Page 367 - Natural Antioxidants, Applications in Foods of Animal Origin

346 Natural Antioxidants: Applications in Foods of Animal Origin
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9.2.1.1 MEAT COMPOSITION

Two factors greatly influence lipid oxidation in raw meat are fat content and
fatty acid composition. According to Min et al. (2008), the composition of
fat is more important than the amount of fat in meat, because the suscepti-
bility of muscle lipid to lipid peroxidation depends upon the degree of poly-
unsaturation in fatty acids. Unsaturated lipids are generally more susceptible
to lipid oxidation because hydrogen atoms can be more easily abstracted
from polyunsaturated fats than saturated fats (Kanner et al., 1987; Gong et
al., 2010). In fact, fats containing high proportions of linoleic or linolenic
acids are more prone to oxidation than oils high in oleic acid. Thus one nutri-
tional effect of oxidation is to reduce the essential fatty acid content of fats.
It is thought that the polyunsaturated fatty acids from polar phospholipids
rather than triglycerides are responsible for the initial development of lipid
oxidation in muscle foods (Renerre & Ladabie, 1993). During the course of
oxidation, the total unsaturated fatty acid content of lipids decreases with a
concurrent increase in the amount of primary and secondary oxidation prod-
ucts such as lipid hydroperoxides, aldehydes, ketones, hydrocarbons, and
alcohols. Therefore, rancidity in food occurs when unsaturated fatty acids
decompose into volatile compounds. Increasing levels of unsaturated fatty
acids in meat increase lipid oxidation rates (and rancidity) and thus decrease
shelf life of the muscle foods. The autoxidation rate greatly depends on the
rate of fatty acid or acylglycerol alkyl radical formation, and the radical
formation rate depends mainly on the types of fatty acid or acylglycerol.
Consequently, the susceptibility of meat to lipid peroxidation varies
among meats from different animal species and muscles from the same
animal (Min et al., 2008). There are numerous studies showing that both
the species and fat location significantly affects fatty acid composition of
the meat. Cava et al. (2003) found that muscles with higher proportions of
phospholipids also presented higher amounts of polyunsaturated fatty acids.
In the same way, Domínguez et al. (2015) also observed that Psoas major
muscle (oxidative muscle) had significantly higher amounts of polyunsatu-
rated fatty acids than Longissimus dorsi (glycolytic muscle). Differences
in fatty acid composition between oxidative and glycolytic muscles might
be due to a higher number of cellular and sub-cellular membranes, and the
difference in the ratio of mitochondria to other membranes between oxida-
tive and glycolytic muscles. Therefore, the different polyunsaturated fatty
acid amounts making lipids from oxidative muscles more susceptible to
oxidative processes than those from the glycolytic muscles.