Combined Effect of Chitosan and Oregano Essential Oil Dip on the Microbiological, Chemical, and Sensory Attributes of Red Porgy (Pagrus pagrus) Stored in Ice

The combined effect of chitosan and oregano essential oil dip on shelf life of whole red porgy (Pagrus pagrus) stored in ice under refrigeration was investigated for a period up to 20 days. Quality attributes monitored during storage included microbiological (total viable counts, Pseudomonas spp., H2S-producing bacteria including Shewanella putrefaciens, Enterobacteriaceae, and lactic acid bacteria), physicochemical (pH, thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), trimethylamine (TMA), and color), and sensory (odor and taste) parameters. Untreated red porgy was used as the control sample. Regarding the chemical indicators of spoilage, TBARS values for all treatments were equal to or less than 0.4 mg MDA kg(-1) throughout the 20-day storage period. pH values varied between 6.6 (day 0) and 6.9 (day 14) for the various treatments. TVB-N values increased gradually during storage reaching the proposed acceptability limit (30 mg N 100 g(-1)) on day 13 for control samples, days 15-16 for samples treated with oregano essential oil, day 20 for samples treated with chitosan, and > 20 days for samples treated with chitosan plus oregano essential oil. Likewise, TMA values reached the proposed limit (5-6 mg N 100 g(-1)) for red porgy on days 11-12, 14-15, 19-20, and > 20, respectively. Finally, sensory evaluation data were in general agreement with microbiological data indicating a product shelf life of ca. 11 days for control samples, 16 days for samples treated with oregano essential oil, 18 days for samples treated with chitosan, and 19-20 days for samples treated with chitosan plus oregano essential oil.