Enology is the science and study of wine and winemaking. Distinct from viticulture, which studies vine-growing and grape-harvesting, enology focuses on desirable characteristics of the grapes themselves and gives winemakers a deeper understanding of the wine production process. Using analytical descriptions and sensory evaluation, enologists can make educated decisions throughout production to improve the quality of their wines.
Enology Best Practices
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.
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).
Useful Enology Charts
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.
Resources for Winemakers
Publications from MGWII
Read publications from the Midwest Grape and Wine Industry Institute about grape cultivars, composition, trials, and more.
Iowa Wine Growers Association
Membership with the Iowa Wine Growers Association gives local wine enthusiasts the chance to become involved in the industry through marketing resources, educational opportunities, and exclusive wine-growing information.
Northern Grapes Project
The Northern Grapes Project is a coordinated agriculture project directed at expanding the cold-hardy grape vineyard and winery industry through research and marketing. Local wine enthusiasts can find newsletters and information specific to cold-hardy grape varieties.
American Journal of Enology and Viticulture
The American Journal of Enology and Viticulture is the official journal of the American Society for Enology and Viticulture (ASEV) and provides peer-reviewed research papers, literature reviews, research notes, and more to winemakers.
Wine Industry News
This online resource contains up-to-date information on national wine legislation, trends within the industry, and helpful tools for wine enthusiasts.
Viticulture Enology Science and Technology Alliance
The Viticulture Enology Science and Technology Alliance (VESTA) is a National Science Foundation (NSF) funded partnership between the Missouri State University system and colleges, universities, vineyards, and wineries across America. These partners share a 21st-century vision for education in grape growing and winemaking.
Grow your winery’s economic impact, learn more about the industry, and find resources related to winemaking in the state of Iowa.
Iowa Department of Agriculture and Land Stewardship
The Iowa Department of Agriculture and Land Stewardship oversees a range of programs impacting the food and drink industries. Find out more about various regulations and consumer protections that impact wineries and vineyards in Iowa.
State of Iowa Alcoholic Beverages Division
Responsible for the regulation and control of alcohol in the State of Iowa, the State of Iowa Alcoholic Beverages Division is an important resource for local winemakers. Find out how to receive an alcohol retailer certification, obtain liquor licenses, and learn more about Iowa’s alcohol laws and regulations.
Iowa Department of Revenue
Find updated tax information impacting your winery or vineyard, from business permit registration and taxable service guidelines to forms and other resources through the Iowa Department of Revenue’s website.
Iowa Department of Tourism
Find travel guides, things to do, and places to stay in the state of Iowa. The Travel Iowa website also includes curated lists of wineries, wine trails, and tasting rooms in the area, making it easy to find local wineries to support.