1,721,044 research outputs found
MONITORING OF GLUTATHIONE CONCENTRATION DURING THE WINEMAKING
No full textThe reduced glutathione can carry out several activities in must and wine, such as the antioxidant property. In this way, the formation of both browning and unpleasant flavours is slowed down. The glutathione level was monitored in several winemaking processes performed in industrial condition for the 2009 and 2010 vintages. The glutathione level is affected by the pressing, the copper concentration and the oxygen exposure of must. The yeast strain shows a weak influence on the glutathione amount if the readily assimilable nitrogen is adequate in must
Andamento della concentrazione di glutatione durante la vinificazione
No full textIl glutatione ridotto può svolgere in mosto e vino numerose attività tra le quali quella
antiossidante. In questo modo risultano sfavoriti l’imbrunimento e lo sviluppo di
difetti sensoriali. Il livello di glutatione è stato monitorato in numerose vinificazioni
su scala industriale nelle annate 2009 e 2010. La presenza di tale composto
risulta essere dipendente dalla pressatura, dal contenuto di rame e dall’esposizione
all’ossigeno del mosto. Il ceppo di lievito impiegato influenza debolmente la
concentrazione di glutatione se il quantitativo di azoto prontamente assimilabile
del mosto è adeguato.The reduced glutathione can carry out several activities in must and wine, such as the antioxidant property. In this way, the formulation of both browning and unpleasant flavours is slowed down. The glutathione level was monitored in several winemaking process performed in industrial condition for the 2009 and 2010 vintages. The glutathione level is affected by the pressing, the copper concentration and the oxygen exposure of must. The yeast strains shows a weak influence on the glutathione amount is the readily assimilable nitrogen is adequate in must
Monitoring of glutathione concentration during winemaking by a reliable high-performance liquid chromatography analytical method
No full textBackground and Aims: Glutathione (GSH) is valued in winemaking as an effective antioxidant in must and white wine if its concentration exceeds a few milligrams per litre. We report the further improvement of a previous analytical method for GSH quantification and its application to the analysis of grapes and wines. Methods and Results: Glutathione was derivatised with p-benzoquinone and detected by HPLC/UV. The analytical method was sensitive (limit of quantification, 0.43mg/L), linear (R2>0.997), accurate (recovery, 101% in grape juice and white wine) and repeatable (relative standard deviation, 3.1). The monitoring of vinifications at commercial wineries showed that Saccharomyces cerevisiae was a main source of GSH in wine, since the GSH of the grape was poorly preserved following juice preparation. Glutathione concentration decreased during wine aging on yeast lees. Conclusion: Glutathione concentration varied considerably during winemaking, and thus monitoring is essential for improving wine flavour and preventing oxidation. This method is suitable for this purpose. Significance of the Study: The analytical method proposed is reliable, fast and easy-to-apply and allows the assessment of the GSH in grape, must and wine. The strong role of the yeast on the GSH concentration in wine is reported
Caratterizzazione di frazioni parietali di lievito sulla base delle forme cisteiniche ridotte
No full textLa presenza di forme tioliche cisteiniche ridotte (FTCR) nei preparati enologici da parete cellulare di lievito potrebbe contribuire a prevenire lo sviluppo di fenomeni ossidativi nel vino tramite la riduzione delle forme chinoniche derivate dall’ossidazione fenolica. Un approccio analitico innovativo basato sulla reattività dei guppi tiolici verso il p-benzochinone, è stato utilizzato per caratterizzare mannoproteine, scorze, lisati, estratti e fecce di lievito di origine commerciale. Molti di tali additivi enologici hanno mostrato una spiccata attività legante verso le molecole tioliche libere ed una generale povertà in FTCR sia libere che proteiche. Questi prodotti potrebbero impoverire il patrimonio aromatico del vino e favorire lo sviluppo di fenomeni ossidativi, ma possono anche promuovere la rimozione di precoci difetti di ridotto. Alcuni campioni di scorza o lisati cellulari sono risultati contenere oltre 4 mmol/100 g di Cys e GSH liberi ridotti oltre che quantità solo poco inferiori di tioli di diversa origine la cui ascrivibilità a forme di Cys proteica ridotta da lievito richiederebbe opportuna conferma. I preparati mannoproteici sono risultati ampiamente danneggiati da un’intensa reazione di Maillard, misurata come indice di furosina, e particolarmente poveri in FTCR. La metodica proposta potrebbe aiutare a isolare frazioni di parete, e soprattutto mannoproteine, con migliori proprietà antiossidanti, nonché a valutare ulteriori aspetti dell’attività enologica delle FTCR
