Chemistry Questions

1. Red wine fermentation using whole bunches (e.g. Burgundy Pinot Noir)2. Carbonic maceration (e.g. Beaujolais)3. Whole bunch pressing for some white wines

Also called wild yeast, it is present in the vineyard and the winery, and includes species like Kloeckera and Candida. Most other species beyond the dominant Saccharomyces cerevisiae die once the alcohol content rises above 5%.

1. Volatile acidity2. Naturally produced SO23. Wine aromatics (precursors like thiols and terpenes, and esters)4. Glycerol

By adding calcium carbonate (chalk) or potassium carbonate, it lowers acidity by the formation and precipitation of tartrates. A higher-tech option is deacidification by ion exchange.

Advantages-Add complexity by producing different aroma compounds-Costs nothing-Yeast can be unique to a place or region (i.e., Terroir)-Used in marketingDisadvantages-Fermentation may start slowly and could introduce volatile acidity buildup risk or spoilage organisms-Fermentation to dryness may take longer, or stuck fermentations may occur-Consistency cannot be guaranteed

1. Add water2. Reverse osmosis - forming cross-flow filtration that removes flavorless permeate of alcohol and water which can be distilled to remove alcohol3. Spinning cone - extracts volatile aroma compounds and then removes alcohol, with aromas being blended back in

-Tempreatures below 15°C / 59°F-Low pH-Moderate SO2-Added lysozymes, which kills lactic acid (conducted by the winemaker)

When lactic acid bacteria convert malic acid into lactic acid and carbon dioxide, producing heat. It occurs after alcoholic fermentation and occasionally during it. It requires temperatures between 18-22°C / 64-72°F, moderate pH between 3.3-3.5, and low total SO2. It can start naturally, or by adding ('inoculating') cultured lactic acid bacteria.

-Cool: 12-16°C / 54-61°F - for white and rose, promoting production of esters -Mid: 17-25°C / 63-77°F - for easy drinking red, retaining fruit aromas and low tannin extraction, or for less fruity white wines or barrel-fermented whites-Warm: 26-32°C / 79-90°F - for red with pronounced flavor and tannins, maximum extraction of color and tannins and maybe some fruit flavor loss

Minimum natural potential alcohol = 8%; max enrichment = +3%; max alcohol level in final wine if enriched = 11.5% for white, 12% for red

1. Tartaric acid - most common2. Citric acid - not permitted in EU3. Malic acid - less common 4. Lactic acid - for after malolactic conversion

Minimum natural potential alcohol = 9%; max enrichment = +1.5%; max alcohol level in final wine if enriched = 13.5%

1. Reduction in acidity and rise in pH - lactic acid is weaker than malic2. Some color loss in red wines3. Grater microbial stability4. Modification of flavor - slight loss in fruit character and addition of buttery notes (white)5. Increase volatile acidity

Conversion of sugar into ethanol (ethyl alcohol) and CO2, carried out by yeast anaerobically. It also produces heat.

Before fermentation to the must; before maturation to the wine. Powdered tannins clarify musts, and in red wines, help stabilize color and improve mouthfeel.

Before, during or after fermentation, although winemakers prefer to acidify before fermentation

Yeasts can be stressed, causing them to produce undesirable sulfur compounds or stop fermenting.

-A viable temperature range-Yeast nutrients, especially nitrogen-Absence of oxygen

Also called selected yeast or commercial yeast, this is a strain selected in a laboratory and grown in volumes suitable for scale.

Advantages-Reliable, fast fermentation to dryness-Low levels of volatile acidity and less risk to spoilage-Consistency-Large selection of strains available to choose from Disadvantages-Some believe it creates similarity of fruit expression (i.e., industrial wine)-Adds to costs of commercial product