pH sensitive cold-set hydrogels based on fibrinogen hydrolysates/carrageenan: Insights of rheology, coacervation, microstructure and antioxidant ability

In order to investigate the effect of pH treatments on the coacervation mechanism of fibrinogen hydrolysates and carrageenan complex, the cold-set hydrogels of carrageenan and fibrinogen hydrolysates derived from the hydrolysis of chymotrypsin, alcalase and flavourzyme were prepared under different pH; mechanical strength, rheological properties, gelling structure, morphological observation, and chemical action force were investigated, and the antioxidant capacity of the hydrogels was further evaluated in meat preservation model. The results indicated that the hydrogels of carrageenan and fibrinogen hydrolysates derived from the hydrolysis of alcalase (AHs) showed the largest gel strength and the best viscoelasticity at pH 7.0 compared with other pH and hydrolase treatments. FTIR spectrum revealed that AHs showed more β-sheet and β-turn at pH 7.0 among all treatments. The interaction forces of these hydrogels showed various under different pH and hydrolase treatments, and the network of AHs hydrogels at pH 7.0 was mainly stabilized by electrostatic interaction and hydrophobic interaction. SEM and AFM demonstrated that the more regular three-dimensional network with smaller pore sizes was formed in AHs at pH 7.0 compared with pH 5.0 and pH 9.0. The AHs showed the largest scavenging ability for DPPH radicals (72.4%) at pH 7.0 in vitro, and the coated meat samples with AHs significantly increased the preservation times of fresh pork and dry-cured ham during the storage by inhibiting the increase of TBARS, TVB-N, and metmyoglobin. The finding of this work is expected to broaden the application of fibrinogen hydrolysate hydrogels into the field of food industry.