Obtenção e análise de óleo e compostos fenólicos de sementes de diferentes variedades de uva (Vitis vinifera e Vitis labrusca) cultivadas no Rio Grande do Sul

Abstract

Brazil is known as a country of great agricultural activity, but also produces a large amount of agro-industrial residues. On this basis, the seek for alternatives to the use of residual organic matter is increasing. The expected development of the vineyard area will increase the volume of waste and the consequent accumulation of byproducts will probably become a considerable environmental problem. These wastes are usually burned out, although they sometimes are used as fertilizer or to feed the cattle, but the seeds contain a variety of biologically active substances that are wasted, such as phenolic compounds, fatty acids and tocopherol. These compounds are important in the treatment and prevention of cardiovascular disease, and act against oxidation of LDL (Low-density lipoprotein). Considering these affirmations, the major aim of this study was to perform the extraction of oil and phenolic compounds extract from grape seeds collected from winemaking waste, using the technologies of supercritical carbon dioxide extraction and Soxhlet apparatus. To this study were selected residues from Vitis labrusca (Isabel and Bordô varieties) and Vitis vinifera (Cabernet Sauvignon, Merlot and Moscato Giallo varieties), both belonging to the harvest of 2005 and 2006, from wineries located in Caxias do Sul. The extractions were performed in Soxhlet with hexane during 6 hour for oil, and with ethanol 70% during 8 hour for extract. The extractions were carried out with supercritical CO2 at 80°C, CO2 flow rate of 69g/min, 250bar pressure and 1 hour for oil extraction. To the extract, the parameters used were 60°C, CO2 flow rate of 76g/min, 225bar pressure, 3% ethanol as cossolvent and 1 hour of extraction. The extracted compounds were analyzed by gas and liquid chromatography and by spectrophotometric methods. It was observed that in general, the varieties of Vitis labrusca (Isabel and Bordô) had higher concentrations of fatty acids in comparison to the varieties of Vitis vinifera (Cabernet Sauvignon Merlot and Moscato Giallo), demonstrating the great potential of these more rustic varieties, which are still underexplored. On the other hand, the varieties of V. vinifera showed higher concentrations of phenolics compounds in comparison to the varieties of V. labrusca. With regard to the extraction methods, the supercritical extraction of grape seed oil proved to be very similar to the Soxhlet extraction, with the advantage of the absence of organic solvents during process and less extraction time, being a promising method for extraction of grape seed oil from the tested varieties. To the extract with higher amounts of phenolic compounds, the best extraction method was the one conducted in Soxhlet. In general, the harvest of 2006 showed the highest concentrations of the compounds evaluated in comparison to the harvest of 2005. The experimental data suggest the use of residual biomass of the wine industry as an alternative source of phenolic compounds, α-tocopherol and fatty acids. Therefore, a new source of exploitation, is reported especially in the herbal, cosmetics and food industry.