The effect of some agricultural by-product extract on the rheological and technological properties of gelatin produced from sea bream (sparus aurata) skin

Gelatins from aquaculture have a limited use in food products due to their low melting point and unpleasant flavor and odor. In this study, it was tried to improve the rheological properties of fish gelatine with grape pomace (GPE), pomegranate peel (PPE), and green tea (GTE) extracts, which are all valuable agricultural waste extracts that cause environmental pollution but are also usefull as food components. For this purpose, kgel, tmodel, gel strength, melting point and gelation temperature (oC) parameters were examined to determine the best agricultural waste extract or extracts combination model using mathematical modeling. As a result, the optimum sample (OG) that gave the best results for these five surface responses was the sample with 20% GPE. With the addition of GPE and PPE (pomagranate pomace extract), the gel, gel strength, and melting temperatures of the samples generally increased. The physicochemical and technical properties of OG were investigated in relation to SG (bovine gelatin) and ÇG (control fish gelatin). It was discovered that the foam formation and foam stability, oil binding and water holding capacity, bloom degree and textural properties, melting behavior, microstructures, and structural changes in functional groups of the OG sample, which were determined by FTIR analysis, developed according to the ÇG sample, and showed similar properties to the SG sample. The melting point of fish gelatin was increased by 2,5oC with the addition of 20% GPE. Also, the addition of GPE contributed to the formation of a more stable structure by 74% shortening the gelation time. pH, moisture, ash, protein, L*, and b* values of the OG sample decreased and turbidity values increased. To determined the usefulnessof OG in food, which gives positive results in terms of its technological properties, model foods as jelly, ice cream, and pudding with the addition of SG, ÇG, and OG were produced. Following that, the effect of different gelatin addition on the rheological, technological, physicochemical, and sensory properties of model foods was investigated. In jelly-type candies, GPE added fish gelatin increased the nʹ-nʺ and Kʹ-Kʺ values of the jellies by 45-35% and 25-11%, respectively, and showed similar results to the SG added jelly in terms of sensory. While the melting rate was found to be lower in OG added ice cream compared to other ice-cream, it was determined that the η50 value of OG increased by 28% compared to ÇG. With the addition of OG, the nʹ-nʺ and Kʹ-Kʺ values of the pudding samples showed an improvement, and in connection with these, it was observed that the syneresis is reduced by 72% compared to the ÇG added pudding. As a result; A functional and food industry usable fish gelatin enriched with GPE has been developed.