Effect of Pasteurization on Total Flavonoid Content and Ferric Reducing Antioxidant Power of Tempeh-Based Soy Sauce

Nowadays, tempeh is consumed almost all over the world, but unfortunately, it is highly perishable. Tempeh can be processed into soy sauce lasting up to 3 years to increase its functional value. This study aims to determine the effect of pasteurization on the total flavonoid content and ferric-reducing antioxidant power of tempeh-based soy sauce. Three different tempeh fermentation times (2 days, 3 days, and 4 days) were used in this study, with koji as the control. Total flavonoid content and ferricreducing antioxidant power were measured for 1 month, 2 months of fermentation, and after pasteurization. Results showed a significant increase in total flavonoid content and antioxidant capacity after 1 and 2 months of fermentation. Meanwhile, total flavonoid content decreased after pasteurization, but antioxidant capacity increased. Furthermore, koji has the highest value of total flavonoid content and antioxidant capacity, whereas tempeh-based soy sauce was the lowest with an increase along with the tempeh fermentation time. It can be concluded that the fermentation time of soy sauce and tempeh could increase the total flavonoid content, while pasteurization increases antioxidant capacity but decrease the total flavonoid content.