Wine Chemistry

Importance of Chemical Understanding of Wine

An explanation of the chemical processes involved in the production of wine and in those that determine the appearance, flavor, and aroma of different wines.

Wine-making is essentially a chemical process. It involves a chemical reaction in which sugars are turned to alcohol and carbon dioxide in the presence of yeast. There are also many other chemical processes going on which affect the strength, appearance, color, and taste of the wine.

Grape Ingredients

Wine is made from grapes. In addition to water, grapes contain two different sugars: glucose and fructose, tartaric acid, malic acid, amino acids, and a few other chemicals. The chemical processes of wine-making involve several of these components and the amount of each is important in determining the character of the wine produced.

Glucose to Ethanol

The most important chemical reaction in the winemaking process is the breaking down of glucose by yeast, forming ethanol and carbon dioxide as gas. There are various important factors at this stage that affect the wine. First, sulfur dioxide gas is passed through the crushed grapes to kill off wild yeasts. If this was not done the yeasts would compete with one another and fermentation would stop prematurely.

Controlling pH

Next, the pH (acidity) of the grape pulp needs to be controlled. If grapes are too sweet, then their pH is too high (acidity too low) then fewer flavors are produced in the wine. The pH can be lowered by adding tartaric acid at the start of the fermentation process.

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Finally, the temperature must be controlled throughout the process. Fermentation is an exothermic process (heat is produced by the reaction), but there are various reasons for keeping the temperature as low as possible. Yeast stops growing as temperatures increase and will die at higher temperatures. Also at lower temperatures colors and flavors are extracted from the skins and by-products such as esters and aromatic compounds are produced which add to the flavor and also the clarity of the wine.

Advances in Wine Chemistry

As more and more research is done into the constituents of the wine and the way they are formed, two areas, in particular, stand out. First is the idea that regular consumption of wine in moderation is good for you. Statistical studies have shown that wine drinkers are less prone to heart disease, cancer, and other diseases. This may be explained by the fact that wine drinkers tend to have a healthier lifestyle and are in groups that are less at risk to these diseases. It may be that there are certain chemicals that combat certain conditions, for example, the antioxidant resveratrol which may reduce cholesterol and the risk of Alzheimer’s disease. These chemicals can, of course, be found in other food and drink without the damaging presence of alcohol.

Improving Wine Making

Then there is the development of the scientific study of the process of winemaking, and the technology to improve it. There are many who would desire to depend on the natural processes of grapes and fermentation. Others have studied the chemicals which make up wine, seeking to determine those that cause the flavor, aroma, and appearance of wine so that these can be manipulated in the production process. This tension will continue as the desire to make money affects the love of natural processes.

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