377 research outputs found
Hydrogen sulfide and its roles in Saccharomyces cerevisiae in a winemaking context
No full textThe rotten-egg odour of hydrogen sulfide (H₂S) produced by the yeast Saccharomyces cerevisiae has attracted considerable research interest due to its huge impact on the sensory quality of fermented foods and beverages. To date, the yeast genetic mechanisms of H₂S liberation during wine fermentation are well understood and yeast strains producing low levels of H₂S have been developed. Studies have also revealed that H₂S is not just a by-product in the biosynthesis of the sulfur-containing amino acids, but indeed a vital molecule involved in detoxification, population signalling and extending cellular life span. Moreover, polysulfides have recently emerged as key players in signalling and the sensory quality of wine because their degradation leads to the release of H₂S. This review will focus on the recent findings on the production of H₂S and polysulfides in S. cerevisiae and summarise their potential roles in yeast survival and winemaking. Recent advances in techniques for the detection of H₂S and polysulfides offer an exciting opportunity to uncover the novel genes and pathways involved in their formation from different sulfur sources. This knowledge will not only provide further insights into yeast sulfur metabolism, but could potentially improve the sensory quality of wine.Chien-Wei Huang, Michelle E. Walker, Bruno Fedrizzi, Richard C. Gardner and Vladimir Jirane
First evidence of the presence of S-cysteinylated and S-glutathionylated precursors in tannins
No full textTannins are widely used in winemaking and food and beverage preparation for the many different contributions they can give to the overall characteristics of the product (e.g., colour stability, mouthfeel and aromatic composition). Varietal thiols and their precursors are one of the most interesting research areas in food science and a lot of effort has been put to further the current understanding on their formation and on the impact of different production strategies on their concentration in the final product.
This paper reports the identification of two important thiol precursors (Cys-3MH and GSH-3MH) in commercial grape oenological tannins and, to the best of our knowledge, this information is reported here for the first time. This finding allows potential new perspectives in the winemaking and the food industry, offering the possibility of controlled additions of thiol precursors in pre-fermentative stages in order to tune the aroma profile of fermented product
Effects of noble rot on must composition and aroma profile of Amarone wine produced by the traditional grape withering protocol
No full textThe effects of noble rot on the overall quality of Amarone wine, a “Passito” dry red wine, produced with traditional withering grape process is still poorly investigated. Wines obtained from healthy and selected grapes infected by noble-rot were compared. Validation of the experimental plan was carried out by determining glycerol and gluconic acid content, laccase activity and microbial analysis of the musts. The B. cinerea infection produced significant variation on esterase and β-glucosidase activity of grape must. Aroma analysis in healthy and botrytized wines, was carried out by SPE extraction followed by GC–MS quantification. A decrease of several fermentative esters was observed in botrytized wine, while the one produced from healthy grapes showed a higher fatty acid content. Molecules as 1-octen-3-ol, phenylacetaldehyde and furaneol were correlated positively to the noble-rotten grapes. Interestingly, γ-nonalactone and 4-carbethoxy-γ-butyrolactone increased, while Sherry lactones decreased in botrytized wine. The strong increase of N-(3-methylbutyl)-acetamide was related to B. cinerea grape infection
Aging Effects and Grape Variety Dependence on the Content of Sulfur Volatiles in Wine
No full textThirteen sulfur compounds (boiling points from 35 to 231 °C), usually considered as possible offflavoring
volatiles, were quantified by a concurrent headspace-solid phase microextraction method
coupled with gas chromatography–mass spectrometry (HS-SPME/GC-MS) on 80 not off-flavoring
wines of four varieties (Merlot, Marzemino, and Teroldego as red wines and Chardonnay as a white
one) and of five vintages produced in the North Italian Trentino region. The results of the research,
the first Italian data-bank per variety on such volatiles, allow us to make a comparison with the data
of other winegrowing areas, to investigate the aging effect on the considered volatiles, and, finally,
to try a variety discrimination using statistical procedures. Dimethyl sulfide, 3-(methylthio)-1-propanol,
diethyl sulfide, and diethyl disulfide were found to increase with time whereas 2-mercaptoethanol
and ethylmercaptan showed a decreasing trend. Furthermore, the concentration of several compounds
was found to be dependent on the variety. For instance, sulfide, disulfides, benzothiazole, and
thioalcohols are at higher levels in Merlot wines, whereas thiols and thioacetates are more abundant
in Marzemino and Teroldego wines. Chardonnay products, well apart from the other wines, are the
poorest in 3-(methylthio)-1-propanol and rather rich in dimethyl disulfide and in diethyl disulfide, mostly
in the aged wines. Applying the principal component analysis to the data, it was possible to
demonstrate that Chardonnay and Merlot wines are well-discriminated from the Italian native varietal
wines, which on their turn are only partially distinguishable among them. A contribution of these
compounds to the variety characteristics of wine is reasonable
COMPOSITION, MICROSTRUCTURE AND MECHANICAL PROPERTY RELATIONS IN SINTERED STAINLESS-STEEL
No full textConvenient synthesis of deuterium labelled sesquiterpenes
No full textSesquiterpenes are an important class of molecules, with roles ranging from pollination and signalling to defense mechanisms. Despite their apparent importance, the limited number of commercial standards has hindered their study and precise quantification. Herein, we report the syntheses of fourteen labelled sesquiterpenes with a high level of deuterium incorporation (>95%) for applications in MS-based studies
Oenological tannins as a source of thiol precursors
No full textOenological tannins are a widely used adjuvant in winemaking. They can help stabilising colour, stringency and
flavour. European regulation currently allows tannins produced form vegetable origins in winemaking.
Previous researches have already highlighted the contribution that tannins can give to flavour [1] and aroma [2]
of wine.
Among the aroma classes identified and investigated in wine, varietal thiols (i.e. 3-mercaptohexan-1-ol, 3-
mercaptohexyl acetate and 4-mercapto-4-methylpentan-2-one) are particularly important for their extremely low
sensory threshold and highly appreciated aroma descriptors [3].
In this communication we are presenting the first identification of two known thiol precursors (S-3-
glutathionylhexan-1-ol and S-3-cysteinylhexan-1-ol) in oenological tannins [4] and the impact of controlled
addition of this adjuvant on free thiols in the final wines [5].
This evidence opens several avenues for an additional application of oenological tannins in the wine industry
and shed new light on the impact that oenological tannins might have on final aroma profil
Caratteristiche sensoriali ed aromatiche di vini elaborati tramite macerazioni lunghe.
No full textCaratteristiche sensoriali ed aromatiche di vini elaborati tramite macerazioni lunghe
Monitoring accumulation and degradation of polysulfides with the consequently hydrogen sulfide formation using ion chromatography and ultra highpressure liquid chromatography combined with fraction collection and high-resolution mass spectrometry
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