Agricultural Biochemistry Department, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima Cairo, Egypt.
Horticulture Department, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima Cairo, Egypt.
Food Chem. 2016 Feb 1;192:879-85. doi: 10.1016/j.foodchem.2015.07.100. Epub 2015 Jul 23.
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 (⩾ 100mM for glycine and ⩾ 1.0M 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 (⩾ 1.11 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.
五种结构变异的氨基酸，甘氨酸、缬氨酸、蛋氨酸、苯丙氨酸和半胱氨酸，被用作抑制和/或刺激鲜切马铃薯褐变的抑制剂。前四种氨基酸表现出冲突效应；高浓度（甘氨酸 ⩾ 100mM，其他三种氨基酸 ⩾ 1.0M）诱导马铃薯褐变，而低浓度则减少褐变过程。相反，由于与醌反应形成无色加合物，半胱氨酸浓度的增加会一直降低褐变过程。在多酚氧化酶测定中，四种氨基酸的高浓度（甘氨酸 ⩾ 1.11mM）比对照样品产生更多的颜色。可见光谱表明，醌和甘氨酸不断缩合形成在 610-630nm 处吸收的有色加合物，这些加合物通过 LC-ESI-MS 分离和鉴定为儿茶酚-二甘氨酸加合物，它与其他甘氨酸分子聚合形成肽侧链。在较低浓度下，观察到浓度越低，颜色发展越少。
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