Effect of Osmotic Dehydration with Pulsed Vacuum on Hot-Air Drying Kinetics and Quality Attributes of Cherry Tomatoes

The effects of osmotic dehydration (OD) with or without pulsed vacuum (PV) on hot-air drying kinetics and quality attributes of cherry tomatoes were investigated. Both OD and PVOD pre-treatments were performed for 3 h at 50°C in 50 and 70^o Brix sucrose solutions with a solution-to-fruit mass ratio of 4:1, and PVOD was applied for 15 min before OD at atmospheric pressure. Samples were further dried at air temperature of 70°C. Effective moisture diffusivity (D _eff) of osmotically dehydrated samples increased gradually while the D_eff curve of fresh samples had a plateau stage during hot air drying. Lower glass transition temperature, T_g, values of osmotically dehydrated samples indicated that they needed a lower storage temperature. Both OD and PVOD pre-treatments had advantages in shortening drying cycles and improving quality of products. Compared with air drying, osmo-air drying decreased the total drying time, color change, and hardness of dried samples by 32.26%, 18.11%, and 88.21%, respectively, and increased volume ratio and vitamin C retention rate by 72.31% and 125.82%. As compared with OD, PVOD decreased color change and hardness by 28.48% and 45.17%, increased volume ratio and vitamin C retention rate by 27.41% and 17.77%, but there was no significant difference shown in drying time. Therefore, osmotic pre-treatment can shorten the total dehydration time, and improve the general quality of dried cherry tomatoes.     

Kinetics and Mass Transfer during Atmospheric Freeze Drying of Red Pepper

Drying is applied for moisture removal to allow safe and extended storage. Red pepper (Capsicum annum) samples were heat pump dried in fluidized bed at different air temperatures. A slightly modified solution of the diffusion equation was used to describe the kinetics and drying rates of red pepper. The model well described the low- and medium-temperature drying processes. The determined effective mass diffusivities varied from 0.7831 to 4.0201 × 10^-9 m²/s and increased consistently with drying air temperature. The mass diffusivity was correlated to temperature by linear regression with coefficient of determination equal to 0.999 and negligible standard error.     

Kinetics and Mass Transfer during Atmospheric Freeze Drying of Red Pepper

Drying is applied for moisture removal to allow safe and extended storage. Red pepper (Capsicum annum) samples were heat pump dried in fluidized bed at different air temperatures. A slightly modified solution of the diffusion equation was used to describe the kinetics and drying rates of red pepper. The model well described the low- and medium-temperature drying processes. The determined effective mass diffusivities varied from 0.7831 to 4.0201 × 10^?9 m²/s and increased consistently with drying air temperature. The mass diffusivity was correlated to temperature by linear regression with coefficient of determination equal to 0.999 and negligible standard error.     

微波真空干燥工艺参数对猕猴桃切片品质的影响

微波真空干燥技术是在真空条件下利用微波能对物料进行干燥加工的一项新技术,本实验以猕猴桃切片为研究对象,以干制品复水率、维生素C含量以及干燥时间为指标,在单因素试验的基础上,通过3因素3水平的二次回归正交试验,研究了微波功率、物料厚度、干燥室压力对猕猴桃切片干燥特性的影响。结果表明：在微波功率为800W、切片厚度为4mm、干燥室压力为0．04MPa的条件下,微波真空干燥猕猴桃切片的干制品质量最好,确定了猕猴桃切片微波真空干燥较优工艺参数条件。     

Assessment of Osmotic Process in Combination with Coating on Effective Diffusivities during Drying of Apple Slices

The effect of carboxymethyl cellulose (CMC) coating on the mass exchanges during the osmotic dehydration of apples and its effect on the quality of final product were studied. Coating semi-rings of apple with CMC solution (1%) was found to prevent solute uptake and to reduce salt diffusion coefficient from 4.35 × 10^-10 m²/s to 2.86 × 10^-10 m²/s. However, coating did not significantly affect the diffusivity of water. The effective diffusivity of salt and consequently solids gain were found to be depended on the concentration of CMC solution in the range of 0-1%. Increasing the concentration of CMC further from 1% had no effect on the mass exchanges during the osmotic process. Maximum performance ratio, defined as water loss/solids gain, and the lowest solids diffusion was observed for coated samples (with 1% CMC solution) treated with an osmotic solution containing glucose syrup (50%) and NaCl (2%).     

Assessment of Osmotic Process in Combination with Coating on Effective Diffusivities during Drying of Apple Slices

The effect of carboxymethyl cellulose (CMC) coating on the mass exchanges during the osmotic dehydration of apples and its effect on the quality of final product were studied. Coating semi-rings of apple with CMC solution (1%) was found to prevent solute uptake and to reduce salt diffusion coefficient from 4.35 × 10^?10 m²/s to 2.86 × 10^?10 m²/s. However, coating did not significantly affect the diffusivity of water. The effective diffusivity of salt and consequently solids gain were found to be depended on the concentration of CMC solution in the range of 0–1%. Increasing the concentration of CMC further from 1% had no effect on the mass exchanges during the osmotic process. Maximum performance ratio, defined as water loss/solids gain, and the lowest solids diffusion was observed for coated samples (with 1% CMC solution) treated with an osmotic solution containing glucose syrup (50%) and NaCl (2%).     

