Chemical Compositions and Antioxidant Capacities of Bauhinia strychnifolia Craib. : Grilling with a Double Belt Conveyor Dryer

Abstract

Yanang Daeng leaf tea is produced traditionally by grilling Bauhinia strychnifolia leaves with a charcoal stove. This method requires labor and time. Moreover, the heat cannot be controlled precisely and consistently which hinders industrial-scale production. We compare the chemical compositions and antioxidant activity in Yanang Daeng tea using grilling with the double belt conveyor dryer method (DBCD) and the charcoal stove method (CS). DBCD may be used effectively at temperatures of 80-120 ◦C over a period of 2-4 mins producing herbal tea leaves between 11.52-19.2 kg h^-1. The phenolic acid and flavonoid contents using HPLC after grilling with DBCD are generally higher than when using the conventional CS process. Total flavonoid contents (TFC) using (+) - catechin as a standard substance is higher when using DBCD than using CS. The antioxidant activity as tested using 2, 2-diphenyl-1-picrylhydrazyl (DPPH), revealed by both DBCD and CS are similar, showing that DBCD may be used effectively in place of CS.