Physicochemical and Functional Comparison of Gelatin Extracted from Rainbow Trout (Oncorhynchus mykiss) and Silver Carp (Hypophthalmichthys molitrix) Byproducts

Document Type : Research Article-en

Authors

Alireza Amirafzali

Masoud Rezaei

Shahab Naghdi

Seafood Processing Department, Marine Sciences Faculty, Tarbiat Modares University, Noor, Iran

https://doi.org/10.22067/ifstrj.2026.96879.1528

Abstract

In this research, gelatin was extracted from various by-products of silver carp (Hypophthalmichthys molitrix) (SC) and rainbow trout (Oncorhynchus mykiss) (RT), including skin, soft tissue, head, and vertebrae. The extracted gelatins were evaluated for proximate composition, molecular weight, functional properties, and structural characteristics. The findings revealed that the protein content of the gelatin samples ranged from 69.25% to 85.75%, with fat levels below 1.5%. The highest moisture content was observed in RT-skin gelatin (16.8%), while the lowest was found in RT-vertebral bone gelatin (2.97%). SDS-PAGE analysis showed clear 1α (~114–121 kDa) and 2α (~100–112 kDa) chains in skin and cranial soft tissue gelatins, whereas bone-derived samples lacked distinct bands, indicating extensive collagen degradation due to harsh acid treatment. In terms of viscosity, the highest value (11 cP) was recorded for SC-cranial soft tissue gelatin, and the lowest (2.6 cP) for RT-head gelatin. Gel strength ranged from 573.5 g (SC-skin) to 19.6 g (RT-head). The melting point of SC-gelatins was significantly higher than that of RT, with some samples approaching values similar to bovine skin gelatin. SC-vertebral bone gelatin exhibited the greatest foaming capacity (120 ± 2%), while SC-head gelatin demonstrated the highest foam stability (48.03 ± 2.12%). These results suggest that non-commercial by-products from these two fish species, especially SC-skin and cranial soft tissue, represent valuable potential sources for producing high-quality gelatin for food applications.

Keywords

Fish gelatin

Functional properties

Hypophthalmichthys molitrix

Oncorhynchus mykiss

SDS-PAGE analysis

Subjects

• Food Biotechnology

---

Authors retain the copyright. This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0)

