高压脉冲电场技术降解茶饮料中啶虫脒和吡虫啉机理研究

Tea is one of the most popular beverages throughout the world and valued for its specific aroma and flavor as well as health-promoting properties. However, the application of pesticides with little restriction or control during tea planting has resulted in the occurrence of residues in tea. Acetamiprid and imidacloprid are the most frequently monitored pesticides residues in tea and they easily transfers into tea beverage due to their high solubility in water. Several studies have demonstrated that acetamiprid and imidacloprid are cytotoxic, genotoxic and neurotoxic. Therefore, the dissipation of pesticides residues in tea beverage is critically demanded. Pulsed electric fields (PEF) are potential complements or replacements to thermal pasteurization and have undergone substantial developments near commercial application. Our previous study has demonstrated that PEF was effective in dissipation several pesticides. However, the mechanism of pesticides degradation under PEF treatment is not clear. Therefore, this study will attempt to investigate the degradation kinetics and mechanism of acetamiprid and imidacloprid in tea beverage under PEF treatment. For the degradation intermediates screening and identification, gas chromatogram/mass spectrometry (GC/MS) and liquid chromatogram/mass spectrometry will be used. The identification of small molecule products will be performed by ion chromatography. Preparative chromatography will be used to separate and enrich the degradation products which could not be identified by GC/MS. Then, high-resolution mass spectrometry, nuclear magnetic resonance spectroscopy and near infrared spectroscopy will be used for further identification. Based on the degradation kinetics and the changes of concentration of degradation products during PEF treatment, the degradation mechanism of acetamiprid and imidacloprid under PEF treatment will be proposed. This study will facilitate the application of PEF on the elimination of pesticides in tea beverage and other foods.

茶饮料是当今世界三大无酒精饮料之一。但因茶叶种植中农药安全使用水平和监管力度有限，致使茶饮料中啶虫脒和吡虫啉等水溶性农药残留问题突出。研究证实，啶虫脒和吡虫啉具有细胞毒性、遗传毒性和神经毒性。因此，降解茶饮料中的农药残留迫在眉睫。高压脉冲电场（PEF）技术是一种新兴的非热加工技术，申请人前期研究已发现，PEF技术能够显著降解食品体系中的农药残留，但其降解机理尚不明确。本课题拟以茶饮料中主要的水溶性农药啶虫脒和吡虫啉为目标物，研究PEF作用下影响农药降解的因素及降解动力学；采用气相色谱质谱和液相色谱串联质谱技术全面筛查农药降解中间产物，采用离子色谱分析降解终产物，对气相色谱质谱无法确证的产物创新性的采用制备色谱分离富集，结合高分辨质谱、核磁共振和近红外光谱技术进行鉴定；跟踪降解产物随处理条件的动态变化，明确PEF作用下农药的降解机理，为PEF降解茶饮料及其它食品中的农药残留提供理论依据。

茶饮料是当今世界三大无酒精饮料之一。在现代茶树种植中，农药的使用控制了病虫害的发生，对于茶叶产量的提高和质量的提升均起到了积极作用。但因茶叶种植中农药安全使用水平和监管力度有限，致使茶饮料中吡虫啉和啶虫脒等水溶性农药残留问题突出。研究证明，啶虫脒和吡虫啉具有细胞毒性、神经毒性等。为保证食品安全，降低茶饮料中的农药残留势在必行。. 本项目以控制茶饮料中的农药残留为目标，研究PEF技术降解吡虫啉和啶虫脒残留。在发现PEF对吡虫啉和啶虫脒无显著降解效果后，项目成员经过长时间探索，筛选出可被PEF降解的有机磷农药——甲拌磷和马拉硫磷，进而继续深入研究。研究发现，PEF电场强度、处理时间和农药初始浓度对农药的去除均有显著影响，而温度和pH值对农药的去除无显著的影响；当电场强度20 kV/cm，处理时间为512 µs时，所得甲拌磷和马拉硫磷的降解率最大，分别为88.4%和22.6%；动力学研究表明，PEF处理时，甲拌磷浓度的变化符合Weibull模型和Hülsheger模型，而马拉硫磷浓度的变化符合Hülsheger模型；同时，该实验中证实了PEF对农药的去除具有选择性。. 为控制茶饮料中的吡虫啉和啶虫脒，本研究采用紫外照射控制茶饮料中的农药残留。研究发现，紫外照射能有效去除茶饮料中的吡虫啉和啶虫脒，且紫外光强度、照射时间、茶汤浓度对两种农药的去除率均有显著影响；当紫外光强度为650μW/cm2时，紫外光照射1:50绿茶浸提原茶汤稀释10倍的茶饮料120min，吡虫啉和啶虫脒的降解率达到最大，分别为75.8%和26.0%，此时茶饮料中茶多酚、生物碱和儿茶素的保留率均超过70%；紫外光作用下，两种农药的降解符合一级动力学模型；在鉴定降解产物的基础上，提出了紫外照射降解吡虫啉和啶虫脒的机制。. 同时，开展了膜技术去除茶饮料中吡虫啉和啶虫脒的研究。研究发现，膜技术能有效降低茶饮料中的吡虫啉和啶虫脒残留，且膜孔径、操作压力、茶汤浓度对去除率均有显著影响；当膜孔径为0.22μm、操作压力为0.01Mpa，茶水比为1:200时，吡虫啉和啶虫脒的去除率最高，分别为91.7%和92.5%；该条件下，茶饮料中茶多酚和生物碱的保留率均超过70%。.该项目的完成为PEF技术、紫外和膜技术控制茶饮料和其他食品中的农药残留提供了理论基础。.