Alteration of fatty acid profile

Issues of dietary fat in humans have gained tremendous attention in recent years. Recommendations have been made to reduce total fat intake and to modify the type of fat consumed (American Heart Association, 1985). In general, an increased intake of monounsaturated and polyunsaturated fatty acids, and a decreased consumption of saturated fatty acids have 

Supplementation of meat animal diets with fish oil, and fish meal have been reported the degree to which an undesirable fishy flavor occurs depends on which of these is fed. The occurrence of a fishy flavor in bacon was related to the content of long-chain PUFA resulting from excessive supplementation of fish products in the diets of swine (Coxon et al., 1986). Miller et al. (1969) reported a dose-dependent response of long-chain PUFA, especially C20 5 and C22 5, in broiler breast and thigh with supplementation of menhaden fish oil. Undesirable fishy flavors were noted in tissues from birds receiving high levels of supplementation. The authors noted that supplementation of birds for 4 weeks, with subsequent withdrawal for the same time period, resulted in acceptable sensory scores. However, the fatty acid profile of meat from these birds also returned to that of controls. Miller et al. (1967) reported that specific n-3 fatty acids, C18 4, C20 4, C20 5 and C22 5, were associated with the unacceptable flavor of fish oil-supplemented broiler meat. Crawford and Kretsch (1976) identified 21 different volatile products associated with fishy flavor in meat from turkeys supplemented with tuna oil. 

There have been attempts to remove or quench undesirable flavors associated with fish oil-supplemented meat. Miller et al. (1967) fed refined menhaden fish oil in the form of both triglyceride, and ethyl esters of the fatty acids, to determine if there was any difference in the development of fishy flavors. The authors reported no differences, and broiler meat obtained from fish oil-supplemented birds was less acceptable than birds fed control fat (tallow or corn oil). Crawford et al. (1975) further supplemented fish oil diets with a-tocopheryl acetate. Meat from vitamin E-supplemented birds demonstrated a greatly reduced fishy flavor the fatty acid profile was, however, unaffected by vitamin E treatment. 

The supplementation of animals with specific fats for the purpose of altering fatty acid profile, specifically long-chain PUFAs, of animal food products is feasible. The two greatest problems appear to be the increased susceptibility of supplemented products to lipid oxidation, and undesirable flavors associated with dietary fat source. Each of these problems may be overcome in part by dietary supplementation of antioxidants and choosing lipid supplements of high quality, respectively. 

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Table 2.1 Patents on oilseed transformation and alteration of fatty acid profiles. 

Food from supplement-fed animals is reviewed in chapter 8 by Cameron Faustman of the Department of Animal Science at the University of Connecticut, USA. The use of feed supplements is a growing area of research for improvement of the quality of meat. Supplementation with vitamin E, carotenoids and vitamin C is addressed. Cholesterol reduction, alteration of fatty acid profiles and competitive exclusion are also covered. 

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