Effect of Spirulina platensis addition on physicochemical, bioactivity, and sensory properties of fermented soybean as a potential functional food product

In the last decade, fermented soybean called tempeh has gained popularity globally as a healthy food especially for vegan/vegetarian and organic food enthusiasts. In order to improve the functionality of tempeh, Spirulina platensis , which is known to have high antioxidant activity is added to tempeh. Due to the unpleasant odour of Spirulina , the supplementation level of Spirulina on tempeh needs to be optimized to obtain tempeh product which has good nutrition and functionality as well as acceptability by the consumers. In this study, Spirulina was added at 5–40 g/kg and the fermentation varied from 24 to 72 h. The nutritional values of Spirulina tempeh was then analyzed, including proximate composition as well as antioxidant, α-amylase inhibition, and angiotensin I-converting enzyme (ACE)-inhibition activity. To evaluate the influence of Spirulina addition on tempeh sensory, hedonic and intensity tests were performed. The result of the study showed that the best fermentation time was 48 h, no difference of nutrition was observed with different addition of Spirulina . However, the Spirulina addition on tempeh increased the antioxidant, α-amylase inhibition, and ACE-inhibition activities by 39–104.7%, 12.2–33.5% and 28.2–46.5% compared to tempeh without Spirulina addition. The highest antioxidant, α-amylase inhibition, and ACE-inhibition activities were obtained with addition of 40 g/kg, 40 g/kg, and 20 g/kg, respectively. The overall likeness was in the range of 5.07–6.98 from 1–9 scales, the value decreasing along with the increase of Spirulina addition. Based on the nutrition, bioactivity, and sensory test, addition of 20 g/kg of Spirulina is suggested. The result reveals that Spirulina tempeh is a potential functional food.