Evaluation of peroxidase assay and effect of thermal blanching on sapota and fig fruits

A spectrophotometric assay was developed for the quantification of peroxidase activity in the presence of para-phenylenediamine dihydrochloride (PPDD) and 8-hydroxyquinolene (8-HQ) as chromogenic co-substrates in KH2PO4/NaOH buffer solution at pH 7.8. The resulting violet coloured product had maximum absorbance at 540 nm. Under optimized condition, the linearity range of hydrogen peroxide (H2O2) was 1-124 µM and that of peroxidase was 0.2958-14 nM and 0.0739-2.3674 nM by kinetic and fixed time assays, respectively. The Michaelis-Menten (Km) constant, catalytic efficiency and catalytic power were 38.72 µM, 0.2613 × 106 M−1 min−1 and 2.4748 × 10−3 min−1, respectively. The obtained broad and sensitive linearity range of H2O2 and peroxidase assays and lower value of Michaelis-Menten constant indicate the superiority of this method. The developed method was successfully applied to study the effect of blanching treatment of peroxidase in sapota and fig fruit extracts and this is helpful in fixing blanching temperature and blanching time for fruits.

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