Evaluating the Effect of Chitosan, Water-Soluble Chitosan and Chitosan Application Techniques on the Quality of Refrigerated Catfish Fillets

Chitosan (CH) is a biopolymer synthetized by deacetylation of chitin, it is found in the exoskeleton of crustaceans, cell wall of fungi, and insects. CH’s water insolubility limited the used of this compound in some food systems. However, enzymatic hydrolysis of CH yields water-soluble chitosan (WSC). The aim of this study was to evaluate the effect of chitosan, water-soluble chitosan, and chitosan application techniques on the quality of refrigerated catfish fillets. This research was conducted in two separated studies. In the first study, three solution treatments were prepared: (1) a 1% acetic acid (AA) solution, (2) a 0.5% CH solution in the 1% AA solution, and (3) 0.5% WSC in distilled water (DW). DW was used as a control solution. Fresh Catfish fillets were separately tumbled with DW, AA, CH, and WSC solutions for 10 min in a vacuum tumbler and then the catfish fillets were stored in refrigerated conditions (4 °C) for 20 days. In the second study, chitosan solution was prepared using a medium molecular weight 0.5% chitosan in 1% AA. CH solution was applied to the fillets using three techniques: (1) spraying (15% w/v), (2) dipping for 10 min in a ratio 1:1 w/v (g/ml), and (3) vacuum tumbling for 10 min in a ratio 1:1 w/v (g/ml). Catfish untreated was used as a control. After application of chitosan, the fresh catfish fillets were kept under refrigerated storage (4 °C) for 16 days. In both studies, the catfish fillets were evaluated for selected quality parameters during refrigerated storage. Triplicate experiments were conducted and the data was statistically analyzed (α=0.05). Catfish fillets treated with WSC had the lowest lipid oxidation. CH had higher inhibition in aerobic plate counts (APC) and yeast and mold counts than the other treatments during the 20 days in storage. An eight-day microbiological shelf life increase was observed for vacuum tumbled fillets and four day increases were obtained for some fillets which were sprayed or dipped compared to untreated fillets. This study demonstrated that CH with vacuum tumbling is effective in reducing microbial loads and lipid oxidation, respectively, in catfish fillets during refrigerated storage