Relevance of ions in pressurized fluid extraction of carbohydrates and phenolics from barley hull

• The highest phenolics extraction was obtained with pressurized aqueous ionic liquid.
• The anionic species facilitated removal of phenolics.
• The highest carbohydrates extraction was obtained with pressurized aqueous ethanol.
• A mechanism of phenolics and carbohydrates extraction based on ionic species is proposed.

The removal of total carbohydrates and phenolics from the hull of a new barley variety BT 584 using solid-liquid batch and aqueous pressurized fluid (ethanol or ionic liquid) extractions were evaluated. Using pressurized fluids, temperature was the most significant variable for the extraction of biocompounds from barley hull. The highest phenolics extraction (189.1 ± 3.1 mg/g hull) was obtained using pressurized aqueous ionic liquid while the highest carbohydrates extraction (450.3 ± 7.8 mg/g hull) was obtained using pressurized aqueous ethanol. The predicted solubility of ferulic acid and glucose in water, ionic liquid or carbonic acid, and the acid dissociation constant of the compounds studied allowed proposing an extraction mechanism based on biomass interaction with ionic species formed during pressurized fluid extraction. The anionic species facilitated removal of phenolics while the interaction of cationic/anionic species facilitated removal of carbohydrates from barley hull biomass.

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