Free Amino Acid, Organic Acid and Carbohydrate Contents in Japanese Traditional Starch Syrup "Gyousen"

Abstract

Since early 18th century, starch syrup "Gyousen" has been manufactured in Kagawa Prefecture, Japan by a unique traditional procedure, that is, boiled glutinous rice is mixed with malt made from wheat cv. Seto. The mixture is then allowed to stand overnight during which starch is converted into maltose. Clarified extracts are evaporated in a stainless steel cauldron. This procedure results in final products with unique flavor. No report is available about the components responsible for the characteristics of "Gyousen". Hence, in this paper free amino acid, organic acid and carbohydrate contents were analyzed by chromatographic techniques. The samples analyzed were glutinous rice extract, residues in a jute bag, extracts immediately at the start of heating, and after 6.5 hours, the final products and starch syrup (manufactured by acid-hydrolysis) from the local market. Aspartic acid and proline were the most predominant free amino acids followed by serine and glutamic acid. Pyroglutamic acid derived from glutamic acid was 21.4mg per 100g, making up 41.2% of the total organic acids. The dextrin and glucose contents of "Gyousen" were lower than those of commercial starch syrup since there were still impurities in the "Gyousen", hence the sweet taste of "Gyousen" appeared mild in comparison with that of the commercial one.