胡萝卜微波真空干燥试验研究

以胡萝卜为原料，采用均匀设计对微波真空干燥的微波功率、干燥温度及料层厚度进行试验研究，分析各试验条件下的水分含量及胡萝卜素含量，得到了干燥曲线和胡萝卜素保有量曲线，得出了胡萝卜失水量、胡萝卜素含量与各因素之间的回归方程，可用于描述胡萝卜的微波真空干燥特性。     

微波干燥RDX新技术研究

以含水率10%的RDX为研究对象,采用特制的微波真空干燥仪干燥一定量的炸药,详细考察了各种因素对炸药干燥时间的影响.结果表明,在真空度为0.080 MPa,微波功率为1 400 W,物料层厚度为20 mm的条件下,923 g含水率为10%的RDX完全干燥时间为1 090 s,远小于常规干燥的7～8 h;当物料厚度为15～20 mm时干燥时间最佳.微波真空干燥对RDX的机械感度等性能无明显影响.     

黄精微波真空-热风联合干燥工艺研究

以黄精含水率为指标,采用单因素和均匀实验方法,对黄精微波真空干燥工艺进行优化,考察联用的热风干燥温度和时间对黄精多糖含量及其抗氧化活性的影响。结果表明,微波真空-热风联合干燥的最优工艺条件为:微波功率2 k W、间歇比1.67(75/45),真空度0.085 MPa,微波真空干燥37 min,再在55℃的热风下干燥约77 min。在该条件下,黄精干制品多糖含量达61.7 mg/g,对O^(2-)的抑制率达24.1%。微波真空-热风联合干燥技术可以应用于黄精的干燥。     

黄精微波真空-热风联合干燥工艺研究

以黄精含水率为指标,采用单因素和均匀实验方法,对黄精微波真空干燥工艺进行优化,考察联用的热风干燥温度和时间对黄精多糖含量及其抗氧化活性的影响。结果表明,微波真空-热风联合干燥的最优工艺条件为:微波功率2 k W、间歇比1.67(75/45),真空度0.085 MPa,微波真空干燥37 min,再在55℃的热风下干燥约77 min。在该条件下,黄精干制品多糖含量达61.7 mg/g,对O~(2-)的抑制率达24.1%。微波真空-热风联合干燥技术可以应用于黄精的干燥。     

梅州金柚柚子皮的真空冷冻干燥工艺研究

目的以梅州金柚柚子皮为原料,研究柚皮真空冷冻干燥工艺技术,确定最佳工艺参数和加工工艺,为柚皮综合利用提供参考依据。方法通过单因素实验和正交实验设计,以冻干速率作为考察指标,研究了压力(真空度)、加热温度、物料厚度对真空冷冻干燥速率的影响。结果实验表明,对冻干柚皮干燥速率的影响主次顺序为加热温度、压力(真空度)、物料厚度,最佳工艺条件分别为:加热温度50℃、压力(真空度)40 Pa、物料厚度5 mm,在此干燥工艺条件下,产品在色泽等方面保持较好。结论该正交试验筛选出的工艺稳定可行。     

微波真空组合干燥技术的研究

微波真空干燥是综合微波干燥和真空干燥各自优点的一项新技术,将微波干燥的快速高效性和真空干燥的低温高质相结合,在真空条件下利用微波对物料进行干燥处理,从而实现物料的快速低温干燥。着重阐述了微波真空组合干燥技术的机理、特点、干燥动力学以及影响微波真空干燥的重要因素,并对微波真空组合干燥的应用研究进行了介绍。     

典型中华菜肴鱼香肉丝的真空冷冻干燥工艺研究

以鱼香肉丝这一典型的中华菜肴为对象，通过正交实验求出了最佳真空冷冻干燥工艺参数，即物料铺放厚度5mm、升华干燥的真空度140Pa、解析干燥的真空度30Pa、解析时加热板温度20℃。试验得出的影响冷冻干燥的主要工艺因素其次序为：加热板温度、物料铺放厚度、升华压力和解析压力。同时还求出了这种菜肴的复水工艺参数，即复水量为干制品含水率的140％～150％，复水温度65～85℃，复水时间20～30min。最后通过本研究建立的数学模型对干燥时间进行了验证。     

