Determination of some quality changes during cold storage of rainbow fi̇llets coated with powder protein hydrolyzate obtained by-products of rainbow trout

In the present study, it was aimed to produce powder protein hydrolyzate from the by products (head, spine, fins and skin) from the rainbow trout fillet processing and the effect of it on shelf life during cold storage (4±1°C) of the rainbow trout fillet coated with this hydrolyzate. The resultant powder protein obtained with alcalase hydrolyzate was mixed with distilled water and glycerol at certain ratios and the trout fillets were coated with this mix by dipping method. Control group was set in the same application, yet the fillets of this group was subjected to distilled water. The control and coated group of fillets were packaged and storage at the refrigerator conditions. Thereafter fillets were subjected to the physical (water activity (aw), pH and color analysis), chemical (TVB-N and TBA), sensorial (appearance, odor and texture) and microbiological analyses besides crude protein, dry matter, crude oil and crude ash tests. The yield of the protein hydrolyzate obtained from the trout by products was found to be 9.05%, as biochemical content was 94.75% dry matter, 86.40% crude protein, 0.37% crude oil and 6.34% crude ash in the presented study. The limit values of the chemical and microbiological analyzes were not exceeded while the spoilage occurred below the limit value of 4 points in the sensorial control and in the coated group on the day 5 and day 9, respectively. The shelf life of the control group was determined as 3 days and the coating group was 7 days based on these results. According to the results of the study, it was determined that the edible coating made by protein hydrolyzate obtained from the by-products of the rainbow trout increased the shelf life of the trout fillets by about 2 times.