Fish Habitat Temperature Pre-Programs Surimi Gel Quality, Study Finds

The quality of surimi, the washed fish-protein concentrate used to make high-value reconstructed seafood products, may be written into the evolutionary history of the fish itself. A new laboratory study compared surimi made from three marine species living in sharply different thermal environments — golden threadfin bream (Nemipterus virgatus), red sea snapper (Pagrosomus major) and Alaska pollock (Theragra chalcogrammus) — and found that each species reached its best gel quality under a different heating regime. The warm-adapted species set best at 40 °C for one hour, while the cold-water pollock preferred a gentler 25 °C setting for two hours. The findings suggest that processing schedules should be matched to the thermal ecology of the raw material rather than applied uniformly across species.

Surimi production relies on heat-induced gelation, in which myofibrillar proteins, dominated by myosin, unfold and cross-link into a three-dimensional network that traps water and gives the product its characteristic springy texture. The process conventionally passes through three sequential stages: suwari at 25–40 °C, where the paste first sets; modori at 50–70 °C, a notorious gel-weakening zone; and kamaboko above 70 °C, where the structure becomes permanently fixed. Industrial practice typically uses either a single high-temperature stage at 75–95 °C or a two-stage process in which a low-temperature setting step at 25–50 °C precedes high-temperature cooking. Both strategies aim to move the paste quickly through the modori window, where endogenous proteases can soften and degrade the forming gel. Where a species’ proteins and enzymes sit within these temperature windows, the researchers reasoned, depends on the waters it evolved in.

That reasoning rests on a well-documented biological principle: as cold-blooded vertebrates, fish co-evolve extensively with their surrounding water temperature, and this shapes both enzymatic metabolic rates and the conformational structures of large biomolecules. Previous work has shown that the thermal denaturation temperature of structural proteins such as myosin rises by roughly 0.5–1.2 °C for every 10 °C increase in environmental temperature. Studies in freshwater fish, including silver carp whose habitat water temperature controls the protein unfolding rate and thereby the most effective comminution time for surimi production, had already linked habitat temperature to protein behavior. What remained largely unexplored was whether the same thermal imprint shapes heat-induced gelation in marine species, which dominate commercial surimi processing and generally show stronger gel-forming ability than freshwater fish.

To find out, the team purchased fish of the three species, prepared frozen surimi from them in three independent batches per species, and mixed the dewatered mince with cryoprotectants — 4% sucrose, 4% sorbitol and 0.2% composite phosphates — before vacuum-packing and storage at −18 °C. The materials were then characterized with an extensive analytical array. Differential scanning calorimetry measured the temperatures at which proteins denatured; SDS-PAGE mapped the protein composition; turbidity assays tracked myosin aggregation during one hour of heating at 40 °C; and fluorogenic assays quantified the residual activities of cathepsin B, a gel-degrading protease, and endogenous transglutaminase, a cross-linking enzyme, after preincubation at temperatures from 20 to 60 °C. Dynamic rheology followed the elastic modulus (G′) of salted pastes during a temperature sweep from 10 to 90 °C, and finished gels — set at 25 °C or 40 °C for one, two or four hours and then cooked at 90 °C for 30 minutes — were assessed for strength, water holding capacity, chemical bonding forces, water mobility by low-field nuclear magnetic resonance, magnetic resonance imaging, TCA-soluble peptide content and protein banding patterns.

The thermal analysis delivered a clean hierarchy. Golden threadfin bream, whose habitat spans 22–30 °C, showed the highest onset and peak denaturation temperatures and the largest enthalpy changes across three thermal transitions, with its first peak at about 49.2 °C and an enthalpy of 0.28 J/g. Red sea snapper, from 12–28 °C waters, fell in between, with a first peak near 49.8 °C, while Alaska pollock, adapted to −2–8 °C, denatured at the lowest temperatures, its first transition peaking near 34.9 °C with only 0.07 J/g. SDS-PAGE of the raw surimi showed that pollock carried the most intense myosin heavy chain band, suggesting abundant gel-forming potential, since MHC is the primary functional protein responsible for cross-linking into a dense three-dimensional network. This thermal ordering mirrors the freshwater pattern reported earlier and supports the idea that environmental temperature induces adaptive shifts in protein thermal stability across marine and freshwater species alike.

Protein aggregation behavior, however, proved more nuanced than thermal stability alone. Turbidity of golden threadfin bream myosin rose rapidly during the first ten minutes of heating and then plateaued, consistent with its higher thermal stability limiting further unfolding at 40 °C. Pollock myosin, despite its lower denaturation temperature, showed higher turbidity, peaked at about 15 minutes and then declined slightly — a drop the authors attribute to the formation of larger flocs that reduce the number of suspended light-scattering particles, rather than to refolding. Red sea snapper myosin turbidity climbed continuously throughout the hour. Because surface hydrophobicity, sulfhydryl accessibility, surface charge and aggregate-size distribution were not directly measured, the researchers present these mechanistic explanations as plausible rather than definitive, and they caution that turbidity reflects aggregate formation and physical state, not thermal stability itself.

