Development of pH-stimulus responsive gelatin hydrogel loaded with bacteriocin bifidocin A for salmon preservation

Bacteriocins exhibit excellent antibacterial activity, effectively inhibiting the growth and metabolism of microorganisms. However, achieving the continuous, controlled release of bacteriocin to effectively utilize their antibacterial potential remains a challenge. Therefore, this study employed the rapid gelling properties of gelatin to prepare a pH-responsive oxidized konjac glucomannan (OKGM)-bifidocin A/gelatin hydrogel for salmon preservation. The -CHO groups in the OKGM were bonded to the -NH₂ group in bifidocin A via a Schiff base reaction, allowing the bifidocin A to be released in response to pH changes. The FT-IR, FE-SEM, and antibacterial activity results demonstrated the successful incorporation of OKGM-bifidocin A grafts into the gelatin hydrogel, with an optimal OKGM-bifidocin A graft-to-gelatin ratio of 2:1. The OKGM-bifidocin A/gelatin-2 hydrogel exhibited excellent swelling capacity (with a balanced swelling rate of 291%) and strong antibacterial properties. Furthermore, the bifidocin A exhibited marked pH-dependent release characteristics (pH 5-8, range from 25% to 87%). The salmon preservation experiment demonstrated that the OKGM-bifidocin A/gelatin-2 hydrogel coating extended the shelf life by 12 d by preserving its microbiological, physicochemical, and sensory quality. This study provides a reference for the encapsulation application of food-active packaging materials and bacteriocins.