Sardine surimi has long been the underdog of the surimi industry. Unlike the white-fleshed fish that dominate commercial surimi production, dark-fleshed tropical species such as sardines are abundant, economical, and rich in heart-healthy polyunsaturated fatty acids — but they are also notoriously poor at forming the strong, elastic gels that surimi products demand. A new study published in Case Studies in Chemical and Environmental Engineering reports a remarkably simple solution drawn from two humble tropical plants, and the underlying chemistry may reshape how the seafood industry thinks about clean-label additives.
The research, led by Muh Ali Arsyad and colleagues at Politeknik Pertanian Negeri Pangkajene Kepulauan in Indonesia, examined freeze-dried aqueous leaf extracts of kenikir (Cosmos caudatus) and binahong (Anredera cordifolia), two edible plants widely available across tropical Southeast Asia and traditionally valued in folk medicine. Both plants are rich in phenolic compounds, and because the extraction uses nothing but water as the solvent, the resulting powders avoid the residues and sustainability problems associated with organic solvent extraction. That combination of bioactivity, green processing, and ready dispersibility in food matrices made them ideal candidates for a dual task: strengthening the gel network of sardine surimi and protecting its fragile lipids from oxidation.
The problem the researchers set out to solve is rooted in the biochemistry of dark-fleshed fish. Sardine muscle contains high levels of hemoproteins such as myoglobin and hemoglobin, along with abundant polyunsaturated fatty acids that are exquisitely vulnerable to peroxidation. During thermal processing, lipid oxidation generates reactive aldehydes and radicals that attack myofibrillar proteins, interfering with the protein–protein interactions needed to build a cohesive three-dimensional gel network. The result is surimi with lower gel strength, reduced storage stability, and faster quality deterioration than products made from white-fleshed species. Polyphenols offer a potential way out, because they can both quench oxidation chains and engage proteins through hydrogen bonding, hydrophobic interactions, and covalent cross-linking — modifying protein conformation in ways that favor network formation rather than degradation.
To prepare the extracts, the team dried fresh leaves at 25 to 40 degrees Celsius in a cold-air dryer for 48 hours, ground and sieved them to a fine powder, then stirred 50 grams of powder into 500 milliliters of distilled water for an hour. After centrifugation, filtration, freezing, and freeze-drying, they had two additive powders ready for testing. Chemical characterization revealed a decisive difference between the two plants. Binahong leaf extract, or BLE, delivered a total phenolic content of 209.54 milligrams of gallic acid equivalents per gram of dry extract, roughly 1.75 times the 120.00 milligrams measured for kenikir leaf extract, or KLE. Antioxidant assays painted the same picture across four complementary mechanisms. BLE scavenged ABTS radicals at 55.49 micromoles of Trolox equivalents per gram versus 32.31 for KLE, and DPPH radicals at 47.17 versus 25.12. Its ferric reducing antioxidant power was 64.66 compared with 36.41 micromoles of Trolox equivalents per gram, and its metal chelating activity — critical because iron ions catalyze the Fenton reactions that drive lipid oxidation in fish muscle — reached 10.78 micromoles of EDTA equivalents per gram, more than three times the KLE value.
With the extracts characterized, the researchers chopped frozen sardine surimi with 2.5 percent salt to solubilize myofibrillar proteins, then added BLE or KLE at concentrations ranging from 0.05 to 0.30 percent by weight. The pastes were encased, set at 40 degrees Celsius for 30 minutes, cooked at 90 degrees Celsius for 20 minutes, and chilled. Breaking force and deformation — the mechanical hallmarks of gel strength and elasticity — followed a clear dose-dependent pattern with an optimum. Control gels broke at roughly 56.6 grams of force, but BLE at 0.20 percent pushed that figure to about 73.5 grams, a peak that fell away again at higher doses. KLE required more: its optimum arrived at 0.25 percent, with a breaking force near 67.9 grams. Deformation followed the same shape, peaking at about 1.4 millimeters for BLE-0.2 and 1.3 millimeters for KLE-0.25. Expressible moisture, a measure of how readily water escapes the gel under pressure, dropped from around 35 percent in the control to 23 percent at the BLE optimum and 24 percent at the KLE optimum, evidence that both extracts produced tighter matrices that immobilized water more effectively. Whiteness, importantly, was unaffected across the entire dosing range — a practical advantage for consumer acceptance, since the aqueous extraction leaves chlorophyll behind and the low doses contribute negligible color.
