Membrane lipid oxidation and proteolytic activity in thigh muscles from broilers fed different diets

Thr effects of diets differing in their level of unsaturation and their con tents of natural antioxidants and prooxidants on lipid oxidation was measur ed in microsomal membranes of the thigh muscles of broilers by three proces ses: enzymatic, nonenzymatic and sarcoplasmic protein oxidation. Lysosomal cysteine proteinase activities were determined to assess the influence of t he different diets on the enzymatic proteolysis of meat. Statistically sign ificant differences were found in the enzymatic reaction for 72 h of incuba tion at 4 degrees C in relation to the effect of both diet and antioxidant supplementation. Meat from animals fed an unsaturated diet containing sunfl ower oil gave the highest level of oxidation. Broilers fed supplemental ant ioxidants, especially alpha-tocopherol, had lower degrees of oxidation than those fed the basal diet. An unexpected result of the prooxidant diet stud y was a higher degree of oxidation in samples from animals deprived of iron and copper. Cysteine proteinase activities were favoured by vitamin E (alp ha-tocopherol) supplementation and the absence of copper. (C) 1999 Elsevier Science Ltd. All rights reserved.