Drying Of Biological Materials Research Articles

Swell Drying: Coupling Instant Controlled Pressure Drop DIC to Standard Convection Drying Processes to Intensify Transfer Phenomena and Improve Quality—An Overview

Increasing globalization is driving agricultural production in developing countries toward better recovery levels and high additional value. A great opportunity is thus offered to emerging economies. By adopting appropriate and improved methods that allow better preservation, transport, and storage and that conform to the rigorous requirements and standards of organoleptic and nutritional quality as well as stringent hygienic criteria, emerging economies can derive significant benefits. Drying of biological materials usually results in shrinkage. The impact of shrinkage is often highly prejudicial for both the function and use of these materials. On the one hand, shrinkage results in a sharp decrease in water diffusivity through the porous structure (for dehydration and rehydration processes). On the other hand, the compact structure of dried biological material is usually unsuitable in terms of organoleptic quality and is inadequate for grinding. Thus, it is becoming very important to include retexturing and structure-expanding processes in standard drying processes. To this end, the instant controlled pressure drop (DIC) technology has been proposed and successfully tested as a texturing process for partially dried materials, which should normally intensify the whole operation. The quality of the final product as well as the performance of the drying process can also be dramatically improved. Finally, for a large category of dried fruits and vegetables, and even freeze-dried materials, microbiological contamination and the presence of insects and larvae are serious problems. DIC technology can be used as an ultra-high-temperature treatment for a controlled decontamination. Such dried, expanded, and completely decontaminated products can be used as highly nutritional snacks. They can easily be ground to produce expanded granulated powders with excellent sensory, nutritional, functional, and textural properties.

Convective Drying in Combination with Microwave and IR Drying for Biological Materials

The main aim of this article is to find an optimal method for drying of biological materials. Eight schedules of combined (hybrid) drying processes were carried out experimentally with the use of different techniques like convective, microwave, and infrared radiation. The drying time and the quality of dried products were the points of interest. Beetroot (Beta vulgaris) was used as the experimental material. The kinetic curves of drying for the beetroot samples were determined and the dried samples were photographed for visual assessment of the sample quality. Based on the result, attempts were made to suggest suitable drying methods for the application of biological materials in terms of drying time and product quality.

Enthalpy-Driven Optimization of Intermittent Drying

Several optimization problems pertinent to intermittent drying of biological materials were analyzed and a tool to resolve each optimization problem was developed. As the product quality is related to the particularities of the thermal treatment, an average enthalpy gain of the product weighted by the maximum enthalpy gain was considered as the objective function to be minimized. A diffusion model was used to estimate the objective function, and process simulations were performed for batch drying of grains in the rotating jet spouted bed. The results show that the optimization of intermittent drying improves considerably the energy performance of such a drying process. Moreover, it offers better product quality due to lower enthalpy gain.

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.

Application of Electrical Fields in Dewatering and Drying

AbstractThe application of electrical fields to dewatering and drying is reviewed. In particular, the developments in electroosmotic dewatering (EOD) of colloidal slurries are discussed in terms of fundamental associated phenomena, as well as the methods of enhancement of EOD. The electrohydrodynamic (EHD) drying of biological materials are discussed in terms of its fundamentals, current status, and advantages and disadvantages. The potential applications of this emerging technique are evaluated along with a discussion of R&D needs in these areas.

Drying of biological materials in a spout-fluid bed with a draft tube

The possibility of applying a spout-fluid bed with a draft tube and conical bottom was investigated for drying fluid media with a certain content of suspended material was investigated. The major goal who to study the drying of biological materials and products of food the industry. Experimental results concerning the fluidmechanical characteristics of a spout-fluid bed with a centrally situated draft tube and the drying characteristics were obtained on a pilot scale unit, 0.250 m in diameter, with a toed consisting of polyethylene particles 3.6 mm mean diameter and 940 kg/m3 density. Within the regime of the fluid mechanical stability, the system could be used for drying biological suspensions with satisfactory results.

Quantitation of water absorption, swelling, and drying of biological materials. Soaking of rice and soaking and drying of wood

The structural diffusion resistance of wood was higher than that of rice. The rate constants were higher in rice than in wood, bu the diffusion coefficients were higher in wood. Brown rice had musch lower rate constants and diffusion coefficients than polished rice. Activation energies and enthalpies were also determined. The determination of the kinetic constants by this method from the time curves was simple and accurate and had several advantages when compared with infinite series of the integrated Fick's equation

Rapid homogenisation and drying of biological materials

A description of a small apparatus constructed for homogenisation and drying of biological materials is given. Preliminary investigations were carried out for the determination of differences at drying.

Advances in Freeze - Drying Employing Thermoelectric Cooling

Two techniques have been developed in an attempt to eliminate the effect of surface tension forces during the drying of biological materials; namely, the critical point method of Anderson, and the freeze dry procedure of Williams. More recently, a procedure employing thermoelectric cooling was developed in this laboratory. This technique has now received further attention and development.Out present thermoelectric cooling unit* consists of four ceramic insulated modules connected in cascade, having 62, 31, 3, and 3 thermocouples, respectively (Fig. 1 ). The base stage is welded to a heat sink consisting of a copper block (2 1/2″ × 2″ × 1″), through which serpentines a 1/4″ wide channel, the thickness of the block, and which is connected by two threaded tubes to the base of the evaporating chamber (Fig. 2).

Freezing and Drying of Biological Materials

Freezing and Drying of Biological Materials

The use of dielectric heating in the drying of biological materials from the frozen state

The rate of vacuum drying of biological materials from the frozen state may be extremely slow due to the lowering of the vapor pressure which results from evaporative cooling. Present means of supplying heat involve the danger of localized damage due to overheating at the surface. This can be avoided by the use of radio frequency (1000 Mc/s) energy from a radar generator. These wavelengths are not absorbed by dry proteins and thus the dielectric heating occurs only in that part of the material still containing water. Microscopic examination of tissues dried in this way revealed no evidence of localized overheating or other changes due to exposure to radio energy. In operation, a small antenna is placed next to the sample holder and the temperature, as indicated by a thermocouple in the material, is controlled by adjusting the power to the radar generator. The amount of power needed to produce a given amount of heating is a function of the rate at which water vapor can escape from the material as well as the dielectric properties of the material itself. When all water has been removed, no further heating can be produced.

A Simple and Inexpensive Apparatus for the Desiccation of Biological Materials from the Frozen State

Summary A simple and inexpensive apparatus is described for using chemical desiccants in the drying of biological materials from the frozen state.