Determination of Reduced Cysteine in Oenological Cell Wall Fractions of Saccharomyces cerevisiae
No full textCompounds containing cysteine residues, such as glutathione, can affect the redox potential of must and wine by reduction of o-quinones and hydrogen peroxide. The oenological yeast cell wall fractions contain cysteine residues in their protein structure, and they could affect both oxidative and odor properties of wine. An analytical approach based on the derivatization of cysteinyl residues with p-benzoquinone followed by reversed-phase high-performance liquid chromatography separation was developed to quantify glutathione and free and protein cysteine in 16 Saccharomyces cerevisiae strains and 12 commercial samples of yeast mannoproteins, hulls, and lysates. The chemical modifications induced by the Mail lard reaction following the industrial preparation of such fractions were evaluated as well. Lysates showed the highest protein cysteine content and high contents of glutathione and free cysteine. Mannoproteins showed an intense Mail lard reaction (furosine >60 mg/100 g protein), and most of the samples were able to bind thiol compounds with a potentially detrimental effect toward the thiol-related odors in wine
INVESTIGATION ON CYSTEINYL THIOL COMPOUNDS FROM YEAST AFFECTING WINE PROPERTIES
Full text linkThiol compounds carry out several activities in must and wine. Among them, our attention was focused on the cysteinyl thiols (glutathione and free and protein bound cysteine).
The glutathione (GSH) properties in oenological matrices are well known: it reduces the o-quinones arising from the hydroxycinnamic acids esters, limiting the formation of brown polymers. GSH can decrease the loss of thiol-related aromas and it prevents the sotolon (3-hydroxy-4,5-dimethyl-2(5H)furanone) formation, the main responsible of the atypical white wine ageing. The GSH constitutes the main thiol compound on grape, in must and wine and its content is affected by the winemaking practices.
The cysteinyl residues on the yeast cell wall can limit the reduced/oxidized defects in wine ageing as they occur when the ageing sur lies or the addition of commercial yeast cell-wall fractions (YCWF) are carried out. The addition of such adjuvants is allowed by the European law (EU Regulation 2165/2005) and they exert several activities improving the sensorial properties of wine. The evaluation of their cysteinyl thiols level was the object of this research. The analytical approaches proposed in the literature are hard-to-apply for the routine analysis since the thiols quantification of YCWF was not reliable applying the methods described for the biological system proteins.
The aims of this research were to set up and validate a sensitive and reliable analytical method for the thiols content determination in the YCWF. The cysteinyl thiols content of some commercial preparations and active dry yeast was assessed and it was correlated to the heat damage occurring during the industrial preparation. The same analytical approach was applied and validated to the quantification of GSH in grape juice, must and wine. The winemaking practices affecting the GSH level were evaluated in real processes both in vintage 2009 (8) and vintage 2010 (10). Finally, also the oxidation rate in white wine was estimated through the evaluation of the interactions between GSH, sulfur dioxide and phenols.
The analytical approach proposed was based on the reaction between the thiol and p-benzoquinone (pBQ); the thio-substituted hydroquinones were separated by liquid chromatography and detected by spectrophotometry. The pBQ was added in excess and the unreacted amount was bound to an excess of 3-mercaptopropanoic acid. The derivatization was fast, accurate and stoichiometric at room temperature.
