Wine Fractions Research Articles

Analysis of Aromatic Fraction of Sparkling Wine Manufactured by Second Fermentation and Aging in Bottles Using Different Types of Closures

Analysis of Aromatic Fraction of Sparkling Wine Manufactured by Second Fermentation and Aging in Bottles Using Different Types of Closures

Valorization of the solid fraction of wine lees through optimized accelerated autolysis: Effect of temperature, pH and solid concentration on free-amino acid concentration

Winemaking, as an agro-industrial process, generates substantial amounts of by-products, notably grape pomace and wine lees. The latter constitutes the residue left behind during the racking or bottling of wine, consisting mainly of dead yeast cells, ethanol, phenolic compounds, tartrates, and other compounds. Within the framework of by-products’ valorization, the rich content of dead yeast cells in wine lees render them conducive to the production of a yeast extract substitute through autolysis. In the present study, the effect of pretreatment, temperature, pH, and solid concentration on the efficiency of white wine lees autolysis was investigated. Moreover, the effect of enzyme addition and dynamic thermal protocols were investigated. Efficiency assessment was based on the increase of free α-amino nitrogen (FAN) found in the autolysate. The finding revealed a significant increase of FAN in all cases, with treated and untreated white wine lees reaching a maximum increase of 477% and 834%, respectively. Furthermore, the amino acid profile of autolysates was significantly affected by the autolysis temperature. These results hold promise for the comprehensive, holistic valorization of wine lees, suggesting their potential use as a nutrient source for microorganisms, such as wine yeast, or even as a grape must nitrogen modulator. Consequently, this by-product can be integrated back into the same industrial process from which it originates, namely winemaking. This not only aligns with the principles of circular economy but also underscores the potential for sustainable development within wineries.

Co-pigmentation of Pinotage anthocyanins with Cyclopia (honeybush) polyphenols in model wine solutions

Co-pigmentation of an anthocyanin-enriched fraction (AEF) of Pinotage wine with honeybush polyphenols (Cyclopia subternata extract and fractions enriched in specific polyphenols) was studied in model wine solutions. The hyperchromic effects and bathochromic shifts depended on the co-pigment sources and co-pigment/anthocyanin ratio. Fraction 2 (F2), enriched in xanthones (mangiferin and isomangiferin), produced the most pronounced co-pigmentation effect at a co-pigment/anthocyanin ratio of 15:1. Greater co-pigmentation effects were observed in model solutions at pH 3.0 (pH 3–4 evaluated) and in the absence of EtOH (0–16 % EtOH evaluated). During storage of solutions (AEF and/or F2) at 15 °C and 25 °C for 12 weeks, myrtillin, petunin, 3′,5′-di-β-D-glucopyranosyl-3-hydroxyphloretin and mangiferin concentrations decreased following first-order kinetics, while peonin and oenin degradation followed fractional-conversion kinetics. Polymeric anthocyanin formation followed zero-order kinetics. Reaction rates increased with an increase in storage temperature. The addition of F2 to the AEF solution produced a darker, more vivid colour and improved the colour stability, however, the yellow-orange colour of F2 and intensification of its colour during storage contributed to increasing red-orange hues. Further research is necessary to elucidate the effect of honeybush polyphenols on the colour and composition of a complete wine as it is more complex than model solutions.

Carbonic maceration vinification: A tool for wine alcohol reduction.

The increase in alcohol content in wine due to climate change is one of the main challenges that winemakers face today. Previous studies have indicated that carbonic maceration processing can be used to obtain a wine fraction with lower alcoholic strength. The aim of this study was to determine the effectiveness of this technique in obtaining wines with lower alcohol content. For this purpose, seven trials were carried out, studying a total of 63 wines. The physico-chemical, phenolic and aromatic composition of the wines was analysed using official methods and gas chromatography. The results showed that it is possible to obtain a fraction of carbonic maceration wine (25-35% of the total) with a reduction in alcohol content of up to almost 4% depending on the vinification conditions and the grape variety used. Therefore, this CM fraction, marketed on its own, could be a low-alcohol alternative to red wines.

