固态食品常压吸附流化冷冻干燥的研究

至今为止,冷冻干燥技术得到应用的只有真空冷冻干燥一种,本文提出了常压吸附剂流化冷冻干燥,并具体阐述了数学模型和实验装置。通过与真空冷冻干燥进行比较,认为常压吸附流化冷冻干燥值得进一步深入研究,具有发展和应用前景。     

Modeling of Vacuum Desorption in Freeze-Drying Process

A mathematical model of multicomponent vacuum desorption, which occurs in vacuum freeze-drying process, was developed. In freeze-drying porous biomaterials and pharmaceuticals are considered and the vacuum freeze-drying process, especially the moisture desorption in its final stage, is investigated. In this article, the drying with conductive heating and constant contact surface temperature was considered. Pressure drop is taken into account in the model formulation but was neglected in process simulation because of thin material layers undergoing freeze-drying. Model equations were solved by numerical method of lines. Moisture content and temperature distributions within the drying material were predicted from the model as a function of drying time.     

微波冷冻干燥技术的发展及关键技术研究

微波冷冻干燥是将高效的微波辐射加热技术和真空冷冻干燥技术相结合的极具应用价值的一项新技术。文章综述了国内外微波冻干研究的进展情况,并对其中辉光放电、加热均匀性、控制策略优化以及干燥终点判别等问题进行分析并提出解决这些问题相应的技术方法和手段,为改进和优化微波真空冷冻干燥设备提供了理论依据和技术支持。     

Modeling of Vacuum Desorption in Freeze-Drying Process

Abstract

A mathematical model of multicomponent vacuum desorption, which occurs in vacuum freeze-drying process, was developed. In freeze-drying porous biomaterials and pharmaceuticals are considered and the vacuum freeze-drying process, especially the moisture desorption in its final stage, is investigated. In this article, the drying with conductive heating and constant contact surface temperature was considered. Pressure drop is taken into account in the model formulation but was neglected in process simulation because of thin material layers undergoing freeze-drying. Model equations were solved by numerical method of lines. Moisture content and temperature distributions within the drying material were predicted from the model as a function of drying time.     

黑加仑真空冷冻与微波真空联合干燥工艺研究

以黑加仑为原料,对其进行了真空冷冻与微波真空联合干燥工艺的研究。结果表明：先真空冷冻后微波真空干燥（FDMV）的组合方式是可行的;联合干燥合理工艺参数为：微波功率1．34kW。绝对压力11kPa,转换含水率为20％（wb）;通过试验验证,联合干燥生产的脱水黑加仑的感官品质和营养成分接近真空冷冻干燥,联合干燥方式对节省干燥时间和降低能耗是有效的。     

真空冷冻干燥设备节能改进的再探讨

针对2010年8月22日出版的《干燥技术与设备》专题综述"真空冷冻干燥设备节能改进的探讨"的内容进行后续,前文主要叙述了真空冷冻干燥设备的配置的动力系统上可改进的领域,本次主要从设备本身与管理上探讨节能减排的途径。     

丁二磺酸腺苷蛋氨酸冻干工艺研究

为建立合适的丁二磺酸腺苷蛋氨酸冻干工艺,采用真空冷冻干燥法,对丁二磺酸腺苷蛋氨酸冻干条件如共晶点、装量、预冻程序、升华温度、升华真空度及解吸干燥温度等进行研究。结果显示：冻干工艺：装量为液面高度小于10 mm,预冻程序为预冻至-40℃,然后回温至-10℃,再降至-50℃,在真空度10～30 Pa,-25℃下升华,35℃解吸干燥。此工艺制备的丁二磺酸腺苷蛋氨酸外观好,产品质量符合国家标准。     

Optimization of freezing parameters for freeze-drying mango (Mangifera indica L.) slices

