Here, we present an optimization of colorimetric determination of hydrogen peroxide content in plants using potassium iodide. Our method is based on a one step buffer (extraction and reaction) for the determination of H 2 O 2 in different plant tissues and overcomes interference of soluble antioxidant and color background. A particular attention is paid to buffer pH shown to be tissue dependent. With this inexpensive microplate method, it is possible to analyze 12 experimental samples in about 45 min all in triplicates, with blanks, controls and standard curve.

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Postharvest degradation of minimally processed mangoes limits the marketability of fruit. The effect of heat treatments applied to whole 'Keitt' mango fruit on physical, physiological and biochemical quality of minimally processed mangoes was studied. Whole mangoes were subjected to hot water dipping (HWD) at 46 or 50 • C for 30 or 75 min, cooled for 15 min, minimally processed and stored at 6 • C for 9 d. Sensory analysis, firmness, color, acidity, pH, total soluble solids (TSS), ascorbic acid, total carotenoids, malondialdehyde (MDA) and respiration rate (RR) were investigated. A global beneficial effect of HWD 50 • C/30 min was observed. This treatment was the only one to maintain the acceptability of fresh-cut mangoes for 6 d, the yellow color, expressed by b* value, for 9 d and the firmness for 3 d compared to the control. Moreover, HWD 50 • C/30 min increased the total carotenoids content after 3 d compared to the control. Although the ascorbic acid content decreased during storage, HWD 50 • C/30 min is the less degrading condition of the heat treatments. Lipid peroxidation, estimated by MDA content, was less important for HWD 50 • C/30 min. Finally, the RR of whole mangoes treated by HWD 50 • C/30 min was lower than in the other treatments and could be used as an indicator of product shelf-life. This study selected the HWD 50 • C/30 min as the optimal heat treatment to improve the quality of fresh-cut 'Keitt' mangoes.

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