Purpose: This study evaluated the microbiological quality of ice produced at retail outlets and in self-service vending machines in Georgia and compared the quality to industry standards for manufactured ice.
Methods: Packaged ice samples (250 bags) from retail locations throughout Georgia that produced and bagged ice on-premises, from self-service vending machines and packaged ice samples (25 bags) from two manufacturing plants were analyzed for heterotrophic plate counts, total coliforms and E. coli, and enterococci. To test for Salmonella and Listeria monocytogenes, melted ice was membrane filtered (45 µ) and any Salmonella or L. monocytogenes trapped on the filter was enriched in universal pre-enrichment broth before plating onto selective agar plates. Confirmation tests were done for presumptive positives.
Results: Of the total retail and vending machines samples, 6.4% contained unsatisfactory levels of heterotrophs according to the limits set by the IPIA (<500 CFU/100 ml). Twenty-six percent of all samples contained unsatisfactory levels of coliforms (<2.2 MPN/ml). E. coli and enterococci were present in 1.2 and 13.2% of the samples, respectively. One sample tested positive for Salmonella, but no L. monocytogenes was found. Samples from the manufacturing plants were well within the IPIA microbial limits.
Significance: Ice made and packaged on-site at retail outlets and in self-service vending machines is not subject to the microbial standards established by IPIA, unlike the two ice manufacturing plants. The presence of microorganisms in samples from retail and vending sites at levels exceeding those established indicates the need for greater sanitary oversight for these segments of the ice industry.