| In china, cured products are the important parts of precious cultural heritage in the world because of their long history and ethnic characteristics. Bacon as a typical representative of Chinese traditional cured products, and in recent years, modern bacon processing industry had been growing quickly due to the increasing production and varieties. But the recent researches mostly concentrate on the flavor or the aspects of the improvement of process parameters for traditional bacon while the the comprehensive and systematic research for bacon which producted by modern processing was still lack of. In this paper, physical and chemical indexes of the production process, variation and the reasons for changes of flavor components, the prediction of shelf life are all researched based on the modified Chongqing bacon as with the simple research of qualities and flavor elements for the isntant bacon products. The results would have the important value which would contribute to the better understanding of the mechanism and the process improvements for the modified Chongqing bacon as well as the improvements for storage and distribution. The main researches are as follows:(1)Physical and chemical indicators, lipid content and fatty acid composition of the modified Chongqing bacon kept changing during processing. AV increased sharply at the end of salting while TBA and POV rose markedly after electric baking, then POV showed downward trend but TBA changed slightly. Lipase activities went up significantly after salting and then declined insistently. The components of phospholipids and fatty acid varied considerably before smudging under the influence of lipase activities, which meant both the content and fatty acid composition of phospholipids changed conversely with free fatty acid, while the content and ralative quantity of fatty acid profile of triacylglycerols(TAG) kept stable, this showed phospholipid hydrolysis was significant during the processing. Therefore, phospholipid hydrolysis may be the main source of free fatty acids. But whether phospholipid was the main substance for the flavor needed further study.(2) 8 kinds of volatile flavor compounds which were alcohols, aldehydes, ketones, phenols, esters, acids, ethers, hydrocarbons and furans in modified Chongqing bacon during the processing by solid phase microextraction(HS-SPME) combined with gas chromatography-mass spectrometry(GC-MS). And aldehydes, phenols, esters, hydrocarbons were the main volatile flavors. Both of the type and relative content of aldehydes showed a decreasing after the first increase trend. The type of phenols went up to the maximum at the 10 d days of smoking period while the relative content changed not significant at the latter smoking period. The type and relative content of esters showed the opposite trend during the smoking time while both of the type and relative content of alcohols and hydrocarbons rose slightly. And the main volatile flavor compounds were: hexanal, heptanal, octanal, nonanal, phenol, guaiacol, 2-methoxy-4-methyl phenol, 4-ethyl-2-methoxy phenol, 4-vinyl-2-methoxy phenol, 2,6-dimethoxy phenol, ethyl caproate, ethyl caprylate, ethyl caprate, naphthalene, 1-methylnaphthalene.(3) The quality changes of modified Chongqing bacon which stored at different temperatures showed the similar trend. Changes in sensory quality of bacon during the different storage temperature declined gradually, and all the samples which stored at 25℃ reached the sensory refused point at 84 d while stored at 30℃, 35℃ reached the sensory refused point at 42 d and 25 d. The total bacterial count, AV, POV and TBA values rose increasingly and the rate was 35℃>30℃>25℃. Ea was 8.69×104 J/mol, k0 was 2.97×1013 and the first order kinetics equation was also calculated according to Arrhenius curves of POV values which were selected as the shelf life prediction model through the pearson correlation coefficient values of the physical and chemical indicators at different storage temperatures. Thus, the theoretical value of shelf life of bacon was predicted by the sensory refused point and first order kinetics equation, and the values were 459, 93, 24 d, respectively, which were better in line with practice.(4) The quality changes of instant bacon products which formed by samples had been smoked during storage after sterilization treatment were: The sensory test of instant bacon products after vacuum packaging and second disinfect had no significant difference during storage(p>0.05), but higher than the control group, which showed that second disinfect could help to keep sensory quality of instant bacon products. The microbial counts of different groups of instant bacon products kept slightly increase trend during storage, and at the end of storage, the microbial counts of instant bacon products by water bath sterilization was ±3 lg CFU/g while the control group was 3.69 lg CFU/g which closed to the critical value of deterioration of instant bacon products, but none exceeded. The values of L *, a *of lean of different groups dropped gradually while the value of b* fluctuated with irregular trend, the value of L *of fat of different groups kept the downward trend during storage while both of the values of a *, b* increased continuously with the significant difference(p<0.05). The values of AV of different groups went up slowly, the values of POV of three groups showed no significance(p>0.05) at the early stage of the storage, but after that the increase rate of POV of control group was higher than the groups by second disinfect, the values of TBA fluctuated slightly and kept stable during storage. Therefore, the low temperature preservation contributed to inhibit microbial growth and extend shelf life of instant bacon products based on the physical and chemical indicators. Meanwhile, the preservation effect was better under the treatment by second disinfect and the order was 85℃>95℃.(5)About 100 volatile flavor compounds of the instant bacon products after second disinfect during storage were detected by solid phase microextraction(HS-SPME) combined with gas chromatography-mass(GC-MS). And acids, phenols, aldehydes, alcohols, ketones as with hydrocarbons were main volatile flavors which changed slowly, indicating that the low temperature preservation effectively reduced fat oxidation to preserve the flavor. Meanwhile, based on the variation of types and relative contents of acids, phenols, aldehydes and changes of main flavor compounds including alcohols, ketones as with hydrocarbons of instant bacon products during storage, the result showed that second disinfect contributed to reduced fat oxidation to extend the storage period, and the order was 85℃>95℃. |
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