Extraction of Antioxidant Phenolic Compounds from Brewer’s Spent Grain: Optimization and Kinetics Modeling

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.

Water Ultrasound-Assisted Extraction of Polyphenol Compounds from Brewer’s Spent Grain: Kinetic Study, Extract Characterization, and Concentration

“…In the literature, an increase in extraction yield was also observed by solvent bath extraction (maceration) for 60 min when using a 70% ethanol aqueous mixture at 60 • C with values of 2.59, 2.74, and 3.07 mg GAE/g BSG,dry at 10, 20, and 30 mL solvent /g BSG,dry , respectively [17]. These authors explained that higher liquid/solid ratio implies higher concentration gradient between the solid and the bulk of the liquid, resulting in a greater driving force for diffusion of compounds to the solvent and higher extraction efficiency.…”

“…Therefore, water could create a more polar medium that facilitates the extraction of phenolic compounds. Water and mixtures with low ethanol concentration could access to cells, but high concentration of ethanol could cause protein denaturation, preventing the dissolution of polyphenols, and then influencing the extraction [17]. Socaci et al [2] found that an increase in ethanol concentration from 60% to about 68% increased TPC extraction while higher ethanol concentration led to a gradual decrease in TPC.…”

Optimization of Sonotrode Ultrasonic-Assisted Extraction of Proanthocyanidins from Brewers’ Spent Grains

“…The results obtained by the US sonotrode at the optimal conditions were compared with a PC extract from BSGs obtained via conventional solid/liquid extraction. The extraction methodology was carried out according to Carciochi et al [27]. Briefly, BSGs were subjected to mechanical agitation with a w / v ratio of 1/30, temperature of 80 °C, 72/28 ethanol/water ( v / v ), and an extraction time of 60 min.…”

Simultaneous production of lignocellulolytic enzymes and extraction of antioxidant compounds by solid-state fermentation of agro-industrial wastes

“…The extraction of phenolic compounds from BSG was lower, A. niger CECT 2915 achieved the maximum extraction of TPC 1.86 ± 0.11 mg CAE/gds. However, the extraction was the same order to other extraction techniques as ultrasounds and microwaves 4.11 and 3.91 mg gallic acid equivalent/gds in ethanol:water extracts, respectively (Carciochi et al, 2018). The phenolic compounds of BSG are linked to hemicellulose and lignin fraction, however the action of enzymes produced during SSF not allowed their extraction.…”