Discipline: food safety; Key words: Bacillus cereus, spores, Extended Shelf Life milk, CIP, heat and chemicals, biofilms.
It is known that Bacillus cereus spores are resistant to heat and chemicals, and can attach and form biofilms on stainless steel surfaces. B. cereus have been found in the aseptic Extended Shelf Life (ESL) filler nozzles and could be dispensed into the final ESL milk and multiply at refrigeration temperatures as well as during the distribution chain. This implies that the spores potentially could contribute to the contamination of ESL milk. This was the topic of the study by the authors cited below where the objective was to determine the effect of simulated cleaning in place (CIP) on the germination of B. cereus spores isolated from ESL milk processing.
B. cereus strains were isolated from filler nozzles and raw milk. Following isolation, spores were subjected to simulated CIP processes. Flow cytometry and epifluorescence microscopy were used to analyse physical characteristics of spores following the CIP treatment. Biofilm formation and growth kinetics were also determined.
Cleaning in place treatment damaged at least 98% of all spores in all three B. cereus strains, but more than 1% remained intact. These spores were still capable of germination, regrowth and biofilm formation, but strains varied in terms of response to treatment. It was therefore concluded that CIP treatment is not entirely effective and that the final ESL milk product could become contaminated to the detriment of shelf life.
C. Kruger and E.M. Buys, 2018. Effect of simulated Cleaning In Place on the germination of Bacillus cereus spores isolated from Extended Shelf Life milk. In: Proceedings of the 51st Annual Symposium of the SASDT, 24-25 April 2018, Kievits Kroon Country Estate, Pretoria.