Department of Life and Food Sciences, Obihiro University of Agriculture and Veterinary Medicine.
Fukushima Technology Centre, Aizuwakamatsu Technical Support Centre.
J Oleo Sci. 2021 Aug 5;70(8):1147-1156. doi: 10.5650/jos.ess21125. Epub 2021 Jul 9.
In plants and fungi, sphingolipids, characterized by the presence of a sphingoid base (SB), comprise neutral classes, including ceramide (Cer) and glucosylceramide (GlcCer), and acidic classes, including glycosyl inositol phosphoryl ceramide (GIPC). The major class of plant and fungal sphingolipids is GIPC; however, owing to their complicated extraction and analysis, there is still little information regarding the food characteristics of GIPC compounds. In the present study, we evaluated the content and SB composition of highly polar sphingolipids (HPS) in materials that had been obtained from our previous food processing study for GlcCer and Cer. This assessment was based on the changes that occur in HPS containing GIPC in sake rice (saka-mai) during the rice polishing and sake (rice wine) brewing process. In addition, we report a new investigation into the composition of sphingolipids in koji rice and sake yeast. HPS levels were the highest among the sphingolipid classes in brown rice cultivars and highly polished rice. Sake and sake lees (sake-kasu) were produced using three different starter cultures. In sake lees, Cer levels were the highest among the classes, while HPS was greatly reduced based on the amount of highly polished rice and koji rice, and these HPS were mainly composed of sphinganine (d18:0), which is a minor SB in highly polished rice, koji rice, and sake yeast. In addition, considerable levels of free SBs, mainly comprising d18:0, were detected in sake lees. The levels of HPS and free SBs in sake lees were dependent on the starter culture. These results suggest that HPS was hydrolyzed to Cer and that sake yeast also affected the levels of Cer and free SBs during brewing. One interesting question raised by these results is whether changes in the class and base compositions of sphingolipids during brewing contribute to taste of the final product and other food functions.
在植物和真菌中，神经酰胺（Cer）和葡糖脑苷脂（GlcCer）等中性类，以及糖基肌醇磷酸神经酰胺（GIPC）等酸性类，都以神经鞘氨醇（SB）为特征，构成了鞘脂类。植物和真菌鞘脂类的主要类别是 GIPC；然而，由于其提取和分析较为复杂，关于 GIPC 化合物的食品特性，目前仍知之甚少。本研究中，我们评估了前期 GlcCer 和 Cer 食品加工研究中所获材料中高度极性鞘脂（HPS）的含量和 SB 组成。该评估是基于 sake 米（saka-mai）在大米抛光和清酒（米酒）酿造过程中，HPS 中所含 GIPC 的变化情况。此外，我们还报告了对曲米和清酒酵母中鞘脂组成的新研究。在糙米品种和高度抛光大米中，HPS 水平在鞘脂类中最高。使用三种不同的起始培养物生产清酒和清酒酒糟（sake-kasu）。在清酒酒糟中，Cer 水平在各类别中最高，而 HPS 则基于高度抛光米和曲米的用量大幅减少，这些 HPS 主要由神经节苷脂（d18:0）组成，这是高度抛光米、曲米和清酒酵母中的一种次要 SB。此外，还检测到相当数量的游离 SB，主要由 d18:0 组成。清酒酒糟中 HPS 和游离 SB 的水平取决于起始培养物。这些结果表明 HPS 被水解为 Cer，并且在酿造过程中清酒酵母也会影响 Cer 和游离 SB 的水平。这些结果提出的一个有趣问题是，在酿造过程中鞘脂类的类别和碱基组成的变化是否会影响最终产品的口感和其他食品功能。
