Lactic acid produced by lactic acid bacteria decomposing monosaccharide and disaccharide in sauerkraut lowers ph value, and carbon dioxide produced by fermentation makes fermentation container in anaerobic state, thus preventing food from being infected and corrupted by other microorganisms and prolonging the shelf life of food. At the same time, carbon dioxide, acetic acid, ethanol, higher alcohols, aromatic esters, aldehydes, sulfides and so on. Protein produced in the fermentation process gives kimchi a flavor.