Influence of some technological practices on the quantity of resveratrol in wine

 A study of the effects of some prefermentative and fining practices on the resveratrol concentration in wine was carried out. The trans- and cis-resveratrol contents in a red wine obtained using must hyperoxidation were reduced to about 50% compared with those of control wines; this decrease was greater than that observed for total phenols and catechins. In contrast, sparging the red grapes with SO₂ and ascorbic acid before crushing them resulted in the trans-resveratrol concentration being greater than that of the control wines. Moreover the amounts of trans- and cis-resveratrol in commercial and synthetic wines were determined before and after addition of charcol, polyvinylpolypyrrolidone (PVPP), bentonite, casein, gelatine, and two inert materials, cellulose and diatomaceous earth (kieselgur), used as a filter aid. The results showed that PVPP, charcoal and casein were more effective at removing trans- and cis-resveratrol both in synthetic wine and in commercial wines. In all the wines tested the other fining agents gave a limited decrease (2 – 5%) of trans- and cis-resveratrol. After charcoal and PVPP treatments, significant correlations were observed between the percentage of residual resveratrol and the total phenols in the wines. Received: 16 June 1997     

Preliminary study of resveratrol content in Aragón red and rosé wines

A survey of resveratrol content in wines of the four Aragón designations of origin (Borja, Cariñena, Calatayud and Somontano) was carried out. Concentrations of trans- and cis-resveratrol isomers of 98 commercial wines of the four designations of origin, from several vintages, were analyzed by means of reverse-phase high-performance liquid chromatography. Concentration of trans-resveratrol ranged from 0.32 to 4.44 mg/l in red wines and from 0.12 to 2.80 mg/l in rosé wines. cis-Resveratrol levels ranged from 0.20 to 5.84 mg/l in red wines and from 0.02 to 3.17 mg/l in rosé wines. The grape variety influenced resveratrol contents in wines from the different regions. The highest trans/cis ratios were found in Somontano (4.50) and Calatayud wines (2.90), both of the Tempranillo variety. However, a discriminant analysis applied to the concentrations did not show significant differences between young red wines nor between rosé wines of the four designations of origin.     

A review of the content of the putative chemopreventive phytoalexin resveratrol in red wine

Resveratrol, a naturally occurring compound of various fruits such as grapes, is thought to possess chemopreventive properties. The levels of resveratrol in grapes and grape products including wine, varies from region to region and from one year to another. This paper reviews the resveratrol content in red wine based on relevant published data. Red wine contains an average of 1.9 ± 1.7 mg trans-resveratrol/l (8.2 ± 7.5 μM), ranging from non-detectable levels to 14.3 mg/l (62.7 μM) trans-resveratrol. In general, wines made from grapes of the Pinot Noir and St. Laurent varieties showed the highest level of trans-resveratrol. No region can be said to produce wines with significantly higher level of trans-resveratrol than all other regions. Levels of cis-resveratrol follow the same trend as trans-resveratrol. The average level of trans-resveratrol-glucoside (trans-piceid) in a red wine may be as much as 29.2 mg/l (128.1 μM), i.e., three times that of trans-resveratrol.     

Comparison of polyphenols and aroma in red wines from Portuguese mainland versus Azores Islands

trans-Resveratrol (trans-3,5,4′.trihydroxystilbene), piceid (resveratrol 3-O-β-D-glucopyranoside), together with their isomers and quercetin were measured in red wines from cultivars grown in Portuguese mainland and Azores Islands. Crude hydroxystilbenes and quercetin were extracted by solid-phase extraction-C₁₈ cartridges, and eluted with ethyl acetate. Recoveries of added trans-resveratrol and quercetin were between 90.2 to 101% (mean 96.8%) and between 95.2 and 97.6% (mean 96.2%), respectively. The precision measured by coefficients of variation (overall mean) ranged from 1.8 to 3.3%, and the calibration curves were linear with the mean correlation coefficients of 0.9997 and 0.9978 for trans-resveratrol and quercetin, respectively. The wine polyphenolic compounds were separated by reverse-phase C18 HPLC column and identified by UV fast scanning, retention times and HPLC/MS. The average content of total stilbenes was 4.75 and 6.33 mg/l, that of quercetin was 4.38 and 5.57 mg/l, and the trans/cis ratio was 8.32 and 10.89 for piceid and 5.2 and 4.09 for resveratrol in Portuguese mainland and Azorean wines, respectively. The Azorean wine (Basalto) was notable in having the highest trans-resveratrol concentration. The aroma profile of red wine samples from different regions were compared using SPME/GC-MS headspace methodology.     

