Quality Evaluation And Monitoring Of Sterilized Milk And Fresh Milk On The Market In Shihezi Area

Milk is a kind of nutritionally high-quality and comprehensive animal-origin food,containing water,fat,phospholipid,protein,lactose,inorganic salt and other main ingredients.Due to high nutritional value,rich mineral types,reasonable ratio of calcium and phosphorus,and necessary amino acids that synthesize human protein,milk is known as"white blood".Therefore,the quality of milk is closely related to the above nutrient contents.At present,the quality and safety assessment of milk mainly depends on physical and chemical indexes and hygiene indexes,among which physical and chemical indexes mainly include protein,fat,non-fat milk solids,acidity,etc.Health indicators are consisted by total number of bacteria,number of somatic cells,veterinary drug residue,heavy metal residue and pesticide residue.Because of its rich nutrients,milk is also a good medium for microbial reproduction,especially when cows are infected with bacteria and transported during milk production,and the storage link is also highly susceptible to bacterial contamination.In recent years,food safety incidents occur frequently,especially the quality problems of dairy products account for a large proportion.Xinjiang is an important milk source in China.However,the quality evaluation and monitoring data of sterilized milk and fresh milk in the market are not comprehensive.In view of this,sterilized milk and fresh milk collected from Shihezi area of Xinjiang,the main nutrients(fat and protein),evaluation index(non fat milk solids and acidity),microbial content,aflatoxin M1 and dexamethasone residues testing were determined according to the national standard method in this study,and then the comparative analysis of the sterilized milk and fresh milk was evaluatd according to qualified rate,which lay a foundation for the monitoring of milk and dairy products in the Shihezi region of Xijiang.The main methods and results are as follows:1.Physical and chemical indicators of sterilized milk and fresh milk detection fromShihezi regionTo monitor the quality of milk and dairy products quality in Shihezi area of Xinjiang,sterilized milk and community and farmers,farm fresh milk were collected from supermarkets,shops,market selling point,in Shihezi.The main nutrients(fat and protein),evaluation index(non fat milk solids and acidity)were determined in this experiment,respectively.The results showed that protein?2.9g/100g,fat?3.1g/100g,non-fat solid?8.1g/100g and acidity of 12°T?18°T of the 60 batches of sterilized milk all reached the quality evaluation standard of liquid milk,that is,the reaching rate was 100%.The protein,fat,non-fat milk solids and acidity of 40 portions of fresh milk were 90%(36/40),70%(28/40),60%(24/40)and 100%(40/40),respectively.The results indicated that the physical and chemical indexes of sterilized milk in Shihezi area were all up to the standard,and the quality was better than that of fresh milk.2.Microbial detection of sterilized milk and fresh milk from Shihezi regionAccording to the state standards of GB 4789.2-2016,GB 4789.3-2016,GB 4789.4-2016and GB 4789.10-2016,the total number of bacterial colonies,Coliforms,Salmonella and Staphylococcus aureus were detected,respectively.The results showed that any bacteria were detected in all the 60 samples,that is,the qualified rate of bacterial colonies,Coliforms,Salmonella and Staphylococcus aureus was 100%.The total bacterial colonies of 40 fresh milk were?2.0×10~6CFU/m L,25%(10/40),?5.0×10~5CFU/m L,10%(4/40),and the bacterial colonies of Coliforms were?10~3CFU/m L,12.5%(5/40),respectively.The microbial detection of Salmonella and Staphylococcus aureus was negative,respectively,which means the qualified rate was 100%for the sterilized milk.However,Coliforms were common in the fresh milk.3.Detection of major risk factors of quality and safety of sterilized milk and fresh milk from Shihezi regionAflatoxin toxin M1(AFTM1)and dexamethasone are important risk factors in milk and dairy products.In this study,all samples were detected according to GB 5009.24-2016and GB/T22978-2008 respectively.The results showed that AFTM1 and dexamethasone were not detected in 60 samples of sterilized milk,that is,the detection rate was 0%and the pass rate was 100%.One sample of 40 fresh milk samples was found to contain AFTM1(content0.90 g/kg?0.50g/kg).The detection and pass rate was 2.5%(1/40)and 97.5%(39/40),respectively,while the detection and pass rate of dexamethasone was 0%and 100%,respectively.This indicates that aflatoxin contamination exists in farms in this area,whereas dexamethasone has no residue.