Food Chemistry 133 (2012) 271–276
Contents lists available at SciVerse ScienceDirect
Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Evolution of the colour, antioxidant activity and polyphenols in unusually aged Sherry wines Mónica Schwarz ⇑, M. Carmen Rodríguez, Dominico A. Guillén, Carmelo G. Barroso Centro Andaluz de Investigaciones Vitivinícolas (CAIV), Agrifood Campus of International Excellence, University of Cádiz, P.O. Box 40, Pol. Río San Pedro, 11510 Puerto Real, Cádiz, Spain
a r t i c l e
i n f o
Article history: Received 23 November 2010 Received in revised form 3 October 2011 Accepted 14 January 2012 Available online 25 January 2012 Keywords: Ageing Antioxidant activity Polyphenols Colour Sherry wine
a b s t r a c t The present paper reports the results of a study monitoring several key analytical parameters in a set of aged samples of vintages from 1999 back to 1935. The analysed parameters were: colour, antioxidant activity, low molecular weight phenolics, index of total polyphenols and SO2 content. It can be concluded that the antioxidant activity of the old wines studied is clearly related to the ageing time and to the polyphenols extracted from the wood during this period. The wines also showed differences in their chromatic characteristics according to the duration of their ageing in years. A principal component analysis confirmed that most of the studied variables (except hydroximethylfurfural and SO2) are strictly linked to ageing, which allowed a discrimination of 100% of the wines belonging to different decades, according to the results obtained by means of the application of linear discriminant analysis. Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction Many studies have been published about the relationship between the consumption of antioxidants and decreases in the incidence of certain cardiovascular diseases and cancer (Frankel, Waterhouse, & Teissedre, 1995; Satue´-Gracia et al., 1999). The antioxidant activity of wine is largely due to its polyphenolic compounds (Alonso, Guillén, Barroso, Puertas, & García, 2002; De Quirós, Lage-Yusty, & López-Hernández, 2009; Ferna´ndez-Pacho´n, Villaño, Troncoso, & Garci´a-Parrilla, 2006; Paixão, Perestrelo, Marques, & Câmara, 2007). These polyphenolic compounds are contributed not only by the raw material of the wine, the grapes, but also by the wood of the casks in which it is aged. This process is influenced by diverse factors such as the type of wood (Cerezo et al., 2010; Frangipane, Santis, & Ceccarelli, 2007; Herna´ndez, Estrella, Dueñas, De Simo´n, & Cadahi´a, 2007) and the toasting that may be applied to the inner surface of the cask (Cadahía, Muñoz, De Simón, & García-Vallejo, 2001). Since there is a tendency for the concentration of polyphenolic compounds in the wine to increase during the course of its ageing process (Del Alamo Sanza, Escudero, & De Castro Torío, 2004), in principle it should be possible to establish a direct relationship between the antioxidant activity of a particular wine and the duration of the time it has spent ageing in wood. However, the time spent ageing in wood is not ⇑ Corresponding author. Address: Department of Analytical Chemistry, Faculty of Sciences, University of Cádiz, República Saharui s/n, 11510-Puerto Real, Cádiz, Spain. Tel.: +34 956016363; fax: +34 956016460. E-mail address: [email protected] (M. Schwarz). 0308-8146/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2012.01.019
the only factor influencing the concentration of polyphenolic compounds in wine: the concentration also depends on diverse factors including the variety of grape utilised (Bosso, Guaita, Panero, Borsa, & Follis, 2009) and the production process utilised in the winemaking (Ortega et al., 2008). Due to these facts and also due to the fact that not all polyphenolic compounds present the same antioxidant activity (Alonso, Castro, Rodríguez, Guillén, & Barroso, 2004), this may vary. Several authors have studied the evolution of the polyphenols of low molecular weight in various enological products of Jerez during their period of ageing. García Moreno and Garcia Barroso (2002) studied this evolution during one year in three different types of Sherry wine aged by the dynamic system of solera and criaderas, and identified the differences between them; Tesfaye, Morales, Garci´a-Parrilla, and Troncoso (2002) studied the evolution over two years of polyphenols in aged Sherry wine vinegars; they found a considerable increase in the concentration of the majority of the compounds over the course of the period of time studied. In addition, there are many studies describing the evolution of colour in wines during their ageing (Del Alamo et al., 2004; Garci´a-Puente Rivas, Alcalde-Eon, Santos-Buelga, Rivas-Gonzalo, & Escribano-Bailo´n, 2006), and in some cases this evolution has been used as a parameter indicative of the age of the enological product studied (Del Álamo, Nevares, Gallego, Martin, & Merino, 2008). Among the studies of colour in Sherry wines, one of the most relevant is that carried out by Recamales, Hernanz, Álvarez, González-Miret, and Heredia (2007) on amontillado wine, utilising the colour as a parameter indicative of the type of wood in which the wine has been aged.
