The objective of this study was to examine the effects of the FLUIDIZED-BED DRYING method on the final quality of two varieties of Iranian rice, medium- and long grain. The results were compared to that of paddy DRYING using a traditional method. Rough rice was treated in the FLUIDIZED BED drier at 140°C for 2 minutes. Similar samples were dried for 8-10 hrs by the traditional method. Dried samples were dehusked and polished. Quality factors, including trade quality (head rice yield percent and whiteness), cooking quality (amylose content, gelatinization temperature, gel consistency, aroma and flavor) and nutritional quality (thiamine and lysine contents), were then measured for each sample. Finally, the data was analyzed. Results show that paddy DRYING in a FLUIDIZED BED dryer would reduce the quality factors except for rice whiteness for which conventional DRYING is more acceptable. Therefore modification of FLUIDIZED-BED DRYING technique is recommended.

Modeling of DRYING kinetics of canola was studied at 30 to 100oC in a Lab scale FLUIDIZED BED dryer. DRYING rate of the crop was assessed, using many conventional moisture ratio models employed in food science. Effective Diffusivity coefficient (Deff) and activation Energy (Ea) of kernel moisture were determined using Fick's Law of Diffusion and Arrhenius Equation. Besides, the effects of temperature changes on DRYING time were modeled through, regression method. Results indicated that static pressure dropped from 596 to 583 Pa when kernels starting to fluidize. In fluidizing state, canola DRYING time becomes reduced by 74% through an increase of temperature from 30 to 100oC. In comparison with the other models, Approximate Diffusion model and two term Exponential model are in good agreement with the experimental data respectively with high R2 and low c2 as well as RMSE. Also Newton model was of little with the other models. It bears a single coefficient, and is easy and convenient to be used for an estimation of DRYING rate of canola in FLUIDIZED BED dryer. Temperature changes from 30 to 100oC cause Deff to increase from 3.759×10-11 to 8.457×10-11. In this research, Ea of canola moisture was determined as 11.03 kJ/mol. Selected exponential Regression model is in good agreement with the experimental data and suitable for an estimation of DRYING time in temperature range of 30 to 100oC.

AbstractBackground and objectives: Among the various hot air DRYING methods, FLUIDIZED BED DRYING has significant advantages such as high heat and mass transfer, uniform moisture reduction of products with short time and high DRYING rate and uniform process at entire surface of the product due to efficient mixing with the DRYING air and high efficiency of process. In recent years, usage of infrared DRYING to dry food products has increased over conventional DRYING methods due to higher product quality, uniform heat distribution, high energy efficiency, high heat transfer rate and less processing time, facilitating the control of raw material temperature, reduced necessity for air flow across and the high ability to control process parameters in infrared heating. In this study, kinetics of carrot cubes DRYING by infrared-FLUIDIZED BED dryer were investigated.Materials and methods: Fresh carrot were washed with tap water and peeled manually then diced by dicer. To DRYING carrot cubes by combined infrared- FLUIDIZED BED method a laboratory scale dryer was designed and performed. In this study, DRYING of carrot cubes (0.5 and 1 cm3) was performed in factorial design experiments using air temperatures of 50, 60 and 70 °C and three levels of infrared power (200, 400 and 600 W) in three replications. To describing the infrared-FLUIDIZED BED DRYING behavior of carrot cubes, five mathematical models (Page, Modified Page, Henderson & Pabis, Midilli and Logarithmic) were evaluated.Results: The results demonstrated that the change in inlet air temperature, size of carrot cubes and infrared power had a significant effect (P <0.05) on water withdrawal from the sample and DRYING time decreased with increasing air temperature and infrared power and decreasing carrot cubes size. Therefore, the energy consumption was also reduced considerably, decreasing from 12.63 Kwh/kg in BED FLUIDIZED method (without infrared power) to 2.28 Kwh/kg using infrared -FLUIDIZED BED DRYING. The Page model was identified as the suitable model to describe the DRYING kinetics of carrot cubes by infrared-FLUIDIZED BED dryer that showed a good agreement with experimental data.Conclusion: The statistical analysis of variance showed that air temperature, sample size and infrared power had a significant effect on water withdrawal rate of samples and therefore DRYING time. According to the results, using infrared-FLUIDIZED BED DRYING as a combined method in comparison with conventional hot air DRYING methods can reduce DRYING time and energy consumption and costs considerably.Keywords: Infrared, Combined FLUIDIZED BED, DRYING, Kinetics, Carrot

One of the most effective DRYING mechanisms used today is FLUIDIZED BED DRYING. The enhanded DRYING rate in this method is contributed to the fluidization of particles, resulting in an increased contact area and hence an increase in heat and mass transfer rates. The model which is basd on a two-fluid model, provides the velocity, temperature profiles of phases, moisture content and the voidage distribution. One-dimensional finite volume scheme is used for the proposed model and the Simpler Algorithm is utilized for the hydrodynamic of the flow field. The verification of the theoretical results was done by the use of an experimental set up. The results indicate a good agreement between the mathematical model and the experiment.

