Pressurized aqueous ethanol extraction of β-glucans and phenolic compounds from waxy barley

- Pressurized aqueous ethanol was used to extract β-glucans and phenolics.
- β-Glucans and phenolics showed opposite trends during the extraction.
- Mild conditions (< 155 °C & < 35 min) led to high molecular weight β-glucan extraction.
- Ethanol content in the solvent (< 20%) did not affect β-glucan extraction.
- Flavonoids were mainly extracted at 175 °C, with 12.5% of ethanol within 55 min.

Beta-glucans and phenolics were extracted from waxy barley using pressurized aqueous ethanol in a stirred batch reactor at 25 bar and 500 rpm. The effect of temperature (135-175 °C), extraction time (15-55 min) and ethanol content (5-20%) was evaluated. Temperature had an opposite effect on the extraction of both compounds. The higher the temperature, the lower the β-glucan extraction yield due to fragmentation, but a significant increase on the phenolic recovery was observed. Long extraction times favored the extraction of β-glucans at low temperatures and phenolics at any temperature. The ethanol content was not statistically significant on the β-glucan extraction, but helped to maintain the molecular weight of the extracted β-glucan. To obtain liquid extracts rich in high molecular weight β-glucans and phenolics, mild conditions of 151 °C, 21 min and 16% ethanol are needed, leading to 51% β-glucan extraction yield with a molecular weight of 500-600 kDa and 5 mg GAE/g barley.