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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Anvari, M., & Joyner (Melito), H. S. (2017). Anvari, M., & Joyner (Melito), H. S. (2017). Effect of formulation on structure-function relationships of concentrated emulsions: Rheological, tribological, and microstructural characterization. Food Hydrocolloids, 72, 11–26. https://doi.org/10.1016/j.foodhyd.2017.04.034 DOI: https://doi.org/10.1016/j.foodhyd.2017.04.034

Chaijan, M., Panpipat, W., & Benjakul, S. (2010). Physicochemical and gelling properties of short-bodied mackerel (Rastrelliger brachysoma) protein isolate prepared using alkaline-aided process. Food and Bioproducts Processing, 88(2–3), 174–180. https://doi.org/10.1016/j.fbp.2009.11.003 DOI: https://doi.org/10.1016/j.fbp.2009.11.003

Chen, L., Remondetto, G. E., & Subirade, M. (2006). Food protein-based materials as nutraceutical delivery systems. Trends in Food Science & Technology, 17(5), 272–283. https://doi.org/10.1016/j.tifs.2005.12.011 DOI: https://doi.org/10.1016/j.tifs.2005.12.011

Cho, D., Lee, S., & Frey, M. W. (2012). Characterizing zeta potential of functional nanofibers in a microfluidic device. Journal of Colloid and Interface Science, 372(1), 252–260. https://doi.org/10.1016/j.jcis.2012.01.007 DOI: https://doi.org/10.1016/j.jcis.2012.01.007

Datta, L. P., Manchineella, S., & Govindaraju, T. (2020). Biomolecules-derived biomaterials. Biomaterials, 230(119633), 119633. https://doi.org/10.1016/j.biomaterials.2019.119633 DOI: https://doi.org/10.1016/j.biomaterials.2019.119633

Dickinson E. (2015). Colloids in food: ingredients, structure, and stability. Annual Review of Food Science and Technology, 6, 211–233 https://doi.org/10.1146/annurev-food-022814-015651 DOI: https://doi.org/10.1146/annurev-food-022814-015651

Farjami, T., & Madadlou, A. (2019). An overview on preparation of emulsion-filled gels and emulsion particulate gels. Trends in Food Science & Technology, 86, 85–94. https://doi.org/10.1016/j.tifs.2019.02.043 DOI: https://doi.org/10.1016/j.tifs.2019.02.043

Folch, J., Lees, M., & Stanley, G. H. (1957). A simple method for the isolation and purification of total lipids from animal tissues. Journal of Biological Chemistry, 226(1), 497–509. DOI: https://doi.org/10.1016/S0021-9258(18)64849-5

García-Moreno, P. J., Özdemir, N., Stephansen, K., Mateiu, R. V., Echegoyen, Y., Lagaron, J. M., Chronakis, I. S., & Jacobsen, C. (2017). Development of carbohydrate-based nano-microstructures loaded with fish oil by using electrohydrodynamic processing. Food Hydrocolloids, 69, 273–285. https://doi.org/10.1016/j.foodhyd.2017.02.013 DOI: https://doi.org/10.1016/j.foodhyd.2017.02.013

Geremias-Andrade, I. M., Souki, N. P. B. G., Moraes, I. C. F., & Pinho, S. C. (2017). Rheological and mechanical characterization of curcumin-loaded emulsion-filled gels produced with whey protein isolate and xanthan gum. *LWT - Food Science and Technology. 86, 166–173. https://doi.org/10.1016/j.lwt.2017.07.063 DOI: https://doi.org/10.1016/j.lwt.2017.07.063

Harsch, M., Herzog, F., & Karger-Kocsis, J. (2008). Cure-induced normal force development in unfilled and filled epoxy resins. Journal of Composite Materials, 42(21), 2299–2309. https://doi.org/10.1177/0021998308094969 DOI: https://doi.org/10.1177/0021998308094969

Hattrem, M. N., Molnes, S., Haug, I. J., & Draget, K. I. (2015). Interfacial and rheological properties of gelatin based solid emulsions prepared with acid or alkali pretreated gelatins. Food Hydrocolloids, 43, 700–707. https://doi.org/10.1016/j.foodhyd.2014.07.026 DOI: https://doi.org/10.1016/j.foodhyd.2014.07.026

