Effect of different drying methods on antioxidant characteristics of bee-pollen

Abstract

In this study, microwave drying (MWD) and microwave-assisted vacuum drying (MW-VD) (500, 675 mbar) at power levels of 300, 450, 600 and 900 W, hot-air drying (HAD) and vacuum drying (VD) (300, 500 mbar) at temperatures of 35, 50, 65 °C and freeze drying (FD) of bee-pollen were investigated in relation to its total phenolic content (TPC), antioxidant vitamin composition (C and E) and antioxidant capacity. HAD at 35 °C provided similar vitamin C content as compared to fresh pollen while all other treatments led to significant loss ranging between 14.3 and 61.3%. Retention of vitamin E level in dried pollen ranged between 71 and 87%. Except vitamin C, MWD at lower power levels provided better or similar values of above mentioned properties as compared to HAD and FD treatments. The data indicated that pollen dried by MW-VD had higher antioxidant activity compared to samples dried by HAD irrespective of the applied pressure or power level.