Lipid peroxidation (LPO) alongside with other processes of post mortem metabolism is decisive for quality formation of meat products. Phenomena encountered in meat raw materials as a result of LPO can be summarized under three headings: 1 -those affecting safety (formation of malonic dialdehyde, fatty acids peroxides, oxidized cholesterol etc); 2 -those affecting biological value (lowering the content of non-replaceable fatty acids and vitamins, oxidative amino-acid decomposition, decrease of protein digestibility); 3 -those affecting technological quality parameters (decrease of protein solubility, colour and fl avour changes, as well as appearance of a typical odour).
MEAT COLOUR AND ITS NATUREAmong the meat quality parameters affecting its salability, colour plays a special role. The colour of meat depends on the content and physical and chemical changes of hemoglobin and myoglobin (Mb) -complex proteins of hemoprotein group contained
ROLE OF PEROXIDATION AND HEME CATALYSIS IN COLORATION OF RAW MEAT
ABSTRACTIt is known, that lipid peroxidation is one of the main factors limiting the quality and acceptability of meat and other animal tissues. The current data concerning connection of heme and peroxidation were summarized and analysed here. The muscle food compounds that are most infl uenced by oxidative processes include unsaturated fatty acids of lipids, amino acids of proteins and heme groups of pigments. Heme proteins and particularly myoglobin are abundant in muscle tissues. Meat colour is primarily infl uenced by the concentration and chemical state of heme pigments, myoglobin and hemoglobin. Oxygenated myoglobin oxidized to the brown metmyoglobin form and its accumulation is highly correlated with progress of lipid peroxidation. Heme proteins such as hemoglobin or myoglobin accelerate the decomposition of hydroperoxides to free radicals. Metmyoglobin possesses «pseudoperoxidase» activity and catalyzes the oxidation of various compounds following the reaction with hydrogen peroxide. The reaction between hydrogen peroxide and metmyoglobin results in the formation of two active hypervalent myoglobin species, perferrylmyoglobin (•MbFe lV =O) and ferrylmyoglobin (MbFe lV =O), which participate in lipid oxidation catalysis. Both MbFe lV =O and •MbFe lV =O are deactivated in the presence of reducing agents, whose nature determines the overall effect of the pseudoperoxidase cycle. Hypothesis can be put forward that loss of cellular antioxidants might precede the rise of peroxidase-like activity, thus being a sign of incipient discoloration of meats and muscle components of foods.
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