STUDY OF HEAT PUMP DRYING CONDITION OF GYMNEMA SYLVESTRE LEAF FOR RECOVERY EFFICIENCY IMPROVEMENT OF PHENOLIC AND FLAVONOID

Abstract

This study optimizes heat pump drying condition of Gymnema sylvestre leaf in order to
improve the recovery efficiency of total phenolic and flavonoid content via Response Surface
Method (RSM). Central Composite Designed (CCD) experiments were implemented to obtain the
regressive model of total phenolic content losses (Y1, %), total flavonoid content losses (Y2, %)
and moisture content (Y3, %) due to three factors: drying air temperature (X1), drying air velocity
(X2) and drying time (X3). Due to obtained model, optimal condition of heat pump drying process
which minimizes bioactive content loss and moisture is 53oC (drying air temperature), 1.1m/s
(drying air velocity) và 480 minutes (drying time). At found condition, total phenolic content loss
(TPCL) is 16.82 ± 0.05%, total flavonoid loss is 17.51 ± 0.07% and moisture content (MC) is
6.72 ± 0.04%.