Effect of Aerobic Fermentation of Yeast on Antioxidant Compounds and Antioxidant Activity of Okara Powder

Goh, Kai Shian (2022) Effect of Aerobic Fermentation of Yeast on Antioxidant Compounds and Antioxidant Activity of Okara Powder. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Recently, there has been an increasing demand for soybean products, resulting in production of 1.4 billion tons of okara per year. Okara is discarded as waste due to its high perishability and beany flavor. However, it is still abundant in nutrients which can exert beneficial health effects and is suitable to be utilized in food production. Biovalorization is one of the most cost-effective methods to valorise and add value to okara. The main purpose of this study was to investigate the potential of Kluyveromyces marxianus and Saccharomyces cerevisiae fermentation to increase the antioxidant compounds and antioxidant activities of okara. K. marxianus was first isolated from yogurt starter and cultured in broth before inoculation. After fermenting for 3 days at 30°C under aerobic conditions, the antioxidant compounds and activities of okara were determined by total phenolic content (TPC), total flavonoid content (TFC) and Diphenyl- 1-picrylhydrazyl (DPPH) scavenging activity analysis. The pH of fermented okara was also recorded. Okara fermented with K. marxianus has the lowest pH value (6.18 ± 0.02) and the highest TPC (2.831 ± 0.126 GAE mg/g), TFC (1.345 ± 0.011 GAE mg/g) and DPPH scavenging activity (1.135 ± 0.023 AAE mg/g), followed by okara fermented with S. cerevisiae, control and fresh okara. DPPH scavenging activity has a positive correlation with TPC and TFC (r = 0.932; 0.794), while having a negative correlation with pH (r = - 0.766) at