Study On Safety Of Raw Materials In Dining Hall Of A University In Zhejiang Province

Over recent years,incidents about food safety in China come out one after another,directly causing not only enormous damage to property,but also a serious threat to the people's health.In addition,these incidents may lead to a series of major social problems,such as a sharp drop of people's happiness.Mess hall is the place for teachers and students to have meals,and the food quality there is directly related to their health.Recently,factors that affect food safety are of a diversified and complex trend,the occurrence of food safety incidents,such as “Sanlu Milk Powder”,“Tony Red”,“Waste Oil”,“Chrome Rice”,“Lean Meat Powder”,etc.brings up new requirements to ensure the quality and safety of raw materials in the mess hall.It is of great importance to ensure the normal study,work and life of teachers and students.Thus,it is essential to conduct a comprehensive and in-depth investigation.In this paper,the raw materials in the mess hall of a University of Zhejiang are set as the studying objective.The quality safety of raw materials and other comprehensive aspects are studied in terms of pesticide residues,heavy metals,nitrite,aflatoxin and oil deterioration after frying,etc.,which may provide reference for the quality control of raw materials in the mess hall by university logistics and related department.The contents of this paper are as follows:(1)High performance liquid chromatography.0.1 and 1mg/kg of five pesticides(thiamethoxam,thiophene clothianidin,imidacloprid,acetamiprid,thiacloprid)were added into four kinds of vegetables(potatoes,spinach,celery and tomato)and two kinds of meat(chicken and pork).Study pesticide residues of all samples after the simultaneous treatment of boiling and frying.The results show that except celery,chicken and pork with the addition of 0.1mg/kg imidacloprid,thiamethoxam and thiacloprid respectively and tomato and pork with the addition of 1mg/kg of clothianidin and thiacloprid,the pesticide residue rate of the remaining boiled samples are significantly higher than that of frying samples,indicating that compared with boiling,frying can more effective remove pesticide residues in samples,which may be related to the high temperature in frying process.Moreover,no matter by boiling or frying,pesticide residue rate in processed meat is lower than that in processed vegetables.(2)Apply ICP-MS to confirm the heavy metal elements(As,Cd,Cu,Pb)in raw and cooked vegetables,celery,potatoes and tomato.It is found that the content of Pb in all food samples does not exceed(except raw celery),but the content of As has exceeded(except raw tomatoes);the content of Cd in raw and cooked tomato and vegetables is excessive,and it is not excessive in the other vegetables;as for Cu,no relevant national standards can be found and thus comparison cannot be made.Through the comparison of the four kinds of cooked vegetables,it can be found that the content of As and Pb in potatoes is the highest,and the content of Cd and Cu in Vegetables is the highest;the content of As and Pb in tomatoes is the lowest,the content of Cd in celery is the lowest,and the content of Cu in potatoes is the lowest.(3)UV spectrophotometry is applied.Study the nitrate variation of samples of raw and cooked meat(chicken and pork),and vegetables(cucumbers and spinach)placed at 4,20 and 37? at different times.The results show that: Whether the vegetables are raw or cooked,the nitrite content of all vegetable samples does not exceed after placed for 48 h.Raw chicken at 4,20 and 37? exceeds after placed for42,18 and 12 h and at the same temperature pork shall exceed after placed for 48,24 and 12h.Cooked chicken stands at 4 ? for 48 h,and shall not stand at 20 and 37?,respectively for 24 h and 18h;cooked pork exceed at 4,20 and 37? after placed for48,18 and 12 h.Overall,the low temperature will help slow down the growth rate of the nitrite content;nitrite content in pork is higher than that in chicken;spinach is of nitrate-rich vegetable and its nitrite content is higher than that of cucumber.(4)HPLC is applied to test aflatoxin B1 of rice stored for several different days at 20 ? and 37 ?.The aflatoxin B1 content in rice is of 1.41?g/kg in case of 0d,and the aflatoxin B1 content increases to 1.60?g/kg and 2.21?g/kg,respectively after stored for 15 d and 30 d at 20 ?;and when it is stored for 15 d and 30 d at 37 ?,the rice aflatoxin B1 content increases respectively to 2.23?g/kg and 3.19?g/kg.These results indicate that the aflatoxin B1 content in rice is positively correlated to the storage temperature and time.In addition,no matter at 20 ? or 37 ?,the aflatoxin B1 content in rice for a storage of 30 d is significantly lower than the national limit standard(10?g/kg),and it is safe to eat.(5)Based on sensory evaluation and physical and chemical indicators,study the quality deterioration of edible oil during frying.The results show that: With the prolonging of frying oil,soybean oil quality deteriorates significantly,the color gradually deepen to reddish brown,the clarity level experiences a significant decline,the odor change,viscosity increases,acid value and peroxide value obviously increase,carbonyl base price grows,but the physical and chemical indicators do not exceed the national standard.Thus,the frying technique in the mess hall of Zhejiang University of Technology(5kg of initial oil,125 pounds of fried big row for five-time frying)meets the comprehensive requirements of quality safety and economic efficiency and is trustworthy.