Wine Flavor 101B Introduction to Native Fermentations

Impact of Winemaking Technologies Impact on composition When to use Unintended consequences Value added versus cost (value may be important even if it is just to marketing) What to do when things go wrong

IMPACT ON COMPOSITION

Impact of Native Fermentation on Composition Chemical complexity derived from the biological activities of a consortium of microorganisms Slower fermentations: less heat, less loss of volatile compounds Enhanced mouth feel and finish Better stability post-fermentation

Types of Native Fermentations Vineyard Microbiota? Winery Microbiota? Both?

Types of Native Fermentations Native non-Saccharomyces organisms? Yeast? Bacteria? Both? Native Saccharomyces? All of the above?

Types of Native Fermentations “True” native microbiota Manipulated native microbiota Partial native microbiota Inoculated native microbiota

“True” Native Microbiota No inoculation: autochthonous microbiota No use of additions or chemical or physical changes to manipulate microbial populations

Source of Native Microbiota Vineyard Winery surfaces

Source of Native Microbiota Vineyard site effects Winery sanitation practices Winery production practices

Vineyard Site Effects Humidity Average temperature Soil and vine microbiota Disease pressure Insect vectors Adjacencies Vineyard practices Number and timing of drive throughs Irrigation Fertilizer use and application practices

Winery Sanitation Types of agents used How used (how often, how rigorous, before and after use) Goals for reduction in microbial counts Are all surfaces approached with the same target microbe goals?

Winery Production Practices Crushing operation Cold soaks Cold settling Hot cap extraction Temperature of fermentation Type of fermentation vessel Oxygen exposure Pressing regimen

Even if you do not intend to manipulate the microbiota, you are by default

Microbial Requirements for Growth Permissive Conditions Absence of Non-Permissive Conditions

Permissive Growth Requirements Nutrients Macronutrients Micronutrients Allowable pH range Allowable osmotic range: “water activity” Allowable temperature range

Non-Permissive Conditions Lack of requirements: competition Presence of inhibitory conditions Chemical inhibitor Physical environment inhibition

Microorganisms differ in what defines permissive and non-permissive conditions

Microbial Ecosystems Are dynamic Depend upon relative numbers Depend upon relative metabolic activities Depend upon type of growth: surface (biofilm) or free floating (planktonic) Impacted by subtle changes in the environment

Manipulated Native Microbiota No inoculation Use of sulfite Use of nutrient additions Use of temperature to alter competitiveness Use of physical means to remove/alter microbial populations

Partial Native Microbiota Fermentation No inoculation at onset of enabling microbial activity Inoculation occurs at some point in process Point in process: Early to initiate fermentation After native yeasts have started Near end to assure completion Inoculant may be: Commercial strain Active fermentation

Inoculated Native Microbiota Fermentation Inoculate with non-Saccharomyces organisms Simultaneously with Saccharomyces Inoculate sequentially with Saccharomyces

WHEN TO USE

Issues in Use of Native Fermentations Unpredictability Microbiota present Risk factors for spoilage Risk factors for arrest of fermentation

Risk Factors for Spoilage Unsound fruit High microbial loads in winery/deficient sanitation practices Insect invasion of vineyard Issues with fruit composition Very slow start of fermentation

Risk Factors for Arrest of Fermentation Unsound fruit High and unchecked inhibitory microbial populations Nutrient availability decreased Creating a non-permissive environment for fermentation

When Not to Use When risk factors are high: Unsound fruit, fruit track record is “difficult to ferment” When you cannot blend it out if there is a problem Insurance policy (10% of volume inoculated as a precaution) is not possible

UNINTENDED CONSEQUENCES

Unintended Consequences Get some characters/impacts you want and some you do not (changes in flavor versus loss of color) May be addressed by manipulating microbiota Very long fermentations that result in too much oxygen exposure or lead to greater loss of grape impact compounds (style too “microbial”)

TODAY’S PROGRAM

So What Did We Do? We started with unsound fruit...

Sulfite Native Trial Goal: Assess impact of sulfite additions on resulting wine composition following native fermentation. Used: Chardonnay that had pervasive low cluster percentage rot issues Sulfite range: 0, 15, 25, 50, 100, 200 ug/L

Sulfite Range Lower levels inhibit bacteria but not yeast Higher levels inhibit within yeast and select for more resistant organisms

What Did We Expect to See? Problems at the low end of sulfite use At some level of sulfite the inhibitory microbes would be inhibited and fermentation progression would improve Wines would differ in things other than just residual sugar (and we were not disappointed)

Use of pH to Manipulate Microbiotoa Goal: When starting with unsound fruit, can pH alteration be a useful tool to manipulate microbiota? Used: a red blend (to get the right starting pH) pH range: 3.3, 3.5, 3.7, 3.9

What Did We Expect to See? There would be microbial differences There would be unintended consequences

Sulfites Tasting Chardonnay: pH 3.6; 22.4 Brix; TA: 5.76 g/L

Sulfite Tasting Glass 1: Native, 0, no sulfites during fermentation Glass 2: Native, 15 ppm sulfite Glass 3: EC1118, 15 ppm sulfite Glass 4: Native, 50 ppm sulfite Glass 5: EC1118, 50 ppm sulfite Glass 6: Native, 100 ppm sulfite

pH Tasting Glass 1: pH 3.3 Glass 2: pH 3.5 Glass 3: pH 3.7 (control) Glass 4: pH 3.9