The Research On The Exposure Of Bacillus Cereus In Dairy Products

Bacillus cereus is widely distributed in soil, dust and water, and is also common in many plant foods and raw and cooked foods.Bacillus cereus is an aerobic gram-positive spore that can form bacilli can, and under the opposite condition, as surrounding anaerobic atmosphere, it still can grow vividly As a common source of pollution, bacillus cereus is a condition of the pathogen that results in food poison.The main pathway of Bacillus cereus contaminating the infant formula is:contamination brought by the ingredient, secondary contamination after the sterilization, and contamination before feeding.In this thesis, a research about distribution of Bacillus in the dairy production, taking four main kinds of dairy production as subjects-milk powder, pasteurized milk, ultra high temperature sterilized milk and yogurt, presents the contamination of Bacillus cereus in HACCP of dairy production by using statistics theory, which is significant for the protection and guidance of milk production; the related study about dairy procession and storage of Bacillus cereus theoretically offers a basis on stability and safety production of dairy products.The conclusions of this thesis are as follows:1、Qualitative test of32batches HACCP of milk powder, under four conditions-after concentration, spraying dryness, fluid bed and finished, shows the Bacillus cereus contamination rates are0%,12.5%,6.25%and7.81%respectively.2、The simulation test of Bacillus cereus contaminating milk powder finds that the contents of Bacillus cereus from the start, the fist month, the secondare23.1cfu/100g,9.1cfu/100g,3.6cfu/100g. The test result in the third month is less than3cfu/100g, and the result after the sixth month is less than1cfu/100g from the small proportion of the sample.3、The investigation on the contamination of Bacillus cereus in the HACCP of yogurt come out with that the contamination rates of Bacillus cereus are15.63%in the fresh milk,18.75%after mixing materials,9.38%after pasteurization (88～94℃,300s), and3.13%after filling.4%The simulation test of Bacillus cereus contaminating yogurt at37℃presents 15cfu/100mL from the start,5.6cfu/100mL on the third day,2.54cfu/100mL on the fifth day, and0.8cfu/100mL on the seventh day. The results of less than0.3cfu/100mL both are calculated on the fourth and the twenty first.5%The investigation on the contamination of Bacillus cereus in the HACCP of pasteurized milk reveals that the contamination rates of Bacillus cereus are9.38%in fresh milk,12.5%after mixing materials,25%after pasteurization (88～94℃,300s), and21.88%after filling, from which31samples contenting Bacillus cereus of less than10cfu/g account for96.9%and only one sample of between10cuf/g and100cuf/g accounts for3.1%.6、The research about the contamination of Bacillus cereus in the HACCP of ultra high temperature sterilizing milk displays that the contamination rates of Bacillus cereus are21.88%in fresh milk,12.75%after mixing materials,12.5%after pasteurization (88～94℃,15s), and0%after filling.7、The simulation test of Bacillus cereus contaminating yogurt receives that at37℃the rates of Bacillus cereus in samples are14cfu/100mL from the start,39.7cfu/100mL on the third day,23.1cfu/100mL on the fifth day,21.2cfu/100mL on the seventh day.