响应曲面法漂白紫胶微波-真空干燥工艺研究

为提高漂白紫胶产品质量及生产效率,采用微波-真空干燥漂白紫胶研究了不同压强、微波功率和干燥时间对漂白紫胶产品颜色指数和含水率的影响,用响应曲面法（RSM）设计试验并建立了该工艺条件的拟合方程。结果表明,拟合方程的拟合度较高,所建立的数学模型可以用于描述漂白紫胶的微波-真空干燥。漂白紫胶微波-真空干燥的最优条件：干燥压强为3.0 kPa,微波功率为795 W,干燥时间为30 min。在优化条件下进行了验证实验,得到了颜色指数为0.9、含水率为0.028 9kg水/kg干料的产品。     

微波辐射干燥氟化铝的工艺研究

介绍了微波干燥的原理和主要特点，研究了利用微波辐射干燥氟化铝工艺，探讨了微波功率、微波辐射时间、物料质量、物料厚度对氟化铝脱水率的影响。实验的最佳条件为微波功率2．0kW、干燥时间80s、物料质量400g、物料厚度2．0cm。实验结果表明，利用微波辐射干燥，氟化铝含水质量分数小于1％，且干燥时间短、能耗低，实验为工业化提供了必要的参考数据。     

升华干燥过程的(火用)损失分析

通过对物料在升华干燥过程中的Yong损失分析，建立了升华干燥过程的Yong损失分析模型。结合升华干燥动力学模型和Yong损失分析模型，以牛肉为冷冻干燥过程的模型物料，计算了物料表面加热温度、干燥室压力和物料厚度等操作条件的变化对升华干燥过程Yong损失的影响。计算结果表明：随着干燥室压力的增大，物料的Yong损失减小;随着物料表面加热温度的降低，Yong损失减小：随着物料厚度的减小，Yong损失逐渐减小；在冷冻干燥过程中，Yong损失主要集中在升华干燥阶段，在解析干燥阶段，物料表面加热温度的升高不会引起Yong损失的大幅度增加。     

Modeling Microwave Vacuum Drying Kinetics and Moisture Diffusivity of Carrot Slices

Carrot slices of 3.5 mm thickness were dried in a laboratory microwave vacuum dryer at five different microwave power density levels of 2, 4.66, 7.33, 10, and 12.66 W/g and at three vacuum chamber pressure levels of 6.66, 19.98, and 33.3 kPa to 4–6% d.b. moisture content. Inside the dryer the sample holding plate was rotated with the speed of 4 rpm for uniform microwaves application. The drying rates were increased with the increase in microwave power density at all pressure levels and the Page model was found to be the most suitable model to predict the drying behavior of carrot slices at all process conditions. The Page model drying rate constant (k, min^?1) showed high correlation with microwave power density at constant pressure by a power law equation and showed a logarithmic relationship with the microwave power density and pressure. Similar to the drying rate constant, the average moisture diffusivity at constant pressure was found to be function of microwave power density by power law equation as well as was also dependent on the power density and pressure by a logarithmic relationship.     

Modeling Microwave Vacuum Drying Kinetics and Moisture Diffusivity of Carrot Slices

Carrot slices of 3.5 mm thickness were dried in a laboratory microwave vacuum dryer at five different microwave power density levels of 2, 4.66, 7.33, 10, and 12.66 W/g and at three vacuum chamber pressure levels of 6.66, 19.98, and 33.3 kPa to 4-6% d.b. moisture content. Inside the dryer the sample holding plate was rotated with the speed of 4 rpm for uniform microwaves application. The drying rates were increased with the increase in microwave power density at all pressure levels and the Page model was found to be the most suitable model to predict the drying behavior of carrot slices at all process conditions. The Page model drying rate constant (k, min^-1) showed high correlation with microwave power density at constant pressure by a power law equation and showed a logarithmic relationship with the microwave power density and pressure. Similar to the drying rate constant, the average moisture diffusivity at constant pressure was found to be function of microwave power density by power law equation as well as was also dependent on the power density and pressure by a logarithmic relationship.     

