. How nice is that for the bacteria??? The temperature is also very optimal for the bacteria since yeast produces a significant amount of heat during fermentation. The only thing is that one should ideally keep the temperature in the mid 20’s (degrees Celsius) since that is what will be optimal for the yeast / bacterial combination. It is anyway a good idea in the case of the yeast as well, since high fermentation temperatures increase ethanol toxicity. In most of the trial results I have seen, MLF is completed when AF is completed. The time saving and energy saving (no heating up of tanks) can have a profound effect on your bottom line. Generally one has to inoculate the bacteria 24 hours after the yeast inoculation. The reason for this is to give the SO₂ that was added at crushing time to bind since free SO₂can have an inhibitory effect on lactic acid bacteria. With co-inoculation there are no short cuts. You have to use the inoculum size specified by the supplier as well as use only bacteria proven suitable for co-inoculation. Suppliers also specify the yeasts that are best suited for the co-inoculation.

So, it will cost you, but you will get what you pay for: a more predictable and reliable outcome and latest research shows there is a sensory advantage as well!!! Sounds like a good deal to me. The company that I am forced to work for since I did not marry into money employs an American marketing consultant who would have ended off this blog with the following words:

Can you afford NOT to be part of this REVOLUTION???!!!

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Is it okay to use my normal settling enzyme for red wine maceration?

Karien O'Kennedy — Wed, 03 Feb 2010 07:22:53 +0000

This is a question I got from a winemaker a few days ago. Some people selling enzymes will say yes, that any pectinase preparation you use will be better than using nothing at all. I suppose that can be the case. However, here are a few facts to consider when choosing an enzyme for red colour/tannin extraction.

Colour and tannin are mostly situated in red grape skins. The pectin structure of grape skins is much more complicated than the simple structure of the pulp. When your aim is settling only, you work with the pulp of the grape. A simple pectin structure only requires the basic pectinase activities of pectin lyase, pectin methyl esterase and polygalacturonase. That is why settling enzymes are the most cost effective to produce and usually the cheapest of an enzyme supplier’s range of enzymes.

If skin contact is your aim, you need additional enzymatic activities to break down the highly branched, complex pectin structure of skins. So in addition to the basic pectinases, skin contact enzymes contain various “side” activities. The production organism – Aspergillus niger – produces much less of these side activities than the basic pectinases. That is why production of skin contact enzymes is more expensive and you, the end user, has to fork out more. It is a specialised enzyme for a specialised application. So basically skin contact enzymes contain all the components of a settling enzyme, usually in higher concentrations, as well as specific side activities that will work on the more complex pectin structure of skins.

So, common sense will tell you that an enzyme specifically recommended for skin contact will therefore be way more efficient in extracting colour and tannin than a normal settling enzyme. But wait…there is more….if you order now, you get this beautiful set of steak knives absolutely free!!! OK I digress; seriously there is one more factor to keep in mind.

Aspergillus niger also produces a group of enzymes called glycosidases during the commercial production of pectinases. It actually falls under the group of side activities formed. It does it automatically, with some strains producing more than other. Glycosidases remove sugar molecules from more complex structures. In grapes, certain potentially flavour active compounds are bound to sugar molecules. In this bound form they are not flavour active. When the sugars are removed, you can smell and taste these compounds. An example is monoterpenes found in most white grape varieties, especially Riesling and Muscats. They are also found in red grapes. However, red wine colour, anthocyanin, is stabilised by sugar molecules. So by removing the sugars from anthocyanins, glycosidases can destabilise them, making your red wine colour, unstable. So what is a positive in white is a negative in red. Red wine enzymes should preferably not contain any glycosidases, or, as they are more commonly known in this case – anthocyanases.

My advice to you would thus be: make sure that the enzyme preparation you plan to use for red must maceration contain negligible levels of anthocyanase. If your supplier cannot give you that assurance, then switch to a supplier that can give you that assurance. No point in being penny wise and pound foolish. There are ways enzyme companies can manipulate production of red skin contact enzymes to minimise this activity. They generally, however, do not try to limit this activity in white enzymes, such as settling enzymes, since it is a positive for white wine aroma.

Having given you the scientific facts, my personal answer to the above question would be: no, it is not OK to use your settling enzyme for red skin contact. However, if your supplier can guarantee you that the anthocyanase activity in their settling enzyme is negligible, then I suppose some pectinase activity is better than none.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

What do YOU base your choice of yeast on?

Karien O'Kennedy — Fri, 22 Jan 2010 14:08:55 +0000

There are over 200 (or even more) yeast strains commercially available to winemakers. How do you choose which ones to use? It is interesting to note the differences in psychology of yeast choice between different wine producing areas in the world. Having travelled to most of the important wine areas I have come across various different “reasons” for particular choices of yeast. I found tradition to play a big role. For instance, in my experience Bordeaux is Laffort country. The French like everything to be French – vive la France! It is very difficult for non-French companies such as Erbslöh, Mauri and Anchor Yeast to make inroads into this market. Lallemand, although French Canadian, comes a close second, seeing that their technical head offices are in Toulouse. And they are French off course.

In Germany Erbslöh is big due to a long standing association with Geisenheim, the very famous university for studying winemaking. However, French yeasts seem to be more acceptable in Germany than German yeasts in France, with the exception of Alsace. South African (www.anchorwineyeast.com) yeasts are also quite popular. Probably because the South African yeasts are true New World wine yeasts promoting New World wine styles. German winemakers, especially in the south, are more open to “internationalise” their wine styles. The taste of the wines anyway, the labels are still a problem.

