Abstract
The kinetics of polyphenol extraction from brewer’s spent grain (BSG), using a batch system, ultrasound assistance, and microwave assistance and the evolution of antioxidant capacity of these extracts over time, were studied. The main parameters of extraction employed in the batch system were evaluated, and, by applying response surface analysis, the following optimal conditions were obtained: Liquid/solid ratio of 30:1 mL/g at 80 °C, using 72% (v/v) ethanol:water as the solvent system. Under these optimized conditions, ultrasound assistance demonstrated the highest extraction rate and equilibrium yield, as well as shortest extraction times, followed by microwave assistance. Among the mathematical models used, Patricelli’s model proved the most suitable for describing the extraction kinetics for each method tested, and is therefore able to predict the response values and estimate the extraction rates and potential maximum yields in each case.
Highlights
Brewer’s spent grain (BSG) is the solid fraction that remains following wort production, which is the first step of the brewing process
Phenolic compounds extracted from brewer’s spent grain (BSG) ranged from 1.59 to 3.57 mg gallic acid equivalents (GAE)/g, whereas antioxidant activity varied between 1.86 and 11.93% of DPPH radical inhibition
A value of 20 mg GAE/g dry weight (DW) for Total phenolic compounds (TPC) assay was reported by Moreira [1] using an optimized microwave-assisted method under alkaline conditions, showing an advantage of these novel extraction techniques compared to conventional ones
Summary
Brewer’s spent grain (BSG) is the solid fraction that remains following wort production, which is the first step of the brewing process. BSG is the main by-product from breweries, representing about 20 kg per hectoliter of beer produced [1] This source is rich in oligo- and polysaccharides, as well as in polyphenols, which are widely recognized as having antioxidant and antiradical properties [2]. Extraction is the initial and most important step in the recovery and purification of bioactive compounds from plant materials. Many factors such as solvent composition, extraction temperature and solvent-to-solid ratio, may significantly influence the extraction efficiency, antioxidant activity and phenolic content. The traditional method of optimization (OVAT, one variable at a time) is laborious and time-consuming, since only a single factor at a time is taken into consideration
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