Preservative paper containing phenolic acid grafted on chitosan for post-harvest peach preservation

Honey peach (Prunus persica) is easy to rot after picking because of its special property, and the damage of traditional preservation method to the ecological environment is unacceptable. Therefore, chitosan as a kind of environmental protection material with excellent performance has attracted people's attention. Though chitosan has good practicability, its application in practical production is limited due to its poor water solubility. In this study, we prepared phenolic acid-g-chitosan using two synthesis methods of carbodiimide-mediated coupling reaction and free radical-mediated grafting procedure. After comparing the grafting rates of these conjugates, the results showed that using the synthetic method of carbodiimide-mediated coupling reaction through NHS and EDC as the coupling agent to graft phenolic acid onto chitosan had a good grafting ratio at a molar ratio of 1.5:1. Therefore, six phenolic acids were used for the first time to prepare conjugates through this method, and these conjugates were characterized by UV and NMR. It can significantly improve the water solubility and DPPH scavenging activity of chitosan, thus releasing its good properties and meeting the application of post-harvest preservation of honey peaches. The results indicate the antisepsis and fresh-keeping effects of six conjugates showed that preservative paper containing 2-Hydroxyphenylacetic acid-g-CS has the best effect of inhibited decay index and weight loss when peach fruits were stored at 20 ± 5 °C under 40%–60% humidity for 8 days. Thus, the water-soluble conjugate prepared by grafting phenolic acid onto chitosan can enhance the market application range of chitosan.