Non-radical synthesis of chitosan-quercetin polysaccharide: Properties, bioactivity and applications.

Quercetin-chitosan (QCS) polysaccharide was synthesized via non-radical reaction using L-valine-quercetin as the precursor. QCS was systematically characterized and demonstrated amphiphilic properties with self-assembling ability. In-vitro activity studies confirmed that quercetin grafting does not diminish but rather increases antimicrobial activity of the original chitosan (CS) and provided the modified polysaccharide with antioxidative properties. QCS applied as a coating on fresh-cut fruit reduced microbial spoilage and oxidative browning of coated melon and apple, respectively. Notably, QCS-based coatings prevented moisture loss, a major problem with fresh produce (2%, 12% and 18% moisture loss for the QCS-coated, CS-coated and uncoated fruit, respectively). The prepared QCS polysaccharide provides advanced bioactivity and does not involve radical reactions during its synthesis, therefore, it has good potential for use as a nature-sourced biocompatible active material for foods and other safety-sensitive applications.

In Situ Grafting of Silica Nanoparticle Precursors with Covalently Attached Bioactive Agents to Form PVA-Based Materials for Sustainable Active Packaging.

Sustainable antibacterial-antioxidant films were prepared using in situ graftings of silica nanoparticle (SNP) precursors with covalently attached bioactive agents benzoic acid (ba) or curcumin (cur) on polyvinyl alcohol (PVA). The modified PVA-SNP, PVA-SNP-ba and PVA-SNP-cur films were characterized using spectroscopic, physicochemical and microscopic methods. The prepared films showed excellent antibacterial and antioxidant activity, and increased hydrophobicity providing protection from undesired moisture. The PVA-SNP-ba films completely prevented the growth of the foodborne human pathogen Listeria innocua, whereas PVA-SNP-cur resulted in a 2.5 log reduction of this bacteria. The PVA-SNP-cur and PVA-SNP-ba films showed high antioxidant activity of 15.9 and 14.7 Mm/g TEAC, respectively. The described approach can serve as a generic platform for the formation of PVA-based packaging materials with tailor-made activity tuned by active substituents on silica precursors. Application of such biodegradable films bearing safe bioactive agents can be particularly valuable for advanced sustainable packaging materials in food and medicine.