Effect of chitosan-based edible coating on antioxidants, antioxidant enzyme system, and postharvest fruit quality of strawberries (Fragaria x aranassa Duch.)

The severity of decay in strawberries stored at either 5 °C or 10 °C was significantly reduced and the shelf-life was extended by immersing fruits in chitosan solutions of 0.5, 1.0 and 1.5 g/100 mL for 5 min at 20 °C as compared to the control. Strawberries treated with chitosan also maintained better fruit quality with higher levels of phenolics, anthocyanins, flavonoids (ellagic acid, ellagic acid glucoside, p-coumaroyl glucose, quercetin 3-glucoside, quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-glucuronide, cyanidin 3-glucoside, pelargonidin 3-glucoside, cyanidin 3-glucoside-succinate, and pelargonidin 3-glucoside-succinate), antioxidant enzyme activity [catalase (CAT), glutathione-peroxidase (GSH-POD), guaiacol peroxidase (G-POD), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDAR)], and oxygen radical absorbance capacity for peroxyl radicals (ROO), hydroxyl radical radicals (OH; HOSC) and 2,2-Di (4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) than the untreated fruits. Chitosan treatments retarded the decrease of ascorbic acid (ASA) and reduced glutathione (GSH) content and β-1,3-glucanase activities compared to control. The high contents of antioxidants, antioxidant activity, ASA and GSH and high activity of β-1,3-glucanase in the treated strawberries reinforced the microbial defense mechanism of the fruit and accentuated the resistance against fungal invasion. Therefore, the application of chitosan coating could be favorable in extending shelf-life, maintaining quality and controlling decay of strawberries.

► Decay in strawberries during storage was significantly reduced by chitosan.
► Strawberries treated with chitosan maintained high levels of phenolics and antioxidants.
► Chitosan coating also increased antioxidant enzyme and β-1,3-glucanase activities.