Study of interval infrared Airflow Drying: A case study of butternut (Cucurbita moschata)

Abstract

Abstract Interval process is defined as a means of operating short-time intervals configured to allow the material to attain characteristics to match higher drying rate. The innovative Interval Infra-Red Airflow Drying (IIRAD) involves successive heating intervals (tON) of several seconds followed by tempering periods (tOFF) of a few minutes. IIRAD provides heat only when the product surface is fully rewetted. Drying of winter squash slices was performed in three cases; continuous IR-drying, IIRAD-I: tON=5 s and tOFF=2 min, and IIRAD-II: tON varies throughout the process with tOFF=2 min. A higher drying rate was observed during IIRAD-I. Measured evaporating-bulb temperatures were below 21°C with energy consumption of 0.98 and 0.77 kWh/kg of evaporated water for I-IIRAD and II-IIRAD, respectively, wherein they exceeded 66°C and 2.19 kWh/kg of evaporated water for continuous drying. IIRAD resulted in better preservation of flavonoids and better retention of color. However, continuous IR-dried samples displayed better rehydration and higher total polyphenol content. Overall, IIRAD is shown to be a promising drying technique for heat sensitive materials in terms of efficiency, energy consumption, and preservation of key quality attributes linked to lower operating temperature, but with increased drying time.