Sensory dimensions derived from competitive and creative perceptual interactions between fruity ethyl esters and woody odorants in wine-like models

The present study analyses the sensory effects associated with the interactions between different woody aroma compositions and a simple fruity ester vector in red wines. The semi-synthetic wine models contained a fixed aroma composition, the dearomatised non-volatile fraction of red wine and 21 different combinations of ethyl 2-methylbutyrate (fruity vector) plus 1 out of 3 woody aroma compositions (woody vectors) at 3 possible levels of concentration each. Woody vectors imitated a highly toasted American oak (HAO—elevated levels of whiskylactones and furaneol), a highly toasted French oak (HFO—low levels of whiskylactone and vanillin levels, high levels of eugenol and guaiacol) and a medium toasted French oak (MFO—low levels of whiskylactones, eugenol, guaiacol and furaneol and high levels of vanilla). Models were sensorily assessed by a sorting task and by descriptive analysis. The increase in woody notes causes a concomitant decrease in fruity notes by a competitive perceptual interaction. HAO models are richest in coconut and woody notes and poorest in fruity notes, while HFO models keep strawberry and apple notes. At certain specific fruity-woody vector ratios, particularly in the MFO model, blackcurrant notes emerge, which can be considered a creative perceptual interaction.

Accurate quantitative determination of the total amounts of Strecker aldehydes contained in wine. Assessment of their presence in table wines

Strecker aldehydes (SAs) are key determinants of wine shelf-life and can be present in unoxidized wines in odorless forms, such as hydroxyalkylsulfonates, imines or acetals. A robust and accurate method for the determination of total forms of SAs, based on the classical derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and in the selective solid phase extraction of derivatives has been optimized and validated. Matrix effects have been solved by the use of adequate internal standards and by large-enough equilibration times under anoxic conditions. Method figures of merit are highly satisfactory in terms of detection limits (<0.1 μg/L), linearity (R2 > 0.997), reproducibility (5–13%) and recoveries (RSDs, between 2 and 10%, for 3-methylbutanal, 14%). The analysis of total SAs in 108 Spanish wines revealed that between 52% and 70% of unoxidized red wines and likely a similar fraction of white wines, contain levels of SAs high enough to cause oxidative aromas if bound forms of SAs cleave.

Comparison between Membrane and Thermal Dealcoholization Methods: Their Impact on the Chemical Parameters, Volatile Composition, and Sensory Characteristics of Wines.

Over the last few years, the dealcoholization of wine has piqued the interest of winemakers and researchers. Physical dealcoholization methods are increasingly used in the dealcoholization of wines because they can partially or completely reduce the alcohol content of wines. This study aimed to compare the chemical parameters, volatile composition and sensory quality of white, rosé and red wines dealcoholized by two physical dealcoholization methods: reverse osmosis (RO) and vacuum distillation (VD) at 0.7% v/v ethanol. RO and VD effectively reduced the ethanol concentration in all wines to the required 0.7% v/v, but also significantly affected most chemical parameters. The pH, free sulfur dioxide, total sulfur dioxide, and volatile acidity decreased significantly due to dealcoholization by RO and VD, while reducing sugars and total acidity increased significantly. VD resulted in higher color intensity, which was perceptible in dealcoholized rosé and red wines, while RO caused notable color differences in dealcoholized white and red wine fractions. RO were richer in esters (more ethyl esters and isoamyl acetate), higher alcohols, organic acids, terpenics and C13-norisoprenoids, and carbonyl compounds, while wines dealcoholized with VD had lower levels of these volatile compounds, which may reflect both the loss of esters into the distillate during evaporation and condensation (in the case of VD) and a shift in the chemical equilibrium responsible for ester formation and hydrolysis after ethanol removal. β-damascenone exhibited the highest OAV in all wines, however, losses equal to 35.54–61.98% in RO dealcoholized fractions and 93.62% to 97.39% in VD dealcoholized fractions were observed compared to the control wines. The predominant aroma series in the original and dealcoholized wines were fruity and floral but were greatly affected by VD. Sensory evaluation and PCA showed that dealcoholization by RO improved the fruity and floral notes (in rosé and red wines), color intensity, sweetness, viscosity, and aroma intensity better than dealcoholization by VD, while VD mainly enhanced the color of the dealcoholized wines. Both methods increased the acidity of the respective dealcoholized wines. Nevertheless, RO dealcoholized wines achieved higher acceptance by the panelists than VD dealcoholized wines. Therefore, RO may be a better method for producing dealcoholized (0.7% v/v) wines with minimal impact on aroma and sensory quality.

