Isomerization of various aldo-saccharides to the corresponding keto-saccharides under microwave heating using uncalcined scallop shell powder as a catalyst

• Published in: FOOD SCIENCE AND TECHNOLOGY RESEARCH Vol. 30; no. 3; pp. 305 - 311
• Main Authors: Watanabe, Yoshiyuki, Kobayashi, Takashi, Khuwijitjaru, Pramote, Adachi, Shuji
• Format: Journal Article
• Language: English
• Published: Tsukuba Japanese Society for Food Science and Technology 2024; The Japanese Society for Food Science and Technology; Japan Science and Technology Agency
• Subjects: Aqueous solutions; Calcium ions; Carbohydrates; Catalysts; Cellobiose; Disaccharides; Galactose; Heating; Hexoses; Ion concentration; Isomerization; Lactose; Lactulose; Microwave heating; Microwave oven; Pentose; Powder; rare sugar; Ribose; Saccharides; shell powder; Xylulose
• ISSN: 1344-6606; 1881-3984
• DOI: 10.3136/fstr.FSTR-D-24-00025

Fifty milliliters of 0.2 mol/L aqueous solutions containing two aldo-pentoses (ribose and xylose), two aldo-hexoses (glucose and galactose), and two aldo-disaccharides (cellobiose and lactose) were placed in a pressure-resistant vessel along with 0.5 g of uncalcined scallop shell powder and heated by a microwave oven at 700 W to isomerize the aldo-saccharides to the corresponding keto-saccharides (ribulose and xylulose, fructose and tagatose, and cellobiulose and lactulose). The yields of keto-saccharides were approximately 10 % for pentoses, 18 % for hexoses, and 25 % for disaccharides within 105 s. The selectivity from aldo-saccharide to the keto-saccharide followed the order of disaccharide > hexose > pentose. Measurements were taken for pH, calcium ion concentration, and absorbance at 280 nm and 420 nm. The acidic by-products formed during heating were neutralized by the shell powder, maintaining the pH of the reaction mixture above 7 to promote isomerization through Lobry de Bruyn–Alberda van Ekenstein transformation.