Production, reactivation and nutrient requirements of active dried yeast in winemaking: theory and practice

Wine yeast, from production to application, traverse an incredible range of environments. Central to their ability to not only survive but to thrive throughout this journey is their capacity to transform themselves in response to the varied conditions encountered. Wine yeast resilience alone, however, is insufficient. Producers and winemakers must be assiduous in their use of wine yeast with an understanding of yeast requirements throughout the process to achieve optimal results. Active dried yeast (ADY) starter cultures for initiating grape must fermentations are convenient, reliable and available for a wide range of strains suited to different wine types. These benefits cannot be fully realised without optimisation of: their production; reactivation of the dried product prior to inoculation; and appropriate nutrient management during fermentation. This review discusses current knowledge on production of Saccharomyces ADY for greatest biological stability and activity, and factors that affect their activity following rehydration and inoculation into grape must. The efficacy of various types of commercial additives used in reactivation of ADY and, winemaking interventions and nutrients that are used to optimise fermentation are also discussed.