Types of Native Fermentations

Linda F. BissonWine Flavor 101 January 2016

Native Fermentations: DefinitionsThe term “native” with respect to wine production has several meanings:

– Not deliberately inoculated– No commercial yeast strains present– Only vineyard yeast present– Vineyard/winery resident yeast only present– No manipulation of native microbiota– Only autochthonous yeast present

Source of “Native” Flora Vineyard Winery Early in season grape microbiota may be most

important but as microbes become established on winery surfaces, winery microbiota become more important

Genetic data suggests winery microbes likely over-winter in the winery and build up from winery, not vineyard, biota

And it all depends upon sanitation practices!

Both are sources of microbes

Native Fermentations: Goals Complexity, complexity, complexity Non-Saccharomyces yeast and bacteria able to contribute to

aroma, flavor and mouthfeel properties of the wine Slower fermentation of Saccharomyces contributes to aroma

and flavor profile of wine Wines are more unique and appealing than they would be

using a “generic” strain Enhanced varietal character due to hydrolases and other

enzymes produced by a diverse microbiota or to production of aroma-enhancing compounds (matrix effects)

Not Deliberately Inoculated No commercial inoculum No tank-to-tank inoculum May be “inoculated” by winery biota

– Tank/barrel residents– Hoses/equipment residents

Depending on sanitation practices may be conducted by vineyard biota

No Commercial Yeast Strains Present Winery has never used commercial starters (ever) Winery has not introduced materials (bulk wines; used

equipment) that has seen commercial starter cultures Winery may take steps to not be accidentally

“inoculated” by natural starters from adjacent wineries Yeast lees returned to vineyard?

Only Vineyard Yeast Present Challenging: requires intense sanitation program to

eliminate winery residents each year Vineyard yeast variability from year to year both in

numbers and types of strains should be evident Winery lees may or may not be put back in the

vineyard

Vineyard/Winery Resident Yeast Only Present Recognizes challenges of not developing winery

“house” strains House strain lees may be added back to vineyard so

origins the next season may be confounded

No Manipulation of Native Microbiota No use of sulfur dioxide or other antimicrobial No additions of nutrients that would alter microbial

dynamics No oxygen addition except that occurring during

transfers No temperature control that would alter microbial

dynamics

Only Autochthonous Yeast Present Autochthonous: “originating in the place found” Strains present are not just found in the wild but originated

in that region Challenging with wine yeast as yeast DNA analyses have

shown “migration patterns” for specific strains Issues:

– If one generates a “house autochthonous” strain and uses it as an inoculum, is it still “native”?

– Should “heritage yeast” be its own category of fermentation type?

The Negative Impacts of Native Microbiota

Arrest of alcoholic/ML fermentations Spoilage character formation

– From the non-Saccharomyces microbes– From Saccharomyces due to enhanced competition for nutrients and

growth factors Loss of varietal character

– Degradation of varietal aroma/flavor compounds– Modification of varietal aroma/flavor compounds– Masking of varietal impact compounds

When Are Negative Impacts Likely? Condition of fruit: high incidence of rot/damage in

vineyard High insect presence Lack of a robust native strain of Saccharomyces ( a

trade-off between sanitation practices and use of “house” strains

Deficiencies in grape composition: nutritional stress Undesirable vineyard residents: the dreaded “bad

lactics”

Condition of the Fruit Damaged Clusters

– Rot amplifies acetic acid bacteria– Mold metabolites may be present

Uneven Ripening/Raisining– Leads to differences in flora on the surfaces of the fruit

Presence of Material Other than Grape– Soil, leaves, bark: all contain microbes– Some of these microbes can persist early in fermentation

Timing of Harvest During ripening the berry surface flora change

– More seepage from the berry providing nutrients– Yeast population continues to increase in relative numbers post-veraison

Aerobic basidiomycetes are replaced by the fermentative ascomycetes– Consume available oxygen rapidly– Create localized anaerobic zones– Produce toxic waste products

Aerobic bacilli and pseudomonads replaced by acetic and lactic acid bacteria– Produce toxins and toxic waste products

Factors Impacting Biota and Persistence pH Temperatures of holding or processing: everything is a

selection Oxygen exposure Nutrient level and diversity of nutritional components The starting biota and strains present

Native Fermentations: Styles 100% native: no additions of any microbes ever Native yeast but with ML inoculation Native Saccharomyces only or native non-

Saccharomyces? (manipulate biota using sulfur dioxide) Partial natives: inoculated at some point (the insurance

policy method) Manipulated microbiota “natives”

Manipulated Microbiota Sulfur dioxide or other antimicrobial agent used Temperature of pre-incubation/fermentation pH adjustment or selection Level of aeration Nutrient addition practices Inoculation with non-Saccharomyces yeasts and

bacteria

Partial Natives Temporal inoculation: after x days Inoculation at a specific Brix/ethanol level Inoculation at “first sign of trouble” Addition of SO2 to arrest non-Saccharomyces biota Selective feeding of Saccharomyces population

The VEN124L Trial: Test the impact of timing of inoculation of a

commercial strain of Saccharomyces Used Albariño No sulfur dioxide No nutrient additions Used a neutral yeast: EC1118

Treatments● Control: inoculated with EC1118 at 0 hours● 24hrs: inoculated with EC1118 at 24 hours● 48hrs: inoculated with EC1118 at 48 hours● 72hrs: inoculated with EC1118 at 72 hours● 96hrs: inoculated with EC1118 at 96 hours● Native: no inoculation, left to ferment with native yeast

Fermentation Data

Inoculation Timing Tasting: Glass 1: Inoculated Time 0 Glass 2: Inoculated 24 hrs. Glass 3: Inoculated 48 hrs. Glass 4: Inoculated 72 hrs. Glass 5: Inoculated 96 hrs. Glass 6: Uninoculated