Fractionation and purification of bioactive compounds obtained from a brewery waste stream

Abstract

The brewery industry generates waste that could be used to yield a natural extract containing bioactive phenolic compounds. We compared two methods of purifying the crude extract-solid-phase extraction (SPE) and supercritical fluid extraction (SFE)--with the aim of improving the quality of the final extract for potential use as safe food additive, functional food ingredient, or nutraceutical. The predominant fractions yielded by SPE were the most active, and the fraction eluted with 30% (v/v) of methanol displayed the highest antioxidant activity (0.20 g L(-1)), similar to that of BHA. The most active fraction yielded by SFE (EC50 of 0.23 g L(-1)) was obtained under the following conditions: temperature 40 °C, pressure 140 bar, extraction time 30 minutes, ethanol (6%) as a modifier, and modifier flow 0.2 mL min(-1). Finally, we found that SFE is the most suitable procedure for purifying the crude extracts and improves the organoleptic characteristics of the product: the final extract was odourless, did not contain solvent residues, and was not strongly coloured. Therefore, natural extracts obtained from the residual stream and purified by SFE can be used as natural antioxidants with potential applications in the food, cosmetic, and pharmaceutical industries.

Figure 1

Schematic representation of the brewing process, extraction, and purification of the PVPP-WS extract containing bioactive compounds.

Figure 2

Chromatograms acquired at 280 nm  by HPLC-DAD-UV. (a) Chromatogram of the crude extract without fractionation process. (b) Chromatogram of the residue of the crude extract that remains in the extraction cell after the fractionation process (E_Cell). (c) Chromatogram of the fraction obtained under optimal conditions (E₁₄₀).