118 research outputs found
Preliminary characterisation of mannoproteins from different wine yeast strains and impact on wine properties
No full textMannoproteins (MPs) are released from the yeast cell wall during alcoholic fermentation and aging on the lees, and influence aspects of wine quality such as haze formation and colour stability. Yet, as this is a slow process with microbiological and sensory risks, the exogenous addition of extracted MPs poses an efficient alternative. While Saccharomyces cerevisiae has long been studied as a prominent source for MPs extraction, their structure and composition greatly differ between yeast species. This may influence their behaviour in the wine matrix and subsequent impact on wine properties. However, although wine yeast species other than S. cerevisiae possibly present an untapped source of MPs, they are still ill-characterised in terms of chemical composition and influence on wine.
This study aimed to characterise the composition of MPs extracted from different wine yeast strains, and to investigate the impact of their addition on wine properties of organoleptic significance. MPs extracted and purified from four strains belonging to four different species (Saccharomyces cerevisiae, Saccharomyces boulardii, Metschnikowia fructicola and Torulaspora delbrueckii) were subjected to HR-SEC and GC-MS analyses to determine polysaccharide size distribution and monosaccharide composition, respectively. After addition of these MPs to Cabernet Sauvignon and Chardonnay wines, samples taken over the course of 6 months were analysed for protein stability, colour stability, browning potential and astringency.
HR-SEC analyses of the MPs revealed differences in size distribution patterns between species both in terms of the maximum and the medium molecular weight observed. MPs impact on the four different wine parameters tested were dependent on several factors, including time since MPs addition, and the yeast strain of origin. For example, whereas the addition of MPs from S. cerevisiae and S. boulardii showed increased white wine protein stability after 3 months, M. fructicola and T. delbrueckii did not.
The results obtained in this study form an important step towards further characterisation of mannoproteins derived from non-Saccharomyces yeast species. While the variable impact of MPs from different species on wine properties is an important aspect to consider in winemaking applications, further information regarding the influence of variations in MPs structure and composition could be used to better understand this effect
Optimised Extraction and Preliminary Characterisation of Mannoproteins from Non-Saccharomyces Wine Yeasts
No full textThe exogenous application of yeast-derived mannoproteins presents many opportunities for the improvement of wine technological and oenological properties. Their isolation from the cell wall of Saccharomycescerevisiae has been well studied. However, investigations into the efficiency of extraction methods from non-Saccharomyces yeasts are necessary to explore the heterogeneity in structure and composition that varies between yeast species, which may influence wine properties such as clarity and mouthfeel. In this study, nine yeast strains were screened for cell wall mannoprotein content using fluorescence microscopy techniques. Four species were subsequently exposed to a combination of mechanical and enzymatic extraction methods to optimize mannoprotein yield. Yeast cells subjected to 4 min of ultrasound treatment applied at 80% of the maximum possible amplitude with a 50% duty cycle, followed by an enzymatic treatment of 4000 U lyticase per g dry cells weight, showed the highest mannoprotein-rich yield from all species. Furthermore, preliminary evaluation of the obtained extracts revealed differences in carbohydrate/protein ratios between species and with increased enzyme incubation time. The results obtained in this study form an important step towards further characterization of extraction treatment impact and yeast species effect on the isolated mannoproteins, and their subsequent influence on wine properties
A novel approach for the valorization of wine lees as a source of compounds able to modify wine properties
No full textMannoproteins extracts from wine lees: characterisation and impact on wine properties
