Brewery waste as a potential source of phenolic compounds: Optimisation of the extraction process and evaluation of antioxidant and antimicrobial activities

This paper reports the development of an extraction process that allows selective recovery of polyphenols from a brewery waste stream. The antioxidant activity of this extract (EC50 = 0.23–0.3 g/L) was very high, similar to that of butylated hydroxyanisole (BHA) and higher than that of other synthetic antioxidants such as butylated hydroxytoluene (BHT). Crude extracts exhibited a high level of antimicrobial activity against Gram-positive and Gram-negative bacteria, when applied at concentrations of 1% and 3% (w/v). The antioxidant and antimicrobial activities can probably be attributed to the major phenolic compounds, such as protocatechuic, caffeic, p-coumaric and ferulic acids and catechin. With this procedure, the waste polyphenols could be used as cheap source of natural compounds, with potential applications in the food and health sectors. Substitution of synthetic additives with safe and effective natural additives may be of further benefit to the food industry.