Development and characterization of yeast-incorporated coating films for improving the postharvest shelf-life of snap beans

Abstract

Snap bean is an important crop species of Leguminosae family, which needs to be stored prior to marketing as it is usually consumed fresh. However, snap bean pods are prone to disease infection during storage, and quickly lose market quality if they store for a long period. One way to tackle this issue is to cover pods with yeast-incorporating coating films. In this research, we assessed incorporation of three strains of yeast Ca63 (Cryptococcus albidus), Ca64 (Cryptococcus albidus) and Yett1006 (Candida parapsilosis) and their intracellular products with naturally-based fruit coating materials. All three strains and their intercellular products could effectively inhibit the growth of Fusarium fujikuroi, the phytopathogenic agent causes pod rot in snap beans, however, the inhibitory impacts of yeast strains were more pronounced than their intercellular products. The snap bean pods treated with either yeast-incorporated films or yeast intracellular products-incorporated films could reduce weight loss rate, decay rate, rust index and color index in pods, leading to longer shelf-life during 15 days of storage at 28 ℃ and relative humidity of 65% ± 5%. In addition, the coating material containing yeasts or their intracellular products positively affected the activity of superoxide dismutase, increased the content of vitamin E, reduced the rate of chlorophyll degradation and effectively inhibited the increase of malondialdehyde content in the treated pods. A metabolomic analysis of the yeasts and their intracellular products revealed that their protective impacts could be due to antioxidant compounds found in their metabolites. Overall, the results of this research provided a basis for the application of the three strains of yeast in postharvest preservation of snap bean pods and laid a foundation for exploring the mechanism underlying postharvest preservation of snap bean pods.