Browsing by Author "Chandra, Mahesh"
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- Effect of ethanol, sulfur dioxide and glucose on the growth of wine spoilage teasts using response surface methodologyPublication . Chandra, Mahesh; Oro, Inês; Ferreira-Dias, Suzana; Malfeito-Ferreira, ManuelResponse surface methodology (RSM) was used to study the effect of three factors, sulfur dioxide, ethanol and glucose, on the growth of wine spoilage yeast species, Zygosaccharomyces bailii, Schizosaccharomyces pombe, Saccharomycodes ludwigii and Saccharomyces cerevisiae. Seventeen central composite rotatable design (CCRD) trials were designed for each test yeast using realistic concentrations of the factors (variables) in premium red wine. Polynomial regression equations were fitted to experimental data points, and the growth inhibitory conditions of these three variables were determined. The overall results showed Sa. ludwigii as the most resistant species growing under high ethanol/free sulfur dioxide concentrations, i.e., 15% (v/v)/20 mg L-1, 14% (v/v)/32 mg L-1 and 12.5% (v/v)/40 mg L-1, whereas other yeasts did not survive under the same levels of ethanol/free sulfur dioxide concentrations. The inhibitory effect of ethanol was primarily observed during longer incubation periods, compared with sulfur dioxide, which showed an immediate effect. In some CCRD trials, Sa. ludwigii and S. cerevisiae showed growth recovery after a short death period under the exposure of 20–32 mg L-1 sulfur dioxide in the presence of 11% (v/v) or more ethanol. However, Sc. pombe and Z. bailii did not show such growth recovery under similar conditions. Up to 10 g L-1 of glucose did not prevent cell death under the sulfur dioxide or ethanol stress. This observation demonstrates that the sugar levels commonly used in wine to sweeten the mouthfeel do not increase wine susceptibility to spoilage yeasts, contrary to the anecdotal evidence
- Forest Oak Woodlands and Fruit Tree Soils Are Reservoirs of Wine-Related Yeast SpeciesPublication . Chandra, Mahesh; Mota, Mariana; Silva, Ana Carla; Malfeito-Ferreira, ManuelIn this study, a large-scale sampling plan was performed over a period of four years in three different vineyards to evaluate the occurrence of wine-related yeast species in the soils underneath vines and forest oak and fruit trees close to the vineyards. Ascomycetous fermentative yeasts were present in 27% of 320 soil samples throughout the sampling years with incidences that could not be related to sampling season. Highest percentages of occurrence were found in soils under fig (76%), apple (73%) and oak trees (41-55%). Soils were less contaminated under vines (6%), while these yeasts were not recovered from soil underneath chestnut trees. Other soils showed intermediate percentages of occurrence. A total of 139 fermentative ascomycetes were identified, revealing 25 species. A total of 96 isolates corresponded to different non-Saccharomyces species and 43 isolates to 4 Saccharomyces species. Soils underneath fruit trees shared 11 different species. The most common isolates belonged to Lachancea thermotolerans and Torulaspora delbrueckii, while Sacharomyces paradoxus predominated in the soil underneath oak trees. S. cerevisiae was found in low percentage (7% of total isolates) during all sampling years under fruit trees but was not recovered from vineyard or oak tree soils. The wine spoilage species Zygosaccharomyces bailii was recovered only in one sample of vineyard soil. Our work clearly demonstrated that, for a given soil system, the species recovered vary strongly over the years thus suggesting the existence of complex yeast communities. In particular, the soils in the vicinity of vineyards were found to be natural reservoirs of yeast species of oenological interest
- Forest Oak Woodlands and Fruit Tree Soils Are Reservoirs of Wine-Related Yeast SpeciesPublication . Chandra, Mahesh; Mota, Mariana; Silva, Ana Carla; Malfeito-Ferreira, ManuelA large-scale sampling plan was performed over four years in three different vineyards to evaluate the occurrence of wine-related yeast species in the soils underneath both vines and forest oak and fruit trees close to the vineyards. Ascomycetous fermentative yeasts were present in 27% of 320 soil samples throughout the sampling years, with incidences that could not be related to sampling season. The greatest percentages of occurrence were found in soils under fig (76%), apple (73%), and oak (41 to 55%) trees. Soils were less contaminated under vines (6%), while these yeasts were not recovered from soil underneath chestnut trees. Other soils showed intermediate percentages of occurrence. A total of 139 fermentative ascomycetes were identified from 25 species. Ninety-six isolates came from 21 different non-Saccharomyces species and 43 isolates from four Saccharomyces species. Soils underneath fruit trees had 11 different species. The most common isolates belonged to Lachancea thermotolerans and Torulaspora delbrueckii, while Sacharomyces paradoxus predominated in the soil underneath oak trees. Saccharomyces cerevisiae was found at low frequency (7% of total isolates) during all sampling years under fruit trees, but it was not recovered from vineyard or oak tree soils. The wine spoilage species Zygosaccharomyces bailii was recovered in only one sample of vineyard soil. For a given soil system, the species recovered varied strongly over the years, suggesting the existence of complex yeast communities. In particular, soils in the vicinity of vineyards were natural reservoirs for yeast species of enological interest
