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

Changes in the colour and opacity of meat

Nitrite and nitrosyl compounds in food preservation.

The experiments described in this report were aimed at determining whether L-arginine (L-arg)-derived nitrogen oxidation products (nitric oxide, nitrous acid, nitrites) are involved in the intracellular killing of Leishmania parasites by activated murine macrophages in vitro. Peritoneal or bone marrow-derived macrophages were infected with L. enriettii or L. major, then activated by exposure to recombinant murine interferon-gamma or to macrophage activating factor (MAF)-rich media in the presence of lipopolysaccharide. Activation of macrophages in regular (i.e., arginine-containing) culture medium led to complete destruction of the microorganisms within 24 h (L. enriettii) or 48 h (L. major), concomitant with accumulation of nitrites (NO2-) in the culture fluids. When macrophage activation was carried out in L-arg-free medium, however, neither parasite killing nor NO2- production was obtained. A similar inhibition of macrophage leishmanicidal activity and of NO2- release was observed using media treated with arginase (which converts L-arg to urea and ornithine), or supplemented with NG-monomethyl-L-arg or guanidine (which inhibit the conversion of L-arg to nitrogen oxidation products). In all these situations, an excellent correlation between the levels of NO2- production by macrophages and intracellular killing of Leishmania was observed, whereas no strict correlation was detectable between leishmanicidal activity and superoxide production. Intracellular parasite killing by activated macrophages could be prevented by addition of iron salts to the incubation fluids. Incubation of free parasites with NaNO2 at acid pH (which permits the production of nitrous acid) led to immobilisation, multiplication arrest, and morphological degeneration of the microorganisms. Similarly, exposure of infected cells to NaNO2 led to killing of the intracellular parasite without affecting macrophage viability. These experiments strongly suggest that the leishmanicidal effect of activated murine macrophages involves the agency of L-arg-derived nitrogen oxidation products.

Killing of Leishmania Parasites in Activated Murine Macrophages is Based on an L-Arginine-Dependent Process That Produces Nitrogen Derivatives

The influence of nitrite and nitrate on microbial, chemical and sensory parameters of slow dry fermented sausage

The chemistry of nitrite, the properties of meat, and the curing process are covered in this review of the reactions of nitrite in meat. The salts of nitrite are soluble in water and very reactive. Meat contains an enormous variety of chemicals and these chemicals are contained in a complicated morphological muscle structure. When nitrite is added to meat for curing, less than 50% of that added can be analyzed chemically after completion of processing. Nitrite reacts with the myoglobin to form the cured meat color. Nitrite also reacts with the proteins, lipids and carbohydrates in the meat or its additives. Before heating, some of the nitrite of cured beef often turns into nitrate, in some cases up to 40%. Research is being conducted to block the formation of nitrosamines in cured meat

R.G. Cassens

Papers

Reactions of nitrite in meat