Comparison of pulse electric field, microwave and ultrasonic pretreatment prior to black rice extraction on antioxidant and sirtuin1 enzyme stimulating activities

Abstract

The objective of this research was to investigate the effects of pulse electric field, microwave, and ultrasonic assisted water extractions on the bioactive compounds in black rice, and their antioxidant and sirtuin1 enzyme stimulating activities. The number of pulses were changed from 1,000 to 2,000 and 3,000 at a constant electric field intensity of 5 kV/cm. Microwave and ultrasonic conditions were followed by 800 W for 20 min and 60 °C for 20 min, respectively. The results found that using pulse electric field with 3,000 pulses and microwave achieved high concentrations of total phenolic compound and cyanidin-3-glucoside with non-significantly difference. Extracts from the pulse electric field with 3,000 pulses showed the significantly highest DPPH scavenging activity (30.83 ± 2.06%) and the sirtuin1 enzyme stimulating activity (27.260 ± 0.418 of fluorescence intensity) when compared with microwave and ultrasonic extractions. Scanning electron microscopy and fourier transform infrared spectroscopy results showed distinct differences between the effects of these methods on the outer surface. The overall results revealed that pulse electric field and microwave were similarly effective at increasing the content of bioactive compounds in extract and their antioxidant activities. However, the pulse electric field was considerably more effective for activating sirtuin1 enzyme activity.

Keywords:
pulse electric field; microwave; ultrasonic; black rice grain; antioxidant activity; surtuin1 enzyme