Optimising chitosan–pectin hydrogel beads containing combined garlic and holy basil essential oils and their application as antimicrobial inhibitor

Chitosan–pectin hydrogel beads that trap and release the maximal amount of combined garlic and holy basil essential oils to inhibit food microorganisms were developed based on the central composite design, with chitosan (0.2–0.7% w/v), pectin (3.5–5.5% w/v) and calcium chloride (CaCl₂) (5.0–20.0% w/v) contents. The optimal bead consisted of 0.3–0.6% w/v chitosan, 3.9–5.1% w/v pectin and 8.0–17.0% w/v CaCl₂, which had a high encapsulation efficiency (62.16–79.06%) and high cumulative release efficiency (31.55–37.81%) after storage at 5 °C for 15 days. Optimal hydrogel beads were packed into a cellulose bag to evaluate antimicrobial activity by the disc volatilisation method. The beads inhibited Bacillus cereus, Clostridium perfringens, Escherichia coli, Pseudomonas fluorescens, Listeria monocytogenes and Staphylococcus aureus but did not affect Lactobacillus plantarum and Salmonella Typhimurium. The oil-containing beads could potentially be applied in food packaging to inhibit the mentioned microorganisms.