Kinetics of temperature effect on antioxidant activity, phenolic compounds and color of Iranian jujube honey.

In the present study, the Iranian jujube honey was evaluated for its total antioxidant activity by DPPH assay, total phenolic content (TPC) by using the Folin-Ciocalteu reagent, and brown pigment formation (BPF). The kinetics of changes in jujube honey samples heated at various temperatures (45, 55 and 65 °C) over 10 days were studied. Increasing treatment temperature and time caused an increase in all three parameters including, antioxidant activity, BPF and TPC. Increases in BPF and TPC followed zero-order kinetics, and the rise in antioxidant activity varied depending on heating temperatures, following second-order, first-order and zero-order kinetics when samples were heated at 45, 55 and 65 °C, respectively. At 45-65 °C, activation energy values of 68 and 64.7 kJ/mol^-1 were obtained for BPF and TPC, respectively. Linear relationships were observed between antioxidant activity and BPF, TPC and antioxidant activity, and BPF and TPC, such that the highest phenol content was related to the darkest honey sample. For all three parameters, heating honey to 65 °C was found to be more effective than heating to 45 or 55 °C.