Study On Analytical Technology Of Emulsifiers In Dairy Products And Their Levels Change During Storage

Dairy products are high nutritional components in the human dietary structure.The quality and safety of dairy products are of great significance for guaranteeing the health of consumers and promoting sustainable development of the industry.To stabilize food structure,emulsifiers are often added in the process of dairy products manufacturing.Contents of emulsifiers in dairy products demonstrate a certain influence on the stability and quality of dairy products.Therefore,it is essential to study and construct new method of emulsifier analysis in dairy products,as well as to guarantee the quality.In this thesis,the analytical methods was studied and constructed for monoglycerol fatty acid esters and diglycerol fatty acid esters in dairy products based on gas chromatography-mass spectrometry and liquid chromatography analytical techniques.The new methods also probed into the variation of aforementioned emulsifier levels during the storage of dairy products and achieved satisfactoy results.The main research results are as follows:1.A new method for simultaneous analysis of emulsifiers monopalmitate,monooleate and monostearate in dairy products has been established by using gas chromatography-mass spectrometry(GC-MS).The targets in dairy products were extracted with CH₂Cl₂ and derivatized with a silanization reagent(BSTFA+1%TMCS).Under optimized experimental conditions,glyceryl monopalmitate(1-20 mg/L),glyceryl monooleate(5-100 mg/L)and glyceryl monostearate(10-200 mg/L)possess superior linear correlation(R²>0.992)and the limit of detection(LOD)and limit of quantification(LOQ)were within the range of0.262-1.203 mg/L and 0.873-4.010 mg/L,respectively.The spiked recoveries of the three target analytes in dairy products were 63.5%-111.7%,and the relative standard deviation(RSD,n=6)was less than 3.0%.The established method was finally applied to the determination of glycerol monopalmitate,glycerol monooleate and glycerol monostearate in dairy products including fresh milk and yogurt,which achieved satisfactory results.2.A new method for the determination of the emulsifiers,including dilinoleic acid glyceride,1,3-dipalmitoic acid glyceride and 1,3-dihardened in dairy products were sysmatically studied by Ultra Performance Liquid Chromatography-Evaporative Light Scattering Technology(UPLC-ELSD).The target substances in dairy products were extracted with acetone.Under optimized experimental conditions,glyceryl dilinoleate,glyceryl 1,3-dipalmitate and glyceryl 1,3-distearate possess good linear correlation within the range of 10-100 mg/L(R²>0.997),LOD and LOQ were within the range of 3.15-3.19 mg/L and 10.30-10.50 mg/L,respectively.The recovery rate of above target analytes in dairy products were 72.5%-127.5%,and the RSD(n=6)was less than 6.0%.The established method was applied to analyze glyceryl dilinoleate,glyceryl 1,3-dipalmitate and glyceryl 1,3-distearate in dairy products and achieve satisfactory results.3.The above-constructed analytical technology were applied to study the variation of some typical emulsifiers(including glycerol monopalmitate,glycerol monooleate,glycerol monostearate,glycerol dilinoleate,1,3-dipalmitate and1,3-distearate)during storage.Meanwhile,p H and UV-Vis spectrum changes of dairy products have also been explored.The results show that the content of mono-and di-glycerin fatty acid esters changed slightly over time during the storage.The p H value were stable all the time.On the other hand,with the extension of storage time,the intensity of ultraviolet light absorption at 280 nm of various brands of dairy products demonstarte a significant difference.