| The Rong-chang pork which were cut into lcm strips were baked at 180℃for 15min, 30min,40min,until the core temperature were reached at 60℃,80℃,90℃.The changes of flavor precursors and the physical and chemical indicators were studied in processing.In this paper the changes of the aroma compounds in processing were also studied. In addition, the difference of the overall flavor between the samples after processing were distinguished based on the electronic nose. The flavors in processing and the differences between the methods of the simultaneous distillation extraction and solid phase micro extraction were discussed. using the statistical method of Partial least squares regression. It has some significance to improve the characteristics of traditional food processing technology, and also it provide some of the key research ideas and methods for similar studies. In this paper, the results showed that:1. The low boiling point compounds were better extraction by the method of SPME, while the high boiling point compounds were better extraction by the method of SDE. It requires a long period of heat treatment in simultaneous distillation extraction process, so it can lead to the degradation of flavor compounds, at the same time, it can produce other compounds. The flavor compounds extracted by SDE tend to deviate from the essence of the flavor extracts, which cause some false flavor generation. Summarily, the volatile flavor compounds were better analyzed by the two methods which were complement each other.2. The changes of the physical and chemical indicators:The center temperature of samples reached at 60℃,80℃and 90℃when baked at 180℃for 15min,30min,40min. The moisture content reached at 59.24%,43.77%,30.82%. The pH which reached at 5.75,5.78 and 5.84 did not change significantly. The TBA was first increased and then decreased for the 1.67,2.09 and 1.18, respectively. The crude fat contents were 13.73%,11.71% and 11.41% and the crude protein content were 56.09%,43.22% and 35.61%.3. The changes of precursor flavor in processing:(1) Reducing Sugar:the reducing sugar content decreased gradually With the core temperature continuous rise in processing. And when it were 30min-40min the reducing sugar content decreased slowly.(2) Thiamine:In the initial stage of processing the heating time is not very long and the heating temperature is not very high. The content of thiamine were decreased slowly. With the heating time is longer and the heating temperature is higher he content of thiamine were decreased significant.(3) Free amino acids:The volume of the seventeen minutes amino acids wad gradually reduced. The free amino acids which were significant changed in processing include methionine, cysteine, proline, hydroxyproline, threonine, serine and lysine. The thermal degradation of these amino acids led to the pyrazine compounds and Pyridines compounds and sulfur compounds a significant increase in samples.(4) Fatty acid composition:The content of saturated fatty acids and monounsaturated fatty acids which were the composition of triglyceride did not change significantly. But the content of Polyunsaturated fatty acids which were the Composition of triglyceride changed significantly. The phospholipid were degraded partly in processing. The content of saturated fatty acids and monounsaturated fatty acids which were the composition of phospholipid did not change significantly while the C16:1 fatty acids which were the composition of monounsaturated fatty acids changed significantly. The general trend of free fatty acids is that the SFA was significantly higher and the MUFA did not change significantly but the PUFA were significantly reduced. The PUFA decreased more significantly especially when baking 40min.4. The changes of the major categories of the flavor compounds in processing:the Percentage of aldehydes has been the highest volatile flavor compounds. But the percentage of 2-crotonaldehyde,3-methyl butyraldehyde and benzaldehyde significant increase. In addition, the content of some compounds increased significantly in the higher level of processing samples. These compounds which have the greatest contribution to the flavor of baked Rong-chang pork include Furan and its derivatives, pyrazine compounds, sulfur compounds and lactone compounds. Other compounds Such as alcohols, ketones, acids, esters and aromatic compounds have a high threshold. Therefore, Although their concentrations is higher but the contribution is very small. And these compounds changed Irregularly in processing.5. The main flavor compounds after processing:The samples after processing were distinguished by electronic nose found that the informations of the overall flavor abou samples E(baked 30min) and F(baked 40min) were not very different. But it has a greatly difference between the samples E,F and the samples S(baked Omin),C (baked 15min). The volatile flavor compounds which have the largest contribution to the overall flavor of Rong-chang pork after processing are Pyrazine,2,3-dimethyl-, Pyrazine,2,5-dimethyl-, Pyrazine,,2-ethyl-6-methyl-, Pyrazine,,trimethyl-, Disulfide, dimethyl, Dimethyl Trisulfide, and Bis(2-furfuryl)disulfide.
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