Research Of Lactulose In Milk And Development A New Detection Method Of Lactulose

Under the different conditions of storage and transportation,the change of the lactulose concentration in raw milk and UHT milk is researched in this study.And it also been discussed about the effect of different heat treatment conditions on the concentration of lactulose.Meanwhile,because of the complexity of the existing lactulose detection methods,a new method which use supercritical fluid chromatography to detect lactulose in milk is developed,the aim of this study is to provide the basis for the further research.Experiment 1:In the extreme storage and transportation conditions,to research the change of the lactulose concentration in raw milk and UHT milk by simulating limit transportation temperature?65??and transportation time?0h,5h for raw milk;0h,5h,10h,20h for UHT milk?.These conditions are simulating the container transportation of commercial milk on the highway in the hot summer.The results showed that keeping milk samples in these conditions,lactulose contents in raw milk are markedly increased.In UHT milk,lactulose contents also have obvious increasing trend,and the lactulose contents increased with the increase of time.Experiment 2:This experiment is researched the effects of different heat treatment milk on the concentration of lactulose.Change the conditions through change heat treatment temperature and heat treatment time.Raw milk samples were heated under 60?,65?,70?,75?,80?,85,90,95,100?,105?,110?,115?,120?for 15s,and under 135?,137?,139?,141?,143?,145?for 5 s.Then,used the raw and processed milk samples to detect lactulose.The results showed that,when the temperature was below 95?,the contents of lactulose are rise slowly.Between 95?and 120?,lactulose contents rise obviously.And when the temperature between 135?and 145?,and keep 5s,a significant increase in the concentration of lactulose was shown.Experiment 3:The aim of this study is to adapt the supercritical fluid chromatography?SFC?method for determination of lactulose content in commercial samples of raw milk,pasteurized milk,UHT milk and condensed milk.In this work,a new method for the rapid determination of lactulose by SFC coupled with mass spectrometry is presented.The developed method is based on methanol:acetonitrile?1:3,v/v?precipitation followed by a SFC separation on a Torus Diol Column?130?,1.7?m,3 mm×100 mm?,using a gradient elution of supercritical CO₂ and methanol/water?100/3,v/v?with 0.1%ammonia as the mobile phase at 1.4 ml/min flow rate.The back pressure was set at 2200 psi.The MS analysis was performed using selected ion recording mode.The linearity test for the quantitation of lactulose has been carried out over the range 0.1–10.0 mg/L,R²=0.9992.the limit of detection is 0.03 mg/L,and the limit of quantitation is 0.1 mg/L.The proposed method,simple,cheap and time-saving,allows an accurate lactulose–lactose separation,with the novel SFC equipment.And it was successfully applied to the quantification of lactulose in commercial milk products.