Protein haze formation in white wines: effect of saccharomyces cerevisiae cell wall components prepared with different procedures

Cell wall material was extracted by five different methods from an oenological strain of Saccharomyces cerevisiae. Enzyme preparations containing beta-glucanase activity (Zymolyase, Glucanex, and Finizym 250L) allowed a better extraction yield compared to that of dithiothreitol (DTT) and EDTA. The yeast extracts were only soluble in part in wine. The wine-soluble fraction (WSF) of the five extracts, differing in both protein and sugar contents, when added in increasing amounts to white wine differently affected protein haze formation, as determined by the heat test, giving dose/response curves of different shapes. The curves obtained with the WSF derived from DDT and Zymolyase extracts showed a plateau value corresponding to 90% and 80% of wine haze reduction, respectively. In contrast, addition of the WSF derived from the other extracts resulted in increased turbidity with respect to the original wine. The mannoproteins (MP), isolated from each yeast extract by Concanavalin-A chromatography, gave dose/response curves showing shapes more similar among them than those obtained with the whole WSFs. The best wine stabilization was obtained with the MP of the DTT and Zymolyase extracts. The supernatants obtained after heating the MP of the different extracts were also tested. The stabilizing effect of the heat-stable MP (HSMP) was always larger than that of the corresponding total (un-heated) MP. The HSMP obtained starting from the DTT and Zymolyase extracts showed the best haze-protecting effect, which was, however, lower than that obtained with their corresponding WSF. This result suggests that wine protein stabilization by compounds of the yeast cell wall could be related, in addition to the action of the MP, also to the presence of other substances of different nature.     

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.     

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.     

Influence of grape-harvesting steps on varietal thiol aromas in Sauvignon blanc wines

The intense tropical fruit aroma of Sauvignon blanc wines has been associated with the varietal thiols 3-mercaptohexanol (3MH), derived from odorless precursors in the grape, and 3-mercaptohexyl acetate (3MHA), arising from 3MH during fermentation. Grapes and juice were sourced from five locations in Marlborough, New Zealand, taking hand-picked grapes and samples at four stages during the mechanical harvesting process and pressing, which were then fermented in replicated 750 mL bottles. With each set of juices, the highest concentrations of Cys-3MH and Glut-3MH were found in the juices pressed to 1 bar, but these juices produced wines with lower 3MH and 3MHA concentrations. With three of the juices, there was an increase in varietal thiol content for wines made from juices that had been machine harvested compared to the hand-picked samples, which matched earlier findings of lower 3MH and 3MHA levels in wines made from hand-picked grapes. Juices that were more oxidized, and which showed a higher absorbance at 420 nm, were found to produce wines with lower 3MH and 3MHA concentrations.     

Effect of Schizosaccharomyces pombe on aromatic compounds in dry sherry wines containing high levels of gluconic acid

Volatile compounds have been determined in control dry sherry wines and those supplemented with gluconic acid, which were inoculated with the Schizosaccharomyces pombe 1379 (ATCC 26760) yeast strain. These compounds were grouped, according to volatiles exhibiting the identical odor quality, into nine groups of the same odor character (aromatic series) as a way of establishing the aroma profile for the studied wines. Control and supplemented wines showed changes in the balsamic, spicy, roasty, and fruity aromatic series, and tasters judged the aroma as typical of wines subjected to biological aging. This fission yeast may be used as a treatment to reduce gluconic acid contents in wines obtained from rotten grapes, making feasible the incorporation of these wines into the biological aging process. In addition, this procedure may also help to accelerate the traditional biological aging in sherry winemaking due to the contribution of some specific compounds by S. pombe to the wine.     

Discrimination between Shiraz wines from different Australian regions: the role of spectroscopy and chemometrics

This study reports the use of UV-visible (UV-vis), near-infrared (NIR), and midinfrared (MIR) spectroscopy combined with chemometrics to discriminate among Shiraz wines produced in five Australian regions. In total, 98 commercial Shiraz samples (vintage 2006) were analyzed using UV-vis, NIR, and MIR wavelength regions. Spectral data were interpreted using principal component analysis (PCA), linear discriminant analysis (LDA), and soft independent model of class analogy (SIMCA) to classify the wine samples according to region. The results indicated that wine samples from Western Australia and Coonawarra can be separated from the other wines based on their MIR spectra. Classification results based on MIR spectra also indicated that LDA achieved 73% overall correct classification, while SIMCA 95.3%. This study demonstrated that IR spectroscopy combined with chemometric methods can be a useful tool for wine region discrimination.     