Several studies have been conducted on equipping conventional FLUIDIZED BED with some technologies to increase DRYING efficiency and its performance. The objective of the study was to investigate the influence of high power ultrasound on FLUIDIZED BED DRYING of corn in terms of DRYING kinetics and quality characteristics of corn in three levels of ultrasound power density (11.1, 14.6 and 18.7 kW m-3), three levels of DRYING air temperature (30, 40, and 50oC) and four levels of frequency (20, 25, 28, and 30 kHz) in which the moisture content reduced from 32±0.5 (%d.b.) to 17±0.5 (%d.b.). Results revealed that the frequency of 25 kHz was the most efficient in terms of DRYING time. The frequency of 25 kHz and power density 14.6 kw m-3 was the most efficient frequency and caused reduction of the DRYING time by 43% in comparison with no ultrasound condition (control). The sponge effect caused by ultrasound application led to reduction of failure strength and toughness of the dried samples. According to the results, toughness compared to the failure strength was an appropriate index of the grain hardness.

DRYING properties of high moisture potato slices with initial moisture content of about 4.06 (db) under thin layer fixed, semi FLUIDIZED and FLUIDIZED BED conditions were studied. DRYING air temperatures of 40, 50, 60 and 70oC were applied in experiments using a laboratory FLUIDIZED BED convective dryer. In order to predict the DRYING behavior of potato slices, seven thin layer DRYING models were applied from where finally Midilliet al. model was selected as the suitable one, based on comparative indices. Effective moisture diffusivity of the potato slices varied between 4.29×10-9 and 15.70×10-9 m2 s-1 for fixed and FLUIDIZED BED conditions, respectively. Moisture diffusivity values of the slices were increased as the DRYING air temperature levels increased. Activation energy values varied between 15.88 and 24.95 kJ mol-1. Minimum and maximum values of activation energy were obtained at minimum FLUIDIZED and fixed BED conditions, respectively. Consumption of specific energy for thin layer DRYING of high moisture potato slices was obtained between 0.45×105 and 1.64×105 (kJ kg-1). Increase in the DRYING air temperature in each BED condition caused increase in energy consumption. The maximum value of energy consumption was obtained at FLUIDIZED BED conditions.

FLUIDIZED BED DRYING method is one of the most important new DRYING methods of agricultural materials. In this study the rough rice DRYING process by fixed and FLUIDIZED methods was compared based on thermal efficiency, DRYING rate and kernel fissuring percent. The experiments were conducted by a laboratory FLUIDIZED BED dryer with ability of the inlet air temperature and airflow rate control to operate in fixed and FLUIDIZED conditions. The rough rice samples were dried from 17.7 initial moisture content to 11% final moisture content (dry basis) at three temperatures of 40, 60 and 80oC. The air velocity in fixed, semi-FLUIDIZED and FLUIDIZED BED conditions was 0.1, 1.1 and 3.5 m/s, respectively. The thermal efficiency of dryer was calculated based on the ratio of thermal energy utilized for evaporating water from the DRYING product to thermal energy supplied to the DRYING air. The maximum and minimum thermal efficiency of 22.84 and 3.3% were belonged to the fixed BED condition at 80oC and the FLUIDIZED BED condition at 40oC, respectively. The fixed BED condition was determined as the main factor influencing kernels fissuring, so that the maximum DRYING time of 280 minutes and the maximum kernel fissuring of 78% were measured in this condition at 80oC. The minimum DRYING time of 40 minutes and the minimum kernel fissuring of 17% were belonged to the semi-FLUIDIZED BED condition at 80 and 40oC, respectively.

In this research the effect of different DRYING conditions of microwave FLUIDIZED BED (inlet air temperature, inlet air velocity and microwave power) on DRYING time, effective moisture diffusivity, shrinkage and total energy consumption of pistachio kernel was studied. Data analysis and optimization of DRYING process of pistachio were conducted by response surface method and central composite design. Input (independent) parameters were: inlet air temperature, inlet air velocity and microwave power. Dependent (output or response) variables were: DRYING time, effective moisture diffusivity, shrinkage and total energy consumption. The primary moisture content of pistachio kernels has been determined 0.569 (d.b.). DRYING of the kernels was performed at three levels of air velocity (1.16, 3.32 and 8.48 m/s), three levels of input air temperature (40, 55 and 70oC) and three levels of microwave power (220, 330 and 440W). The obtained effective DRYING time, moisture diffusivity, shrinkage and total energy consumption of pistachio ranged between 1.2 to 3.83 h, 2.7×10-10 to 1.32×10-09 m2/s, 12.01% to 35.43% and 0.337 to 1.63 kWh, respectively. The optimum point occurred at air temperature of 38.48°C, air velocity of 1.16 m/s and microwave power of 440 W. Response variable values for DRYING of Akbari cultivar of pistachio with FLUIDIZED BED microwave dryer at this point were DRYING time of 2.677 h, effective moisture diffusivity of 5.179×10-10, shrinkage percent of 18.41% and total energy consumption of 0.7109 kWh.