红茶芳香物渗透汽化分离中的多组分传递耦合机制及膜性能调控

The content and composition of tea aroma compounds have an important influence on the quality of instant tea beverage, but during the process of instant tea, a large amount of aroma components will lose by degradation or co-boiling with water, which is the main reason for the decrease of the flavor quality of products. Due to the complexity, low concentration and heat sensitive characteristics of aroma components in the extracting solution of instant black tea, the project is aimed at a new way for the separation and recovery of the aroma compounds by pervaporation using organophilic membrane. Multiple model solutions of typical aroma compounds of black tea will be used in experiments to reveal the coupling effect of different compounds during pervaporation. A mass transport model of multi-components pervaporation will be stablished which can be used for practical application by elucidating the mass transport mechanism of multi-component pervaporation, introducing the performance parameters of the membrane materials, and considering the interactions between the components. The structure-activity relationship between physicochemical parameters of membrane, such as surface structure form and hydrophilicity, and separating property by pervaporation will be studied, the regulation method of membrane property aimed at the actual system of multiple objective will be developped, and functional membrane materials will be designed for the property modulation of pervaporation membrane. The project will establish the foundation for the improvement and development of fundamental theory of aroma recovery and promote the application of pervaporation in the recovery of tea aroma.

茶叶芳香物的含量及组成对于速溶茶饮料的品质具有重要影响，而在速溶茶加工过程中，大量的茶叶芳香物因降解或与水共沸流失是导致产品风味品质下降的主要原因。本项目针对速溶红茶提取液中芳香物成分复杂、浓度低及热敏性等特点，探索利用亲有机物性渗透汽化膜对其中的芳香组分进行分离回收的新途径。采用典型红茶芳香物的多元模拟体系揭示不同化合物渗透汽化膜分离过程中的耦合作用规律；阐明多组分渗透汽化传质机理，引入膜材料性能参数，并考虑组分间相互作用，建立可用于指导实际应用的多组分渗透汽化传质模型；明确渗透汽化膜表面结构形态、亲疏水性等理化参数与分离性能间的构效关系，发展面向多目标实际体系的膜性能调控方法，设计功能膜材料，为进一步完善和发展渗透汽化分离食品芳香物的基本理论，促进渗透汽化技术在茶叶芳香物回收中的应用奠定基础。

茶叶中芳香物的种类和含量是决定速溶茶品质的重要因素之一，但茶叶芳香物，尤其是红茶芳香物具有沸点低、浓度低及稳定性差等特点，在传统的速溶茶加工过程中极易损失而影响产品风味品质，成为速溶茶产业发展中亟待解决的关键问题。本项目旨在探索利用渗透汽化技术分离回收红茶及其他植物提取物中芳香物富集回收新途径。.具体的研究内容和结论如下：.（1）分别鉴定并建立了红茶茶汤以及黑莓浓缩汁中挥发性芳香成分信息表，确定了水杨酸甲酯、β-紫罗酮和芳樟醇等为红茶特征性芳香化合物；芳樟醇，苯甲醛和乙酸乙酯等为黑莓浓缩汁特征性芳香化合物。.（2）分别以多壁碳纳米管（MWCNTs）和纳米ZIF-8晶体为填充粒子制备了两种性能稳定的有机/无机杂化膜——MWCNTs(2%wt)/PDMS和ZIF-8(6%wt)/PDMS。在乙醇/水体系中对乙醇的分离通量分别较纯PDMS膜提高了103.5%和84.4%，分离因子提高了7.8%和136.7%。.（3）考察了不同操作条件下红茶及黑莓浓缩汁中特征性芳香物单组分、二元及三元体系模拟溶液的渗透汽化性能，阐明了膜面流速、温度、渗透侧浓度等对各芳香物组分分离性能的影响，并结合热力学性质的计算揭示了多元模拟溶液中组分间耦合效应对渗透汽化性能的影响规律及作用机理。.（4）实际应用表明，两种杂化膜对水溶液中的挥发性芳香物均具有良好分离性能。在优化的参数条件下，MWCNTs/PDMS膜对红茶茶汤中水杨酸甲酯、β-紫罗酮和芳樟醇的分离富集回收率分别为 90.84%、83.40%和 85.80%，渗透侧浓度分别达 4.47mg/L、72.71mg/L 和3.53mg/L； ZIF-8/ PDMS膜对黑莓浓缩汁中芳樟醇，苯甲醛和乙酸乙酯的回收率分别为93.8%，92.1%和75.2%，渗透侧浓度分别为3.6 mg/L、2.03 mg/L和28.6 mg/L。.本项目分别以速溶红茶和黑莓浓缩汁为目标体系，通过膜结构设计、筛选，获得了两种性能稳定的有机/无机杂化混合基质膜，并阐明了两个体系中特征性芳香物在膜相中的溶解-渗透机制及其交互作用；在此基础上，通过分离参数的优化建立了面向应用的芳香物富集、回收技术体系，为速溶茶及浓缩果汁加工行业中挥发性芳香物回收技术的发展提供了理论和技术支撑。