Acid-Induced Gelation of European Eel Protein Isolate Fortified with Fish Oil: Enhancement of Physicochemical, Microstructural and Thermal Properties

Wafa Taktak; Sawsan  Affes; Marwa Hamdi; Suming  Li; Moncef  Nasri; Rim Nasri; Maha  Karra Chaabouni

doi:10.51745/najfnr.9.SI.S40-S49

Acid-Induced Gelation of European Eel Protein Isolate Fortified with Fish Oil: Enhancement of Physicochemical, Microstructural and Thermal Properties

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Food Chemistry, Engineering, Processing and Packaging

DOI https://doi.org/10.51745/najfnr.9.SI.S40-S49

Issue Vol. 9 No. SI (2025): Special Issue - Potential of food by-products

Submitted 2025-12-02

Accepted 2026-01-16

Published 2026-01-17

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Aims: This study aimed to investigate the gelation capacity of European Eel Protein Isolate (EPI) through the development of novel emulsion protein isolate-based gels (EPIGs). Furthermore, the research evaluated the extent to which fortification with bioactive European eel oil (EO) modulates the structural and functional attributes of these acid-induced gel matrices.

Methods: EPIGs were synthesized via thermal treatment (90°C for 60 min) of EPI solubilized in 20% (v/v) acetic acid, followed by emulsification with EO at two distinct weight ratios: 1:2 and 1:4 (EO:EPI, w/w). The resulting gel structures were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), texture profile analysis (TPA), and scanning electron microscopy (SEM).

Results: A 4% (w/v) EPI solution in acetic acid achieved gelation at 54°C, demonstrating superior thermal stability and significant gelling potential. FTIR analysis confirmed the successful incorporation of EO into the gel matrix, while TGA results indicated a slight increase in thermal degradation onset temperatures associated with higher EO concentrations, increasing from 375°C (EPIG1:4) to 382°C (EPIG1:2). Texture analysis revealed that incorporation of EO modestly augmented gel elasticity (from 12.93 mm to 13.19 mm), a phenomenon attributed to the stabilizing interactions between the lipid droplets and the protein network. Microstructural appraisal via SEM indicated that a higher EO load (EPIG1:2) induced the formation of larger pores, whereas the EPIG1:4 formulation exhibited a more cohesive and compact architecture with reduced porosity.

Keywords

European Eel Emulsion Protein Isolate-based Gel FTIR Thermogravimetric SEM

Wafa Taktak

Laboratory of Enzyme Engineering and Microbiology University of Sfax, National Engineering School of Sfax, B.P. 1173-73038 Sfax
Sawsan Affes

Laboratory of Enzyme Engineering and Microbiology University of Sfax, National Engineering School of Sfax, B.P. 1173-73038 Sfax
Marwa Hamdi

Laboratory of Enzyme Engineering and Microbiology University of Sfax, National Engineering School of Sfax, B.P. 1173-73038 Sfax
Suming Li

Institut Européen des Membranes, IEM-UMR 5635, Université de Montpellier, ENSCM, CNRS, 34095 Montpellier
Moncef Nasri

Laboratory of Enzyme Engineering and Microbiology University of Sfax, National Engineering School of Sfax, B.P. 1173-73038 Sfax
Rim Nasri

Laboratory of Enzyme Engineering and Microbiology University of Sfax, National Engineering School of Sfax, B.P. 1173-73038 Sfax. Higher Institute of Biotechnology of Monastir, University of Monastir, Monastir
Maha Karra Chaabouni

Laboratory of Enzyme Engineering and Microbiology University of Sfax, National Engineering School of Sfax, B.P. 1173-73038 Sfax

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Taktak, W., Affes, S. ., Hamdi, M., Li, S. ., Nasri, M. ., Nasri, R., & Karra Chaabouni, M. . (2026). Acid-Induced Gelation of European Eel Protein Isolate Fortified with Fish Oil: Enhancement of Physicochemical, Microstructural and Thermal Properties. The North African Journal of Food and Nutrition Research, 9(SI), S40-S49. https://doi.org/10.51745/najfnr.9.SI.S40-S49

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