Texture profile analysis at the selected working concentrations confirmed these mechanical gains. Hardness rose from 651.70 grams in the control to 737.44 grams with 0.20 percent BLE, the highest value recorded, while 0.25 percent KLE produced an intermediate 701.10 grams. Springiness climbed from 0.66 centimeters in the control to 0.86 centimeters with BLE-0.2, and gumminess and chewiness rose in parallel, reaching 221.89 grams and 129.78 gram-centimeters respectively. Cohesiveness remained statistically unchanged, indicating that the extracts altered the strength and malleability of the gels rather than their internal bonding ratios. Beyond the optimal doses, all parameters declined toward control values, a signature of over-crosslinking: once protein binding sites approach saturation, excess polyphenols promote aggregation that disrupts the homogeneity of the gel network and weakens its mechanical performance.
The molecular basis for these effects emerged from Fourier transform infrared attenuated total reflection spectroscopy. The addition of BLE and KLE produced no new chemical bands, but it shifted and reshaped existing ones. Bands in the 3200 to 3400 per centimeter region, associated with amide A and overlapping hydroxyl stretching, shifted slightly to lower wavenumbers, indicating strengthened hydrogen bonding between phenolic hydroxyl groups and the carbonyl and amine groups of myofibrillar proteins. The amide I band near 1656 per centimeters held its position but changed in relative intensity, and the amide II band near 1544 per centimeters remained stable, showing that the peptide backbone was not chemically damaged — the extracts acted as modulators of intermolecular interactions rather than denaturants. Meanwhile, increased intensity of carbon–oxygen stretching bands in the 1000 to 1100 per centimeter range signaled phenolic groups integrated into the protein matrix, consistent with oxidation of phenolics into quinones that form covalent cross-links with nucleophilic residues such as lysine and cysteine during heating.
Deconvolution of the amide I band revealed the conformational story behind the improved textures. The control gel contained 54.79 percent beta-sheet, 24.96 percent alpha-helix, 9.66 percent random coil, and 10.59 percent beta-turn. The KLE-treated gel shifted modestly toward alpha-helix content, but the BLE-treated gel showed the most pronounced transformation: beta-sheet content rose to 59.18 percent, while alpha-helix and random coil fell to 22.33 and 7.38 percent respectively. The conversion of alpha-helical domains into beta-sheet conformations is a hallmark of thermal myosin unfolding and aggregation, and it exposes reactive residues that drive intermolecular association. The elevated beta-sheet fraction in the BLE gel therefore reflects a higher degree of protein–protein organization, stabilized by extensive hydrogen bonding and regulated by the polyphenols. This structural rearrangement correlated directly with function. Dynamic rheology, monitoring the elastic modulus during heating from 20 to 90 degrees Celsius, showed that the BLE gel developed the highest storage modulus during the sharp gelation phase between roughly 50 and 70 degrees Celsius, where myosin heads denature and reactive groups drive aggregate formation. Scanning electron microscopy closed the loop visually: while the control gel displayed a rough, poorly organized matrix with large, uneven pores, the BLE gel exhibited a dense, continuous, homogeneous network with small, uniformly distributed cavities — a microstructure that stores elastic energy efficiently and traps water within microcapillary spaces.
