Enhancing pressurized water extraction of β-glucan from barley grain by adding CO₂ under hydrothermal conditions

Subcritical water extraction is one of the green ways to isolate plants biomass components. In this work, it has been applied as a media to extract β-glucan from barley (Hordeum vulgare L.). The extractions were carried out at temperatures of 130-170°C and a pressures of 10-40MPa, using a semi-batch system. UV-vis spectra of liquid fraction products showed a high content of hemicelluloses, including glucan compounds. Results of FT-IR spectra analysis showed that β-glucan has been extracted from barley grains after subcritical water treatment. The elemental analysis showed that dehydration and decarboxylation occurred during subcritical water extraction of barley grains at these conditions. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of water-soluble products were approximately 500Da to 1167 kDa. To improve the extraction process, the CO₂ was added. At the same extraction time, the yield of β-glucan in the liquid fraction products increased clearly with the presence of CO₂.