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.     

Polysaccharide profile and content during the vinification and aging of Tempranillo red wines

Passing from must to wine produced a loss of low-molecular-weight grape structural glucosyl polysaccharides, and an important gain in yeast mannoproteins (MP) and grape-derived arabinogalactan proteins (AGP), and rhamnogalacturonans-II (RG-II). AGP were more easily extracted than RG-II, and small quantities of RG-II monomers and galacturonans were detected. Postmaceration produced a reduction in all grape polysaccharide families, particularly acute in AGP. The reduction of polysaccharides during malolactic fermentation only affected grape AGP, and MP were continuously liberated during the entire vinification process. Wine oak and bottle aging was associated with a relative stability of the polysaccharide families. AGP were thus the majority polysaccharides in young wines but, contrary to what may be thought, structural glucosyl oligosaccharides dominated in musts and MP in aged wines. Precipitation of polysaccharides was noticeable during vinification, and it mainly affected high-molecular-weight AGP and MP. Hydrolytic phenomena affected the balance of wine polysaccharides during late maceration-fermentation.     

Influence of blending on the content of different compounds in the biological aging of sherry dry wines

Principal components analysis to examine the effect of blending (viz. the mixing and transfer of wine between cask rows in a "criaderas and solera" system) on metabolic activity in flor yeasts during biological aging of sherry dry wines was carried out. The variables used in the analysis were the wine compounds most deeply involved in the flor yeast metabolism, namely ethanol, acetaldehyde, glycerol, acetic acid, and l-proline. The greatest blending effect was found to be on the third and second "criadera", which are the stages where the yeasts show a high metabolic activity. The stages holding the oldest wine (viz. the first criadera and the solera) exhibited no differences before and after blending; therefore, the yeasts have a decreased biological activity in them and physical-chemical aging processes seemingly prevail over it.     

Formation of hydroxyphenyl-pyranoanthocyanins in Grenache wines: precursor levels and evolution during aging

Grenache red wines were produced following three different winemaking techniques, that is, small-scale standard experimental wines and industrial-scale wines by both double-mash fermentation and fermentation in Ganimede vats. Wines were analyzed for their color properties, as well as the anthocyanin, flavonol, hydroxycinnamic acid, and pyranoanthocyanin profiles following alcoholic and malolactic fermentation. The evolution of pyranoanthocyanins and their corresponding precursors in the experimental wines was monitored at 6 and 10 months of aging. Wines produced by double-mash fermentation exhibited superior color properties compared to Ganimede wines and the experimental red wines, due to better extraction of flavonols and anthocyanins as well as a lower degree of polymerization. Pyranoanthocyanin formation varied within the different classes of pigments. Vitisins A and B were formed only during alcoholic fermentation. Pinotin A (i.e., the reaction product from malvidin 3-glucoside and caffeic acid) formation took place only during the aging process, whereas formation of hydroxyphenyl-pyranoanthocyanins derived from p-coumaric and ferulic acid followed two different pathways, that is, an enzymatically assisted production during fermentation and a pure chemical formation during aging.     

Hyperoxygenation and bottle storage of Chardonnay white wines: effects on color-related phenolics, volatile composition, and sensory characteristics

The effects of hyperoxygenation on Chardonnay white musts and the influence of subsequent storage on the corresponding wines have been evaluated. Attention was focused on the color characteristics, phenolic and volatile composition, and sensorial analysis, not previously reported in conjunction. On the one hand, the hyperoxygenation treatment provoked a significant decrease in the concentration of virtually all phenolic compounds in musts, young wines, and one-year-stored wines. In addition, a higher resistance to browning was observed in stored wines derived from hyperoxygenated musts. Different storage conditions (light and dark) produced significant differences in the 2-S-glutathionylcaftaric acid derivatives amounts. On the other hand, significant differences were observed in the volatile composition of wines due to the hyperoxygenation treatment, such as a decrease in the isoamylic alcohols concentration, acetaldehyde, and β-damascenone, even after storage under different conditions. Finally, Chardonnay white wines derived from hyperoxygenated musts had higher banana odor and lower herbaceous and flowery notes.     

