(1) DPPH* assay
The reaction started by adding 100 μL of ascorbic acid solution or the
diluted strawberry juice to the cuvette containing 4 mL of methanol
solution (0.14mol/L) of the free radical (DPPH*). The mixture was set
away from light for 15 min, and then the absorbance was measured at
765 nm with a spectrophotometer (UV-726, T6, PG General, Beijing,
China). Results were expressed as equivalents of mg of ascorbic acid
per 100 mL of juice.