干燥方式对红枣动力学及挥发性成分的影响

采用热风干燥、真空冷冻干燥和微波真空干燥对红枣进行干燥处理，结合顶空固相微萃取-气相色谱-质谱（headspace solid-phase microextraction-gas chromatography-mass spectrometry，HS-SPME-GC-MS）和电子鼻对枣片挥发性成分进行了分析，并对比了3种干燥方式对红枣色泽、动力学和挥发性成分的影响。结果表明，热风干燥和微波真空干燥对枣片色泽影响较大，真空冷冻干燥能够更好的保持原始色泽；对动力学方程进行拟合，发现Page 模型为预测红枣3种干燥方式干燥特性最适合的数学模型；干燥对枣片挥发性成分种类及相对含量差异显著，其中干燥前后相同的挥发性成分有19种。挥发性物质主要有酸类、酯类、醇类、醛类、酮类、烃类、杂环类和其他化合物，干燥过后枣片中酸类和烷烃类挥发性成分相对含量显著增加，醛类和杂环类物质显著降低。电子鼻结果表明干燥后枣片香气特征与新鲜红枣有较大的区别，热风干燥和微波真空干燥香味特征较为接近，微波真空干燥枣片的焦甜香特征更为明显。相较于热风干燥和真空冷冻干燥，微波真空干燥效率较高、能耗较低、周期较短，更适于制备干燥枣片。     

MICROWAVE VACUUM DRYING KINETICS OF SOME FRUITS

Microwave vacuum drying kinetics of three fruits (namely, apple, kiwi and pear) were studied by introducing an one-parameter empirical mass transfer model, involving a characteristic parameter (drying constant), as a function of process variables. The model was tested with data produced in a microwave oven equipped with vacuum apparatus, using non-linear regression analysis. The investigation involved a wide range of microwave power and vacuum pressure levels. The parameters of the model considered were found to be greatly affected by the microwave power level while vacuum pressure affected slightly the process.     

Drying Characteristics and Kinetics of Vacuum Microwave–Dried Potato Slices

Vacuum microwave dehydration characteristics and drying kinetics of potato slices were evaluated using a laboratory-scale dryer. The test materials were placed on a rotating tray to allow uniform exposure to the microwave field. The effect of drying conditions on the drying characteristics was investigated. As expected, higher drying rates were obtained with higher microwave power and lower vacuum levels. The effect of vacuum pressure on drying rate was not as significant as that of microwave power. The Henderson & Pabis model provided better simulation of the drying curves for potato slices. Empirical models are presented for the drying rate constant as a function of the microwave power and vacuum pressure for potato slices under the range of operating conditions tested.     

MICROWAVE VACUUM DRYING KINETICS OF SOME FRUITS

ABSTRACT

Microwave vacuum drying kinetics of three fruits (namely, apple, kiwi and pear) were studied by introducing an one-parameter empirical mass transfer model, involving a characteristic parameter (drying constant), as a function of process variables. The model was tested with data produced in a microwave oven equipped with vacuum apparatus, using non-linear regression analysis. The investigation involved a wide range of microwave power and vacuum pressure levels. The parameters of the model considered were found to be greatly affected by the microwave power level while vacuum pressure affected slightly the process.     

Freeze Drying of Apple Slices with and without Application of Microwaves

In this study, Fuji apple slices were dehydrated using freeze drying (FD) combined with microwave assisted with vacuum drying (VMD). The optimal parameter for the diversion point of moisture content from FD to VMD process was at the moisture level of 21%, and for VMD the optimal parameter for vacuum pressure was at 9.15 kPa and microwave power density was at a level of 3.18 w/g. The results show that the two-step technique can significantly reduce total FD time required by up to 40%, while the nutritional value of the dried apple chips remained unchanged compared to FD used alone.     

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 glutinous components on matrix microstructure during the drying process of plant porous materials

This paper compares the drying of two plant materials by microwave drying and hot air drying using Chinese angelica and Astragalus slices as examples, with the aim to study the influence of glutinous components in plant tissue on drying behavior of plant materials. In cases studied in this paper, the microwave drying time of Chinese angelica slices is reduced to 1/16 (50 min/810 min), that of Astragalus slices is reduced to 1/6 (30 min/180 min) as compared to hot air drying. The total pore volume of hot air dried Chinese angelica slices sample is 1.5 times of microwave dried sample, but that of microwave dried Astragalus slices sample is 2.5 times of hot air dried sample. In compare to microwave dried sample, the re-hydration ratio of hot air dried sample of Chinese angelica slices sample increases by 7.1%, but that of Astragalus slices sample decreases by 6.6%. This can be partly explained by the characteristics of pore size distribution inside matrix, resulted by the less deformation of glutinous component inside matrix during microwave drying process as compared to hot air drying. It is also confirmed that larger porosity and total volume of sample, higher re-hydration ratio of sample.