- Influence of Brettanomyces ethylphenols on red wine aroma evaluated by consumers in the United States and in PortugalPublication . Schumaker, Megan R.; Chandra, Mahesh; Malfeito-Ferreira, Manuel; Ross, Carolyn F.Brettanomyces may add complexity to wine at low concentrations but at high concentrations, can result in objectionable wines. The objective of this study was to determine the concentrations at which consumers from two different locations were able to detect Brettanomyces volatile compounds present in a red wine. A red wine blend, used in both countries, was spiked to create five treatments containing different concentrations of 4-ethylphenol (4-EP), 4-ethylguiacol (4-EG), and 4-ethylcatechol (4-EC) in a 5:1:1 ratio, respectively. These treatments were evaluated by consumers in the United States and Portugal (n = 121) using a difference from control test. Consumers were also classified as having low, medium, or high wine knowledge. Among the spiked samples, the greatest degree of difference was found between the second and third treatments, corresponding to reported detection and recognition threshold ranges of 4-EP and 4-EG. For some treatments, consumers from Portugal classified in the medium or high knowledge level reported significantly higher mean differences from the control than those in the low knowledge group (p < 0.05). Results demonstrated consumers' ability to detect differences in red wines due to Brettanomyces volatile compounds. Results provide useful context on how wine knowledge and cultural variants may affect the detection of Brettanomyces
- Investigating the Influence of Vessel Shape on Spontaneous Fermentation in WinemakingPublication . Malfeito-Ferreira, Manuel; Granja-Soares, Joana; Chandra, Mahesh; Asryan, Arman Asryan; Oliveira, Joana; Freitas, Victor; Loira, Iris; Morata, Antonio; Cunha, Jorge; Harutyunyan, MkrtichThe earliest archaeological evidence of wine came from ceramic vessels of the Tran- scaucasian ‘Shulaveri-Shomutepe’ or ‘Aratashen-Shulaveri-Shomutepe culture’ (SSC/AShSh: c. 6000–5200 BC). Western European ‘Bell Beaker culture’ (BB: c. 2500–2000 BC) is characterized by bell- shaped pottery vessels but has so far not been found with residues consistent with wine. Knowing that wild grapes populated both habitats, the absence of wine during the Bell Beaker period remains to be explained. The main goal of this work was to investigate whether the shape of the vessels could influence the performance of spontaneous fermentation, specifically regarding the production of volatile acidity. Crushed grapes or juices from various grape cultivars were fermented in two types of vessels: (i) borosilicate glass beakers (4–5 L) to imitate bell beakers and (ii) Erlenmeyer flasks (5 L) to imitate SSC/AShSh vessels. Fermentations occurred spontaneously, and the wines were analyzed for their conventional physical–chemical parameters (e.g., ethanol content, total acidity, volatile acidity, pH), chromatic characteristics (e.g., wine color intensity, wine hue), and volatile composition by gas-chromatography-flame ionization detection (GC-FID). At the end of fermentation, the yeast species were identified by molecular methods. In addition, wine yields and phenolic composition (e.g., total phenols, anthocyanins, total pigments) were determined for wild grapes in comparison with six red varieties Vitis vinifera L. subsp. sativa (Vinhão, Marufo, Branjo, Melhorio, Castelão and Tempranillo Tinto), chosen as a function of their genetic relatedness with the wild counterpart. Wines produced from V. sylvestris grapes showed higher total acidity and color intensity when compared to the cultivated varieties. Saccharomyces cerevisiae dominated at the end of all spontaneous fermen- tations in all types of vessels and conditions. Wines fermented in Erlenmeyers showed ethanol concentrations as high as 14.30% (v/v), while the highest ethanol level was 12.30% (v/v) in beakers. Volatile acidity increased to a maximum of 4.33 g/L (acetic acid) in Erlenmeyers and 8.89 g/L in beakers. Therefore, the shape of the vessels influenced the performance of fermentation, probably due to the different exposures to air, leading to vinegary ferments more frequently in open mouths than in conical-shaped flasks. These results provide a hypothesis based on fermentation performance for the absence of wine produced in the Iberian Peninsula until the arrival of Phoenician settlers.
