Free radical scavenging activity (DPPH assay)

The DPPH radical scavenging activity was determined using the method described by Thaipong et al. (2006). 24 mg DPPH were dissolved into 100 mL methanol to make stock solution and kept it at − 0 °C until use. The chemical solution was prepared by mixing 10 mL stock solution with 45 mL methanol to the absorbance of 1.1 ± 0.02 unit at 515 nm using the spectrophotometer (Cary 60 UV–Vis, Agilent Technologies, CA, USA). Sausage sample extract (0.5 mL) was allowed to react with 2.5 mL of the DPPH solution for 2 h in the dark. Then the absorbance was taken at 517 nm. The residual radicals were calculated as followed:

where [DPPH_Blank] is the absorbance of DPPH radicals in blank with distilled water instead of sample and [DPPH_Sample] is the absorbance of DPPH radicals in the sample.