Australia is quite an interesting example. In my experience the main players are Lallemand and Mauri. Mauri was traditionally Australian but is now owned by a Brittish company. However the legacy remains and they have a long research association with the Australian Wine Research Institute (AWRI). Lallemand is probably the premium yeast of choice and I find it astonishing that most tank fermented white wines in Australia are made with one particular yeast. Trying to convince an Aussie winemaker to try something else on white is like pulling teeth, especially if you are trying to convince them to use South African yeasts. I suspect rugby and cricket has something to do with it.

I find the New Zealand market very open to suggestions. They seem to make technology their reason for their yeast choices. They follow science, are great in trialling new products and very open to new suggestions and change. No specific yeast company dominates this market.

The American market loves the French yeasts. However, they are open to change lately and do pay attention to new research findings on yeast. Anchor yeasts have made some inroads into this market lately since American winemakers are looking into making more New World style wines, especially the whites. They are moving away from heavily oaked, buttery wine styles to more easy drinking fruity wine styles that countries such as South Africa, Chile, Australia and New Zealand produce.

In Chile DSM (the former Gist-Brocades, www.dsm-oenology.com) used to be the main player in the yeast business due to the fact that they had production facilities in Chile. They remain one of the main players in the market today. Subsequently Lallemand and Laffort have become big players and Anchor Yeast is gaining popularity fast. I find the wineries that I have visited quite modern and scientific in their approaches and they base their yeast choices on the best possible yeast for the application. Tradition does not play such a big role.

The other reasons why winemakers use the yeasts they do:

Price – “I use only basic yeasts (pdm) because they are the cheapest and I produce bulk wine”

“Everyone else is using it”

“I don’t believe choice of yeast has any influence” – these winemakers should preferably not be allowed to make quality wine.

What your choice should be based on is the following (and it is not rocket science):

1. The yeast needs to be able to complete fermentation under your specific conditions (each tank in your cellar being unique) without any problems and off odours.

2. The yeast must be the most suitable one for your specific style of wine. Sancerre produces a different style Sauvignon blanc to New Zealand.

There are many yeasts in the world good for the production of Cabernet Sauvignon. Very few can ferment 26°Brix to dryness. So if you make wine in the Napa valley, you might need to choose a different yeast to what is being used in Bordeaux where grapes are picked at 24°Brix and below. The good news is that you probably do not have to give up tradition as choice of yeast supplier, you might just need to change to a more suitable yeast within your supplier’s range for your specific conditions. In some cases however, you will have to change supplier to find a more suitable yeast. The proverbial leap of faith. If you are not open to change I suggest reading the book: “Who moved my cheese” by Spencer Johnson.

Bon courage!

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy

Can yeasts change from one year to the next?

Karien O'Kennedy — Fri, 15 Jan 2010 12:57:41 +0000

Harvest has started in the southern hemisphere which for me means phone calls and queries from winemakers. These questions, I am starting to realise, provide ample blogging material. Here goes one I got yesterday:

Q: I used "Yeast X" last year and it worked beautifully on my Sauvignon blanc. I therefore used it again in 2009 and got nothing. The wines were very bland. Did you change the yeast?

A: Yeast companies don’t generally “change” their yeasts – not the well-known established brands anyway. I can’t speak for distributor brands. The OIV requires that yeast strains are identified on the packaging especially if the original strain name is not the same as the brand name. There can, however, be quality differences in the manufacturing of a specific strain. Reputable yeast producers have strict manufacturing standards to ensure product performance repeatability.

In some cases when one company steals another company’s strain and manufactures and sells it under a different name – the copied strain can have decreased fermentation performance. This is simply because the company that originally commercialised the strain has perfected its production process. The company who stole the yeast does not have the in depth knowledge of the specific strain’s metabolism since they did not do the research to develop the strain. I have seen published scientific results from a reputable institute on fermentation performance of two strains that I know to be the same strain. The original outperforming the copy. Sadly, very good copies also exist. Why do these copies exist? Well its simple – they are cheaper than the original since the copying company did not have to pay for four to five years of research and neither do they pay royalties to the research institute who owns the strain.

So if the yeast strain does not change? What does? How can you have a good wine one year and a bland one the next – from the same vineyard? Well, the answer is quite simple. No two years are the same in terms of weather patterns and if you add changes in viticulture to that, you increase the effect on grape composition even more.

Yeasts cannot perform miracles. They can only work with the raw material you supply. Grapes contain aroma and flavour precursors. If, in some years, these precursors do not exist in adequate concentrations as a direct result of a change in climate, yeasts cannot transform them to flavour active compounds. Simple as that. So it’s not the yeast supplier that is to blame, more likely the viticulturist, who should have adapted his/her viticultural practices to accommodate the change in climate form the previous year. Unfortunately the effect of some climatic conditions cannot be corrected through a change in viticultural practices and one has to resort to changes in winemaking practices to try and save the day. This can include a change in the choice of yeast, lower fermentation temperature in the case of white wines and higher juice clarity. The best thing to do if you are uncertain as how to handle lower quality fruit than what you normally have is to contact a fermentation / winemaking consultant (phone a friend) and ask for advice. There is no point in doing what you normally do and hoping for the best. This “hoping for the best” could have serious financial implications.

This NewWorldWinemakerBlog.com post was written by Karien O'Kennedy