Sensory and analytical study of rose sparkling wines manufactured by second fermentation in the bottle

The sensory and analytical characteristics of five rose sparkling wines manufactured by the traditional method have been determined. Moreover, the changes that take place in the nitrogen and volatile fraction of the wines during the second fermentation and the aging with the yeasts have been studied. Each of these wines was made from a single industrial rose base wine of the Garnacha Tinta variety, with five selected yeasts strains. The base wine had a low content in free amino acids, 16 mg/L, and the yeast consumed more peptides than free amino acids during second fermentation. From the application of the two-way analysis of variance, yeast strain, and aging time factors to the data of volatile compounds, it has been found that most of the differences between these sparkling wines are due to the aging time. It has been verified that these rose sparkling wines have foam of good quality and that the grape variety Garnacha Tinta is suitable for the production of rose sparkling wines.     

Study of the formation mechanisms of some volatile compounds during the aging of sweet fortified wines.

Sweet fortified wines, traditionally aged under strong oxidation conditions, have a characteristic aroma. An experimental laboratory study investigated the aging of red and white sweet fortified wines under various conditions. The formation of various molecules, previously identified as characteristic of the aroma of this type of wine, was monitored by analysis. The development of these compounds during accelerated aging was affected by oxidation and the color of the wine. Among the molecules studied, sotolon [3-hydroxy-4, 5-dimethyl-2(5H)-furanone] was one of the few molecules present in concentrations above the perception threshold, in both red and white wines. Buildup was strongly affected by the presence of oxygen in white wine subjected to accelerated aging. (Ethoxymethyl)furfural, formed from 5-(hydroxymethyl)furfural, and furfural, derived from sugars, are also involved in the aroma of sweet fortified white wines aged in oxygen-free conditions. The substances most characteristic of accelerated aging of sweet fortified red wines were 5-(hydroxymethyl)furfural, acetylformoin, and hydroxymaltol, the formation of which is affected by oxidation, and dihydromaltol, formed in the absence of oxidation.     

Changes in sulfhydryl content of egg white proteins due to heat and pressure treatment

The sulfhydryl (SH) content of egg white proteins (10% v/v or 9.64 mg of protein/mL) after heat (50-85 degrees C) and combined heat- and high-pressure treatments (100-700 MPa, 10-60 degrees C) was determined using 5',5-dithiobis (2-nitrobenzoic acid) (DTNB), both for the soluble fraction and the total protein fraction. Only irreversible changes were taken into account. Both physical treatments were performed at two pH levels: pH 7.6, corresponding to the pH of fresh egg white, and pH 8.8, corresponding to that of aged egg white. Both heat and combined heat- and high-pressure treatment resulted in an exposure of buried SH groups. These exposed SH groups were involved in the formation of disulfide bond stabilized protein aggregates, as shown by gel electrophoresis. Under severe processing conditions (above 70 degrees C at atmospheric pressure or above 500-600 MPa, depending on the temperature applied), a decrease in total SH content could be observed, probably due to the formation of disulfide bonds by oxidation, especially at alkaline pH when the thiolate anion was more reactive. The high degree of exposure of sulfhydryl groups, and subsequent oxidation and sulfhydryl-disulfide bond exchange reactions resulting in soluble aggregates, can explain why pressure-induced egg white gels are softer and more elastic than heat-induced ones. When pressure treatment was performed at low temperatures (e.g., 10 degrees C), a lower pressure was required to induce similar changes in the sulfhydryl content, as compared to higher temperatures (e.g., 25 degrees C), indicating an antagonistic effect between pressure and temperature in the domain studied (10-60 degrees C, 100-700 MPa). Treatment conditions resulting in extensive protein insolubilization were accompanied by a transfer of free sulfhydryl groups from the soluble to the insoluble protein fraction. These SH groups were mainly accessible to DTNB.     

