Dose-dependent (A) Fe(III) reducing and (B) Fe(II) chelating capacities of potato protein hydrolysates (PPH) produced with pepsin (PPHp) and pepsin-pancreatin (PPHppc); GSH, reduced glutathione (standard physiological antioxidative peptide); EDTA, ethylenediaminetetraacetic acid (standard divalent metal chelator); bars, in each figure, with different letters represent significantly different mean values (P