Refractance Window Drying Of Aonla Pulp To Produce Powder

Abstract

Aonla fruits are found to be rich in ascorbic acid and have been reported to be useful in curing many diseases. Refractance Window (RW) drying is a novel thin-film drying process, generally used for drying of heat sensitive farm produce for retention of necessary quality attributes. Aonla pulp of 3 mm thickness was dried using RW drying process to obtain powder. RW drying was conducted to study the single layer drying kinetics, and other quality parameters such as colour, thermal properties, sieve analysis, FT-IR and SEM analysis. RW drying of 3 mm thick pulp entered into falling rate drying period after 6 min of constant rate drying. The diffusivity of moisture values for 3 mm thick pulp RW drying was 5.48 x 10-10 to 3.5 x 10-9 m 2 s -1. The dried powder was bright, more yellow and less green as compared to pulp. FT-IR results show that shift of spectrum peaks were more pronounced for 212 μm powders particles than for 500 μm powder particles with respect of pulp. Ascorbic acid presence is characterized by peaks obtained at 1633 cm-1, 1741 cm-1 in IR spectrum of pulp, 1747 cm-1 and 1629 cm-1, 1749 cm-1 in 500 μm and 212 μm powders particles, respectively. SEM analysis for powder particles shows that the RW dried powder particles were of uniform thickness and smooth surfaces.