Today, there is an increasing trend toward consuming healthful food products, and dried fruits are one option for obtaining desirable nutrition in dehydrated products. Proper drying method selection is important for minimizing quality losses. Lyophilization (freeze-drying), a technique that removes water by sublimation at low temperature, can produce excellent dried products. Fast vacuum induction during freezing has been proposed as a way to control ice nucleation and to obtain enhanced lyophilized pharmaceutical products. However, this technique has not yet been applied to food freeze-drying. The aim of this work was to evaluate the effects of the freezing rate (0.4, 0.25, and 0.1°C/min), the minimum chamber pressure during vacuum-induced surface freezing (900, 700, and 500?mTorr) and the sample temperature at which the induced vacuum was applied (0, ?2, and ?4°C) on the total process time, final moisture content, rehydration capacity, total color difference, and total polyphenol content during the lyophilization of mango (Mangifera indica L.) slices. A Box–Behnken design with three factors at three levels was used to design the experiments, to generate the polynomial equations relating the dependent and independent variables, and to determine the optimal operational conditions. The results highlight the reduction of total process time (30%) at high freezing rates and the influence of the tested operating conditions on freeze-drying optimization. It was found that the optimal conditions that satisfy commercial quality goals were pressure between 500 and 650?mTorr, temperature between ?2 and 0°C, and freezing rate values close to 0.4°C/min.     

真空冷冻干燥鸡蛋粉的实验研究

用电阻法测定了蛋清、蛋黄以及全蛋混合液的共晶点温度，通过对蛋清、蛋黄以及全蛋的多次冻干实验．分析了三种蛋粉的冻干曲线，探索了真空冷冻干燥鸡蛋粉的工艺。     

Drying Kinetics and Energy Consumption in Vacuum Drying Process with Microwave and Radiant Heating

The general objective of this work is to analyze energy input in a vacuum process with the incorporation of microwave heating. Thus, necessary criteria for designing an efficient freeze-drying operation are considered through the analysis of strategies based on the combination of different intensities of radiant and microwave heating. The other aim of this research topic is to study the kinetics of drying in relation to mass transfer parameters. Five freeze-drying strategies using both heating systems were used. Consequently, energy input could be related to diffusivity coefficients, temperature and pressure profiles during dehydration of the product and analyzed in comparison to a conventional freeze-drying process.     

微波及辐射真空干燥过程中的干燥动力学及能量消耗

The general objective of this work is to analyze energy input in a vacuum process with the incorporation of microwave heating. Thus, necessary criteria for designing an efficient freeze-drying operation are considered through the analysis of strategies based on the combination of different intensities of raxiiant and microwave heating.The other aim of this research topic is to study the kinetics of drying in relation to mass transfer parameters.Five freeze-drying strategies using both heating systems were used. Consequently, energy input could be related to diffusivity coefficients, temperature and pressure profiles during dehydration of the product and analyzed in comparison to a conventional freeze-drying process.     

How to Meet the Freeze Drying Standard in Combined Drying Processes: Pre and Finish Drying of Carrot Dice

Freeze-drying (FD) processes are well known to produce high-quality consumer products. Major problems are long drying times, high investment costs, and resulting maintenance and operating costs that make FD a very costly process. In this study, the potential of air drying (AD) and microwave vacuum drying (MVD) is tested to reduce freeze-drying times and make better utilization of the investment by combining FD with alternative lower cost drying processes using a pre or finish drying step while preserving the qualwity of the final product. Using carrot dice as a sample product, predrying did not lead to the desired qualities and reduction in drying time, whereas finish drying produced promising results. FD/MVD was 40% faster than pure FD and achieved freeze-drying standards regarding volume retention, shape, color, and rehydration. The good performance of microwave vacuum finish drying can directly be traced back to a time effect that is possibly linked to a characteristic collapse time of the cellular matrix. In order to use this effect, a stable skeleton must have developed at the point of process changeover, changeover has to be immediate, and finish drying has to be quick.     

超声雾化喷涂保色牡丹花冻干试验研究

将保色溶液超声雾化并对牡丹花进行喷涂护色处理,对处理过的牡丹花进行真空冷冻干燥,研究了保色溶液组成、雾化喷涂时间等指标对干花品质的影响。结果表明：超声雾化喷涂保色液具有明显的保色、保形作用,冷冻干燥后牡丹干花的颜色和形状保持得很好。     

辐射传热冷冻干燥速率的简捷估算

对Sheng 和Peck的辐射传热冷冻干燥模型进行简化，将该模型中升华阶段物料干燥层的误差函数温度分布近似为线性分布。计算表明，其结果与实验值及Sheng和Peck模型的预测值很接近。这种冷冻干燥过程中物料含水率和温度分布的简捷估算方法，在工程应用中十分方便。     