No full textThis study aims at exploiting an undervalued winemaking by-product, wine yeast lees, by developing efficient and food-grade methods for the extraction of yeast glycoproteins. These extracts were then supplemented to wine and their impact on wine properties assessed. White wine lees were produced by fermenting Sauvignon blanc grape juice with S. cerevisiae Uvaferm HPS strain. Three extraction methods were applied on lees using physical (autoclave and sonication) or enzymatic (Glucanex®, an industrial β-glucanases) approaches. Glycoproteins extracts were characterized by SEC-HPLC and SDS-PAGE. After their addition to wine (0.5 g/L), no alteration of wine clarity was detected. The ultrasonication and enzymatic extracts, containing a relatively low amount of glycoproteins, led to a significant decrease in wine protein haze formation upon heat test (-7%). Conversely, the autoclave extract was the richest in glycoproteins and had a positive impact on wine foaming properties, inducing an increase in foam’s maximum height and stability which were 2.6 and 3.6 times higher compared to a model wine. The autoclave extract improved tartrate stability as shown by a decrease in wine conductance (-11%) compared to the untreated wine. Results suggest that white wine lees could be considered a valuable source of glycosylated proteins with potential applications in winemaking. In this context, the autoclave appears as the more promising method in terms of both efficiency and extract’s effectiveness. The proposed food-grade exploitation approach could represent an important tool to improve the environmental and economical sustainability of the wine supply chain
Characterization of Mannoprotein Structural Diversity in Wine Yeast Species
No full textThe structure of yeast cell wall (CW) mannoproteins (MPs) influences their impact on wine properties. Yeast species produce a diverse range of MPs, but the link between properties and specific structural features has been ill-characterized. This study compared the protein and polysaccharide moieties of MP-rich preparations from four strains of four different enologically relevant yeast species, named Saccharomyces boulardii (SB62), Saccharomyces cerevisiae (SC01), Metschnikowia fructicola (MF77), and Torulaspora delbrueckii (TD70), and a commercial MP preparation. Monosaccharide determination revealed that SB62 MPs contained the highest mannose/glucose ratio followed by SC01, while polysaccharide size distribution analyses showed maximum molecular weights ranging from 1349 kDa for MF77 to 483 kDa for TD70. Protein identification analysis led to the identification of unique CW proteins in SB62, SC01, and TD70, as well as some proteins shared between different strains. This study reveals MP composition diversity within wine yeasts and paves the way toward their industrial exploitation
Impact of mannoproteins from different yeast species on wine properties
No full textThe extent to which the addition of extracted mannoproteins (MPs) improve wine properties
such as mouthfeel, clarity and colour stability is a controversial topic, and conflicting results
have been reported. One possible explanation for this is the diversity that exists between
MPs, a prevalent cause for which is their yeast strain of origin. However, although wine yeast
species other than Saccharomyces cerevisiae possibly present an untapped source of MPs, their
influence on wine as extracted additives is still ill-characterised. This study sought to compare
the impact of MPs extracted and purified from different yeast species, named Saccharomyces
boulardii, Saccharomyces cerevisiae, Metschnikowia fructicola and Torulaspora delbrueckii,
as well as a commercial control, on wine. MPs were applied to a red and a white wine at three
different concentrations, and BSA-reactive tannins, polymeric pigments, colour characteristics,
browning potential and protein haze-forming potential were measured over the course of six
months. The most notable differences were observed for the commercial MP, which achieved
lower BSA-reactive tannins, increased polymeric pigments and a greater reduction of browning
potential. This could be due to the difference in preparation procedures compared to the MPs
extracted and purified for this study, possibly leading to variations in the commercial MPs’
structure and composition. However, some differences were also evident between species, with
M. fructicola treatments achieving a 20 % reduction in browning compared to ~10 % for the
other purified MPs and significantly increased colour intensity of red wine treated with low
concentrations of T. delbrueckii. This study highlights alternative yeast species as a potential
source of MPs with diverse benefits to wine and the need for further investigation into their
diversity and properties to promote their eventual exploitation
Non-saccharomyces killer toxins : possible biocontrol agents against brettanomyces in wine?
