| Feeding high concentrates diet was the main finishing strategy for sheep in Inner Mongolia currently.Long-term intake of high concentrates diet would likely to cause oxidative stress in sheep,which may affect the endogenous antioxidative capacity of sheep.Researchers made great efforts to relieve the oxidative damage to sheep by adding natural plant antioxidants.The meat quality of mutton may also undergo different changes after long-term frozen storage with different feeding systems.In this study,the effects of feeding systems on the quality of lamb were investigated after 150 days of frozen storage,aimed to provide suitable guidance for protection of the nutritional quality and processing properties of mutton.The Mongolian sheep were subject to three different feeding systems,named pasture feeding(PF),high concentrate diet feeing(HC)and adding plant additives with high concentrate diet(PA)respectively.The lambs in three groups had a similar average live weight of 50 ± 5 kg at slaughter.The longissimus dorsi muscles were sampled from the left side of the carcass for further detection.The results were showed as follows.1.The pH value,color and crude fat content of the PA group were significantly higher than those of the other two groups(P<0.05),the crude protein content in the PA group was significantly lower than that in the other two groups(P<0.05).ash content in PF group was significantly higher than that in the other two groups(P<0.05),the amino acid content in the HC group was significantly lower than that in the other two groups(P<0.05).The C18:2content in PA group and the C18:3 content in PF group were the highest among the three groups,reached 10.66% and 2.02% respectively.2.Protein oxidation of mutton in all three groups was significantly increased with the increase of frozen storage time(P<0.05).Supplementation of plant additive significantly reduced the carbonyl content and increased the total sulfhydryl content of mutton,and inhibited protein oxidation through whole frozen storage period.The antioxidant enzyme activity and T-AOC value of mutton in three groups were also decreased with the prolongation of frozen storage time.CAT activity in PF group was significantly increased by 1.82 times and 0.43 times(P<0.05)compared with HC and PA groups on the 150 th day,and SOD activity in PA group was significantly increased by 38.5% compared with PF group on the 150 th day(P<0.05).The TBARs value of the HC group was higher in the later period of frozen storage time,indicated that feeding high concentrates diet delayed the fat oxidation of frozen stored mutton.3.With the extension of frozen storage time,the protein solubility of mutton in the HC group showed a trend of decrease and was the lowest value among the three groups(P<0.05).The gel strength,water holding capacity and emulsification stability of mutton gels in HC group was significantly lower than the other two groups(P<0.05).The texture properties of mutton gels in the three groups were significantly decreased with the extension of freezing storage time(P<0.05).At the initial stage of frozen storage,the gel network structure of the three groups was smooth and evenly distributed.At the end of storage,the gel network structure of the HC group became rougher.In conclusion,feeding strategy had significant effects on physicochemical properties,antioxidant capacity and protein functional properties of lamb after frozen storage.The antioxidant capacity and protein functional properties of high concentrates finished mutton decreased during frozen storage,which resulted in poor meat quality.Pasture feeding and the supplementation of antioxidative plant additive could improve the decrease of endogenous antioxidant of mutton caused by high concentrates diet feeding and protect the protein functional properties of mutton in frozen storage. |
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