The effect of superheated steam (SHS) treatment on the quality characteristics of rape bee pollen were studied, and the efficiency of inactivation and inhibition of lipid oxidation were analyzed to investigate the differences between SHS and ⁶⁰Co radiation treatment. The number of total plate count (TPC) and mold colonies (MC) remained within the limits of the standards after SHS treatment at 140 ℃ for 2 min. Neither TPC nor MC were detected after ⁶⁰Co irradiation. Peroxidase (POD) and polyphenol oxidase (PPO) activities significantly decreased with increasing temperature and duration of SHS, while ⁶⁰Co radiation completely inactivated PPO. Compared to ⁶⁰Co radiation, SHS treatment inhibited the deterioration of rape bee pollen by avoiding hydroperoxide production and lipid oxidation due to lack of oxygen. These results suggested SHS under 140 ℃ for 2 min was the most suitable to inactivate the microorganisms and enzymes in rape bee pollen with minimal lipid oxidation.

This study was aimed to analyze the effect of procyanidin B₂ (PC) and tannin acid (TA) on the activities of cholesterol esterase (CEase) and the inhibitory mechanisms of enzymatic activity. The interaction mechanisms were investigated by enzymatic kinetics, multi-spectroscopy methods, thermodynamics analysis, molecular docking, and dynamic simulations. PC and TA could bind with CEase and inhibit the activity of enzyme in a mixed-competitive manner and non-competitive manner, which was verif ied by molecular docking simulations and dynamics simulations. Also, PC and TA showed the synergistic inhibition with orlistat. Fluorescence, UVvis and the thermodynamic analysis revealed that the complexes were formed from CEase and inhibitors by noncovalent interaction. As revealed by the circular dichroism results, both PC and TA decreased enzymatic activities by altering the conformations of CEase. The inhibition of PC and TA on CEase might be one mechanism for its cholesterol-lowering effect.

The significant demand for high quality food has motivated us to adopt appropriate processing methods to improve the food nutritional quality and flavors. In this study, the effects of five drying methods, namely, pulsed vacuum drying (PVD), freeze drying (FD), infrared drying (IRD), hot-air drying (HAD) and sun drying (SD) on free amino acids (FAAs), α-dicarbonyl compounds (α-DCs) and volatile compounds (VOCs) in rape bee pollen (RBP) were determined. The results showed that FD significantly released the essential amino acids (EAAs) compared with fresh samples while SD caused the highest loss. Glucosone was the dominant α-DCs in RBP and the highest loss was observed after PVD. Aldehydes were the dominant volatiles of RBP and SD samples contained more new volatile substances (especially aldehydes) than the other four drying methods. Comprehensively, FD and PVD would be potential methods to effectively reduce the quality deterioration of RBP in the drying process.