Winemaking is a fascinating creative process whose interpretation includes both craft and a science. While the majority of winemakers aim for a balance between both philosophies, divided opinions on what extent wine production should be manipulated and controlled to produce the best wines spark highly controversial discussions. Current conventional understanding of microorganisms used in the process of alcoholic and malolactic fermentation is to classify them as processing aids, regardless whether they are indigenous or selected. Nevertheless, the natural wine movement insists that anything added (e.g. lab-bred yeasts, enzymes or bacteria) to wine should be listed as an additive and therefore be declared on the label so that consumers can make an informed choice. However, what happens when wild yeasts are selected from a specific ecosystem for their individuality and then are reproduced for the following vintages in order to achieve reliability? And would consumers really benefit from this transparency reflected on labels or would it just create further confusion?
Both winemaking techniques – alcoholic and malolactic ferment – can be either controlled by inoculation with carefully selected yeast strains (specifically Saccharomyces cerevisiae) or lactic acid bacteria (specifically Oenoccocus oeni, Lactobacillus, Leuconostoc & Pediococcus) respectively. Alternatively they can be carried out spontaneously thanks to indigenous cultures. Regardless the method, the microorganisms used as catalysts are technically defined as processing aids (not additives or ingredients) as they are substances that are transient and do not remain to a significant extent in the finished contemporary wines. Both yeasts and bacteria are killed by increased alcohol level or thanks to sulphur dioxide at the end of fermentation and are then removed from the finished wine by racking and/or filtration.
The non-interventionist or natural wine argument, on the other hand, uncompromisingly asserts that foreign/selected yeasts and bacteria are additives and therefore not accepted in their unofficial codes of practice. Their argument is supported by the fact that it has been proven that different populations of wild yeast species are specific to a region/vineyard. This means that the regionally different populations of wild yeasts and other fungi produce regional flavours and wine characteristics and therefore are closely tied to expression of a specific terroir. Global research has shown that both vineyards (grape skins, vine leaves, stems, soil) and wineries (interior, barrels etc.) are heaving with microbial life. Dr Mat Goddard, senior lecturer and yeast researcher of The University of Auckland, has proven that Saccharomyces cerevisiae is unique to a place/region. He found that yeasts in West Auckland, Kumeu River share less than 0.4% of their ancestry with other international strains. Similarly, David Mills, Professor in the Departments of Food Science & Technology at the University of California at Davis, found specific microbes within California’s wine growing regions (such as Acetobacter in Central Coast, Methylobacterium in Sonoma and Lactococcus in Napa Valley) after testing over 270 ferments.
Based on these findings, only indigenous populations of yeasts and bacteria result in wine that faithfully reflects the sense of place. The clearest solution therefore would be to consider indigenous cultures as processing aids, and commercial cultures from a packet as additives as they alter the wine style despite not remaining in the finished wine. However, the issue is how to make this sufficiently clear on labels in order to provide consumers with accurate information and enable them to identify the origin and quality level of the wine. Also, consideration is required on how to avoid misleading or confusing consumers by listing extra ingredients whilst not portraying the wine yeast additions as detrimental or unfavorable in the consumer’s mind. It is thanks to the wine yeast companies (such as Lallemand, Oenobrands) and their ongoing investment that the risk of stuck ferments, the formation of undesired characteristics or a high level of bacterial biogenic amines have been eliminated, and that better more consistent wines can be created.
In addition to this labeling issue, the discussion gets even more complicated as wild yeasts can and are commercially developed in order to produce the authentic effect of spontaneous ferment yet in a control way. There are some producers worldwide that select their own indigenous yeasts and reproduce the same species for the following vintage ensuring a reliable start and finish of the ferment and retaining the individuality of the place. Quinta de Azevedo in Minho, Portugal developed a yeast culture from their vineyards called QA23 which has been successful for starting and controlling fermentation. Vasse Felix in Margaret River, Australia has developed their own yeast culture for the combination of individuality and reliability and in order to create consistent aromas.
In conclusion, there is no single answer as to whether yeasts and bacteria that have been commercially selected should be considered as additives or whether they should remain to be officially classified as processing aids. There are two controversial camps of producers who present valid arguments. In addition, a new method of capturing the benefits of authenticity and control is starting to be explored thanks to new developments in viticulture and a better understanding of the microorganisms responsible for alcoholic and malolactic ferment. However, the combination of using wild microorganisms and reproducing them muddies the waters between what is a natural element and what is an additive/ingredient. Consumers may not be aware of the implications of these production methods but if labelling reflects the difference there it is likely that despite being more specific, labels will become more confusing and possibly misleading about the quality of wine. After all, regardless of the method used, both are instrumental in meeting global demand for high quality wines.