References

1. Abdollahi, M., Rezaei, M., & Jafari, E. (2014). Evaluation of production efficiency, by-products, and their nutritional value during the processing of rainbow trout. JFST, 2(4), 23–34.
2. Adnan, S., Kresnowati, M.T.A.P., Marlina, & Bindar, Y. (2024). Sustainable valorisation of freshwater fish by-products to gelatin and fish oil by hydrothermal extraction. International Journal of Food Science and Technology, 8224–8235. https://doi.org/10.1111/ijfs.17512
3. Adnan, S., Kresnowati, M.T.A.P., Marlina, & Bindar, Y. (2025). Effect of operational variables on gel strength of fish gelatin striped catfish (Pangasianodon hypophthalmus). AIP Conference Proceedings, 3295(1), 70007. https://doi.org/10.1063/5.0269817
4. Alves, A.L., Fraguas, F.J., Carvalho, A.C., Valcárcel, J., Pérez-Martín, R.I., Reis, R.L., Vázquez, J.A., & Silva, T.H. (2022). Characterization of codfish gelatin: A comparative study of fresh and salted skins and different extraction methods. Food Hydrocolloids, 124(December 2020). https://doi.org/10.1016/j.foodhyd.2021.107238
5. Anandito, R.B.K., Purwanto, E., Praseptiangga, D., & Zaman, M.Z. (2024). Optimization of cobia fish (Rachycentron canadum) gelatin extraction with response surface methodology. Food Research, 8, 139–147. https://doi.org/10.26656/fr.2017.8(S2).98
6. Arnesen, J.A., & Gildberg, A. (2006). Extraction of muscle proteins and gelatine from cod head. Process Biochemistry, 41(3), 697–700. https://doi.org/10.1016/j.procbio.2005.09.001
7. Association of Official Analytical Chemists. Official Methods of Analysis of AOAC International; AOAC International: Gaithersburg, MD, USA, 2000. https://doi.org/10.1093/9780197610145.003.1380
8. Barman, L.C., Sikder, M.B.H., Ahmad, I., Shourove, J.H., Rashid, S.S., & Ramli, A.N.M. (2020). Gelatin extraction from the Bangladeshi Pangas catfish (Pangasius pangasius) waste and comparative study of their physicochemical properties with a commercial gelatin. International Journal of Engineering Technology and Sciences, 7(2), 13–23. https://doi.org/10.15282/10.15282/ijets.7.2.2020.1002
9. Barman, L.C., Sikder, M.B.H., Ahmad, I., Shourove, J.H., Samiur Rashid, S., & Ramli, A.N.M. (2021). Gelatin extraction from the Bangladeshi Pangas Catfish (Pangasius pangasius) waste and comparative study of their physicochemical properties with a commercial gelatin. International Journal of Engineering Technology and Sciences, 7(2), 13–23. https://doi.org/10.15282/10.15282/ijets.7.2.2020.1002
10. Bekesheva, A.A., & Yakubova, O.S. (2018). Scientific substantiation of physical properties of fish gelatin. Vestnik of Astrakhan State Technical University. Series: Fishing Industry, 132–140. https://doi.org/10.24143/2073-5529-2017-3-132-140
11. Boran, G., & Regenstein, J.M. (2009). Optimization of gelatin extraction from silver carp skin. Journal of Food Science, 74(8), E432–E441. https://doi.org/10.1111/j.1750-3841.2009.01328.x
12. British Standards Institution – BSI. (1975). Methods for sampling and testing gelatin (Physical and Chemical Methods). London: BSI.
13. Choi, S.S., & Regenstein, J.M. (2000). Physicochemical and sensory characteristics of fish gelatin. Journal of Food Science, 65(2), 194–199. https://doi.org/10.1111/j.1365-2621.2000.tb15978.x
14. Derkach, S.R., Voron’ko, N.G., Kuchina, Y.A., & Kolotova, D.S. (2020). Modified fish gelatin as an alternative to mammalian gelatin in modern food technologies. Polymers, 12(12), 1–10. https://doi.org/10.3390/polym12123051
15. Du, L., Khiari, Z., Pietrasik, Z., & Betti, M. (2013). Physicochemical and functional properties of gelatins extracted from turkey and chicken heads. Poultry Science, 92(9), 2463–2474. https://doi.org/10.3382/ps.2013-03161
16. Duasa, J., Husin, A.M., Asmy Mohd Thas Thaker, M., & Rahman, M.P. (2022). An alternative source of collagen for Muslim consumers: halal and environmental concerns. Journal of Islamic Marketing, 13(11), 2232–2253. https://doi.org/10.1108/jima-09-2020-0268
17. Duman, M. (2025). Collagen extraction from rainbow (Oncorhynchus mykiss) trout heads and skins. Revista Cientifica de La Facultad de Veterinaria, 35(2), 1–7. https://doi.org/10.52973/rcfcv-e35646
