Psicose

DescriptionD-Psicose, an epimer of d-fructose at position C3, is a rare sugar found in extremely small quantities in commercial carbohydrates or agricultural products. Psicose has been found in wheat, Itea plants, and processed cane and beet molasses. It is also present in small quantities in commercial complexes of d-glucose and d-fructose. It is 70% as sweet as sucrose (when compared to 10% solutions), and the caloric value is reported to be 0.007 kcal/g. Psicose is poorly absorbed in the digestive tract and has zero energy for growth; therefore, it may be useful as a low-calorie sweetener.

PreparationPsicose is manufactured commercially using d-psicose-3-epimerase from A. tumefaciens. A fructose solution is treated with immobilized, nonviable C. glutamicum cells harboring the enzyme, and it takes 4–8 h at 50°C to convert fructose to psicose. The psicose solution is purified with active carbon, ion exclusion chromatography, and crystallization.