Wine Flavor 101Common Wine Taints

Napa Valley VintnersJanuary 13, 2012

UC Davis

WELCOME TO:

Overview of Today’s Topics

Linda F. Bisson

Department of Viticulture and Enology

University of California, Davis

Introduction to VENsource and Wine Flavor 101

VENsource: Viticulture and ENology System for OUtreach Research Communication and Extension

Comprehensive on-line and in-person programs aimed at maintaining the competitive edge of the wine and grape industries and in facilitating transfer of newly discovered information

VENsource On-Line

Enology Access web site:

Content rich

Problem solving guides

Aids for training

Best practices analyses

Discussion forum

Wine Flavor 101:

Series of programs defining the impact of decision making on

wine flavor

Wine Flavor 101: The NeedAdvances in wine chemistry: dissection of

wine composition and sensory perceptionMicrobe genomics enabling greater

understanding as well as ability to control metabolite effects

Grape genome: ability to target viticultural practices to enhance or diminish specific characters

Wine Flavor 101: The Important Questions

What are the key impact compounds?What are the key matrix effects?Now that we can manipulate characters, what

do we want to manipulate?What are the best ways to modify characters?

(Vineyard? Fermentation? Aging? Blending?)

Wine Flavor 101: The Realities

Personal preferences and style differ Interpretation and detection of components

differ Interactive effects are profound Intensive efforts underway internationally to

optimize and target flavor outcomes

Wine Flavor 101: The Competitive Advantage

State-of-the-Art WineryNew Research FacilitiesEnhanced Research CapabilityOptimized Working Relationship with

Industry

Wine Off-Characters

Off-colors Off-flavors Hazes/cloudiness Sediment/precipitates

Source of Off-Characters

Vineyard Unsound fruit Fermentation microbes Oxidation/reduction reactions Spoilage microbes

Off-Characters

Same off-character may come from different sources (acetaldehyde)

Some off-characters arise only in specific chemical/microbial environments

Compound(s) responsible for some taints unknown

Best course of action: not getting them in the first place!

Microbial Off-Characters

Pre-fermentation During fermentation Post-fermentation

Microbial Off-Characters

Pre-fermentation During fermentation Post-fermentation

Pre-Fermentation Off-Characters

Derive from the metabolic activities of non-Saccharomyces yeasts and bacteria

Increased impact with rot Increased impact with hang time Juice and must processing can encourage

pre-fermentation character formation

Pre-Fermentation Processing

Lower temperatures: favor non-Saccharomyces yeasts

Low, no or late sulfite additions: favor both non-Saccharomyces yeasts and bacteria

Warm temperatures: favor bacteria Oxygen exposure: favors both non-

Saccharomyces yeasts and bacteria

Pre-Fermentation Processing Lower temperatures: favor non-

Saccharomyces yeasts– Cold soak/maceration (reds)

– Cold settling (whites)

– See bloom of Hanseniaspora/Kloeckera

Pre-Fermentation Processing Low, no or late sulfite additions: favor both

non-Saccharomyces yeasts and bacteria– Favors growth of both wild lactics and acetic

acid bacteria

– Favors growth of non-Saccharomyces yeasts

Pre-Fermentation Processing

Warm temperatures: favor bacteria– Cap management strategies

– Refrigeration capacity

Pre-Fermentation Processing

Oxygen exposure: favors both non-Saccharomyces yeasts and bacteria– All organisms benefit from presence of oxygen

– Obligate aerobes not inhibited

Types of Pre-Fermentation Characters

Esters Acids

_______________________________ Higher alcohols S-compounds Aldehydes

Microbial Off-Characters Pre-fermentation During fermentation Post-fermentation

Fermentation Off-Characters

Esters S-compounds

___________________________________ Higher alcohols Acetaldehyde Higher aldehydes Volatile acids

Fermentation Off-Characters

Influenced by yeast strain Impacted by growth conditions Affected by juice composition

Fermentation Off-Characters

Influenced by yeast strain– Different strains vary ten-fold or more in

compound production within dynamic range of odor detection

– Strains dominate fermentation with differing efficiencies

Fermentation Off-CharactersImpacted by growth conditions

– Volatilization of compounds» Temperature» Head space

– Nutrient availability» Nitrogen» Micronutrients» Oxygen

– Microbial competition» Sulfite use» Inoculation practices

Fermentation Off-Characters

Affected by juice composition– Availability of precursors

– pH

– Presence of stressors» High sugar/high ethanol

» Previous microbial history

Today’s Program

Fermentation Off-Characters: the esters Lactic Acid Bacteria Taints Brettanomyces Sulfur Taints