Glucose oxidase activity and hydrogen peroxide accumulation in Croatian honeys

Sa？etak Ability of black locust (n = 7), chestnut (n = 3), lime (n = 5), mint (n = 3), and honeydew (n = 12) honeys to produce hydrogen peroxide upon dilution, as well as their glucose oxidase activity were investigated in the present study. The glucose oxidase (GOX) activity was determined by the standard horseradish peroxidase/o-dianisidin method, while hydrogen peroxide concentration in honey solutions of five different mass to volume ratios (1:1; 1:2; 1:4; 1:8; 1:16) by semi-quantitative method using MQuant？ peroxide test strips. The obtained results showed that chestnut, lime, honeydew and mint honeys exhibited high GOX activity (341.26 ± 128.78, 350.16 ± 124.91, 376.82 ± 69.02, 402.47 ± 60.99 μg H2O2/h g), while black locust honeys much lower GOX activity of 25.58 ± 21.87 μg H2O2/h g. The accumulation of hydrogen peroxide in serially diluted honeys has shown asymmetrical inverted U-shaped curve, where the increase in hydrogen peroxide accumulation with dilution reached a maximum point, after which its concentration rapidly declined. Hydrogen peroxide content in honey solutions of different mass to volume ratio varied from 0 to 294.1 μmol/L h. Lime and chestnut honeys generated the highest hydrogen peroxide content (264.71 ± 65.77, 245.10 ± 84.90 μmol/L h) on average, while black locust, mint and honeydew honeys at least two-fold lower amounts (113.40 ± 50.84, 127.45 ± 33.96, 112.75 ± 98.42 μmol/L h). Lack of correlation between glucose oxidase activity and hydrogen peroxide content indicates that the glucose oxidase activity does not present a reliable parameter for the prediction of hydrogen peroxide content produced in honey solutions