18. Elavarasan, K., Kumar, A., Uchoi, D., Tejpal, C.S., Ninan, G., & Zynudheen, A.A. (2017). Extraction and characterization of gelatin from the head waste of tiger tooth croaker (Otolithes ruber). Waste and Biomass Valorization, 8(3), 851–858. https://doi.org/10.1007/s12649-016-9639-5
19. FAO. (2024). World Fisheries and Aquaculture, FAO:Rome,2022 (pp. 1–11).
20. Feng, Y., Shi, Q., Xie, H., Ouyang, K., Xiong, H., & Zhao, Q. (2024). Combined effects of gelatin extraction methods and hydrolysis protease types on the functional properties of tilapia scale gelatin hydrolysates. International Journal of Food Science and Technology, 59(9), 6194–6206. https://doi.org/10.1111/ijfs.17354
21. Göçer, M. (2022). Extraction and characterization of collagen from the skin and bone of shabout (Arabibarbus grypus Heckel, 1843). Iranian Journal of Fisheries Sciences, 21(3), 671–687. https://doi.org/10.22092/ijfs.2022.126898
22. Gomez-Guillen, M.C., Gimenez, B., Lopez-Caballero, M.E., & Montero, M.P. (2011). Functional and bioactive properties of collagen and gelatin from alternative sources: A review. In Food Hydrocolloids, 25(8), 1813–1827. Elsevier. https://doi.org/10.1016/j.foodhyd.2011.02.007
23. Goudie, K.J., McCreath, S.J., Parkinson, J.A., Davidson, C.M., & Liggat, J.J. (2023). Investigation of the influence of pH on the properties and morphology of gelatin hydrogels. Journal of Polymer Science, 61(19), 2316–2332. https://doi.org/10.1002/pol.20230141
24. GME. (2011). Gelatin Manufacturers of Europe: Raw materials. Retrieved from http://www.gelatine.org/en/about-gelatine/ manufacturing/raw-materials.html
25. Guan, Y., He, J., Chen, J., Li, Y., Zhang, X., Zheng, Y., & Jia, L. (2022). Valorization of fish processing by-products: Microstructural, rheological, functional, and properties of silver carp skin type I collagen. Foods, 11(19). https://doi.org/10.3390/foods11192985
26. He, J., Zhang, J., Xu, Y., Ma, Y., & Guo, X. (2022). The structural and functional differences between three species of fish scale gelatin and pigskin gelatin. Foods, 11(24). https://doi.org/10.3390/foods11243960
27. Hu, B., Cen, S., Sun, W., Zhan, S., Jia, R., Ou, C., & Huang, T. (2024). Effects of different phosphorylation times and pH on fish gelatin: Functional properties, structural and mechanism analysis. Food Hydrocolloids, 152, 109876. https://doi.org/10.1016/j.foodhyd.2024.109876
28. Huang, T., Tu, Z., cai, Shangguan, X., Sha, X., Wang, H., Zhang, L., & Bansal, N. (2019). Fish gelatin modifications: A comprehensive review. Trends in Food Science and Technology, 86(August 2018), 260–269. https://doi.org/10.1016/j.tifs.2019.02.048
29. Iranian Fisheries Organization Statistical Yearbook. (2024). Iranian Fisheries Organization Statistical Yearbook, 1st ed.; Iranian Fisheries Organization: Tehran, Iran, 2024; p. 30. 1–30. https://doi.org/10.52547/injvr.1.1.1
30. Karim, A.A., & Bhat, R. (2009). Fish gelatin: properties, challenges, and prospects as an alternative to mammalian gelatins. Food Hydrocolloids, 23(3), 563–576. https://doi.org/10.1016/j.foodhyd.2008.07.002
31. Kittiphattanabawon, P., Benjakul, S., Visessanguan, W., & Shahidi, F. (2010). Comparative study on characteristics of gelatin from the skins of brownbanded bamboo shark and blacktip shark as affected by extraction conditions. Food Hydrocolloids, 24(2–3), 164–171. https://doi.org/10.1016/j.foodhyd.2009.09.001
32. Koli, J.M., Basu, S., Nayak, B.B., Patange, S.B., Pagarkar, A.U., & Gudipati, V. (2012). Functional characteristics of gelatin extracted from skin and bone of Tiger-toothed croaker (Otolithes ruber) and Pink perch (Nemipterus japonicus). Food and Bioproducts Processing, 90(3), 555–562. https://doi.org/10.1016/j.fbp.2011.08.001
33. Koli, J.M., Basu, S., Venkteshwarlu, G., Choukasy, M.K., & Nayak, B.B. (2013). Optimization of fish gelatin extraction from skins and bones: A comparative study. Ecology, Environment and Conservation, 19(1), 47–56.