Effect of Structural Transformations on Precipitability and Polarity of Red Wine Phenolic Polymers

Condensed tannins and polymeric pigments are essential red wine components that contribute to color stability, taste, and mouthfeel. Phenolic polymers in red wine consist of flavan-3-ol monomers and anthocyanins and cause the perception of astringency. Due to the chemical heterogeneity of proanthocyanidin polymers, analytical tools to determine the polymers’ structural features are limited. Incorporation of anthocyanins increases the structural complexity even more and makes it almost impossible to assess the influence of structure on the perceived astringency. To better understand the structural diversity of red wine polymers, this study combines forced aging and FLASH-fractionation of polyphenolic wine extracts to reveal the relationship between phenolic polymers and two physicochemical properties: polarity and hydrophilicity. Red wine fractions were characterized using polarity, the octanol-water partitioning coefficient, protein precipitation assay, ultra high-performance liquid chromatography-mass spectrometry, and color. Tannin concentrations in wine decreased during forced aging and were constant in the corresponding extracts, suggesting alteration of the precipitation behavior. A simultaneous increase in precipitable polymeric pigments leads to the assumption that incorporating anthocyanins into tannin molecules alters their interactions with red wine polysaccharides and proteins, lowering tannin readings. Finding tannins and polymeric pigments in different FLASH-fractions indicates that precipitability of polymers is affected by their physicochemical properties, which in turn depend on the degree of polymerization as well as degree of pigmentation. The results of this study show that red wine astringency and its sub-qualities may be related to the increase in precipitable polymeric pigments during forced red wine aging and their putative enhanced interaction with wine polysaccharides, increasing understanding of astringency mechanisms.

Identifying a Role of Red and White Wine Extracts in Counteracting Skin Aging: Effects of Antioxidants on Fibroblast Behavior.

Dermal fibroblasts are the main actor in many proteins’ secretion, including collagen, preserving skin function. Free radicals are involved in skin aging and damages involving different cellular components. The imbalance between reactive oxygen species (ROS) amount and natural antioxidant enzymes negatively affects skin homeostasis. Natural compounds have recently emerged as a potential anti-aging tool in tissue regeneration. In the present paper we evaluated the antioxidant activity of white and red wines, considering their probable use, as raw materials, for the formulation of cosmetic products with anti-aging properties. We studied a method that would allow the removal of the alcoholic fraction of wines and determined their composition by LC-MS analysis. We then tested the possible cytotoxic effects of red and white wines on fibroblasts by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay, and their antioxidant activity by the catalase activity test in stressing conditions. Finally, we evaluated their anti-aging potential through the β-galactosidase colorimetric assay. Our results showed that wine extracts exhibit a remarkable antioxidant and anti-aging activity, especially on cells exposed to a marked stressful event. These properties could suggest their possible application as cosmetical products for skin regeneration.

Identification of compounds in red wine that effectively upregulate aquaporin-3 as a potential mechanism of enhancement of skin moisturizing

In a previous clinical study, the moisture content in the stratum corneum of healthy Japanese women who consumed a beverage rich in oligomeric proanthocyanidins (OPCs) made from red wine extract was found to be higher than that in the control group. This finding suggested that OPCs can increase skin moisture content. In this study, we determined the expression level of aquaporin-3 (AQP3) in keratinocytes to elucidate the mechanism by which compounds in red wine grape increase moisture content in stratum corneum. Through in vitro studies, we confirmed that normal human epidermal keratinocytes (NHEK) incubated with red wine induced AQP3 expression. Furthermore, the supplementation of red wine fractions enriched in OPC was shown to increase AQP3 expression. Besides, the component of OPC-rich fractions that upregulated AQP3 expression was found to be a gallic acid (GA)-binding flavan-3-ol, particularly oligomeric compounds. We found that GA-binding OPC were able to upregulate AQP3 expression and that these compounds were enriched in red wine. Our findings might suggest that the mechanism of enhancement of moisture content in stratum corneum by red wine might be via the upregulation of AQP3 expression in the epidermal keratinocytes.

Evolution of the Phenolic Fraction and Aromatic Profile of Red Wines Aged in Oak Barrels.

Various changes occur in red wine during aging in oak barrels. Among these, the variation of the polyphenolic fraction and the transfer of aromatic compounds to the wine from oak wood are of great importance. The aim of the present work is to compare the chemical composition of wines aged in different new oak barrels with similar commercial denominations. During 8 months, the total polyphenol index (TPI), color parameters, anthocyanins and pyranoanthocyanins, and wood aromatic compounds were periodically evaluated. The measurement of the TPI and color parameters was similar in all wines, but significant differences were found in total anthocyanin and vitisin content and in certain aromatic compounds belonging to volatile phenols, furanic compounds, and phenolic aldehydes. The results obtained indicate the need for the winemaker to carry out preliminary tests in order to be able to choose the wood that best suits the sensorial profile of the wine.

