Screening Of Milk Spoilage Markers Based On Free Amino Acids And Biogenic Amines

Dairy products are one of the main sources of animal protein consumed by human.As one of the key indictors of milk quality,milk freshness directly impacts the health of consumers.The establishment of fast,effective and objective dairy freshness evaluation technology is extremely significant for the modern dairy industry.The aim of this paper was to speculate on the possibility of free amino acids and biogenic amines in protein degradation products as markers of spoiled milk with a view to providing a reliabletheoretical basis for further researchthe quality of milk.The research contents and results are as follows:(1)A method for determining of underivatized free amino acids and biogenic amines in milk was developed withultra-high performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS).The sensitivity and accuracy were improvedby optimizing the mass condition,chromatographic condition,pretreatmentmethod.The results indicated that good separation of all the analytes was obtained within 14 min.The correlation coefficient was in the range of 0.9907~0.9996 for FAAs and 0.9944~0.9998 for BAs.The average recoveries and relative standard deviations of FAAs and BAs at three spiked levels were in the range of 68%~134% and1.81~26.33% respectively.The proposed methodwas shown to be specific,accurate and efficient,and suitable for the simultaneously quantitative analysis of underivatized free amino acids and biogenic amines in milk.(3)Changes of free amino acids?biogenic aminesand other indexes(sensory evaluation,acidity,fading time of methylene blue)in different milk(raw milk and UHT milk)were studied at different storage temperatures(4? and 20?).It could be concluded that PUT and CAD could be used as the markers for the identification of raw milk in simulated storage environments at 4?,whereas FAA had no significant relation with the degree of milk corruption.