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.
During my recent harvest stint in Germany, my host, Christoph Hammel uttered many memorable (and some that I am not allowed to mention here) pearls of wisdom. He told me about a meeting where some of the biggest names in German winemaking and professors associated with the wine industry were present. A very well know professor publically stated that his belief system does not have any room for the theory that yeasts impart any aroma to a wine fermentation. At this, Christoph got up and glibly replied: “My dear sir, it is not a question of belief. It is a question of knowledge.” The subsequent pandemonium that ensued was apparently quite noteworthy (hence the photo above).
Christoph is a big believer in using technology, specifically technology that can be used to make wine, and wine processing, better. Even more specifically, he is a big believer in additions. He always said to me that he makes wine that people want to drink and if this can be achieved with the addition of enzymes and other winemaking tools, so be it. Every addition that he does is done for a reason. One thing can be said with certainty and that is that Christoph believes in the “interventionist” approach to winemaking. A lot of winemakers like to claim that their wine is made “naturally” and with the least possible human intervention, but Christoph is at the complete opposite of the spectrum. He has some pretty far out and amazing ideas and some might even call him a renegade or a cowboy after hearing about his yeast mixing and addition regimes!
As far as the additions are concerned, Optiwhite (Lallemand) is one of his stalwarts. This is usually added at the beginning of fermentation. β-glucanase and β-glycosidase enzymes are added at the end of fermentation (at about 0°Brix). Depending on the structure and quality of a specific wine, ascorbic acid is also added right at the end of fermentation. DAP is added at three stages and is sometimes even added in divided dosages during the day, depending on the fermentation bouquet. In addition to DAP addition, thiamine is added to all musts. This is done simultaneously with sugar addition. It is well known that fungal infection on grapes depletes thiamine and it is therefore an excellent prophylactic measurement against stuck, sluggish or smelly ferments. For each addition, a cost to benefit decision is made. For instance, light and easy drinking wines will not get all the bells and whistles. The more expensive wines will get a full range of stuff added.
If Christoph was not such an excellent winemaker, I would have said that he missed his true calling in life: A chef! A chef who is forever mixing, adding and tasting, mixing, adding and tasting…
The European Union might want to ban wine in which hen’s eggs or dairy products have been used, as some people can be allergic to these products. Alternatively the new law might just insist on labelling the wine as containing these products. The prevalence of allergic reactions to milk and egg products has been reported to be 1% of the adult population. Clinical trials have been inconclusive, and although wine has no history of causing allergic reactions as a result of the protein fining agents used, the possibility still exists.
Eggnog is a traditional drink at Christmas in the USA, and was developed in Europe by combining eggs and alcoholic drinks to let the eggs last longer. The drink was apparently first called “egg-and-grog”, and it has been known to cause allergic reactions in individuals. This seems to be the basis of the fear of egg allergens in wine.
Although HACCP is widely practised in the winemaking industry, almost all of the CCPs (critical control points) have a quality influence. There is only one commonly established real CCP and that is at bottling, to prevent glass from entering the bottles which could be harmful to people who swallow it. Another critical control point was once established to be grapes infected by Ochratoxin A, which is formed by moulds on grapes, but that is not very common.
The allergen law requires wine that contain these products to be labelled, but if there are no residues, who will be the wiser? The naughty compounds in eggs are the proteins that can easily be removed, although milk might leave residues of lactose. The ELISA tests that are used to test for residues cannot test down to zero, but the limits of detection have been found to be good enough to establish risk. There are also people with the view that if a product has been used, if it is still present or not, it must be stated.
There have been companies peddling plant alternative proteins that can apparently perform the same tasks as egg and milk proteins, but I have not had the pleasure to test these.
The new allergen labelling laws were originally intended to be implemented in 2005, but the deadline has now been extended to 30 June 2012, to assess possible exemption of these products. Let’s see what happens.
The history of the wine trade is filled with stories of wine that has been manipulated, adulterated (substances not related to grapes being added) and even counterfeited. We have grown used to spinning cones and reverse osmosis, electron dialyses and ion exchange, thermoflush and decanting, cmc’s and various cocktails. Do not get me wrong, I also love the science of wine, and I firmly believe you have to have cash to sustain “real winemaking”…profit can only be achieved if costs are reduced and turn over maximised…and if you can use technology to achieve that, why not?
But to add strong acids? To add glycerol? To add flavourants? And call it wine? I can certainly not agree with this, even if legislation does in some cases. Take Mega Purple for example, a food additive that is used to enhance sensory attributes such as color, taste and mouth feel. It is produced by concentrating the teinturier grape Rubired, a cross between Alicante Ganzin and Tinta Cão and has a sugar concentration of 68%. Teinturier grapes is different to vinifera in that it has dark, red juice. Mega Purple is basically a concentrate of sugar and colour, and is added to a wine with insufficient colour to fix the colour to a darker hue, making it more attractive for the buyer. It is common knowledge that a darker, deeper red colour is associated with higher quality, irrespective of the cultivar. It is therefore possible to “change a white wine or Rose into a red wine” by the addition of this magic potion. The downside, however, is that it has its own, unique smell and if you use as little as <1% it may change the aroma/bouquet of the adulterated wine to something less intriguing. Perhaps it is in order to use mega purple in cheaper wines, but as soon as the potion is added to wine, it “homogenise” the complexity of the bouquet significantly. Perhaps the consumer who buys wine in this category does not really care about terroir, nor bouquet, only about price.
If you surf the net to establish how people feel about Mega Purple, you’ll find loads of oenophiliacs giving the wine drinking community a piece of their mind, but no comments from “semi-oenophiliacs”. The question is though: Does someone who buys wine for less than $10 or €3-00 really care? I honestly think they don’t!
From a personal perspective though…I suppose it just does not feel right.
I remember someone saying long ago “it is the complexities of nature that gives personality to our wines…”