Determination of antioxidant power of red and white wines by a new electrochemical method and its correlation with polyphenolic content

A new method for measuring the antioxidant power of wine has been developed based on the accelerated electrochemical oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). The calibration (R = 0.9922) and repeatability study (RSD = 7%) have provided good statistical parameters. The method is easy and quick to apply and gives reliable results, requiring only the monitoring of time and absorbance. It has been applied to various red and white wines of different origins. The results have been compared with those obtained by the total antioxidant status (TAS) method. Both methods reveal that the more antioxidant wines are those with higher polyphenolic content. From the HPLC study of the polyphenolic content of the same samples, it is confirmed that there is a positive correlation between the resveratrol content of a wine and its antioxidant power.     

Free radical scavenging capacity in the aging of selected red Spanish wines

Free radical scavenging capacity by the DPPH(*) method and main physicochemical properties, polyphenols content by HPLC, color by a tristimulus colorimeter, and UV-vis spectra in the aging of selected red Spanish wines, were studied. As the wines age, they become darker (lower lightness, L) and increase their hue angle (lower red color) as well as the ratio of absorbance at 420 nm to that at 520 nm. Main polyphenolics identified in the samples were tannic acid, oenin, and gallic acid. The antiradical efficiency of the samples increased during aging, which could be related to an increase in the tannic acid concentration shown by the following correlationship: EC(50) = 1/(0.18 + 0.0011[tannic acid](mg/L)) with a correlation coefficient of 0.744.     

Changes in phenolic content of tomato products during storage

The effect of storage on the total polyphenol content and individual phenolic compounds as well as on the hydrophilic antioxidant capacity of ketchups and tomato juices was studied. The total polyphenol content was determined using the Folin-Ciocalteu assay, and the antioxidant capacity of the hydrophilic fraction was determined using DPPH and ABTS(+) assays. Individual polyphenols were identified and quantified using liquid chromatography/electrospray ionization tandem mass spectrometry on a triple quadrupole. All analyses were carried out for ketchups and tomato juices after storage for 3, 6, and 9 months. The total polyphenol content and antioxidant capacity of the hydrophilic fraction decreased during storage of ketchups and tomato juices. Ketchups, in general, showed a slightly greater stability during storage than tomato juices. The most significant decrease was observed for quercetin followed by caffeic and ferulic acids, whereas glycosilated polyphenols showed greater stability during storage.     

Impact odorants of different young white wines from the Canary Islands

Five young monovarietal white wines from the Canary Islands made from Gual, Verdello, Marmajuelo, white Listán, and Malvasia grape cultivars were studied to determine the characteristics of their most important aromas and the differences among them. The study was carried out using gas chromatography-olfactometry (GC-O) to detect the potentially most important aroma compounds, which were then analyzed quantitatively by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. The strongest odorants in the GC-O experiments were similar in all cases, although significant differences in intensity between samples were noted. Calculation of the odor activity values (OAVs) showed that 3-mercaptohexyl acetate was the most active odorant in the Marmajuelo and Verdello wines, as were 3-methylbutyl acetate in the Gual wine, beta-damascenone in the Malvasia wine, and ethyl octanoate in the white Listán wine. However, the most important differences between varieties were caused by the three mercaptans (3-mercaptohexyl acetate, 3-mercaptohexanol, and 4-methyl-4-mercapto-2-pentanone) and the vinylphenols (4-vinylphenol and 2-methoxy-4-vinylphenol). The correlation between the olfactometric values and the OAVs was satisfactory in the cases when the compound eluted in the GC-O system was well isolated from other odorants and had aromatic importance and the OAVs for the different wines were sufficiently different.     

