| Chicken soup is rich in nutritional value and health-care functions, and it is favored by consumers from various populations. With the development of the society, the ready-to-eat nutritional chicken soup will become mainstream soup product in the future. At present, the processing of chicken soup is mainly based on traditional methods, which have disadvantages of time-consuming processing and low industrialization. High Pressure Processing(HPP) is currently prevailing because of time-saving and efficient characteristics, but the processing conditions play an important role in nutritional quality and the overall taste of soup. Therefore, it is necessary to improve the processing so as to enhance its nutritional value and taste and make it suitable for industrial production. In this paper, the HPP was optimized using the response surface methodology; on this basis, the basic physical properties, non volatile flavor, volatile flavor substances and relationship among them were investigated, and the change of sensory, chemical and microbial quality of chicken soup in refrigeration, partial freezing and frozen were studied, based on which, storage dynamics model was built, thus providing certain theoretical guide for the industrialized production of high-pressure chicken soup. Main conclusions were as follows:1. The optimal boiling conditions of high-pressure chicken soup: boiling time of 40 min, boiling temperature of 120℃, liquid-to-meat ratio of 1.4:1. Under this conditions, the actual values of sensory score, soluble solids and soluble protein were 8.67±0.42,(2.60±0.10)% and(19.78±0.63) mg/m L respectively, and there was a relative error less than 8% compared with predicted values, which indicated that the processing was reliable and had practical value.2. The comparison of quality between the high-pressure chicken soup and traditional chicken soup: compared with the traditional processing, theHPP shortened the cooking time by nearly 2/3. Both of them had a similar comprehensive sensory quality and nutritive peculiarity. 65 kinds of volatile flavor substances were detected at six time points, 51 of them were common, including hydrocarbons, aldehydes, ketones, alcohols, acids, esters and furans, and so on. Due to the higher average relative contents(59.78 and 23.32% respectively), aldehydes and alcohols were proved to be main volatile flavor substances. The alcohols, acids and esters contents in high-pressure chicken soup were relatively higher than traditional chicken soup, whereas hydrocarbons, ketones and aldehydes contents in traditional chicken soup were relatively higher. In addition, higher content of low threshold flavor substances from high-pressure chicken soup were detected, such as(E,E)-2,4-Decadienal, 2,3-Octanedione, 1-Octene-3-ol, 1-Octanol, and so on.3. The changes of basic physical properties and flavor substances of high-pressure chicken soup: as the extension of pressurization time, the aroma, taste and overall acceptability scores of high-pressure chicken soup showed a gradual increase on a overall trend(p<0.05), and reached the optimum at the end of term; on the whole, L* and Ytotal decreased significantly(p<0.05), while b* was just the opposite(p<0.05); pH value changed slowly after a significant increase; soluble solids, soluble protein, peptides, total sugars, free amino acids and inosinic acid contents of high-pressure chicken soup overall showed a significant upward trend(p<0.05); USFA, PUFA, MUFA increased firstly and then decreased slowly(p>0.05), and the change trend of SFA was contrary to USFA(p>0.05), chicken soup at the end of boiling contained higher PUFA, EFA, P/S and better n-6/n-3 value. During the whole stage(15~40 min), 92 kinds of volatile flavor substances were detected at six time points, 42 of them were common. The average relative content of aldehydes accounted the highest proportion(65.08%), which were main volatile flavor substances of high-pressure chicken soup. At different time points, main flavor substances of high-pressure chicken soup were basically consistent, but the relative contents among them were different, thus leading to different senses of chicken soup. Using the principal component analysis method, 4 kinds of main flavor compounds of high pressure chicken soup were screened out, namely Hexanal,(E,E)-2,4-Decadienal, 2,3-Octanedione, 2-Pentyl furan.4. The correlation between basic physical properties and flavor substances of high-pressure chicken soup: correlation analysis revealed that a significant positive correlation existed among soluble solids, soluble protein, free amino acids, total sugars, oleic acid and sensory quality(p<0.05), whereas saturated fatty acids such as pentadecane acid, heptadecylic acid and stearic acid showed a significant negative correlation with it(p<0.05). The rich aroma of high-pressure chicken soup was produced by the interaction of a variety of volatile flavor substances, and correlation analysis revealed that there was a high correlation among 3-Octene-2-one, Hexadecanal, 3-Nonene-2-one, 2-Pentyl furan, 2-butyl-tetrahydro-furan and sensory aroma, but the correlation with other components was poor. Most of the aldehydes, ketones and alcohols presented a strong correlation with fatty acids(p<0.05), whereas small part of ketones, hydrocarbons, furans and free amino acids and total sugars exhibited a substantial correlation(p<0.05).5. The changes of quality of high-pressure chicken soup during storage: with the extension of storage time, the sensory scores and pH value of cold storage, partial freezing and frozen chicken soup showed a gradual downward trend, while the TVB-N value, TBARS value and TVC presented a gradual increasing trend. The change in cold storage was more significant than that of another two(p<0.05). Correlation analysis revealed that TBARS value was significantly correlated with sensory score(p<0.01), the correlation coefficient was greater than 0.9. The storage dynamics model based on TBARS value was established, on this basis, the predicted value of the shelf life of high-pressure chicken soup at-2.5℃ was 136 days, and shelf life of 258 days at-18℃. In the three ways mentioned above, the shelf life of cold storage(4℃) was the shortest(only 81 days); the storage time of frozen storage(-18℃) was the longest, but the cost was higher; taking into account the actual production, micro-freeze(-2.5℃) preservation will be the best method for industrial production and supermarket sales of high-pressure chicken soup in the future. |
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