Hydrogen sulfide delays softening of banana fruit by inhibiting cell wall polysaccharides disassembly

Summary Harvested banana undergoes rapid softening, which limits its shelf life. To delay softening, banana fruit was treated with hydrogen sulfide (H 2 S) emitted by 0.6 m m sodium hydrosulfide (NaHS) and stored at 15 °C for 16 days. The effects of H 2 S on cell wall degradation and other physiological characteristics were investigated. In comparison to control fruits, H 2 S‐treated bananas retained a higher level of fruit firmness, but lower hue values. Ethylene metabolism analysis suggested that H 2 S inhibited the production of ethylene and the accumulation of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) and decreased the activities of ACC synthase (ACS) and ACC oxidase (ACO). Cell wall polysaccharides determination assays suggested that H 2 S treatment increased the proportion of HCl‐soluble pectin (HSP), NaOH‐soluble pectin (NSP), cellulose and hemicellulose but decreased water‐soluble pectin (WSP) in fruits. H 2 S treatment also inhibited the activities of polysaccharide degrading enzymes such as polygalacturonase (PG), pectin methylesterase (PME), pectin lyase (PL), cellulase (CL) and β ‐galactosidase ( β ‐Gal). Transmission electron microscopy analysis suggested that H 2 S protected cell walls from structural breakdown. These results indicated that H 2 S is effective in delaying banana softening by regulating cell wall polysaccharide metabolism.