SOME THEORETICAL AND EXPERIMENTAL CONSIDERATIONS ON THE THIN-LAYER DRYING OF FISH CRACKERS: PRODUCT EXPANSION ASSESSMENT

ABSTRACT

Fish crackers are semi-prepared starch-based products which must be expanded just prior to consumption. This work aims at the experimental and theoretical study of the thin-layer drying process of fish crackers in a thin disc geometry. The process was carried out in an insulated cabinet dryer and the experimental kinetic drying data were fitted using the analytical solutions resulting from both a drying model governed by the Fick' s second law and a model based on the lumped system, highlighting the adequacy of each of them. Therefore, it was possible to calculate the mass transfer coefficients for seven different blends offish crackers. Also, the effect of the drying time on the bulk density of the puffed product was evaluated for these seven blends. Both the kinetic drying parameters and the optimal bulk density responses were analyzed using the Simplex-Lattice Design over a mixture triangle within a minimal number of experiments.     

EFFECT OF DRYING METHOD ON SHRINKAGE AND POROSITY

The effect of drying method on bulk density, particle density, specific volume and porosity of banana, apple, carrot and potato at various moisture contents was investigated, using a large set of experimental measurements. Samples were dehydrated with five different drying methods: conventional, vacuum, microwave, freeze and osmotic drying. A simple mathematical model was used In order to correlate the above properties with the material moisture content. Four parameters with physical meaning were incorporated in the model: the enclosed water density p_w, the dry solid density p_s, the dry solid bulk density p_bo and the volume shrinkage coefficient β'. The effect of drying method on the examined properties was taken into account through its effect on the corresponding parameters. Only, dry solid bulk density was dependent on both material and drying method. Freeze dried materials developed the highest porosity, whereas the lowest one was obtained using conventional air drying.     

EFFECT OF DRYING METHOD ON SHRINKAGE AND POROSITY

ABSTRACT

The effect of drying method on bulk density, particle density, specific volume and porosity of banana, apple, carrot and potato at various moisture contents was investigated, using a large set of experimental measurements. Samples were dehydrated with five different drying methods: conventional, vacuum, microwave, freeze and osmotic drying. A simple mathematical model was used In order to correlate the above properties with the material moisture content. Four parameters with physical meaning were incorporated in the model: the enclosed water density p_w, the dry solid density p_s, the dry solid bulk density p_bo and the volume shrinkage coefficient β'. The effect of drying method on the examined properties was taken into account through its effect on the corresponding parameters. Only, dry solid bulk density was dependent on both material and drying method. Freeze dried materials developed the highest porosity, whereas the lowest one was obtained using conventional air drying.     

SOME ASPECTS OF MODELLING CONVECTIVE CORN DRYING

Specific heat claim of dewatering at large scale convective corn driers could be reduced to about 3000 kf/kg by means of an accurate modelling of the drying process. The main inadequecy of the models used in these days is the ignorance of change caused by interactions between some process parameters and material features during drying process.

In this study dehydration of seven Pioneer type hybrids was tested at model and large scale driers. By an empirical resolution of specific heat and bulk density functions of shelled corn furthermore by establishing a drying speed equation depending on the main grain- and process-features an appropriate result was provided.     

Determination of porosity change from shrinkage curves during drying of food material

Based on a very simple model of mass conservation, three experimental properties (solid density, liquid density and initial bulk density) and the simultaneous acquisition of the reduced moisture content and the volume shrinkage during drying, a simple method is proposed to calculate the bulk porosity of a material during drying. This model allows a graphical interpretation to visualize the porosity change by comparing the experimental shrinkage curve with an ideal shrinkage curve. In the present work, several examples were taken from the literature to illustrate the application of this method to foodstuffs (apple, banana, carrot, garlic, pear, potato and sweet potato) with two different processes (convective drying, freeze-drying) and different drying conditions. Porosity calculations including error estimations showed a good agreement with experimental values reported in the literature.     

DENSITIES, SHRINKAGE AND POROSITY OF SOME VEGETABLES DURING AIR DRYING

Bulk density, particle density, shrinkage and porosity were experimentally determined at various moisture content during air drying for apple, carrot and potato cubes. A simple mathematical model was used to predict the above properties versus material moisture content. Four parameters were incorporated in the model: enclosed water density, dry solids' density, bulk density of dry solids, and volume-shrinkage coefficient. The model was fitted to experimental data satisfactorily, and the parameters were estimated. The influence of varying drying conditions was also investigated.     

A fractional kinetic model for drying of cement-based porous materials

In this work, we attempt to characterize the drying phenomena of cement-based porous materials (CBPMs) using a fractional kinetic model that is represented by a function for the kinetics of complex systems and characterized by a stretched exponential and/or power-law function with two parameters: the order index n and the fractional time index α. The fractional kinetic model recovers the classic Lewis and Page drying models as well as the pseudo first-order and pseudo second-order adsorption/desorption models with appropriate n and α values and boundary conditions. The fractional kinetic and classic drying models (i.e., the Lewis, Henderson and Pabis, Page, and logarithmic models) were used to interpret the experimental drying data for cement pastes and mortars. Rearrangement of the fractional kinetic correlation generates a linear log ?log plot. The results showed that the values obtained using the fractional kinetic model and Page models were in better agreement with the experimental data than the values obtained using the other selected models. The results may also suggest that drying of CBPMs is more than a diffusion-controlled process.     