Jamshidi, A., Cao, H., Xiao, J., & Simal-Gandara, J. (2020). Advantages of techniques to fortify food products with the benefits of fish oil. Food Research International (Ottawa, Ont.), 137(109353), 109353. https://doi.org/10.1016/j.foodres.2020.109353 DOI: https://doi.org/10.1016/j.foodres.2020.109353

Kharlamova, A., Chassenieux, C., & Nicolai, T. (2018). Acid-induced gelation of whey protein aggregates: Kinetics, gel structure and rheological properties. Food Hydrocolloids, 81, 263–272. https://doi.org/10.1016/j.foodhyd.2018.02.043 Google Scholar DOI: https://doi.org/10.1016/j.foodhyd.2018.02.043

Li, X., Wang, X., Xu, D., Cao, Y., Wang, S., Wang, B., Sun, B., Yuan, F., & Gao, Y. (2018). Enhancing physicochemical properties of emulsions by heteroaggregation of oppositely charged lactoferrin coated lutein droplets and whey protein isolate coated DHA droplets. Food Chemistry, 239, 75–85. https://doi.org/10.1016/j.foodchem.2017.06.078 DOI: https://doi.org/10.1016/j.foodchem.2017.06.078

Li, S., Li, L., Zhu, X., Ning, C., Cai, K., & Zhou, C. (2019). Conformational and charge changes induced by l-Arginine and l-lysine increase the solubility of chicken myosin. Food Hydrocolloids, 89, 330–336. https://doi.org/10.1016/j.foodhyd.2018.10.059 DOI: https://doi.org/10.1016/j.foodhyd.2018.10.059

Li, R., Wu, N., Xue, H., Gao, B., Liu, H., Han, T., Hu, X., Tu, Y., & Zhao, Y. (2023). Influence and effect mechanism of disulfide bonds linkages between protein-coated lipid droplets and the protein matrix on the physicochemical properties, microstructure, and protein structure of ovalbumin emulsion gels. Colloids and Surfaces. B, Biointerfaces, 223(113182), 113182. https://doi.org/10.1016/j.colsurfb.2023.113182 DOI: https://doi.org/10.1016/j.colsurfb.2023.113182

Line, V. L. S., Remondetto, G. E., & Subirade, M. (2005). Cold gelation of β-lactoglobulin oil-in-water emulsions. Food Hydrocolloids, 19(2), 269–278. https://doi.org/10.1016/j.foodhyd.2004.06.004 DOI: https://doi.org/10.1016/j.foodhyd.2004.06.004

Lu, Y., Mao, L., Zheng, H., Chen, H., & Gao, Y. (2020). Characterization of β-carotene loaded emulsion gels containing denatured and native whey protein. Food Hydrocolloids, 102(105600), 105600. https://doi.org/10.1016/j.foodhyd.2019.105600 DOI: https://doi.org/10.1016/j.foodhyd.2019.105600

Moomand, K., & Lim, L.-T. (2014). Oxidative stability of encapsulated fish oil in electrospun zein fibres. Food Research International (Ottawa, Ont.), 62, 523–532. https://doi.org/10.1016/j.foodres.2014.03.054 DOI: https://doi.org/10.1016/j.foodres.2014.03.054

Taylor, M. J., Tomlins, P., & Sahota, T. S. (2017). Thermoresponsive Gels. Gels, 3(1), 4. https://doi.org/10.3390/gels3010004 DOI: https://doi.org/10.3390/gels3010004

McClements, D. J. (2015). Food emulsions: Principles, Practices, and Techniques (3rd ed.). CRC Press. DOI: https://doi.org/10.1201/b18868

Nasri, R., Taktak, W., Hamdi, M., Ben Amor, N., Kabadou, A., Li, S., & Nasri, M. (2020). Sardinelle protein isolate as a novel material for oil microencapsulation: Novel alternative for fish by-products valorisation. Materials Science & Engineering. C, Materials for Biological Applications, 116(111164), 111164. https://doi.org/10.1016/j.msec.2020.111164 DOI: https://doi.org/10.1016/j.msec.2020.111164

