Supercritical carbon dioxide and hexane extraction of wax from triticale straw: Content, composition and thermal properties

Wax and other lipophilic compounds of triticale straw were extracted with supercritical carbon dioxide (SC-CO2) and hexane. Extraction with SC-CO2 was carried out at 70 °C and a flow rate of 50 g/min at different pressures (250, 300, 350 and 400 bar) for 90 min. The yield, composition, thermal properties, and spectral features of triticale wax obtained by SC-CO2 extraction were compared with those obtained using Soxhlet extraction with hexane. The major compounds extracted with SC-CO2 and hexane from triticale straw were fatty acids (30.4–34.1%), fatty alcohols (4.8–7.4%), alkanes (7.2–8.3%), sterols (11.3–13.6%), hydroxyl-beta-diketones (5.78–11.9%), and, beta-diketones (18.2–26.9%). The differential scanning calorimetry (DSC) thermograms of each wax were considerably different. SC-CO2 and hexane extracts shared similar thermal properties, while commercial waxes showed several small peaks over a broad temperature range, indicating their eutectic nature. In contrast, purified wax from SC-CO2 (obtained at 300 bar) showed a single, sharp, narrow peak at 53 °C. Triticale wax had a higher melting point and good oxidative stability. In addition, it shared similar key thermal and spectral features with commercial waxes. The triticale wax extracted residue (dewaxed straw) obtained using SC-CO2 was composed mainly of glycans (60.4%), lignins (18.3%), ash (7.2%), acetyls (2.1%), uronic acids (1.5%) and unidentified compounds (14.1%).