果蔬射频变温压差膨化动力机制研究

Puffed fruits and vegetables are crisp and delicious, easily digested and adsorbed, easily carried and eaten. They are well loved by consumer and have a huge market capacity. There exist some problems of traditional puffing techniques, such as: high energy consumption, high oil absorbed products and easily deteriorating. It is urgent to develop new puffing technique. Similar to microwave, radio frequency (RF) is a no ionizing radiation with larger penetration depth. The structure change of starch and protein, morphologic change of cell, physical property of pretreated sample surface layer, puffing kinetics and texture change are the keys to radio frequency assisted variable temperature and pressure puffing (RF-VTPP), which have not yet been reported in the literature so far. In this project, the changes of microstructure of starch and protein are to be discovered with the help of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and 13C CP/MAS NMR. Cellular morphology change and permeability of cell membrane etc. are to be observed by SEM and fluorescent microphotography. Relations of the surface layer property with puffing product texture are to be explored. Four-coupled models are to be established according to the electromagnetic field, heat transfer field, structural mechanics and thin matter transfer theory, using the Comsol Multiphysics software. Puffing kinetic models are to be established using RF strength, initial moisture content, temperature, heating rate, the shape of the materials as variables. The RF-VTPP mechanisms of fruits and vegetables are to be revealed. This research work will provide a solid theoretical support for the industrialized application of RF-VTPP.

膨化果蔬脆片口感鲜美松脆、易于消化吸收、携带食用方便，深受消费者喜爱，市场容量巨大。传统膨化技术存在能耗高、产品含油率高、易氧化变质等问题，迫切需要开展新的膨化技术研究。射频与微波类似，为非电离辐射，但穿透力更大。淀粉/蛋白质结构变化、细胞形态变化、胚料表层物理特性、膨化动力学、质构变化是果蔬射频变温压差膨化研究的关键问题，目前未见有关研究报道。本课题拟使用扫描电子显微镜、红外光谱、核磁共振等仪器，研究淀粉/蛋白质的变化。采用荧光显微照相、扫描电子显微镜等仪器，观察膨化过程中细胞形态和细胞膜通透性等的变化。研究胚料皮层物理特性与膨化产品质构的关系。运用多物理场耦合软件，建立电磁场、传热场、结构力学、稀物质传递四场耦合模型。以射频强度、初始含水率、温度、加热速率、物料形状等为变量，建立膨化动力学模型，揭示果蔬射频变温压差膨化动力机制，为其工业化应用提供理论支撑。

膨化食品口感鲜美松脆、易于消化吸收、携带食用方便，深受消费者喜爱，市场容量巨大。传统膨化技术存在能耗高、产品含油率高、油易氧化变质等问题，迫切需要开展新的膨化技术研究。研究内容和结果：（1）研究不同极板间距、不同初始含水量和不同物料高度对射频膨化小麦粉脆片升温速率、体积比和含水率的影响，得到最佳射频膨化工艺参数；（2）对六种常见干燥动力学模型进行统计分析，拟合得出最佳干燥动力学模型；（3）采用偏光显微镜、场发射扫描电镜、X-射线衍射、傅里叶中红外光谱等研究射频膨化后的小麦淀粉的结构特性，采用DSC、物性测定仪与色度仪研究膨化小麦淀粉的理化特性；（4）研究了复合紫薯片的介电特性、射频升温速率、加热均匀性以及膨化工艺条件。确定了射频膨化干燥对复合紫薯脆片理化特性的影响；（5）测定苹果介电常数和介电损耗因子随频率和温度变化规律，研究苹果块射频加热均匀性；（6）确定在射频变温压差膨化处理过程中，山药-小麦-玉米淀粉片的加热速率和加热均匀性受极板间距、样品厚度的影响；（7）研究了膨化温度、膨化压差和停留时间等参数对膨化零食的脆度、硬度、色差（ΔE）和水分含量的影响。为食品射频真空膨化技术工业化应用提供理论和技术支撑。