MICROWAVE FREEZE DRYING CHARACTERISTICS OF BEEF

Microwave freeze drying characteristics of unsaturated raw beef were studied experimentally for various levels of electric field strength, vacuum pressure, sample thickness and initial saturation. The results show that drying time is proportional to initial saturation and inversely proportional to the electric field strength and sample thickness. The effect of vacuum pressure on drying time is negligible. Some advantages of microwave freeze-drying over conventional freeze drying with radiant heating are pointed out     

Studies on the Microwave Freeze Drying Technique and Sterilization Characteristics of Cabbage

The vacuum freeze-drying (FD) technique used in the food industry can yield a high-quality product, but it is very expensive and requires a long processing time. Besides, the quantity of microorganisms in FD products can often exceed the required standard. As a result, it will be important to develop a new freeze-drying technique. In this article, cabbage was used as a model material, and the microwave field was used as a heat source to supply sublimation heat so that the drying time was shortened greatly. The effect of the microwave sterilization during the drying process was evaluated. Effects of the pressure, thickness of material being dried, and the input microwave power on such indices as drying time and the microorganism number were studied. Compared with the method of ordinary freeze drying, microwave freeze drying (MFD) can greatly reduce the drying time and has a notable sterilization effect.     

Studies on the Microwave Freeze Drying Technique and Sterilization Characteristics of Cabbage

The vacuum freeze-drying (FD) technique used in the food industry can yield a high-quality product, but it is very expensive and requires a long processing time. Besides, the quantity of microorganisms in FD products can often exceed the required standard. As a result, it will be important to develop a new freeze-drying technique. In this article, cabbage was used as a model material, and the microwave field was used as a heat source to supply sublimation heat so that the drying time was shortened greatly. The effect of the microwave sterilization during the drying process was evaluated. Effects of the pressure, thickness of material being dried, and the input microwave power on such indices as drying time and the microorganism number were studied. Compared with the method of ordinary freeze drying, microwave freeze drying (MFD) can greatly reduce the drying time and has a notable sterilization effect.     

Effect of Microwave-Vacuum Drying on the Carotenoids Retention of Carrot Slices and Chlorophyll Retention of Chinese Chive Leaves

Microwave-vacuum drying, and combined microwave-vacuum with air or vacuum drying were investigated as potential methods for drying green and high-carotenoid vegetables of Chinese chive leaves and carrot slices. The samples were dried by microwave-vacuum until the moisture content reached about 20% (wet basis), and then by conventional air drying at the temperature of 45-50°C or conventional vacuum drying at the temperature of 55-60°C or by continued microwave-vacuum drying at lower power level to final moisture content about 6% (wet basis). The carotenoid retention of carrot slices and chlorophyll retention of Chinese chive leaves, dried by these methods, was evaluated and compared with those dried by freeze-drying and conventional hot-air drying. The comparison showed that the carotenoid retention of carrot slices and chlorophyll retention of chive leaves, dried by the current methods, was very close to or even as much as those dried by freeze-drying and much better than those dried by conventional hot-air. Blanching was not necessary when using microwave-vacuum drying or combined microwave-vacuum with conventional hot-air drying or vacuum drying, because the activity of enzymes which were responsible for the degradation of color was greatly reduced with extremely rapid decreasing of moisture, and because oxygen was absent in microwave-vacuum drying.     

Effects of drying on the production of polyphenol-rich cocoa beans

The current study emphasizes on the effects of four drying methods, namely, oven drying, adsorption drying, freeze-drying, and vacuum drying on the total polyphenol content and antioxidant activity of unfermented cocoa beans. The comparison of drying kinetics analysis showed that adsorption drying method dried faster than other methods. On comparing the results of total polyphenol contents and antioxidant activity, freeze-drying method showed the optimal results and the lowest values were recorded by oven drying. The sensory analysis of cocoa beans after drying showed low cocoa flavor and high astringency scores.     

MICROWAVE FREEZE DRYING CHARACTERISTICS OF BEEF

ABSTRACT

Microwave freeze drying characteristics of unsaturated raw beef were studied experimentally for various levels of electric field strength, vacuum pressure, sample thickness and initial saturation. The results show that drying time is proportional to initial saturation and inversely proportional to the electric field strength and sample thickness. The effect of vacuum pressure on drying time is negligible. Some advantages of microwave freeze-drying over conventional freeze drying with radiant heating are pointed out