| Flavonoids, namely anthocyanins and procyanidins, are health-benefitting compounds in fruits and vegetables. This project focused on flavonoids in red grape by-products because grape wastes are a plentiful low-value source of high-value compounds. The goal was to optimize three progressively more continuous extraction methods using sustainable techniques. The first extraction apparatus was static, batch-style. Optimal extraction conditions were 50--70% ethanol between 80--120°C for anthocyanins and 50% ethanol from 80--140°C for procyanidins. These conditions extracted an equivalent amount of anthocyanins and more low degree of polymerization bioavailable procyanidins compared to conventional extracts obtained with methanol- or acetone-based solvents. Skins and seeds were analyzed separately and skin, but not seed, procyanidins were effectively extracted with 50% ethanol. A sequential extraction method was effective in producing one extract high in both anthocyanins and procyanidins. The second extraction method used a semi-continuous, batch apparatus with continuously flowing pre-heated water. Optimal conditions were ∼90°C cell temperature, 9 mL/min flow rate, and 5 g crude (non-dried) sample. Results indicated 96% anthocyanin and 84% procyanidin recovery compared to conventional extracts. The third extraction method continuously extracted flavonoids using a modified expeller. Optimal conditions were 140°C water bath temperature, 65 mL/min flow rate, 50°C shaft temperature, and 20 Htz shaft rotation speed with crude pomace. Although only 58% of anthocyanins and 27% of procyanidins were recovered versus conventional extracts, the benefits of this system (continuous pomace and water flow and industrial application) are still appealing. Recovered flavonoids can be used as natural colorants or nutraceuticals. |
