Zaima Nobuhiro, Yoshimura Yukihiro, Kawamura Yukio, Moriyama Tatsuya
Department of Applied Biological Chemistry, Graduate School of Agriculture, Kinki University, Nara, 631-8505, Japan.
Rapid Commun Mass Spectrom. 2014 Jul 15;28(13):1515-20. doi: 10.1002/rcm.6927.
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.
清酒由发酵的大米制成，在日本已有1000多年的饮用历史。大米在发酵前必须进行打磨以获得高品质的清酒。传统观点认为，随着大米打磨率（打磨过程中去除的百分比）的提高，清酒的品质会得到提升。然而，大米打磨过程的潜在化学原理尚未完全被理解。在此，我们分析了大米中含有不饱和脂肪酸的溶血磷脂酰胆碱（LPC）分子种类的分布情况，因为它们的存在被认为会对清酒的风味产生负面影响。
通过基质辅助激光解吸/电离质谱成像（MALDI-MSI）观察大米中LPC分子种类的分布。
LPC（16:0）普遍存在于大米胚乳中，而LPC（18:0）则定位于胚乳核心。相比之下，LPC（18:2）和LPC（18:1）存在于胚乳的外层区域。
大米打磨率提高时清酒品质提升，这或许可以从大米中含有不饱和脂肪酸的LPC分布情况来解释。
