Effect of microwave assisted hot-air drying temperatures on drying kinetics of dried black gram papad (Indian snack food)

Abstract

In this study, suitable drying techniques were evaluated for drying black gram papad using sun, tray and microwave assisted hot-air drying (MAHD). Drying of black gram papad in MAHD consumes less time (100-175 min) compared to tray (240 min) and sun (355 min) drying methods. Therefore, the drying characteristics of black gram papad were evaluated with MAHD using varying temperatures ranges of 40, 50 and 60 °C and validation was performed with fifteen thin-layer drying models. The suitability of different models was estimated using the coefficient of determination (R2), standard error of estimation (SEE), root mean square error (RMSE), relative mean error (P0) and chi-square (χ2). The ‘Weibull distribution model’ showed the best fit with the highest R2 (0.99) and lowest SEE (0.0002-0.0003), RMSE (0.0026-0.0047), P0 (6.40-7.49 %) and χ2 (0.0448-0.0677) values for drying black gram papad using varying temperatures of MAHD. The moisture diffusivity for varying temperatures (40 to 60 °C) of MAHD ranged from 4.60×10-09 to 6.28×10-09 m2/s and the activation energy was found to be 13.50 kJ/mol. The drying of black gram papad using the MAHD method will be beneficial and time-consuming for the papad manufacturing industries in India.

Keywords

• Black gram papad
• Microwave assisted Hot-air drying
• Thin-layer drying
• Moisture diffusivity
• Activation energy