Hydrothermal fractionation of grape seeds in subcritical water to produce oil extract, sugars and lignin

• Grape seeds as a model compound for hydrothermal treatment and extraction.
• Multi-step temperature hydrolysis from 150 to 340 °C feasible for biomass fractionation.
• High lignin purity in the residual solid >90%.
• Extraction of 50–62% of sugars (0.20–0.23 g/g-grape).

In this work, the fractionation of grape seeds as a model biomass was studied using a combination of two processes: solvothermal extraction and hydrothermal fractionation-hydrolysis process in a semicontinuous reactor. First, grape seeds were subjected to an extraction process with ethanol/water (70/30 wt.%) at 90 °C during 60 min obtaining ca. 13.0 wt.% of oil and extractable components with 4.46 wt.% of polyphenols (66% of the maximum). Afterwards, the solvent was water and the biomass was treated in steps at different temperatures (150 °C to 340 °C). During the hydrolysis the pH decreased from 5.5 down to 3.0 due to acetyl group liberation. The total quantity of recovered sugars varied around 20.0 to 23.1 wt.%. The best experimental condition for obtaining the maximum amount of pentoses + hexoses + oligosaccharides was 180 °C (45 min) + 250 to 265 °C (45 min) + 330 to 340 °C (45 min).

Figure optionsDownload high-quality image (177 K)Download as PowerPoint slide