Enology

Tartaric Acid Chart  

This chart shows how to calculate the amount of tartaric acid required to raise the acidity. Monitoring and controlling Tartaric acid is a crucial step in optimizing the flavor and character of your wine, and testing should occur at all stages of production but especially before fermentation to ensure an optimal environment.

Desirable Sugar, Acid, and pH Levels  

This chart shows the sugar and acid values suited for making dry table wines. For making other types or styles of wine, the desired composition in terms of sugar, acid, and pH could be different. Acids are crucial in boosting the effect of sulfur dioxide, which essentially protects wines from spoilage and becoming rotten. A good acidity level also fends off most unwanted bacteria, as these compounds are unable to survive in low pH solutions. 

pH is a measure of the acidity (or alkalinity) of an aqueous solution, or, in winemaking, juice or wine. pH greatly affects the taste of wine as well as microbial stability.  The most important aspect of pH in winemaking is that microbial stability and spoilage risks are highly correlated to pH. Microorganisms thrive at higher pH. With the less acidic environment, the winemaker needs to compensate with higher doses of sulfur dioxide (SO2). High-pH wines also tend to oxidize faster and therefore not age as well. 

Potential Alcohol Yield   

Brix measures must levels (sugar) in wine grapes that ultimately determines how much alcohol a wine will have. This chart shows the potential alcohol by volume resulting from the fermentation of the must at various ºBrix levels. The amount of fermentable sugar (glucose and fructose) in juice and the average conversion rate of sugar into alcohol can be used to predict the potential alcohol level in wines.

Sulfur Dioxide Additions Using Potassium Metabisulfite  

Sulfur dioxide is the primary preservative used in wine. It acts as an antioxidant and antimicrobial agent to help stabilize wine through its duration. 

During the winemaking process, essential practices for preserving wine quality include oxygen management, proper sulfur dioxide use, inhibiting volatile acidity formation and other microbial spoilage, and thorough cleaning and sanitation.

Oxygen Management  

Excessive oxygen exposure for wines can result in oxidized sensory characteristics. It can also cause SO2 levels in the wine to drop and promote microbial spoilage. The sensory effects are difficult (or impossible) to correct once they have occurred. Oxygen exposure is limited by minimizing headspace when possible and using carbon dioxide, argon, or nitrogen gas to drive oxygen out of tanks, hoses, and bottles.

Sulfur Dioxide Use

Proper use of sulfur dioxide must consider the current SO2 measurement, the pH of the wine, and the intended next steps for the wine (such as bottling). Sulfur dioxide should be measured frequently (approximately every four weeks), and additions are made as necessary to maintain a protective level.

Cleaning and Sanitation

Thorough cleaning and sanitation of equipment are critical for preventing spoilage microbes or other unwanted contaminants. Cleaning should be done with mechanical action and using cleansers designed to remove soil deposits. Sanitizers are formulated to reduce microbial populations effectively. For all products, the manufacturer’s directions should be followed closely to ensure they work as intended.

Volatile Acidity and Microbial Spoilage

The risk of microbial spoilage can be reduced through oxygen management, sulfur dioxide use, and sanitation practices. However, the risk cannot be eliminated, so winemakers must remain vigilant. Routine chemical analysis and sensory evaluation for volatile acidity (acetic acid/vinegar aroma) or other off aromas are critical for detecting and addressing issues early. If microbial spoilage does occur, mitigation requires both removal of the microbes and chemical corrective measures (such as volatile acidity removal by reverse osmosis).