34. Kwak, H.W., Shin, M., Lee, J.Y., Yun, H., Song, D.W., Yang, Y., Shin, B.S., Park, Y.H., & Lee, K.H. (2017). Fabrication of an ultrafine fish gelatin nanofibrous web from an aqueous solution by electrospinning. International Journal of Biological Macromolecules, 102, 1092–1103. https://doi.org/10.1016/j.ijbiomac.2017.04.087
35. Laemmli, U.K. (1970). Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature, 227, 680–685. https://doi.org/10.1038/227680a0
36. Liu, H.Y., Han, J., & Guo, S.D. (2009). Characteristics of the gelatin extracted from Channel Catfish (Ictalurus punctatus) head bones. LWT-Food Science and Technology, 42(2), 540–544. https://doi.org/10.1016/j.lwt.2008.07.013
37. Nagarajan, M., Benjakul, S., Prodpran, T., Songtipya, P., & Kishimura, H. (2012). Characteristics and functional properties of gelatin from splendid squid (Loligo formosana) skin as affected by extraction temperatures. Food Hydrocolloids, 29(2), 389–397. https://doi.org/10.1016/j.foodhyd.2012.04.001
38. Naghdi, S., Rezaei, M., Heidari, M.G., Tahergorabi, R., Lorenzo, J.M., & Mirzaei, F. (2024). Insights into fishery by-product application in aquatic feed and food: a review. In Aquaculture International (Issue 0123456789). Springer International Publishing. https://doi.org/10.1007/s10499-024-01447-x
39. Naghdi, S., Rezaei, M., Tabarsa, M., & Abdollahi, M. (2025). Structure , functionality and bioactivity of sulfated polysaccharide extracted from rainbow trout byproducts : pH-shift method vs enzymatic hydrolysis. Food Chemistry, 479(March), 143665. https://doi.org/10.1016/j.foodchem.2025.143665
40. Nikoo, M., Benjakul, S., Bashari, M., Alekhorshied, M., Cissouma, A.I., Yang, N., & Xu, X. (2014). Physicochemical properties of skin gelatin from farmed Amur sturgeon (Acipenser schrenckii) as influenced by acid pretreatment. Food Bioscience, 5, 19–26. https://doi.org/10.1016/j.fbio.2013.10.004
41. Nurilmala, M., Suryamarevita, H., Hizbullah, H.H., Jacoeb, A.M., & Ochiai, Y. (2022). Fish skin as a biomaterial for halal collagen and gelatin. Saudi Journal of Biological Sciences, 29(2), 1100–1110. https://doi.org/10.1016/j.sjbs.2021.09.056
42. Nurul, A.G., & Sarbon, N.M. (2015). Effects of pH on functional, rheological and structural properties of eel (Monopterus) skin gelatin compared to bovine gelatin. International Food Research Journal, 22(2).
43. Olaniran, A.F., Adeoye, O.E., Oyadeyi, O.M., Okonkwo, C.E., Erinle, O.C., Malomo, A.A., Iranloye, Y.M., Olaniran, O.D., & Faloye, O.R. (2024). Utilization and application of bioactive compounds generated from Fish waste and by product as Functional Food Ingredient: A review. IOP Conference Series: Earth and Environmental Science, 1342(1). https://doi.org/10.1088/1755-1315/1342/1/012014
44. Peng, J., Zi, Y., Xu, J., Zheng, Y., Huang, S., Hu, Y., & Liu, B. (2022). Effect of extraction methods on the properties of tilapia scale gelatins. International Journal of Biological Macromolecules, 221(July), 1150–1160. https://doi.org/10.1016/j.ijbiomac.2022.09.094
45. Ruan, Q., Chen, W., Lv, M., Zhang, R., Luo, X., Yu, E., Pan, C., & Ma, H. (2023). Influences of trypsin pretreatment on the structures, composition, andfunctional characteristics of skin gelatin of Tilapia, grass carp, and sea perch. Marine Drugs, 21(8). https://doi.org/10.3390/md21080423
46. Sha, X.M., Tu, Z.C., Wang, H., Shi, Y., Liu, G.X., Man, Z.Z., Huang, T., & Lan, Z. (2013). Preparation and properties on gelatin from fish scale. Advanced Materials Research, 647, 352–356. https://doi.org/10.4028/www.scientific.net/AMR.647.352
47. Shakila, R.J., Jeevithan, E., Varatharajakumar, A., Jeyasekaran, G., & Sukumar, D. (2012). Functional characterization of gelatin extracted from bones of red snapper and grouper in comparison with mammalian gelatin. LWT-Food Science and Technology, 48(1), 30–36. https://doi.org/10.1016/j.lwt.2012.03.007
48. Shyni, K., Hema, G.S., Ninan, G., Mathew, S., Joshy, C.G., & Lakshmanan, P.T. (2014). Isolation and characterization of gelatin from the skins of skipjack tuna (Katsuwonus pelamis), dog shark (Scoliodon sorrakowah), and rohu (Labeo rohita). Food Hydrocolloids, 39, 68–76. https://doi.org/10.1016/j.foodhyd.2013.12.008
