饲养方式对苏尼特羊肉挥发性风味成分和脂肪酸组成的影响

Effects of Feeding Patterns on Volatile Flavor Components and Fatty Acid Composition of Sunit Sheep Meat

选择舍饲、放牧2 种饲养方式下12 只12 月龄的苏尼特羊背最长肌为实验材料,采用气相色谱-质谱(gaschromatography-mass spectrometry,GC-MS)联用技术测定挥发性风味物质和脂肪酸成分,实时荧光定量聚合酶链式反应方法测定脂肪代谢相关调控基因表达量,探究饲养方式对苏尼特羊肉风味和脂肪酸组成的影响。结果表明:羊肉中主要挥发性化合物为己醛、壬醛、1-辛烯-3-醇和2,3-辛二酮,其中舍饲羊中壬醛含量显著高于放牧羊(P<0.05),1-辛烯-3-醇和2,3-辛二酮含量显著低于放牧羊(P<0.05);脂肪酸中棕榈酸、硬脂酸和油酸占比较大,放牧羊肉中的硬脂酸含量显著高于舍饲组(P<0.05);放牧组脂肪氧合酶基因(lipoxygenase,LOX)表达量显著高于舍饲组(P<0.05),乙酰辅酶A羧化酶基因(acetyl-CoA carboxylase,ACC)和过氧化物酶体增殖物激活受体γ基因(peroxisome proliferator-activated receptor γ,PPARγ)表达量高于舍饲组(P>0.05)。整体上,由于放牧羊中PPARγ和ACC基因的较高表达量,使得羊肉中合成并沉积了更多的脂肪酸,并激活了LOX基因的高表达,促使脂肪酸氧化生成大量醛、醇类挥发性物质,赋予了放牧羊肉优异的风味品质。

The volatile flavor and fatty acid components of the Longissimus dorsi of twelve 12-month-old Sunit sheepsubjected to two feeding patterns (grazing and forage supplemented with a concentrate mixture) were analyzed by gaschromatography-mass spectrometry (GC-MS), and then the expression levels of lipid metabolism-related genes weredetermined by quantitative real-time polymerase chain reaction (qRT-PCR) in order to explore the effect of feeding methodson the volatile flavor components and fatty acid contents of mutton. The results showed that hexanal, nonanal, 1-octen-3-oland 2,3-octanedione were the main volatile compounds in Sunit sheep meat, and nonanal content in the meat of forageplus concentrate-fed sheep was significantly higher than in the meat of grazed sheep (P < 0.05), but the opposite was truefor the contents of 1-octen-3-ol and 2,3-octanedione (P < 0.05). The contents of C16:0, C18:0 and C18:1 n9c were higher thanthose of the other detected fatty acids, and C18:0 was significantly more abundant in the meat of grazed sheep than in forageplus concentrate-fed sheep (P < 0.05). The expression level of lipoxygenase (LOX) gene in grazed sheep was significantlyhigher than in forage plus concentrate-fed sheep (P < 0.05), and the expression levels of acetyl-CoA carboxylase (ACC) andperoxisome proliferator-activated receptor (PPARγ) genes were higher but not significantly than in forage plus concentratefedsheep (P > 0.05). On the whole, the higher expression levels of PPARγ and ACC genes led to the synthesis and depositionof more fatty acids in the meat of grazed sheep and consequently activated expression of LOX, thereby promoting theoxidation of fatty acids to produce a large amount of volatiles like aldehydes and alcohols imparting a better flavor quality tothe meat of grazed sheep.