Nutraceutical value and toxicological profile of selected red wines from Morocco

The polyphenolic composition, antioxidant properties and multielement profile of selected red wines from Morocco were evaluated. The polyphenolic contents resulted higher than those reported elsewhere for the same variety of wines; the highest quantity was found in Cabernet Sauvignon, followed by Merlot, and last by Syrah wine. All of the wines tested showed very similar anthocyanin and flavonol patterns: individual compound contents resulted generally higher in comparison to conventional wines. The content of trans-resveratrol was significantly higher than that of cis-resveratrol in all of the wine samples. Particularly, Merlot showed the highest concentration of trans-resveratrol while Syrah exhibited the highest levels of cis-resveratrol. Reducing capacity resulted higher than antiradical property for all of the wines. The metal concentrations were below the official limits. The elemental pattern of wines were very similar, excepted V, Mn, Fe, Cu, As and Mo, for which Syrah markedly differed from the other wine samples.     

Matrix effects on the bioavailability of resveratrol in humans

The pharmacokinetics of resveratrol in 11 healthy male volunteers has been assessed in a randomized, crossover, controlled clinical trial after the administration of three grape products: red wine (250 mL), grape juice (1/L), or tablets (red wine extracts enriched with trans-resveratrol). Doses of trans-resveratrol independently of the product administered, were about 14 μg/kg. Biological samples were collected and analysed by capillary gas chromatography–mass spectrometry. cis-Resveratrol, trans-resveratrol and dihydroresveratrol were determined in plasma and urine. Plasma concentration of trans-resveratrol after hydrolysis increased as a response to all grape products and that of cis-resveratrol after wine and grape juice. Free forms of these phenolic compounds were deemed undetectable in plasma. Despite similar trans-resveratrol doses being administered, its bioavailability from wine and grape juice was 6-fold higher, than that from tablets. Resveratrol was better absorbed from natural grape products than from tablets, pointing out the importance of the matrix in its bioavailability.     

Rapid method for resveratrol determination by HPLC with electrochemical and UV detections in wines

The study describes an improved version of the reverse-phase-HPLC method. To determine free resveratrol isomers, the method uses isocratic elution and electrochemical detection with the use of a glassy working electrode at a potential of 0.75 V. The effects of important factors – such as the isomerization of standard resveratrol solution in diffused daylight and its dependence on temperature or resveratrol isomerization in wine samples – were investigated. The equilibrium between trans- and cis-isomer was achieved after a 5-h exposure to the daily diffused light and it was not significantly influenced by the temperature (30–60 °C). Linearity was obtained in the concentration range from 0.01 to 10 mg l⁻¹. The detection limit (S/N=3) was 3 μg l⁻¹ for trans-resveratrol and 15 μg l⁻¹ for cis-resveratrol. The trans- and cis-resveratrol were determined in selected Czech red and white wines and in the extract from Vitis vinifera plant. The concentration of trans-resveratrol ranged from 0.7 to 11 mg l⁻¹, that of cis-resveratrol from 0.6 to 5.1 mg l⁻¹.     

Authentication of Italian red wines on the basis of the polyphenols and biogenic amines

Seventy-three Southern Italian red wines were characterized according to their content in total polyphenols, trans- and cis-resveratrol and biogenic amines. These quality parameters were used in multivariate statistical analysis to discriminate the wines according to their specific geographical origin. The results indicated that total polyphenols, resveratrol isomers and biogenic amines provide a good prospect for discriminating wines by regions. The discrimination was also possible to a lesser extent by cultivar. In particular, canonical variate analysis suggested that the discrimination of wines according to their provenance is based on the following parameters: cis-resveratrol, total polyphenols, spermidine and tryptamine for Basilicata region; agmatine and trans-resveratrol for Calabria and Campania regions; cadaverine, ethanolamine, histamine, putrescine and tyramine for Puglia region.     

