两种饲养方式下苏尼特羊肉中鲜味物质含量及相关调控基因表达量

为研究不同饲养方式下羊肉的风味特性，以舍饲、放牧两种方式饲养的12 月龄苏尼特羊股二头肌、背最长肌、臂三头肌3 个部位为实验材料，分别测定味觉指标、鲜味物质含量以及相关调控基因表达量并进行比较分析。结果表明：放牧饲养羊肉鲜味和咸味高于舍饲饲养，苦味和涩味低于舍饲饲养；放牧饲养羊肉中的肌苷酸（inosinic acid，IMP）和肌苷（inosine，INO）含量显著高于舍饲饲养（P＜0.05）；放牧饲养羊背最长肌的腺苷一磷酸脱氨酶（adenosine monophosphate deaminase 1，AMPD1）基因表达量显著高于舍饲饲养（P＜0.05），股二头肌的腺苷酸琥珀酸裂解酶（adenylosuccinate lyase，ADSL）和次黄嘌呤核苷酸环水解酶（aminoimidazole carboxamide ribonucleotide transformylase，ATIC）基因表达量显著高于舍饲饲养（P＜0.05）；放牧饲养羊肉AMPD1表达量与ADSL表达量之间呈极显著正相关（P＜0.01）；通过分析鲜味物质含量与调控基因表达量的相关性，发现放牧饲养羊肉IMP含量与AMPD1基因表达量之间呈极显著正相关（P＜0.01），与ATIC基因表达量之间呈显著正相关（P＜0.05）；舍饲饲养羊肉IMP含量与ATIC基因表达量之间呈显著正相关（P＜0.05）。综上，当鲜味物质调控基因的表达量高时，肉中的鲜味物质含量也随之提高。

Effects of Two Different Feeding Patterns on Umami Substances and Expression of Related Genes in Sunit Sheep Meat

The objective of this study was to investigate the difference in taste characteristics, umami substances and the expression of umami-related genes in Longissimus dorsi, Biceps femoris and Triceps brachii muscles from Sunit sheep subjected to two different feeding patterns (grazing and stall feeding). Sunit sheep were slaughtered at the age of 12 months for the collection of muscle samples. The results showed that the umami and saltiness of meat from grazed sheep were higher than those of stall-fed sheep, while the bitterness and astringency were lower than those of the latter. The contents of inosine monophosphate (IMP) and inosine (INO) as umami substances in meat from grazed sheep were significantly higher than in meat from stall-fed sheep (P < 0.05). The expression of adenosine monophosphate deaminase 1 (AMPD1) gene in Longissimus dorsi of grazed sheep were significantly higher than that in stall-fed sheep (P < 0.05), and there was also a significant increase in the expression of adenylosuccinate lyase (ADSL) and aminoimidazole carboxamide ribonucleotide transformylase (ATIC) gene in Biceps femoris (P < 0.05). For grazed sheep, a significant positive correlation was found between the expression of AMPD1 and ADSL (P < 0.01). Correlation analysis showed that IMP content was positively correlated with the expression of AMPD1 highly significantly (P < 0.01) in grazed sheep and with the expression of ATIC significantly (P < 0.05) in both grazed and stall-fed sheep. Finally, we concluded that when the expression of umami-related genes was increased, there was a concomitant increase in the content of umami substances.