Distribution of lysophosphatidylcholine in the endosperm of Oryza sativa rice

Sake is made from fermented rice and has been drunk in Japan for more than 1000 years. The rice must be polished prior to fermentation to obtain high-quality sake. It is traditionally recognized that the quality of sake is improved as the rice polishing ratio (percentage removed in the polishing process) increases. However, the underlying chemistry of the rice polishing process is incompletely understood. Herein, we analyzed the distribution of lysophosphatidylcholine (LPC) molecular species with unsaturated fatty acids in rice, as their presence is thought to exert a negative effect on the flavor of sake.

The distribution of LPC molecular species in rice was visualized via matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI).

LPC (16:0) is ubiquitously present in the endosperm of rice while LPC (18:0) is localized in the core of the endosperm. In contrast, LPC (18:2) and LPC (18:1) are present in the outer region of the endosperm.

The enhancement of the quality of sake as the polishing ratio of the rice increases might be explained in terms of the distribution of LPC with unsaturated fatty acids in the rice.