| Mutton can release a special odor in cooking, commonly known as"goaty flavour". The odor affected people's mutton consumption in a certain extent. Our country was biggest country of feeding goat and sheep in the world, can produce millions of tons of mutton every year. So, that the material and mechanism of forming mutton smell was deeply studied is very important to the rapid development of sheep industry. Under foreign research methods of volatile substance, the study firstly established determination method of causing mutton smell material, and studied material of causing mutton smell and its influencing factors. At last, the forming mechanism of causing mutton of smell in sheep adipose tissue was preliminary explored. The results were showed in following.1. Research results showed that taking into account the extract concentration in the extract, the feasibility of sample collection and separation of volatile fatty acids operability. The parameters of 100 g adipose tissue sample and 60 min extraction time can meet the research needs of volatile fatty acids of adipose tissue. In GC separation, Polarity GC column and heating rate of 4℃/min can separated volatile fatty acids. Volatile fatty acids including have important role mutton smell were detected. After testing, the repeatability and recovery of the method meet the needs of studying mutton smell.2. By analyzed volatile fatty acids of adipose tissue from pig, cattle and sheep, the results showed that the adipose tissue of pig hasn't contain volatile branched chain fatty acids. The adipose tissue of cattle contained a lot of 3-methylbutyric acid, it's concentration 186.513 mg/kg. At the same time, 4-methyloctanoic acid was detected, it's concentration 7.508 mg/kg, which was lower than sheep adipose tissue. Adipose tissue of sheep has detected pentanoic acid, heptanoic acid, 4-methyloctanoic acid and 4-methylnonanoic acid, their concentration was 12.928 mg/kg, 16.276 mg/kg, 36.169 mg/kg, and 6.174 mg/kg, respectively. Decanoic acid of sheep adipose tissue was more than pig and cattle. 4-methyloctanoic acid and 4-methylnonanoic acid have mutton odor trait. which less than detecting value of this study. Decanoic acid can release very unpleasant odor. So, forming mutton odor, inducing low acceptability of mutton has close relationship of 4-methyloctanoic acid, 4-methylnonanoic acid and decanoic acid.3. By analyzed volatile fatty acids of adipose tissue from strong, middle and low mutton odor. The results showed that the butanoic acid, hexanoic acid, octanoic acid, 4-methyloctanoic acid and decanoic acid of strong mutton odor sample were significantly higher than middle and low mutton odor sample(P<0.05). The change of hexanoic acid, octanoic acid, 4-methyloctanoic acid and decanoic acid among of volatile fatty acids was consistent with mutton odor. The change 4-methylnonanoic acid was not consistent with mutton odor. So, we speculated 4-methyloctanoic acid has important role to forming mutton odor, 4-methylnonanoic acid was helping role. The higher concentration decanoic acid can reduce acceptability of mutton.4. The effects of breed on volatile fatty acids in sheep adipose tissue were researched in this test. The results showed that the concentration of 4-methyloctanoic acid and 4-methylnonanoic acid, which have important role to mutton odor, from small tail Han sheep, Tan sheep and Tong sheep were 20.317 mg/kg,3.546 mg/kg ;14.150 mg/kg,5.597 mg/kg and 12.835 mg/kg , 6.403 mg/kg, respectively. The sort of 4-methyloctanoic acid concentration among three sheep breed is small tail Han sheep > Tan sheep > Tong sheep. The 4-methyloctanoic acid concentration of small tail Han sheep is 1.43 and 1.57 fold of Tan sheep and Tong sheep. Tan sheep was same with Tong sheep. The change date was same with experience of life people. Among sheep breeds, genetic factor can affected mutton odor forming.5. The effects of area on volatile fatty acids in sheep adipose tissue were researched in this test. The results showed that the concentration of octanoic acid, 4-methyloctanoic acid, decanoic acid of Small Tail Han sheep from Henan were 52.823 mg/kg,35.745 mg/kg and 118.217 mg/kg, which more than 43.942mg/kg,20.317 mg/kg and 51.949 mg/kg from Ningxia. The concentration of 4-methyloctanoic acid of Henan was 1.75 fold of Ningxia. On 4-methylnonanoic acid, two area were same. The concentration of decanoic acid of Henan was 2.27 fold of Ningxia. The date indicated mutton odor of Henan was stronger than Ningxia, which was same with experience of people life. The phenomenon showed region has significantly effects to mutton odor.6. The AT-MT gene sequence of fatty acid synthase from sheep was cloned and analyzed. The results showed that the gene homology between sheep and goat was 98.3%, followed by cattle, 94.8%, then followed by pigs, and rats, respectively, 85.0%, 83.7% and 80.4%. In the nucleic acids, the AT-MT gene of sheep and goat has eight significant differences comparing with other animal. In the amino acid sequence, the AT-MT gene of sheep and goat has six significant differences, in which the difference of 244 was caused by changed of amino acid nature. In the secondary structure distribution, the spiral and folded structure of sheep and goats AT-MT gene amino acid sequence formed have specific structure comparing with other species. |
