Novel imine dynamic response films with grafting phenylalanine onto oxidized starch/pectin matrixes and regulated physiological metabolism of cherry tomatoes

Dynamic response films with efficient, accurate and biodegradable properties greatly contribute to food packaging materials. In this study, phenylalanine was innovatively reversibly grafted onto oxidized starch via imine bonding and blended with Ca²⁺ and pectin to prepare novel imine dynamic responsive composite films (PO-PE/Ca). The results indicated that the cross-linking and dense structure formed by electrostatic interaction in PO-PE/Ca, and showed excellent thermal stability. The composite films displayed excellent mechanical property (elasticity modulus over 2100 MPa), and the water vapor permeability was 26.4 % lower than that of individual starch films. Additionally, the introduction of benzene rings and imine bonds significantly improved the ultraviolet shielding properties and transparency of the films. The internal imine bonds of PO-PE/Ca could be stimulated by acidic gases of fruit respiration, and constantly released phenylalanine to regulate fruit metabolism. The films effectively maintained fruit quality and significantly promoted phenol content (9.5 mg/100g) of fruits, showing resistance to Botrytis cinerea of cherry tomatoes during 10 d storage. This study provided a novel strategy for the development of dynamic controlled release packaging materials in food preservation.