Study On Ultra High Pressure Sterilization Process And Quality Of Leisure Bean Products

The leisure bean products are the instant soybean products which are made by the semi-dehydrated tofu which serve as dishes through the processes of marinated, flavoring, packaging and sterilization into unique flavors, meeting the demand for leisure, tourism and other consumer demand, among which the typical products are the spicy and smoked semi-dehydrated tofu in Sichuan, the Hunan thick gravy-stewed semi-dehydrated tofu, Anhui dried bean curd and the fried and thick gravy-stewed semi-dehydrated tofu. Because it is easy to eat, delicious, the products are popular in the country, the annual sales is in increase year on year, the annual output value of the Hunan leisure semi-dehydrated tofu’s Shaoyang flavor alone is more than 3 billion RMB. At present, most of the leisure bean products use thermal sterilization, thus the product safety is ensured and the shelf life is extended. But high temperature treatment will lead to the decline in product quality, such as structural hardening, reduced springiness, flavor loss, this will seriously affect the product sales, restrict the development of soybean products industry. The ultra high pressure technology can effectively kill microorganisms in food under low temperature conditions, and better maintain the original quality of food.The study sets the Hunan leisure semi-dehydrated tofu’s Shaoyang flavor as the research object, the ultra-high pressure sterilization process is optimized by using the response surface method, and by comparing with the two mostly commonly used plant heat sterilization processes, the effects of the ultra-high pressure process on the quality of products is studied. The main findings are as follows:1.Wit hthe sterilization rate as the evaluation index, the single factors’ investigation on pressure, holding time and temperature was carried out, and the response surface method was used to optimize the ultra high pressure sterilization process, the optimal ultra-high pressure sterilization process was: the pressure was 438 MPa, 21 minutes’ holding time, and the temperature is 61 centigrade, the sterilization rate was 96.62% at this time, this is superior than the plant’s most commonly used heat sterilization process pasteurization(95 centigrade and with the holding time of 40 minutes) and the sterilization of anti-pressure high temperature(115 centigrade, and the holding time is 20 minutes).2.By sensory evaluation and texture analyzer measurement, the comparative analysis was performed of the color, smell, taste, hardness, springiness and chewiness to the leisure semi-dehydrated tofu of unsterilization, pasteurization, anti-pressure high temperature sterilization and ultra-high sterilization, and it is found that:(1)The texture analyzer measurement results show that, compared with the non-sterilized leisure tofu products, the hardness of those of the high pressure and heat sterilization significantly increased(P<0.05), the springiness decreased, the chewiness have increased. There was no significant differences between the hardness, springiness and chewiness of the ultra-high pressure treated samples and those treated with the pasteurization(P>0.05), there was significant differences between them and those treated with the anti-pressure high temperature(P<0.05).(2)The double-blind sensory evaluation results show that the raw sample sensory scored the highest(94.3 points), the samples treated with the anti-pressure high temperature scored the lowest(85.1 points), and the sensory staff can clearly feel that, the hardening of the product structure, the increase in the resistance to chewiness, the decline in springiness, the weakening of the flavor, this shows that the product quality declined significantly. The processing sensory score of the ultra-high pressure was 92.8 points, and was ranked second, which is higher than the 89.1 points of the pasteurization, there are no significant differences between the score and the non-sterilized sample sensory score, and the acceptance was higher.(3)The correlation between the texture parameters and the sensory score was analyzed. The sensory score was significantly correlated with hardness and chewiness ability, and the correlative coefficients were-0.952 and-0.983 respectively, was positively correlated with springiness(R2=0.89), which showed that the texture parameters can objectively reflect the quality of the leisure bean products. And the degree between hardness and chewing was highly correlated(R2=0.978), whereas the springiness was negatively correlated with the hardness and chewing performance.