Non-Saccharomyces Strains in Wine

Linda F. Bisson

Department of Viticulture and Enology

University of California, Davis

Role of Non-Saccharomyces Yeast in Wine Aroma

Native FermentationsDeliberate Inoculation

NATIVE FERMENTATIONS

Native Fermentations

Rely on microbial flora of grapes and wineries to conduct fermentation

No deliberate inoculation with commercial strains

May be inoculated from an existing native fermentation

Native Fermentations

Diversity of yeast and bacterial speciesNumbers and persistence impacted by

grape/must/juice treatmentsNumbers and persistence impacted by

winery Saccharomyces flora

The Most Important VariablesCondition of the fruit: level of rotTime of harvestProcessing conditions

– Oxygen exposure

– Solids level

Juice/Must amendmentspHSulfite/antimicrobial additionTemperature

Yeast Native Flora

Show strong impacts of maturityShow differences by climateShow seasonal effectsShow differences by varietalShow site effectsMore strongly influenced by insect

trafficking

The Most Common Yeasts of the Berry Surface Yeast % of Total IsolatesKloeckera apiculata/

Hanseniaspora uvarum 65-80

Candida species 5-10

Issatchenkia 5-10

Metschnikowia 5-10

Pichia species 10-20

Basidiomycetes 10-20

SaccharomycesNot often isolated from vineyardsDepends upon practice of dumping yeast

lees in vineyardDepends upon level of rotIs present but in very low numbers, one out of

ten million yeast isolatesEven at these low numbers will dominate

wine fermentations

Impacts of Wild Yeast Flora

Ester productionTerpene productionHydrolytic enzyme production (release of

bound flavor precursors)Carotenoid degradation?Source of stress for Saccharomyces

The Common Wild Yeasts

Ethyl Acetate Producers:– Kloeckera/Hanseniaspora

– Candida stellata

Ester Producers:– Candida: other species

– Metschnikowia

– Issatchenkia

– Pichia species

NON-SACCHAROMYCES INOCULANTS

Non-Saccharomyces Inoculants

Mixtures of Saccharomyces and non-Saccharomyces strains– Separate inoculations

– Combined in one packet

Provide positive benefits of complexity of wild fermentations with a low risk of off-characters

Kluyveromyces thermotoleransTorulaspora delbrueckii

HYBRID STRAINS

Hybrid Commercial StrainsForced mating of two closely related but

different speciesParental strain often sterile but combines

properties of both parental strains in the hybrid

Second Flight: Hybrids and Non-Saccharomyces Strains

Glass 1: Native (no inoculation)Glass 2: DV10 (control S. cerevisiae)Glass 3: Cross Evolution (hybrid)Glass 4: NT116 (hybrid)Glass 5: Rhythm (60Sc:40Kt)Glass 6: Melody (60Sc:20Kt:20Td)