Eco-friendly, pH-sensitive curcumin-loaded sodium alginate/hydroxyapatite/quaternary ammonium chitosan microspheres with enhanced antibacterial and antioxidant activities for fruit preservation

The development of intelligent responsive reactive packaging materials with natural polymers shows excellent potential in food preservation. In this study, eco-friendly, pH-sensitive sodium alginate (SA)/hydroxyapatite (HA)/quaternary ammonium chitosan (HACC) composite microspheres loading curcumin (CUR) with excellent antibacterial and antioxidant activities were successfully synthesized. Scanning electron microscopy (SEM) and nitrogen adsorption/desorption tests indicated that the doping of HA substantially increased the specific surface area and pore volume of the microspheres. The loading experiments showed that the efficiency of the microspheres was significantly increased by 49.47 % and 55.10 %, respectively, when HA and HACC were incorporated into the SA network. The release test results suggested that the release rate of SA/HA/HACC microspheres loading CUR (SA/HA/HACC@CUR) increased as the pH decreased, demonstrating notable pH-responsive release characteristics. DPPH free radical scavenging experiments demonstrated that the SA/HA/HACC@CUR had excellent and long-lasting antioxidant capacity. The antibacterial experiments revealed that the SA/HA/HACC@CUR had excellent antibacterial properties, with inhibition rates of 88.73 % and 92.52 % against E. coli and S. aureus, respectively. Making coatings out of microspheres could effectively slow down the rotting and deterioration of cherry tomatoes during storage, suggesting that microspheres with intelligent responses have a broad application prospect in fruit preservation.