Influence of fungicide residues and in vitro gastrointestinal digestion on total antioxidant capacity and phenolic fraction of Graciano and Tempranillo red wines

The effect of fenhexamid, mepanipyrim and cyazofamid fungicides on in vitro bioavailability of antioxidant activity and phenolic compounds of Tempranillo and Graciano red wine was studied by simulating the digestive process by dialysis in semipermeable membranes. Determination of antioxidant activity was through reaction with the DPPH • radical and the measurement of phenolic compounds was made with liquid chromatography with diode detector (HPLC-DAD). Fenhexamid, mepanipyrim and cyazofamid reduce the total polyphenol content in both wines. During dialysis there was a large loss of total polyphenols (80–90%) and of antioxidant activity (> 90%). The bioavailability of the phenolic compounds is lower than that for non-treated wines and the highest dialization percentages were found for stilbenes > 50%. While for the remaining phenolic fraction the order is the following hydroxycinnamic derivatives > anthocyanins > flavonols.

Modification of the polyphenolic and aromatic fractions of red wines aged on lees assisted with ultrasound

SummaryThe ageing on lees is a technique particularly interesting in the production of red wines due to the possibility of enhancing some of their sensory characteristics. Different authors have researched the ultrasound assistance to accelerate this ageing process in wines. The present work evaluated the modification that both fractions, polyphenolic and aromatic, of red wines suffer during the ageing on lees process assisted with ultrasounds and with the addition of oak chips. The results obtained during the experimental design indicate that the ultrasound treatment decreased the concentration of proanthocyanidins (between 20.3% and 32.8% with and without oak chips, respectively) and the total pigment content (with the highest reduction in the control sonicated wine 55.9% without chips and lees and from 47.8% to 48.9% when having oak chips/lees and lees, respectively). In addition, it has been observed that the ultrasound treatment did not affect the amount of fermentative volatile compounds present in the wine but, it increased the concentration of phenolic aldehydes coming from oak wood chips (10.8% in control wine and from 35.92% with oak chips/lees to 55.8% with lees).

Mass-spectrometric study on13C/12C carbon and18O/16O oxygen stable isotopes distributions in grapes and wines from the Black Sea regions

The present study continues the 2015–2016 research project on biological characteristics of stable isotopes fractionation in grapes taking into account the agro-climatic growth conditions of this representative of the C3-pathway of photosynthesis group of plants in different geographical Black Sea regions. The first parts of the project were presented at the 39th and 40th Congresses of OIV in Bento Gonçalves (Brazil) and Sofia (Bulgaria). The scientific data on compositions of13C/12C carbon and18O/16O oxygen stable isotopes in carbohydrates, organic acids, and intracellular water were obtained for grapes of 2015–2016 growing seasons in the four areas of the Crimean peninsula as well as in several areas of the Don Basin and the Western Caspian region. This report presents the results of the 2017 season study of13C/12C carbon and18O/16O oxygen stable isotopes in carbohydrates and intracellular water of 12 red and white grape varieties (Aligote, Rkatsiteli, Sauvignon Zeleny, Chardonnay, Cabernet Sauvignon, Sauvignon Blanc, Merlot, Risling, Pinot Noir, Cabernet Franc, Sira, Krasnostop) as well as in ethanol of wines made from corresponding grapes from the Crimean Peninsula and South-West Coast of the Greater Caucasus. To measure the ratio of carbon isotopes13C/12C in grape (must) carbohydrates and wine ethanol the Flash-Combustion technique (FC-IRMS/SIRA) has been used, while the method of isotopic equilibration (EQ-IRMS/SIRA) has been used for the measurement of18O/16O oxygen isotopes ratio in the intracellular water of grapes (must) and in the water fraction of wine. The GC-Combustion technique (GC-IRMS/SIRA) has been used for the first time to measure the carbon isotopes13C/12C distribution in ethanol of studied wines. It has been found that the δ13CVPDBvalues for carbohydrates of red and white grape varieties as a result of biological fractionation of carbon isotopes in the agro-climatic conditions of plant growth (2017 season) for the studied geographical areas formed the following quantitative ranges: from − 26.72 to − 23.35‰ (the Crimean Peninsula) and from − 25.92 to − 23.87‰ (South-West Coast of the Greater Caucasus). The δ13CVPDBvalues for wine ethanol are in the following ranges: from − 28.15 to − 24.47‰ (the Crimean Peninsula) and from − 27.29 to − 25.78‰ (South-West Coast of the Greater Caucasus). The δ18OVSMOWvalues in intracellular water of grapes of the 2017 season range from − 1.24 to 2.17‰ (the Crimean Peninsula) and from 1.08 to 4.09‰ (South-West Coast of the Greater Caucasus). The results of this study show, in comparison with the results of studies of the 2015 and 2016 seasons, a decrease in the δ13CVPDBvalues for carbohydrates of grapes and ethanol of wine, which is explained by the changed climatic conditions of grapes growing in the vegetation period of 2017.

