Saccharides are sweet, water-soluble carbohydrates which are divided into monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Saccharides used as raw materials for seishu include glucose, mizu-ame (starch syrup) and hydrolyzed starch from rice or other sources.

Glucose is the smallest unit resulting when starch is hydrolyzed. When used as a subsidiary ingredient, it is in the form of liquid glucose with a water content of about 30%, or crystalline glucose with a moisture content of about 10%.

Mizu-ame starch syrup is made during the manufacture of glucose, when hydrolysis is stopped in order to keep the ratio of glucose and other saccharides to at a fixed level. It is commonly a viscous liquid containing 25% water and 50% saccharides.   This can be dried to give a powder with about 3% water content.