Abstract

To assess the adherence of bacteria in stainless steel used in food processing, we developed an experimental model of a milk circulation line equipped with coupons T, 90° (elbow) and cylindrical-shaped constructed AISI 304 stainless steel. We evaluated the adherence of Enterococcus faecium, Pseudomonas aeruginosa ATCC 15442 and Bacillus cereus NCTC 11145 in vegetative and spore forms, before and after milk circulation in the model. The micro-organisms were activated (35°C/12 h) in MRS to E. faecium and B. cereus and nutrient broth for P. aeruginosa and were used to inoculate milk so as to obtain a count of 1.0 x 10⁶ CFU/ml and placed within the test coupons in order to fill them and subsequently incubation was performed at 18°C/12 h. It was concluded that percentages of adherent bacteria before milk circulation were significantly different (p<0.05) that is 13.6% for the B. cereus spores that adhered, 6.0% for the P. aeruginosa, 1.28% for vegetative and spore forms of B. cereus and 0.31% for E. faecium. There was no significant difference (p≥0.05) between the micro-organisms that remained attached after the milk circulation. There was significant difference in removing bacteria, among coupons proof. No coupon T removal was higher than in cylindrical, probably due to the higher turbulent flow, whereas in the later, there is greater tendency of bacteria still attached.

Key words: Milk, adhesion, bacterium, biofilm.