The antioxidant payoff emerged during refrigerated storage. Over twelve days at 4 degrees Celsius, peroxide values and thiobarbituric acid-reactive substances rose in all samples, but the control gels showed significantly higher oxidation at days 4 and 8, reflecting the classic progression from primary lipid hydroperoxides to secondary products such as malondialdehyde. Gels containing BLE suppressed both indices most effectively, a result the researchers attribute to a combination of intrinsic radical scavenging, metal chelation that curbs Fenton chemistry, and a denser gel matrix that physically limits oxygen diffusion. By preserving myofibrillar proteins from reactive aldehydes, BLE also protected the structural integrity that underpins gel texture, suggesting the additive improves both immediate quality and shelf life.
Taken together, the study delivers a unified molecular mechanism: polyphenols from water-extracted tropical leaves strengthen sardine surimi gels through reinforced hydrogen bonding and controlled covalent cross-linking, driving a favorable beta-sheet transition that builds a tighter, more elastic network while simultaneously shielding the product from oxidative decay. Binahong leaf extract proved the more potent additive, achieving maximum effect at 0.20 percent versus 0.25 percent for kenikir, mirroring its higher phenolic content and antioxidant capacity. For an industry seeking to upgrade abundant but underutilized dark-fleshed pelagic fish into value-added surimi products, the findings point toward additives that are effective, colorless at working doses, and produced with nothing more exotic than water — a genuinely green chemistry recipe for better seafood.
Subject of Research: Dual-function aqueous plant leaf extracts as natural additives for improving gel quality and oxidative stability of sardine surimi
Subject of Research: Chemistry
Article Title: Dual-functionality of aqueous plant extracts of Cosmos caudatus and Anredera cordifolia in Sardine Surimi: Enhancing gel network formation and retarding lipid oxidation via Protein–Polyphenol interactions
Article References: Arsyad, M. A., Syukroni, I., Malle, S., & Arfini, F. (2026). Dual-functionality of aqueous plant extracts of Cosmos caudatus and Anredera cordifolia in Sardine Surimi: Enhancing gel network formation and retarding lipid oxidation via Protein–Polyphenol interactions. Case Studies in Chemical and Environmental Engineering, 14, Article 101473. https://doi.org/10.1016/j.cscee.2026.101473
Image Credits: AI Generated
DOI: 10.1016/j.cscee.2026.101473
Keywords: sardine surimi, protein–polyphenol interactions, binahong leaf extract, kenikir leaf extract, lipid oxidation, gel network formation, FTIR secondary structure, tropical plant additives, clean-label food additives, water-holding capacity, antioxidant activity, food texture analysis
Cite Scienmag News
APA MLA Chicago
Bethany Barker. (September 4, 2026). Plant polyphenol extracts boost surimi gel quality and prevent oxidation. Scienmag. https://scienmag.com/plant-polyphenol-extracts-boost-surimi-gel-quality-and-prevent-oxidation/
Bethany Barker. “Plant polyphenol extracts boost surimi gel quality and prevent oxidation.” Scienmag, 4 September 2026, https://scienmag.com/plant-polyphenol-extracts-boost-surimi-gel-quality-and-prevent-oxidation/. Accessed 4 September 2026.
Bethany Barker. “Plant polyphenol extracts boost surimi gel quality and prevent oxidation.” Scienmag. September 4, 2026. https://scienmag.com/plant-polyphenol-extracts-boost-surimi-gel-quality-and-prevent-oxidation/
Copy citation Download RIS
Tags: antioxidant properties of plant phenolicsbioactive compounds from edible plantsbioactive phenolic compounds in edible plantseffects of plant extracts on seafood gel qualityeffects of plant-based antioxidants on seafood qualitygreen extraction methods for food additivesgreen extraction methods for food ingredientsimproving surimi gel texture with natural extractsimproving surimi texture with plant extractsnatural antioxidants in seafoodnatural food preservativesPlant polyphenol extractsplant-derived clean-label food preservativessardine surimi processingseafood lipid oxidation preventionsurimi gel enhancementsustainable food additive developmenttraditional medicinal plants in food industrytropical plant extracts in seafood processingtropical plant-based food additives