Evaluating potential alternatives to potassium caseinate for white wine fining: Effects on physicochemical and sensory characteristics

The use of potassium caseinate for wine fining can cause allergic reactions and must be included on wine bottle labels. The focus of this research was to determine if non-allergenic pea protein or polyvinylpolypyrrolidone (PVPP) are possible alternatives for wine fining. Trials were performed to compare the effects of these potential fining agents on phenolic compounds, browning potential, turbidity and sensory attributes. The results indicate that flavonoid and non-flavonoid phenols decreased (p < 0.05) in the wines treated with potassium caseinate, pea protein, and PVPP. All fining agents decreased (p < 0.05) wine colour. Potassium caseinate was the most effective fining agent for reducing browning potential. Pea protein and potassium caseinate resulted in increased clarity of the final wines. No sensorial differences (p < 0.05) were detected among the wines prepared with the different fining agents. This study provides information that could be used to select an appropriate alternative to potassium caseinate.     

Detection of ochratoxin A and cis- and trans-resveratrol in red wines and their musts from Calabria (Italy)

The natural occurrence of ochratoxin A (OTA) and cis- and trans-resveratrols in red wines has been widely reported. The aim of this work was to evaluate the ochratoxin A (OTA) and both cis- and trans-resveratrol content of red wine (from must to wine) in a pilot-scale vinification process in Calabria (Italy). Eleven samples were collected at different stages of vinification and analysis was carried out by HPLC. Wine from manufacturer 3 contained the highest amount of trans-resveratrol (3.41?mg?l^?1). This wine was characterized by an Aglianico–Magliocco grape variety. Interestingly, data regarding OTA showed that the value of this contaminant was low in all analyzed samples and, in each case, below the legal limit (2.0?mg?l^?1 (ppb)). Overall, the results demonstrated the high quality of wines produced in Calabria.     

Changes in phenolic compounds and colour in pale Sherry wines subjected to fining treatments

 Changes in the concentrations of hydroxybenzoic acids, hydroxycinnamic acids and their esters, monomeric and dimeric derivatives of flavan-3-ol, and flavonols, as well as in the UV-visible absorbances of pale Sherry wines were studied. The wines were subjected to four different fining treatments: casein + bentonite, casein + bentonite + activated charcoal, casein + bentonite + polyvinylpyrrolidone (PVPP) and casein + bentonite + Riduxhigh. Based on the results, the treatments including activated charcoal and PVPP were the most effective at decreasing the overall concentration phenolic compounds, with no significant difference between them. Likewise, these treatments provided the best results in relation to wine colour in the visible spectral region, and particularly at 420 nm, at which wavelength browning compounds are usually measured. Received: 24 March 1997 / Revised version: 11 June 1997     

Capillary electrophoresis analysis of trans- and cis-resveratrol,quercetin, catechin and gallic acid in wine

A study was conducted on the use of micellar electrokinetic capillary chromatography (MEKC) in the analysis of trans- and cis-resveratrol, quercetin catechin and gallic acid in wine. Standards and wine samples were directly injected into CE after a simple filtration, under a pressure of 50 mbar. Separation of the compounds was done in bare fused-silica capillary-extended light path with 50 μm i.d. An excellent correlation coefficient (r = 0.99998) was obtained with a linear analytical response from 8 to 1000 ppm of resveratrol, quercetin, catechin and gallic acid in MEKC. The high separation efficiency obtained recommend CE as a good application for trans- and cis-resveratrol detection in wine.     

Changes in phenolic compounds and colour in pale Sherry wines subjected to fining treatments

 Changes in the concentrations of hydroxybenzoic acids, hydroxycinnamic acids and their esters, monomeric and dimeric derivatives of flavan-3-ol, and flavonols, as well as in the UV-visible absorbances of pale Sherry wines were studied. The wines were subjected to four different fining treatments: casein + bentonite, casein + bentonite + activated charcoal, casein + bentonite + polyvinylpyrrolidone (PVPP) and casein + bentonite + Riduxhigh. Based on the results, the treatments including activated charcoal and PVPP were the most effective at decreasing the overall concentration phenolic compounds, with no significant difference between them. Likewise, these treatments provided the best results in relation to wine colour in the visible spectral region, and particularly at 420 nm, at which wavelength browning compounds are usually measured. Received: 24 March 1997 / Revised version: 11 June 1997     

