Evaluation of the effect of nanoemulsion coating enriched with herbal additives on quality criteria of frozen rainbow trout(Oncorhynchus mykiss) fillets

In this study, nanoemulsions were prepared from different formulations of aloe vera gel (AVG) and hemp seed oil (HSO). For nanoemulsion characterization, pH, droplet size, polydispersity index, zeta potential, viscosity, turbidity, conductivity, color, transmission electron microscopy and Fourier transform-infrared spectroscopy analyzes were performed. Rainbow trout fillets were coated by dipping method with HA8 (5% HSO and 3% AVG) nanoemulsion, which was found to be the most suitable as a coating material with its low polydispersity index (0.17±0.01) and homogeneous morphological appearance. The nanoemulsion-coated fillets were then subjected to slow (-20°C) and quick freezing (-40°C) temperatures and the study groups were formed as follows: 20C (fillets coated with pure water frozen at -20°C), 20N (fillets coated with nanoemulsion frozen at -20°C), 40C (fillets coated with pure water frozen at -40°C), and 40N (fillets coated with nanoemulsion frozen at -40°C). Biochemical (moisture, crude protein, crude fat, and ash) and physicochemical (pH, sulfhydryl groups (-SH), disulfide bonds (S-S), carbonyl levels, myofibrillar fracture index, water holding capacity, water activity, drip loss, texture, color, TVB-N, and TBA) analyses were carried out monthly for 6 months on the frozen trout fillets. The results of this study indicated that none of the study groups exceeded limit values for pH, TVB-N, and TBA. The yellowness value of the nanoemulsion-coated fillets was observed to be high, which was attributed to the hemp seed oil. It was also determined that the nanoemulsion coating positively affected the firmness, drip loss, and water holding capacity of the products. Particularly, the fillets subjected to rapid freezing with nanoemulsion coating (40N) showed delayed protein oxidation, as evidenced by the sulfhydryl group, disulfide bond, carbonyl level, and myofibrillar fracture index data. Additionally, these fillets maintained acceptable quality parameters such as TVB-N, TBA, and pH. In conclusion, nanoemulsions containing AVG and HSO were found to enhance the quality of fish products, keeping them fresh for a longer period.