Fermentation
Introduction
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In the context of food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology.
Biochemical Overview
Fermentation is a natural process that humans have used for thousands of years for the production of food and beverages, and more recently, fuels. In the absence of oxygen, cells can convert sugars and other organic molecules into cellular energy and a byproduct, typically a type of alcohol such as ethanol, or gases such as carbon dioxide. This process is essential for many types of microorganisms, as it allows them to produce energy without the need for sunlight or other external energy sources.
Types of Fermentation
There are several types of fermentation, classified by the end products which they produce. These include alcoholic fermentation, lactic acid fermentation, and acetic acid fermentation, among others. Each of these types of fermentation is carried out by different species of microorganisms, which thrive under different conditions and produce different byproducts.
Alcoholic Fermentation
Alcoholic fermentation is the process by which yeasts, and some other types of cells, convert sugars into ethanol and carbon dioxide. This process is used in the production of alcoholic beverages such as beer and wine, as well as in the production of ethanol for fuel and other industrial uses.
Lactic Acid Fermentation
Lactic acid fermentation is a metabolic process by which glucose and other six-carbon sugars are converted into cellular energy and the metabolite lactate, which is lactic acid in solution. It is an anaerobic fermentation reaction that occurs in some bacteria and animal cells, such as muscle cells.
Acetic Acid Fermentation
Acetic acid fermentation is the process by which ethanol produced by alcoholic fermentation is converted into acetic acid (or vinegar). This process is carried out by acetic acid bacteria, and is used in the production of vinegar and other sour foods.
Fermentation in Food and Beverage Production
Fermentation is used in the production of a wide variety of foods and beverages worldwide. These include alcoholic beverages such as beer and wine, as well as a wide variety of fermented foods such as yogurt, cheese, pickles, sauerkraut, and kimchi.
Fermentation in Alcoholic Beverages
The production of alcoholic beverages is one of the oldest and most common uses of fermentation. The process is used to produce beer, wine, and spirits, among other beverages. The specific types of fermentation used, and the conditions under which they are carried out, can greatly affect the flavor and other qualities of the resulting beverage.
Fermentation in Food Production
Fermentation is also used in the production of a wide variety of foods. These include dairy products such as yogurt and cheese, fermented vegetables such as pickles and sauerkraut, and fermented soy products such as soy sauce and tempeh. In addition to preserving foods and enhancing their flavor, fermentation can also increase their nutritional value and digestibility.
Fermentation in Energy Production
In addition to its uses in food and beverage production, fermentation is also used in the production of biofuels. This includes the production of ethanol from corn and other crops, as well as the production of biogas from organic waste.