New World Winemaker Blog

“I have walked across the surface of the Sun. I have witnessed events so tiny and so fast they can hardly be said to have occurred at all. But you, Adrian, you’re just a man. The world’s smartest man poses no more threat to me than does its smartest termite.” – Doctor Manhattan

The above quote by Doctor Manhattan from the 2009 movie, Watchmen, made a very big impact on me. Not only did Doctor Manhattan have extraordinary physical capabilities, but also boundless intelligence and wit. Most scintillating however, was his ability to observe and control miniscule atomic particles and impossibly fast to imagine metaphysical events. Doctor Manhattan didn’t really strike me as a lush, but I’m sure that he would have been fascinated with the chemically complex and ever changing matrix that is maturing wine.

As a former minor winemaker at quite a few cellars, my favorite place has always been the barrel maturation cellar. Barrel ageing is ostensibly one of a wine’s more important stages of evolution before bottling. But how exactly does wine change during barrel ageing and what effect does it have on the countless chemical reactions taking place in wine every second? The main effect of oak barrel ageing is twofold. Wood character is introduced (the rate and intensity is mostly dependent on fill status of the barrel) and oxygen is very slowly introduced to the wine. Generally speaking, this results in softening of the harsh tannins and flavors present at the end of fermentation. Oak is a fascinating substance, which has a profound and remarkable effect on the flavor chemistry of wine. Key oak derived compounds are tannin, lignin, cellulose and hemicellulose.

Tannin plays a vital role in barrel ageing. Although most tannin in wine comes from the grapes, some of it is also liberated by the barrel during ageing. So what exactly is the deal with tannin? An experienced winemaker will instinctively know how to optimally merge and balance the tannins extracted during the youthful stages (fermentation, skin contact and pressing) and the mature stages (barrel ageing and blending). For instance, more tannic grape varieties such as Tannat, Cabernet Sauvignon, Nebbiolo and Shiraz cannot be approached the same as the less tannic Pinot noir. Once again, winemaker experience is paramount.

OK, now hold on to your chemistry hat, here comes the hard (but interesting) bit! Phenolic compounds (consisting of natural phenols and polyphenols) in wine are largely responsible for imparting taste, colour and mouthfeel to wine. They include phenolic acid, stilbenes, flavonols, dihydroflavonols, anthocyanins, flavanol monomers (catechins) and flavanol polymers (proanthocyanidins). Natural phenols can be separated into flavonoids and non-flavonoids. The latter group includes stilbenoids such as resveratrol and phenolic acids such as benzoiz, caffeic and cinnamic acids. The former group includes anthocyanins and wait for it… tannins!

What would a good red wine be without vanilla flavors, sweet and toasty aromas and notes of tea and tobacco? Specific compounds create these nuances in finished wine, for example: volatile phenols containing vanillin; carbohydrate degradation products containing furfural, a component yielding a sweet and toasty aroma; “oak” lactones imparting a woody aroma; terpenes providing “tea” and “tobacco” notes, and hydrolysable tannins, which are important to the relative astringency of the wine. Take note, every time you’re quaffing a wine (hopefully a worthy vintage), you’re consuming everything you’ve just read above. If this doesn’t sit quite right with you, then I guess nothing much will.

They say you should have respect for your elders. So, tread lightly the next time you pass through a barrel maturation cellar. You might even see Doctor Manhattan skulking around in the dark, silent corners…

Bernard Mocke is a technical consultant for Oenobrands.

VERB:   to put in the place of another; switch seemingly equivalent items (e.g. “substitute regular barrels with flextank”)

DEFINITION 1: to use something or someone instead of another thing or person

(You can substitute oak barrels for flextank in the production of icon and ultra premium segment wine.)

DEFINITION 2: to perform the same job as another thing or to take its place

(Polymer flextank will substitute for less efficient oak barrels.)

(Definition of substitute verb from the Cambridge Advanced Learner’s Dictionary)

I am sure I have most reader’s attention now. Something in me shivered when I read on flextank Australia’s website, the bullish mantra “Barrels – a good idea 500 years ago…a great idea today –fFlextank Barrel replacement” for the first time. I am a traditionalist. I use barrels to mature wine in! How could I EVER be a representative of a product in which I do not whole heartedly believe in? This is a story of a paradigm shift…

The title of my M.Sc. thesis many moons ago was “The influence of oak and oak derived products on the evolution of red wine”, and this was somewhat part of the birth of the Coffee Pinotage 11 years ago. I realised throughout the course of the project that you can achieve great results by using staves as opposed to barrels, if certain aspects of the processing part is tweaked.

I met the flextank team last year, and became part of an incredible product, which raised my eyebrows at first…until I experienced the proof in the pudding. Before I get there, let me explain what flextank is. Wine is matured in barrels for two reasons mainly: One is the contribution of oak to the mouthfeel of the wine, and the second is the contribution to the wine’s aromatic complexity. The evolution of both is  influenced by oxygenation as a result of the porosity of the oak – which of course is not that consistent…hence barrel differences in many cases. flextank is a polyethylene polymer, which allows for the effect of oxygenation, making this process very homogenous and controlled. No barrel differences!

The lifespan of the 1000 L cube is more than 25 years, requires less manpower to move around, rack and transport, has no evaporative losses, is significantly more hygienic than older barrels, does not lose its ability to oxygenate at a controlled level like old barrels (new barrels 30-40 mg O₂/L/year, old barrels <10 mg O₂/L/year), is more space efficient (can be stacked 4 high) and can be reductively “battonaged” simply by using a forklift (yes, the seal is that effective). It can be used for both red and white wines, and can be used for alcoholic fermentation, malolactic fermentation and maturation. I almost forgot – it is also slightly more cost effective, although this should not even be part of the consideration for using flextank…

The proof of the pudding? I tasted over 40 wines in Australia earlier this year. The wines matured in flextank tasted (blind) fresher, fruitier, livelier and better integrated than the older barrels, and I did not pick up any difference between wines matured in flextank vs. NEW barrels.

Plus the friendlier carbon footprint…what more do you need?

Bertus Fourie is a winemaker, turned Enology lecturer and creator of the Barista coffee Pinotage.