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Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine
Thesis (MSc)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613902668300288 |
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| access_status_str | Open Access |
| author | Roodt, Xander |
| author2 | Du Toit, Wessel Johannes |
| author_browse | Du Toit, Wessel Johannes Roodt, Xander |
| author_facet | Du Toit, Wessel Johannes Roodt, Xander |
| author_sort | Roodt, Xander |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132461 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:31.605Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132461 Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine Roodt, Xander Du Toit, Wessel Johannes Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture & Oenology & Institute for Wine Biotechnology. Wine and wine making -- Chemistry Fermented beverages Shiraz (Wine) -- Composition Wine -- Flavor and odor Cabernet (Wine) -- Composition Oxygen Red wines -- Oxidation UCTD Thesis (MSc)--Stellenbosch University, 2025. Roodt, X. 2025. Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/63b9c480-f32f-4181-801d-33989df79888 ENGLISH ABSTRACT: This study investigated the impact of controlled oxygen additions during alcoholic fermentation on the chemical and sensory profiles of Shiraz wines across two vintages and Cabernet Sauvignon from a single vintage. Oxygen management during alcoholic fermentation plays a crucial role in shaping wine aroma, flavour, and mouthfeel. The research aimed to explore how controlled oxygen exposure during alcoholic fermentation can enhance wine quality by improving aroma, reducing “reductive” off-aromas, and mitigating risks such as the formation of “oxidized” off aromas. Low and high oxygen additions were applied during alcoholic fermentation, followed by detailed chemical and sensory analyses. Phenolic analysis revealed consistent reductions in MCP tannin concentrations under high oxygen additions in Shiraz wines across two vintages, while Cabernet Sauvignon wines exhibited minimal tannin changes, reflecting cultivar-specific oxidative responses. HPLC analysis showed a stable mean degree of polymerization (mDP) and average molar mass, suggesting that oxygen primarily altered tannin subunit composition rather than polymer size. Sensory evaluation revealed a decrease in “reductive” off-aromas and enhanced red fruit attributes in Shiraz wines exposed to oxygen during alcoholic fermentation, with no significant changes in mouthfeel. Conversely, Cabernet Sauvignon showed minimal sensory differences, highlighting the need for tailored oxygenation strategies. Principal component analysis (PCA) further clarified the relationship between sensory attributes and oxygen treatments. Interestingly, even under high oxygen additions, which are difficult to replicate in practical winemaking, no detectable “oxidative” aroma attributes were observed. This was supported by stable acetaldehyde levels across all treatments for all experiments, indicating that oxygen exposure did not trigger oxidation processes strong enough to produce typical “oxidative” off-aromas. These findings demonstrate the potential of controlled oxygen additions during alcoholic fermentation to refine wine style, particularly by enhancing red fruit aromas and reducing off-aromas in Shiraz. However, the limited impact on Cabernet Sauvignon underscores the importance of cultivar-specific approaches. By integrating chemical and sensory data, this study provides practical guidance for winemakers seeking to optimize fermentation practices and achieve desired wine profiles across diverse cultivars and vintages. AFRIKAANSE OPSOMMING: Hierdie studie het die impak van beheerde suurstofbyvoegings tydens alkoholiese fermentasie op die chemiese en sensoriese profiele van Shiraz-wyne oor twee oeste en Cabernet Sauvignon van een oes ondersoek. Suurstofbestuur tydens alkoholiese fermentasie speel 'n belangrike rol in die vorming van wynaroma, smaak en mondgevoel. Die navorsing het ten doel gehad om te ondersoek hoe beheerde suurstofblootstelling die wynkwaliteit kan verbeter deur die aroma te verbeter, "reduktiewe" ongewensde geure te verminder, en risiko's soos die vorming van "geoksideerde" ongewensde aromas te beperk. Lae en hoë suurstofbyvoegings is tydens alkoholiese fermentasie toegepas, gevolg deur gedetailleerde chemiese en sensoriese ontledings. Fenoliese analise het konsekwente afnames in MCP-tannienkonsentrasies onder hoë suurstofbehandelings in Shiraz-wyne gewys oor beide oeste, terwyl Cabernet Sauvignon-wyne minimale tannienveranderinge vertoon het, wat die kultivar- spesifieke oksidatiewe reaksies weerspieël. HPLC-analise het 'n stabiele gemiddelde graad van polimerisasie (mDP) en gemiddelde molêre massa getoon, wat daarop dui dat suurstof hoofsaaklik die tannien-subeenheidsamestelling eerder as die polimergrootte verander het. Sensoriese evaluering het afnames in reduktiewe ongewensde aromas en verbeterde rooi vrugte- eienskappe in Shiraz-wyne wat aan suurstof blootgestel is tydens alkoholiese fermentasie getoon, met geen beduidende veranderinge in mondgevoel nie. Aan die ander kant het Cabernet Sauvignon minimale sensoriese verskille getoon, wat die behoefte aan kultivar-spesifieke suurstofstrategieë beklemtoon. Hoofkomponent-analise (PCA) het verder die verband tussen sensoriese eienskappe en suurstofbehandelings verduidelik. Interessant genoeg is daar geen opspoorbare oksidatiewe aroma-eienskappe waargeneem nie, selfs onder hoë suurstofbyvoegings, wat moeilik in praktyk in die wynmaakproses bereikbaar is. Dit is ondersteun deur stabiele asetaldehiedvlakke, wat aandui dat suurstofblootstelling tydens alkoholiese fermentasie nie oksidasieprosesse opwek wat sterk genoeg is om tipiese "oksidatiewe" ongewensde aromas te produseer nie. Hierdie bevindings demonstreer die potensiaal van beheerde suurstofblootstelling tydens alkoholiese fermentasie om die wynstyl te verfyn, veral deur die rooi-vrug aromas te verbeter en ongewensde geure in Shiraz te verminder. Die beperkte impak op Cabernet Sauvignon beklemtoon egter die belangrikheid van kultivar-spesifieke benaderings. Deur chemiese en sensoriese data te integreer, bied hierdie studie praktiese leiding vir wynmakers wat poog om fermentasiepraktyke te optimaliseer en gewenste wynprofiele oor verskeie kultivars en oeste te bereik. Masters 2025-06-09T09:24:21Z 2025-06-09T09:24:21Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132461 en Stellenbosch University viii, 143 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Wine and wine making -- Chemistry Fermented beverages Shiraz (Wine) -- Composition Wine -- Flavor and odor Cabernet (Wine) -- Composition Oxygen Red wines -- Oxidation UCTD Roodt, Xander Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine |
| title | Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine |
| title_full | Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine |
| title_fullStr | Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine |
| title_full_unstemmed | Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine |
| title_short | Oxygen additions during alcoholic fermentation: effects on chemical and sensory composition of red wine |
| title_sort | oxygen additions during alcoholic fermentation effects on chemical and sensory composition of red wine |
| topic | Wine and wine making -- Chemistry Fermented beverages Shiraz (Wine) -- Composition Wine -- Flavor and odor Cabernet (Wine) -- Composition Oxygen Red wines -- Oxidation UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132461 |
| work_keys_str_mv | AT roodtxander oxygenadditionsduringalcoholicfermentationeffectsonchemicalandsensorycompositionofredwine |