Aroma plays a decisive part in defining the organoleptic quality of the wine. Thiols are a group of volatile compounds which are particularly appreciated by consumers for they are associated with fruity flavours such as grapefruit and passion fruit. IRC7 is a β-lyase that intervenes in the metabolism of thiols. The gene can be found in wine yeast strains in four different allelic variants, of which just one is fully functional. In this thesis work two commercial yeast strains, known for their suitability to ferment both white and red wine musts, were transformed by Genome Editing using CRISPR/Cas-9 technology to convert the wildtype alleles into the functional variant in homozygosity. The transformed cells were then sequenced to verify the transformation correctly occurred and brought to the partner company laboratory to test their fermentative capacity and their ability to enrich wines of thiols. Both transformed strains were tested on different grape must substrates, in particular Sauvignon blanc, Syrah, and Cabernet sauvignon. Samples were collected from the fermented units in each test and analyzed by UPLC looking for Thiol levels. The analysis revealed a significant difference in the production of 4MMP among white and red wines, ascribable probably to the different presence of biochemical precursors among grapes and Sauvignon blanc displayed the richest aroma profile. The work was finalized by fermentation of Sauvignon blanc to compare the performances of the experimental strains against the historical data of the elective yeast strain for thiol enrichment of white wines and to draw up an evaluation form from sensorial analysis by wine experts.

Impact of IRC7 allelic configuration on S. cerevisiae fermentation properties and wine aroma profiles

STEFAN, MATTEO
2021/2022

Abstract

Aroma plays a decisive part in defining the organoleptic quality of the wine. Thiols are a group of volatile compounds which are particularly appreciated by consumers for they are associated with fruity flavours such as grapefruit and passion fruit. IRC7 is a β-lyase that intervenes in the metabolism of thiols. The gene can be found in wine yeast strains in four different allelic variants, of which just one is fully functional. In this thesis work two commercial yeast strains, known for their suitability to ferment both white and red wine musts, were transformed by Genome Editing using CRISPR/Cas-9 technology to convert the wildtype alleles into the functional variant in homozygosity. The transformed cells were then sequenced to verify the transformation correctly occurred and brought to the partner company laboratory to test their fermentative capacity and their ability to enrich wines of thiols. Both transformed strains were tested on different grape must substrates, in particular Sauvignon blanc, Syrah, and Cabernet sauvignon. Samples were collected from the fermented units in each test and analyzed by UPLC looking for Thiol levels. The analysis revealed a significant difference in the production of 4MMP among white and red wines, ascribable probably to the different presence of biochemical precursors among grapes and Sauvignon blanc displayed the richest aroma profile. The work was finalized by fermentation of Sauvignon blanc to compare the performances of the experimental strains against the historical data of the elective yeast strain for thiol enrichment of white wines and to draw up an evaluation form from sensorial analysis by wine experts.
2021
Impact of IRC7 allelic configuration on S. cerevisiae fermentation properties and wine aroma profiles
S. cerevisiae
Fermentation
Genome editing
Thiols
Wine
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12608/34587