Chemical properties of vacuum-fried Pleurotus eryngii during storage and characterization of brown pigment

From the paper

Abstract

In this study, changes in the color value, 5-hydroxymethylfurfural (5-HMF), free amino acid (FAA), reducing sugar, peroxide value (PV) and malondialdehyde (MDA) in vacuum-fried Pleurotus eryngii products were investigated. The FAA and reducing sugar decreased, whereas 5-HMF, PV and MDA increased during storage. The brown pigment from vacuum-fried P. eryngii was purified, characterized and identified by HPLC-MS/MS and was found to have a UV-visible maximum absorption at 209 nm. The Fourier-transform infrared spectra spectrum showed that there were long-chain compounds as well as compounds with functional groups of –OH, C=O, –NH₂ and high conjugated C=C in the brown pigment. The brown pigment was also found to contain at least five compounds whose molecular weights were 562, 600, 554, 582 and 642, respectively. Among these compounds, there were long-chain fatty acid esters and derivatives produced by lipid oxidation. The presence of amides, aldehydes, ketones and carboxylic acids would suggest that the Maillard reaction was involved in the browning of vacuum-fried P. eryngii during storage.