Dry White Wines Research Articles

Quantification method and organoleptic impact of added carboxymethyl cellulose to dry white wine

Following the resolution Oeno 2-2008 of the OIV, "Organisation Internationale de la Vigne et du Vin", the addition of carboxymethyl cellulose (CMC) in wines at a concentration lower than 100 mg L-1 is authorized in the EU (RCE 606-2009). In order to control this level, a method has been elaborated to quantify CMC addition at the maximum limit authorized. It is based on the absorbance level of a coloured complex obtained by the addition of a solution of 2,7-dihydronaphthalene in concentrated sulfuric acid to a dry white wine that has been dialyzed; the proposed method has a quantification limit of 60 mg L-1 with a 40 mg L-1 uncertainty. Despite these relatively high values, the method is, nevertheless, suitable for its purpose. Some wines, elaborated and CMC supplemented, allowed one to test the CMC quantification method, in real conditions of wine production. All the measurements provide a CMC quantification at the expected level, within the uncertainty. These samples, sets of treated and untreated wines, were submitted to sensory evaluation to assess the impact of CMC addition to wine. At the maximum authorized level, no significant difference was detected by the 20 expert panel under quality control requirements. Moreover, some experiments, performed to determine the concentration threshold at which the CMC effect is noticeable, showed that even at a level 15 times higher than the maximum amount authorized, CMC has no impact on the taste or the nose of the wines.

Identification of a Sotolon Pathway in Dry White Wines

Sotolon (3-hydroxy-4,5-dimethyl-2(5H)-furanone) is a chiral furanone, an aroma compound known to be responsible for premature-aging flavor in dry white wines. Sotolon generally results from mild oxygenation during bottle aging, and until now, its formation pathways had not been elucidated. The ability of the main precursors described in the literature under very different experimental conditions to produce sotolon was tested. In model wine solution maintained at 40 degrees C for 6 months, sotolon was produced by the oxidative degradation of ascorbic acid. By use of GC-MS, 2-ketobutyric acid, produced by the oxidative degradation of the ascorbic acid in the model wine solution, was identified as a potent precursor of sotolon in this pathway. Ascorbic acid is an exogenous compound, added before bottling, but 2-ketobutyric acid was found even in white wines that had not been supplemented. Consequently, this sotolon formation pathway is also valid in white wines with no added ascorbic acid. In addition, we showed that Saccharomyces cerevisiae strains were capable of producing variable concentrations of this ketone during alcoholic fermentation. In model wine solution, certain yeast strains released large quantities of 2-ketobutyric acid, similar to those found in oxidized dry white wines. In view of these results, the role of yeast strains in this premature-aging phenomenon of dry white wines is discussed. Finally, these investigations revealed that one chemical mechanism responsible for the low concentrations of sotolon found in prematurely aged white wines made from various grape varieties was an aldol condensation between 2-ketobutyric acid and acetaldehyde.

Aromatic potential of botrytized white wine grapes: Identification and quantification of new cysteine- S-conjugate flavor precursors

Sweet wines made from botrytized grapes contain much higher concentrations of volatile thiols, especially 3-sulfanylhexan-1-ol (3SH), than dry white wines. Three new specific volatile thiols (3-sulfanylpentan-1-ol (3SP), 3-sulfanylheptan-1-ol (3SHp), and 2-methyl-3-sulfanylbutan-1-ol (2M3SB) were recently identified in Sauternes wines. Like most volatile thiols, these compounds were almost totally absent from must, mainly being formed during alcoholic fermentation. In this work, we describe the identification and quantification of three new cysteine- S-conjugate precursors in must made from Botrytis-infected grapes. S-3-(pentan-1-ol)- l-cysteine (P-3SP), S-3-(heptan-1-ol)- l-cysteine (P-3SHp), and S-3-(2-methylbutan-1-ol)- l-cysteine (P-2M3SB) were identified by direct GC–MS analysis of their derivative forms obtained by silylation of an enriched fraction, isolated from must by affinity chromatography. Concentrations were considerably higher when Botrytis cinerea had developed on the grapes. In botrytized must, the mean levels of P-3SP, P-3SHp, and P-2M3SB were in the vicinity of 700, 50, and 500 nM, respectively, whereas concentrations in healthy must ranged from 0 to 50 nM. This indicated that these three new sulfanyl alcohols, responsible for the characteristic aroma of botrytized wines, were formed by the yeast metabolism during alcoholic fermentation from the corresponding non-volatile cysteine- S-conjugate precursors. Moreover, these results highlighted the predominant role of botrytization in developing grape aroma potential.

