Effect of Drying Process Parameters on Dehydrated Cabbage Enriched with Selenium

Cabbage (Brassica oleracea var. capitata L.) enriched with selenium through foliar spraying was used to study the effect of drying process on its selenium retention and other quality criteria. Parameters such as blanching, seasoning, temperature, pH, and time of treatment were studied and evaluated to obtain an optimal processing condition for dehydrated selenium-enriched cabbage. After blanching, the barrier for mass and heat transfer of cabbage cellular materials became lower so that the heat damage was high. Blanching parameters set at 95°C and 60 s retained selenium and vitamin C in cabbage best as well as inactivated enzymes present in cabbage. Seasoning reduced the water activity of cabbage and subsequently reduced the loss of selenium. Blanching and seasoning could prevent browning deterioration of cabbage and reasonably kept the fresh color. The selenium loss kinetics during drying obeyed the first-order reaction and its activation energy was 44.0 kJ mol^?1.     

Effect of Drying Conditions and Level of Condensed Distillers Solubles on Protein Quality of Wheat Distillers Dried Grain with Solubles

Reduced protein quality is one of the concerns currently confronting the supply and utilization of wheat distillers dried grain with solubles (DDGS) as an animal feed ingredient. This study assessed the protein quality of wheat DDGS, expressed as acid detergent insoluble crude protein (ADICP) and lysine content, by blending wet distillers grain (WDG) with varying condensed distillers solubles (CDS) levels and drying using forced air convection, microwave, and microwave–convection methods. As the CDS level was increased, the protein content of wheat DDGS generated from the three drying methods increased. Interactions of CDS level with drying air temperature, microwave power, and microwave–convection settings had a significant effect (p < 0.05) on average ADICP and lysine contents. Higher ADICP and lower lysine contents were observed in samples dried at higher temperature, microwave power, and microwave convection settings. Further, the CDS level significantly affected the color parameters of microwave- and microwave–convection-dried samples and the drying air temperature–CDS level interaction significantly affected the color of forced air convection–dried samples. Significant lysine content–redness, ADICP–lightness color parameter, and ADICP–total color difference correlations were found in forced air convection–, microwave-, and microwave–convection-dried samples, respectively. Microwave and microwave–convection drying achieved desirable protein quality associated with low-temperature drying at much shorter times.     

Moisture Diffusion Coefficients for Modeling the First and Second Drying Sections of Green Bricks

A model has been developed that describes the dependence of the moisture diffusion coefficient on the water fraction. Until the end of shrinkage has been achieved, the moisture diffusion coefficient is proportional to the second power of the water fraction. Due to shrinkage, the relevant capillary spaces available for water transport become smaller. Consequently, the moisture diffusion coefficient decreases continually. After the end of shrinkage, the flow resistance to the water moving toward the surface increases sharply due to penetrating air. This leads to a steep drop of the moisture diffusion coefficient by several powers of ten. Measurements were carried out with specimens of defined geometry to determine the moisture diffusion coefficient. On the basis of a specified limiting value, the model is capable of calculating the moisture diffusion for all initially specified raw materials moistures. The moisture can also be determined if the degree of drying shrinkage is known. Using the determined moisture diffusion coefficient, the first and the second drying section can be located. Drying tests were carried out in a laboratory dryer and the experimental results obtained were compared to the simulation results. The simulation results are in good agreement with the experimental results.     

Modeling Intermittent Drying of Wood under Rapidly Varying Temperature and Humidity Conditions with the Lumped Reaction Engineering Approach (L-REA)

For improving product quality and minimizing energy consumption during drying, intermittent drying is often recommended. The mathematical models that are used to describe intermittent drying are usually transport phenomena based, complex models. In this study, the lumped reaction engineering approach (L-REA) is implemented to model wood drying under rapid periodically changed drying air temperature and humidity with high number of cycles of intermittency. The equilibrium activation energy (ΔE _v,b ), an important parameter for REA approach, is evaluated according to the corresponding drying air temperature and humidity in each drying section. The results of modeling suggest the L-REA works well with the experimental data. The simplicity of the L-REA is obvious and is hoped to be used in an industrial setting more readily. The L-REA can be used for sustainable processing in industries to assist in energy audit and management.     

Microwave-Vacuum Drying Kinetics of Pharmaceutical Powders

Abstract

The drying kinetics (maximum drying rate, drying constants) and center temperature of selected powder (aspirin, paracetamol, lactose, and maize starch)–solvent (water, ethanol, methanol, and acetone) systems were monitored during microwave-vacuum drying. An experimental microwave-vacuum system (650 W and 2.45 GHz) operated at 61–81 kPa was used. The drying rate profile did not vary with the powder–solvent system; an initial warming-up period was followed by a constant-rate stage and two falling-rate periods. However, the drying kinetics were found to be both powder and solvent dependent, with the drying times for acetone-, ethanol-, and methanol-wetted materials being considerably shorter (up to 89.8%) than those of samples containing water. Although the general form of the temperature profile (short warming-up period, constant-rate stage, and decreasing temperature phase) was similar for all systems, the maximum temperatures varied quite significantly with solvent type, ranging from highest to lowest in the order water-ethanol-methanol-acetone. For most powder–solvent systems, reduced operating pressure facilitated increased drying rates and thus shorter drying times.     

EFFECT OF EDTA ON COLOR DURING OSMOTIC DEHYDRATION OF BANANA SLICES

ABSTRACT

Five conditions of the osmo-dehydration process of banana slices, which in our previous study underwent the most adequate color parameters changes were used with the presence of EDTA added to the syrup solutions at five concentrations of 0.01, 0.05, 0.1, 0.5 and 1% w/w. EDTA presence did not change the tendency of polyphenol activity decrease during osmotic drying as well as has not effect on chroma, hue and total color difference changes. EDTA presence had an effect on L value decrease in the inner and outer part of the slice, and did not depend to osmotic dehydration conditions. It is highly recommended to use EDTA during osmotic dehydration of some fruits that would undergo undesirable darkening.     

A Method to Measure Emissions from Dryers with Diffuse Leakages,Using Evaporated Water as a Tracer

Abstract

This paper describes a novel method to measure emission from dryers. The method resolves the known difficulties caused by diffuse emissions, and also solves the problems associated with high moisture content of the drying medium. The basic idea is to use water vapor to determine the exhaust flow, while a dry ice trap is used both to preconcentrate emitted VOCs and to determine the moisture content of the drying medium.     

DRYING R D IN THE F.R. GERMANY

This paper summarizes the developments in the field of drying within the Federal Republic of Germany. The main areas on the scientific side (software) as well as those on the manufacturing'side (hardware) are discussed. This survey covers the period, 1976-1986.

On the theoretical side, research and development activities have focussed on convective and contact drying, modelling of contact dryers, selective drying of products with solvents, drying of mixtures and relevant topics in the field of ad-and desorption. On the hardware side, design to fit a changing framework (environment, energy, legislation, etc.), integration of up-and downstream equipment, detail improvements and new types of dryers (as well as applications of otherwise known equipment to drying) have been the major developments. A list of West German manufacturers of drying equipment is also in-cluded as an Appendix.