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. It is a crucial stage in bread-making process, resulting in a soft, fluffy bread. Fermented goods usually have a pretty distinctive taste and aroma, resulted from the liberation of gases and other enzymes from the microorganisms.