5. Flavor compound changes before and after fermentation In studies of volatile flavor compounds of meat, more than 800 compounds have been discovered (Su, 2000), including alkyl, alkenyl, alcohols, aldehydes, ketones, ethers, esters, carboxylic acids, and heterocyclic compounds with oxygen, nitrogen, and sulfur, among which the sulfur compounds reflect the basic meat flavor and carbonyl compounds give unique flavor to the meat. The contribution of different volatile compounds to the meat aroma and overall flavor depends on its aroma value, which is the concentration/threshold value. The volatile with an aroma value > 1 may have a direct influence on the meat aroma, while the volatile with