Influence of Temperature,Air Velocity,and Ultrasound Application on Drying Kinetics of Grape Seeds

The objective of this work was to determine the influence of temperature, air velocity, and ultrasound application on the drying kinetics of grape seeds. The drying kinetics were determined at 1.0, 1.5, 2.0, and 3.0 m/s and at 40, 50, 60, and 70°C. At 1.0 and 1.5 m/s, the experiments were carried out with and without ultrasound application. To establish the influence of the variables on the drying kinetics, the results were modeled by means of both the Peleg and a diffusion model. The activation energy was determined (Arrhenius' equation). For an air velocity of over 1.5 m/s, it was determined that the external resistance to mass transfer was negligible. No influence of ultrasound application was observed, probably due to the fact that grape seeds are very hard and have a low level of porosity.     

Optimizing Drying Conditions for the Microwave Vacuum Drying of Enzymes

The aim of this study was the methodological use of experimental planning for the optimization of microwave vacuum drying of enzymes using α-amylase as a model. A factorial in star designwas used to optimize the microwave vacuum–drying process, and the variables were power output and vacuum pressure. The material dehydrated by this technique was analyzed with regard to its enzymatic activity, water activity, and moisture content. Response surface methodology was used to estimate the main effects of vacuum pressure and power on the enzymatic and water activities. The experimental in star design revealed that microwave vacuum drying is influenced mainly by power. The dehydrated product showed high enzymatic activity and low water activity.     

A Numerical Study on the Convective Heat Transfer Characteristics of Pulsed Impingement Drying

Impinging jets issuing from the tailpipe of pulse combustors have been evaluated in recent studies for possible applications in rapid drying of continuous sheets such as grades of paper, textiles, etc. In order to further understand the effect of pulsed flows on the heat and mass transfer rates of impinging jets, a numerical study was performed on a two-dimensional pulsating impinging jet array. A computational fluid dynamics approach was used to examine the effect of periodic sinusoidal pulsation on the local Nusselt number distribution of the wet target surface being dried. Because a high temperature and large temperature difference between the jet flow and impingement surface are used to obtain high heat transfer rates in impingement drying, the thermophysical properties of jet flows were taken into account in the present mathematical model. A parametric study including phase angle and frequency as well as amplitude of pulsating flows was conducted for optimization and design of pulsating jet arrays. Examination of the velocity and thermal fields showed that the instantaneous heat transfer rate on the target surface was highly dependent on the mass transfer characteristic and development of the hydrodynamic boundary layer with time.     

卡纸涂层对EB固化直接真空镀铝工艺的影响

通过改变卡纸涂布量和涂层中瓷土与碳酸钙的比例,研究了卡纸涂层对电子束固化直接真空镀铝工艺的影响。结果表明,随卡纸涂料量提高,表征涂层开放程度的油墨吸收性也随之提高,但卡纸的耐折性能则下降,电子束（EB）固化预涂料涂布量也随之增大;卡纸涂层材料中颜料的组成对卡纸性能及EB固化涂料预涂量有影响,随着颜料中瓷土含量降低,碳酸钙含量提高,涂层的开放程度提高,纸张光泽度下降。     

Influence of Salt and Surfactant on Copper Removal by Xanthan Gum-g-Itaconic Acid/Bentonite Hydrogel Composite from Water Using Fractional Factorial Design

A novel xanthan gum-g-itaconic acid/bentonite (XG-g-PIA/BET) hydrogel composite was synthesized using free radical polymerization in the presence of ammonium persulfate as initiator and N,N’-methylenebis(acrylamide) as crosslinker. The Fourier transform infrared spectroscopy spectra of XG-g-PIA/BET composite before and after adsorption gave strong evidence of the successful adsorbance of copper ions with COOH groups. Influence of the presence of three typical salts (NaCl, CaCl₂, and FeCl₃) and three types of surfactants including anionic (Brij 35), cationic (N-Cetyl-N,N,N-trimethyl ammonium bromide), anionic (sodium dodecyl sulfate), and their two-term interactions on copper ions adsorption capacity were investigated using 32 experiments with fractional factorial experimental design. The analysis of variance (ANOVA) showed that the fitted model had a significant p value (<0.0001), and except FeCl₃, all other variables present in the aqueous solution increased the copper adsorption capacity. In addition, there was no significant two-term interaction between different variables.     

