3.3.9. Antioxidant Properties

Film extract solution was prepared according to the method described in Tongnuanchan et al. [35]. The film (25 mg) was added with 3 mL of distilled water. After stirring for 3 h, the mixtures were centrifuged at 3000 g for 10 min and the supernatant obtained was then determined for DPPH radical scavenging activity. The film extract solution (1.5 mL) was added to 0.15 mM 2,2-diphenyl-1-picryl hydrazyl (DPPH) in 95% ethanol (1.5 mL), followed by mixing, and then kept in the dark for 30 min at room temperature. The DPPH assay solution recorded the absorbance at 517 nm using a spectrophotometer. The films’ antioxidant activity was expressed as the percentage of DPPH radical scavenging activity.