The YCWF showed an heterogeneous thiols content; the lysate samples had the highest thiols concentration, as well as the GSH which could have been added by the producer to increase the antioxidant properties. The lowest amount of cysteinyl thiols was detected in the mannoprotein samples which were also able to deplete the free cysteine and GSH. Such a behavior can decrease the content of the low molecular weight thiols (e.g. flavour related thiols) naturally occurring in wine. Moreover, the heat damage was higher in the mannoprotein samples and it could be correlated to the low thiols level.
The GSH content was assessed in some grape and wine samples. The sample preparation is reliable, fast and easy-to-apply. The levels detected were in accordance to the literature. The GSH level during the winemaking was low after pressing according to the must exposure to air. The GSH increased during the fermentation dependent to the yeast strain, the fermentation course and must aeration, as well as to the readily assimilable nitrogen and the copper content. At the end of the alcoholic fermentation, the decrease of GSH concentration was faster if the must preparation was performed in oxidative condition.
The oxidation rate in white wine was evaluated through 2 experiments: in the first one the attention was focused on the interactions between GSH, sulfur dioxide and caffeic acid in depleted phenols wine and synthetic wine solution (12% ethanol, 2.5 g L-1 tartaric acid and pH adjusted at 3.5). In the second experiment, 13 South Africans Sauvignon blanc wines were added with sulfur dioxide and the phenols oxidation was evaluated. The quantification of GSH, caffeic acid and catechin was carried out by the validated UPLC method which was previously described. The statistical analysis showed the oxidation rate was mainly affected by the sulfur dioxide content; when the level of the latter was high the oxygen consumption decreased faster in presence of GSH, too. When GSH and sulfur dioxide were added at higher concentration, the comparison between wine and synthetic wine solution was allowed. The oxygen consumption was at least 2 times higher when the sulfur dioxide was added for 12 of the 13 Sauvignon blanc analyzed. Among the 21 parameters considered, it was mainly affected by the copper, free sulfur dioxide and ferulic acid level which constituted the 68% of the variation of the oxidation rate.
Further investigations are needed to better understand the role of copper either during the grape pressing or the wine ageing as well as the interactions between GSH, sulfur dioxide and phenols occurring in white wine
Polymorphisms of Saccharomyces cerevisiae Genes Involved in Wine Production
No full textThe setting up of new molecular methods for Saccharomyces cerevisiae typing is valuable in enology. Actually, the ability to discriminate different strains in wine making can have a benefit both for the control of the fermentation process and for the preservation of wine typicity. This study focused on the screening of single-nucleotide polymorphisms in genes involved in wine production that could evolve rapidly considering the selective pressure of the isolation environment. Preliminary screening of 30 genes in silico was performed, followed by the selection of 10 loci belonging to 8 genes. The sequence analysis showed a low polymorphism and a degree of heterozygosity. However, a new potential molecular target was recognized in the TPS1 gene coding for the trehalose-6-phosphate synthase enzyme involved in the ethanol resistance mechanism. This gene showed a 1.42% sequence diversity with seven different nucleotide substitutions. Moreover, classic techniques were applied to a collection of 50 S. cerevisiae isolates, mostly with enologic origin. Our results confirmed that the wine making was not carried out only by the inoculated commercial starter because indigenous strains of S. cerevisiae present during fermentation were detected. In addition, a high genetic relationship among some commercial cultures was found, highlighting imprecision or fraudulent practices by starter manufacturers
Genetic polymorphism in Saccharomyces cerevisiae strains isolated from Franciacorta DOCG sparkling wines
No full textEffect of the grape must extraction steps on the content of varietal thiol precursors