- Off-flavours and unpleasantness are cues for the recognition and valorization of organic wines by experienced tastersPublication . Romano, Mylena; Chandra, Mahesh; Harutunyan, Mkrtich; Savian, Taciana; Villegas, Cristian; Minim, Valéria; Malfeito-Ferreira, ManuelThe drivers of consumer acceptance concerning organic wines are not well understood. In particular, among wine professionals, there are anecdotal evidences claiming that consumers accept off-flavours that would not be tolerated if the wines were conventionally produced. Therefore, the aim of this study was to shed further light on this issue by tasting blind wines of both types of production using a tasting panel comprised by experienced individuals of several nationalities. The tasted wines were both conventional and organic and were with and without off-flavours. The same wines were evaluated in three tasting sessions where the given information was: (1) all wines were conventional, (2) all wines were organic, and (3) tasters were asked to guess the mode of production. A group of untrained tasters also rated the same organic wines in an informed session. The results showed that wines were significantly better scored and were given a higher willingness to pay value in the “organic” session. In addition, the experienced tasting panel produced a list of the most frequent sensory descriptors. When tasters were asked to guess the mode of production, wines that were supposed to be organic received a higher citation of off-flavours, such as “oxidized”, “reductive”, and “animal/undergrowth”. Moreover, an overall emotional response of unpleasantness was associated with the recognition of organic wines in the “guess” session. Untrained tasters rated the same organic wines with lower liking scores and were willing to pay less. In conclusion, off-flavours and their unpleasantness worked as a cue to identify wines supposed to be organic by experienced tasters. Their corresponding higher valorization could be explained by the psychological halo effect induced by the organic label. Contrarily, consumers did not show this halo effect, depreciating wines with unpleasant flavours irrespective of their mode of production
- Role of p-Coumaric Acid and Micronutrients in Sulfur Dioxide Tolerance in Brettanomyces bruxellensisPublication . Chandra, Mahesh; Branco, Patricia; Prista, Catarina; Malfeito-Ferreira, ManuelSulfite is a common preservative in wine, but the spoilage yeast Brettanomyces bruxellensis can produce volatile phenols even with the recommended sulfite dose. The purpose of this study was to examine how wine components, p-coumaric acid (a precursor of volatile phenols), and micronutrients influence culturability, viability, and volatile phenols production by B. bruxellensis under sulfite stress. In red wine, a high sulfite dose (potassium metabisulfite, 100 mg L1) led to an immediate death phase followed by growth recovery after two weeks. However, 4-ethylphenol (4-EP) was continuously produced by dead or nonculturable cells. Nonetheless, an event of growth recovery could not be observed in the case of the model wine. However, when the model wine was supplemented with minerals and vitamins, both growth recovery and 4-EP production were noticed, suggesting that the minerals and vitamins played an important role in maintaining the viability of cells under the sulfite stress. The yeast could also utilize the p-coumaric acid (p-CA) as an energy source, showing a specific growth rate of 0.0142 h1 with 1 mM of p-CA in model wine. Furthermore, the sulfite-stressed cells exhibited ATP production by means of proton efflux while utilizing the p-CA. This work highlights the novel finding that the conversion of p-CA into 4-EP provides sufficient energy for the cell to remain metabolically active under the sulfite stress.
- Wine Microbial Consortium: Seasonal Sources and Vectors Linking Vineyard and Winery EnvironmentsPublication . Camilo, Sofia; Chandra, Mahesh; Branco, Patrícia; Malfeito-Ferreira, ManuelWinemaking involves a wide diversity of microorganisms with different roles in the process. The wine microbial consortium (WMC) includes yeasts, lactic acid bacteria and acetic acid bacteria with different implications regarding wine quality. Despite this technological importance, their origin, prevalence, and routes of dissemination from the environment into the winery have not yet been fully unraveled. Therefore, this study aimed to evaluate the WMC diversity and incidence associated with vineyard environments to understand how wine microorganisms overwinter and enter the winery during harvest. Soils, tree and vine barks, insects, vine leaves, grapes, grape musts, and winery equipment were sampled along four seasons. The isolation protocol included: (a) culture-dependent microbial recovery; (b) phenotypical screening to select fermenting yeasts, lactic acid, and acetic acid bacteria; and (c) molecular identification. The results showed that during all seasons, only 11.4% of the 1424 isolates presumably belonged to the WMC. The increase in WMC recovery along the year was mostly due to an increase in the number of sampled sources. Acetic acid bacteria (Acetobacter spp., Gluconobacter spp., Gluconoacetobacter spp.) were mostly recovered from soils during winter while spoilage lactic acid bacteria (Leuconostoc mesenteroides and Lactobacillus kunkeii) were only recovered from insects during véraison and harvest. The fermenting yeast Saccharomyces cerevisiae was only isolated from fermented juice and winery equipment. The spoilage yeast Zygosaccharomyces bailii was only recovered from fermented juice. The single species bridging both vineyard and winery environments was the yeast Hanseniaspora uvarum, isolated from insects, rot grapes and grape juice during harvest. Therefore, this species appears to be the best surrogate to study the dissemination of the WMC from vineyard into the winery. Moreover, the obtained results do not evidence the hypothesis of a perennial terroir-dependent WMC given the scarcity of their constituents in the vineyard environment along the year and the importance of insect dissemination