The effects of saliva on the erosive potential of three different wines

The erosive potential of wine on teeth may be modified by the buffering capacity of saliva. This potential effect was studied for three different wines in vitro and in vivo. The buffering capacity was studied in vitro by stepwise addition of small volumes of a dry white wine, a medium sweet white wine and a red wine to collected stimulated saliva. In vivo, this was studied by six volunteers vigorously rinsing 5 mL of each wine in their mouth for 15 to 45 seconds. Changes in salivary flow rate and pH were measured during a period of 10 minutes after rinsing with 5 mL wine. pH values < 5.5 were observed in vitro after addition of 0.2 mL dry white wine and medium sweet wine and after 0.3 mL red wine to 1 mL saliva. During rinsing with all wines, the intra-oral pH decreased to below 4 within 15 seconds and remained below this value for at least 45 seconds. After expectoration, the salivary pH remained significantly low for two to six minutes, despite a doubling of the flow rate observed during the first two minutes. Vigorously rinsing wine induced a decrease in intra-oral pH of significant degree and duration, which increases the risk of developing dental erosion.

Who will win the Premiership, Mr Obama?

Is it possible to read any publication without it mentioning Barack Obama, the man with all the answers? Can he tell us, for example, which of Liverpool and Manchester United will win the Premiership? Or how long the Jade Goody effect on uptake of cervical screening will last? Only God and perhaps Obama know. The JRSM has been as guilty as any with references to the new American President but the genius of Obama's success is that he is at the heart of the global debate on almost any topic. Farooq and colleagues begin this issue by using Obama as a journalistic hook for a bold plea for the feminization of orthopaedic surgery (JRSM 2009;102:124–5). Last year, Clare Marx was elected the first female president of the British Orthopaedic Association, a revolutionary gesture for a specialty caricatured by beer-swilling rugby-playing bruisers. Hence inevitably female medical students view a career in orthopaedic surgery as too physical, a hindrance to family, biased towards men and a submission to antisocial hours. But the authors argue that female role models, and the change in work pattern forced by the European Working Time Directive, might help women to ‘smash through the reinforced concrete ceiling of orthopaedic surgery’. A more balanced workforce will also help better serve patients, they conclude. Meanwhile, Minhas and Wendt focus more keenly on Obama and his health policy (JRSM 2009;102:129–33). Obama's attention has naturally been on the US economy but should that excuse the fact his victory speech failed to mention healthcare, and only a passing reference was made in his inauguration speech? Nonetheless, healthcare will come under increasing focus, argues Noam Chomsky, because of the unsustainable financial impact on corporate America. Obama's strategy on healthcare is not only dictated by the state of the economy but also by the legacy of his current Secretary of State, Hillary Clinton. Her brand of ‘Hillarycare’ was criticized by experts, employers and republicans. Obama's reforms are unlikely to stretch to ‘socialized medicine’, in other words an NHS-type system, argue the authors, but the US system holds a perpetual fascination for UK policy-makers who look to it for useful lessons and welcome US companies and ideas to the NHS. A glass of dry white wine, supper en famille and 15 minutes on a back massage machine might be taken from Barack Obama's book of top 10 relaxation tips from the master of the world. Instead, this is the preferred method of winding down at the end of the working day for Trisha Greenhalgh, the mistress of ‘doing the juggle’ – holding down an academic job while also being a wife and mother and managing major life events in the extended family (JRSM 2009;102:165–6). Greenhalgh kicks off our new series on the working days of 21st-century medics. A must read for everybody seeking to smash a reinforced concrete ceiling or just escape Barack Obama for a few minutes.

