Multifunctional cinnamaldehyde-tannic acid nano-emulsion/chitosan composite film for mushroom preservation

Mushrooms are prone to browning, weight loss, softening, lipid oxidation, and microbial growth after harvesting. Therefore, it is particularly necessary to develop a packaging material with UV protection, antibacterial, and antioxidant properties. Herein, we used tannic acid (TA), a green edible natural extract with excellent antioxidant and anti-ultraviolet effects, as an emulsifier to prepare the cinnamaldehyde-tannic acid nano-emulsion (CIN-TA-NEs). The CIN-TA NEs/CS (CSCT) film was successfully prepared by incorporating CIN-TA NEs into chitosan (CS), which effectively improved the utilization rate of CIN and endowed the composite film with multiple functional effects. Due to the introduction of TA, the radius of CIN emulsion was reduced from 356.2 ± 35.89 nm to 147.4 ± 5.61 nm, which enhanced the uniform dispersion of oil phase CIN in aqueous phase CS, improved the compactness of the film, reduced water vapor and oxygen permeability, and increased water resistance of the composite film. The incorporation of CIN-TA NEs endowed CS composite films with 100% UV protection ability, over 99% antibacterial effect, and 90.56% and 94.02% clearance rates for DPPH and ABTS free radicals. In addition, the CSCT composite film had high biosafety, and TA promoted the biodegradation of composite film to a certain extent. The preservation experiment of Agaricus bisporus has proven that CSCT composite film effectively prolongs the preservation time of mushrooms, which is more than 4 days longer than PE film. This work has prepared a composite film with multiple functions, which has great application prospects for extending the shelf life of mushrooms.