No full textCITATION: Mehlomakulu, N. N., Setati, M. E. & Divol, B. 2015. Non-saccharomyces killer toxins : possible biocontrol agents against brettanomyces in wine?. South African Journal for Enology and Viticulture, 36(1):94-104, doi:10.21548/36-1-939.The original publication is available at http://www.journals.ac.za/index.php/sajevRed wine spoiled by the yeast Brettanomyces bruxellensis is characterised by off-odours commonly
described as horse sweat, phenolic, varnish and band-aid. The growth of this yeast in wine is traditionally
controlled by the use of sulphur dioxide (SO2). However, the concentration of SO2, the pH of the wine,
the presence of SO2-binding chemical compounds in the wine, as well as the strain of B. bruxellensis,
determine the effectiveness of SO2. Other chemical preservatives have been tested, but are not much more
efficient than SO2, and methods used to clean barrels are only partially effective. Filtration of wine and
the use of electric currents/fields are also reported to alter the physical and sensory properties of wine. In
this context, alternative methods are currently sought to achieve full control of this yeast in wine. Killer
toxins have recently been proposed to fulfil this purpose. They are antimicrobial compounds secreted
by Saccharomyces and non-Saccharomyces yeasts, displaying killer activity against other yeasts and
filamentous fungi. They are believed to play a role in yeast population dynamics, and this killer phenotype
potentially could be exploited to inhibit the growth of undesired microorganisms within a microbial
ecosystem such as that occurring in wine. In this review, non-Saccharomyces killer toxins are described
and their potential application in inhibiting B. bruxellensis in wine is discussed in comparison to other
tried methods and techniques.http://www.journals.ac.za/index.php/sajev/article/view/939Publisher's versio
La microbiologie des vins issus des raisins botrytisés au cours de l'élevage: Caractérisation des souches de "Saccharomyces cerevisiae" responsables de refermentations
No full textThe alcoholic fermentation of Botrytis-affected wines is stopped by addition of sulphur dioxide. Some fermenting yeast species can survive during maturation and grow in spite of high ethanol, sugars and sulphur dioxide concentrations. An undesirable new fermentation, named "refermentation", can sometimes occur. In this study, it was proved that some yeast species were able to survive in a viable but non-culturable-like state. This state explains the apparent sterility of wines during maturation. Within Saccharomyces cerevisiae species, an intraspecific selection was spontaneously operated. After some weeks, only one strain could often survive. An ecological study was realized. Some highly fermentative and oxidative species could survive. In spite of slower metabolism, they synthesized acetaldehyde during maturation. The exit from the VBNC state and the high sulphur dioxide binding power were the keys of refermentations. The use of dimethyldicarbonate to stop alcoholic fermentation was studied. The most efficient action was observed for the mixed sulphur dioxide and DMDC addition. Some Saccharomyces cerevisiae strains responsible for refermentations were isolated. These strains exhibited rDNA sequence singularities, showing that they were close to flor strains, responsible for velum formation in some special wines. Moreover, those strains constitutively over-expressed SSU1 gene and could rapidly synthesize high concentrations of acetaldehyde in response to sulphur dioxide addition. High sulphur dioxide concentrations had probably selected the most resistant strains. Refermentation is the result of genetic adaptation and selection, under the influence of microbiological, physical, chemical and human parameters.La fermentation alcoolique des vins liquoreux français issus de raisin botrytisés est arrêtée brutalement par ajout massif de dioxyde de soufre après qu'un certain équilibre est atteint entre la teneur en alcool formé et la concentration en sucres résiduels. Certaines souches de levures fermentaires survivent et parfois se multiplient provoquant une nouvelle fermentation alcoolique indésirable ; c'est la refermentation. Le suivi microbiologique de nombreux lots de vin a permis de montrer que des levures sont dans un état physiologique similaire à celui décrit chez les bactéries sous l'appellation de viable non cultivable. Cet état explique l'apparente stérilité du vin après le mutage. Au sein de l'espèce Saccharomyces cerevisiae, une sélection naturelle se produit, ne laissant souvent la place qu'à une seule souche de refermentation, tolérante au dioxyde de soufre. Une étude écologique a montré que seules certaines espèces fermentaires et oxydatives survivent. Les plus tolérantes au dioxyde de soufre forment de l'éthanal au cours de l'élevage, malgré un métabolisme ralenti, et augmente la combinaison du dioxyde de soufre libre. Cet éthanal vient progressivement combiner le dioxyde de soufre libre. La sortie de l'état viable non cultivable est probablement la clef des mécanismes engendrant les refermentations. L'utilisation du diméthyldicarbonate au moment du mutage a été étudiée en couplage avec le dioxyde de soufre. Des souches de Saccharomyces cerevisiae de refermentation ont été isolées. Elles exhibent des singularités de séquence de leur ADNr, les apparentant aux souches de voile de certains vins spéciaux. Ces souches surexpriment constitutivement le gène SSU1 et synthétisent rapidement une forte concentration d'éthanal en réponse à la présence de dioxyde de soufre. La présence de fortes concentrations de dioxyde de soufre sélectionne les souches les plus résistantes. La refermentation est donc le résultat d'une adaptation génétique et d'une sélection, fruit d'une multitude de paramètres microbiologiques, physico-chimiques et humains
La microbiologie des vins issus des raisins botrytisés au cours de l'élevage. Caractérisation des souches de "Saccharomyces cerevisiae" responsables de refermentations.
