Managing Alcohol
Fermentation –
Good Fermentation Practices
Michigan Wine & Grape Conference, Grand Rapids
February 24, 2010
Gordon Specht
Development and production of…
Yeast
Bacteria
…and their derivatives
How to keep the yeast
happy and minimize
risks…
Good Fermentation
Practices
(GFP)…
Sugar
If Good Fermentation Practices
are used...
if not...higher risk of sluggish
or stuck alcohol fermentation
finish and...
Fermentation Time
Factors affecting Fermentation
Management - Key Interrelationships
JUICE or MUST
TEMPERATURE
CELL
NUMBERS &
HEALTH
YEAST STRAIN
OPTIMUM
FERMENTATION
MANAGEMENT
TOXIC
FACTORS
NUTRITIONAL
FACTORS
COMPETITIVE
FACTORS
4 phases of Alcohol
Fermentation
Stationary
Yeast
Decline
Population
2-4 million
CFU/mL
Exponential
Growth
Lag
Fermentation time
In the winery Good Fermentation
Practices should be used during…
>100-150 million
CFU/mL
2-42-4
million
million
CFU/mL
CFU/mL
Fermentation time
In the winery Good Fermentation
Practices should be used during
yeast rehydration…
>100-150 million
CFU/mL
2-42-4
million
million
CFU/mL
CFU/mL
Fermentation time
Good Fermentation Practice (GFP)
at yeast rehydration stage:
;Proper Yeast Rehydration &
Handling
;Addition of micronutrients
;Directly feed selected yeast with
balance of key vitamins and
minerals
;Why?
;They won’t be used by ambient
microbes or bound by must
components
;Helps yeast population and health
80
Viability: 70% = 49 x 106 live cells
Yeast Viability
70
60
50
Viability: 43% = 23 x 106 live cells
40
30
Control 18°C
20
Goferm 18°C
10
0
0
200
400
Hours
Similar results at 24°C and 28°C, there is a strong positive effect
on yeast viability when yeast stimulant GoFerm (minerals and
Vitamins) added during yeast rehydration.
4 Easy Steps
for Rehydrating Yeast
and Inoculating Juice or Must
4 Easy Steps
for Rehydrating Yeast
and Inoculating Juice or Must
4 Easy Steps
for Rehydrating Yeast
and Inoculating Juice or Must
4 Easy Steps
for Rehydrating Yeast
and Inoculating Juice or Must
>100-150 million
CFU/mL
In the winery Good Fermentation
Practices should be used during
the beginning of yeast
fermentation…
2-42-4
million
million
CFU/mL
CFU/mL
Fermentation time
GFP at beginning of fermentation:
red musts
;If needed addition of complex
nutrients at the end of yeast lag
phase
;Under medium or low Yeast Available
Nitrogen Conditions (YANC)
;Nitrogen as ammonia and alphaamino acids
;Additional survival factors sterols
and unsaturated fatty acids
;Addition of oxygen as soon as the
cap is formed (usually 15 g/L
sugar fermented)
GFP at beginning of fermentation:
red musts
;If needed addition of complex
nutrients at the end of yeast lag
phase
;Under medium or low Yeast Available
Nitrogen Conditions (YANC)
;Nitrogen as ammonia and alphaamino acids
;Additional survival factors sterols
and unsaturated fatty acids
;Addition of oxygen as soon as the
cap is formed (usually 15 g/L
sugar fermented)
>100-150 million
CFU/mL
In the winery Good Fermentation
Practices should be used during
the yeast exponential growth
phase…
2-42-4
million
million
CFU/mL
CFU/mL
Fermentation time
GFP at yeast exponential growth
phase
;Speed of yeast multiplication
during growth phase
Don’t grow yeast up too fast…
temperature management
Low alcohol
concentration
High alcohol
concentration
Slow alcohol
excretion
In the winery Good Fermentation
Practices should be used during
1/3 – 1/2 through fermentation…
>100-150 million
CFU/mL
2-42-4
million
million
CFU/mL
CFU/mL
Fermentation time
GFP ~1/3rd through the
fermentation: red must
;If needed addition of complex
nutrients at ~1/3rd through the
ferment under medium or low
YANC
;Nitrogen as ammonia and alphaamino acids
;Additional survival factors sterols
and unsaturated fatty acids
;Oxygen addition at one third of
sugar depletion
GFP during peak of fermentation:
red musts
Cap
;Maximum temperature
reached under the cap
during the fermentation
Fermenting Juice
Yeast Biomass
In the winery Good Fermentation
Practices should be used during
the last ¼ of fermentation…
>100-150 million
CFU/mL
2-42-4
million
million
CFU/mL
CFU/mL
Fermentation time
GFP during the last quarter of
fermentation:
red musts
;Regular movement of
the yeast during their
death phase
;Deep punching down
;Bring the yeasts back
up into suspension
Move your yeasts!
Delestage
Complete draining of
fermenter
O2
GFP : whites
; Osmotic shock on the yeast
; Yeast cell content of stress resistant factors
; Addition of fatty acids, sterols, vitamins, amino acids
and micronutrients at the inoculation step
; Temperature shock in cold juices
; Grape juice solids (pectic flakes)
; Oxygen addition as soon as the fermentation is active
(usually 15 g/l sugar fermented)
; Oxygen addition at one third of sugar depletion
; Addition of ammonia at one third of sugar depletion
; Addition of fatty acids, sterols and alpha-amino acids
at one third of sugar depletion
; Low temperature during the yeast death
phase
; Regular movement of the yeast during their death
phase
4 Easy Steps
for Rehydrating Yeast
and Inoculating Juice or Must
What are pectic flakes?
After a cold settling with pectic enzymes
Clear juice
Pectic flakes
Heavy solids
Special constraints : be even
more careful applying GFP
• Large tanks (>25,000 gal.) or tall &
narrow tanks : an important consideration
• Uncertain hygiene in the cellar
• End of harvest
• Other unknowns : personnel experience,
training, knowledge of procedures, etc.
Good Fermentation Practices (GFP) Risk
Management…Very critical above pH 3.5!
LYSOZYME
Selected
Yeast
SO2
Viable Cells (cfu/ml)
108
107
Further
Microbial
control as
needed
SO2
106
105
104
103
102
10
Gluconobacter
Lactobacillus
Pediococcus
HARVEST
TRANSPORT
AF
spontaneous Oenococcus
Acetobacter
AGEING
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