Microbiological and physicochemical quality of tilapia fillets treated with ozone and chlorine solution and stored under refrigeration

Fish are foods of high nutritional value for the human diet. However, they deteriorate easily due to microbial activity. The combined action of sanitizing solutions on fillets, the antimicrobial and physicochemical effects of aqueous ozone and chlorine used to wash fillets were investigated immediately after application and during storage. The fillets were treated with demineralized water (control), 5 ppm chlorine solution (Cl), 5 ppm ozone solution (Oz) or 5 ppm chlorine solution with 5 ppm ozone (Cl+Oz). The proximate composition and pH of the fillets were not altered immediately after treatment. The mesophilic count decreased by 0.49 log CFU/g at Cl and 0.56 log CFU/g at Cl+Oz. The Cl treatment showed lower values of lipid oxidation, and the control and Cl treatments showed lower values for total volatile base nitrogen (TVB-N). The treatments did not differ from each other during storage; increases in lipids, TVB-N, lipid oxidation and mesophilic and psychrotrophic counts, as well as a reduction in proteins, were observed. These results were expected due to microbial degradation during storage. The results indicated that the combined action of the sanitizers regulated microbial activity better than the control but was not able to promote the shelf life of the product