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Ultrasound-assisted extraction (UAE) was used to obtain arabinoxylan (AX) from brewers' spent grain (BSG) with a higher yield, altered structural characteristics, and improved techno-functional properties. Results showed that an UAE procedure working at 400 W for 15 min under a 60% duty cycle could increase the AX yield by 52.41% compared with a traditional alkaline extraction without sonication. Concomitantly, UAE-AX developed a degraded Mw of 2741 kDa, a changed conformation of less molecular asymmetry and a decreased mean particle size from 12.56 to 4.993 μm. The rheological properties of UAE-AX aqueous solution were improved, leading to higher viscosity and gel-forming capacity of the AX stabilized emulsions. As a result, UAE-AX addition could reduce the mean droplet size to 6.40 μm and better stabilize the emulsion under various conditions than traditional alkaline extracted AX. Thus, the results proved UAE to be a promising method for extracting AX with increased emulsifying capacity from BSG. [ABSTRACT FROM AUTHOR]

The conformational properties of hydrolysates derived from brewer's spent grain protein (BSGP) pretreatment with and without ultrasound were investigated, and the effect of BSGP hydrolysate (BSGPH) supplementation on the brewer's yeast growth and fermentation performances were examined. Results demonstrated that BSGPH had substantial influences on the biomass, viability, sugar consumption, and ethanol production of yeast. Specifically, medium supplemented with hydrolysates derived from BSGP pretreated with ultrasound (UBPH) for 4-h hydrolysis (UBPH-4) increased biomass by 7.7%, viability by 9.78%, sugar consumption by 37.16%, and ethanol yields by 20.20% (v/v), respectively, compared with the blank. UBPH-4 exhibited a looser morphology and disordered secondary structure, with a decrease in α-helix and increased random coil. Meanwhile, a higher proportion of short peptides and hydrophilic amino acids in UBPH-4 might account for its preferred bioactivity. All findings revealed that UBPH were effective nitrogen sources for yeast growth and fermentation. [ABSTRACT FROM AUTHOR]

Arabinoxylan derived from brewers' spent grain was carboxymethylated, and the emulsifying capacity of carboxymethylated arabinoxylans (CMAX) with different degrees of substitution (DS) was investigated. Results showed that carboxymethylation greatly enhanced the emulsifying capacity and emulsion stability of CMAX compared to the initial arabinoxylan. CMAX developed decreased ζ-potential, higher hydrophilicity, and improved interfacial adsorption capacity. Consequently, the denser and stronger interface on the oil droplet was formed, and the stabilizing mechanism was altered. Moreover, CMAX with lower DS could effectively stabilize emulsions during storage at a concentration of 0.5 % and pH between 6 and 7. Higher DS, however, led to poorer emulsion stability and greater flocculation as a result of the fragile interface formed by excess intermolecular ionic force. The research found CMAX potential in emulsion stabilizing and further applications in food processing. [ABSTRACT FROM AUTHOR]

Ultrasound assisted extraction (UAE) was applied to enhance the extraction efficacy of protein from brewer's spent grain (BSG). The effects of ultrasonic extraction conditions including power, time and duty cycle on the techno-functional properties of protein were also evaluated. The results demonstrated that in 110 mM sodium hydroxide solution, UAE working at 250 W for 20 min under duty cycle of 60% could significantly improve the protein yield to 86.16% compared with traditional extraction without ultrasound (45.71%). The structural analysis including CD, UV–Vis, SH content results and SDS-PAGE patterns clearly showed that BSG protein was modified under ultrasonication. The extracted BSG protein increased 5.83% of β-sheet content while decreased α-helix, β-turn and random coil contents by 4.76%, 0.33% and 0.74%, respectively. Besides, SDS-PAGE pattern of protein was slightly strengthened. The enhancement in SH content and UV–Vis spectra further indicated that exposure and unfolding of protein structure occurred and thus the functional properties of BSG protein were enhanced. Indeed, fat absorption capacity, emulsifying and foaming properties of BSG protein treated by UAE were all improved except for the water absorption capacity. Thus, UAE could be a promising method to separate protein from this valuable feedstock for further utilization in the food industry. • Ultrasound assisted extraction improved the extraction efficiency of BSG protein. • The structural characteristics of BSG protein were modified after UAE. • The functional properties of BSG protein were enhanced after UAE. • UAE under continuous mode was proven to be unsuitable in BSG protein recovery. [ABSTRACT FROM AUTHOR]