Optimal roasting condit ions for maximizing the quality of tea leached from high functional Perilla frutescens leaves

This study was carried out to investigate the optimal roasting conditions for developing perilla leaf leached tea, which has high functional Perilla frutescens leaves. The roasting processes were carried out with variations in roasting temperature (120-200 °C) and roasting time (15-35 min), the response surface methodology was applied to monitor the changes in qualities of the roasted Perilla frutescens leaves. The antioxidant, bioactive substance in roasted Perilla frutescens leaves, and their extracts were the quality parameters. The total polyphenol and total flavonoid contents increased with time and temperature up to 25 min and 160 °C. Antioxidative activities showed a positive correlation with the amount of phenolic compound. Caffeic acid and rosmarinic acid contents increased with time up to a mild temperature, 160 °C, while they decreased at high temperatures over 160 °C. The optimum roasting conditions selected for developing perilla leaf leached tea were thus 180 °C and 20 min, given the conditions in the above experiments.