**1. Introduction**

Cowpea (*Vigna unguiculata* L.), an annual entwining herbaceous plant under the subfamily *Papilionidae*, is a common vegetable variety in China. This species is rich in vitamins, plant protein and mineral elements and has a high economic value [1]. Cowpeas are a highly seasonal vegetable that is usually harvested in summer in high temperatures and humidity. After harvest, this vegetable is very intolerant to storage because of its crisp tissue, high water content and strong respiration [2]. Generally, the storage period of cowpeas at room temperature is 3 days. In a short period, dehydration, wilting, fading, rust spots and even rotting occur, causing major economic losses [3,4]. Therefore, the postharvest preservation of cowpea is a major problem for the healthy development of the cowpea industry, requiring the study of postharvest preservation technologies of cowpea.

Edible coating preservation technology can control moisture and solute migration, internal gas exchange, respiration, and oxidative reaction rates and improve the appearance and surface characteristics of fruits and vegetables [5,6]. Moreover, edible coatings serve as the carriers of food additives, such as preservatives, antioxidants, colorants and flavors [7]. Pullulan is a homogeneous polysaccharide with a fine coating-forming ability [8] and E-polylysine is a broad-spectrum preservative used in the food industry [9]. Glutathione is an antioxidant that can suppress polyphenol oxidase (PPO) activity and browning [10,11].

**Citation:** Hu, A.; Mao, Y. Effects of Pullulan-Based Coatings Incorporating E-Polylysine and Glutathione on the Preservation of Cowpeas (*Vigna unguiculata* L.) Postharvest. *Coatings* **2023**, *13*, 125. https://doi.org/10.3390/ coatings13010125

Academic Editor: Elena Torrieri

Received: 26 November 2022 Revised: 4 January 2023 Accepted: 5 January 2023 Published: 10 January 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Given their coating-forming ability and antibacterial and antioxidant activities, pullulanbased coatings incorporating E-polylysine and glutathione may have antibacterial and antioxidant activities that can thus extend the shelf life of cowpea. Hence, further investigations into pullulan-based coatings incorporating E-polylysine and glutathione are needed. Therefore, this study aims to investigate the preservative effects of pullulan-based coatings incorporating E-polylysine and glutathione on cowpeas during refrigerated storage.
