This time, we will introduce an example of measuring the antioxidant capacity (DPPH radical scavenging activity) of food using 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), which is known as a stable radical. DPPH is known as a purple stable radical and becomes colorless when reduced. This time, by adding tea to DPPH, we confirmed whether changes would occur due to antioxidants such as catechins.