Comparative analysis of drying kinetics of Stevia under various drying conditions
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
A study on the effect of drying method and layer thickness on the drying kinetics of stevia leaves was conducted at varying thickness of 1, 1.5 and 2cm using different methods viz. open sun drying, mechanical tray drying and forced convection solar drying (shade and without shade). Results for all the methods indicated that drying took place in the falling rate period. The drying times observed from various drying methods ranged from 240-540 minutes with lowest drying time being 240 min for mechanically tray dried sample of thickness 1cm and highest drying time being 540 min for sun dried sample of thickness 2cm. The moisture ratio as well as the drying rate decreased with an increase in the drying time for all the drying methods. The Page model for mechanical drying and Logarithmic model for sun and solar drying showed greater adequacy of fit between experimental and predicted data among other models. The stevia samples were analysed before and after drying for their physicochemical parameters viz. moisture content, colour, total sugar and total soluble solids. The least change in quality parameters was found to be in mechanically tray dried sample of thickness 1.5 cm followed by solar without shade dried sample of thickness 2cm. The dried stevia samples were also assessed for their quality parameters at a regular interval of 15 days over the storage period of three months, packaged in LDPE poly pack and LAF pack under ambient and refrigerated conditions. It could be inferred from the storage study that samples in LAF packaging material and under refrigerated conditions performed better.
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