272
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
The evolution of the chromatic characteristics, the antioxidant activity and the polyphenols content are studied, together with the relationship between these last two parameters, in old Sherry wines. Secondary objectives are to check if the antioxidant activity of a wine is increased by the polyphenols passed from the wood to the wine as a result of the ageing of the wine in oak casks, and to determine whether such an increase in antioxidant activity can be related directly to the age of the wine, whether it, can be also used as one of the parameters for indicating the quality of the product. In addition the set of samples has been treated statistically, and a model has been obtained that would allow an unknown sample to be classified in function of its age.
2. Materials and methods
2.4. Measurement of the antioxidant activity The majority of methods for measuring antioxidant activity are based on the inhibition of certain reactions in the presence of antioxidants. The most frequently used methods consider the generation of free radicals, which disappear by the effect of antioxidants. The method used in this work (Alonso, Guillen, & Barroso, 2003) has been developed and validated in the research group, on the basis of a previous design (an electrochemical test of accelerated browning). It consists of the electrochemical oxidation of a solution of ABTS (50 lM), to which the sample to be tested was added. Initially, a continuous current of 2 mA was applied, and results are recorded at 414 and 734 nm; these are the two wavelengths at which ABTS+ presents its principal maximum values. The response function monitored is the amount of electric charge, in coulombs, required for the oxidation of the added sample.
2.1. Samples 2.5. Analysis by UPLC The 26 samples analysed in this study correspond to wines aged by the static system of añadas, from vintages ranging from 1935 to 1999. These Sherry wines are of the oloroso type, and therefore have been made by the oxidative method (not with secondary fermentation under flor yeasts), with white grapes of the Palomino Fino variety, and aged in barrels of American oak. The samples and the data corresponding to the age of each wine were supplied by Bodegas Williams & Humbert; this company operates a special winery for wines of this type. The samples analysed in the present work are considered to be extremely valuable, since in some cases they constitute samples of very rare and very old wine, aged according to the static system of vintages (añadas) from years between 1935 and 1999.
2.2. Reagents Folin reagent (Sigma–Aldrich, Madrid, Spain) and sodium carbonate (Panreac, Barcelona, Spain) were employed for measurement of the Folin–Ciocalteu total polyphenolic index. The calibration curve was constructed using gallic acid (Merck, Darmstadt, Germany). A saturated solution of Zn (CH3COO)2 (Panreac) and a solution of 2,20 -azino-bis (3ethylbenzthiazoline-6-sulphonic acid) (ABTS) (Sigma–Aldrich) in a phosphate buffer medium (pH 6) were used in the electrolytic system. 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), supplied by Sigma–Aldrich, was used to construct the calibration curve. The solvents employed for the UPLC analysis were prepared with acetonitrile, acetic acid (HPLC quality, Scharlau, Barcelona, Spain) and water purified in a Milli-Q system (Millipore, Bedford, MA). Calibration curves were constructed for the polyphenols identified, supplied by Sigma Aldrich, Merck, and Fluka (Buchs, Switzerland). The pure compounds were added to a solution of Milli-Q water containing ethanol (15% v/v) and adjusted to pH 3.5 with tartaric acid.
2.3. Index of total polyphenols and determination of SO2 Total Phenols were determined using the Folin–Ciocalteu reagent (Singleton & Rossi, 1965). The reaction mixture contained 250 lL of sample, 1250 lL of Folin–Ciocalteu reagent and 5 mL of 20% sodium carbonate. Dilutions were carried out in duplicate and calculated from a calibration curve obtained with gallic acid. The absorbance was measured at 750 nm. Determination of SO2 was performed according to the OIV method (OIV, 2009).
