Wild yeast fermentation – true or false?

(WineCompanion) - The news release of the Australian Wine Research Institute of November 28 came in while I was in Myanmar, (albeit only accidentally stumbling across Myanmar’s Red Mountain wines, which seem to have been made by someone with plenty of winemaking know-how). 

The AWRI release is truly fascinating, and many involved in the full spectrum of the wine fraternity in Australia will look forward to the first reports emanating from the studies.  I am not alone in believing that so-called wild yeast fermentations may well have been initiated by yeasts emanating from the vineyard, but typically running out of steam once the alcohol level in the wine reached 3% or thereabouts.  It has been widely assumed that winery residents from prior fermentations or other hosts have been of the saccharomyces cerevisiae family, these being the bedrock of commercially produced yeasts.  However, there have been isolated reports of some unidentified, but viable, yeasts remaining at the end of fermentation, but little more than that.

Winemakers will gain new insight into the microorganisms in their ferments thanks to a new partnership between the Australian Wine Research Institute (AWRI) and the University of New South Wales’ Ramaciotti Centre for Genomics.

Grapes are transformed into wine by an entire ecosystem of yeasts and bacteria, whose composition has a huge impact on the quality of the final product. In many cases these microbes are ‘wild’, coming from the local environment and appearing naturally in the fermentation once the grapes are crushed. However, like any wild creature, their appearance and behaviour can be erratic, and their overall role in defining regional character of wine largely remains a mystery.

To delve into this mystery, a technique known as metagenomics will be applied to analyse wild wine ferments from around Australia, allowing the identity of all the yeast and bacteria present in the fermentations to be mapped using their unique genomic signatures.