Table 7.

Antioxidant activities of collagen samples as determined by the DPPH radical scavenging test.

Antioxidant Activity	µmol AAE/g Protein	mg AAE/g Protein
Bromelain-soluble collagen	1.03 ± 0.03	0.18 ± 0.00
Pepsin-soluble collagen	2.62 ± 0.03	0.46 ± 0.01

All values are given as mean ± standard deviation, n = 2. Values of antioxidant activities showed significant differences between pepsin-soluble collagen and bromelain-soluble collagen, determined by one-way ANOVA (p < 0.05). The straight-line equation for the antioxidant activity of ascorbic acid, used as a positive control, was: Y₁ = −0.0193X₁ + 0.1902, R² = 0.8707; or Y₂ = −0.0034X₂ + 0.1902, R² = 0.8707. X₁ and X₂ are the corrected absorbances and Y₁ and Y₂ are the concentrations of ascorbic acid in mg/L and µmol/L, respectively. The antioxidant activities of the collagen samples were converted into µmol AAE/g protein, or mg AAE/g protein. The IC₅₀ for ascorbic acid was 3.11 ppm.