Analysis On The Changes Of Nutrients And Volatile Components During The Storage Of Formula Milk Powder

Formula milk powder is rich in nutrients such as fat,protein,vitamins and minerals,which can meet the nutritional needs of specific people.However,during storage,these nutrients are easily affected by many factors such as oxygen,temperature and humidity,resulting in oxidative decomposition of fat,degradation of protein and vitamins,resulting in deterioration of nutritional quality and flavor of milk powder.In order to explore the nutrient loss and flavor change of formula milk powder during normal temperature and accelerated storage,this paper takes the newly developed infant formula milk powder（stage I,ⅡandⅢ）and middle-aged and old-aged formula milk powder of a certain brand as the research object,and analyzes and determines the main nutritional components and volatile substances under the conditions of open cover normal temperature（25±1℃）and accelerated test（sealed 45±1℃）,The research results provide theory and basis for guiding the nutrition and flavor loss of formula milk powder during storage.The main results are as follows:（1）The decay rate of protein,fat,docosahexaenoic acid（DHA）,arachidonic acid（ARA）and carbohydrate in stage I,ⅡandⅢformula milk powder after storage for 150 days is less than the detection precision of each nutrient,so the three milk powders can be stored well within 150 days at room temperature with the lid opened.Among the middle-aged and old-aged formula,only the decay rate of Ara after storage（11.93%）exceeded the detection precision,and the milk powder was well preserved within 60days at normal temperature after opening the lid.In the accelerated storage process,the protein,fat,DHA,Ara and carbohydrate of stage I,ⅡandⅢformula milk powder showed good stability within the shelf life of 600 days,while only ARA attenuation rate of middle-aged and old-age formula milk powder was higher than the detection precision,which was 12.64%.Therefore,the nutritional elements such as protein,fat,DHA,ARA and carbohydrate in the middle-aged and old-age formula milk powder have good stability within 360 days of shelf life.（2）After the stage I milk powder is stored at room temperature for 150 days,the attenuation rates of vitamin A,C,B₂and K₁are 14.88%,6.02%,5.10%and 8.84%respectively.Among them,if the attenuation rate of vitamin A exceeds the detection precision,the vitamin content of the stage I milk powder is relatively stable within 30 days after the cover is opened at room temperature.Similarly,the vitamin content of the stageⅡ,Ⅲand middle-aged and old-aged milk powder is relatively stable within 30 days after the cover is opened.In the accelerated storage process,by accelerating the simulated normal temperature shelf-life storage,the attenuation rates of vitamin A,C,B₂and K₁in stage I milk powder are14.56%,16.73%,4.32%and 11.2%respectively.Among them,the attenuation rates of vitamin A,C and K₁exceed the detection precision,so the vitamin content of stage I milk powder is relatively stable within 120days of shelf-life.Similarly,the vitamins in stageⅡ,stageⅢand middle-aged and old-aged milk powder are relatively stable within 480 days of shelf-life Good stability was maintained within 120 d and 360 d.（3）After the infant and middle-aged formula milk powder of stage I,ⅡandⅢis stored at room temperature and accelerated for 150 days,the decay rate of each mineral is less than the detection precision,which proves that the content of this kind of nutrient elements is relatively stable during storage.The mineral content of the four types of milk powder was relatively stable within 150 days after opening the lid or within 600 days of shelf life.This is related to the tolerance of minerals to air,temperature,light and other factors.（4）Solid phase microextraction gas chromatography mass spectrometry was used to separate and detect the volatile components of three types of infant formula milk powder and middle-aged and old formula milk powder in normal temperature and accelerated storage period.It was found that the volatile components of four types of milk powder mainly include ketones,aldehydes,alcohols and acids.After 150days storage at room temperature,the aldehydes in stage I and middle-aged and old-aged formula milk powder have a downward trend,mainly including benzaldehyde,n-hexanal,（E）-2-octenal,（E）-2-heptanaldehyde and other volatile components.After the end of storage period,the total content of aldehydes in stageⅡand stageⅢformula milk powder shows an upward trend,among which,valeraldehyde,2-hexenal and n-octanal increase significantly,The proportion of total relative content of alcohols decreased.Under the accelerated test conditions,with the increase of days,the total content of aldehydes and volatile substances in the four formulas gradually decreased,and the total content of alcohols gradually increased.Through the determination of 10 special flavor compounds such as n-hexanal,benzaldehyde,pentanal,（E）-2-heptanaldehyde,2-hexenal,n-octanal,（E,E）-2,4-heptadienaldehyde,2-heptanone,1-penten-3-alcohol and butyric acid,it was found that the aroma threshold（ROAV）values were different,but n-hexanal was one of the main key flavor compounds;At the same time,benzaldehyde,valeraldehyde,（E）-2-heptanaldehyde played an important role in modifying the overall flavor（0.1≤ROAV<1）.