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Variation in the Lipid Content and Fatty Acid Composition of Three Bovine Muscles as Affected by Different Methods of Extraction¹

University of Arizona, Tucson

Abstract

Ten half-sib Hereford steers were utilized to study the variability in the intramuscular lipid content and fatty acid composition of three muscles (longissimus dorsi, triceps brachii and semimembranosus). Comparisons were made between lipid yields by ether extract and chloroform-methanol methods of extraction. Large differences in lipid content of the muscles were observed: however, these differences were significant (P<.05) only when the chloroform-methanol method of extraction was employed. In addition, a significant (P<.05) extraction method x muscle interaction was observed. When the data were expressed on a wet tissue basis, none of the differences in lipid yields due to the method of extraction was statistically significant.

Relationships were determined between all possible combinations of the data. In general, marbling score was moderately correlated with chemical fat (ranging from 0.62 to 0.79) on an over-all muscle basis. On an individual basis, marbling scores determined at the exposed surface of the l. dorsiwere highly related to muscle lipid content of both the LD and TB muscles regardless of method of extraction. The magnitude of the relationships indicated that marbling, as appraised visually, is a practical indicator of total extractable muscle lipid.

Differences were observed in certain fatty acid levels of the lipid extracted by the two procedures. Only trace amounts of C15 were observed in the lipid extracted by ether for the LD and SM muscles, where measurable amounts were determined for chloroform-methanol extract. Only the differences in the levels of C16 and C18:2 in the two extracts were statistically significant (P<.01).

Large differences between the muscles were observed in most of the major fatty acids. In general, the LD muscle contained significantly (P<.01) more C16 and C18 than the other two muscles, but significantly (P<.01) less C16:1 and C18:2. The data also revealed that the LD muscle was lower (P<.01) in oleic acid content than the SM, but significantly (P<.05) higher than the TB muscle. Furthermore, the LD intramuscular lipid possessed from 2 to 3% less (P<.01) total unsaturated fatty acids than either of the other two muscles.

¹ Arizona Agricultural Experiment Station Technical Paper 1266.