Effect of Phloretin on microbial control and maintain the quality of rainbow trout (Oncorhynchus mykiss)

Phloretin is a natural flavonoid that has antimicrobial and antioxidant activities. Gallic acid is another combination of flavonoids group. The object of this study was to evaluate the function of phloretin as a preservative factor for rainbow trout fillets during storage temperature in the refrigator. This performance has been investigated by examining microbial, chemical and physiochemical indices in four sampling times on days 0, 7, 14 and 21. Trout samples were dipped in phloretin solution (150 mg/ml and 250 mg/ml) and gallic acid solution (250 mg/ml), stored at 4°C for 21 days. Microbial tests showed that microbial load of trout fillet treated by phloretin 250 mg/ml lowered significantly (P<0.05) compared to the control samples in 0, 7 and 14 days. In addition to, phloretin significantly (P<0.05) reduces oxidation, total volatile basic nitrogen (TVB-N), hydrolysis of free fatty acids and the range of pH changes, which are chemical indicators of trout fillet spoilage in 0, 7 and 14 in comparison with control treatment and  also the analysis of the color indicators performed on the treated fillets, showed that phloretin 250 mg/ml was able to maintain color indexes compared to control samples at a significant level of 0.05 in 0, 7 and 14 days. All rainbow trout fillets were treated from day 14 had symptoms of spoilage. The results of this experiment proved the effectiveness of phloretin 250 mg/ml on antimicrobial mechanisms, and inhibition of spoilage.