Changes In Visual Fruit Quality and Antioxidant Content at Harvest and Following Cold Storage of Pepper Fruits Harvested From Plants Fed with Nutrient Solutions Containing Hydrogen Peroxide

In a previous study we reported the effect of different hydrogen peroxide (H2O2) concentrations (100mM to 500mM) on root growth, shoot height and leaf antioxidant activity in pepper seedlings (HortScience 43 (4): Abstr276). The study showed that in 100mM treatment, shoot height was unaffected and the leaf catalase(CAT), peroxidase(POD) and superoxide dismutase(SOD) activities were higher or similar to control indicating that it may be possible to enhance the antioxidant content and hence the nutrient quality of pepper with H2O2 treatment without damaging the crop.  In the present investigation we fed 15mM H2O2 to two varieties (Red-4Ever-Enza Zaden and Yellow-Bsalga-RZ) of mature fruit bearing pepper plants grown hydroponically in bags filled with sawdust. One week following H2O2 treatment fruits were harvested and transferred to cold storage kept at 10 ⁰C. Fruits were examined for visual fruit quality and the antioxidant content in pericarp tissue at harvest and during cold storage. Visual fruit quality was rated from 0 to 5 (0=no decay, 1=signs of decay, fungal spores on fruit stalk, 2=fungal spores on fruit surface, 3=first lesion on pericarp with widespread spore damage (unmarketable), 4= multiple lesions, 5= rot and watery). The antioxidant enzyme activity was determined using 15mm diameter pericap tissue harvested and frozen immediately in liquid nitrogen. The isoenzymes profiles of POD and SOD were also separated by non-denaturing polyacrylamide gel-electrophoresis. Average visual fruit quality was better in fruits from H2O2 treated plants up to 21days of storage at 10 ⁰C compared to control. The two cultivars differed in antioxidant enzyme activity with respect to H2O2 treatments. For example, catalase(CAT) activity in the fruit pericarp tissue from H2O2 treated plants in yellow variety was significantly higher than that of red variety. CAT activities were reduced significantly in both varieties at one week of storage at 10 ⁰C.  POD activity in red fruit pericarp was slightly higher than that of yellow fruit. Similar to catalase, SOD was higher in yellow fruit pericarp tissue than in red fruit pericarp tissue. The SOD activities in both red and yellow fruit pericarps were reduced by H2O2 treatment.