Hydrogen peroxide pre-treatment enhances antioxidant properties and free radical scavenging activities of tree bean (Parkia roxburghii G. Don) seeds and pods during storage

Purpose This study aims to examine the effects of various physical and chemical pre-treatments on antioxidant properties of tree bean (Parkia roxburghii G. Don) in combination with storage conditions. Design/methodology/approach The whole pods and seeds of tree bean were treated with gamma rays (γ-rays), sodium hypochlorite (NaOCl), chlorine dioxide (ClO2) and hydrogen peroxide (H2O2) and stored at room temperature (RT, 25°C) for 30 days. The physical and chemical pre-treated seeds and pods were compared with the same stored at RT and refrigerated storage at 4°C and −20°C. During storage, physical (moisture content) and antioxidants like total phenolics, ascorbate content, reduced glutathione, total flavonoids, along with free radical scavenging activities (FRSA) were measured. Findings Chemical pre-treatments with NaOCl, ClO2 and H2O2 significantly accelerated (p = 0.05) the total phenolics (1.9 mg/g FW in seeds and 2.4 mg/g FW in pods), flavonoids content (0.3 mg/g FW each in seeds and pods) and ABTS activities (73.3 per cent in seeds and 92.3 per cent in pods) at 30 days of storage. A significant decrease (p = 0.05) in ascorbate content (6.1 mg/g FW in seeds and 3.5 mg/g FW in pods), reduced glutathione (5.1 mg/g FW in seeds and 3.7 mg/g FW in pods), FRAP (0.3 mg equi Fe/g FW in seeds and 0.4 mg equi Fe/g FW in pods) and reducing power (1.8 mg/g FW in seeds and 3.7 mg/g FW in pods) was observed under all the treatments at 30 days of storage. However, DPPH increased under γ-irradiation and decreased under chemical pre-treatments, storage at RT and refrigerated storage. The overall result showed that pre-treatment of H2O2 at 10-20 mM maintains antioxidants and radical scavenging activities in tree bean during storage. Originality/value The application of H2O2 at 10-20 mM prior to storage of tree bean maintains the physical, antioxidant properties and FRSA in tree bean seeds and pods as compared to natural ambient conditions. Hence, this technique will help in improving the keeping quality of this legume and avoid spoilage after harvest for an extended period.