Optimization of Fluidized Bed Drying Process of Green Peas Using Response Surface Methodology

Abstract

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.

Keywords:

• Fluidized bed drying
• Green peas
• Process optimization
• Response surface methodology
• Sensory analysis

ACKNOWLEDGEMENTS

We thank the Natural Sciences and Engineering Research Council of Canada (NSERC) for partial funding of this study.

Notes

^a Code 0 is for center point of the parameter range investigated, ±1 for factorial points, and ±2 for augmented points; X ₁ for temperature (°C), X ₂ for tempering time (min), X ₃ for pretreatment, and X ₄ for mass per unit area (g/cm²).

^b Factorial points were in half replication.

^a CBLL stands for chemical blanching in a solution of 2.5% NaCl and 0.1% NaHCO₃, P₁ for pricking once, HWB for hot water blanching, P₂ for pricking twice, CBHL for chemical blanching in a solution of 5% NaCl and 0.1% NaHCO₃.

X ₁ is the temperature (°C), X ₂ the tempering time (min), X ₃ the pretreatment, and X ₄ the mass per unit area (g/cm²).

^a F-table_14,16,0.95 = 2.38.

∗∗Significant at P ≤ 0.05.

∗∗, ∗Coefficient significant at P ≤ 0.05, P ≤ 0.01, respectively; ^nsCoefficient insignificant.

X ₁ is the temperature (°C), X ₂ the tempering time (min), X ₃ the pretreatment, and X ₄ the mass per unit area (g/cm²).

^a Type of pretreatment was decided based on the closest integer values; X ₁ is the temperature (°C), X ₂ the tempering time (min), X ₃ the pretreatment, and X ₄ the mass per unit area (g/cm²).

^a Best result.

^b Second best result.