Compositional Corrections Applied in Obtaining Semi Dry and Semi Sweet White Wines in Iasi Vineyard

Compositional corrections - sugar and acid adjustments, as well as biological degradation of malic acid, wines blending- are used to enhance or diminish the content of certain substances. Feteasca alba, Feteasca regala, Muscat Ottonel and Tamâioasa româneasca grape varieties, harvested in 2008 from Iasi vineyard, center of Copou-Adamachi farm were used. The grapes were processed through the classic technology of obtaining white dry wines. The wines were corrected with rectified concentrated must (RCM) and concentrated must (CM) in order to obtain semi-dry and semi- sweet wines. Tartaric acid was also added. The analyses were done according to international standards and specific literature. The main physical-chemical characteristics of the obtained wines show an increase in reductive sugars, non-reductive extract and density.

Sweeter than wine? The use of the grape in early western Asia

AbstractEmotional news for lovers of a dry white wine. The blissful Hippocrene was composed from wild grapes from the sixth millennium BC in the lands of its natural habitat. But, as the author shows, the cultivation, domestication and selective breeding of the grape following in the Late Neolithic to Early Bronze Age was aimed primarily at the enjoyment of its sweetness.

The Effect of Glycerol on the Perceived Viscosity of Dry White Table Wine

The effect of glycerol on the perceived viscosity of dry white wines was investigated using direct paired comparison sensory methods. Before tasters assessed wines for viscosity, the natural sweetness of glycerol needed to first be masked. This was achieved using two novel methods—prior oral exposure to the anti-sweetness agent Gymnema sylvestre, and by sweetness equalisation using a non-viscous high potency artificial sweetener. After masking its sweetness, the addition of 6 g/L of glycerol did not increase the perceived oral viscosity of dry white wine suggesting that glycerol does not play a role in the perception of dry white wine viscosity. Therefore, palate viscosity in dry white wine cannot be enhanced by employing traditional winemaking approaches that elevate glycerol levels.

Changes in the Sotolon Content of Dry White Wines during Barrel and Bottle Aging

GC-MS in electron ionization mode (EI) was used as a simple, sensitive method for assaying sotolon [4,5-dimethyl-3-hydroxy-2(5) H-furanone] in various dry white wines. The impact of barrel-aging conditions, that is, whether yeast lees were present or not, on the formation of sotolon in dry white wines was then studied. The sotolon content was highest in dry white wines aged in new barrels without lees, often exceeding the perception threshold (8 microg/L). These results demonstrated that yeast lees were capable of minimizing the formation of sotolon in dry white wines during aging. The sotolon and oxygen contents of several bottle of the same white wine were also compared 7 years after bottling. At the range of dissolved oxygen concentrations generally measured, between 5 and 100 microg/L, the sotolon content remained below its perception threshold in wine. The perception threshold was exceeded only in wines with oxygen concentrations above 500 microg/L. The presence of dissolved oxygen in the wine samples analyzed also resulted in a decrease in their free sulfur dioxide content.

Distribution and Organoleptic Impact of Sotolon Enantiomers in Dry White Wines

The enantiomers of sotolon, a flavor compound typical of oxidized white wines, were separated by preparative HPLC to determine their perception thresholds and distribution in wines. The enantiomeric ratios of chiral sotolon were evaluated in several dry white wines using gas chromatography and a chiral column (beta-cyclodextrin) connected to a 2 m precolumn (BP20). The perception threshold of (S)-sotolon (0.8 microg/L) in model wine solution was 100 times lower than that of the (R) form (89 microg/L), indicating that (S)-sotolon contributes to the characteristic aroma of prematurely aged dry white wines. Both enantiomers are detected in white wines. Analysis of commercial dry white wines from various vintages and origins revealed three types of distribution patterns: the racemic form, an excess of R, and an excess of S. The proportions found in these wines may be partially explained by the slow racemization kinetics (20 months) of optically active sotolon.

