Effects of ozonation on microbiological, chemical and sensory attributes of vacuum-packaged rainbow trout stored at 4±0.5°C

The effects of ozone in aqueous solution on the shelf life of whole, vacuum-packaged rainbow trout, stored under refrigeration (4±0.5°C) were studied by monitoring the microbiological, chemical and sensory changes for a period of 15 days. Vacuum-packaged non-ozonated trout served as the control sample. Ozonation affected populations of bacteria namely, mesophilic aerobic bacteria, Pseudomonas spp. and H2S-producing bacteria until day 11 of storage, Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae until day 8 of storage. Trimethylamine (TMA) values of all rainbow trout samples remained low (<3 mg N/100 g) until day 11 of storage, and then increased to 12.2, 8.9 and 4.7 mg N/100 g for the control and the samples ozonated for 60 and 90 min, respectively on day 15 of storage. Total volatile basic nitrogen (TVB-N) values remained relatively constant (20–25 mg N/100 g) until day 11 of storage, but increased to 61.1, 37.6 and 39.4 mg N/100 g flesh for the control and ozonated specimen for 60 and 90 min, respectively on day 15 of storage. Thiobarbituric acid (TBA) values remained relatively constant (1–3 mg MA/kg flesh) until day 12 of storage but increased to 8.4, 6.4 and 3.8 mg MA/kg flesh on day 15 of storage for the control and the ozonated trout for 60 and 90 min, respectively. Sensory evaluation (odor, taste and texture) of cooked rainbow trout showed a very good correlation with bacterial populations. On the basis of both sensory and microbiological data, a shelf life of 10 and 12 days was obtained for ozonated, vacuum-packaged and refrigerated rainbow trout at 60 and 90 min, respectively.