Fibrinogen hydrolysate-carrageenan hydrogels filled with carboxymethyl chitosan-cinnamaldehyde: Insights of the interaction mechanism, structure, stability and antibacterial capacity

Emulsion-filled hydrogels have recently attracted interest against foodborne pathogens. However, the relationship between fibrinogen hydrolysate-carrageenan (AHs-C) and carboxymethyl chitosan-cinnamaldehyde (CMCS-CAL), as well as the antibacterial effect, were not investigated during the formation of emulsion-filled hydrogels. To explore the interaction mechanism between AHs-C and CMCS-CAL as well as the antimicrobial effect of the emulsion-filled hydrogels, the emulsion-filled hydrogels were fabricated using different ratios of AHs-C and CMCS-CAL. The morphological characteristics, structural changes, antimicrobial capacity, and release behavior of cinnamaldehyde were evaluated. The rheological results showed that the hydrogel of AHs-C/CMCS-CAL-5:1 exhibited the highest crossover strain value (23.7%) and formed more stable network structure compared with other groups (AHs-C, AHs-C/CMCS-CAL-10:1, 20:1, 40:1). FTIR and XPS showed that CMCS-CAL was bonded to AHs-C via Schiff bases, hydrogen bonds and electrostatic interactions, where AHs-C/CMCS-CAL-5:1 showed more interaction between AHs-C and CMCS-CAL, and higher thermal stability compared with other groups. The inhibition of AHs-C/CMCS-CAL-5:1 against Staphylococcus aureus and Salmonella enteritidis reached 99.9%, and the release kinetics of cinnamaldehyde demonstrated that the release of cinnamaldehyde in AHs-C/CMCS-CAL transitioned from dissolution diffusion to Fick diffusion in gastrointestinal simulation experiments, which was mainly responsible for the sustaining inhibition of foodborne pathogens.