Vol. 10, Special Issue 12 (2021)

Author(s):
I Narmatha, S Ganapathy, M Balakrishnan, I Geethalakshmi and P Subramanian

Abstract:
Drying with superheated steam (SHS) as a drying medium is a novel technology with high potential benefits compared to conventional hot-air drying. This approach is becoming more common, particularly in drying of foodstuffs. The aim of this study was to explore the influence of SHS at low-pressure as a drying medium for fruits. Drying studies of apple slices were conducted in a convective batch type dryer with superheated steam at low pressure as a drying medium. Low-pressure superheated steam (LPSHS) drying was investigated at temperatures ranging between 70 and 90 °C and absolute pressure levels of 0.5 and 0.8 bar with steam flow rate at 0.1 and 0.3 m³/h, respectively. The apple slices dried under the condition of 90 °C, 0.5 bar pressure enhanced the drying rate from 0.195 to 1.02 g/min with reduced drying time of 130 min in order to attain a final moisture content of 108% (d.b.). In terms of physical attributes, samples exposed to a lower temperature level of 70 °C and low pressure of 0.5 bar had promising results. The volume, porosity (Ɛ), rehydration ratio and percentage shrinkage of LPSHS dried samples were 0.09 g/cm³, 0.87, 5.23 and 91%, respectively. Fruit slices with a pleasant cooked flavour can be obtained under these conditions with relatively better texture and colour.