I made ice cream using red pitaya peel and i need to measure the DPPH inhibition percentage for both red pitaya peel and ice cream. As we know, red pitaya peel has such strong red purplish color meanwhile my ice cream is slightly pink color.

Can I use different sample volume for my DPPH assay? I've tried using 1,5 ml ice cream extract+2,5 ml DPPH solutions and 0,5 ml red pitaya peel extract+3,5 ml DPPH solution

But the ice cream gives bigger DPPH inhibition percentage than my red pitaya peel

Is it because of different sample's volume? I can't use 1,5 ml red pitaya peel extract like ice cream one because the color is too strong so it doesn't turn to yellow after incubation

Is there any solution? Because I already performed Phenolic content assay and my ice cream's phenolic lower than red pitaya peel's

Thank you