Influence of Drying Conditions on the Drying of Longan without Stone by Low-Pressure Superheated Steam
This research aims to study the use of low-pressure superheated steam (LPSS) drying for longan without stone. The effects of drying conditions, i.e., drying temperature and pressure on the drying kinetics and dried product quality viz. color, shrinkage, rehydration and texture (toughness) were investigated. The experiments were conducted at the drying temperatures of 70-90oC and absolute pressures of 7-15 kPa. Sample with an initial moisture content in the range of 350-400% dry-basis was dried until its moisture content reached 18% dry-basis. Results showed that drying rate increased as drying temperature increased and as pressure decreased. Total color difference seemed to decrease whereas shrinkage increased when drying temperature decreased and pressure increased. Rehydration and toughness increased when drying temperature and pressure increased. Considering drying time and product quality, LPSS drying at 80oC and 15 kPa was the best condition for drying longan without stone in this study.
Keywords - Drying, Longan, Low-Pressure Superheated Steam, Quality.