Table 2.
Data concerning delignification and lignin fractions obtained. Delignification % of the GSWE-red and GSWE-white samples and sugar analysis of GSWE treated with NaOH 1% (w/v) tested with two reaction times 15 and 60 min. Yields (%) and purity of lignin obtained from grape stalks without extractives using water (GSWE) or water plus ethanol (GSWEE) procedures.
| Delignification process | ||||
| Time of process | % Delignification | |||
| GSWE-red | GSWE-white | |||
| 15 min | 47.81 ± 2.61 | 42.04 ± 2.02 | ||
| 60 min | 50.61 ± 1.62 | 45.58 ± 0.86 | ||
| Compounds (monosaccharides) | % Sugars in DGS samples | |||
| with 60 min | ||||
| Glucose | 43.79 ± 5.92 | 26.33 ± 6.58 | ||
| Xylose | 16.38 ± 2.50 | 9.54 ± 1.42 | ||
| Arabinose | 0.38 ± 0.07 | N.D. | ||
| Total | 60.55 | 35.87 | ||
| Dried lignin fractions | ||||
| Material | Yield (%, w/w) | Purity (%, w/w) | ||
| Freeze dry | Precipitation | Freeze dry | Precipitation | |
| GSWE-red | 9.23 | 1.4 | 40.84 | 70.57 |
| GSWEE-red | 1.48 | 1.15 | 30.08 | 67.91 |
| GSWE-white | 9.47 | 1.98 | 56.02 | 73.73 |
| GSWEE-white | 1.42 | 4.27 | 39.5 | 67.01 |
* N.D.: Not detected; Sugars data are yields of components (g) per 100 g of oven-dried grape stalk. GSWE: Grape stalk water extracted, GSWEE: Grape stalk water and ethanol extracted.