Effect of the extent of ethanol removal on the volatile compounds of a Chardonnay wine dealcoholized by vacuum distillation

“Beverages obtained from the partial dealcoholization of wine” are those drinks whose final alcoholic degree after dealcoholization is lower than that of a wine and higher than or equal to 0.5% v/v. When the total alcoholic degree is lower than 0.5% v/v the denomination is “Beverages obtained from the dealcoholization of wine”. The practices to be authorized for the production of these drinks with the dealcoholized wine fractions are currently being studied at OIV. The characterization of the composition of these fractions is essential to identify the necessary corrective practices. The present work was aimed at monitoring the losses of the main volatile compounds of a Chardonnay wine with the proceeding of the dealcoholization process by vacuum distillation. The wine was subjected to total dealcoholization, and during the process the evaporated fractions, re-condensed at 9 ∘C, were collected in aliquots of 1.25 L each. The ethanol content of each fraction was measured, and for the first 20 fractions the content in volatile compounds was determined with GC-MS. The results show that the losses of volatile compounds during the dealcoholization process follow different trends depending on the molecules considered. The most volatile compounds, generally with the lowest perception thresholds, were mainly present in the first evaporated fractions. The greatest losses concerned isoamylacetate, ethyl hexanoate and ethyl octanoate. Conversely, a greater number of molecules were present at similar concentrations in the different fractions, and their losses followed a linear or sometimes exponential trend: in particular, these compounds included n-hexanol, 2-phenylethanol, diethyl succinate and medium chain fatty acids (hexanoic, octanoic and decanoic acids). In the wine dealcoholized at 3.36% v/v (loss of ethanol equal to 7.43% v/v, corresponding to the 20th and last recondensed fraction), some volatile compounds were no longer detectable or quantifiable; in particular, these compounds were isoamylacetate, ethylhexanoate, hexylacetate, n-hexanol and other alcohols with 6 carbon atoms and ethyl octanoate. Other compounds, such as hexanoic, octanoic and decanoic acids, and, in particolar, β-phenylethanol, benzylic aalcohol and γ-butyrolactone, underwent lower percentage losses than those of ethanol. The dealcoholization process can therefore deeply modify the original aromatic profile of the wines, intervening on the absolute concentration and on the relative ratios of the single molecules.

Straw Wine Melanoidins as Potential Multifunctional Agents: Insight into Antioxidant, Antibacterial, and Angiotensin-I-Converting Enzyme Inhibition Effects.

Numerous studies provide robust evidence for a protective effect of red wine against many diseases. This bioactivity has been mainly associated with phenolic fractions of wines. However, the health effects of melanoidins in red sweet wines has been ignored. The goal of the present work was to unravel the antioxidant, antimicrobial, and angiotensin-I-converting enzyme (ACE) inhibitory properties of straw sweet wine melanoidins. Results demonstrated that melanoidins have a potential antioxidant activity, determined by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and Ferric reducing antioxidant power (FRAP) assays. The antimicrobial activity of melanoidins was also tested against Listeria monocytogenes, Salmonella Enteritidis, and Escherichia coli. Minimum inhibitory concentration (MIC) of isolated melanoidins against three bacterial strains ranged from 5 mg mL−1 to 10 mg mL−1. Finally, the ACE inhibitory effect of isolated melanoidins was evaluated, as it is linked with antihypertensive activity. Results showed that they have ACE-inhibitory activity ranging from 58.2 ± 5.4% to 75.3 ± 6.4% at a concentration level of 2 mg mL−1. Furthermore, the chemical properties of isolated melanoidins were determined. Results demonstrated that the skeleton of straw wine melanoidins is mainly composed of carbohydrates, and bear significant numbers of phenolic compounds that may play critical roles in their functional properties. Overall, this study describing the chemical composition and functional properties of melanoidin fractions isolated from a straw wine highlights that they can be exploited as functional agents for multiple purposes. Finally, melanoidins are an unexplored source of bioactive molecules in straw wines except from polyphenols that contribute to the health effects.

