Defining and exploiting the indigenous microflora of grapes

Background

Microorganisms isolated from 2018 winery samples. Photo: K. Sumby

Uninoculated fermentations that use resident grape and wine microflora have seen a dramatic resurgence in winemaking. Previously, fear of spoilage saw resident microbes suppressed by addition of a selected strain and SO2, but now these resident non-Saccharomyces yeasts are being encouraged. The spoilage risk remains, but the reward is an increased flavour complexity arising from extensive competition for and sharing of metabolites and cell-cell interactions. Distinct local populations or ‘microbial terroirs’ have been demonstrated in recent work (e.g Knight et al 2015).

This project will use the unique resource of a single block of many grape varieties on the same soil, encountering the same climatic conditions, to define the impact of grape variety only on microbial terroir. Different varieties, phenology, skin thicknesses, grape and bunch architecture, attractiveness to animal and insect pests, etc are expected to lead to different microbial populations.

Objectives/aims

The project seeks to identify novel yeast and lactic acid bacteria (for use as pure cultures) and an understanding of vine and grape attributes that favour particular species. Knowledge gained about the grape population that inoculates the fermentation will help winemakers better steer the microbes and fermentation to a desired outcome.

Industry partners