wild or natural ferments/strong>
It is not uncommon for wine books and wine promotions to refer to 'wild' or 'natural' ferments when describing the production of Chardonnay and red wines. Such descriptions accord with public sentiment, which tends to prefer the natural to the artificial or technological, and reinforce the bucolic and romantic vision of winemaking. But what does this mean? 'Wild ferment' refers to the practice of not adding cultured or commercial yeasts to red or white ferments, thus (in theory) allowing the natural yeasts brought in on the grapes to initiate the ferment, giving a more ‘natural' result. Such descriptions immediately raise scientific and philosophical questions
Most winemakers would probably agree that the first ferment of the vintage can be decidedly different, and that it probably starts as a genuine natural ferment since it takes a much longer time to begin, often smells quite strongly of ester (not necessarily desirably so) and shows the characteristics of a Kloekera yeast ferment which microbiologists claim is probably naturally derived. Such a ferment is normally quickly overtaken by the more robust Sacchromyces yeast, since it cannot effectively compete for nutrients and it dies in the presence of quite low levels of alcohol. Sacchromyces yeasts are the conventional winemaking yeasts: robust and capable of fermenting grape juices dry, and contributing flavours appropriate for the production of wine. All but the earliest ferments will be dominated by these from the start.
The oenological crunch comes with the fact that vineyard investigations by microbiologists have not been able to find wine-type Sacchromyces in any vineyards around the world We must presume that if they exist at all, they must do so in very, very small numbers. It appears likely that the Sacchromyces which provide the ‘natural' ferments come from inside the wineries or off equipment on which they have survived for some years, and that in New Zealand it is more than probable the ancestors of these yeast cells came out of a bag or a tin. Maybe we should substitute 'natural' with ‘indigenous winery ferments'? Let us not despair. The pristine naturalness may be a lost cause, but our yeast ferment is at least not a ‘pure 'single strain (as it might have been from a packet), since winemakers will have used different strains with the different wines in the winery, and a collection of various types of yeast certainly does have the potential of producing interesting results. Indeed, the latest innovation in the production of cultured yeasts is the marketing of mixtures of strains carefully selected to provide exactly this effect.
Is there a problem with the earlier 'pure' single strains of yeast? No, of course not. In principle they are the same or similar to components of the commercial mixtures or the 'natural' strains we have discussed. The only possible criticism is that because they are singular they may lack some complexity by comparison. And what of the overall role of the choice of yeast for making fine wine? In my view the essential component of great wine has to be fruit quality before all else. The winemaker has a number of choices to make, but if we set aside the quality control decisions, choices such as type of yeast have a much stronger influence on how the wine is perceived in the first year or so than on how it appears when it has reached its prime, because the development of a wine is so strongly dictated by the variety of grape and the quality of the fruit at the the time of bottling.