Research On The Identification Of Quality, Safety And Authenticity Of Dairy Products Based On NMR Technology

At present,chinese dairy industry is facing many problems,such as melamine and other non-protein nitrogen adulteration,low-cost milk adulteration,the lack of nutrients in milk.These issues bring serious harm to human health.Although many detection methods have been established for the adulteration detection in dairy products at home and abroad in recent years,a comprehensive system for dairy quality control has not yet been set up.Therefore,establishing a method for quality and dairy safety testing,authenticity identification,and quality control is essential,in order to eliminate consumers’panic and promote the development of chinese dairy industry.The purpose of this study is to establish a NMR method for quality and dairy safety testing,authenticity identification,and quality control.The details are as follows:(1)A NMR method for simultaneous determination of five non-protein nitrogen compounds,i.e.,urea,melamine,guanidine,biuret,and diaminoguanidine,in milk was developed.All of these non-protein nitrogen compounds can be accurately quantified with recovery between 80%and 110%and relative standard deviation less than 6%using quantitative ~1H NMR method.The limit of quantitation was 2.0 mg/L for melamine and urea,8.0 mg/L for guanidine,biuret,and diaminoguanidine.The endogenous urea content in milk was found and quantified using the established NMR method,and its level varies in milk from different production regions(China,Europe,and Australia).However,the level did not exceed the maximum safe dose(<620mg/L).(2)1D NMR in conjunction with multivariate chemometrics as well as 2D NMR was applied to differentiate the milk types,and to identify milk adulteration.10metabolites were found which differed among milk types hence providing characteristic markers for identifying the milk.These metabolites were used to establish the mathematical model for milk type differentiation.The LOQ of adulteration was 2%for soymilk in bovine milk,2% for soymilk in goat milk,and 5% for bovine milk in goat milk,RSD≤10%,which can meet the needs of daily inspection.It provides an informative and robust technique for verifying milk authenticity.(3)A new approach for determination of lipids in different milk matrix by using ~1H NMR was established.The organic bovine milk,goat milk and soymilk collected from supermarket were detected.It showed that organic bovine milk>goat milk>soymilk forω-3%;goat milk>organic bovine milk>soymilk for DHA%;organic bovine milk>goat milk for EPA%and no EPA in soymilk.Besides,the PLS-DA and ANOVA method were used to further analyze the difference of lipid distribution in the three species of milk and then evaluate the nutrition value.