Formation And Control Technology Of Thermal Processed By-Products In Milk

Milk is a food with high nutritional value.Heat sterilization ensures the safety of dairy products and extends the shelf life.However,traditional thermal processing or excessive processing can degrade cow milk protein,cause loss of active ingredients and nutrients in daily products,deteriorate flavor,etc.At the same time,complex chemical reactions occur.With the generation of thermal processing by-products,there are potential safety risks.This topic systematically analyzes the production of thermal processing by-products in liquid milk in the traditional process.The effect of static ultrahigh pressure on the sterilization and by-products of liquid milk is studied.A low-temperature composite ultra-high pressure processing technology for liquid milk is established to reduce thermal processing in dairy products The production of by-products improves the quality of dairy products.The results show that the deeper the degree of thermal processing,the higher the amount of by-products generated.The production of ?-dicarbonyl compounds,5-hydroxymethylfurfural,furosine,N?-(Carboxymethyl)lysine and N?-(Carboxyethyl)lysine in pasteurized milk(72-85?,15-20 s)showed no significant difference from that of superpasteurized milk(125-138?,2-4 s).Except for some ultra-high temperature instantaneous sterilization(135-150?,4-7s)milk,the content of ?-dicarbonyl compounds was lower than that of pasteurized milk and superpasteurized milk,the yield of other thermal processing by-products was significantly higher than that of pasteurized milk.Various thermal processing by-products produced in formulated and brown milk are significantly higher than in ultra-high temperature instant sterilized milk.During the static ultra-high pressure treatment of raw milk,the single factor test(200-600 MPa,3-20 min)showed that different ultra-high pressure conditions have different germicidal effects.The greater the pressure,the better the killing effect of microorganisms.The 400 MPa pressure treatment for 10 min can effectively kill the coliform bacteria in milk,but the treatment of Staphylococcus aureus and Salmonella is not stable.The sterilization effect is stable when treated at 600 MPa for more than 10 min,and the production of hot processing by-products can be significantly reduced.The raw milk is further treated with low temperature insulation(50?,10-30 min)and ultra-high pressure(400-600 MPa,5-15 min).Using thermal processing by-products and microorganisms as the evaluation criteria,a low-temperature composite ultra-high pressure treatment of milk was initially established:the heat treatment at 50? for 20 min combined with 500 MPa pressure for 10 min.This process reduces the intensity of the ultra-high pressure treatment alone and ensures the microbial safety of the product.Compared with traditional pasteurization,the content of ?-dicarbonyl compounds,N?-(Carboxymethyl)lysine and N?-(Carboxyethyl)lysine in liquid milk Significantly reduced(p<0.05).As a result,the quality of liquid milk is significantly improved.