Prevalence of Bacillus cereus s.l. in ultra-high temperature chocolate milk from selected milk manufacturers in Malaysia

Abstract

Bacillus cereus is a major foodborne pathogen of great concern to the dairy industry owing to its resilient spores as well as the adverse effect of its toxins. At present, there is no informational study available to solve or pinpoint the UHT chocolate milk contamination issue in Malaysia. This work aimed to investigate the prevalence and contamination level of B. cereus s.l. in UHT chocolate milk and to suggest the appropriate solution for the issue. In the present study, B. cereus s.l. prevalence and contamination level in individually packed UHT chocolate milk from processing factories was evaluated. The prevalence and concentration of B. cereus s.l. were determined via MPN-PCR (Most Probable Number-Polymerase Chain Reaction) assay. Results showed that 31.11% from 220 of UHT chocolate milk tested contained Bacillus spp.; of this Bacillus spp. positive samples, 24.30% were also positive for B. cereus s.l. with concentration ranging from less than 3 to more than 1100 MPN/mL. Findings from this study highlighted the possibility of UHT chocolate milk as a potential source of B. cereus s.l. infection. Therefore, findings emphasized the needs to revise, monitor and improve UHT sterilization process to reduce infection risk. Furthermore, it is also essential to maintain the hygiene to minimize initial microbial load and contamination of UHT chocolate milk, beginning from production to retail.

Sources, transmission, and tracking of sporeforming bacterial contaminants in dairy systems

“…Once the cocoa nibs enter the manufacturing process to be converted into cocoa powder, there are additional chances for spore contamination to occur. Due to the biofilm-generating ability of common sporeforming bacteria found in cocoa nibs, machinery and other instruments are susceptible surfaces for them to adhere to and contaminate the cocoa powder in the process ( Lima et al, 2012 ; Pereira and Sant'Ana, 2018 ; Ubong, 2020 ). Studies indicate that the mesophilic strains most commonly found in cocoa powder include Bacillus cereus and Bacillus subtilis groups, Bacillus coagulans , Bacillus licheniformis , Paenibacillus , and others, whereas thermophilic strains including Geobacillus pallidus and Geobacillus stearothermophilus are also commonly identified ( Pereira and Sant'Ana, 2018 ), all of which represent quality, and potentially safety, concerns for HTST and UHT chocolate milk products.…”