关键词: 饲养方式, 苏尼特羊, 挥发性风味物质, 脂肪酸, 代谢调控基因

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

Key words: feeding patterns, Sunit sheep, volatile flavor compounds, fatty acids, metabolism-related genes