The effect of rotary drying temperature on drying characteristic and antioxidant activity of Etlingera elatior Jack

The study was conducted to investigate the effect of drying temperature on a rotary type of dryer for drying characteristics and antioxidant activity of Etlingera elatior flower. This study used a lab-scale rotary dryer which was a modification of the commercial oven heater from the market. The research design was a Randomized Block Design (RCBD) with one factor, i.e. the drying temperature, which consisted of four temperature levels, 60oC, 70oC, 80oC and 90oC. All experiments were repeated six times. The results showed that the drying of Etlingera elatior flowers at three different temperatures (70oC, 80oC and 90oC) required a shorter drying time than that of 60oC. The drying rate of the samples at 70oC, 80oC and 90oC was drastically decreased before the 200th min, while 60oC took a long time to 380 mins. The drying rate pattern with the drying temperature of 60oC showed a significantly lower total phenolic content of Etlingera flowers compared to 70oC, 80oC and 90oC, while there was no significant difference in total phenolic content among 70oC, 80oC and 90oC. In addition, different drying temperatures did not give a significant effect on the antioxidant activity based on the DPPH (2,2-diphenyl-1- picrylhydrazyl radical) method. This study proposed the effectiveness of drying using a rotary dryer in maintaining the total phenolic content and antioxidant activity of Etlingera flowers.