Study On Quality Improvement Of Processed Cheese At Room Temperature

At present,China’s processed cheese is developing rapidly,but the cold chain in some areas is not perfect,which will limit the development of processed cheese.Therefore,room temperature processed cheese has broad development prospects.Normal temperature processed cheese is obtained after high temperature sterilization of processed cheese.High temperature sterilization of cheese will lead to changes in its appearance,structure and flavor.At the same time,it will also be accompanied by Maillard reaction.Among them,the softening of cheese texture and oil precipitation are the most prominent problems.Therefore,this study aims to explore the problems of softening texture and oil precipitation of room temperature processed cheese during storage.Whey protein isolate(WPI)was used to pre emulsify the emulsion and emulsion gel to improve the texture and softening of the reprocessed cheese at normal temperature.The compound emulsifier and whey protein isolate pectin composite emulsion were used to improve the oil release during the preservation process.Whey protein isolate was used to pre emulsify the butter to prepare whey protein isolate emulsion.The emulsion p H was adjusted to prepare the emulsion gel.Then the emulsion and emulsion gel were added to the preparation of normal temperature reprocessed cheese.After the sterilization was made at 121 C 15 min and 100 min 15 min,the reprocessed cheese and chilled reprocessed cheese were obtained,then stored at room temperature and 4 C respectively.The results showed that after pre emulsification of whey protein isolate,the processed cheese at room temperature had high hardness,adhesion and chewability,and its hardness first increased and then decreased with the extension of storage time.The pre emulsification of whey protein isolate aggravates the oil precipitation of cheese.Scanning electron microscopy(SEM)showed that the uniformity of cheese microstructure decreased and the number of large free fat pools increased after pre emulsification.In addition,the pre emulsification of whey protein isolate can slow down the Maillard reaction process of refrigerated processed cheese and reduce the content of Maillard products such as hydroxymethylfurfural(HMF),acetone aldehyde(Mg O)and glyoxal(go).The experimental results show that although pre emulsification can effectively improve the texture characteristics of room temperature processed cheese,it has an adverse effect on oil precipitation.In order to improve the problem of oil precipitation in pre emulsified room temperature processed cheese,the influence of composite emulsifier on the emulsifying effect of room temperature processed cheese was investigated.According to the single factor experiment and taking the oil precipitation as the index,the single emulsifier(sucrose fatty acid ester,glycerol monostearate and hexapolyglycerol monooleate)with good effect of controlling oil precipitation was selected.Using the additivity of hydrophilic lipophilic balance value(HLB),the optimum HLB value of room temperature processed cheese was determined to be 12.20,and then the emulsifier was compounded according to the HLB value to obtain the optimum dosage of composite emulsifier: hexapolyglycerol monooleate(71%)and sucrose fatty acid ester(29%),and the optimum dosage was 0.5%.The compound emulsifier was applied to the production of room temperature processed cheese to investigate its effect on the oil precipitation of room temperature processed cheese.During storage,the compound emulsifier can effectively control the precipitation of oil in room temperature processed cheese.The addition of compound emulsifier makes the fat distribution in room temperature processed cheese more uniform.The rheological results showed that the melting temperature of cheese was reduced and cheese was easier to melt after adding composite emulsifier.In order to improve the texture and oil precipitation of reprocessed cheese at ambient temperature,a whey protein isolate pectin emulsion was prepared by using the complex condensation reaction of anionic polysaccharide gum and whey protein isolate emulsion.The whey protein isolate emulsion was used as a control group to study the thermal stability of two emulsions under heating conditions.With the increase of heating temperature,the addition of pectin will help stabilize the emulsion droplet and reduce protein aggregation.The absolute value of the potential value of whey protein isolate pectin emulsion is higher,and the mean diameter(d4,3)of the pectin emulsion is smaller.The results showed that the addition of pectin increased the thermal stability of whey protein isolate emulsion.Then,two kinds of emulsions were used to pre emulsify the butter in cheese.The results showed that whey protein isolate pectin emulsion significantly improved the texture and oil release characteristics of the cheese at ambient temperature.The cheese made from whey protein isolate pectin pre emulsified at normal temperature had higher hardness,adhesion and chewiness,and its microstructure also improved,and the fat distribution was more uniform.In conclusion,whey protein isolate pectin emulsion can effectively improve the texture and oil release characteristics of ambient temperature reprocessed cheese,and inhibit the accumulation of fat in the reprocessed cheese at normal temperature.The introduction of the whey protein can significantly improve its stability during storage,and is of great significance for the processing and popularization of the reprocessed cheese at constant temperature.