Protective Role of Bio-Based Coating of Ultrasound-Improved Trout (Oncorhynchus mykiss Walbaum, 1792) Waste Protein Hydrolysate for Bonito (Sarda sarda Bloch, 1793) Fillets at Storage at -18±1°C

Abstract

A novel and rich protein source was utilized in bonito fillets to prevent/ delay deterioration during frozen storage at -18±1°C. Accordingly, trout wastes protein hydrolysates (PH); produced enzymatically traditional protein hydrolysate (TPH) and ultrasound–treated protein hydrolysate (UPH) containing 86.40 g/100 g and 86.75 g/100 g protein respectively used as a coating. Hydrolysates were mixed with glycerol (2:1) to form coating materials. Three groups of fillets were prepared as control fillets (C) without coating, TPH coated fillets (TPHCF), and UPH coated fillets (UPHCF). pH, color, TVB-N, TBA, and TMA, and sensory analyzes were performed in all groups. The L* value of all groups reached a maximum the highest value at 6 months and was 54.56±0.27, 53.74±0.23, and 54.83±1.26 for C, TPHCF, and UPHCF, respectively. TVB-N was 18.08±0.10, 17.71±0.09, and 17.36±0.12, for C, TPHCF, and UPHCF, respectively, in the first month of storage. The values reached 32.18±0.29, 26.61±0.12, and 25.72±0.08 at 7th month for C, TPHCF, and UPHCF, respectively. TBA value of the C group samples of the frozen bonito fillets reached 7.53 in the 7th month, it remained within the consumable limits, and it remained within the consumable limits in the coated groups. Significant increases occurred in TMA values of all groups between months during the seven-month storage period. Accordingly, the TMA values for C, TPHCF, and UPHCF were 2.56±0.04 mg/100 g, 2.12±0.04mg/100 g and 2.16±0.06mg/100 g, respectively, at the 7th month. The mean values of sensory parameters were 9.15±0.08; 9.51±0.12 and 9.46±0.13 for C, TPHCF, and UPHCF, respectively, at the 1st month of storage. While they were 5.29±0.09, 6.23±0.06 and 6.24±0.09, in THE same order, respectively. Results showed that TPHCF and UPHCF have a potential as a coating for bonito fillets at frozen conditions, prolonging the shelf life.