Transcript Types of Native Fermentations

Types of Native Fermentations
Linda F. Bisson
Wine Flavor 101 January 2016
Native Fermentations: Definitions
The 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
Both are sources of microbes
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 overwinter in the winery and build up from winery, not
vineyard, biota
 And it all depends upon sanitation practices!
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 postveraison

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 nonSaccharomyces? (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:
 Glass 2:
 Glass 3:
 Glass 4:
 Glass 5:
 Glass 6:
Inoculated Time 0
Inoculated 24 hrs.
Inoculated 48 hrs.
Inoculated 72 hrs.
Inoculated 96 hrs.
Uninoculated