Production of rare sugars from common sugars in subcritical aqueous ethanol

• Published in: Food chemistry 2015-05, Vol.175, p.465-470
• Main Authors: Gao, Da-Ming, Kobayashi, Takashi, Adachi, Shuji
• Format: Article
• Language: English
• Subjects: Carbohydrates - chemical synthesis; Carbohydrates - chemistry; d-Ribulose; d-Tagatose; d-Xylulose; Ethanol; Ethanol - chemistry; Ethyl alcohol; Foods; Hexoses - chemistry; Isomerization; Ketoses - chemical synthesis; Ketose–aldose isomerization; Pentoses - chemistry; Productivity; Subcritical aqueous ethanol; Sugars; Xylulose - chemistry
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2014.11.144

•Tagatose, xylulose, and ribulose were synthesized using subcritical aqueous ethanol.•An increase in ethanol concentration significantly accelerated the isomerization reaction.•The maximum productivity of d-tagatose was ca. 80g/(Lh).•Both 2,3-threo and 2,3-erythro aldoses could be converted to the corresponding C-2 ketoses. A new isomerization reaction was developed to synthesize rare ketoses. d-Tagatose, d-xylulose, and d-ribulose were obtained in the maximum yields of 24%, 38%, and 40%, respectively, from the corresponding aldoses, d-galactose, d-xylose, and d-ribose, by treating the aldoses with 80% (v/v) subcritical aqueous ethanol at 180°C. The maximum productivity of d-tagatose was ca. 80g/(Lh). Increasing the concentration of ethanol significantly increased the isomerization of d-galactose. Variation in the reaction temperature did not significantly affect the production of d-tagatose from d-galactose. Subcritical aqueous ethanol converted both 2,3-threo and 2,3-erythro aldoses to the corresponding C-2 ketoses in high yields. Thus, the treatment of common aldoses in subcritical aqueous ethanol can be regarded as a new method to synthesize the corresponding rare sugars.