Extracts were obtained from grape stems of Mazuelo variety from the Estación de Viticultura y Enología de Navarra, in northern Spain (2016 harvest). Prior to extraction, the stems were oven dried (Ing Climas, Barcelona, Spain) at 25 °C until constant weight. They were subsequently ground in a coffee grinder (Moulinex, Ecully, France) and passed through a 300 µm sieve. To obtain the grape stem extract, the dried and ground stem was macerated in 50% v/v ethanol/water (solid/solvent ratio 1:100, w/v), for 24 h at 40 °C. After the incubation, the extracts were centrifuged (8000 rpm for 15 min), filtered and lyophilized. The characterization of the extract thus obtained was published in a previous work [8 (link)]. To perform the stability study, 50 mg of the lyophilized extract were stored in transparent (T) and in amber vials (A), at 25 °C and 40 °C for 6 months. The samples were stored under fluorescent lamps. Nine replicates were performed for each of the conservation conditions studied, and three vials of each type were taken every two months for characterization. At the end of each storage period, the samples were kept at −20 °C for subsequent analysis. Prior to analysis, the lyophilized extract in each vial was reconstituted in 10 mL of methanol.
Free full text: Click here
