It depends on how you want to express the results and compare them with the literature later on. In my case, I usually prefer to convert the results from mg/l to mg/100 g considering the initial concentration used for producing the extract/drink.

Hello Avanthi Pabbisetty ;

Good question. If you are developing a fermented beverage, then it is correct for you to report your antioxidant results in terms of the volume of your sample (mL, uL, etc.). Bear in mind that for calculating the IC50 you need a plot of inhibition percent vs. extract concentration of your sample. For solid samples concentrations would be in mg/L; in your case you would need a v/v concentration; e.g. mL/L. After this you can convert these concentration to mL / kg of DPPH, or equivalent, considering the amount of reacted DPPH.

For the FRAP analysis, standards are used, and the results are expressed as equivalents of Trolox or Fe2+ as: mmol Trolox/mL of sample, or mmol Fe2+/mL. Here I include as a reference, a link to one of our paper related to antioxidant activity of tomato samples.

Article Effect of nitrogen fertilization and Bacillus licheniformis ...

Hope this helps for your research.

Regards

the results are converted as mg/100 mL (expressed as dry weight soluble solids fraction by 100 ml in the vol of sample used.