Effects of spray-drying conditions on functional properties of bioactive compounds extracted from Lotus leaf

Abstract

In order to determine the effects of spray-drying conditions on functional properties of lotus leaf extract, Total Phenolic Content (TPC), Total Flavonoid Content (TFC), alpha-amylase, alpha-glucosidase inhibition activity and DPPH scavenging activity of the extracts before and after spray-drying at different temperatures and carrier concentrations were investigated. Lotus leaf was extracted by 75% ethanol in 20 min for three times and then concentrated to 50% (v/v) by vacuum evaporator. Maltodextrin and gelatin were used as carriers in spray drying process with the ratio 7:3 (w/w) and at concentration 10, 20, 30% (w/v). The mixtures of carriers and extract were dried in spray drying chamber with 400mL/min feed rate, 1.2 – 1.3 bar air pressure, 10 rpm pump speed and air inlet temperature at 130, 150, 170, 190oC. TPC, TFC and other functional properties were shown to have strong correlation which suggested that the phenolic compounds presented in the extract may be responsible for the DPPH radical scavenging ability, alpha-amylase and alpha-glucosidase inhibition activity. Significant loss on TPC and TFC (28.74 to 40.63% and 25.52 to 36.87%, respectively) were brought to the decrement of alpha-amylase, alpha-glucosidase inhibition activity and DPPH scavenging activity after spray-drying. In this study, the highest TPC and TFC recovery after spray drying (79.24% and 81.87%, respectively) were obtained at 130oC and 20% carrier concentration. Key words: Lotus leaf, TPC, TFC, antioxidant activity, alpha-amylase inhibition, alpha-glucosidase inhibition, spray-drying, air inlet temperature, carrier concentration.