Solubility of carbohydrates in supercritical carbon dioxide with (ethanol + water) cosolvent

Prebiotic carbohydrates are defined as non-digestible carbohydrates that beneficially affect the host by selectively stimulating the growth and/or activity of a limited number of bacteria in the colon.The present study is focused on two prebiotic ketosugars: tagatose and lactulose, which are currently obtained by alkaline isomerization of their respective aldoses—galactose and lactose. It is a part of a broader research devoted to examining the possibility of complex solid carbohydrate mixtures fractionation using supercritical carbon dioxide and alcohol-type cosolvents. We report new experimental solubility data of tagatose, galactose, lactulose and lactose in supercritical carbon dioxide with ethanol:water (95:5, v/v) used as a cosolvent at T = (60 and 100) °C, P = (10–30) MPa and cosolvent content from 6 to 21% (w/w). The solubility measured was in the range (0.02–1.09) mg g−1. Additionally, the experimental data was correlated using the Soave–Redlich–Kwong cubic equation of state with the modified Huron-Vidal second order (MHV2) mixing rule. The latter employs the mS-UNIFAC, which introduces two new groups in the original UNIFAC parameter matrix to represent the sugar molecules.

Graphical abstractSolubility data of tagatose, galactose, lactulose and lactose in SC-CO2 with ethanol:water (95:5, v/v) as modifier at 60–100 °C and 100–300 bar is reported. The experimental data was correlated using the Soave–Redlich–Kwong equation of state with the modified Huron-Vidal second order (MHV2) mixing rule, and the mSUNIFAC with its new groups to represent the sugar molecules.Figure optionsDownload full-size imageDownload as PowerPoint slide