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.
Soybeans form the basis of several fermented foods.
The preparation methods, the microorganisms involved in fermentation and usage of fermented oriental soy products varies greatly. In terms of use in the diet, natto and tempeh are consumed as part of a main meal and contribute to dietary protein and oil in addition to flavour. Other fermented soy products are generally used as seasonings for soups and dishes and thus contribute more to flavour than they do to nutrition in the diet. The proximate compositions of several soy products, including fermented ones, are given below. Slight variations in the traditional methods of preparation result in differences in appearance, aroma, texture and flavour characteristics in the final products.