Extraction of Bioactve Compounds from Lemongrass and Freeze Driying of Lemongrass Extract Powder

Tan, Shuen Shuen (2021) Extraction of Bioactve Compounds from Lemongrass and Freeze Driying of Lemongrass Extract Powder. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Lemongrass (Cymbopogon citratus), a spice which is known to have antioxidant and anti-inflammatory properties and is commonly used in Asian cuisine and herbal tea. However, only the stems are utilized while most of the leaves are discarded as waste. This study was conducted to determine the optimum hot water extraction parameters for whole lemongrass and the effect of maltodextrin concentration on the freeze-dried lemongrass extract. Response surface methodology (RSM) with Box-Behnken design (BBD) was used to investigate the effect of the extraction temperature (70 °C, 80 °C and 90 °C), extraction time (20, 40 and 60 minutes) and solid to liquid ratio (1:10, 1:20 and 1:30 (w/v)) on total phenolic content (TPC), total flavonoid content (TFC), 1,1-diphenyl-2- picryhydrazyl (DPPH) free radical scavenging activity, ferric reducing antioxidant power (FRAP) and inhibition of albumin denaturation (IAD). Temperature significantly influenced TPC, TFC, FRAP and IAD at P < 0.05. The optimized extraction parameter obtained from Box-Behnken design is 85 °C, 47 minutes and 1:30 (w/v) contributed to 56.07 ± 4.42% of yield, 463.70 ± 7.45 mg GAE/100 g of TPC, 5903.01 ± 23.09 mg QE/100 g of TFC, 1105.48 ± 24.58 mg AAE/100 g of DPPH, 1557.35 ± 54.02 mg FE/100 g of FRAP and 1014.80 ± 17.38 mg DSE/100 g of IAD with desirability of 0.9058. The optimized extract was subsequently freeze dried with addition of different maltodextrin ratio (20%, 30% and 40%) into lemongrass extract to encapsulate the freeze-dried lemongrass extract powder. The freeze-dried lemongrass extract with 40% of maltodextrin have the lowest moisture content (5.57 ± 0.15%), water activity (0.285 ± 0.013); highest solubility (3.11 ± 0.24%) and extraction yield (27.93 ± 0.53%) while freeze dried lemongrass extract with 20% of maltodextrin have the highest TPC (54.62 ± 0.07 mg GAE/100 g), TFC (425.16 ± 3.98 mg QE/100 g) and FRAP (125.18 ± 4.07 mg FE/100 g). In short, extracts from dried whole lemongrass powder and its freeze-dried lemongrass extract has potential to be incorporated into food and beverages to increase their bioavailability.