Combined effect of ozonated water and chitosan on the shelf-life of Pacific oyster (Crassostrea gigas)

Effects of ozonated water and chitosan treatment on the shelf-life extension of Pacific oysters (Crassostrea gigas) stored at 5 +/- 1 degrees C were studied. Results indicated that ozonated water treatment reduced the total microbial load of fresh oysters by about 10-fold (from 3.2 x 10(3) CFU/g to 1.8 x 10(2) CFU/g) before storage and the microbial flora was different with that of raw samples. The wide-spectrum antibacterial property of chitosan against bacteria isolated from oysters was confirmed, and chitosan concentration of 5.0 g/l was eventually determined for application in oyster preservation. Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-lives of 8-9 days for control, 10-12 days for ozonated water treated samples, 14-15 days for chitosan treated samples and 20-21 days for samples with combined treatment were observed, indicating that ozonated water and chitosan have a great potential for oyster preservation. Industrial relevance: As seafood, Pacific oysters have a short shelf-life. Improvements in the shelf-life of oysters can have an important economic impact by reducing losses and by allowing the products to reach distant and new markets. In this work, Shelf-life of oysters with combined treatment of ozonated water and chitosan doubled, which has great practical meaning, and the process could be fully adopted by the food industry. We also did some research about the changes in microbial flora after ozonated water treatment. This work could help in preservation of oysters when ozone or ozonated water concerned. We discovered Wide-spectrum antibacterial property of chitosan against the strains isolated from raw oysters. The potential for using chitosan as a natural preservative in oysters was approved. (C) 2009 Elsevier Ltd. All rights reserved.