Study On The Influencing Factors Of Pasteurized Milk Quality

Pasteurized milk is a kind of liquid product which is made from raw cow(sheep)milk by pasteurization and other processes.The good quality of pasteurized milk is affected by many factors,among which the closely related factors are: feed formula,feeding environment,seasonal factors,tank cleaning,raw milk storage time,pasteurization and pre pasteurization process,filtration process,product storage conditions,etc.This experiment mainly studied the effect of different pasture conditions,production process conditions and storage conditions on the quality of pasteurized milk,the results are as follows:1.Study the effect of different pasture conditions on raw milk quality,the results show :On the basis of the daily diet,adding 1 kg of cottonseeds / head / day,the number of alfalfa grasses is not limited,the milk protein and milk fat in cow's milk are improved to varying degrees,the milk fat content is increased by 1.3% to 3.3%,milk The protein content increased by 0.9% to 2.3%,indicating that the addition of alfalfa and cottonseed to the feed significantly improved the quality of raw milk.Compared with the natural ventilation and fan cooling method,the temperature and humidity index decreased by 3.3% to 12.0%,and the monthly output of single cattle increased by 7.4% to 15.6%,indicating that the cooling method of fan and spray Increased the yield of raw milk.Different seasons have a significant impact on milk quality.The experiment found that the total number of colonies,somatic cells and aerobic spores in the milk from January to July showed an upward trend;from August to December,the total number of colonies,somatic cells and aerobic The total number of spores is showing a downward trend.Therefore,during the hot season,the pasture should take strict control measures at all links to control microbial indicators and produce good quality raw milk.Compared with once / 48 h and once / 72 h,once / 24 h is the best way to clean the farm storage tank.At this time,the microbial residue in the farm storage tank is not detected,which should be used in actual production.2.Study the effect of different production process conditions on pasteurized milk quality.The results showed that when the pre storage time of raw milk was less than 8h before use,there was no effect on the quality of milk.When the pre storage time was more than 8h,the total number of colonies,aerobic spores and psychrophilic bacteria in raw milk increased significantly(P<0.05),so the storage time of raw milk in the processing plant should not exceed 8h.After comparing four pasteurization temperatures(75?,80 ?,85?and 95?),the total number of colonies decreased gradually,and the total number of colonies after pasteurization was controlled within<100cfu/ml;the retention values of lactoferrin and ?-lactoglobulin in pasteurized milk were the highest at 75?,and the retention values were 68.3mg/l and 5020.6mg/l respectively,so 75? and 15 s were selected as the best pasteurized milk technology.After the raw milk is filtered,the impurity degree of pasteurized milk with secondary filtration is 0.50mg/kg;the impurity degree of pasteurized milk with three filtration is 0.25mg/kg,so the raw milk should be filtered three times,with the best quality.Compared with pasteurized milk without prepatakill,the content of furosine in pasteurized milk without prepatakill was 5.0mg/100 g.The retention values of ?-lactoglobulin and lactoferrin in pasteurized milk without pre pasteurization were 1132.5mg/L and 66.1mg/L higher than those in pasteurized milk with pre pasteurization,which indicated that pre pasteurization had an impact on nutrients in pasteurized milk.Therefore,in order to ensure the quality of milk,pre pasteurization was not recommended.3.Study on shelf life quality of pasteurized milk with different packaging methods under different storage temperature.The results showed that the total number of colonies of the products packed with pasteurized roof was the lowest(national standard: n = 5 C =2 m=50000CUF/mL M=100000cfu/mL),which was 139.7cfu/ml.During the period of shelf life,pasteurized lactic acid degree did not change.Therefore,it was suggested that pasteurized milk should be stored at 5? and the packaging method was roof packaging.