Characterization of wines by nuclear magnetic resonance: a work study on wines from the Basilicata region in Italy

We explored the possibility of differentiating Italian wines produced in different regions by means of nuclear magnetic resonance (NMR) techniques. Ten commercial red Aglianico wines were selected from different areas of the Basilicata region in the south of Italy. Some important components of these wines were identified by the assignments of their (1)H and (13)C resonances using one- and two-dimensional homonuclear and heteronuclear NMR experiments. These data were compared with those obtained from 10 Aglianico wines produced in Campania, another southern Italian region. Differences were found among the wines according to their geographical origin and vintage. A fine discrimination of Aglianico wines from Basilicata and Campania was obtained, suggesting that the selected NMR parameters may be a valuable tool for wine authenticity control.     

Effect of accelerated autolysis of yeast on the composition and foaming properties of sparkling wines elaborated by a champenoise method

Five mutants (obtained by UV mutagenesis) and the parent strain were selected to produce sparkling wines following the traditional or champenoise method. The wines were aged with the yeast for 9 months, with samples being taken each month for analytical and sensory determinations. The wines elaborated with mutant strain IFI473I demonstrated an accelerated release of protein, amino acids, and polysaccharides. An analysis of the secreted polysaccharides revealed that mannose was the major sugar present. The effects of the products released by yeasts on the foaming properties of the wines were determined by both sensory and instrumental analysis. In all cases, the wines elaborated with mutant strain IFI473I showed improved foaming properties as compared to wines fermented without this strain. Similar results were obtained at a decreased aging time of 6 months, thereby confirming the capacity of IFI473I strain to carry out an accelerated autolysis. These results demonstrate that mutant strain IFI473I can significantly reduce production times of high-quality sparkling wines.     

Influence of oak wood on the aromatic composition and quality of wines with different tannin contents

The aromatic compounds associated with aging in wood have been studied in Monastrell wines containing different quantities of tannin. Analyses were carried out before and after a six month period in wooden barrels (225 L) of American and French (Allier) medium-toasted oak. Three classes of wine were made: one from a free-run must; one to which enological tannin was added; and one to which was added the wine obtained by pressing the grape pomaces. The aromas were determined by GC-MS, and the quality was evaluated by a group of expert tasters. The aromatic compounds, some of which came from the wines themselves and others which came from the wood, all increased in concentration by the end of the aging process. The ratio between cis- and trans-whiskylactone contents in wines reflected the different types of oak wood used. The note "vanilla" used by the tasters is probably not totally due to the presence of vanillin. The wines of best quality were those with a natural tannin content which had been aged in American oak, whereas the wines to which enological tannin had been added but aged in the same wood were considered the worst. An equalizing effect on the sensorial wines qualities was seen to result from the use of French oak. The furfural, eugenol, and cis-, and in some cases trans-, whiskylactone contents identified the wines from the different classes of wood. The wood from which the barrels were made had a greater effect on wines differentiation than the tannin content.     

Thermodynamics and structural features of the yeast Saccharomyces cerevisiae external invertase isoforms in guanidinium-chloride solutions

Recently, four external invertase isoforms (EINV1, EINV2, EINV3, and EINV4) have been isolated from S. cerevisiae. However, there is nothing known about their structural features and thermodynamics of unfolding. Since this information is essential for understanding their functioning at the molecular level as well as applicable in the food industry, we investigated guanidinium-chloride induced structural changes of the isoforms by CD and fluorescence spectroscopy. The resulting unfolding curves measured for each isoform at different temperatures were described simultaneously by a reversible two-state model to obtain the corresponding thermodynamic parameters. Here, we show that they are different for different isoforms and demonstrate that they correlate with the surface charge density of the native isoforms which follows the order EINV1 < EINV2 < EINV3 < EINV4. It appears that at physiological temperatures the thermodynamic stability of the isoforms follows the same order, while above 55 °C, the order is the opposite EINV1 > EINV2 > EINV3 ≈ EINV4. This suggests that increasing the efficiency of the food industry processes involving invertase would require the application of EINV3 and/or EINV4 at physiological temperatures and EINV1 at elevated temperatures.     

