The Influence Of Heat Treatment On The Flavor And Preservation Quality Of Milk

Heating as a common means of preservation of milk has been used widely,but during the process of heating treatment,many different physicochemical reactions will be happened,resulting in milk system transforming and instability,the most obvious sensory experience is the flavor of milk has changed after heat treatment.Since milk is a complicated system,the flavor and quality will be changed due to the degree of heat treatment and the temperature of preservation during storage.Therefore,this article studies the relationship between flavor and the degree of heat treatment in different degree of heat treatment,at the same time the preservation of sterilized milks to explore their quality changes in the storage period.The main results are as follows:1 Effect of different heat treatments on the Maillard reaction products of milk:Through the detection of two kinds of Maillard reaction products on behalf of furosine and 5-hydroxymethyl furfural in different degree of heatting treatment of milk,concluded that:the heating temperature and time effected Maillard reaction,heating temperature can be increased to improve the Maillard reaction,the heating time accumulated Maillard reaction.The different heat treatment of milk for proteomics analysis that verified the positive effect of heating temperature on the Maillard reaction,the reaction temperature is higher than 130 ℃,protein types of Maillard reaction is increased,the reaction sites increased significantly,too.2 The affect of different heat treatment on volatile flavor substances:In this paper,the detection of free amino acid,cysteine and volatile flavor compounds,the study found that:the free amino acids is fluctuated irregularly that can not explain the reason of the phenomenon;thiol content decreased with the increase of heating degree deepening gradually,turning into the volatile flavor compounds of other sulfur mainly,so that impact on milk flavor.Using GC-MS for classification and identification of the milk flavor,found that the influence of the flavor is ketones,the high content is acetone and 2- methylethyl ketone.Detection of milk flavor by electronic tongue and electronic nose,with the increase of heating temperature and heating time,milk PCA moved clockwise,electronic tongue DFA extended counterclockwise.Influence of different heat treatment in milk flavor substances,thereby affecting the flavor of milk.3 Changes of milk enzyme under different storage conditions:Milks still remains part of protease,lipase and fibrinolytic enzyme after the ultra pasteurized milk and sterilized UHT,these enzymes have a certain impact on the quality of milk.And in the preservation process,the ultra pasteurized enzyme activity is higher than the UHT sterilization milk, which may be an important factor in UHT milk than pasteurized milk quality stability.4 Different storage conditions on the quality of milk:In the process of preservation,the p H value,color,Zeta potential and the colloidal particle size of ultra pasteurized milk and the UHT milk have been changed increased with the storage time,especially ultra pasteurized milk has obvious changes in 35 days,the analysis of Zeta potential,ultra pasteurized milk system gradually is not stable and quality changes significantly after 35 days,so that predict ultra pasteurized milk’s shelf-life is 35 days.The overall properties of the UHT milk is more stable than the ultra pasteurized milk,which have a great relationship with the heat treatment intensity,at the same time enzyme activity are linked closely.Along with the change of storage time,ultra pasteurized milk flavor changes greatly after the electronic tongue and nose,and the difference of the UHT milk flavor is small,further validation of the UHT milk’s flavor is more stable than the pasteurized milk.In the process of flavor analysis of ultra pasteurized milk,the flavor of milk preserved at 4℃ is close to unpreserved milk flvour,so ultra pasteurized milk is better in 4 ℃ to keep better flavor and quality.