Spray Drying of Chicken Meat Protein Hydrolysate: Influence of Process Conditions on Powder Property and Dryer Performance

The influence of operational conditions of a spray dryer on powder properties and equipment performance during spray drying of chicken meat hydrolysate was evaluated by a central composite rotatable design. The independent variables were inlet air temperature (120 to 200°C) and feed flow (0.1 to 0.38 kg/h). Spray dryer performance was assessed through estimation of product recovery, outlet air temperature, thermal efficiency, and energy on the dryer, obtained by mass and heat balance in the dryer system. Powder property was characterized in respect to antioxidant activity. The stable free radical diphenylpicrylhydrazyl (DPPH) was used to estimate the antioxidant activity of protein hydrolysate powder. This response varied from 38.7 to 59.4% and was only affected by inlet air temperature. Moreover, the results demonstrate a significant effect of the processing conditions on dryer performance. The increase of feed flow results in higher thermal efficiency and lower energy on dryer. Higher product recovery values were obtained at lower inlet air temperature and feed flow.     

真空玻璃传导和对流传热机理研究

利用传导和对流传热原理,建立了真空玻璃热量的流动和传递数学模型,推导了真空玻璃自由分子状态的导热量、支撑柱及边料的固体导热及真空玻璃的外表对流换热方程.分析了自由对流传热、纯气体、稀薄气体、支撑柱及边料的固体导热机理,探讨了真空玻璃的外表对流换热问题.研究结果表明,在低真空状态下的真空玻璃夹层厚度越小,越有利于由自由对流向纯气体导热方向发展,越有利于真空玻璃传热系数的降低.真空玻璃结构只要保持夹层真空度小于0.313 Pa就使得夹层内成为自由分子导热状态.     

Effects of the operational parameters on carbon recovery and water flux in ultrafiltration using fractional factorial design

The distribution of molecular weight of natural organic matter on the effect of operational efficiency for water treatment units is very important, like coagulation, the biological activated carbon, and chlorination. This work discusses the following three topics: (1) The properties of humic acid were compared using fluorescent spectrometry and optical spectrometry; (2) the variations of carbon recovery and the water flux in the membrane filter after repeated rinsing with a 0.1 M sodium hydroxide and 10 ppm NaOCl mixed cleaner and reuse; and (3) the effect of operational parameters, such as the concentration of humic acid, the operating pressure, the mixer speed, and the fractional reduction in retentate volume, on the membrane filter during the fractionating of organic matter in a stirred cell using Statistica 7 software with fractional factorial design. Humic acid yields both fluorescent peaks of both 240/440 nm and 450/510 nm. Fluorescent organic matter with an emission wavelength of 510 nm can be removed using a 5 kDa polyethersulfone membrane filter with rinsing for 90 min. Rinsing with a mixed cleaner reduced both carbon recovery and water flux, but especially the latter. NaOCl solution included in the mixer cleaner should be considered not only because of its ability to destroy organic matter but also because it might transform the properties of the cleaning membrane surface. With respect to the absolute magnitude of the effect of the four factors on the water flux ratio, the humic acid concentration affected the carbon recovery more than the other three factors. The humic acid concentration is negatively correlated with carbon recovery. The operating pressure more strongly affects the water flux than do any of the other parameters. Furthermore, the operational pressure was positively correlated with the water flux.     

真空法合成甲基硫醇锡研究

研究了以巯基乙酸异辛酯和甲基氯化锡为原料，在真空下直接合成甲基硫醇锡的工艺．该法操作简单、成本低，该工艺分3个阶段分别控制压强、温度和时间，其最佳反应条件为，第一阶段2．667kPa，70℃反应2h；第二阶段1．333kPa，80℃反应2h；第三阶段0．667kPa，80℃反应1h。合成的产品质量稳定，并能有效降低污染物的排放量，甲基氯化锡的转化率在99％以上。     

常减压塔顶系统工艺防腐

介绍了７０年代以来我国常减压塔顶系统工艺防腐蚀的概况及其主要进展,并指出了今后工艺的防腐研究的方向。     

氧化钛在真空炼铝过程中氟化行为的热力学研究

从热力学角度引入物质吉布斯自由能函数法讨论在不同压力下,真空炼铝过程中氧化钛和氟化铝反应生成氧化铝及氟化钛的热力学条件.研究表明,该反应常压下在1512 K时发生.而在真空度(即残余)为100～10 Pa时,反应在1144～1061 K时就能发生.比常压下降低368～415 K.因此,减小反应体系的压力,可以使反应...     

Mathematical Modeling of Drying Kinetics for Apricots: Influence of the External Resistance to Mass Transfer

The drying curves of halved and deseeded apricots obtained during convective drying at different temperatures (from 50 to 90°C) have been examined, and a diffusional model, solved by a finite elements method, has been proposed to simulate the drying kinetics. The importance of taking into account both the internal and the external resistances to mass transfer when modeling the drying curves is discussed. Due to the geometry of halved apricots as a hemisphere losing water only through the flat section, the mass transfer coefficient (k_c) was not correctly estimated through an empirical correlation. Only the identification of this coefficient from the experimental results allowed an accurate simulation, decreasing the mean relative error from 12.3±3.8% when k_c was calculated through the Pasternak and Gauvin correlation to 2.9±1.0% when k_c was identified.