Poultry rancidity

Gray, J.l. and Pearson, A.M. 1987. Rancidity and warmed-over flavor. In Advances in Meat Research, Vol. 3 Restructured Meat and Poultry Products (A.M. Pearson and T.R. Dutson, eds.) pp. 221-269. Van Noslrand-Reinhold, New York. 

Including full-fat soybeans in poultry diets reduces aerial dust levels, and is likely to benefit the health of animals and workers in buildings. Because of possible rancidity problems, diets based on full-fat soybean should be used immediately and not stored. Otherwise, an approved antioxidant should be added to the dietary mixture. 

Tappel (5) showed that ascorbic acid acts synergistically with food antioxidants and because of the great increase in eflFectiveness resulting from a small amount of ascorbic acid, he suggested mixtures would be eflFective in preventing oxidative rancidity in meats, poultry, and fish. 

Products and Uses Wheat germ oil is a rich source of this fat-soluble compound. It is found in bacon, fats (rendered animal), pork fat (rendered), and poultry. Useful as an antioxidant (added to oil-containing food to prevent it from getting rancid), dietary supplement, nutrient, and preservative. 

In addition to these inherent characteristics of the fat itself, contact of the fat in meat with an aqueous solution containing surface-active substances, accelerators and inhibitors of rancidity, creates a very different situation from conditions which exist in a container of rendered lard. The author has noted on a number of occasions that the keeping time of fat rendered from pork tissues did not correlate with rancidity development in the ground meat. Schreiber et al. (1947) reported that the stability of fat, as measured by accelerated tests on the extracted fat from fresh birds, was not a good indication of the stability of poultry fat in situ during freezer storage. 

In general, the oxidation rate of pure dry oils was approximately doubled by a 10 C. (18° F.) rise in temperature in the absence of catalysts. In the presence of light or metal catalysts the coefficient was much smaller. There is no published information on the temperature coefficient of the coupled reaction between hemoglobin and unsaturated fat. Numerous more recent studies on frozen meats and poultry have emphasized the importance of low storage temperatures in retarding rancidity (Cook and White, 1939, 1941 Ramsbottom, 1947 Atkinson et al., 1947 Hall et al., 1949 Klose et al., 1950 Palmer et al., 1953). 

The hpid content of cereal grains varies with spedes. Wheat, barley, rye and rice contain 10 30 g/kg DM, sorghum 30-40 g/kg DM and maize and oats 40-60 g/kg DM.The embryo, or germ, contains more oil than the endosperm in wheat, for example, the embryo has 100-170 g/kg DM of oil, while the endosperm contains only 10-20 g/kg DM.The embryo of rice is exceptionally rich in oil, containing as much as 350 g/kg DM. Cereal oils are imsaturated, the main adds being linoleic and oleic because of this they tend to become rancid quickly and also produce a soft body fat in pigs and poultry. 

The poultry study of Marusich et al, (1975) is one of the most comprehensive published to date. Data are presented for different vitamin E supplements fed for varying time periods to both chickens and turkeys. Turkeys required much higher levels of supplemental vitamin E than broilers for obtaining similar low TBA values of meat. The authors proposed that 0.50 mg a-tocopherol/100 g tissue was necessary to delay the onset of rancidity in broiler breast muscle. Results of the study supported a strong inverse correlation between the level of dietary supplementation and rancidity development in turkey or chicken breast. 

Heme (Fe +) and hemin (Fe +) proteins are widely distributed in food. Lipid peroxidation in animal tissue is accelerated by hemoglobin, myoglobin and cytochrome C. These reactions are often responsible for rancidity or aroma defects occurring during storage of fish, poultry and cooked meat. In plant food the most important heme(in) proteins are peroxidase and catalase. Cytochrome P450 is a particularly powerful catalyst for lipid peroxidation, although it is not yet clear to what extent the compound affects food shelf life in situ . 

The volatile components of raw chicken breast muscle include mainly carbonyls, thiols, sulfides and alcohols. The major volatile components of fried chicken are similar to volatiles of the meat of farm animals (e.g. common aldehydes, ketones, hydrocarbons and other compounds). Sulfur-containing compounds generated during thermal processing are also important for the flavour of chicken meat. Saturated and unsaturated aldehydes are very important - these are produced easily by oxidation of lipids and manifest negatively in stored poultry meat, which quickly becomes rancid. Feed plays an important role in imparting certain flavour characteristics to poultry meat. 

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