Investigation Of Quality Of Raw Milk In Ningxia And Establishment Of Detection Method Of Benzalkonium Bromide

The dairy industry is one of the characteristic industries in Ningxia.At present,Ningxia has 600,000 dairy cows on hand,The average output is 7600kg per cow,total milk production reached 2.187 million tons,the average quantity of milk for each person is over 300kg,and all ranks in the forefront of the country.Raw milk components are affected by nutrient intake,drug metabolism,dairy cows' physical condition and human factors.The Occurrence of Two Events,the "Big-headed Doll" in 2003 and the"Melamine" in 2008,Not only endangered the baby's life,but also exposes the phenomenon of inadequate food safety supervision in China,and Revealed the importance of quality monitoring of raw milk.Since then,our country has increased the detection of raw milk quality,thus ensuring the nutrition and safety of raw milk.As an important milk source base,it is particularly important to monitor the quality of raw milk in Ningxia.In this experiment,242 raw milk samples from NingXia were selected in 2017.Two studies were carried out,one is the detection and analysis of raw milk quality,and the other is the establishment of a test method for benzalkonium bromide in raw milk.Test 1:The six indexes of protein,fat,total number of colonies,somatic cell,impurities and relative density in raw milk were measured,Analyzed by season and collection types,the results are as follows:1.The average protein content in raw milk from one to four quarters respectively are 3.27,3.12,3.00,3.24 g/100g.The average fat content in raw milk from one to four quarters respectively are 3.97,3 84,3 64,4.03 g/100g.The average number of bacteria respectively are 3.2 X 104,8.7×104,21.7×104,7.8×104cfu/mL.The average number of somatic cell respectively are 23.4 X 104,19.7×104,25.7×104,17.4×104cell/mL.The relative density and the impurities are in line with national standards.In summary,the seasonal impact on raw milk quality was significant,and the raw milk quality was higher in the first and fourth quarters than in the second and third quarters.2.The four indexes protein,fat,total number of colonies and somatic cell in raw milk,The average number of Dairy producers are 3.19g/100g,3.97g/100g,16.8×104cfu/mL,20.8×104cell/mL.The average number of Dairy farmers are 3.14g/100g,3.86g/100g,10.6×104cfu/mL,20.0 × 104cell/mL.The average number of Dairy farmers'cooperatives are 3.16g/100g,3.85g/100g,8.5 × 104cfu/mL,23.3 × 104 cell/mL.There are two cases of total number of bacteria were seriously outliers in Dairy producers,Caused its average level too high.Therefore,these two cases should be excluded from the analysis.In summary,The quality of raw milk produced by Dairy producers was slightly better than that of the other two types of acquisition stations,but the overall difference between the three types of acquisition stations was not significant.3.Compared with other countries,the milk fat,colony count,and somatic cell level in Ningxia are comparable to those in other countries,but the milk protein content is significantly lower than other countries.Test 2:A HPLC method for the determination of benzalkonium bromide in raw milk was established.After the raw milk was precipitated with acetonitrile,take the supernatant water bath to evaporate,and then reconstitution with 1 mL of mobile phase,Filter with 0.4?m membrane,For liquid chromatography detection.In this method,benzalkonium bromide can be separated within 15 min without interference of impurities.The limit of detection was 5.5?g/mL,the limit of quantitation was 18.05?g/mL,the recoveries were between 71.74%?100.41%,and the relative standard deviation less than 8.02%.This method has good selectivity,high sensitivity,simple pretreatment method and high recovery rate,meet the test requirements of benzalkonium bromide in raw milk.