Full text linkThe varietal thiols 3-sulfanyl-3-methylpentan-2-one, 3-sulfanylhexan-1-ol and its acetyl ester are the main responsible for boxwood, grapefruit and passion fruit notes of many white wines. These compounds occur in grape only as non-volatile precursors bound to S-glutathionyl- or S-cysteinyl- moieties but they are released by the yeast over the fermentation. However, the amount of these volatile compounds in wine is seldom related to the amount of their precursors in grape [1] because the lyase activity of yeast is a strain-dependent characteristic [2] and the probable contribution of hydrogen sulphide to the neoformation of the volatile thiols [3]. Fracassetti et al. [4, 5] reported massive loss of glutathione and glutathionyl- bounded varietal thiols as result of the grape juice extraction under production in industrial-scale conditions. Particularly, more than 60% of the precursors S-glutathionyl-3-sulfanylhexan-1-ol (GSH-3MH) and its aldehyde form (S-glutathionyl-3-sulfanylhexanal, GSH-3MHAl) got lost from Grillo and Catarratto bianco grape cultivars, the main Sicilian white grape cultivars, as result of the juice extraction. Such a behaviour can seriously detrimentally affect the flavouring properties of the final wine and it points out a further source of the lacking correlation between the amount of precursors in grape and volatile thiols in wine. The reasons for such behaviour were investigated in Grillo grape pressed under industrial-scale production. Must samples were collected after crashing, at draining, at pressing yield of 20%, 40%, 60% and 70%, during transfer in clarification tank, in the clarification tank and after clarification. The must was either air-exposed or air-free during the pre-fermentative steps. Thiol precursors were determined in SPE-purified must samples by UPLC-HRMS [5]. The concentration of thiol precursors detected following the crushing was comparable to the value found in grape, but it dramatically decreases (< 95%) in the must from the press loading. The concentration of thiol precursors increased as the must yield increased, and eventually equals the levels in the grape when a must yield of 60% was achieved. The final loss of thiol precursors was about 80% and 95% for GSH-3MH and GSH-3MHAl, respectively, in the must sampled at the clarification vat (the last juice fraction was excluded). Higher loss of thiol precursors was observed when the must was produced under air-free condition, whereas higher amounts were recorded in laboratory-made must, especially when sodium fluoride or EDTA were added prior the pressing. The results show that the contact of must with the grape skin leads to a loss of thiol precursors. Oxygen seems to be not involved in the oxidative loss of thiol precursor The protective behaviour of the cation-binding compounds suggests that the cations occurring on the grape skin can be responsible for the loss of thiol precursors during the pre-fermentative steps
Ellagic acid derivatives, ellagitannins, proanthocyanidins and other phenolics, vitamin C and antioxidant capacity of two powder products from camu-camu fruit (Myrciaria dubia)
Full text linkThe aims of this study were the evaluation of polyphenols and vitamin C content, and antioxidant capacity of dehydrated pulp powder and the dried flour obtained from the skin and seeds residue remaining after pulp preparation from camu-camu (Myrciaria dudia). Fifty-three different phenolics were characterised by HPLC–DAD–ESI-MS–MS and UPLC-HR-QTOF-MS-MS. The phenolic content of camu-camu flour was higher than that of the pulp powder (4007.95 mg/100 g vs. 48.54 mg/100 g). In both products the flavonol myricetin and conjugates, ellagic acid and conjugates and ellagitannins were detected. Cyanidin 3-glucoside, and quercetin and its glycosides were only found in the pulp powder, while proanthocyanidins were only present in the flour (3.5 g/100 g, mean degree of polymerisation 3). The vitamin C content was lower in pulp powder (3.5%) than in the flour (9.1%). The radical-scavenging capacity of both powders was determined by the DPPH, ABTS and ORAC assays, and was higher for camu-camu flour as could be expected for its higher phenolics and vitamin C content. Comparative analyses with fresh camu-camu berries indicate that some transformations occur during processing. Analysis of fresh berries showed that ellagic acid derivatives and ellagitannins were mainly present in the seeds, while proanthocyanidins were present both in the seeds and skin
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