Sun Drying of Sultana Grapes

ABSTRACT

In this paper, an experimental investigation is presented on natural sun drying of Sulruna grapes. in drying experiments, a new pretreatment solution was employed to decrease the drying time and to obtain better quality products. In addition to this solution, grape drying experiments in the pretreated form with potasa solution -the most common mixture in Turkey for grape drying- and in the untreated form were carried out. The measurements of weight loss and dry matter (and brix) during drying experiments, and the color, pH and total acidity measurements at the end of drying experiments were carried out. The results show that the total drying period for grapes pretreated with the present solution was 128 hr while the drying periods for the cases, e.g., pretreated with potasa solution and untreated were 176 hr and 436 hr. This means that the drying rate for pretreated grapes with the present solution was 1.375 times faster than the pretreated case with potwa and 3.4 times faster than the untreated case. In light of the results obtained here. it is clear that the present solution is a very good alternative for grape drying applications and will be beneficial to the relevant industry and people.     

Sun Drying of Sultana Grapes

In this paper, an experimental investigation is presented on natural sun drying of Sulruna grapes. in drying experiments, a new pretreatment solution was employed to decrease the drying time and to obtain better quality products. In addition to this solution, grape drying experiments in the pretreated form with potasa solution -the most common mixture in Turkey for grape drying- and in the untreated form were carried out. The measurements of weight loss and dry matter (and brix) during drying experiments, and the color, pH and total acidity measurements at the end of drying experiments were carried out. The results show that the total drying period for grapes pretreated with the present solution was 128 hr while the drying periods for the cases, e.g., pretreated with potasa solution and untreated were 176 hr and 436 hr. This means that the drying rate for pretreated grapes with the present solution was 1.375 times faster than the pretreated case with potwa and 3.4 times faster than the untreated case. In light of the results obtained here. it is clear that the present solution is a very good alternative for grape drying applications and will be beneficial to the relevant industry and people.     

A Sharp Drying Front Model

The drying of materials is often described by nonlinear diffusion equations. Up to now the only way to solve these equations is by numerical simulations. Recently an analytic solution has been proposed for the drying problem. Based on this solution a sharp drying front model is presented. Measured moisture profiles during drying and the drying curve of gypsum are compared with approximate models.     

A Sharp Drying Front Model

Abstract

The drying of materials is often described by nonlinear diffusion equations. Up to now the only way to solve these equations is by numerical simulations. Recently an analytic solution has been proposed for the drying problem. Based on this solution a sharp drying front model is presented. Measured moisture profiles during drying and the drying curve of gypsum are compared with approximate models.     

Effects of Surface Concentration on Drying Behavior of Carbohydrate Solutions

As the surface properties of the drying materials are very important not only for the drying rate but also for the quality change during drying, the effects of surface concentration on the drying behavior of liquid foods (sugar solutions) were investigated by isothermal drying experiments and by numerical calculation experiments. The isothermal drying experiments with gelled sugar solution systems (sucrose and maltodextrin) were carried out at various relative humidity (RH) values (RH = 0 to 84%). Separate experiments were carried out for determination of the desorption isotherms.

The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.

When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased.     

Effects of Surface Concentration on Drying Behavior of Carbohydrate Solutions

ABSTRACT

As the surface properties of the drying materials are very important not only for the drying rate but also for the quality change during drying, the effects of surface concentration on the drying behavior of liquid foods (sugar solutions) were investigated by isothermal drying experiments and by numerical calculation experiments. The isothermal drying experiments with gelled sugar solution systems (sucrose and maltodextrin) were carried out at various relative humidity (RH) values (RH = 0 to 84%). Separate experiments were carried out for determination of the desorption isotherms.

The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.

When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased.     

Determination of the moisture diffusivity coefficient and mathematical modeling of drying

Drying plays an important role in the production of clay tiles. In the present article, drying process is analyzed taking experimental data for several masonry clays obtained from different clay tile manufacturers and published data for different clay slabs. Calculation methods and computer programs designed for the calculation of the effective diffusion coefficient are developed. The first calculation method represents the analytical solution of the Crank equation, while the second one represents the analytical solution of the Efremov equation with boundary conditions in the form of the flux. Unlike other materials, clay tiles exhibit shrinkage during the drying process. For this reason, a shrinkage correction is included in both calculation methods. Four models (A1, A2, B1 and B2) for predicting the drying behavior are obtained as the result of the calculation cited programs. It is shown that the calculated effective diffusion coefficient determined by the designed computer programs, using experimentally obtained and selected published data sets have similar values to those of the same coefficient reported in the literature. Based on the mathematically determined prognostic values of the effective diffusion coefficient, it was concluded that there is more than 90% agreement between the experimentally recorded and the calculated drying curves.     

