Cryoprotective effects of fish skin collagen peptide on frozen gluten proteins: From conformational changes to functional properties.

Fish skin collagen peptides (FSCP) are mainly extracted from fish processing residues and exhibit outstanding biological activity and excellent functional properties. This study conducted a systematic evaluation of the effects of FSCP incorporation (0-2.0%, w/w) on the multiscale structural characteristics and functional performance of gluten proteins during freezing. Results demonstrated that FSCP exhibited pronounced ice recrystallization inhibition activity, effectively suppressing water migration, reducing the content of freezable water, and preserving the structural integrity of gluten proteins during freezing. On day 28 of freezing, 1.5% FSCP significantly increased the proportion of bound water than the control. Specifically, disulfide bond content increased by 69.69%, whereas intrinsic fluorescence intensity and median particle size decreased by 17.71% and 36.40%, respectively. Analysis of noncovalent interactions revealed that ionic and hydrogen bonds increased by 121.07% and 34.32%, respectively, whereas hydrophobic interactions decreased by 34.73%. FSCP addition enhanced water-holding capacity by 37.54% but reduced oil-holding capacity by 25.50%. Meanwhile, the emulsifying properties have also been enhanced. Rheological measurement further indicates storage and loss modulus increased significantly, while creep strain decreased slightly, reflecting improved viscoelastic behavior. Microstructural analysis further confirmed that FSCP contributed to a more densely packed and continuous gluten protein matrix. These effects are likely attributable to FSCP limiting water mobility through hydrogen bonding, thereby inhibiting ice crystal formation and recrystallization during freezing. Overall, as a novel and highly effective cryoprotectant, FSCP can stabilize protein network structures and enhance their functional properties, demonstrating significant application potential and offering a promising strategy for mitigating freeze-induced deterioration in frozen flour-based foods.