Enzyme behavior followed the ecological logic. Cathepsin B activity in all three surimis rose and then fell with heating temperature, but the peaks sat at different points: Alaska pollock’s enzyme was most active at 20–30 °C, whereas golden threadfin bream retained higher activity above 30 °C, with activity in all samples declining sharply beyond 60 °C. Endogenous transglutaminase peaked at 40–50 °C in the two warm-adapted species but at just 30 °C in pollock, dropping off steeply at higher temperatures. The temperature windows in which gel-building cross-linking and gel-destroying proteolysis are most active therefore differ systematically between cold- and warm-water fish, echoing earlier reports that optimal TGase temperatures and setting behavior vary among species.

Those differences translated directly into processing outcomes. Golden threadfin bream and red sea snapper achieved maximum gel strength and water holding capacity after one hour of setting at 40 °C; extending setting at that temperature significantly weakened the gels, apparently because over-activated endogenous proteases degraded the protein network. Alaska pollock behaved in nearly the opposite way: its strongest, most water-retentive gels formed at 25 °C, with strength improving significantly as setting extended from one to two hours and showing no further significant improvement at four hours. Notably, pollock surimi outperformed both other species in absolute gel strength across all treatments, which the authors attribute to its abundant myosin heavy chain, high endogenous transglutaminase content and comparatively low protease levels. Rheological traces told a matching story: the warm-water species showed an initial weak network below 34 °C, a G′ minimum near 43–45 °C corresponding to protease-driven modori softening, and a sharp rise as covalent and non-covalent cross-links consolidated, whereas pollock displayed a distinct early peak at 35 °C and an intermediate terminal G′ — below bream but above snapper.

Water measurements reinforced the picture. Low-field NMR showed that immobilized water dominated all gels, with the immobilized fraction P21 exceeding 97% in every treatment, but the mobility of the remaining fractions tracked gel quality closely. Pollock gels set at 25 °C for four hours combined the highest water holding capacity with the highest P21 and the shortest T21 and T22 relaxation times — signs of a dense network tightly confining water — while the same species set at 40 °C for two hours showed the lowest P21 and highest P22. MRI proton maps were brighter for pollock gels overall and peaked in brightness at each species’ optimal condition. Chemical interaction assays found hydrophobic interactions present at significantly higher concentrations than all other forces, with hydrophobic association rising continuously in red sea snapper gels to a peak after two hours at 40 °C, likely as cathepsin-driven hydrolysis exposed buried hydrophobic residues, while ionic and hydrogen bonds steadily degraded with heating across all samples.

Protein degradation data told a consistent story. Setting at 40 °C accelerated the accumulation of TCA-soluble peptides — a marker of proteolytic breakdown — in all three species as treatment time increased from one to four hours, while 25 °C setting held degradation in check or reduced it. SDS-PAGE revealed weakening of the myosin heavy chain band in the warm-water species during prolonged 40 °C setting, consistent with proteolysis, whereas pollock showed weaker heavy chain bands at 25 °C, possibly reflecting TGase-driven cross-linking into aggregates too large to enter the resolving gel. The authors caution that band intensity can be influenced by proteolysis, aggregation and incomplete solubilization simultaneously, and that actin bands changed little, indicating greater stability. The study’s correlational analysis linking enzyme activities to gel properties is explicitly exploratory: with only three species-level observations, associations such as the near-perfect correlation between cathepsin B activity and terminal G′ at 90 °C (r = 0.9995) cannot establish causation and may partly reflect species differences in protein composition. Even so, the overall message is clear: gelation behavior in marine surimi is not merely a processing outcome but appears pre-programmed by the ecological thermal history of each species, and quality control in seafood manufacturing may improve by tailoring setting temperatures and times to the thermal imprint of the fish on the line.

Subject of Research: Effects of habitat temperature and gelation method on heat-induced gelation of surimi from three marine fish species

Article Title: Effect of gelation methods on the gel properties of surimi from marine fish adapted to different thermal environments

Article References: Wang, Y., Wang, Z., Benjakul, S., Shen, X., You, J., Liu, R., Jia, D., & Yin, T. (2026). Effect of gelation methods on the gel properties of surimi from marine fish adapted to different thermal environments. Journal of Agriculture and Food Research, 32, Article 103384. https://doi.org/10.1016/j.jafr.2026.103384

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103384

Keywords: surimi, marine fish, gelation, thermal adaptation, myosin, cathepsin B, transglutaminase, Alaska pollock, water holding capacity, rheology, protein denaturation, food processing