A study of bioactive compounds of wine production residues of some red grapes common in Georgia and the perspective of using the obtained preparations

Historically, Georgia is a winemaker country (about 8000-year-old history). Wine has been made by several methods, which manifests in different times of fermentation of seeds and juice, which in turn affects the chemical composition of wastes after winemaking. Despite more than 500 cultivated species existing in Georgia, wastes after wine production are unexplored and unused. Therefore, our goal was to study the chemical composition of the post-production waste of some industrial red wine varieties by HPLC, UPLC-PDA, and MS methods and to obtain hydrophilic, alcoholic, and hydrophobic extractions and preparations by several methods: supercritical fluid extraction (SFE), ultrasonic extraction (US), cold press extraction, and high-pressure and temperature extraction.

Obtained preparations were different by chemical composition and antioxidant activity in different forms of grapes. The contents of total phenolics in Ojaleshi, Saperavi, and Otskhanuri Sapere skin were 7.085 g/kg, 9.71 g/kg, and 11.280 g/kg in dry mass; corresponding antioxidant activities were - 0.72, 0.44, and 0.37 units (0.1mM DPPH 50% inhibition mg of samples). In seeds of Ojaleshi, Saperavi, and Otskhanuri Sapere, the content of total phenolics was 5.472 g/kg, 7.572 g/kg, and 10.447 mg/kg in dry mass; corresponding antioxidant activities were 1.02, 0.65, and 0.52 units (0.1 mM DPPH 50% inhibition mg of samples). The yield of preparations of phenolics obtained from grape skin was 10-15%; from grape seeds, it was 14-18%. The yield from seeds' oil was 17-22%.

The produced oil was compared with the oil obtained by the extraction of the classic Soxhlet method.

Palmitic acid (C16:0), Stearic acid (C18:0), Oleic acid (C18:1), Linoleic acid (C18:2 cis-9), and Linolenic acid (C18:3) have been identified in the obtained oil.