Influence of Acetaldehyde Induction on Monomeric and Polymeric Polyphenols in Wine using the Polyphenol/Protein-binding Model

Polyphenols make a substantial contribution to the sensory properties of wine, and their evolution is affected by the acetaldehyde present during fermentation and ageing. In this work, five typical monomeric phenolic standards and three different polymeric flavanol fractions separated from wine were tested for polyphenol/protein binding by means of circular dichroism measurement and fluorescence spectrum assay in the presence or absence of acetaldehyde, and the formation of new oligomeric compounds linked by ethyl bridges was observed through HPLC-MS analyses. The results show that the protein-binding ability of these monomers was in the order of gallic acid > caffeic acid > quercetin > (+)-catechin > (-)-epicatechin, while acetaldehyde exerted a stronger effect on (+)-catechin and (-)-epicatechin monomers. Moreover, different wine fractions had different responses when reacted with proteins with the participation of acetaldehyde, while the polymeric proanthocyanidins produced the largest value (84.67%) of the salivary protein precipitation index and the strongest fluorescence-quenching effect.

Antioxidant and Antihypertensive Effects of a Chemically Defined Fraction of Syrah Red Wine on Spontaneously Hypertensive Rats.

A particularly phenolic-rich fraction extracted from red wine from the São Francisco valley (Northeastern Brazil) was chemically characterized and its hypotensive and antioxidant effects on spontaneously hypertensive rats were studied both in vitro and in vivo. The liquid-liquid pH dependent fractionation scheme afforded a fraction with high content of bioactive phenolics such as flavonols, flavonol glycosides, phenolic acids and anthocyanins, whose identities were confirmed by liquid chromatography coupled to mass spectrometry analysis. Pretreatment of spontaneously hypertensive rats with this wine fraction at doses of 50 and 100 mg/kg by gavage for 15 days was able to decrease mean arterial pressure and heart rate as well as decrease serum lipid peroxidation. The fraction at concentrations of 0.01–1000 µg/mL induced concentration-dependent relaxation of isolated rat superior mesenteric artery rings pre-contracted with phenylephrine and this effect was not attenuated by endothelium removal. Our results demonstrate it is possible for phenolic constituents of red wine that are orally bioavailable to exert in vivo hypotensive and antioxidant effects on intact endothelial function.

Is wine savory? Umami taste in wine

Umami is an important taste element in natural products like wine. The umami taste has distinctive properties that differentiate it from other tastes, including a taste-enhancing synergism between two umami compounds, L-glutamate and 5’-ribonulceotides, and a prolonged aftertaste. In human taste cells, taste buds transduce the chemicals that elicit the umami tastes into membrane depolarization, which triggers release of transmitter to activate gustatory afferent nerve fibers. Umami taste stimuli are primarily received by type II receptor cells which contain the T1R and T2R families of G protein-coupled taste receptors. The taste sensation of umami requires protein hydrolysis which renders free glutamic acid. The main components of the nitrogen fraction of musts and wines are amino acids, peptides, proteins and ammonium ion. Their presence in wine is from amino acids of grapes, enzymatic degradation of grape proteins, excretion by living yeasts at the end of fermentation and to proteolysis during yeast autolysis. Thus, amino acids are important contributors of the wine savory taste and flavor.

Rapid fingerprinting of white wine oxidizable fraction and classification of white wines using disposable screen printed sensors and derivative voltammetry

This work describes the application of disposable screen printed carbon paste sensors for the analysis of the main white wine oxidizable compounds as well as for the rapid fingerprinting and classification of white wines from different grape varieties. The response of individual white wine antioxidants such as flavanols, flavanol derivatives, phenolic acids, SO2 and ascorbic acid was first assessed in model wine. Analysis of commercial white wines gave voltammograms featuring two unresolved anodic waves corresponding to the oxidation of different compounds, mostly phenolic antioxidants. Calculation of the first order derivative of measured current vs. applied potential allowed resolving these two waves, highlighting the occurrence of several electrode processes corresponding to the oxidation of individual wine components. Through the application of Principal Component Analysis (PCA), derivative voltammograms were used to discriminate among wines of different varieties.