Even today, various fermented foods of animal and plant origin make up an essential part of the diet in many parts of the world. The variety of fermented foods has gradually grown and now ranges from fish pastes to soy sauce to vegetarian meat substitutes. Traditionally, however, they are normally encountered in non-affluent, densely populated areas where traditional recipes are handed down through generations and preparation is a household art. In addition to preservation, fermenting foods can also have the added benefits of enhancing flavour and improving the nutritional value. During fermentation it is the unique properties of the bacteria and fungi present that increases the levels of proteins, vitamins, essential amino acids and fatty acids in the food.
Some microorganisms produce flavour compounds, complex polysaccharides or organic acids.
Fungi isolated during tempeh, ragi, sufu or koji fermentation have also been shown to produce antibacterial compounds, which have a beneficial effect by preventing growth of other bacteria, and thereby increase food safety. Methods of preparing soybeans for consumption were developed, and soybeans and soy products became a part of the traditional culture. Gradually, soybean cultivation and the preparation of soy products spread to Korea, Japan and other oriental countries. Methods of preparation were modified and new types of soy products created. The preparation of soy products has now spread to the rest of the world and with advances in soybean chemistry, processing and packaging technology the traditional methods of preparation have been dramatically modernized.