【作者】 陈静；

【导师】 高爱武；

【作者基本信息】 内蒙古农业大学 ， 农业硕士（专业学位）， 2021， 硕士

【摘要】 目前,高精料育肥是内蒙古地区肉羊主要的养殖方式,长期采食高精料容易导致肉羊机体氧化应激,可能对肉羊内源性抗氧化能力产生影响,因此许多研究者试图通过添加抗氧化剂缓减肉羊机体的氧化应激。在饲养方式存在差异时,羊肉经过长期的冷冻保藏后肉品质也会产生不同的变化。本文以不同育肥方式生产的羊肉为试验对象,研究饲养方式对宰后冻藏羊肉品质的影响,旨在为寻求适宜的羊肉生产方式,最大可能保护羊肉营养品质和加工性能提供理论指导。分别选择天然放牧绵羊(pasture feeding,PF)、高精料育肥绵羊(high concentrate,HC)和补饲中草药抗氧化剂的高精料育肥绵羊(plant additive,PA)各5只,屠宰后平均活体重为50±5kg,于胴体左侧取背最长肌样品进行分析。研究结果如下:1.PA组的pH值、色泽和粗脂肪含量显著高于其他两组(P<0.05),粗蛋白含量显著低于其他两组(P<0.05);PF组的灰分含量显著高于其他两组(P<0.05);HC组的必需氨基酸含量(EAA,essential amino acids)显著低于其他两组(P<0.05);三组背最长肌共测得13种饱和脂肪酸(saturated fatty acid,SFA)、9种单不饱和脂肪酸(monounsaturated fatty acid,MUFA)和7种单不饱和脂肪酸(polyunsaturated fatty acid,PUFA),PA组的C18:2含量和PF组的C18:3含量分别为三组中的最高值,达到10.66%和2.02%。2.三组绵羊肉的蛋白质氧化随冻藏时间的延长显著加剧(P<0.05),补饲中草药抗氧化剂可以显著降低宰后羊肉的羰基含量,提高总巯基含量,抑制蛋白质氧化;三组绵羊肉的抗氧化酶活性及总抗氧化能力(total antioxidant capacity,T-AOC)随冻藏时间的延长出现了不同程度的降低,PF组在第150d时的过氧化氢酶活性(catalase,CAT)相比于HC组和PA组分别显著高了1.82倍和0.43倍(P<0.05),PA组在第150d时的超氧化物歧化酶活性(superoxide dismutase,SOD)比PF组显著高了38.5%(P<0.05);HC组绵羊肉在冻藏后期呈现较高的硫代巴比妥酸值(thiobarbituric acid value,TBARs),说明饲喂高精料加剧了绵羊肉的脂肪氧化。3.随着冻藏时间的延长,HC组绵羊肉的蛋白溶解度呈现持续下降的趋势,且在三组中处于最低值(P<0.05);三组羊肉凝胶的凝胶强度、保水性、乳化稳定性均随着冻藏时间的延长显著下降(P<0.05),且HC组显著低于其他两组(P<0.05);三组羊肉凝胶的质构特性均随着冻藏时间的延长而显著下降(P<0.05),HC组凝胶在前两个冻藏期的内聚性和回复性显著高于其他两组(P<0.05);在冻藏初期,三组凝胶网络结构光滑且分布均匀,冻藏结束时,三组凝胶网络结构变差,HC组的更为粗糙。综上所述,饲养方式对宰后羊肉理化特性、抗氧化能力以及蛋白功能特性有显著影响。高精料育肥的羊肉在冻藏期间抗氧化能力及蛋白功能特性下降,导致肉质变差。天然放牧或补饲中草药抗氧化剂可改善因高精料育肥造成的羊肉内源抗氧化性下降问题,同时对羊肉后续冻藏中的蛋白功能特性有提高作用。更多还原

【Abstract】 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.更多还原