Spreading Pressure-Water Activity and Moisture Relationships in Starchy Materials

ABSTRACT

The spreading pressure values have been calculated by integration of the Gibbs equation using G.A.B. isotherm for different cereal grains and starchy materials. This procedure gives an useful analytic solution the ibtegral avoiding inherent mathematicai instability at very low water activity. It was found a non linear relationship between spreading pressure and water activity being this function weakly dependent on products and temperature. On the other hand a nearly linear relationship was observed between spreading pressure and moisture in the moisture range 0.0–0.15 ( dry basis).     

Moisture Diffusivity in Food and Biological Materials

The spatial distributions of water content and temperature inside moist food or biological materials (native or manufactured) during drying are important in interpretation and prediction of quality changes. The dynamics of drying in modern devices is not simple—for instance, the process of intermittent drying—thus, a liquid diffusion model is expected to be the simplest and hopefully the very effective. In this article, some controversial aspects of the concept of the effective Fickian liquid moisture diffusivity are described and discussed. These discussions are intended to stimulate more interest in working toward a better rationalization of the liquid diffusion concept. It is suggested that such a parameter may even be called a “liquid depletion coefficient” instead to avoid confusion at the fundamental level. An improved alternative model from the effective liquid diffusion model is possible and some new ideas have been explored.     

Moisture Diffusivity in Food and Biological Materials

The spatial distributions of water content and temperature inside moist food or biological materials (native or manufactured) during drying are important in interpretation and prediction of quality changes. The dynamics of drying in modern devices is not simple—for instance, the process of intermittent drying—thus, a liquid diffusion model is expected to be the simplest and hopefully the very effective. In this article, some controversial aspects of the concept of the effective Fickian liquid moisture diffusivity are described and discussed. These discussions are intended to stimulate more interest in working toward a better rationalization of the liquid diffusion concept. It is suggested that such a parameter may even be called a “liquid depletion coefficient” instead to avoid confusion at the fundamental level. An improved alternative model from the effective liquid diffusion model is possible and some new ideas have been explored.     

Production of Fumaric Acid from Raw Starchy Materials by Rhizopus oryzae with SSF

To reduce the manufacturing cost of fumaric acid production by fermentation, four kinds of raw starchy materials were investigated, cassava powder, corn powder, degermed corn powder and starch. By comparing the nitrogen contents in them, carbon/nitrogen ratio of raw materials was the key factor affecting the fumaric acid production by Rhizopus oryzae. Based on this point, degermed corn powder was selected as the best raw starchy material for fumaric acid production. In addition, the simultaneous saccharification and fermentation (SSF) process for fumaric acid production was optimized. With degermed corn powder as substrate at 100 g/L total sugar concentration, the fumaric acid production (35.51 g/L), yield (0.355 g/g) and productivity (0.493 [g/(L.h)]) were obtained via SSF process in a 7-L fermentor.     

Moisture Distribution and Dewatering Efficiency for Wet Materials

This review paper summarizes current research efforts toward a comprehensive view of wet material dewatering, considering the binding energy as the strength to hold water, and rupture energy given to remove moisture from materials.     

Moisture Distribution and Dewatering Efficiency for Wet Materials

This review paper summarizes current research efforts toward a comprehensive view of wet material dewatering, considering the binding energy as the strength to hold water, and rupture energy given to remove moisture from materials.     

Contribution to the Study of Moisture Expansion in Ceramic Materials

Measurements were made of the expansions produced by autoclaving coprecipitated and mixed gels of silica and alumina fired over the temperature range 850° to 1200°C. The effect of adding soda to gels of kaolinite composition was investigated and the compositions of the phases were determined. The results show that amorphous silica has a limited influence and must be modified by alumina or by soda and alumina to produce expansions comparable with those of ceramic bodies. The active material is an amorphous alkali aluminosilicate, to be distinguished from permutites and glass. Formation of glass and crystalline compounds reduces moisture expansion. At low firing temperatures (below 950° C.) the hydration of γyAl₂O₃ to boehmite produces high moisture expansions, but γ-Al₂O₃ modified by silica (silicon spinel) has only a limited influence. Some observations are made on the nature of cristobalite developed during the firing of pure amorphous silica and amorphous silica into which additives were introduced.     