49. Siburian, W.Z., Rochima, E., Andriani, Y., & Praseptiangga, D. (2020). Fish gelatin (definition, manufacture, analysis of quality characteristics, and application): A review. International Journal of Fisheries and Aquatic Studies, 8(4), 90–95.
50. Silviwanda, S., & Najib Tuisina, N. (2024). Physical characteristics of fishbone gelatin (gel strength, viscosity, and pH): Review. Journal of Tropical Food and Agroindustrial Technology, 5(01), 9–18. https://doi.org/10.21070/jtfat.v5i01.1619
51. Sinthusamran, S., Benjakul, S., & Kishimura, H. (2015). Molecular characteristics and properties of gelatin from skin of seabass with different sizes. International Journal of Biological Macromolecules, 73, 146–153. https://doi.org/10.1016/j.ijbiomac.2014.11.024
52. Tabarestani, H.S., Maghsoudlou, Y., Motamedzadegan, A., Sadeghi Mahoonak, A.R., & Mahoonak, A.R.S. (2010). Optimization of physico-chemical properties of gelatin extracted from fish skin of rainbow trout (Onchorhynchus mykiss). Bioresource Technology, 101(15), 6207–6214. https://doi.org/10.1016/j.biortech.2010.02.071
53. Tavakolipour, H. (2011). Extraction and evaluation of gelatin from silver carp waste. World Journal of Fish and Marine Sciences, 3(1), 10–15.
54. Uddin, S.M.K., Hossain, M.A.M., Sagadevan, S., Al Amin, M., & Johan, M.R. (2021). Halal and Kosher gelatin: Applications as well as detection approaches with challenges and prospects. Food Bioscience, 44(PA), 101422. https://doi.org/10.1016/j.fbio.2021.101422
55. Usman, M., Sahar, A., Inam-Ur-Raheem, M., Rahman, U., Sameen, A., & Aadil, R.M. (2022). Gelatin extraction from fish waste and potential applications in food sector. International Journal of Food Science and Technology, 57(1), 154–163. https://doi.org/10.1111/ijfs.15286
56. Valcarcel, J., Hermida-Merino, C., Piñeiro, M.M., Hermida-Merino, D., & Vázquez, J.A. (2021). Extraction and characterization of gelatin from skin by-products of seabream, seabass and rainbow trout reared in aquaculture. International Journal of Molecular Sciences, 22(22). https://doi.org/10.3390/ijms222212104
57. Wang, Y., Cui, Q., Wang, X., Wu, C., Xu, X., Dong, X., & Pan, J. (2024). The gelling properties of fish gelatin as improved by ultrasound-assisted phosphorylation. Food Chemistry, 449(December 2023), 139214. https://doi.org/10.1016/j.foodchem.2024.139214
58. Xie, D., Tang, Y., & Dong, G. (2024). Various factors affecting the gel properties of surimi: A review. Journal of Texture Studies, 55(3), e12847. https://doi.org/10.1111/jtxs.12847
59. Yazid, M., Hartina, U., Razali, M., Shaarani, S., Roslan, J., Amirah, R., Noor, M., & Qhairul, N. (2024). Physicochemical and functional properties of buffalo (Bubalus bubalis) bone gelatin extracted using acid pre-treatment. Future Foods, 10(August), 100428. https://doi.org/10.1016/j.fufo.2024.100428
60. Yin, Q., Shi, H., Zhao, Y., Yu, G., Wu, H., Xia, G., & Yang, T. (2025). Physiochemical and functional properties of gelatin obtained from frigate mackerel (Auxis thazard), skipjack tuna (Katsuwonus pelamis), Longtail tuna (Thunnus tonggol) and yellowfin tuna (Thunnus albacares) skin. Food Chemistry: X, 27, 102360. https://doi.org/10.1016/j.fochx.2025.102360
61. Yu, E., Pan, C., Luo, X., Ruan, Q., Chen, W., Fang, Y., Wang, K., Qin, Y., Lv, M., & Ma, H. (2023). Structural characteristics, component interactions and functional properties of gelatins from three fish skins extracted by five methods. International Journal of Biological Macromolecules, 248(May), 125813. https://doi.org/10.1016/j.ijbiomac.2023.125813
62. Yuan, Z., Ye, X., Hou, Z., & Chen, S. (2024). Sustainable utilization of proteins from fish processing by-products: Extraction, biological activities and applications. Trends in Food Science & Technology, 143, 104276. https://doi.org/10.1016/j.tifs.2023.104276
63. Zhou, P., & Regenstein, J.M. (2006). Determination of total protein content in gelatin solutions with the Lowry or Biuret assay. Journal of Food Science, 71(8), C474–C479. https://doi.org/10.1111/j.1750-3841.2006.00151.x