Application of ozone as a disinfectant for commercially processed seafood

Graduation date: 2003Pacific oysters (Crassostrea gigas), Alaska pink salmon (Oncorynchus\ud gorbuscha) roe and chum salmon (Oncorynchus keta) fillets were treated with\ud aqueous ozone in both pilot plant and commercial settings to determine its effect on\ud shelf-life and microbial changes. The microbial quality was analyzed by conducting\ud pyschrotrophic and coliform plate counts on 3M petrifilm. Oxidative rancidity, pH\ud and moisture were measured during the shelf-life study to determine the effects of\ud ozone on quality. Concentrations of 0.5-1.3 ppm of ozone were applied for periods\ud of 30 s, 1, 2 and 4 min at 5°C, 9°C and 15°C to determine an optimum ozone\ud concentration and contact time that would decrease the seafood microbial load and\ud increase shelf-life in the pilot plant studies. Oysters and roe were treated at 15°C\ud and 5°C and fillets were treated at 9°C.\ud There where only minor microbial differences between ozonated and non-ozonated\ud samples. Treatment temperatures rather than treatment types affected the\ud microbial load. The pilot plant experiments at 15°C and 5°C showed 1 log\ud decrease in oysters and roe treated with aqueous ozone at variable concentrations.\ud No increase in shelf-life was observed when salmon fillets were treated with\ud aqueous ozone (1.3 ppm) for 2 min. Bacteria strains were isolated from treated (ozone\ud and water) and control salmon fillet groups at 0, 5 and 10 days of storage and identified\ud using the API20 NE system. The microbial change in the fillet flora did not differ between\ud ozonated and non-ozonated treatment groups. Gram-positive bacteria were predominant\ud in all groups at day 0, Pseudomonas flunrescens and P. putida were the predominant\ud bacterial species found from all groups at days 5 and 10.\ud Aqueous ozone (0.5-1.7 ppm) was applied in a commercial Ikura roe processing\ud facility. A decrease in the microbial load was seen in the pre-processed samples which\ud were ozonated with eggs in the skein. There were no differences in microbial loads from\ud the non-ozonated and ozonated post-processed samples of individual eggs removed from\ud the skein