Ochratoxin a occurrence in Greek dry and sweet wines

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: To assess ochratoxin A (OTA) presence in Greek wines, according to the production area and the technology, as OTA risk is higher in wines from southern Europe. The effect of fining agents was examined in order to investigate OTA reduction.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Dry and sweet wines issued from research programs and trade wines were analyzed, according to the official HPLC method. Greek dry wines do not exceed the European limit of 2 ng/mL. The amount of OTA (in ng/mL) varies between 0 - 1,18 for dry white wines, 0 -1,00 for dry red wines. Among sweet wines, only fortified wines without alcoholic fermentation range between 0,50 -7,64, while other sweet wines range between 0,05 -1,73. Dry yeast reduced OTA by 25 - 60 % according to dosage and duration (1-10 weeks) while the effect of bentonite was 33 - 40 % reduction for a treatment of 3-6 days.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;: The picture for Greek wine production is positive, even in case of a future lowering of the European limit. OTA risk seems higher in the islands, particularly for some dessert wines. Results from wine treatment with fining agents support the theory of OTA adsorption onto suspended solids and the beneficial effect of yeast presence.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of study&lt;/strong&gt;: Assessment of OTA danger for Greek wines and information concerning the effect of fining agents contribute to the production of wines free from contaminants and support wine economy.&lt;/p&gt;

Metalloporphyrin - based Electronic Tongue: an Application for the Analysis of Italian White wines.

An Electronic Tongue system (ET) composed of "all-solid-state" potentiometricsensors was developed and applied for the identification of white wines. The sensingproperties were due to the PVC based membranes doped with several metallo-porphyrinsdeposited on the surface of glassy carbon working electrodes; potentiometric responsetowards several ions in a concentration range from 10-5 M to 10-1 M were studied and cross-sensitivity of sensors was estimated. The sensor array was applied both for the classificationand quantitative analysis of "Verdicchio D.O.C." Italian dry white wines produced by ninecantinas. Peculiar parameters of white wines (namely alcoholic degree, volatile acidity, SO₂,L-Malic Acid, L-Lactic Acid and Total Polyphenols) individuated by standard analyticalmethods were compared with the values evaluated by metalloporphyrin-based ET. Thesystem satisfactory discriminates between an artificial wine control and analyzed winescoming from different cantinas and produced in different years. A satisfactory correlationbetween results of wine analysis performed by certified methods and ET response has beenobtained for SO₂, L-Malic Acid, and Total Phenols content. The developed procedureallows the monitoring of the acetic acid amount in wines and hence to control wine volatileacidity, so indicating the initial steps of wine spoilage process.

Impact odorants of Chardonnay dry white wine from Changli County (China)

Effect of volatile compounds’ contribution to the overall aroma of Chardonnay wines from Changli County was first investigated in this research. Wine aroma compounds were extracted by solid-phase micro-extraction fibers, then they were submitted to gas chromatography-mass spectrometry (GC–MS). A total of 41 volatile compounds were identified and quantified. In the volatiles detected, higher alcohols, esters and fatty acids are the main chemicals. According to their odor active values (OAVs), 13 volatile compounds were considered to be the powerful impact odorants of this wine. They are β-damascenone, isopentyl acetate, phenethyl acetate, ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl lactate, ethyl decanoate, isopentyl alcohol, 2-phenyl-ethanol, hexanoic acid, octanoic acid and n-decanoic acid. Odor descriptions of the impact volatiles suggested that Chardonnay wines from Changli County was a pleasant floral and fruity odor product.