The determination of phenolic compounds was performed following the method developed by Schwarz, Rodriguez, Guillén, and Barroso (2009). These analyses were performed on Waters Acquity UPLC system coupled to a photodiode array detection device. An Acquity UPLC BEH C18 column (100 2.1 mm I.D., with 1.7 lm particle size), also from Waters, was used. The column temperature was maintained at 47 °C. The binary system phases were: A (3% acetonitrile, 2% acetic acid, 95% water) and B (85% acetonitrile, 2% acetic acid, 13% water), with a flow rate of 0.7 mL min1, giving a maximum back pressure of 10,400 psi, which is within the capabilities of the UPLC. The injection volume was 2.5 lL. The 6.5 min gradient was as follows: 0 min 100% A, 3 min 90% A (curve 6), 4 min 90% A, 6.5 min 25% A (curve 6). Finally, the column was washed with 100% B for 3 min and equilibrated with 100% A for 3 min. All the samples were filtered through 0.22 lm nylon filters from Scharlab (Barcelona, Spain). The identification of each compound was carried out by comparing retention times and UV–Vis spectra of the peaks in wine with those previously obtained by the injection of standards. 2.6. Colour Colour measurements were made using a Helios UV–Vis spectrophotometer over the visible range 380–770 nm. Colour analyses were carried out following the method of the CIE (Commission Internationale de l´Eclairage) (C.I.E., 1986). 2.7. Data treatment For each compound or parameter, one-way ANOVA was initially used to determine significant differences between the several groups of samples. A principal component analysis was employed to study the influence of the different parameters which have been studied in ageing. A linear discriminant analysis (LDA) was performed to obtain the equations that would enable a particular sample to be classified according to the age. The Statistica 7.0 program (Tulsa, Oklahoma, USA) was used for all these analyses. 3. Results and discussion 3.1. Evolution of the polyphenols studied Fig. 1 shows the evolution of the different compounds quantified in the samples from the different vintages. As can be observed,
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
273
Fig. 1. Evolution of the different polyphenolic compounds studied.
Fig. 2. Typical Chromatograms of aged Sherry wines, vintage 1935 (A) and vintage 1980 (B). Detection wavelength was set at 280 nm. (1) 5-Hydroxymethylfurfural, (2) protocatechuic acid, (3) furfural, (4) protocatechualdehyde, (5) p-hydroxybenzoic acid, (6) Tyrosol, (7) vanillic acid, (8) p-hydroxybenzaldehyde, (9) syringic acid, (10) vanillin, (11) p-coumaric acid and (12) syringaldehyde.
to stay constant as a consequence of the periodic dilutions of older with younger wine in the transfers between scales, during the samplings (Rodriguez, Guillén, Schwarz, & Barroso, 2010). However, the samples used in the present study have been aged by a static system of ageing; therefore logically, practically all the compounds are expected to show increasing concentration levels in line with the increased length of ageing period. In addition, in the relevant reference studies found, the evolution was monitored over periods of time notably shorter than those considered in the present work. The compounds that are found in higher concentration in the samples aged for longer periods are the furanic aldehydes (hydroxymethylfurfural and furfural), protocatechuic acid, tyrosol, p-coumaric acid and syringaldehyde. The furanic aldehydes, especially hydroxymethylfurfural, are majority compounds in the various different enological products of the zone of Jerez, in wines (García Moreno et al., 2002), brandies (Schwarz, Rodríguez, Martínez, Bosquet, Guillén & Barroso, 2009) and vinegars (Tesfaye et al., 2002). There are two fundamental reasons for the presence of these furanic compounds: the addition of caramel colouring (Quesada, Villalón, Lopez, & López Martinez, 1996) and the ageing in wood (Rodri´guez-Bencomo, Ortega-Heras, Pe´rez-Magarin~o, Gonza´lezHuerta, & Gonza´lez-San Jose´, 2008). However, because the colour of the analysed samples has not been rectified by the addition of caramel, the presence of the furfuraldehydes in our samples must be due to their ageing in wood. Typical chromatograms of aged sherry wines are shown in Fig. 2. As expected, the highest concentration of polyphenols is found in the wine with the longest ageing, whereas the youngest wine has a lower amount of polyphenols.
3.2. Antioxidant activity, index of total polyphenols and SO2 content in general, the concentration of each compound studied tended to be higher in the wines aged for more years. García Moreno et al. (2002) studied the evolution of polyphenols in oloroso, fino and amontillado Sherry wines aged in a dynamic system of Solera and Criaderas. In their investigations in respect of oloroso wine, they observed that the concentration of the benzoic acids was higher in the samples aged for longer periods but that similar increased levels were not observed for the rest of the compounds studied. The difference of behaviour between those samples and the ones of our study is very probably due to the system of ageing. In the dynamic system of solera and criaderas, the concentration of the compounds increases in the initial years of ageing but later tends
If the evolution of the antioxidant activity is observed in relation to the years of ageing, it can be seen that, in general, there is a rising evolution in line with the length of ageing period of the samples, with values ranging from 0.19 mM Trolox for the youngest wine to 5.6 mM Trolox for the oldest one. In addition it can be seen that the oldest samples present an extraordinarily high antioxidant activity. Taking into account that the wines studied are made with white grapes, which have lower polyphenolic content and less antioxidant activity than the black varieties, it can safely be assumed that the high antioxidant activity of these samples is due to the polyphenols that have been contributed during the long
274
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
value of the luminosity parameter L⁄) with an increase of the red and yellow tonalities (larger values of a⁄ and b⁄), with differences in magnitude, which translates to a tone (H⁄) with a greater contribution of red. In Fig. 3, a projection of the CIELab variables a⁄ against b⁄, it is observed that there is a certain ranking in function of the age of the samples. 3.4. Statistical treatment
⁄
⁄
Fig. 3. CIELab colour parameters of aged sherry wines in a b plane.
