The effects of five structurally variant amino acids, glycine, valine, methionine, phenylalanine and
cysteine were examined as inhibitors and/or stimulators of fresh-cut potato browning. The first four
amino acids showed conflict effects; high concentrations (P100 mM for glycine and P1.0 M for the other
three amino acids) induced potato browning while lower concentrations reduced the browning process.
Alternatively, increasing cysteine concentration consistently reduced the browning process due to
reaction with quinone to give colorless adduct. In PPO assay, high concentrations (P1.11 mM) of the four
amino acids developed more color than that of control samples. Visible spectra indicated a continuous
condensation of quinone and glycine to give colored adducts absorbed at 610–630 nm which were
separated and identified by LC–ESI–MS as catechol–diglycine adduct that undergoes polymerization with
other glycine molecules to form peptide side chains. In lower concentrations, the less concentration the
less developed color was observed.