Barley hull constitutes 10-13 wt% of the barley seed. Although the hull contains high amounts of carbohydrates
and some phenolics, it lacks a high value-added application. In this study, the extraction of carbohydrates and
phenolics from BT 584 barley variety using three different extraction methods (solid-liquid, supercritical CO2
(SC-CO2), and pressurized fluid extraction methods) was investigated. The results show the effectiveness of the
sCF (pressurized aqueous ethanol) extraction over the two other extraction methods for the removal of
carbohydrates and phenolics. The effects of pressure, particle size, flow rate, temperature, static holding time,
and ethanol concentration on the extraction efficiency were studied. The optimization of the variables was
performed using response surface methodology with a central composite design. The optimal extraction was
predicted at a temperature of 180°C, 150 bar of pressure, with 12% ethanol concentration, flowing at 5 mL/min.
The amounts of phenolics and carbohydrates extracted were 81.93 mg/g and 498.11 mg/g, respectively. The
maximum yield of phenolics and carbohydrates at a temperature of 66 °C, 66% ethanol concentration, and pH of
10 using the solid-liquid extraction was approximately 13 and 12.4 mg/g barley hull, respectively. The yields of
carbohydrates and phenolics with SC-CO2 extraction using 50% ethanol as a co-solvent at 120 °C and 300 bar
were 73.4 and 67.9 mg/g barley hull, respectively. A traditional model was used to fit the curves of the sCF
extraction with a mean square error lower than 0.06. The dark color of the samples increased with an increase of
the extraction temperature, being more intense at temperatures over 180°C.