**2. Methods and Materials**

### *2.1. Materials*

Cowpeas were obtained from a local agricultural product wholesale market in Haizhou, Lianyungang, China. Cowpeas with the same length, thickness and maturity and without mechanical damage, pests or diseases were selected, rinsed and drained naturally for use. Pullulan with a molecular weight of 3.1 × 105 Da was obtained from Pharmacopoeia, Japan. E-polylysine was obtained from Zhejiang Tongfa Biotechnology Co., Ltd., Ningbo, China. Glutathione was obtained from Zhejiang Shenyou Biotechnology Co., Ltd., Huzhou, China. All the other chemicals were of reagent grade.
