Several chemical changes occur during the ripening of dry-fermented sausages 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 oxide 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 changes 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 nonvolatile compounds present in the product in suitable proportions Microbial growth in the sausage together with activity of the meat endogenous enzymes are undoubtedly partially responsible for the development of a number of aromatic and sapid compounds However, lipid autooxidation reactions are also an important source of these substances, and it is not yet known which of these processes is more important in sausage ripening Much research has focused on the break up of triglycerides into free fatty acids, diglycerides, and monoglycerides during ripening and the progressive increase in the amounts of different carbonyl oxidation products Carbonyl compounds probably play 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 extensively, the latter being substrates of several microbial and chemical reactions that generate many flavor compounds

Changes in the components of dry-fermented sausages during ripening.

The processing of dry-cured ham is very complex and involves numerous biochemical reactions that are reviewed in this article. Muscle proteins undergo an intense proteolysis, resulting in a great number of small peptides and high amounts of free amino acids. The enzymes responsible of these changes are proteinases (cathepsins B, D, H, and L and, to a less extent, calpains) and exopeptidases (peptidases and aminopeptidases). Muscle and adipose tissue lipids are also subject to intense lipolysis, generating free fatty acids by the action of lipases that, in a second stage, are transformed to volatiles as a result of oxidation. Sensory profiles of dry-cured ham are strongly affected by these enzymatic reactions. In addition, the activity levels of the muscle enzymes significantly depend on the properties of raw ham, such as age and crossbreeding as well as the process conditions such as temperature, time, water activity, redox potential, and salt content. Thus, the control of the muscle enzyme systems, mainly proteases and lipases, is essential for the standardization of the processing and/or enhancement of flavor quality of dry-cured ham.

The role of muscle proteases and lipases in flavor development during the processing of dry-cured ham

Proteolysis and lipolysis in flavour development of dry-cured meat products.

Flavor is an important quality attribute which relates to the organoleptic characteristics of meat. Although perception of flavor is a complex phenomenon, odor is the most important single factor contributing to the overall characteristics of flavor. A large number of compounds have been identified in the volatile fraction of red meats and poultry. An overview of the chemical constituents present in the volatiles of beef, pork, mutton, and chicken is presented according to species and arranged by chemical class--hydrocarbons, alcohols, acids, aldehydes, ketones, sulfides, heterocyclic compounds, etc. The volatile components of cured and uncured pork are compared. The field of meat flavor is assessed in terms of what has been accomplished and the direction in which it may proceed. Techniques for analysis of these volatiles are briefly described.

Meat flavor volatiles: A review of the composition, techniques of analysis, and sensory evaluation

Volatile components of dry cured Iberian ham

SUMMARY
Volatile compounds isolated from dry-cured hams were tentatively identified by gas chromatography retention times and further verification of the compounds made by infrared spectroscopy. These compounds were as follows: formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde, acetone, diacetyl, methyl ethyl ketone, formic acid, acetic acid, propionic acid, butyric acid, and isocaproic acid. RF values and selective indicators were used to identify ammonia and methylamine. Selective trapping was used to identify hydrogen sulfide and trace amounts of disulfides and/or monosulfides.

Herbert W. Ockerman

Papers

Volatile Chemical Compounds in Dry‐Cured Hamsa,b