[zuzig]

Thank you people for sharing your brain powers:).

[zuzig]

Thank you very much for your answer. 
So would you say, that I could judge the potency of different vitamin C serums by this test on apples, or? I have compared too samples of grated apples, one I treated with drops of the oil serum I mentioned and the other by ascorbic acid diluted in water (200 mg/30 ml of water) - the one treated with ascorbic acid diluted in water did not brown at all. So the high concentration of ascorbic acid and high acidity of the solution inhibited completely the oxidation thus the enzymatic reaction? Does this other oil serum which did not inhibit the oxidation processes can be considered as not potent enough?