Fermentation is one of the oldest and most economical methods of producing and preserving foods.
By the third century BC, labourers working on the Great Wall of China were consuming acid-fermented mixed vegetables. 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.