干燥处理对蜂花粉脂质氧化劣变的干预机制与调控

Pollen is very susceptible to oxidation due to highly amounts of polyunsaturated fatty acids, thus negatively affect its nutritional properties and commercial value. Our previous research found that drying is the key process resulting in lipid oxidation, different drying methods and conditions greatly affect the storage stability of pollen. However, the mechanism of intervention of lipid oxidation in the drying process is not yet clear. Therefore, the current work aims to reveal the mechanism and optimization strategy of lipid oxidation degradation of pollen during drying. Firstly, changes in fatty acid composition and content of samples dried by different methods (hot air, infrared, pulsed vacuum drying, freezing,and etc.) and temperatures were carried out, analyze the formation and accumulation of primary and secondary oxidation products, and elucidate the major degradation pathways of lipid oxidation; Secondly, explore the intrinsic relationships between the lipid oxidation and changes in moisture migration, microstructure, and antioxidant constituents and lipid oxidation, then, reveal the mechanisms of lipid oxidation of pollen during drying by multiple perspectives. Finally, conclude the key factors related to lipid oxidation, and develop the optimization strategy of lipid oxidation degradation of bee pollen during drying processing, which is proposed to provide theory and technology support for reducing pollen lipid oxidation.

蜂花粉因富含脂肪酸，特别是多不饱和脂肪酸，极易发生脂质氧化，严重影响其营养特性和商品价值。申请人前期研究发现干燥是蜂花粉加工过程中导致脂质氧化的关键环节，不同干燥处理对花粉的贮藏稳定性影响显著。然而干燥对脂质氧化的干预机制尚不明确。基于此，项目以揭示干燥处理对蜂花粉脂质氧化劣变的干预机制与调控为研究目标，首先采用HS-GC-MS、HPLC等技术分析不同干燥方式与温度条件下蜂花粉中脂肪酸组成与含量的变化，脂质初级、次级氧化产物的形成与积累，阐明脂质氧化的主要降解途径；其次借助Cryo-SEM、TEM和LF-NMR等技术分析不同干燥过程中微观结构、水分迁移和抗氧化成分的动态变化与脂质氧化的内在关系，最后通过高分辨质谱和计量学等分析手段，多层次多角度揭示蜂花粉脂质氧化的主要途径和机理；进而找出脂质氧化减损调控的关键点，提出降低脂质酸败的靶向控制方法，为蜂花粉脂质氧化减损控制提供理论与技术支撑。

蜂花粉含有种类丰富的脂肪酸，特别是多不饱和脂肪酸，导致目前市售蜂花粉普遍存在不同程度的脂质氧化酸败，严重影响了蜂花粉的营养特性和商品价值。本研究主要以油菜花粉和荷花花粉为研究对象，探究了不同干燥方式（热风、红外、真空脉动、冷冻干燥等）对蜂花粉干燥动力学、脂质氧化、脂质谱和脂质代谢途径的影响。利用非靶向脂质组学方法解析了蜂花粉中的脂类成分，确证了来自20个亚类1541种脂代谢产物，通过关联网络和代谢途径分析，明确了干燥过程中的脂质氧化与甘油磷脂、亚油酸和甘油脂代谢途径相关，探明了磷脂酰乙醇胺、磷脂酰胆碱、磷脂酰丝氨酸、磷脂酸和溶血磷脂酰胆碱是影响氧化进程的关键脂质，揭示了干燥诱导蜂花粉脂质氧化的分子机制；解析了自然晾晒、热风、中短波红外、真空冷冻和真空脉动等5种干燥方式对油菜蜂花粉的干燥特性、色泽、酚酸含量以及α-二羰基化合物的影响规律，确证了真空脉动干燥过程中的低氧环境可有效抑制脂质氧化反应，防止色泽劣变，减少生物活性成分的降解，当干燥温度超过55℃时，干燥蜂花粉的形状和表面结构发生显著变化，5-羟甲基糠醛含量快速增加。采用HS-GC-IMS和HS-SPME-GC-MS联用技术对荷花粉中的挥发性成分进行了系统分析，鉴定了147种挥发性成分，找到了蜂花粉在干燥过程中形成的特征性风味化合物及其生成路径。本项目的研究结果揭示了蜂花粉脂质氧化的主要途径和机理，提出了降低脂质酸败的优化控制方法，为蜂花粉脂质氧化减损控制提供理论与技术支撑。