Mechanisms of Drylng of Skin-Forming Materials; the Significance of Skin Formation and a Comparison Between Three Types of Material

Comparisons are drawn between the drying characteristics, and the mechanisms of skin formation on, three characteristic types of material. The significance of skin formation, which may be a major factor in valatiles retention in the drying of spray dried products, is discussed. The optimum drying conditions to achieve the highest volatiles retention for each type of skin-forming material are predicted. General comparisons are also drawn between the drvine of skin-formine i.e., materials which form a smooth flexible low- parosity skin at same slage, and normal crust-forming materials. The latter form only a rigid crust with a porosity which is system and drying-condition dependent.     

Influence of pore structure and impregnation–drying conditions on the solid distribution in porous support materials

Deposition of solids within porous materials from a drying solution is an important phenomenon in numerous natural and industrial processes. A profound knowledge about influences of different parameters on the solid distribution in the material is required for an effective targeted impregnation process. Experimental investigations and simulations are used to study the influence of pore structure, drying conditions, and solute concentration on the solid distribution in porous support materials after impregnation and drying. It is found that low drying rates lead to strong solid accumulation at the material surface, whereas high drying rates reduce the solute transport to the surface and result in more uniform solid distributions. A small pore diameter and distribution width reduce solute migration during drying and lead to uniform solid distributions without being influenced by the drying conditions. A higher initial concentration of the impregnation solution causes pronounced surface accumulation, while low initial solute concentrations result in more uniform distributions. Fundamental effects during drying are captured in an existing pore network model by adaption of experimental pore structures and impregnation–drying conditions, resulting in a good general agreement of experiments with simulations.     

Small Capacity Mobile Dryers for Drying Biological Materials

Creation of the universal technology and solution for drying of biological materials is almost impossible since various materials are concerned and various parts of plants are dried (root, stem, flower, bloom, seed, and fruit). Three original designs of devices for drying of biological materials have been developed. First, there are two types of mobile solar dryers for drying various biological materials by direct and combined use of solar energy, a design with the direct use of solar energy, solar air collector, and photovoltage system, and a design with combined use of solar energy, solar air collector, and wind motor. The procedure for dimensioning some basic elements of the dryer has been presented, and the analysis is given showing how the parameters of materials being dried, the collector construction, and climatic, and weather conditions influence the efficiency of the collector active surface. Having considered the advantages of radiation drying as well as the reasons for its limited application, a design concept of a mobile radiation dryer for drying biological materials at atmospheric pressure is given. Furthermore, optimization of operation modes and construction parameters of the proposed mobile dryer design is provided, with respect to the analysis showing how radiation source and characteristics of material being dried influence the drying rate and dried material quality.     

Dynamics of drying of textile materials after treatment with foam solutions

The drying curves for fabric and base treated with warp-sizing foam were experimentally obtained and their features were discussed. The transfer functions corresponding to transients and reflecting the dynamics of drying of materials treated with foam in numerical form were determined.     

Controlled freezing and freeze drying: a versatile route for porous and micro‐/nano‐structured materials

Freeze drying is a process whereby solutions are frozen in a cold bath and then the frozen solvents are removed via sublimation under vacuum, leading to formation of porous structures. Pore size, pore volume and pore morphology are dependent on variables such as freeze temperature, solution concentration, nature of solvent and solute, and the control of the freeze direction. Aqueous solutions, organic solutions, colloidal suspensions, and supercritical CO₂ solutions have been investigated to produce a wide range of porous and particulate structures. Emulsions have recently been employed in the freeze drying process, which can exert a systematic control on pore morphology and pore volume and can also lead to the preparation of organic micro‐ and nano‐particles. Spray freezing and directional freezing have been developed to form porous particles and aligned porous materials. This review describes the principles, latest progress and applications of materials prepared by controlled freezing and freeze drying. First of all the basics of freeze drying and the theory of freezing are discussed. Then the materials fabricated by controlled freezing and freeze drying are reviewed based on their morphologies: porous structures, microwires and nanowires, and microparticles and nanoparticles. The review concludes with new developments in this area and a brief look into the future. Copyright © 2010 Society of Chemical Industry     

Encapsulation Efficiency of Food Flavours and Oils during Spray Drying

Microencapsulation is a rapidly expanding technology which is a unique way to package materials in the form of micro- and nano-particles, and has been well developed and accepted within the pharmaceutical, chemical, food and many other industries. Spray drying is the most commonly used encapsulation technique for food products. A successful spray drying encapsulation relies on achieving high retention of the core materials especially volatiles and minimum amounts of the surface oil on the powder particles for both volatiles and non-volatiles during the process and storage. The properties of wall and core materials and the prepared emulsion along with the drying process conditions will influence the efficiency and retention of core compounds. This review highlights the new developments in spray drying microencapsulation of food oils and flavours with an emphasis on the encapsulation efficiency during the process and different factors which can affect the efficiency of spray drying encapsulation.     

