Studies On The Factors Affecting The Formation Of Maillard Reaction Harmful Products In Whole Milk And Milk Powder

Maillard reaction harmful products such as furosine,furfural compounds and advanced glycation end products(AGEs)have attracted researchers' great attention in recent years because they exist extensively in thermal processing foods which are rich in protein and reducing sugars.Although the formation pathways and affecting factors of various types of thermal reaction harmful products in the simulation system have been basically clear at present,there is little research on Maillard reaction harmful products in the actual system,especially the milk system,and there is a lack of the holistic understanding.Therefore,this thesis will detailedly study the effects of thermal processing intensity,storage time of room temperature,total microorganisms amount of raw milk on the formation of eight major potential harmful products in the initial,intermidiate and advanced stages of Maillard reaction and the consumption of substrate lysine in the whole milk and milk powder systems(pasteurized milk,commercial sterilized milk,reconstituted milk and milk powder).In order to study the effects of thermal processing temperature and time,low-temperature long-time pasteurized milk(LTLT),high-temperature short-time pasteurized milk(HTST),extended shelf life of ultra-pasteurized milk(ESL),ultra-high temperature instantaneous sterilization combined with aseptic filling milk(UHT),commercial sterilization milk after aseptic filling(BS)using fresh raw milk as raw material and milk powders prepared by spray drying using the above five heat-treated milk as raw materials were used to investigate the levels of Maillard reaction harmful products formation and the substrate lysine consumption;and on this basis,the above five kinds of milk powders were used as raw materials to make the reconstituted milk through the LTLT processing again so as to investigate the effects of multiple heat treatments on the Maillard reaction harmful products formation and the substrate lysine consumption in the dairy products.The results showed that the raw milk itself contained a certain amount of furosine,5-hydroxymethylfurfural(5-HMF),5-methylfurfural(5-MF),carboxymethyllysine(CML)and carboxyethyllysine(CEL),and after heat treatment,the eight major potential harmful products increased significantly(p<0.05);and the higher the pretreatment heating intensity,the more the loss of the Maillard reaction substrate lysine and the more the accumulation of harmful products.Multiple heating sterilization or spray drying after heating could significantly accelerate the carbonylation reaction between lactose and lysine,resulting in a rapid increase in the accumulation of the Maillard reaction initial product furosine,meaning that the furosine content in the reconstituted milk increased by 24.75 ~ 38.88 ?g/mL,while the milk powder increased by 37.15 ~ 102.92 ?g/mLwith the comparasion with the five preheat-treated milk;while the formation rates of four furfurals and three AGEs from Amadori product through 1,2-enolization in the all five reconstituted milk were accelestrated,resulting in a significant increase in the level of AGEs by 67% to 113%.In addition,there is a certain superposition between the intensity and the times of heat treatment in milk,which could cause a significant increase in the cumulative amount of Maillard reaction harmful products.In order to investigate the effects of storage time of room temperature,UHT sterilization milk and five kinds of milk powders with different preheating treatment degrees were used to study the levels of Maillard reaction harmful products generation and substrate lysine consumption;and the six kinds of LTLT milk powders stored at room temperature for different time were used as raw material to prepare the reconstituted milk through the LTLT processing again to investigate the impact of raw material storage time on the consumption of substrate lysine and the formation of Maillard reaction harmful products in the re-products.The results indicated that with the prolongation of room temperature storage time,the consumtion of lysine and the accumulation of harmful products in UHT sterilized milk and five kinds of milk powder increased significantly(p<0.05).The analysis of the generation pathways showed that the reason for the continuous increase of the eight major potential harmful products contents in reconstituted milk caused by the room temperature storage was not only the Maillard reaction pathway,but the oxidized fat in the raw milk powder which could further promote the formation and accumulation of AGEs through the Acetol pathway increasing by 2 to 3 times.At the same time,the storage experiment results also showed that there was a certain superposition among the thermal processing intensity,storage time and processing times,which could lead to a rapid decrease in lysine level and a rapid increase in Maillard reaction harmful products levels of dairy products.In order to explore the influence of microbial content in raw milk,the levels of Maillard reaction harmful products formation and the substrates lactose and lysine consumption in both raw milk of different microbial content and its UHT sterilization milk were discussed.The results showed that with the exponential increase of the total microorganism amount of raw milk,the content of lysine and lactose in raw milk decreased by 26% and 16% respectively,and the accumulation of harmful products in the initial and intermidiate stages of Maillard reaction decreased by 40% and 55% respectively,while the accumulation of AGEs significantly increased(p<0.05),meaning that CML and CEL increased by 38% and 146% respectively.Moreover,the lysine and lactose contents were in a further decrease while the the levels of harmful products in the early,middle and late stages of Maillard reaction were in a significangt increase in the above-mentioned UHT sterilized milk produced by different microbial content of raw milk.