INFLUENCE OF SEX AND POSTMORTEM AGING ON INTRAMUSCULAR AND SUBCUTANEOUS BOVINE LIPIDS

SUMMARY –Fifteen wholesale beef ribs from an equal number (5) of half-sib bulls, steers and heifers were used to study the changes in subcutaneous (SQ) and longissimus dorsi intramuscular (IM) lipids at 2, 7, 14 and 21 days post-mortem (PM). The progressively increasing free fatty acid (FFA) levels observed in both depots with time PM were paralleled by fatty acid composition changes. During the aging period the content of C14:0 in the FFA fraction decreased from 11.7–5.8%; the level of C18:1 increased from 42.6–49.7%. Cholesterol and phospholipid levels did not change with PM aging. PM aging had no effect on the composition of the IM phospholipid class, suggesting that autoxidation does not readily occur during aging of fresh beef ribs. Fatty acid composition of the bull IM lipid fractions frequently differed from the fatty acid composition of these fractions in heifers or steers; the latter two sexes had similar fatty acid compositions in their IM lipid fractions. In the SQ triglyceride fraction, heifers had higher and lower levels of C18:1 and C16:0, respectively, when compared to both bulls and steers. Traces of C22:6 were present in the IM free fatty acid fraction of heifers, whereas 3.2 and 4.1% were present in the FFA of steers and bulls, respectively. Rib steaks from heifers had significantly (P < .05) higher sensory panel scores for aroma and lower IM and SQ levels of FFA when compared to bulls. A significant (P < .01) correlation of -0.49 was obtained between aroma score and IM levels of FFA.