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.

Covalent linkage of bioactive volatiles to a polysaccharide support as a potential approach for preparing active edible coatings and delivery systems for food products.

In this study, a potential of covalent linkage approach for developing active edible coatings was examined. Vanillin and trans-cinnamaldehyde were bound to chitosan by Schiff base reaction and reductive amination. The modified polysaccharides were comprehensively characterized and applied as active coatings on fresh-cut melon. The covalent linkage allowed overcoming solubility problems with the lipophilic vanillin and cinnamaldehyde and neutralizing their volatility, producing well-adhered coatings that enhanced fruit quality and storability without sensorial impairment. The attached hydrophobic moieties also provided new polysaccharides with self-assembling ability. Their aggregates were loaded with antimicrobial citral and added to mandarin juice, resulting in up to 6 log CFU/mL microbial count reduction. Thus, the covalent linkage concept offers several advantages, especially when hydrophobic or volatile active agents are used. Further developed, it may become a safe and effective tool for the formation of advanced active edible coatings and delivery vehicles for direct applications on food products.

Enhancement of agricultural produce quality and storability using citral-based edible coatings; the valuable effect of nano-emulsification in a solid-state delivery on fresh-cut melons model.

Emulsification approach is widely employed to deliver beneficial agents to liquid food products, whereas utilizing emulsions with solid food is scarce. In this research, coarse and nano emulsions of citral were prepared and embedded in chitosan or carboxymethyl cellulose (CMC) polysaccharides to form active edible coatings for solid-state delivery. Polysaccharides stabilized the emulsions by electrostatic interactions, while chitosan also prevented coalescence. The nano emulsion based films showed a more organized and dense morphology (E-SEM), higher water vapor barrier, better mechanical features (strength, elasticity and Young modulus) than the coarse ones. When applied on a solid food model, fresh-cut melons, the nanoemulsified edible coatings demonstrated a superior antimicrobial protection (up to a 5-log reduction) and significantly extended product's storability (up to 13 days). The presented approach could be further employed for the delivery of other beneficial agents (nutrients, aroma, antimicrobial, antioxidants) to solid food products, contributing a general progress in this field.

Potential of chitosan from mushroom waste to enhance quality and storability of fresh-cut melons.

The possibility of usage mushroom industry wastage, as a source of antimicrobial biopolymer chitosan to form active edible coatings was studied. It was found that the champignon stipe, an underutilized part of the mushroom, gave rise to a higher chitosan yield than caps (176 vs. 105 mg/g). Fungal chitosan caused a total growth inhibition of the Saccharomyces cerevisiae yeast and Escherichia coli bacteria at concentrations of 1% and 2%, respectively. The fungal chitosan-based edible coatings were applied on fresh-cut melons and found to enhance fruit firmness, inhibit off-flavors and reduce the microbial counts (up to 4 log CFU/g). Volatiles profile showed the coated melons have a higher content of esters responsible for fruit flavor (79.93% and 57.15% for fungal chitosan coated melon and uncoated melon, respectively). This study demonstrates that waste from the mushroom industry can be utilized for the production of non-animal sourced chitosan to form active edible coatings.