New method for reducing the binding power of sweet white wines

Sulfur dioxide is now considered to be a toxic chemical by most world health authorities. However, it remains an irreplaceable additive in enology for wine conservation, combining antioxidant and antibacterial properties. Sweet white wines from botrytized grapes retain particularly high SO 2 levels due to their high sulfur dioxide binding power. This paper presents a new method for reducing this binding power by removing some of the carbonyl compounds responsible, which are naturally present in these wines. The main carbonyl compounds responsible for the SO 2 binding power of sweet wines were removed, that is, acetaldehyde, pyruvic acid, 2-oxoglutaric acid, and 5-oxofructose. The method retained was selective liquid-solid removal, using phenylsulfonylhydrazine as a scavenging agent. The scavenging function was grafted on different classes of porous polymer supports, and its efficiency was evaluated on sweet white wines under conditions intended to conserve their organoleptic qualities. The results obtained showed that the method was efficient for removing carbonyl compounds and significantly reduced the binding power of the wines. Sensory analysis revealed that this process did not deteriorate their organoleptic qualities.     

Total phenolic content, antioxidant activity, and cross-cultural consumer rejection threshold in white and red wines functionally enhanced with catechin-rich extracts

White and red wines spiked with catechin-rich green tea extract and grape seed extract were assessed for phenolic content, antioxidant activity, and cross-cultural consumer rejection thresholds in relation to wine as a functional food. Health functionality is an important factor in functional foods, and spiking pure compounds or plant extracts is an effective method to increase or control functionality. The total phenolic content and antioxidant activity were measured in wines spiked to different extract concentrations, namely, control and 50, 100, 200, 400, and 800 mg/L, to confirm the dose-response curves in both white and red wines. Consumer rejection thresholds (CRTs) were established for spiked wines in a Korean and in an Australian population. Our results showed that the green tea extract and grape seed extract increased the antioxidant activity dose dependently, and the CRTs varied considerably between the Korean and the Australian groups, with Koreans preferring wines spiked with green tea extract and Australians showing a preference for wines spiked with grape seed extract. These results have implications for producing wine products that are enhanced in phenolic compounds and targeted to different cultural groups.     

Behavior of monosaccharides, phenolic compounds, and color of red wines aged in used oak barrels and in the bottle

A red wine with appropriate basic quality characteristics for aging was stored in oak barrels for 12 months and then bottled and aged for a further 6 months. The same ambient conditions of temperature and humidity were maintained throughout the entire aging process. The barrels used were made from three different species of oak by four different cooperages and had been used for at least two years. Analysis of variance and principal component analysis were run on the values for hexoses, pentoses, total anthocyanins, ortho-diphenols, low- and high-polymer polyphenols, and color parameters to study the behavior of the monosaccharides and polyphenols in response to the factors of aging time, the oak variety employed, and the source cooperage where the barrels had been made. Time trends for all the phenolic components were directly related to aging time, with low-polymeric polyphenols (LPPs) being the most affected by wood type and source cooperage. Wine color was defined by a basic red color which decreased with aging time in the barrel and was altered by yellowish pigment components differing for each of the barrels in which oxidative aging took place and by increased stability of the blue copigments. Principal component analysis showed that samples of the same source wine aged in different barrels tended to be grouped together according to each of the aging intervals considered.     

Fermentation of white wines in the presence of wood chips of American and French oak

Must obtained from Airén grapes was fermented in the presence of wood chips (4 and 7 g/L) of either French oak (from Vosges, central France, and Allier zones) or American oak. Fermentation yields were higher than in the control fermentations carried out in the absence of wood, and production of volatile substances during fermentation (alcohols, esters, and acetates) was also higher. The volatile substances that leached out of the wood were analyzed by GC-MS-SIR. The results showed that their concentrations depended on the type and amount of the oak; some of these substances were consumed in part by the yeasts during fermentation. A taste panel favorably assessed the wines produced by fermentation in the presence of oak chips, which retained part of the must original fruity aroma.     

