Microbial Quality and Histamine Producing Microflora Analysis of the Ice Used for Fish Preservation

The aim of the present study was the estimation of the microbiological quality of ice used for fish preservation. Samples of flake ice, produced either from potable or seawater were collected monthly during a 12 month period and were examined for total heterotrophic count (THC) at 37°C and 5°C, total and fecal coliforms, enterococci, Pseudomonas spp., staphylococci, fungi, Vibrio spp., and histamine producing bacteria (HPB). THC at 37°C was higher than the IPIA limit in 15% of the samples (9/60). In 91.67% of the samples (55/60) at least one fecal coliform colony was counted, with three of them (5%) exhibiting counts larger than 100 CFU/100g. All samples tested positive for enterococci, with 6 samples (10%) exhibiting counts greater than 100 CFU/100g. From the 282 isolates characterized as HPB, 24.10% were Pseudomonas spp. (n = 67), 20.86% belonged to Enterobacteriaceae (n = 58) and 19.42% were Staphylococcus spp. (n = 54). Therefore, the ice used for fish preservation can be a potential source of microbial contamination, particularly of HPB; ice production from safe potable water should be practiced in order to safeguard public health. Practical Applications Ice is used extensively for fish preservation, providing an easy and cost effective way to control temperature of stored fish. Ice is a possible vehicle of pathogens contaminating the fish. The present research provides insight in the potential microbial contamination of fish by ice. Factors such as the nature of the water (potable water, seawater) used for ice production and the ice production process (small scale production at the retail store, production in an ice facility) were examined. Also, the involvement of ice as source of histamine producing bacteria was assessed based on the isolation, identification and enumeration of histamine producing bacteria in the examined ice samples. Therefore the results of this study provide useful data that can be applied to minimize the microbial burden of fish due to contaminated ice, to lengthen fish storage life and to avoid pathogen transmission to the consumers.