Effects of pulsed vacuum drying temperature on drying kinetics, physicochemical properties and microstructure of bee pollen

In order to clearly analyze the effects of different drying temperatures on the nutritional components, toxic substances and other physicochemical properties of bee pollen, this work comprehensively investigated the effect of pulsed vacuum drying (PVD) temperature on the drying kinetics, amino acids, toxic products of Maillard reaction (α-Dicarbonyl compounds, α-DCs and hydroxymethylfurfural, HMF), antioxidant capacity, lipid oxidation, and microstructure of bee pollen. The results showed that when the drying temperature increased (35–75 °C), the drying time was shortened by 233 min, accompanied by the increase of antioxidant and lipid oxidation. When the temperature exceeded 55 °C, HMF and α-DCs accumulated in large quantities, and the amino acid content decreased significantly, among which the content of seven essential amino acids decreased by more than 32.2%. The changes in the microstructure support the accelerated water migration rate and the dramatic Maillard reaction at high temperature. This study explored the law of bee pollen quality changes under PVD drying technology, preliminarily analyzed the transformation and synthesis pathways of HMF and α-DCs, proposed 3,4-DGE could be used as a representative indicator to judge the safety of bee pollen, and recommended that the drying temperature of pollen should not exceed 55 °C.