Classification of Wines Based on Combination of 1H NMR Spectroscopy and Principal Component Analysis

AbstractA combination of 1H nuclear magnetic resonance (NMR) spectroscopy and principal component analysis (PCA) has shown the potential for being a useful method for classification of type, production origin or geographic origin of wines. In this preliminary study, twenty‐one bottled wines were classified/separated for their location of production in Shacheng, Changli and Yantai, and the types of the blended, medium dry, dry white and dry red wines, using the NMR‐PCA method. The wines were produced by three subsidiary companies of an enterprise according to the same national standard. The separation was believed to be mainly due to the fermentation process for different wines and environmental variations, such as local climate, soil, underground water, sunlight and rainfall. The major chemicals associated with the separation were identified.

The effects of ethanol and glycerol on the body and other sensory characteristics of Riesling wines

The effect of ethanol and glycerol concentration on the body, sweetness, acidity, aroma and flavour intensity, and perceived viscosity and hotness of three Riesling wines was assessed. The ethanol and glycerol contents of the wines were adjusted by addition to give three realistic levels (5.2, 7.2, 10.2 g/L glycerol and 11.6, 12.6 and 13.6 v/v ethanol). The nine treatment combinations (3 glycerol × 3 ethanol) were rated on the above attributes by a panel of trained tasters. Increased alcohol levels resulted in increased perceived hotness in all wines, and in higher body and perceived viscosity in two of the three wines. The effect of increasing glycerol content was less consistent with only one of each of the three wines showing increased viscosity and body. However, the mean viscosity ratings given to wines with 10 g/L glycerol was higher than at 5 g/L at all alcohol levels and for all wines, suggesting that differences in glycerol concentration typically displayed between dry white table wines can affect their perceived viscosity. Neither alcohol nor glycerol consistently affected sweetness, acidity, aroma or flavour intensity. Higher ratings of the abstract term 'body' were most commonly associated with higher ratings of flavour and/or perceived viscosity, suggesting that for the majority of tasters, these two attributes contributed to their interpretation of the term 'body'. Perceived hotness was not an important component of body, while the role of acidity in body perception was taster dependent.

Assay of glutathione in must and wines using capillary electrophoresis and laser-induced fluorescence detection: Changes in concentration in dry white wines during alcoholic fermentation and aging

Glutathione (GSH) was assayed in must and wine using capillary electrophoresis coupled with laser-induced fluorescence (LIF) detection. Sample preparation involved conjugating thiols with monobromobimane (MBB) in a 2-( N-cyclohexylamino)ethanesulfonic acid [CHES] buffer (179 mM). The electrophoretic conditions were 30 kV with a capillary length of 105 cm from the inlet to the detector (120 cm total length) and a 50 μm inner diameter. Under these conditions, the complete separation from the other main non-volatile thiols took less than 20 min. We also described the optimum conditions for derivatizing wine samples with MBB to increase eletrophoretic sensitivity. The detection limit for glutathione assay is 65 nmol/L. This simple, sensitive method provides a specific assay of glutathione in reduced form, as the sample preparation technique does not modify the balance of oxidized and reduced forms. We used this method to monitor changes in the reduced glutathione content of a white wine during alcoholic fermentation and barrel aging.

Characterization of key-aroma compounds of botrytized wines, influence of grape botrytization

Botrytized wines (BW) are famous for their distinctive, complex aromas. To date, only a few studies have analysed the volatile compounds involved in their typical flavours. In this paper, GC–O was applied to BW and dry white wines (DW) made from the same grape varieties to characterize the main odorants responsible for their sensory differences. Surprisingly, only two odorous zones, with grapefruit or curry nuances, were apparently specific to BW. However, GC–AEDA revealed important differences in the FD values between BW and DW, making it possible to screen potent odorants of BW, such as 3-mercaptohexan-1-ol, homofuraneol ®, furaneol ®, sotolon, methional, and phenylacetaldehyde. GC–MS quantification of homofuraneol ®, furaneol ®, norfuraneol ®, phenylacetaldehyde, and methional in 14 BW, mostly at levels above their perception thresholds, confirmed their contribution to the aroma of BW. Increased concentrations of some of these odorants in BW were shown to be associated with grape botrytization, partially through the desiccation process.

