Optimization of Fermentation Time and Temperature to Enhance Phenolic Content and Antioxidant Activity of Traditional Tempe as a Functional Food

Tempe is a traditional Indonesian fermented soybean product with growing potential as a functional food due to its bioactive compounds. This study aimed to evaluate the effects of fermentation time and temperature on total phenolic content and antioxidant activity of tempe and to determine optimal fermentation conditions. Tempe samples were fermented for 24, 36, and 48 h at two different temperatures (28 and 32°C). Total phenolic content was determined using the Folin–Ciocalteu method, while antioxidant activity was measured by the DPPH radical scavenging assay. The results demonstrated that both fermentation time and temperature significantly affected total phenolic content and antioxidant activity. The highest phenolic content (11.14 mg GAE/g) and antioxidant activity (62.1% DPPH inhibition) were obtained at 36 h fermentation at 32°C. Prolonged fermentation (48 h) led to a decrease in both parameters. A positive relationship was observed between total phenolic content and antioxidant activity, indicating that phenolic compounds play a major role in the antioxidant potential of tempe. These findings suggest that optimization of fermentation conditions can enhance the functional properties of traditional tempe.