Delignification Alternatives of Spent Solid from Autohydrolysis of Vine Shoots

Abstract

Vine shoots are residues obtained from an important agricultural activity as the viticulture. Although these residues have not received much attention yet, in the recent years the employment of these residues under a biorefinery approach has increased, being possible the obtaining of products of added value as polyphenols or lactic acid for instance. Dávila et al. (2016) carried out the hydrothermal treatment in a non-isothermal regimen in a range of temperatures between 180-215 °C with a liquid/solid ratio of 8 Kg/Kg vine shoots, in order to obtain oligosaccharides which can be used as food ingredients due to their prebiotic effect. In this previous study it was observed that the optimum temperature of the treatment to obtain the maximum oligosaccharides with the minimum formation of degradation products was 201 °C. In this work, organosolv, acetosolv and alkali delignifications of the spent solid enriched in lignin and glucan were studied. The alkali delignification, using 8 w/w % of NaOH at 124°C for 105 min, was more promising than the other two treatments, being possible to remove 61% of the lignin present in the autohydrolized vine shoots. The lignin isolated in this process presented the highest content of Klason lignin (86%) and a high molecular weight (11401 g/mol) compared with the lignins isolated by applying the other delignification conditions.