Stereoisomeric Distribution of 3-Mercaptohexan-1-ol and 3-Mercaptohexyl Acetate in Dry and Sweet White Wines Made fromVitis vinifera(Var. Sauvignon Blanc and Semillon)

The enantiomeric distribution of 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA) in Vitis vinifera wines was determined by combining two techniques: specific purification of volatile thiols from the wines using p-hydroxymercuribenzoate and separation of the chiral molecules by gas-phase chromatography on a cyclodextrin capillary column. The R and S enantiomer ratios of these two thiols in dry white Sauvignon blanc and Semillon wines are approximately 30:70 for A3MH and 50:50 for 3MH. However, in sweet white wines made from grapes affected by "noble rot" due to the development of Botrytis cinerea on ripe grapes, the proportion of the R and S forms of 3MH is in the vicinity of 30:70. During alcoholic fermentation, a change in the ratio of the two enantiomers of 3MH in dry white wines was observed. At the beginning of fermentation (around density 1.08), the S form represented over 60%; then, at lower density, as fermentation proceeded, the enatiomeric ratio approached 50:50. The ratio of the two 3MHA enantiomers remained constant throughout fermentation. On the contrary, the distribution of the two 3MH enantiomers changed very little during fermentation of the botrytized sweet wines. The perception thresholds for the R and S forms of 3MH in hydroalcoholic model solution are similar (50 and 60 ng/L). These two enantiomers have quite different aromas: The R form is fruitier, with a zesty aroma reminiscent of grapefruit, while the S form smells more of passion fruit. The perception thresholds of the R and S enantiomers of 3MHA are slightly different (9 and 2.5 ng/L). The less odoriferous R form is reminiscent of passion fruit, while the S form has a more herbaceous odor of boxwood.

Development and Applications of a Bienzymatic Amperometric Glycerol Biosensor Based on a Poly(Neutral Red) Modified Carbon Film Electrode

A bienzymatic biosensor for glycerol has been designed, based on the co‐immobilization of two enzymes, glycerol kinase and glycerol‐3‐phosphate oxidase, the glycerol kinase phosphorylating glycerol to glycerol‐3‐phosphate. The enzymes were immobilized by cross‐linking with glutaraldehyde on carbon film electrodes with poly(neutral red) as mediator of the enzymatic reaction. The polymer film was made on the carbon film substrate by potential cycling from a solution containing 1 mM neutral red. Glycerol, as well as glycerol‐3‐phosphate, was determined in amperometric mode at −350 mV vs. saturated calomel electrode. Several buffers and pH values were tested for the immobilized enzymes' response and the optimum experimental conditions were found to be in phosphate buffer at pH 8.0. The linear response range to glycerol was directly dependent on the concentration of adenosine‐5′‐triphosphate (ATP). With 3 mM ATP, glycerol was determined in the range 5–147 µM. A monoenzymatic glycerol‐3‐phosphate biosensor was also evaluated and found to have a working range from 20–700 µM. Application of the bienzymatic biosensor to natural samples was tested by glycerol determination in dry white and red wines and the method was validated by spectrophotometric enzyme assay.

PVPP−Polyphenol Complexes: A Molecular Approach

In dry white wines, two different forms of instability occur: (i) substantial yellow or yellow-green deposits are observed principally due to flavonol quercetin; and (ii) protein instability leads to protein casse. Polyvinyl polypyrrolidone (PVPP) is used to adsorb phenols from beverages, and bentonite is used to eliminate heat instable protein. However, in both cases, their effects are still largely unknown. This study uses a multitechnique approach to gain a better molecular understanding of the association of polyphenol aglycones with PVPP compared to that of glucosides with PVPP. The work demonstrates, that with aglycones, three forces drive complex formation: hydrophobic interaction, H bonds, and van der Waals bonds. With glucosides, the sugar moiety removes or reduces these driving forces. Thus, if the interaction between proteins and polyphenols is responsible for haze and precipitates, as is classically assumed, PVPP could prevent quercetin sedimentation.