It includes breaking the starch in the grains into a sugary liquid, called wort, and fermenting the sugars in the wort into alcohol and carbon dioxide by yeasts. The process of making beer is called brewing.

Potatoes, millet and other foods high in starch are used in different places in the world as the primary carbohydrate source. Unmalted maize can be added to the barley or wheat to lower cost. Sometimes a mixture of starch sources can be used, such as rice.

It is made most often of malted barley and malted wheat. Malic acid, naturally present in grape juice, can be converted to lactic acid by lactic acid bacteria naturally found in wineries or added artificially.īeer is the most consumed alcoholic beverage in the world. When making red wine, there is an additional fermentation step after alcoholic fermentation. To improve yeast growth, additional nutrients, like diammonium phosphate, are sometimes added in the fermentation step. It is important to keep the temperature in the fermentation vessel lower than 40✬ to keep the yeasts alive. In the fermentation process, energy that is converted to heat is produced as well. Figure: Wine grapes: The white film that covers the grapes contains wild yeasts. There are hundreds of commercially available yeast strains for wine fermentation. However, cultivated strains of Saccharomyces cerevisiae are often added to improve the consistency of the final product. These wild strains play an important role in the final properties of the drink. The yeasts used for the fermentation grow a film on the fruit or in the environment. The grapes are first cleaned of leaves and stems and the fruit is crushed into must that is ready for fermentation.

Types of wine fermentation