Grape Preservation Using Chitosan Combined with β-Cyclodextrin

The effect of 1% chitosan combined with 2% β-cyclodextrin to the preservation of fresh grapes under ambient temperature was investigated. The results indicated that the hydrogen bond formed between the hydroxyl group of β-cyclodextrin and the amidogen or hydroxyl group of chitosan and the crystal form of chitosan was also changed when cyclodextrin was doped into chitosan coating. The compound coating could prolong the shelf life of grapes, maintain lower respiration rate and higher activities of superoxide dismutase, peroxidase, and catalase during storage time, and restrain weight loss and malonaldehyde content increase. Coating grapes with chitosan + β-cyclodextrin was a good method in postharvested grape preservation. 1. Introduction Chitosan is formed by 2-amidogen-2-deoxidize-β-D-glucose. It is a safe, biocompatible, and biodegradable natural alkaline polysaccharide, and can easily form a film on fruit and vegetable surfaces. Chitosan is popular in many fields, such as medicine, environment, chemical industry, and food [1]. β-Cyclodextrin is one of supramolecular compounds and has many particular properties such as emulsion, moisturizing, and inclusion. It is combined by α-1, 4-glucosidic bond with α-D-glucose, and is oligosaccharide of closed loop structure, and the degree of polymerization is 7 unite of glucose. Cyclodextrin demonstrates a high symmetrical characteristic and its spatial structure is cylindrical. Both the cavity depth and internal diameter are 0.7-0.8？nm. The atoms of the glycosidic oxygen are in the same plane. The primary hydroxyl group of residue C6 is located outboard of the ring, and the hydrophobic group of C–H bond is placed inside the cylinder [2]. Grape is one of main fruits in the world. Fresh grape usually possesses good commodity properties and long storage time. However, fresh grape loses water and rots during storage time. Thus, its commercial value decreased [3]. In this paper, the compound coating of chitosan combined with β-cyclodextrin was prepared and applied in fresh grape preservation. There is no report about the edible coating of chitosan combined with β-cyclodextrin at present, and we hope to explore a new method for fresh grape preservation. 2. Materials and Methods 2.1. Materials Grapes (Vitis labrusca L. kyoho) were purchased from an orchard in the vicinity of Shanxi Normal University on August 10, 2011. Grapes with uniform shape, size, color, physiologically mature stage, and no defects were selected and quickly transported in cartons with holes to the laboratory after picked at noon. Water-soluble