Influence of paclobutrazol on photosynthesis rate and dry matter partitioning in the apple tree

Four‐year‐old ‘Aki Fuji’ apple trees in their second leaf of fruiting were used to study the influence of paclobutrazol on photosynthesis rate (Pn) and the partitioning of dry matter in the different parts of the tree. It was found that the Pn of paclobutrazol‐treated trees was significantly higher than the untreated check trees. This is partially accounted for by the higher light intensity in the canopy of the paclobutrazol‐treated trees. Production efficiency of the paclobutrazol‐treated trees was 2.6 times higher than that of the untreated check trees. Paclobutrazol significantly changed the partitioning pattern of dry matter in the different parts of the tree. A much higher percentage of total dry matter was distributed to the fruit. However, a higher percentage of dry matter was found in the root of the paclobutrazol‐treated trees than in the untreated trees, the difference being mainly in the lateral and fibrous roots. Total dry matter accumulated per m² of occupied land of the paclobutrazol‐treated tree was 4% greater than that of the untreated check trees, whereas total dry matter accumulated per kg of leaves was essentially the same in both trees. Whether calculated on the basis of per m² of occupied land or per kg of leaves, the dry matter distributed into the fruit and into the root was considerably greater in the paclobutrazol‐treated trees than the untreated trees.     

Pyruvic acid and acetaldehyde production by different strains of Saccharomyces cerevisiae: relationship with Vitisin A and B formation in red wines

The production of pyruvate and acetaldehyde by 10 strains of Saccharomyces cerevisiae was monitored during the fermentation of Vitis vinifera L. variety Tempranillo grape must to determine how these compounds might influence the formation of the pyroanthocyanins vitisin A and B (malvidin-3-O-glucoside-pyruvate acid and malvidin-3-O-glucoside-4 vinyl, respectively). Pyruvate and acetaldehyde production patterns were determined for each strain. Pyruvate production reached a maximum on day four of fermentation, while acetaldehyde production was at its peak in the final stages. The correlation between pyruvate production and vitisin A formation was especially strong (R (2) = 0.80) on day 4, when the greatest quantity of pyruvate was found in the medium. The correlation between acetaldehyde production and the formation of vitisin B was strongest (R (2) = 0.81) at the end of fermentation when the acetaldehyde content of the medium was at its highest. Identification and quantification experiments were performed by HPLC-DAD. The identification of the vitisins was confirmed by LC/ESI-MS.     

Interactions between yeast lees and wine polyphenols during simulation of wine aging: I. Analysis of remnant polyphenolic compounds in the resulting wines

Wine aging on yeast lees is a traditional enological practice used during the manufacture of wines. This technique has increased in popularity in recent years for the aging of red wines. Although wine polyphenols interact with yeast lees to a limited extent, such interactions have a large effect on the reactivity toward oxygen of wine polyphenolic compounds and yeast lees. Various domains of the yeast cell wall are protected by wine polyphenols from the action of extracellular hydrolytic enzymatic activities. Polysaccharides released during autolysis are thought to exert a significant effect on the sensory qualities of wine. We studied the chemical composition of polyphenolic compounds remaining in solution or adsorbed on yeast lees after various contact times during the simulation of wine aging. The analysis of the remnant polyphenols in the wine indicated that wine polyphenols adsorption on yeast lees follows biphasic kinetics. An initial and rapid fixation is followed by a slow, constant, and saturating fixation that reaches its maximum after about 1 week. Only very few monomeric phenolic compounds remained adsorbed on yeast lees, and no preferential adsorption of low or high polymeric size tannins occurred. The remnant condensed tannins in the wine contained fewer epigallocatechin units than the initial tannins, indicating that polar condensed tannins were preferentially adsorbed on yeast lees. Conversely, the efficiency of anthocyanin adsorption on yeast lees was unrelated to its polarity.     

Effect of gluconic acid consumption during simulation of biological aging of sherry wines by a flor yeast strain on the final volatile compounds

Flor yeast Saccharomyces cerevisiae (capensis G1) strain assimilates gluconic acid during the aerobic biological aging process of sherry wines and exerts significant changes on the final volatile compounds of wines, especially a decrease in volatile acidity and butanoic, isobutanoic, 2-methylbutanoic, and 3-methylbutanoic acids. This decrease may have a favorable effect on the quality of sherry wines.     

Influence of winemaking practices on the concentration of rare earth elements in white wines studied by inductively coupled plasma mass spectrometry

Influence of clarification, filtration, and storage on the concentration of rare earth elements (REEs) was studied in white wines by inductively coupled plasma mass spectrometry (ICP-MS). Smooth and parallel chondrite-normalized (CN) plots were obtained for wines which have never been in contact with fining agents. Clarification and filtration generally used in white wine production were simulated in the laboratory using nontreated reference wines, and CN plots were compared before and after treatments. Clarification by bentonites yields an overall increase in REE concentrations resulting in substantially parallel CN curves well above the plots of the corresponding nontreated wines. Filtration using silicate (SiO2), on the other hand, changes the CN profile in a nonparallel manner due to a higher release of La, Ce, Pr, Nd, and Gd, more than other elements studied. Filtration with cellulose powder causes a small increase in the concentration of light REEs, while the concentrations of other elements remain basically unchanged. Storage conditions could also affect the REE pattern of wine. We found that the influence of glass is greater than that of stainless steel and wood. In addition, we report that commercially available finished white wines from the same region show highly different REE patterns depending on the winemaking practices employed.     

