Comparative analysis of functional components in Sakekasu (Sake lees)

Background: Sake lees (Sakekasu), a byproduct of sake production, has been recently attracting attention as a functional food. Sakekasu is rich in nutrients and contains glycerophosphocholine (GPC) and S-adenosylmethionine (SAM), which are well-known functional compounds. The content of these compounds in Sakekasu depends on a variety of factors, including fermentation conditions, especially the method and length of ripening. These differences are reflected prominently in the color of Sakekasu, which becomes darker due to the long ripening period and high drying temperature.Objective: This study aimed to clarify the contents of functional components in Sakekasu with different color tones (i.e., ripening period).Methods: Three types of Sakekasu with different color tones (white, ocher, and brawn) were collected from several breweries. The contents of multiple functional components in their extracts were determined by liquid chromatography coupled to high resolution ion-trap/time-of-flight mass spectrometry.Results: Sakekasu with white color had more abundant GPC, SAM, and fatty acids than those with darker color. However, ethyl glucoside and glyceryl glucosides did not differ significantly by color tone. Furthermore, the Maillard reaction products of sugar and dipeptide were mainly found in dark-colored Sakekasu, and their structures were annotated by tandem mass spectrometry. Conclusions: This study has clarified many functional compounds in Sakekasu in relation to color tone (i.e., ripening period) and highlighted the potential of Sakekasu with white color tone as a functional food.