Microbiological quality of packaged ice from various sources in Georgia

This study determined the microbiological and chemical quality of ice produced and bagged on premises in retail establishments and in free-standing self-service ice vending machines in the state of Georgia and compared the results with that from ice produced by manufacturing companies monitored by the International Packaged Ice Association. Two hundred fifty bags of packaged ice samples were obtained from retail locations and self-service ice vending machines, along with 25 bags of packaged manufactured ice. Ice samples were melted within 24 h of collection and heterotrophic plate count SimPlates were used to detect heterotrophic bacteria present. Colisure and Enterolert assays were used to enumerate coliforms, nonpathogenic Escherichia coli, and enterococci. Membrane filtration coupled with enrichment was used to detect Salmonella and Listeria monocytogenes. Confirmation tests were done for presumptive-positive pathogens. None of the manufactured ice had unacceptable microbial levels. Six percent of the ice samples bagged at retail sites and from ice vending machines contained unsatisfactory levels of heterotrophs compared with the limits set by the International Packaged Ice Association (≥ 500 most probable number [MPN]/100 ml). Thirty-seven percent of these samples contained an unsatisfactory level of coliforms (≥ 1.0 MPN/100 ml), 1% contained nonpathogenic E. coli, and 13% contained enterococci (≥ 1.0 MPN/100 ml). One sample tested positive for the presence of Salmonella and another tested positive for Enterobacter agglomerans. Ninety-five samples of packaged ice from retail establishments and vending machines (38%) had pH levels outside the acceptable range that can affect product flavor. Turbidity of three samples exceeded the acceptable level. No samples had unacceptable nitrate levels. Manufactured ice had better microbiological and chemical quality than ice packaged on the premises of retail locations and from self-serve ice vending machines.