The Enhancement of Isoflavone Aglycones Daidzein and Genistein from Soybean Devon-1 Tempeh through Heat Treatment after 61 Hours of Fermentation

Abstract

Daidzein and genistein, the main isoflavone aglycone in soybean, are significantly gaining attention due to the numerous health benefits. Devon-1 variety of soybean, found in Indonesia, has the highest total isoflavone content. However, the compound predominantly exists in glycoside form, requiring hydrolysis during tempeh fermentation to obtain bioactive aglycone. Previous investigations indicated that ethanol extract of Devon-1 soybean after 61 hours showed lower daidzein and genistein levels compared to 1 N HCl hydrolyzed soybean. Therefore, this study aimed to enhance daidzein and genistein contents through heat treatment of Devon-1 soybean tempeh after 61 hours of fermentation. The sample was heated using a dry oven at 40, 50, and 60°C for 2 hours and extracted with ultrasonic bath with ethyl acetate solvent and 100% amplitude for 10 mins. Extract was analyzed using RP-HPLC with UV/Vis detector at 265 nm, methanol, and 0.1% acetic acid (47:53) as mobile phase. The results showed a 2-3 times increase in daidzein and genistein levels after heat treatment in all temperatures, particularly at 40°C. This suggested that heat treatment was a viable means to enhance the main isoflavone in tempeh.