USE OF RSM TO OPTIMIZE DRYING TEMPERATURE AND LENGTH OF LEMONGRASS (Cymbopogan Citratus) AND ENHANCE SENSORY PROFILE OF GREEN TEA (Camellia Sinensis)

Abstract

The objective of this study was to optimize the drying temperature and length of lemongrass (Cymbopogon citratus) with respect to phytochemical content and antioxidant activity, and to evaluate its suitability for incorporation into green tea (Camellia sinensis) as a functional beverage. Fresh lemongrass leaves were cut into different lengths (1, 3, and 5 cm) and dried at varying temperatures (30°C, 45°C, and 60°C). Response Surface Methodology (RSM) using a Central Composite Design was applied to assess the combined effect of drying temperature and length on total phenolic content, total flavonoid content, tannin content, and DPPH radical scavenging activity. The optimized dried lemongrass was blended with green tea at different ratios, and the resulting tea samples were evaluated for sensory attributes using a nine-point hedonic scale. The results showed that both drying temperature and length significantly influenced the phytochemical composition and DPPH radical scavenging activity of lemongrass. The optimum condition was identified as drying lemongrass at 47.5°C with a length of 3.8cm, yielding the highest DPPH radical scavenging activity (79.42 ± 0.18%) along with elevated flavonoid (22.56 ± 0.92 mg QE/100 g), polyphenol (17.9 ± 0.03 mg GAE/100 g), and tannin contents (0.40± 0.02 mg/100 g). Higher drying temperatures and larger length led to significant losses of bioactive compounds (p < 0.05). Sensory evaluation revealed that green tea incorporated with optimally dried lemongrass showed superior acceptability compared to the control (6±0.408). The study concludes that optimized drying conditions effectively preserve the functional properties of lemongrass and enhance the sensory quality of green tea.