Which process produces alcohol or acid through the action of microorganisms?

Fermentation is the process that generates alcohol or acids as a result of the metabolic activity of microorganisms, primarily yeasts and bacteria. During fermentation, these microorganisms convert sugars into alcohol (such as ethanol) or organic acids (like lactic acid) under anaerobic (absence of oxygen) conditions. This process is fundamental in various food and beverage production, such as in brewing beer, making wine, and producing yogurt.

In contrast, extrusion is a food processing technique that involves forcing ingredients through a device to create shapes and textures, commonly used in snack foods and pasta production. Pasteurization is a method of heat treatment designed to kill or deactivate harmful microorganisms in food and beverages to make them safe for consumption, but it does not produce alcohol or acid. Filtration is a physical separation process used to remove solid particles from liquids or gases and does not involve the action of microorganisms.