No full textLa fermentation alcoolique des vins liquoreux français issus de raisin botrytisés est arrêtée brutalement par ajout massif de dioxyde de soufre après qu'un certain équilibre est atteint entre la teneur en alcool formé et la concentration en sucres résiduels. Certaines souches de levures fermentaires survivent et parfois se multiplient provoquant une nouvelle fermentation alcoolique indésirable ; c'est la refermentation. Le suivi microbiologique de nombreux lots de vin a permis de montrer que des levures sont dans un état physiologique similaire à celui décrit chez les bactéries sous l'appellation de viable non cultivable. Cet état explique l'apparente stérilité du vin après le mutage. Au sein de l'espèce Saccharomyces cerevisiae, une sélection naturelle se produit, ne laissant souvent la place qu'à une seule souche de refermentation, tolérante au dioxyde de soufre. Une étude écologique a montré que seules certaines espèces fermentaires et oxydatives survivent. Les plus tolérantes au dioxyde de soufre forment de l'éthanal au cours de l'élevage, malgré un métabolisme ralenti, et augmente la combinaison du dioxyde de soufre libre. Cet éthanal vient progressivement combiner le dioxyde de soufre libre. La sortie de l'état viable non cultivable est probablement la clef des mécanismes engendrant les refermentations. L'utilisation du diméthyldicarbonate au moment du mutage a été étudiée en couplage avec le dioxyde de soufre. Des souches de Saccharomyces cerevisiae de refermentation ont été isolées. Elles exhibent des singularités de séquence de leur ADNr, les apparentant aux souches de voile de certains vins spéciaux. Ces souches surexpriment constitutivement le gène SSU1 et synthétisent rapidement une forte concentration d'éthanal en réponse à la présence de dioxyde de soufre. La présence de fortes concentrations de dioxyde de soufre sélectionne les souches les plus résistantes. La refermentation est donc le résultat d'une adaptation génétique et d'une sélection, fruit d'une multitude de paramètres microbiologiques, physico-chimiques et humains. Botrytis-affected wines microbiology during maturation. Characterization of Saccharomyces cerevisiae strains responsible for refermentation. ABSTRACT : The alcoholic fermentation of Botrytis-affected wines is stopped by addition of sulphur dioxide. Some fermenting yeast species can survive during maturation and grow in spite of high ethanol, sugars and sulphur dioxide concentrations. An undesirable new fermentation, named "refermentation", can sometimes occur. In this study, it was proved that some yeast species were able to survive in a viable but non-culturable-like state. This state explains the apparent sterility of wines during maturation. Within Saccharomyces cerevisiae species, an intraspecific selection was spontaneously operated. After some weeks, only one strain could often survive. An ecological study was realized. Some highly fermentative and oxidative species could survive. In spite of slower metabolism, they synthesized acetaldehyde during maturation. The exit from the VBNC state and the high sulphur dioxide binding power were the keys of refermentations. The use of dimethyldicarbonate to stop alcoholic fermentation was studied. The most efficient action was observed for the mixed sulphur dioxide and DMDC addition. Some Saccharomyces cerevisiae strains responsible for refermentations were isolated. These strains exhibited rDNA sequence singularities, showing that they were close to flor strains, responsible for velum formation in some special wines. Moreover, those strains constitutively over-expressed SSU1 gene and could rapidly synthesize high concentrations of acetaldehyde in response to sulphur dioxide addition. High sulphur dioxide concentrations had probably selected the most resistant strains. Refermentation is the result of genetic adaptation and selection, under the influence of microbiological, physical, chemical and human parameters
Tracking the careers of grape and wine polymers using biotechnology and systems biology.
No full textPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected] Vir Wynbiotegnologi
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