| Abstrakt: |
The present study was designed to assess the balance between antioxidant and pro-oxidant components and the oxidative stability of beef from cattle fed exclusively grazed pasture (P) or a barley-based concentrate offered indoors (C) for 11 months, or fed grass silage indoors for a 5-month winter period followed, for the remaining 6-month summer period, by grazed pasture (SiP) or by grazed pasture plus concentrate at 50% of the diet DM (SiPC). Muscle pro-oxidant and antioxidant components were determined by measuring fatty acid and of a-tocopherol concentration of LM, respectively. Lipid oxidation and color stability were monitored in ground LM, packaged in a high oxygen modified atmosphere, over 11 days of refrigerated storage. Vitamin E concentration decreased (P < 0.0005) with increaseing proportion of concentrate in the diet (2.59, 2.45, 1.76 and 1.15 µg/g for P, SiP, SiPC and C, respectively). A higher proportion of PUFA was found in LM from cattle in the P, SiP and SiPC groups compared to animals from the C group (9.62%, 11.04%, 8.96% and 6.94%, respectively; P < 0.0005). A higher concentration of highly peroxidizable PUFA (HP-PUFA) was found in LM from heifers in the P, SiP and SiPC groups compared to animals in the C group (0.84, 0.85, 0.87 and 0.65 mg/g of muscle, respectively; P = 0.02). Dietary treatment affected lipid oxidation (P < 0.0005), with higher TBARS values in beef from heifers in the SiPC group compared to those of the P, SiP and C groups. Dietary treatment affected myoglobin oxidation (P = 0.002) during storage with greater metmyoglobin accumulation in beef from animals receiving concentrate (C and SiPC treatments) compared to cattle in the P and SiP groups. Consequently, feeding concentrate impaired meat color stability over storage duration, with higher H* values (P < 0.0005) in meat from heifers in the SiPC and C groups compared to cattle from the P and SiP groups. The results of the present study confirm a positive effect of grass-based feeding systems on meat color stability compared to concentrate-based dietary strategies. It appears that vitamin E in muscle does not alone explain the resistance of meat to oxidative deterioration, as a clear interaction with HP-PUFA exists. [ABSTRACT FROM AUTHOR] |
