Thermal, Rheological, and Surface Properties of Brewer’s Spent Grain and Its Oligo and Polysaccharides Fractions

The brewing industry produces a large amount of byproducts, primarily brewery spent grain (BSG), which mainly consists of carbohydrates, proteins, and lipids. The different fractions isolated and extracted from BSG have significant potential for waste valorization and could be used as functional products or food ingredients. In this study, specific BSG-derived fractions (Hemicellulose A, Hemicellulose B, and oligosaccharides) were isolated and characterized to evaluate their potential applications. Thermogravimetric analysis data showed that the residue at 600 °C for various fractions is approximately 20% under N₂, compared to 10% in air for BSG fractions. The rheological properties of Hemicellulose A and Hemicellulose B fractions from brewers' spent grain (BSG) exhibit high viscosity, suggesting a strong dependence on molecular weight. This characteristic implies that their elevated molecular size may play a key role in their capacity to form gels, potentially enhancing their functionality in applications requiring thickening or structural integrity. Among the BSG fractions, Hemi. It had a viscosity of >102 mPa s^-1 at a 3% (<i>w</i>/<i>v</i>) concentration, which was higher than Hemi B and oligosaccharides at the same concentration. The zeta potential of BSG fractions at various pH and concentrations was measured to assess the effects of pH and concentration. Additionally, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) revealed the surface morphology and composition of each fraction. The highest Phosphorus (P) (%) was found on the surfaces of both Hemi B and the hexane-extracted BSG. The surface elements of each fraction primarily included C, O, N, P, Ca, and Mg.