Effects Of Flash Deoxygenation Technology Combined With UHT Sterilization On Milk Quality

During the milk collection process,the milk absorbs the surrounding air,increasing the dissolved oxygen(DO)content in the milk.These increases in dissolved oxygen exacerbate the chemical reactions of milk during UHT sterilization,such as Maillard reactions,lipid oxidation,and protein oxygen,which often lead to browning,flavor changes,and loss of nutritional value.And dissolved oxygen will reduce the quality of UHT milk during storage.Therefore,the quality of UHT milk can be improved by removing dissolved oxygen in raw milk.The purpose of this paper is to reduce the content of dissolved oxygen in milk by flash deoxygenation technology,and to determine the changes in the content of thermally processed products in milk after deoxygenation under heat treatment conditions,and to analyze and compare the changes in milk quality under different heat treatment processes and storage temperatures.The raw milk was deoxygenated by flash evaporation technology,and the dissolved oxygen content in the milk after flashing was determined by using a dissolved oxygen meter.Flash deoxidation parameters,the results show that the two optimal flash deoxidation conditions are that when the flash temperature is 70℃,the vacuum degree is -0.06 MPa,the dissolved oxygen extraction rate of milk is 34.13%and the flash temperature is 34..13%.When the temperature is 60℃ and the vacuum degree is -0.08 MPa,the dissolved oxygen extraction rate of milk is 61.09%.The effect of flash evaporation on milk quality was assessed by measuring changes in stability and the degree of oxidation of milk lipids and proteins.The analysis results showed that the oxidation degree of the milk after flash evaporation was increased compared with that of the raw milk,but the difference was not significant(p>0.05).In addition,the stability of the milk after flashing did not change significantly.The stability changes in deoxygenated UHT milk were determined by Turbiscan Lab stability analyzer;the changes in the degree of lipid and protein oxidation in milk after deoxygenation were determined by microplate reader and fluorescence spectrophotometer.Chromatography was used to measure the changes in the content of its products;volatile flavor substances were measured by gas chromatography(GC-MS).The measurement results show that when the UHT sterilization temperature is 130℃,10 s,and the dissolved oxygen content is 1.14 mg/L,the stability of UHT milk is the best,and the degree of oxidation and Maillard reaction has the lowest degree of influence on the quality.The inhibition rate of furosine was 33.23±1.72%,and the inhibition rate of 5-HMF was 25.43±3.14%.At the same time,it also improved the milky aroma and sweetness of milk,and reduced the content of undesired volatile flavor substances.During the storage period,higher storage temperature will negatively affect the quality of UHT milk again.By measuring the changes of some markers under different storage temeratures and dissolved oxygen conditions,it is again found that the dissolved oxygen content is 1.14 mg/At the temperature of 20℃ and 30℃,L can reduce the influence of the oxidation of milk and the degree of Maillard reaction,indicating that the reduction of dissolved oxygen content improves the storage quality of UHT milk and reduces the loss of nutrients.The research results show that flash deoxygenation technology combined with UHT sterilization can indeed reduce the generation of thermal processing by-products,improve the flavor of UHT milk and reduce the loss of nutrients.In this experiment,when the dissolved oxygen(DO)was 1.14 mg/L,UHT milk has the best quality.Putting this technology into the industrial production of UHT milk can greatly improve the quality of UHT milk and eliminate consumers’ negative perception of UHT milk.