Effect of different molecular weight chitosan coating on preservation of fish fillets during refrigerated storage

In order to explore the differences in the effect of different molecular weight (Mw) chitosan coatings (50, 200 and 500 kD) on the quality of refrigerated grass carp (Ctenopharyngodon idella) fillets, we applied the biological, physical and chemical methods to detect the fresh-keeping quality of the fish fillets, and compared the changes in the sensory scores, microbial enumeration total viable count (TVC) and Pseudomonas count, and physicochemical indicators shear force, water loss rate, pH, total volatile base nitrogen (TVB-N), TCA-soluble peptides and biogenic amines during the storage of different coating samples. The results show that compared with the control group, the coating treatments with all the three Mw chitosan coatings could inhibit the deterioration of fillets quality effectively. Combining with the results of sensory evaluation, TVB-N and TVC, the shelf life of the control group was less than 6 d, while the coating treatment could extend the shelf life more than at least 2 d, and especially the sensory quality of fillets with 200 kD Mw chitosan coating remained the best and had the longest shelf life during the storage. By comparing the microbial and physicochemical indexes of the three coated groups, we found that the total viable count (TVC), Pseudomonas count, shear force, juice loss rate, TVB-N and putrescine content of 200 kD Mw chitosan coating on the 8^th day of storage were better than those of the other two groups. Thus, 200 kD Mw chitosan coating could be used as a preferred coating material for the preservation of fresh fish meat.