Characterization of the reactions of β-lactoglobulin and potato proteins with chlorogenic acid using a UHPLC-ESI-MS...

During isolation of proteins from potatoes, endogenous phenolics react with proteins and lead to undesired brown discoloration. To find effective anti-browning strategies, the underlying mechanisms of protein-phenolic interactions should be understood. Therefore, potato protein fractions rich in either protease inhibitors (PI) or patatin were incubated with chlorogenic acid (CGA) under autoxidative conditions at pH 8.5 for 24 h or in the presence of polyphenol oxidase (PPO) at pH 7 for 3 h. Covalent protein modifications were analyzed with a novel UHPLC-ESI-MS approach. β-lactoglobulin incubated with CGA was included as reference. Comparable discoloration was observed for PI and patatin fractions, namely greening for autoxidation and browning for PPO-mediated oxidation. PIs were partly covalently modified with CGA monomers and dimers, whereas patatin was not covalently linked to phenolics. The results show that discoloration can be clearly observed even when the majority of proteins in a sample is unmodified and highlight the need to mitigate browning reactions during potato protein extraction.