| Infant formula is the best breast milk substitute designed to meet the nutritional needs of infants,and its nutritional value,quality and safety are directly related to the early growth and development of infants and their quality of life.Infant formula requires a high degree of heat treatment to ensure the microbiological safety of the product.However,during the heat treatment process,the dairy powder system is susceptible to thermal damage,such as the maillard reaction,resulting in the loss of nutrients and the formation of harmful products such as furfural and advanced glycation end products(AGEs).At present,there is a lack of systematic understanding and research on the formation of maillard reaction harmful products(MRHPs)during the processing of infant formulae.Therefore,this thesis takes infant formula as the object of study.Firstly,different brands of 1-3 stage commercially available infant formula were selected and analysed for their levels of MRHPs,and correlation analysis was used to try to investigate the link between the differences in nutrient composition and the formation of harmful products.Subsequently,by designing milk powder formulations and simulating industrial production,the effects of stepwise addition of the raw materials,as well as different pasteurisation methods and spray drying temperatures,on the formation of MRHPs were investigated,and possible links and patterns of influence between the formation of MRHPs were analysed.On this basis,a Genetic Algorithms-Back Propagation(GA-BP)Neural Network was designed using Matlab software to construct a prediction model for the formation of MRHPs in infant formulae.The main contents and results of the study are summarised as follows:(1)Thirty commercially available infant formulas were used to determine the levels of their main nutrients(protein,fat,etc.)and the levels of the MRHPs(furosine,carboxymethyl lysine,carboxyethyl lysine,etc.),and to investigate the correlation between the physical and chemical indicators of infant formulas and the MRHPs.The results showed that the protein and fat content,moisture,colour difference values and the levels of MRHPs in the 1-2 formulae were all similar.The brightness value,protein and moisture content of the 1-2 stage formulae were lower than 3 stage formulae,while the b-value,polyunsaturated fatty acid content(PUFA),furosine,3-DG,MGO,GO,CML and CEL were all higher than 3 stage formulae.The results of the correlation analysis suggest that unsaturated fatty acids are associated with the accumulation of carbonyl compounds,which can influence the accumulation of HMF,CML and CEL through the enolisation pathway or in combination with active amino groups,and that the accumulation of AGEs can lead to product browning.(2)The influence of the Key Process Control Points(KPCPs)on the formation of the MRHPs during the production and processing of infant formula was studied and the relevant patterns were summarised.In order to further understand the trend of the formation of the harmful products in the process of formula production and processing,the three KPCPs of raw materials addition,pasteurization and spray drying were selected for analysis.The results showed that the increase in the proportion of PUFA and the protein content after the addition of raw materials promoted the accumulation of MRHPs,leading to browning of the milk powder.Compared to the high temperature short time pasteurisation method,the low temperature long time pasteurisation method was more likely to lead to the accumulation of MRHPs after the addition of raw materials.In addition,with the increase of spray drying temperature,furosine and HMF accumulated gradually,while the yield of intermediate products such as 3-DG,DA,MGO and GO was lower than the conversion rate and their content gradually decreased,and the late product CML accumulated continuously with the increase of spray drying temperature,while the overall trend of CEL decreased.(3)The effects of different raw material compositions on the formation of furosine,α-dicarbonyl compounds,HMF,CML and CEL were analysed by combining the physical and chemical properties such as nutrients,moisture and colour,and the related mechanisms of action were investigated.The results showed that whey powder promoted the accumulation of various MRHPs,lactose had no significant effect and vegetable oil promoted CML.The addition of minerals alone led to an increase in the proportion of PUFA and promoted the formation of α-dicarbonyl compounds,but inhibited the accumulation of other MRHPs.The effect of vitamins alone was similar to that of minerals,promoting the formation of carbonyl compounds such as DA,GO and HMF,but showing some inhibition of late stage products such as CML and CEL.(4)A GA-BP neural network was established to predict the MRHPs and apply to infant formula.For the connection between the raw materials of formula milk powder and the MRHPs,the commercially available formula milk powder ingredients were used as the input layer and the single MRHPs as the output layer,and the GA-BP neural network was designed using Matlab software to establish a prediction model based on the genetic algorithm optimised BP neural network.The correlation coefficients and error results showed that the model was relatively stable,except for the MGO,GO and CML The correlation coefficients and error results showed that the model was stable,except for MGO,GO and CML,whose prediction success rate was low and needed additional sample size for training,the prediction results of other harmful products basically met the requirements. |
