实验有用

2.1. Film preparation

Chitosan solutions (2%, w/v) were prepared by dispersin 10 g of chitosan (deacetylated degree of 90%; Vanson, Redmond, WA) in 500 ml of lactic acid solution (1%, v/v). After the chitosan was dissolved completely, the solutions were filtered with cheesecloth by vacuum aspiration. Starch solutions with concentrations of 1, 2, 3 and 4% (w/v) were prepared by dispersing 25% amylose cornstarch or waxy starch (American Maize Products Co., Hammond, IN) in distilled water and heating the mixtures on hotplates with stirring until it gelatinized, and then cooling to 25 ◦C. A series of chitosan/starch composite films were prepared by mixing 100 ml of 2% chitosan solution with 100 ml of 1, 2, 3, 4% starch solutions. Glycerin was added as 25% (w/w) of the total solid weight in solution. The blend compositions are given in Table 1. The mixtures were cast onto flat, level Teflon-coated glass plates. After drying the films at room temperature for at least 72 h, they were peeled from the plates. Dried films were conditioned at 50% RH and 25 ◦C for 48 h prior to testing.