Potential anti-oxidative properties and quality characteristics of Korean traditional rice cake added with black soybean (Rhynchosia nulubilis) as inner beauty material in COVID-19 pandemic

Humans have a great desire to live a long and healthy life, but as they age, their physical functions weaken and they cannot live long and healthy due to problems such as eating habits and lifestyle. Therefore, in this study, 0%, 5%, 10%, 15% and 20% of black soybeans with high protein content and high antioxidant power were added to rice cake, a traditional Korean food, to compare quality characteristics, antioxidant effect, and preference survey. As a result of the experiment, as the content of black beans increased, the moisture content and pH decreased, and the color and texture were slightly different. In addition, the contents of polyphenols and flavonoids increased significantly. ABTS radical scavenging activity also showed a significant increase, with values of 15.37 ± 3.63 ( p < 0.01), 36.23 ± 2.00 ( p < 0.001), 63.90 ± 3.82 ( p < 0.001), and 78.75 ± 1.00 ( p < 0.001). Similarly, DPPH radical scavenging activity significantly increased to 7.91 ± 2.92, 14.59 ± 1.91 ( p < 0.01), 17.37 ± 1.46 ( p < 0.001), and 31.54 ± 1.05 ( p < 0.001). Meanwhile, sensory evaluation results indicated that as the black soybean content increased, overall preference decreased. Therefore, the optimal addition level was determined to be between 5% and 10%. Therefore, if the moisture content is increased, it is expected to be an inner beauty food and health functional food that can satisfy functionality and palatability, and it is judged to be helpful in the COVID-19 pandemic.