Phenolic compounds and browning in sherry wines subjected to oxidative and biological aging

The composition in hydroxybenzoic and hydroxycinnamic acids, hydroxycinnamic esters, tyrosol, syringaldehyde, and flavan-3-ol derivatives of three different types of sherry wine obtained by aging of the same starting wine under different conditions was studied. So-called "fino" wine was obtained by biological aging under flor yeasts, "oloroso" wine by oxidative aging, and "amontillado" wine by a first stage of biological aging followed by a second oxidative step. On the basis of the results, the wines subjected to oxidative aging exhibited higher phenol contents, in addition to scarcely polar compounds absorbing at 420 nm that were absent in the wines obtained by biological aging. Taking into account that flavan-3-ol derivatives play an important role in wine browning, a model catechin solution was inoculated with flor yeast which, contrary to the findings of other authors in the absence of yeasts, formed no colored compounds. This different behavior may account for the resistance to browning of pale sherry wines in the presence of flor yeasts.     

Changes of the metal composition in German white wines through the winemaking process. A study of 63 elements by inductively coupled plasma-mass spectrometry

Elemental patterns are often used for the classification or identification of the origin of wines. A prerequisite is that the concentration of the elements is not strongly influenced by the addition of different substances such as yeast and fining products during the winemaking process. Inductively coupled plasma-mass spectrometry (ICP-MS) has been used in this study to determine in total 63 elements (including some nonmetals and the rare earth elements) in five German white wines from five regions of origin. The whole winemaking process was studied, from the must to the ready wine. Microwave acid digestion was used for sample preparation, and indium was added as internal standard for a semiquantitative analysis. Two winemaking processes were compared: with the addition of clarifying agents (bentonites) before and after the fermentation. The concentration of only a few elements such as Li, B, Mg, Ca, Rb, Cs, and Pb seems to be constant throughout the whole winemaking process (changes of <+/-50%) and are independent of the time of addition of the bentonites. When bentonites are added before fermentation, the concentration of other elements, such as V, Co, and Fe, remains constant. If bentonites are added after fermentation, the concentration of some other elements such as Sr, Zn, and Mn is nearly unaffected. These elements are therefore robust elements for origin studies in German white wines.     

Response of the aroma fraction in sherry wines subjected to accelerated biological aging.

The effect of an acceleration assay, carried out with a periodic aeration and an increased surface/volume ratio, on various aroma compounds of "fino" Sherry wines aging under a veil of a pure culture of Saccharomyces cerevisiae race capensis G1 flor film yeast was studied. The results were subjected to multifactor analysis of variance, and the compounds simultaneously depending on acceleration conditions and aging time at p < 0.01 were subjected to principal component analysis. The first component, accounting for 86.14% of the overall variance, was mainly defined by acetaldehyde and its derivatives 1,1-diethoxyethane and acetoin. These compounds reached higher concentrations in accelerated aging wines in a shorter time than they did in control wines, and no browning problems were detected. Taking into account that these compounds can be used as indicators for biological aging of "fino" Sherry wines, the acceleration condition assayed can be applied to shorten the time of this process.     

Maturing wines in oak barrels. Effects of origin,volume, and age of the barrel on the wine volatile composition

The influence of the oak origin, volume, and age of the barrel on the volatile composition of a red wine after six months of maturation have been studied. Major volatile compounds in wine were determined using liquid-liquid extraction with dichloromethane, and those volatiles being due to the oak were determined by extraction with pentane-ether using deuterated analogues as internal standards. The results show that there is little difference between the volatile composition of wines matured in French oak barrels and those matured in American oak barrels. The concentration of cis-oak lactone was the most significant difference. The greatest instrumental and sensory differences were found between new and used barrels, with important decreases in lactones and vanillin concentration in used barrels. When studying the effect of the volume of the barrel, the characteristics of the wine matured in 220-L new barrels versus those matured in 1000-L new barrels were very different. In new barrels, the larger the volume of the barrel, the lower the concentrations of those compounds responsible for the oaky aroma. These differences were less evident when comparing wines matured in used barrels with different capacities.