油类原料中的水分对磺基琥珀酸酯盐类加脂剂制备的影响

探讨了油类原料(如酰胺化菜籽油、蓖麻油、Span等)中的水分对磺基琥珀酸酯盐类加脂剂合成反应中单酯化反应、磺化反应和产品性能的影响。从理论上计算出当100 g油类原料中w(H2O)由0%增至3%时,水可能消耗的顺酐从0 g增至16.33 g,可能消耗的无水亚硫酸钠从0 g增至21.00 g,可能生成杂质磺基琥珀酸氢钠从0 g增至40.33 g。并以Span-60为原料,合成出加脂剂(代号S-SCF),验证了不同w(H2O)对合成反应和产物性能的影响。结果表明,当n(羟基)∶n(顺酐)∶n(无水亚硫酸钠)=1∶1∶1,w(H2O)由0.25%增至3%时,顺酐的单酯化率由95.07%降至58.44%,S-SCF的pH由4.8降至4.1,w(S-SCF)=10%的水乳液离心后沉淀的体积分数由0.9%增加到3.7%。因此,预先脱除油类原料中的水分并将其质量分数控制在0.25%以内是十分必要的。该文报告工作的新颖性已为浙江省科技信息研究院于2009年6月28日出具的第200933B2106057号《科技查新报告》所证实。     

Some Considerations in Modeling of Moisture Transport in Heating of Hygroscopic Materials

Hygroscopic materials are those in which the equilibrium pressure of water vapor changes with moisture content and temperature, such as food, soil or wood, etc. Heat and moisture transports are coupled in heating of hygroscopic materials. One of the major links between temperature and moisture changes is water evaporation. There have been different formulations on modeling of evaporation in the past. A typical approach (Model 1 in this article) is to equate the evaporation rate to the rate of local moisture loss. The first part of this paper illustrates that such an approach is physically incorrect based on fundamental conservation relationships. A conservation-based coupled heat and moisture transfer model (Model 2) is presented here based on previous multiphase transport models. It shows that total evaporation rate over the entire material is included in Model 1 while the local evaporation rate is not. The situations when Model 1 may or may not generate large errors are discussed. The second part of this article completes the modeling of evaporation using Model 2. Two types of formulations are given depending on the phase equilibrium of moisture in the hygroscopic materials. When phase equilibrium between water and vapor is assumed for any location at any time, vapor pressure is provided as known variables. In a nonequilibrium approach, evaporation rate needs to be provided. The latter poses numerical difficulties near the material surface, which arises from the possibility that equilibrium state may have a large change near the surface. Further discussions were made on the physical and numerical considerations in using both approaches.     

Moisture Diffusion Inside Paper Materials in the Hygroscopic Range and Characteristics of Diffusivity Parameters

Some current models for moisture diffusion in paper in the hygroscopic range are analyzed. In general, two types of diffusion models can be recognized. Models of the first type treat paper as a homogeneous medium with moisture flux that is proportional to the gradient in moisture content. Although useful in some instances this approach fails frequently because it homogenizes the internal dynamics and relaxation processes occurring within the paper material. Recent studies have shown that a subtler approach which treats paper as a composite of fibers and void spaces is more successful at describing moisture transport dynamics. A review of these studies along with a generalization of this approach to three dimensions is considered here. The parameters appearing in such models can be identified with the physical processes of diffusion through the void space and through the fiber matrix. Diffusivities in these individual phases are supplemented by a local kinetic coefficient representing moisture flux interchange between the void and fiber phases. When the local moisture exchange coefficient takes on large values, the fibers and the void spaces are at local equilibrium with no net exchange of moisture. Under such conditions, the model reduces to the simpler Fickian diffusion model with nonlinear moisture diffusivity equivalent to earlier models.     

镁水泥材料的吸潮返卤性能研究

本文通过定量测定镁水泥板材中总氯离子、自由氯离子、游离氯化镁、钾钠等离子的含量及其与吸潮返卤的关系,并结合物相组成分析,研究探讨了镁水泥材料的吸潮返卤机理.结果表明,自由氯离子是引起镁水泥材料吸潮返卤的主要原凶,其中,由游离氯化镁中的自由氯足引起吸潮返卤的第一原因.镁水泥材料的抗水性对吸潮返卤也有一定的影响.因此,选择合理的MgO/Mgcl<,2>物质的量比、控制原料氯化镁中钠钾等杂质的含量和提高抗水性,是解决镁水泥材料吸潮返卤的重要技术措施.     

