BUSCADOR RECOLECTA

Flexible 100 % bio-based films were produced from discarded carrots fractions. The main ingredient was purified high molecular weight fractions of hemicelluloses and pectins previously obtained by hydrothermal treatment and ultrafiltration/diafiltration. A fraction of lignin-containing cellulose nanofibers was used as an additive. These nanofibers were obtained from the residual pulp of the hydrothermal treatment after a mechanical treatment. Low content of lignin-cellulose nanofibers (< 5 % w/w) improved oxygen permeability (up to 29 %) but worsened water vapor permeability and tensile properties. A higher addition of lignin-cellulose nanofibers (5-25 % w/w) allowed to recover the properties of the reference film (without fibers) and provided a higher hydrophobicity, increasing the water contact angle from 79.9° to 125.8°. The study of the influence of the molecular weight (67.77-102.75 kDa) and composition of the hemicellulose and pectin fraction in films containing 1 % lignin-cellulose nanofibers showed that a higher molecular weight decreased oxygen permeability (from 48.18 to 41.14 cm3·µm/m2/kPa/day), increased water vapor permeability (from 21.56 to 24.01 g·mm/m2/kPa/day) and decreased hydrophobicity (from 86.84° to 71.10°). Tensile stress was higher with higher pectin content and lower molecular weight (from 1.13 to 2.84 MPa), while elongation was higher with higher hemicellulose content (from 5.92 to 15.28 %). The obtained films had acceptable properties for food packaging and high hydrophobicity, with the great advantage of being 100 % from agri-food waste by applying environmentally friendly processes and without the need for chemical modification., Grupo de Tecnologías a Presión (PressTech), Agencia Estatal de Investigación (Gobierno de España) and FEDER Funds EU [PID2019-105975GB-I00 (MICINN/FEDER, EU)], Junta de Castilla y León - Consejería de Educación and FEDER Funds [CLU-2019-04]

Discarded carrots were valorized to obtain different films. The pulp was subjected to hydrothermal treatment (140 and 180 °C) at pilot scale, with one and with several flow-through reactors in series, allowing the extraction of pectin-containing arabinogalactan (P-AG) of very high molecular weight. Ultrafiltration and diafiltration allowed obtaining purified fractions with molecular weights be-tween 3.48-102.75 kDa. The solid residue from the hydrothermal process was subjected to mechanical treatments to obtain lignin-containing cellulose nanofibers (L-CNFs). The P-AG film had a better oxygen barrier (67.73 vs. 239.83 cm3·µm/m2/kPa/day) and the L-CNFs film had a higher tensile strength (7.74 vs. 3.14 MPa). The combination of both fractions showed that L-CNFs should be added in percentages higher than 15 % (w/w) so that their presence does not harm the P-AG based film. There was a synergistic effect on hydrophobicity when mixing both fractions, reaching a 57.5 % higher water contact angle (125.8 °). As for the P-AG sample, a higher molecular weight decreased the oxygen permeability up to 14.6 % (41.14 cm3·µm/m2/kPa/day) but increased the water vapor permeability up to 11.4 % (24.01 g·mm/m2/kPa/day). The tensile strength was up to 150.9 % higher at lower molecular weight and higher pectin content (2.84 MPa) due to the high degree of branching of the arabinogalactan. Elongation was up to 157.9 % higher at higher arabinogalactan content (15.28 %). For the first time, purified fractions of P-AG and L-CNFs from carrot waste were obtained and used for film formation. The films had acceptable properties for food-packaging., Grupo de Tecnologías a Presión (PressTech), Instituto de Bieconomía de la Universidad de Valladolid, Agencia Estatal de Investigación (Gobierno de España) and FEDER Funds EU [PID2019-105975GB-I00 (MICINN/FEDER, EU)] Junta de Castilla y León - Consejería de Educación and FEDER Funds [CLU-2019-04]