Preparation of chitosan gallic acid derivatives and its effect on preservation of fresh-cut apple

According to the spoilage characteristics of the fresh-cut fruits and vegetables as well as structural features of chitosan (CTS) and gallic acid (GA), a kind of water-soluble CTS-GA was prepared by conjugating GA onto CTS and the effect of CTS-GA on preservation quality of fresh-cut apples was studied. The preliminary characterization of derivatives was studied through a series of testing methods, such as UV spectrum, FTIR spectrum, X-ray diffraction and HPLC, which shown that CTS-GA was formed by connecting amine groups from GA and hydroxyl groups from CTS. Some biochemical changes of fresh-cut apples coated with CTS, GA and CTS-GA were investigated. The results showed that after 4 d storage, polyphenols content of CTS-GA group was 1.29±0.067 mg/g, which was significant higher than that of the blank group. Vc content of CTS-GA group was (1.36±0.03)×10-2 mg/g, higher than those of blank, CTS group and GA group, while PPO activity by CTS-GA treatment was 141.78±4.31 U/g md, lower than the blank and CTS treatments. And the amount of microorganism in CTS-GA group was 5.406±0.012 (1 g CFU/g), obviously lower than the blank, CTS group and GA group.