Using NMR to study changes in the characteristic constituents of stored rice

This study investigated constituent differences between stored and fresh rice using multidimensional solution-state nuclear magnetic resonance (NMR) spectroscopy. Fourier transform infrared (FTIR) spectroscopy and gas chromatography mass spectrometry (GC-MS) was also used to determine constituent changes during storage. Signal variations in alkyl, alkoxy, acyl, hydroxyl, amine, and amino groups revealed hydrolysis of neutral fats and phospholipids to free fatty acids or lower esters. Signals from double bonds showed changes in unsaturated substances, such as glycerides and phospholipids, which correspond to a phenomenon. exposed by GC-MS detection, that is, a reduction in polyunsaturated fatty acids occurs on storage. Moreover, the hydrolysis or oxidation of unstable lipids result in a conversion from fresh to aging rice with respect to the development of disagreeable flavors. Results from this study can both aid in our understanding and further the research into the progression and phenomenon of aging rice. (C) 2017 Elsevier Ltd. All rights reserved.