Influence of thermally processed carbohydrate/amino acid mixtures on the fermentation by Saccharomyces cerevisiae

The production of alcoholic beverages such as Tequila, Mezcal, whiskey, or beer includes the fermentation of a mash containing Maillard reaction products. Because excessive heating of the mash can lead to complications during the following fermentation step, the impact of Maillard products on the metabolism of Saccharomyces cerevisiae was investigated. For this purpose, fermentation was carried out in a model system in the presence and absence of Maillard reaction products and formation of ethanol served as a marker for the progression of fermentation. We found that increasing amounts of Maillard products reduced the formation of ethanol up to 80%. This effect was dependent on the pH value during the Maillard reaction, reaction time, as well as the carbohydrate and amino acid component used for the generation of Maillard reaction products. Another important factor is the pH value during fermentation: The inhibitory effect of Maillard products was not detectable at a pH of 4 and increased with higher pH-values. These findings might be of relevance for the production of above-mentioned beverages.     

Influence of storage conditions on the formation of some volatile compounds in white fortified wines (Vins doux naturels) during the aging process

Sweet fortified wines, traditionally aged under strong oxidation conditions, have a characteristic aroma. An experimental study investigated the aging of white sweet fortified wines under various conditions. The development 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. Aging in oak containers, variable storage temperatures, and variable modes of oxidation affect the formation of many of the volatile compounds responsible for the aging aroma of vins doux naturels (fortified wines). Furfural (1), 5-ethoxymethylfurfural (2), and sotolon (3) always reach concentrations above their perception thresholds in wood-aged wines, especially when new oak is used. The isomers of methyl-gamma-octalactone (4 and 5) are reliable indicators of aging in oak. Among the many identifiable volatile phenols, only the vanillin (7) content increases with aging, particularly if the container is made of wood and there is a high degree of oxidation. This molecule frequently reaches and even exceeds its perception threshold. We show here that vanillin and isomers of methyl-gamma-octalactone have a major impact on the aromas of fortified wines.     

Influence of some technological parameters on the formation of dimethyl sulfide, 2-mercaptoethanol,methionol, and dimethyl sulfone in port wines

Volatile sulfur compounds of 15 young port wines and 12 old port wines were determined. As there is a great difference in the pool of sulfur compounds between the two groups of wines, an experimental protocol was performed to determine which technological parameter (dissolved O(2), free SO(2) levels, pH, and time/temperature) was related with the formation/consumption of these compounds. Four sulfur compounds were selected for this purpose: dimethyl sulfide, 2-mercaptoethanol, dimethyl sulfone, and methionol. The synergistic effects of increasing temperature and O(2) at lower pH had the largest impact. Dimethyl sulfide was formed during the experimental period in the presence of O(2). Dimethyl sulfone had the same behavior. Methionol decreased significantly in the presence of O(2), but no methional was formed. 2-Mercaptoethanol, considered to be an important "off-flavor" in dry wines, also decreased during the experimental period (54 days) in the presence of O(2), and the respective disulfide was formed. These results corroborate the fact that old port wine (barrel aged) never develops "off-flavors" associated with the presence of methionol (cauliflower), 2-mercaptoethanol (rubber/burnt), or methional (cooked potato). In fact, temperature and oxygen are the major factors in the consumption of these molecules. However, some notes of "quince" and "metallic" can appear during port wine aging, and these can be associated with the presence of dimethyl sulfide.     

Influence of vine training and sunlight exposure on the 3-alkyl-2-methoxypyrazines content in musts and wines from the Vitis vinifera variety cabernet sauvignon

The influence of vine training and sunlight exposure on the 3-alkyl-2-methoxypyrazines contents in musts and wines was studied by means of two previously reported methods based on headspace solid-phase micro-extraction. Experimental samples were monitored throughout grape ripening and wine making. 3-Isobutyl-2-methoxypyrazine, 3-sec-butyl-2-methoxypyrazine and 3-isopropyl-2-methoxypyrazine were identified. The 3-isobutyl-2-methoxypyrazine content decreased throughout grape ripening in all of the sample types studied. After 1 day of maceration with the skins, there was an increase, but after racking, no further increase was observed. No significant differences between samples were found during grape ripening. Wines from goblet-trained vines, however, contained significantly less 3-isobutyl-2-methoxypyrazine. Clusters protected from sunlight since the beginning of the veraison resulted in wines with a significantly lower content of this compound than the control samples.