Development and characterization of functional ingredients through valorization from brewer's spent grain

Research output: Types of ThesisDoctoral Thesis



The main objective of this thesis was to explore the value of the by-product of beer production, BSG, to promote the principle of sustainable development by obtaining value-added ingredients. So, from this residue, extractions were carried out using solid-liquid and ohmic heating extractions and solvents used in the food industry (ethanol and water) (to guarantee the maintenance of compositional integrity, functionality and safety of the bioactive extracts obtained). All hydroethanolic extracts showed high antioxidant capacity, and the highest values were obtained for the extract 60% ethanol:water (v/v). Identification by HPLC showed that catechin and vanillin were the main compounds identified with the highest concentration (223.6 e 109.2 μg/g BSG respectively) obtained by extraction using 60% ethanol:water (v/v). In the biological activity assays, the extracts proved to be multifunctional (antihypertensive capacity, antibacterial and antibiofilm activity). All were non-genotoxic, but cytotoxicity was dependent on extract concentration, with totally safe application for all extracts up to 1 mg/mL. In the antioxidant extracts obtained by ohmic heating 4-hydroxybenzoic acid was the compound that showed the highest concentration (125.86 μg/ g drêche) and the 60% ethanol extract:water (v/v) was the one that showed the highest antioxidant activity. However, both extracts showed no mutagenic activity, and both were able to inhibit 50% of the angiotensin-I converting enzyme (ACE), with the extract with the best result being 80% ethanol:water (v/v). The BSG extracts showed an inhibitory effect against Bacillus cereus and to a lesser extent against Listeria monocytogenes, at 5.00 and 2.50 mg/mL, for 80% ethanol:water (v/v) and 60% ethanol:water (v/v). v) respectively, and also, the same concentrations inhibited biofilm formation. The gastrointestinal tract (GID) analysis showed that the solid-liquid method containing 60% ethanol:water (v/v) was the extraction with the highest antioxidant activity and the highest content of total phenolics. However, the compounds present in the extract obtained by ohmic heating with 80% ethanol:water (v/v) showed higher values of bioaccessibility indexes for polyphenols. All extracts increased the growth of the probiotic microorganisms tested The flours resulting from solid-liquid extraction and ohmic heating were studied along the GID showing that after an initial decrease there was an increase in antioxidant activity and total phenolic compounds along the GID These flours also positively modulated the growth of probiotic bacteria as well as their metabolism with the production of short chain fatty acids.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Minho
  • Faculty of Biotechnology
  • University of Aveiro
  • Teixeira, José António, Supervisor, External person
  • Pintado, Maria Manuela, Co-supervisor
Award date14 Dec 2022
Publication statusPublished - 14 Dec 2022
Externally publishedYes


  • Antioxidant activity
  • Gastrointestinal tract
  • Microbiota
  • Ohmic heating
  • Solid-liquid extraction


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