SOME ASPECTS OF MODELLING CONVECTIVE CORN DRYING

ABSTRACT

Specific heat claim of dewatering at large scale convective corn driers could be reduced to about 3000 kf/kg by means of an accurate modelling of the drying process. The main inadequecy of the models used in these days is the ignorance of change caused by interactions between some process parameters and material features during drying process.

In this study dehydration of seven Pioneer type hybrids was tested at model and large scale driers. By an empirical resolution of specific heat and bulk density functions of shelled corn furthermore by establishing a drying speed equation depending on the main grain- and process-features an appropriate result was provided.     

DENSITIES,SHRINKAGE AND POROSITY OF SOME VEGETABLES DURING AIR DRYING

Abstract

Bulk density, particle density, shrinkage and porosity were experimentally determined at various moisture content during air drying for apple, carrot and potato cubes. A simple mathematical model was used to predict the above properties versus material moisture content. Four parameters were incorporated in the model: enclosed water density, dry solids' density, bulk density of dry solids, and volume-shrinkage coefficient. The model was fitted to experimental data satisfactorily, and the parameters were estimated. The influence of varying drying conditions was also investigated.     

Non-isothermal modeling of drying kinetics of ceramic tiles

The present study has been undertaken to optimize the drying stage in ceramic tile manufacture. Tests were conducted to determine drying kinetics, establishing how air temperature and relative humidity influenced this process. Tests show that surface moisture content does not evolve as might be expected on the basis of the simple assumption that the surface dries immediately and reaches equilibrium moisture content. A non-isothermal model was proposed to model drying curves successfully. The influence of drying temperature, bulk density of the shaped material, and tile thickness on the drying process and the parameters of the model was obtained.     

DRYING OF BIOACTIVE PRODUCTS: INACTIVATION KINETICS

A comprehensive experimental study of the drying of enzymes (E) and gin seng (GS) biomateriaJs provides a basis for mathematical modelling of the drying process with respect to the inactivation kinetics. Temperature of 20 - 120 °C was established for a number of enzymes while removing moisture with no thermal destruction. The kinetic parameters of inactivation were obtained for dry and wet enzymes and gin seng biomatenals. The software for kinetic parameters calculations for drying and inactivation of enzymes and gin seng biomateriaJs was drawn up, tested and verified experimentally. Methods of drying, design of dryers and regimes of drying of pure enzymes and gin seng biomaterials with minimum loss of bioactivity are suggested on the basis of model analysis and experimental data.     

褐煤等温干燥过程及动力学研究

为研究褐煤干燥过程,利用煤质水分分析仪和微分热重分析方法,对不同粒级的褐煤在不同干燥温度下进行等温干燥试验,得到了样品含水率与干燥时间、干燥速率与含水率的关系曲线。通过粒级分布系数对褐煤进行含水率折算,并用不同干燥模型对试验数据进行拟合,得到了在介质温度140℃下3个干燥阶段的干燥方程及干燥动力学参数。结果表明,引入粒级分布系数得到的干燥速率特征常数k值,与不同粒级的干燥速率特征常数k的均值相近。根据褐煤的干燥速率和水分的存在形式,将褐煤干燥过程分为3个干燥阶段,分析得出干燥方程模型分别用线性干燥模型、Wang经验模型、Page模型较为合理。根据Arrhenius经验公式建立了ln k与1/T的关系,得到褐煤干燥的界面蒸发活化能Ea=17.088 k J/mol,指前因子A=12.47 min~(-1)。     

FITTING CASSAVA DRYING KINETIC WITH A HIGH ORDER EQUATION

The experimental drying curves with air flow rates of cassava parallelepipeds were analyzed at different and thickneses to obtain an empirical model for the cassava drying kinetics. Experimental results were modeled with first and higher order kinetic models. The kinetic parameters were fitted by non-linear regression to experimental drying curves with a power law model. The parameters of the power law model were statistically significant in a non-lineal joint interval confidence of 99%. The effect of temperature, air velocity and sample thickness on drying kinetic results, showed a consistent behavior with respect to drying theory.     

