Kinetic study, optimization and comparison of sun drying and superheated steam drying of asam gelugor (Garcinia cambogia)

Abstract

The purposes of present study are to compare the kinetic drying of the G. cambogia through sun drying and superheated steam drying (SSD) method and optimizing the quality of SSD of it through response surface methodology. G. cambogia fruit rinds were dried at temperature of 150°C, 200°C and 250°C. The drying curves were fitted into the mathematical model of Page, Lewis and Henderson-Pabis models. Page model was found to be the best in describing the drying behavior of G. cambogia. Drying rate constant (k) increased as temperature increased and SSD method had overall higher drying rates ranged from 5.929 x 10-5 to 5.861 x 10-4 min-1 than sun drying method which was 4.980 x 10-6 min-1 . Total acid number showed a trend of increased followed by decreased over drying time. superheated steam drying process of G. cambogia fruit rinds was optimized by using response surface methodology employing a central composite design. Drying time and temperature were the factors in optimization while moisture content (wet basis), acid number and lightness (*L) were the response parameters. Experimental results were fitted to a second-order polynomial model and the model fitness and optimal drying condition were determined by regression analysis and analysis of variance. The optimal conditions for superheated steam drying of G. cambogia fruit rinds were identified as 46.60 mins and 150°C with the composite desirability of 0.913. Application of superheated steam drying under controlled conditions resulted in faster drying process and better quality of dried G. cambogia than conventional sun drying technique.