Department of Life and Food Science, Obihiro University of Agriculture and Veterinary Medicine.
Fukushima Technology Centre, Aizuwakamatsu Technical Support Centre.
J Oleo Sci. 2021 Feb 1;70(2):203-212. doi: 10.5650/jos.ess20234. Epub 2021 Jan 15.
Sphingolipids, including ceramide (Cer) and glucosylceramide (GlcCer), have the characteristic structural units called sphingoid bases, and are constituents of cell and vacuole membranes. Plant sphingolipids bear highly diverse base structures and the base composition differs depending on the plant species. It is thought that the composition of sphingolipid classes and sphingoid bases is related to membrane fractions. However, there is little information about differences in sphingolipids among plant cultivars and the changes occurring in sphingolipids during food processing. This study investigated sphingolipids in sake rice (saka-mai) cultivars grown for sake (rice wine), and the changes in sphingolipids during polishing and brewing. In six brown rice samples, there were no large differences of the base composition among Cer or GlcCer of cultivars, whereas there were differences in their sphingolipid contents. When compared to brown rice, highly polished rice contained lower levels of sphingolipids, especially Cer. For three rice brans from different polishing steps, the Cer content was higher in the outer bran than in the inner bran. Sake and sake lees (sake-kasu) were produced by three different starter cultures (shubo preparations: the mixture of koji rice as an enzyme cocktail containing amylases, sake yeast, and adding rice as a carbohydrate source). The Cer/GlcCer ratio in sake and sake lees depended on the starter culture; Cer and GlcCer in sake lees possessed a fungi-specific base, 9-methyl-trans-4,trans-8- sphingadienine. In addition, sake lees had a higher Cer/GlcCer ratio when compared to highly polished rice as a sake source. These results suggest that the sphingolipid content of brown rice differs depending on the rice cultivar; further, the sphingolipids and the sphingolipid composition in sake and sake lees are affected by fungal sphingolipids and self-digestion during brewing.
鞘脂类，包括神经酰胺（Cer）和葡萄糖神经酰胺（GlcCer），具有称为神经酰胺碱基的特征结构单元，是细胞和液泡膜的组成部分。植物鞘脂类具有高度多样化的碱基结构，碱基组成因植物物种而异。据认为，鞘脂类和神经酰胺碱基的组成与膜部分有关。然而，关于不同植物品种间鞘脂类的差异以及在食品加工过程中鞘脂类的变化，信息很少。本研究调查了用于酿造清酒（米酒）的清酒米（saka-mai）品种中的鞘脂类，以及抛光和酿造过程中鞘脂类的变化。在六个糙米样品中，品种间 Cer 或 GlcCer 的碱基组成没有很大差异，但鞘脂类含量存在差异。与糙米相比，高度抛光的大米含有较低水平的鞘脂类，尤其是 Cer。对于来自不同抛光步骤的三种米糠，外糠中的 Cer 含量高于内糠。清酒和清酒酒糟（sake-kasu）是由三种不同的起始培养物（shubo 制剂：含有淀粉酶的曲米作为酶混合物、清酒酵母和添加的大米作为碳水化合物来源）制成的。清酒和清酒酒糟中的 Cer/GlcCer 比值取决于起始培养物；清酒酒糟中的 Cer 和 GlcCer 具有真菌特异性碱基，即 9-甲基-反式-4,反式-8- 神经鞘氨醇。此外，与清酒来源的高度抛光大米相比，清酒酒糟具有更高的 Cer/GlcCer 比值。这些结果表明，糙米的鞘脂类含量因水稻品种而异；此外，清酒和清酒酒糟中的鞘脂类和鞘脂类组成受真菌鞘脂类和酿造过程中自我消化的影响。
