Effects of hot-air drying temperature on drying characteristics and color deterioration of rape bee pollen

The effects of different hot-air drying (HAD) temperature (40, 50, 60, and 70 °C) on the drying characteristics, color changes, the contents of α-dicarbonyl compounds (α-DCs), 5-hydroxymethyl furfural (5-HMF) and carotenoids of rape bee pollen were investigated in the study. The results showed that increasing the drying temperature from 40 to 70 °C shortened the drying time by 65 %. HAD caused lower L* and b* values, as well as higher a* values. Browning index and 5-HMF content increased with increasing drying temperature. The relative content of antheraxanthin increased 230 % at 70 °C while lutein and zeaxanthin decreased by 74 and 81 % than that of fresh (non-heated) pollen. The contents of 3-deoxyglucosone, 1-deoxy-2,3-pentosulose, antheraxanthin, and lutein were related to the color deterioration in HAD process in rape bee pollen. This work is of great practical significance to provide scientific basis for quality optimization of bee pollen in the drying process.