Determination of flavan-3-ols and trans-resveratrol in grapes and wine using HPLC with fluorescence detection

Concentrations of trans-resveratrol, catechin and epicatechin were analyzed in musts and wines produced from seven red and four white grape cultivars from various wine growing regions of Turkey. Phenolics were quantified using an HPLC method optimized for the separation of wine phenolics. Wine samples contained higher phenolics levels than the corresponding musts. With the exception of Semillion, white wines and musts contained lower concentrations of phenolics than red wines and musts. However, the white cultivar Semillion had the highest concentrations of catechin and epicatechin among all wine and must samples. Semillion wine catechin and epicatechin were 13.7 and 11.8 mg/L, respectively. The highest level of trans-resveratrol among the white cultivars was found in Narince wine (1.93 mg/L). Within the red wine and must cultivars, Bo?azkere, Öküzgozü, and Cabernet contained the highest concentrations of flavan-3-ols and trans-resveratrol. Catechin was the major phenolic in all wines and most musts. Epicatechin was the major phenolic in 6 of the 11 must samples, but none of the wine samples. trans-Resveratrol was generally found in lowest concentrations in both wines and musts.     

Nutraceutical properties and polyphenolic profile of berry skin and wine of Vitis vinifera L. (cv. Aglianico)

Red grapes are rich in phenolics, flavonoids, anthocyanins and resveratrol, all substances which have been suggested as having nutraceutical and health benefits. The berry skin and wine of grape cultivar Vitis vinifera L. (cv. Aglianico), grown in Basilicata (Southern Italy) were examined to determinate the presence of the above mentioned compounds as well as to establish the inorganic cation profile. HPLC analysis coupled with LC–ESI/MS/MS detected high contents of total flavonols and anthocyanins in berry skin and wine. The wine made with the same grape used for berry skin assays showed a notable presence of quercetin-3-O-glucoside (39.4% of total flavonols), and malvidin and petunidin derivatives (63.9% and 10.8% of total anthocyanins, respectively). The strong antioxidant ROS-scavenging activity, determined by both DPPH and FRAP assays, and the high resveratrol content confer high sensory characteristics resulted to be associated with positive nutraceutical properties of these grapes and wine. The level of cis-resveratrol was lower than trans-resveratrol in both berry skin and wine reaching 44.1 mg/kg and 0.3 mg/l, respectively. The cation profile presents low levels of Ca, Cu, K, Fe, Zn and Cd compared to numerous, important red wines, such as Monastrell and Tempranillo.     

Effects of fining agents on trans-resveratrol concentration in wine

Resveratrol has been identified as a wine component related to moderate wine consumption and a reduction in serum cholesterol levels. Processes such as wine fining that result in loss of resveratrol during winemaking are therefore of interest, and led to these present studies. A number of agents were compared and were found to lower resveratrol levels in all wines to some extent. Results from two studies (1996 and 1997) are reported. The standard addition method was used in combination with High Pressure Liquid Chromatography to calculate resveratrol levels. In Study 1 (1996), recommended maximum levels of all fining agents (Level 3), bentonite, egg white, gelatin + kieselsol and polyvinylpolypyrrolidone (PVPP), lowered resveratrol levels significantly compared to controls (Level 0). Nevertheless, addition of fining agents at Level 0 resulted in resveratrol levels that were significantly higher than those at Level 3, but resveratrol levels in wine from Level 0 were not significantly different from Level 1. In Study 2 (1997), carbon + egg white, and gelatin + kieselsol fining was studied, and their effects differed according to grape variety. Least removal of resveratrol by carbon fining occurred in wine from Cabernet Sauvignon (Vitis vinifera) whereas most removal occurred in wines from Cynthiana (Vitis aestivalis) and Noble (Vitis rotundifolia). Resveratrol levels of control wine were significantly higher than resveratrol levels of wine treated with recommended maximum addition of fining agent in all varieties. Taken overall, any addition of any fining agent lowered resveratrol levels in all wines to some extent, but complex interactions between fining agent and wine variety resulted in different regression trends. While recognising the constraints set by our particular data that could reflect unique circumstances, we are nevertheless able to infer from these trends that low levels of fining agents can be used without statistically significant loss of resveratrol.     

