Ultrasonic nebulization-assisted layer-by-layer assembly based on carboxymethyl chitosan: An emerging alternative for promoting phenylpropanoid metabolism

To enrich the properties of chitosan (CS) and improve its applicability, we prepared carboxymethyl-chitosan (CMCS) by carboxymethylation and developed a layer-by-layer assembly (LBL) by the ultrasonic nebulization-assisted technique. The degree of carboxymethylation was 42.20% and the structure of CMCS was characterized using Fourier transform infrared, nuclear magnetic resonance spectroscopy. The ultrasonic nebulization-assisted LBL (UNLBL) edible coating was developed based on an inner negatively CMCS charged layer and an external positively charged CS layer. As compared to conventional LBL (CLBL) assembly, the greater thickness, stronger mechanical properties and lower water vapor permeability were detected in UNLBL assembly. Through an untargeted metabolomic analysis and real-time quantitative PCR, it was evident that ultrasonic nebulization-assisted LBL assembly is a promising alternative for promoting phenylpropanoid metabolism in strawberries.