Study On The Mechanism Of Moderate Heat Treatment On The Production Of Furosine And Freshness Control In Milk

Heat treatment is a common method to ensure the safety of microorganisms and shelf stability in milk,but different degrees of heat treatment will cause many chemical and structural changes in milk,the degree of which depends on the temperature and duration of heating.One of the harmful consequences of heat treatment is the Maillard reaction,which leads to a reduction in the nutritional value of the protein,a change in taste and flavor,and the formation of brown compounds in milk.The degree of reaction can be achieved by measuring the content of furosine,which is a useful indicator of cow’s milk heat damage and can be used to distinguish whether there is excessive heating of milk or reconstituted milk with added milk powder.Therefore,this study explored the production rule of furosine and its flavor quality and stability during storage by establishing a lactose-lysine simulation system and through different degrees of low heat treatment of raw milk.With a view to improving the safety of milk and ensuring the nutritional quality of dairy products.The main research results of this paper were as follows:1.For the purpose of high-efficiency,rapid and accurate detection of furosine in milk and improving the detection accuracy,we optimized the use of liquid-mass spectrometry in the experiment.The results showed that furosine had a good linear relationship in the range of 0.05~0.80 mg/L,the correlation coefficient(R~2)was 0.9992,and the limit of quantification(LOQ)was 0.0125 mg/L.The average recovery rate of this method is 94.2%,and the relative standard deviation(RSD)is 0.71%.It has high accuracy and reproducibility,and this method was used to detect the content of furosine in the simulated system and fresh milk after heating in this paper.2.The change rule of the production of furosine in the simulation system of milk and raw milk in the process of lactose reaction under low-heat and short-time treatment was studied.The study found that under the same heating temperature,the amount of furosine produced showed an upward trend with time.The rate of rise was relatively fast,then slowly,and then rapidly;under the same heating time(15 s)With the increase of temperature(68℃-80℃),the production of furosine shows an upward trend.The higher the temperature,the more production,and when the heating time is 30 s,the production of furosine is more than 15 s.Under the pasteurization process conditions,the effect of sterilization temperature on the production of furosine is greater than the sterilization time,but the dual factors of temperature and time need to be considered comprehensively.3.The quality and flavor changes of cow milk after different low heat treatments during storage were studied by using electronic tongue,pH meter,color difference meter,infrared,etc.to characterize the changes of milk with different low heat treatments during storage.It was found that during storage,the taste,pH value,color and protein structure of raw milk after different low-heat processing treatments changed.The infrared spectroscopy detection analysis showed that the stability of the milk system is closely related to the heat treatment intensity.The electronic tongue and pH detection analysis showed that the milk flavor will be more clearly distinguished as the storage time becomes longer.4.A total of 5 different substances used to distinguish milk after low heat treatment were found by using high-resolution liquid chromatography-tandem mass spectrometry and time-of-flight mass spectrometry(LC-TOF/MS),triple quadrupole liquid chromatography mass spectrometry combined with liquid chromatography mass spectrometry fingerprint spectroscopy technology and chemometrics and screening characteristic difference substances,after the analysis of variance p<0.05 and VIP(variable importance)value>1 to screen the difference.A discriminant model to distinguish the different low heat treatment cow milk was established.The discriminant model established through the screening of the five different substances can accurately distinguish the milk with different low heat treatments,in order to provide a theoretical basis and technical support for identifying whether there is excessive heat treatment detection.The five characteristic difference substances will need to be qualitatively analyzed later through comparison databases,collection of secondary fragment ion peaks,and matching reference materials,in order to lay the foundation for better identification of different substances in cow milk after different low heat treatments.