Institute for Wine Biotechnology
Permanent URI for this community
Browse
Browsing Institute for Wine Biotechnology by Author "Buica, A. S."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- ItemDetermining the impact of industrial wine yeast strains on organic acid production under white and red wine-like fermentation conditions(South African Society for Enology and Viticulture, 2015) Chidi, B. S.; Rossouw, D.; Buica, A. S.; Bauer, FlorianOrganic acids are a major contributor to wine flavour and aroma. In the past, the scientific focus has mostly been on organic acids derived from grapes or on the transformation of malic acid to lactic acid by lactic acid bacteria, since these acids contribute significantly to the final total acidity of wine. However, the organic acid concentration and composition also change significantly during alcoholic fermentation, yet only limited information regarding the impact of different yeast strains on these changes has been published. Here we report on changes in organic acid (malic, tartaric, citric, succinic, acetic and pyruvic) composition during fermentation by five widely used industrial wine yeast strains in a synthetic grape must (MS300) reflecting two very different, but both wine-like, fermentation conditions. Samples were obtained from three physiological stages during fermentation, namely the exponential growth phase (day 2), early stationary phase (day 5) and late stationary phase (day 14). These different stages were selected to provide more information on acid evolution throughout fermentation, as well as on the impact of nutritional and environmental conditions during aerobic and anaerobic fermentation. Among other observations, some strains (such as VIN13 and 285) were shown to be generally higher producers of most acids in white and/ or red wine fermentation settings, while other strains (such as DV10) were generally lower acid producers. The data clearly demonstrate that different strains have different acid consumption and production patterns, and this presents a first step towards enabling winemakers to appropriately select strains for acid management during fermentation.
- ItemInvestigating the concept of South African old vine Chenin blanc(South African Society for Enology and Viticulture, 2020) Mafata, M.; Brand, J.; Panzeri, V.; Buica, A. S.Although South African vineyards are still young by European standards, there is a belief in the industry that vines aged 35 or more years produce grapes and wines with specific characteristics (“old vine wines”). The aim of this study was to investigate the existence of the concept of old vine Chenin blanc wines using a typicality rating and sorting tasks. Chenin blanc wines were made from grapes harvested from vines aged five to 45 years old. Winemaking was standardised, with no wood contact. Typicality rating and sorting tasks were performed on young (first-stage) and two-year bottle-aged (second-stage) wines. Principal component analysis (PCA) on rating data demonstrated judge consensus, but no correlation was found between vine age and typicality rating. Sorting results were submitted to agglomerative hierarchical clustering (AHC) performed on the correspondence analysis (CA) and multidimensional scaling (MDS) results for grouping and attributes resulting from the sorting task. The clusters were different for the young wines and two-year bottle-aged wines. The verbal aspect of the sorting demonstrated the judges’ agreement on the concept of old vine Chenin blanc, shown by the annotation of the old vine group as ‘complex’, ‘balance’, ‘rich’ and ‘good mouthfeel’. However, because the judges did not sort the wines according to vine age, the perceptual aspect of the concept could not be confirmed, its features could not be tested further, and the sensory space could not be built.
- ItemIs there a link between coffee aroma and the level of furanmethanethiol (FMT) in pinotage wines(South African Society for Enology and Viticulture, 2020) Garrido-Banuelos, G.; Buica, A. S.Over the years, Pinotage has found its way into the South African and international market. Producers have used the flavour potential of this “original” South African grape to produce different wine styles, one of them being the so-called “coffee-style Pinotage”. The current study aims to explain the impact of furanmethanethiol (FMT) on the characteristic coffee aroma of these coffee-style wines. Chemical and sensory evaluation, as well as data mining of the technical information available, was performed. Not all wines marketed as “coffee Pinotage” showed a high “coffee” rating. However, the results showed a good correlation between the aroma perception and FMT concentrations (R2 = 0.81). However, RV coefficients were low when comparing the coffee rating with the information provided on both the front and the back label, which shows that, in some cases, the use of the “coffee Pinotage” term was rather part of the marketing strategy.
- ItemResearch note: the use of SO2 to bind acetaldehyde in wine : sensory implications(South African Society for Enology and Viticulture, 2018) Coetzee, C.; Buica, A. S.; Du Toit, W. J.It is thought that the formation of hydroxysulphonate when sulphur dioxide is added to wine containing free acetaldehyde negates the sensory impact of the latter compound, but little research has been done on this. Descriptive analyses were employed using a trained sensory panel to assess the sensory effect of sulphur dioxide and acetaldehyde as single compounds and in combination in model wine. The addition of acetaldehyde or sulphur dioxide as singular compounds led to large increase in especially the green apple or sulphur descriptors respectively. When these two compounds were added in equimolar concentrations, the green apple description decreased drastically; however, a prominent sulphur description was still noted. It thus seems that hydroxysulphonate also has a sulphur-like aroma. The hydroxysulphonate did not influence the perception of a prominent ester, isoamyl acetate, in model wine. A low pH influences the perception of sulphur when sulphur dioxide is present on its own, but this is not the case with hydroxysulphonate. The implications of these results for wine production are discussed further.