Comparative study of browning and flavan‐3‐ols during the storage of white sherry wines treated with different fining agents

White sherry wines were treated with three fining agents (activated charcoal, PVPP and Riduxhigh), in addition to an initial treatment with casein and bentonite, in four different combinations. The wines were stored at 20 or 30 °C for 1 year with a view to examining changes in their flavan‐3‐ol fraction and differences in their degree of sensitivity to browning. Flavan‐3‐ol monomers and dimers, as well as browning measured as absorbance at 420 nm, increased during storage in all the wines. After this period the wines treated with fining agents containing activated charcoal, PVPP and Riduxhigh exhibited less marked browning, with no significant differences among them at both 20 and 30 °C. However, taking into account the higher initial colour of bottled wines treated with Riduxhigh in relation to those treated with activated charcoal or PVPP, this fining agent showed higher capacity to control browning. © 2000 Society of Chemical Industry     

Centrifugal partition chromatography followed by HPLC for the isolation of cis-ε-viniferin,a resveratrol dimer newly extracted from a red Algerian wine

Grapes and related products are considered the major dietary sources of stilbenes. Among these compounds, trans-resveratrol is one of the most important in terms of biological activity, since it has been reported to prevent or to slow the progression of a wide variety of illnesses. We report for the first time the isolation and structure elucidation of cis-ε-viniferin, a biologically active resveratrol dihydrodimer from a red Algerian wine. The Merlot wine was fractionated by column chromatography followed by centrifugal partition chromatography (CPC) and then by reverse-phase semi-preparative HPLC. The structure of cis-ε-viniferin was elucidated by means of 1H NMR and 2D correlations. Cis-ε-viniferin concentrations were determined in wine samples originating from North Africa, most of which are commercially available in France. Stilbene quantification was based on an HPLC method with diode array detection. Unlike trans-ε-viniferin, cis-ε-viniferin was present in almost all wine samples studied and the concentrations ranged from 0.10 to 1.12 mg/l.     

Determination of trans-resveratrol in red wine by adsorptive stripping square-wave voltammetry with medium exchange

In the present paper, a method for the determination of trans-resveratrol in red wine samples, by adsorptive stripping square-wave voltammetry (Ad-SSWV) in a glassy carbon electrode, is presented. In 0.10 M perchloric medium, trans-resveratrol experiments an adsorptive–oxidative process, which promotes the appearance of a peak at 0.72 V. Calibration graph have been constructed from 5.0 to 35 ng/mL. Detection limit of 4.2 ng/mL has been calculated, according to Clayton criterion. Extraction of trans-resveratrol from red wine with diethylether and posterior clean-up with C18 cartridges is carried out. Recovery percentages close to 100% have been calculated with different red wine samples. The accumulation of analyte in the electrode is carried out at +0.60 V for 60 s, in the presence of 0.10 M HClO₄ and 10% of ethanol; the measurement stage is performed after a medium exchange, in 0.10 M HClO₄ and 30% of ethanol. The standard addition method was employed for the analysis of real samples, since a matrix effect is observed in red wine extract. The method has been applied to several commercial red wines samples, and the results have been satisfactorily validated by HPLC.     

The application of an improved method for trans-resveratrol to determine the origin of Greek red wines

A rapid and sensitive method has been developed for the determination of trans-resveratrol in wine. This method consists of a solid phase extraction step followed by a rapid HPLC quantification step (30 min). The improvement of this method consists of the washing step of the solid phase extraction method carried out at pH 8.0 (12% ethanol in a phosphate buffer solution), thus permitting a more efficient removal of the interfering phenolic compounds in conjunction with the required low volume of tested sample. Trans-resveratrol content was determined for 29 red Greek wines of appellation of origin. The concentrations found varied between 0.550 and 2.534 mg/l. The wines produced by grape varieties grown in the Greek islands (Rhodes, Crete and Paros) were richer in trans-resveratrol. The grape variety Mandilaria, in particular, was the Greek variety with the highest trans-resveratrol content.