Development of an antibacterial hydrogel by κ-carrageenan with carvacrol/hydroxypropyl-β-cyclodextrin composite and its application for strawberry preservation

In this study, an active gel of κ-carrageenan (KC) loaded with carvacrol/hydroxylpropyl-β-cyclodextrin (CAR/HPβCD) composite was prepared, its antibacterial property and application in strawberry preservation were evaluated. The successful preparation of CAR/HPβCD composite was verified by Fourier transform infrared spectroscopy (FT-IR) and 1 H NMR, and the embedding mechanism was further elucidated by the molecular docking and molecular dynamics simulation. Then the CAR/HPβCD composites were incorporated into KC to fabricate the active gels. The KC-based gels with great thermal reversibility presented sol states at high temperature and formed gels upon cooling. During the cooling process, KC transformed from random coil conformations to rigid helical rods. A large three-dimensional network structure was eventually constructed through the continuous aggregation of the double helices. It showed that the concentrations of the composites affected both the microstructures and properties of the gels. Low composite concentrations were beneficial to increase the hardness, gumminess and chewiness of the gels, while high composite concentrations could remarkably improve the water retention, freeze-thaw stability and in vitro antibacterial activity of the gels. The antibacterial activity of the gel containing 20% CAR/HPβCD composite against staphylococcus aureus ( S. aureus) could last 15 days. Furthermore, the active gel used as a fresh-keeping coating for strawberry preservation could effectively delay the decline of weight, titratable acidity (TA), total soluble solids (TSS) and firmness of strawberries during the storage time, and reduce the number of rotten strawberries by three quarters compared with the control group within 7 days. The active gel reported in this study was a promising material for food preservation.