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This study investigates the performance of microwave vacuum–assisted drying (MVD) of green peas using both fluidized bed and heat pump systems. A comparative study of heat pump–fluidized bed atmospheric freeze drying (HP-FB-AFD) and heat pump–fluidized bed hot air convective drying (HP-FB-HACD) was conducted. The initial drying rates of green peas were 0.04 and 0.12 1/min for HP-FB-AFD and HP-FB-HACD, respectively. Moisture diffusivity of green peas dried in HP-FB-HACD and HP-FB-AFD were 1.04 × 10−9and 6.94 × 10−11 m2/s, respectively. HP-FB-AFD did not entail changes in the starch granules and preserved the sample size and shape with minimal shrinkage (20%), whereas HP-FB-HACD generated significant volumetric shrinkage (50%). HP-FB-AFD+MVD created a desirable porous inner structure of the final product. HP-FB-HACD+MVD significantly increased the hardness of the dried product and produced green peas with a compact structure and tightly packed cells. Neither HP-FB-AFD+MVD nor HP-FB-HACD+MVD significantly influenced the color of dried green peas. To respond to the current demand for high-quality products, the multistage combined HP-FB-AFD+MVD method is an interesting technique for green peas processing. [ABSTRACT FROM PUBLISHER]

In this study, green pea drying is investigated experimentally in a laboratory-scale spouted bed dryer. A mathematical model is also developed to investigate the effect of operating conditions on the performance of the system. The effect of operating parameters such as inlet air temperature, particle size, and flow rate of the drying air on the performance of the dryer are studied experimentally. In order to build the process model, it is necessary to analyze the transport in both solid and gas phases. A complete set of equations with no adjustable parameters is derived for existing zones in the spouted bed dryer in order to predict variations in the temperature and moisture content of the solid and gas phases with time for batch drying conditions. Model results are compared with corresponding experimental data. Agreement between the model results and experimental data is good. [ABSTRACT FROM AUTHOR]

In this study, a drying kinetics model for predicting the drying of green pea particles using a bench-scale spouted bed with heat carriers is investigated. The experiments were carried out under different operating conditions. The effect of inert particle diameter, inert particle type, and the mass ratio of inert particles to green peas was examined based on the performance of the dryer and the rate of drying. As expected, the rate of drying increased with increased mass ratio of inert particles to green peas and thermal diffusivity of inert particles. [ABSTRACT FROM AUTHOR]

Response surface methodology was used to optimize the pretreatment prior to solar cabinet drying (SCD) of green peas. Thirteen experiments were conducted using a central composite design (CCD) with two variables at two levels each, viz. blanching time (1-5 min) and potassium metabisulphite (KMS) concentration (0.2-0.5%). Solar cabinet drying of pretreated green peas was carried out up to 6% (d.b) moisture content. During drying the air temperature, relative humidity, and air velocity in the dryer were in the range 40-60°C, 40-50%, and 0.9-1 m/s, respectively. After drying, color (a value) and hardness (g) of the dehydrated green peas were measured and taken as responses. During optimization, the best process conditions were found with 4.24-min blanching time and 0.49% KMS concentration resulting into -7.86 color (a value) and 548 g hardness. Green peas were dried in solar cabinet dryer using the pretreatment at optimum conditions and some selected quality parameters like color (a value), hardness, rehydration ratio, shrinkage, overall acceptability, and drying time were used to compare the solar cabinet drying method with other drying techniques like freeze (FD), fluidized bed (FBD), and open sun drying (OSD). Drying kinetics and moisture diffusivity were determined and compared. [ABSTRACT FROM AUTHOR]

Green peas were dried in a vacuum-assisted microwave drying system. The effects of microwave power levels (100-300 W) and system vacuum (50-400 mm Hg) on drying parameters (viz. drying efficiency and drying time) and some quality attributes (viz. linear shrinkage, apparent density, green color, rehydration, and sensory attributes) of dehydrated peas were analyzed by means of response surface methodology. A face-centered central composite design was used to develop models for the responses. Analysis of variance showed that a second-order polynomial model predicted well the experimental data. The system microwave power level strongly affected quality attributes of dehydrated peas and drying parameters. A higher vacuum during drying resulted in a better quality product. Microwave power of 237.31 W and a 360.22 mm Hg vaccum were found to be optimum drying conditions for vacuum-assisted microwave drying of green peas. [ABSTRACT FROM AUTHOR]

The thin-layer drying of three varieties of green peas was carried out in hot air-drying chamber using an automatic weighing system at five temperatures (55-75°C) and air velocity of 100 m/min. The green peas were blanched and sulphited before drying. The variety Pb-87 dried at 60°C was judged to be best for quality on the basis of sensory evaluation and rehydration ratio. The Thomson model was found to represent thin-layer drying kinetics within 99.9% accuracy. The effective diffusivity was determined to be 3.95 × 10-10 to 6.23 × 10-10 m2/s in the temperature range of 55 to 75°C. The activation energy for diffusion was calculated to be 22.48 kJ/mol. The variation in shrinkage exhibited a linear relationship with moisture content of the product during drying. The Dincer number at drying air temperature 60°C and drying air velocity 100 m/min was determined to be 2,838,087. The difference between temperatures of drying air and that of green pea kernels was found to decrease with drying time for all the drying temperatures taken for investigation. [ABSTRACT FROM AUTHOR]

The fluidized bed drying process of green peas was optimized using the response surface methodology for the process variables: drying air temperature (60-100°C), tempering time (0-60 min), pretreatment, and mass per unit area (6.3-9.5 g/cm2). The green peas were pretreated by pricking, hot water blanching, or chemical blanching. Product quality parameters such as rehydration ratio, color, texture, and appearance were determined and analyzed. Second-order polynomial equations, containing all the process variables, were used to model the measured process and product qualities. Rehydration ratio was influenced mostly by pretreatment followed by tempering time, temperature, and mass per unit area. Pretreatment and mass per unit area significantly affected color and texture. Higher levels of temperature and lower levels of tempering time and mass per unit area increased the rehydration ratio. The optimum process conditions were derived by using the contour plots on the rehydration ratio and sensory scores generated by the second-order polynomials. Optimum conditions of 79.4°C drying air temperature, 35.8-min tempering time, pretreatment of the once pricked peas with chemical blanching in a solution of 2.5% NaCl and 0.1% NaHCO3, and mass per unit area of 6.8 g/cm2 were recommended for the fluidized bed drying of green peas. At these conditions the rehydration ratio was 3.49. [ABSTRACT FROM AUTHOR]