Processing Technology And Shelf Life Stability Prediction Of Room Temperature Cheese

As a deep-processed,high-value-added dairy product,cheese is known as the "milk gold".However,short shelf life and insufficient varities of domestic natural cheese limits the development of Chinese cheese consumption market.In order to solve this problem,this paper studied the hot processing technology and shelf life prediction of room temperature process cheese.By analyzing the bactericidal effect and quality attributes under different sterilization methods,the influence mechanism of microorganism and heat treatment of cheese is explained.The specific results are as follows:(1)Research on the formula design and hot processing technology of room temperature liquid cheese.The optimum additive formula and processing parameters of room temperature liquid cheese were determined by single factor test and Box-Behnken experimental design model,and the main reason of instability of liquid cheese were analyzed by Turbiscan multiple light scattering technique.Results showed that the effects of various factors on the TSI and sensory scores of room temperature liquid cheese were in the following order:emulsified salt(A)>emulsifier(B)>stabilizer(C).The optimum additive formula were 0.60%emulsified salt,0.60%emulsifier,0.70%stabilizer and 5.5%sweetener.Under this conditions,the sensory score and TSI value within 24 hours at 37℃ of the sample is 89 and 0.80,with a backscattered light intensity changes at the top and bottom of 0.66 and 0.78,respectively.These results indicate that the delamination and the stability of room temperature liquid cheese can be improved by adjusting the raito of emulsified salt,emulsifier and stabilizer.(2)Study on the quality change of liquid cheese and the establishment of shelf life prediction model.Liquid cheese were stored at 4℃,25℃ and 37℃ and analyzed for sensory,physicochemical,microbiological and flavor quality at 0,30,60 and 90 days to observe changes in quality during shelf life.At the same time,the shelf life of the product is predicted by constructing the mathematical model through the accelerated test of the shelf life of room temperature liquid cheese.The results showed that pH and particle size increased during the storage period,while TSI increased at first and then decreased,and the change rate accelerated with the increase of storage temperature.The color change results showed that the changes of L*,b*and ΔE values of cheese sample stored at 37℃ were significantly higher than that of stored at 4℃ and 25℃.In addition,sensory evaluation showed that the shelf life of room temperature liquid cheese was more than 90 days when they are stored at 4℃ and 25℃，while the quality of the samples decreased significantly when the samples were stored at 37℃.The kinetic equation of the accelerated test of room temperature liquid cheese is TSIt=0.081t-0.905,R2=0.993.This model fits well and can be used to predict the shelf life of room temperature liquid cheese quickly and accurately.(3)Research on the effect of high pressure and thermal processing on shelf life and quality attributes of processed cream cheese.Processed cream cheese was prepared by five different processing methods,and the effects of ultra-high pressure and heat treatment on microorganisms(total colony count,yeast and mold),Maillard products(furosine,fluuorescence intensity),thermal stability and secondary structure of reprocessed cream cheese were investigated.The results show that the commercial sterile can be achieved by spore germinating and subsequent high pressure treatment(75℃/550 MPa/20 min).Compared with the UHT treatment group(A),the furoic acid content of the cheese treated with ultra-high pressure(D1 and D2 groups)decreased by 70.00%and 29.80%respectively,and the fluorescence intensity was closer to that of the untreated group.Furthermore,color parameters of the ultra-high pressure treatment group were closer to the control,while the heat stability was significantly improved.The secondary structure of protein after HPP trearment changed significantly,with decreased β-folding and random coils decreased and increased α-helix and β-sheet increased.The results show that the ultrahigh pressure process after spore induction and germination can not only maintain the color,flavor and nutritional properties of processed cream cheese,but also prolong the shelf life of the product.