Development of multifunctional fruit packaging by incorporating starch aldehyde-quercetin conjugate into chitosan coating films

In this research, quercetin (QR) was successfully conjugated with Qingke (Tibetan barley) starch aldehyde (DAS) in an acid-catalyzed condensation reaction. The Qingke DAS-QR conjugates were characterized by UV–vis spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and powder X-ray diffraction. They were demonstrated to possess antioxidant properties (especially at 0.3-0.5 mg/mL) by DPPH and ABTS radical scavenging activity tests, antibacterial properties (at 0.045 mg/mL) against S. aureus by colony count determination experiment, and non-toxic properties (at 0.02-0.10 mg/mL) by RAW264.7 cell cytotoxicity teseting. The conjugates were incorporated into CS coating films to develop active packaging films. The structural, physical and functional properties of CS/DAS-QR films were determined. FT-IR analysis showed that Qingke DAS-QR conjugates formed hydrogen bonding with CS film matrices, which improved the compactness of the film structures. The study of light transmittance, water vapor permeability, thermal property, mechanical property, antioxidant and antibacterial properties indicated that the light and water vapor blocking property, thermal stability, TS, antioxidant and antibacterial ability of CS coating film were increased by addition of the conjugates (3%, dosage calculated by CS weight). The fruit preservation experiments confirmed that the composite coating film CS/DAS-QR Ⅲ effectively maintained the appearance quality, reduced the respiratory rate, delayed the loss of weight, firmness and TA, and postponed MDA accumulation in citrus. These desirable performances promise that the developed composite coating film is an active packaging material with multiple protective functions for fruit preservation.