Freeze‐drying of aqueous solution frozen with prebuilt pores

To save drying time and increase productivity, a novel idea was proposed for freeze‐drying of liquid materials by creating an initially unsaturated frozen structure. An experimental investigation was carried out aiming at verifying the idea using a multifunctional freeze‐drying apparatus. Mannitol was selected as the primary solute in aqueous solution. Liquid nitrogen ice‐cream making method was used to prepare the frozen materials with different initial porosities. Results show that freeze‐drying can be significantly enhanced with the initially unsaturated frozen material, and substantial drying time can be saved compared with conventional freeze‐drying of the initially saturated one. Drying time was found to decrease with the decrease in the initial saturation. The drying time for the initially unsaturated frozen sample (S₀ = 0.28 or 0.69 of initial porosity) can be at best 32% shorter than that required for the saturated one (S₀ = 1.00 or zero porosity). This unique technique is easy to implement and improves the freeze‐drying performance of liquid materials. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2048–2057, 2015     

Mechanisms of Drylng of Skin-Forming Materials; the Significance of Skin Formation and a Comparison Between Three Types of Material

ABSTRACT

Comparisons are drawn between the drying characteristics, and the mechanisms of skin formation on, three characteristic types of material. The significance of skin formation, which may be a major factor in valatiles retention in the drying of spray dried products, is discussed. The optimum drying conditions to achieve the highest volatiles retention for each type of skin-forming material are predicted. General comparisons are also drawn between the drvine of skin-formine i.e., materials which form a smooth flexible low- parosity skin at same slage, and normal crust-forming materials. The latter form only a rigid crust with a porosity which is system and drying-condition dependent.     

INFLUENCE OF THE DRYING MEDIUM PARAMETERS ON DRYING INDUCED STRESSES

A thermomechanical model of drying of capillary-porous materials whose material constants depend on moisture content and temperature is presented in the paper. The finite element method is used for the solution of two-dimensional problem of convective drying of a prismatic bar. The moisture distributions, temperature distributions, drying induced strains and stresses for various drying medium parameters are determined. The effect of these parameters on moisture distribution and in particular on drying induced stresses is discussed.     

On the Analysis of Drying Process

Drying plays an important role in processing agricultural grains/seeds, chemicals, and other materials. In the present work, drying process has been analyzed taking published data on different grains and seeds such as rapeseed, sunflower, soybean, corn, paddy, and wheat. Mathematical expressions have been established for important drying parameters such as critical moisture content, drying rates, time required to reach critical moisture content, total drying time, and diffusivity as function of drying air temperature. The expressions involve a coefficient parameter and an exponential function of drying air temperature, Aexp(- E/RT_g),and interestingly it is shown that the same functional form with same Es can correlate the different relevant drying parameters. The coefficient parameters As and Es are decided by drying materials and drying process, and the values have been derived for different grains/seeds. The correlations are useful in analyzing the drying process.     

贝壳粉负载TiO2对玫红酸的光降解催化反应

选择天然贝壳,经清洗、干燥、灼烧、研磨和过筛,制的天然贝壳粉.以TiCl<,4>溶液浸渍,经水解、过滤、清洗、干燥和灼烧,制的载有TiO<,2>的贝壳粉材料.以此种材料为催化剂,考察其对有色的玫红酸分解作用.对比实验表明,载有TiO<,2>的贝壳粉材料,对玫红酸有明显的降解作用.     

INFLUENCE OF THE DRYING MEDIUM PARAMETERS ON DRYING INDUCED STRESSES

ABSTRACT

A thermomechanical model of drying of capillary-porous materials whose material constants depend on moisture content and temperature is presented in the paper. The finite element method is used for the solution of two-dimensional problem of convective drying of a prismatic bar. The moisture distributions, temperature distributions, drying induced strains and stresses for various drying medium parameters are determined. The effect of these parameters on moisture distribution and in particular on drying induced stresses is discussed.     

A Model for Drying of an Aqueous Lactose Droplet Using the Reaction Engineering Approach

Spray drying is the primary method for manufacturing of food powders from liquids. Optimal design and optimization of spray drying operations at the fundamental level require both modeling of the drying characteristics of a single droplet and dryer wide simulations using computational fluid dynamics (CFD). An accurate yet simple model for drying of a single droplet, which does not require solution of partial differential equation, is ideal input for CFD simulations. The reaction engineering approach (REA) is shown to be appropriate in this regard. It has been successfully used for prediction of skim and whole milk droplet drying behavior under various drying conditions. In this study, an aqueous lactose solution was dried in droplet form and the appropriate REA model parameters obtained. The change of diameter of the droplet during drying was measured experimentally and compared with the model results.