Extraction, isolation and identification of an enzymatic browning product from fresh white salted noodles

Abstract An enzymatic browning product (EBP) of fresh white salted noodles (FWSNs) was extracted, purified, isolated and identified. The optimum parameters of extraction were as follows: volume fraction of ethanol 70%, solid-liquid ratio 1 : 10 (g: mL, samples: ethanol solution), extraction time 10 days (20 °C). In the purified process, protein (99.86%) and carbohydrates (69.50%) impurities were removed from the crude extract using Sevag method, dialysis method and AB-8 macroporous resin column. The purified EBP was separated using 20% (v: v) methanol solution in a C18 chromatographic column. A monomer of EBP was isolated by high-performance liquid chromatography. Nuclear magnetic resonance and infrared spectroscopy analysis showed that the EBP monomer was 2-hydroxyindole-3-propylamine. This was the first time in the literature that 2-hydroxyindole-3-propylamine was found in the EBP of FWSNs. It would lay a material foundation for investigating the origin of EBPs and the revealing enzymatic browning mechanism of FWSNs.