Cardiff Metropolitan University
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Microbiological risks associated with hot-drinks vending

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posted on 2022-10-14, 10:39 authored by Andrew Hall

 The UK vending industry has received little microbiological attention. Although reported cases of gastroenteritis related to hot-drinks vending are rare,there is evidence of microbial contamination and one reported outbreak of gastroenteritis concerning consumption of hot chocolate. This thesis examines the microbiologyof hot-drinks vending operations, the effect of commonly used cleaning protocols on the microbial load of vending components and vended hot drinks and assesses the microbiological risks associated with hot-drinks vending machines. A survey of vending operators identified three main cleaning methods. Laboratory validation of these methods was conducted using vending machine mixing bowls, artificially soiled with hot chocolate powder and Bacillus cereusor Staphylococcus aureus. Detergent, detergent/sanitiser and dishwasher protocols allachievedsignificant(ANOVA, p<0.05),3 log reductions. No significant (Tukey‟s pairwise comparison, p<0.05) difference was observed between the protocols. The development of a microbial population within a commercial hot-drinks vending machine was investigated.The machine vended ≥50 hot chocolate drinks per day over 19 weeks andwas cleaned using a weekly, detergent-based protocol. Over the first 7–10 weeks a significant (ANOVA, p<0.05) increase in the microbial load of the mixing bowl, dispense point and vended drink was observed, reaching a „quasi-steady state‟ until the end of the study. Weekly cleaning significantly (ANOVA, p<0.05) reduced the microbial load of the mixing bowl and drink. The microbial load of the drink showed no reduction over nine minutes after vending, suggesting only spores were present. B.cereuswas identified using biochemical methods. The presence of B.cereusin the vending powders, machine components and drinks was confirmed using aPolymerase Chain Reaction based assay. Of the 291 isolates tested, 90% were confirmed as B.cereus. Random Amplified Polymorphic DNA analysis indicated that the primary source of contamination in the vended drinks was the drinks powder. However, some isolates were identified within the drinks that were found on the machine components but not the powders. A  microbiological  risk  assessment  found  the  risk  of B.cereusgastroenteritis associated with  consumption  of  vended  hot  chocolate  was  low,  providing  machines  are  maintained appropriately.  



  • School of Sport and Health Sciences

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  • Doctoral

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  • PhD

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