OXIDATION OF LIPIDS IN SARCOPLASMIC RETICULUM OF MUSCLES FROM PASTURE‐ AND GRAIN‐FED CATTLE WITH OR WITHOUT VITAMIN E SUPPLEMENTATION

Abstract

ABSTRACT The effect of different α‐tocopherol contents in sarcoplasmic reticulum (SR) membranes on lipid oxidation was investigated. Muscle membranes contain high contents of polyunsaturated fatty acids that are very susceptible to oxidation during chilled or frozen storage. SR was prepared from M. longissimus dorsi, M. semimembranosus and M. gluteus medius muscles of pasture‐ and grain‐fed steers supplemented with vitamin E (0, 500 or 2500 IU α‐tocopheryl acetate) for 105 ‐132 days. Vitamin E supplementation increased the α‐tocopherol concentration in SR of grain‐fed cattle but did not change that of pasture‐fed cattle. SR from pasture‐fed beef had more linolenic and less linoleic acid than that of grain‐fed meat and, compared with the other treatment groups, SR of control grain‐fed cattle was significantly more prone to lipid oxidation, corresponding with its lower α‐tocopherol content. Thus, α‐tocopherol content appears to play a major role in determining the extent of lipid oxidation in muscle membranes, especially in those from pasture‐fed beef that contained more polyunsaturated fatty acids.