Modification of Chemical and Functional Properties of Commercial Cold-Water Fish Gelatin by Oak Acorn (Quercus. Castaneifolia) Phenolic Extract

Research Aim: Gelatin, a protein-based hydrocolloid widely used in food and drug industries, faces limitations when derived from cold-water fish species due to low gel strength and functional properties. In this regard, this study explores the potential of oak (Q.castaneifolia) phenolic extract as a natural modifier of commercial cold-water fish gelatin (CW-FG). The use of natural crosslinking additives especially oxidized forms of phenolic extract may be suggested as the modification strategy of gelatin hydrogel. Therefore, the objective of this study was to evaluate the potential of oak (Q.castaneifolia) extract as chemical and rheological modifier of commercial cold-water fish gelatin.Materials and methods: The scope of the current work was to investigate the effects of concentration of oxidized/unoxidized oak phenolic extract, reaction pH values (۷ and ۹), and different concentrations ranged from ۰.۱ to ۰.۹ (mg/g protein) on gel strength, crosslinking degree, color parameters and swelling ratio of commercial cold-water fish gelatin. Further characterisation of the properties of different gelatin hydogels was also conducted by their conformational changes using fourier transform infrared (FTIR) analyses and scanning electron microscopy (SEM). Findings: The modified CW-FGs demonstrated higher gel strength, reduced swelling ratio and free amino group, and a more compact structure compared to uncross-linked samples and those containing unoxidized oak phenolic extract at neutral pH. The addition of both types of oak acorn extracts at increasing pH levels led to a decrease in L*-value and an increase in a* and b*-values. FTIR analysis revealed hydrogen bond formation as the primary molecular interaction, particularly in CW-FGs modified with oxidized oak extract at pH ۹. Additionally, free amino group could be controlled by adjusting the concentration of oak extracts. SEM analysis revealed that CW-FG gel containing Ox-OPP exhibited a non-uniform surface with varying pore sizes, exhibiting morphological differences from CW-FG gel containing OPP, particularly characterized by the creation of large empty spaces and fine filaments. These findings collectively demonstrate the potential for improving CW-FG gel properties through the judicious use of oak acorn phenolic extracts at specific concentrations and pH levels, with Ox-OPP showing promising effects on the gel's chemical and functional characteristics. Conclusion: Both oxidized and unoxidized oak phenolic extract showed high potential for modification of physico-chemical and functional properties of gelatin hydrogel. Also, crosslinking degree was controlled by concentration changes. Formation of higher molecular weight structures and hydrogen bonds between gelatin and phenolic compounds were determined as important factors for the observed results. These improved physicochemical properties of gelatin could lead to the development of products in the food industry that meet consumer demands.

کلیدواژه ها:

Cold-water fish gelatin (CW-FG) ، Oak (Quercus castaneifolia) phenolic extract ، Crosslinking ، FTIR ، SEM