Public Thesis defense - LIBST

Identification des défauts majeurs des bières sans alcool et recherche de voies novatrices visant à l’amélioration de leur qualité by Margaux SIMON

Pour l’obtention du grade académique de Doctorat en Sciences agronomiques et Ingénierie biologique

By using various GC and HPLC sensitive techniques, the aim of this work was to assess the quality and stability of a panel of Belgian commercial NABLABs, either issued from physical or from biological processes. The use of low-density worts, strong pasteurization or vacuum distillation techniques can explain their prematured oxidation. Their reduction power (ORAC and TINH methods) confirmed to be half that of conventional beers. Three oxidation-derived odorants usually present in a six-months lager emerged as to be flavor-active in most fresh samples: sotolon, methional, and phenylacetaldehyde, together with dimethyltrisulfide and β-damascenone. Abhexon was also found in higher amount after aging, especially in limited fermentation products. During aging, isohumulones and flavan-3-ols were strongly degraded, resulting in unpleasant astringency, more color, and colloidal instability. Additionally, we evidenced a huge lack of dimethylsulfide in all NABLABs, whatever the process used. This contributor to the typical lager aroma is known as a fruity perception enhancer. Optimized dry hopping, maltose-negative microorganisms able to produce higher amounts of pleasant polyfunctional thiols, and alternative cereals or unusual botanical ingredients here appear as promising options to increase both fruity flavors and resistance to oxidation.

Jury members :

• Prof. Sonia Collin (UCLouvain), Supervisor
• François Chaumont (UCLouvain), Chaiperson
• Prof. Michel Ghislain (UCLouvain), Secretary
• Prof. Stéphanie Marchand (Univ. Bordeaux, Fr.)
• Ir. Pablo Alvarez (CBS Brew, Belg.)
• Dr. Jacques Gros (AB-INBEV, Belg.)
• Ir. Philippe Janssens (FERMENTIS, Fr.)

Pay attention : the public defense of Margaux SIMON will also take place in the form of a videoconference

Télécharger l'annonce