O’Sullivan, J., Murray, B., Flynn, C., & Norton, I. (2016). The effect of ultrasound treatment on the structural, physical and emulsifying properties of animal and vegetable proteins. Food Hydrocolloids, 53, 141–154. https://doi.org/10.1016/j.foodhyd.2015.02.009 DOI: https://doi.org/10.1016/j.foodhyd.2015.02.009

Saha, D., & Bhattacharya, S. (2010). Hydrocolloids as thickening and gelling agents in food: a critical review. Journal of Food Science and Technology, 47(6), 587–597. https://doi.org/10.1007/s13197-010-0162-6 DOI: https://doi.org/10.1007/s13197-010-0162-6

Souissi, N., Abdelhedi, O., Mbarek, A., Kammoun, W., Kechaou, H., & Nasri, M. (2017). Gelatin based bio-films prepared from grey triggerfish’ skin influenced by enzymatic pretreatment. International Journal of Biological Macromolecules, 105(Pt 2), 1384–1390. https://doi.org/10.1016/j.ijbiomac.2017.08.181 DOI: https://doi.org/10.1016/j.ijbiomac.2017.08.181

Surh, J., Decker, E., & McClements, D. (2006). Influence of pH and pectin type on properties and stability of sodium-caseinate stabilized oil-in-water emulsions. Food Hydrocolloids, 20(5), 607–618. https://doi.org/10.1016/j.foodhyd.2005.07.004 DOI: https://doi.org/10.1016/j.foodhyd.2005.07.004

Tabarestani, H. S., Maghsoudlou, Y., Motamedzadegan, A., & Mahoonak, A. S. (2010). Optimization of physico-chemical properties of gelatin extracted from fish skin of rainbow trout (Oncorhynchus mykiss). Bioresource Technology, 101(15), 6207–6214. https://doi.org/10.1016/j.biortech.2010.02.071 DOI: https://doi.org/10.1016/j.biortech.2010.02.071

Taktak, W., Nasri, R., Hamdi, M., Gomez-Mascaraque, L. G., Lopez-Rubio, A., Li, S., Nasri, M., & Karra-Chaâbouni, M. (2018). Physicochemical, textural, rheological and microstructural properties of protein isolate gels produced from European eel (Anguilla anguilla) by heat-induced gelation process. Food Hydrocolloids, 82, 278–287. https://doi.org/10.1016/j.foodhyd.2018.04.008 DOI: https://doi.org/10.1016/j.foodhyd.2018.04.008

Taktak, W., Nasri, R., Lopez-Rubio, A., Hamdi, M., Gomez-Mascaraque, L. G., Ben Amor, N., Kabadou, A., Li, S., Nasri, M., & Karra-Chaâbouni, M. (2019). Improved antioxidant activity and oxidative stability of spray dried European eel (Anguilla anguilla) oil microcapsules: Effect of emulsification process and eel protein isolate concentration. Materials Science & Engineering. C, Materials for Biological Applications, 104(109867), 109867. https://doi.org/10.1016/j.msec.2019.109867 DOI: https://doi.org/10.1016/j.msec.2019.109867

Yang, C., Wang, Y., Vasanthan, T., & Chen, L. (2014). Impacts of pH and heating temperature on formation mechanisms and properties of thermally induced canola protein gels. Food Hydrocolloids, 40, 225–236. https://doi.org/10.1016/j.foodhyd.2014.03.011 DOI: https://doi.org/10.1016/j.foodhyd.2014.03.011

Yan, B., Jiao, X., Zhu, H., Wang, Q., Huang, J., Zhao, J., Cao, H., Zhou, W., Zhang, W., Ye, W., Zhang, H., & Fan, D. (2020). Chemical interactions involved in microwave heat-induced surimi gel fortified with fish oil and its formation mechanism. Food Hydrocolloids, 105(105779), 105779. https://doi.org/10.1016/j.foodhyd.2020.105779 DOI: https://doi.org/10.1016/j.foodhyd.2020.105779

Ye, A., & Taylor, S. (2009). Characterization of cold-set gels produced from heated emulsions stabilized by whey protein. International Dairy Journal, 19(12), 721–727. https://doi.org/10.1016/j.idairyj.2009.06.003 DOI: https://doi.org/10.1016/j.idairyj.2009.06.003

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