Moisture Diffusion Inside Paper Materials in the Hygroscopic Range and Characteristics of Diffusivity Parameters

Abstract

Some current models for moisture diffusion in paper in the hygroscopic range are analyzed. In general, two types of diffusion models can be recognized. Models of the first type treat paper as a homogeneous medium with moisture flux that is proportional to the gradient in moisture content. Although useful in some instances this approach fails frequently because it homogenizes the internal dynamics and relaxation processes occurring within the paper material. Recent studies have shown that a subtler approach which treats paper as a composite of fibers and void spaces is more successful at describing moisture transport dynamics. A review of these studies along with a generalization of this approach to three dimensions is considered here. The parameters appearing in such models can be identified with the physical processes of diffusion through the void space and through the fiber matrix. Diffusivities in these individual phases are supplemented by a local kinetic coefficient representing moisture flux interchange between the void and fiber phases. When the local moisture exchange coefficient takes on large values, the fibers and the void spaces are at local equilibrium with no net exchange of moisture. Under such conditions, the model reduces to the simpler Fickian diffusion model with nonlinear moisture diffusivity equivalent to earlier models.     

混合含氟甲苄醇类菊酯的结构与杀虫活性关系

报道了混合含氟甲苄醇类菊酯对库蚊和家蝇的生物测试。其结果表明该类化合物对测试害虫显示出较高的杀虫活性和较低的抗性比。在抗性品系中，混合含氟甲苄醇类菊酯表现出比单一异构体和氯氰菊酯更高的活性。     

Basic Patterns of Moisture Absorption during the Hydrothermal Treatment of Fibrous and Dispersed Materials with the Periodic Heat and Moisture Supply

Fibre Chemistry - The paper presents an analysis of moisture absorption during the oscillated hydrothermal treatment of fibrous and dispersed materials, which is performed on the basis of kinetic...     

Change in the Properties of Textile Materials Containing Polyester and Cellulose Fibres Caused by Moisture

The hygroscopic properties, swelling, and change in the mechanical properties of thread containing polyester and natural cellulose fibres and one-component thread (yarn) were comprehensively investigated. The kinetics of swelling of textile materials is described by an exponential equation, and the coefficients of this equation are determined. It is shown that for yarn made of fibre blends, the equilibrium sorption and swelling values are satisfactorily described by additive dependences on the component content. It is found that equilibrium swelling is 2-3 times greater than equilibrium sorption of water vapors from air due to different mechanisms of binding of moisture with the fibres. It is shown that the breaking characteristics of flax and cotton varieties of yarn increase in swelling due to an increase in the frictional interaction between the fibres.     

Ordered Mesoporous Materials with Improved Stability and Catalytic Activity

Microporous crystals of zeolites such as Y, Beta, and ZSM-5 are widely used commercial catalysts, but their applications are strongly limited by their small pore sizes. Recent progress in solving this is used to ordered mesoporous materials such as MCM-41, HMS, and SBA-15. These mesoporous materials have pore diameters of 2.0–30 nm and exhibit good catalytic properties for the catalytic conversion of bulky reactants. However, when compared with microporous crystals of zeolites, the catalytic activity and hydrothermal stability are relatively low, which severely hinders their practical applications in industrial catalytic reactions such as petroleum cracking. The relatively low catalytic activity and hydrothermal stability can be attributed to the amorphous nature of the mesoporous walls. In this account, we systemically review the routes for improving catalytic activity and hydrothermal stability of mesoporous materials, which include (1) acidic sulfated zirconia supported in mesoporous materials; (2) strongly acidic and thermally stable mesostructured sulfated zirconia with tetragonal crystalline phase; (3) strongly acidic and hydrothermally stable mesoporous aluminosilicates synthesized in alkaline media; (4) strongly acidic and hydrothermally stable mesoporous aluminosilicates synthesized in strongly acidic media; (5) hydrothermally stable mesoporous titanosilicates with catalytically active titanium species in oxidations; (6) high-temperature generalized synthesis of ultrastable ordered mesoporous silica-based materials by using fluorocarbonhydrocarbon surfactant mixtures.     

基于等温吸附的水泥基孔隙材料水分传输过程

讨论了水泥基孔隙材料水分传输的主要机理,建立了孔隙水分传输的多相和简化模型。测试了胶凝材料含有70%矿渣的净浆和砂浆材料的等温吸附与脱附曲线(WVSI),得到了孔隙材料的水分特征曲线。利用水分传输模型对等温吸附实验脱附过程的实验数据进行回归,得到材料的本征渗透率。结果表明:在相对湿度h=60%时,两个模型的回归结果相近;在相对湿度h=18%时,两个模型的回归结果相差较大;简化模型仅适用于中等湿度(h=60%)及以上环境中水分传输过程的描述;基于等温吸附曲线数据,利用模型回归水泥基材料本征渗透率的方法基本可行。