The Effects of Temperature Linda F. Bisson Department of Viticulture and Enology University of California, Davis, CA

Outline of Presentation Impacts of Fermentation Temperature on Wine Composition Impacts of Fermentation Temperature on Wine Composition Control of Temperature Control of Temperature Temperature Optimization Temperature Optimization

Impacts of Fermentation Temperature in Red Fermentations

Impacts of Fermentation Temperature Extraction Extraction Volatilization Volatilization Chemical Reactions Chemical Reactions Enzymatic Reactions Enzymatic Reactions Microbial Growth and Persistence Microbial Growth and Persistence

Extraction: Skin, Seeds, Stems Extract anthocyanins from skin cells Extract anthocyanins from skin cells Extract phenolic participants in co- pigmentation Extract phenolic participants in co- pigmentation Extract phenolic compounds that participate in stable pigment and tannin formation Extract phenolic compounds that participate in stable pigment and tannin formation Extraction of flavor components Extraction of flavor components Does seed extraction occur? Does seed extraction occur? Impact of stem extraction (whole cluster ferments)? Impact of stem extraction (whole cluster ferments)?

AJEV (1987) 38(2):120-7

Location of Compounds in Berry Sucrose Glucose

Location of Compounds in Berry MalateTartrate

Location of Compounds in Berry Phenols Phenolic compounds

Location of Compounds in Berry Potassium

Location of Compounds in Berry Inorganic anions

Factors Affecting Extraction: Cap Management TEMPERATURE TEMPERATURE TIME TIME MIXING MIXING MACERATION MACERATION USE OF ENZYMES USE OF ENZYMES

Volatilization Higher temperature = greater loss of volatiles Higher temperature = greater loss of volatiles Impact depends upon reservoir of volatile compounds Impact depends upon reservoir of volatile compounds Also impacted by vigor of yeast fermentation Also impacted by vigor of yeast fermentation Fermentation rates faster at higher temperatures Fermentation rates faster at higher temperatures

Chemical Reactions Endothermic (heat absorbing) reactions go faster at higher temperature Endothermic (heat absorbing) reactions go faster at higher temperature Exothermic (heat releasing) reactions go slower at higher temperature Exothermic (heat releasing) reactions go slower at higher temperature Some hydrolytic reactions stimulated by heat Some hydrolytic reactions stimulated by heat

Enzymatic Reactions Some enzymatic reactions are endothermic, some exothermic Some enzymatic reactions are endothermic, some exothermic Heat can speed up or slow down enzymatic reactions Heat can speed up or slow down enzymatic reactions If too hot, enzymes lose structure and become inactivated If too hot, enzymes lose structure and become inactivated

Hot Fermentations: Trade off between extraction of color and phenolic compounds and loss of aromatic components

Temperature and Microbes Microbes have optimal temperatures for growth Microbes have optimal temperatures for growth Warmer favors bacteria Warmer favors bacteria Warmer favors Saccharomyces over non- Saccharomyces wine yeasts Warmer favors Saccharomyces over non- Saccharomyces wine yeasts Warmer impacts ethanol tolerance Warmer impacts ethanol tolerance

Temperature and Microbes Temperature impacts: Temperature impacts: –Metabolic rates –Metabolite profiles –Cell leakiness –Tolerance to other stresses –Higher temperatures: higher ester formation but higher retention of off-esters (longer chain)

Control of Temperature

Fermentation is exothermic: rate of heat release directly proportional to rate of fermentation Fermentation is exothermic: rate of heat release directly proportional to rate of fermentation If too hot, thermal death may occur and such fermentations are difficult to restart If too hot, thermal death may occur and such fermentations are difficult to restart ΔT (ºF) = 1.17 x Brix value, depends upon ambient temperature, vessel characteristics, surface to volume ratio, thermal conductivity of wall ΔT (ºF) = 1.17 x Brix value, depends upon ambient temperature, vessel characteristics, surface to volume ratio, thermal conductivity of wall

Type of Cooling System Tank type and size of jacket Tank type and size of jacket Internal cooling Internal cooling Coolant heat transfer coefficient Coolant heat transfer coefficient Coolant temperature Coolant temperature

Tank Temperature Temporal fluctuation: due to changes in metabolic activity Temporal fluctuation: due to changes in metabolic activity Fluctuation within tank Fluctuation within tank –Cooler nearest the jacket, warmer in center –Warmer nearest the cap (enhanced metabolic activity) –Dependent upon mixing, cap management practices and temperature equilibration

Optimization of Fermentation Temperature

Depends upon varietal Depends upon varietal Depends upon style Depends upon style –Reliance on volatile compounds –Strength of reservoir of volatiles

Optimization of Temperature To achieve optimal pigment extraction To achieve optimal pigment extraction To minimize loss of aromatic volatiles To minimize loss of aromatic volatiles To avoid spoilage organisms To avoid spoilage organisms To prevent arrest of fermentation To prevent arrest of fermentation

Optimization of Temperature Influenced by: Sulfite use Sulfite use Vineyard flora Vineyard flora Winery flora Winery flora Site characteristics Site characteristics Presence of rot/cluster damage Presence of rot/cluster damage

The Experiment: Ferment Cabernet Sauvignon at four different temperatures: 60, 70, 80 90ºF Ferment Cabernet Sauvignon at four different temperatures: 60, 70, 80 90ºF Examine color and sensory differences Examine color and sensory differences Using TJ fermenters Using TJ fermenters

Fermentation Curves of Cabernet Sauvignon

Temperature Flight Glass 1: 60° Glass 1: 60° Glass 2: 70° Glass 2: 70° Glass 3: 80° Glass 3: 80° Glass 4: 90° Glass 4: 90° Glass 5: Mixture of all 4 Glass 5: Mixture of all 4