Phenolic profile of cold-pressed grape seed oil from Teran red grape variety (Vitis vinifera L.): Impact of pre-fermentative mash cooling, heating, and prolonged macerations

This study aimed to determine total phenolic content and concentrations of individual phenolics in cold-pressed grape seed oil obtained by screw pressing of grape seeds of cv. Teran (Vitis vinifera L.). Those seeds derived from six different vinification treatments that were submitted: to 48-h pre- fermentative mash cooling (8 °C) followed by maceration of 13 days (C15), 28 days (C30) and saignée technique followed by maceration of 13 days (CS15), and to 48-h pre- fermentative heating (50 °C) followed by maceration of 13 days (H15) and 28 days (H30). Also, this experiment included a control tank (K7), with a 7- day maceration. After macerations ended, fermented mashes were pressed, and seeds were collected and dried at 38 °C in dehydrating chamber until 5-8 % of moisture content in seeds was reached. Then they were vacuum-packed and stored until screw pressing. The obtained oil was centrifuged and stored at -18 °C prior to analysis. Total phenolic content (TPC) was analyzed by Folin–Ciocalteau colorimetric method and UV/VIS spectrophotometer. Individual phenolic compounds were analyzed by high-performance liquid chromatography (HPLC). Results showed that total phenolic content (mgCAEkg-1 oil) in oil from all treatments, except C15, was significantly higher compared to oil from the control treatment (K7). Respectively, TPC increased with longer duration of maceration. Regarding individual phenolics, it was found that resveratrol, tyrosol, quercetin and kaempferol were significantly the highest in oil from pre-fermentative heating treatment (H30). Obtained results suggested a noticeable impact of pre fermentative treatments and prolonged macerations on phenolics in cold-pressed grape seed oil.