A preliminary study on using ultrasounds for the valorization of spent brewer’s yeast

Abstract

Spent brewer’s yeast is a by-product rich in components with biological activity, being considered an innovative and economical viable solution for creating sustainable functional food systems. This work describes the use of ultrasound treatment, performed under various conditions, with the aim to facilitate the cell lysis and to further characterize the released cellular content of the spent brewer’s yeast. Solid residue content of the spent yeast suspensions was positively influenced by both the amplitude and the exposure time (p<0.05), reaching a maximum content (40.02±0.13 g/100 g dry yeast) at 70% amplitude, after 7.5 minutes of ultrasound treatment under pulsation mode, and the minimum after 2.5 minutes of exposure at 20% ultrasound amplitude under continuous mode (31.59±1.2 g/100 g dry yeast). The content of the soluble proteins released from the yeast cells during the ultrasound treatment under pulsation mode, reached a maximum increase at amplitude of 70%, after 7.5 minutes, being by 85% higher compared to the control represented by untreated yeast suspension. The disintegration index, Z, indicated that the maximum degree of yeast cells disintegration was obtained when applying the ultrasound treatment under pulsation mode for 5 minutes, at 50% amplitude. The antioxidant activity of the yeast extracts depended on the ultrasound conditions applied, the maximum antioxidant activity being measured in the sample exposed to ultrasound under pulsation mode for 5 minutes at 50% amplitude. In conclusion, ultrasound is a good approach to release the intracellular components from the spent brewer’s yeast. Further studies factoring ultrasounds power and frequency should be conducted, such to identify the optimum set of parameters which allow the highest release of the intracellular yeast compounds.

Proteases as Tools for Modulating the Antioxidant Activity and Functionality of the Spent Brewer’s Yeast Proteins

“…The SRC was measured on the supernatant fraction by heating the samples in a Memmert UNB 400 oven (Memmert GmbH+Co. Kg, Schwabach, Germany) to constant weight [33]. The SPC was measured on the supernatant fraction by using the Lowry method, as previously reported by Dumitrascu et al [33].…”

“…Kg, Schwabach, Germany) to constant weight [33]. The SPC was measured on the supernatant fraction by using the Lowry method, as previously reported by Dumitrascu et al [33].…”

“…The antioxidant activity of the spent brewer's yeast protein hydrolysates and of the peptide mixtures separated through ultrafiltration with membranes having cut-offs of 30 kDa, 10 kDa and 3 kDa was evaluated using the methods based on DPPH and ABTS + radicals-scavenging activity, as detailed in Dumitrascu et al [33]. The antioxidant activity was expressed as µM Trolox Equivalent (TE)/g dw yeast.…”

Phytochemical Characterization and Antibacterial Activity of Albanian Juniperus communis and Juniperus oxycedrus Berries and Needle Leaves Extracts

“…The reading of absorbance was performed at 515 nm. The protocol that followed for the ABTS radical scavenging assay was described by Dumitrașcu et al [ 20 ]. Briefly, a volume of 0.02 mL extract was added to 1.980 mL of ABTS (7 mmol), the mixture was homogenized and left in the dark for 20 min.…”

Ultrasound-Assisted Maillard Conjugation of Yeast Protein Hydrolysate with Polysaccharides for Encapsulating the Anthocyanins from Aronia

“…The ABTS + radicals-scavenging activity (ABTS + -RSA) was measured as reported by Dumitras , cu et al [16]. The results are expressed as µM Trolox equivalent/dry weight sample (µM TE/g d.w.).…”