F-T合成蜡油加氢裂化五集总反应动力学模型

根据F-T合成蜡油加氢裂化过程的机理及已有的九集总和全集总动力学模型,提出了异构化因子的概念;将异构化反应模拟与实验结果相结合,引入裂化概率函数改进原有九集总动力学模型;据此建立了包含7个反应式的更加符合实际加氢裂化过程的五集总动力学模型。通过已有的实验结果同两种动力学模型的比较,表明所建立的五集总动力学模型计算值与实验值的平均相对误差为3.95%,在高转化率的情况下,平均相对误差仅为0.88%,且该模型对产品选择性也具有良好的预测能力。     

DRYING OF BIOACTIVE PRODUCTS: INACTIVATION KINETICS

ABSTRACT

A comprehensive experimental study of the drying of enzymes (E) and gin seng (GS) biomateriaJs provides a basis for mathematical modelling of the drying process with respect to the inactivation kinetics. Temperature of 20 - 120 °C was established for a number of enzymes while removing moisture with no thermal destruction. The kinetic parameters of inactivation were obtained for dry and wet enzymes and gin seng biomatenals. The software for kinetic parameters calculations for drying and inactivation of enzymes and gin seng biomateriaJs was drawn up, tested and verified experimentally. Methods of drying, design of dryers and regimes of drying of pure enzymes and gin seng biomaterials with minimum loss of bioactivity are suggested on the basis of model analysis and experimental data.     

Drying of bulk silica gels molded from tetraethylorthosilicate and aerosil

The physicochemical specifics of the process of drying of bulk silica gel molded from mixed sols (tethracthylsilicate hydrolyzate: aerosil) are considered. The results of the experimental studies of kinetic drying curves of bulk-formed silica gels depending on the process conditions and modes are presented. Translated from Steklo i Keramika, No. 5, pp. 11–14, May, 2000.     

Towards optimization of the osmotic drying process of alumina-gelatin objects: Regression analysis and verification

In this study, further analysis of the osmotic drying process was conducted to identify the optimum combination of parameters for drying rectangular alumina-gelatin beams. This study was designed to determine the effect of three variables related to the osmotic drying process (osmotic pressure, molecular weight, and immersion time) on the interaction between the liquid desiccant and the submerged alumina-gelatin samples. The water loss from the alumina-gelatin samples was positively correlated with the molecular weight, osmotic pressure, and immersion time. Up to 40% by weight of the initial water content was removed during the osmotic drying process. The samples also experienced solids gain due to the counterflow of solute from the liquid desiccant. The least amount of solids gain resulted from drying for the shortest immersion time at low osmotic pressure and high molecular weight. Evidence of possible interactions between variables was noted for the sintered density metric. Statistical methods were used to form regression equations for the measured responses (water loss, solids gain, bulk density). A verification experiment was conducted to compare the experimental outcomes to the predicted outcomes. The responses were simultaneously optimized to identify the combination of variable settings required to meet specified goals. In order to maximize water loss, minimize solids gain, and maximize bulk density, the ceramic-gelatin object should be immersed for approximately 60?min in an aqueous solution of 100,000?g/mol poly(ethylene oxide) at an osmotic pressure of 2.50?MPa. These values are valid for the range of parameter settings tested and the sample fabrication and drying methods used.     

Two-stage method of obtaining high bulk density sodium tripolyphosphate: Design and mechanism of process

The paper presents a two-step method for obtaining sodium tripolyphosphate (STPP) with a bulk density of about 0.90 kg/dm³ after the first step, using sodium phosphates after spray drying and water as the raw materials. STPP with a bulk density of 0.95–1.00 kg/dm³ was generated in the second stage, using STPP from the first step and water as the raw materials. The paper presents statistical analyses to define the process parameters which significantly affect sodium tripolyphosphate bulk density. The determination of the profile approximation and utility function enabled the optimization of process parameters for obtaining a product with a bulk density of 0.95–1.00 kg/dm³. Mechanisms of increasing bulk density was indicated by studies on the microstructure of the product and phase transformation during the process. The data were empirically verified and satisfactory results were found.     

Impact of agitated drying on the powder properties of an active pharmaceutical ingredient

In this study, the impact of agitated drying on the physical and bulk powder properties of an active pharmaceutical ingredient (API) is presented. The effects of different agitated drying conditions such as agitation rate, drying temperature, drying time pre-agitation, drying time during agitation and number of solvent wash cycles on the bulk density, millability, flow and specific surface area is reported. The crystal morphology is altered from fibrous needles to agglomerates when switching from tray to agitated drying. An increase in bulk density and specific surface area was evident when using agitated drying compared to tray drying as hard coarse granules were produced with an increase in the number of fine particles < 10 μm. The bulk density was found to increase with an increase in agitation speed, drying time and number of solvent wash cycles used during filtration. Controlling both fine and coarse particle size of the granules for this API during agitated drying was difficult to achieve due to the fibrous crystal habit. However, the increase in the bulk density observed has the potential to facilitate improvements in the ease of drug product development. In the case of this system further particle size control was required through the use of dry milling.     

Effect of sample size on solvent extraction for detecting cocontinuity in polymer blends

The effect of sample size on the results of solvent extraction measurements for detecting cocontinuity in polymer blends was investigated. Poly(ethylene oxide)/polystyrene (PEO/PS) blend samples of several thicknesses were analyzed by removing the PEO phase using water extraction. The experimental degree of continuity was shown to have a linear dependence on the reciprocal of sample thickness. A model is proposed to explain this dependence and to allow the bulk or true degree of continuity to be determined. Measurement of the bulk degree of continuity is useful for understanding properties of cocontinuous polymer blends such as electrical conductivity, impact strength, or tensile strength.