Changes in the components of dry-fermented sausages during ripening

Several chemical changes occur during the ripening of dry-fermented sausage s that determine the flavor and odor of the end product. The phenomena that take place during fermentation, that is, both acidification of the sugars by lactic acid bacteria and reduction of nitrates and nitrites to nitric ox ide by micrococci have been known for several years. However, the chemical changes involved in this process, and, particularly, the agents responsible have not yet been established, although they have been attributed to chang es in the majority components (proteins and lipids) and to the ingredients added (spices and condiments) in the preparation of the original mixture. The typical flavor and odor of dry-fermented sausages cannot be attributed to volatile substances alone, but to a large number of volatile and nonvola tile compounds present in the product in suitable proportions. Microbial gr owth in the sausage together with activity of the meat endogenous enzymes a re undoubtedly partially responsible for the development of a number of aro matic and sapid compounds. However, lipid autooxidation reactions are also an important source of these substances, and it is not yet known which of t hese processes is more important in sausage ripening. Much research has foc used on the break up of triglycerides into free fatty acids, diglycerides, and monoglycerides during ripening and the progressive increase in the amou nts of different carbonyl oxidation products. Carbonyl compounds probably p lay a significant role in determining the flavor because, in general, these have very low perception thresholds, in the ppm and ppb range. Similarly, the protein breakdown to yield peptides and amino acids has been studied ex tensively, the latter being substrates of several microbial and chemical re actions that generate many flavor compounds.