Since the intact protein structure will be lost under physiological conditions after dietary consumption, it is imperative to evaluate the antioxidative capacity of peptide fragments generated from potato proteins with gastrointestinal proteases. Hydrolysis of isolated potato proteins with pepsin yielded PPHp. Further hydrolysis of the resulting product with pancreatin resulted in significant increase in the free amino group and a decrease in So (Table 1). This indicates higher degree of hydrolysis and release of smaller peptides and possibly free amino acids in the latter. Surface hydrophobicity varies in protein hydrolysates and typically has an inverse relationship with degree of hydrolysis (Paraman, Hettiarachchy, Schaefer, & Beck, 2007). Moreover, the peptide products were found to have low magnitude ζ-potential (Table 1) indicating low stability in the aqueous environment. The peptic and peptic-pancreatic digests possess net positive and negative charges, respectively, which are expected at the acidic and neutral pH and represent their physiological surface charges in the gastric and intestinal locations, respectively. In addition, the sample with higher degree of hydrolysis was found to possess larger mean particle size (Table 1), suggesting peptide aggregation possibly induced by clustering of the exposed hydrophobic amino acid residues; this supports the lower So observed for the sample. Furthermore, the significantly smaller particles observed for the peptic hydrolysate can be due to electrostatic repulsion at the cationic surface of the predominantly large peptides, which would discourage peptide interaction and aggregation. The differences in the surface property can impact the behaviour of peptides in food matrices, aqueous physiological environments and their interaction with hydrophobic and charged regions of biological targets.