period of ageing in wood. Therefore the degree of antioxidant activity is clearly related to the length of ageing in wood. The index of total polyphenols and the antioxidant activity were measured for all the samples, and a good relationship, r2 = 0.8416, has been found. Thus the strong influence of the polyphenols on the antioxidant activity is confirmed. However, as stated by other authors (Alonso et al., 2004), not all polyphenols have the same influence on the antioxidant activity; for this reason it is important to study the relationship between the individual polyphenols studied and the antioxidant activity measured in the samples. Protocatechuic acid, protocatechuic aldehyde, syringic acid, vanillin and p-coumaric acid are the compounds that show the closest correlations (r2 > 0.7). These results appear to be consonant with those reported by Alonso et al. (2004), who also obtained a good correlation for these same compounds (except protocatechuic aldehyde) in Sherry wine vinegars aged in wood. The possible correlation between antioxidant activity and SO2 content was then assessed. The SO2 concentrations which were obtained for this group of wines varied between 8 and 17 mg L1. When it was correlated with the antioxidant activity, an r2 of 0.23 was obtained, which shows that the influence of SO2 in the antioxidant activity is not significant in this case.
3.3. Colour In accordance with the values of the chromatic parameters, the samples aged for longer periods present a darker colour (a lower
Taking into account the vintage, the aged samples were grouped in seven different sets, in function of the decade in which the ageing of the samples was initiated. A statistical study was made of all the samples analysed. First, an analysis of the variance was performed to investigate the possibility of differentiating the various groups pre-established, based on these compounds. All the variables presented statistically significant differences between the seven groups of samples (p < 0.05). However, on performing the post hoc (Bonferroni) comparisons, it was found that none of the compounds allowed the discrimination between the seven groups; therefore it was decided to apply multivariate analysis to all the samples using linear discriminant analysis (LDA). The concentrations of the polyphenols and furanic aldehydes were expressed in mg L1. On applying the LDA to the set of samples, the equations are obtained that allow an unknown sample to be classified to one of the groups previously defined according to its mean time of ageing. Thus, Table 1 presents the functions of classification that would make possible the assignment of age. The most discriminant, participating variables were: antioxidant activity, total phenolic content, protocatechuic aldehyde, protocatechuic acid, p-hydroxybenzoic acid, p-hydroxybenzaldehyde and hydroxymethylfurfural. A classification of 100% was obtained as can be observed in Fig. 4a, in which a certain ranking of the samples according to their age by component 2 is observed. In this component the variables that obtained a greater weight were syringic acid, syringaldehyde, vanillic acid, p-coumaric acid, p-hydroxybenzoic acid and the index of total polyphenols; all of these parameters are directly correlated with the length of ageing in wood, which would explain this ranking. A principal component analysis was employed to study the influence of the variables in the ageing of the samples. The first
Table 1 Classification functions.
TPI p-Hydroxybenzoic acid Protocatechuicaldehyde 5-Hydrox ymethylfurfural b⁄ Antioxidant activity Syringaldehyde p-Hydroxybenzaldehyde Protocatechuic acid Syringic acid L⁄ Furfural C⁄ H⁄ p-Coumaric acid Vanillic acid Constant
Samples from 1935 to 1940
Samples from 1941 to 1950
Samples from 1951 to 1960
Samples from 1961 to 1970
Samples from 1971 to 1980
Samples from 1981 to 1990
Samples from 1991 to 1999
18 9951 14,630 287
21 11,261 16,479 329
20 10,733 15,757 314
20 10,852 15,931 317
19 10,337 15,215 301
20 10,728 15,797 314
20 10,665 15,672 314
1277 19,836 1512 16.86 31.61 28.81 1284 23 424 1829 3985 1748 1343.53
1437 22,546 1733 34.73 37.98 35.89 1465 0 478 2062 4413 1931 1740.46
1403 21,545 1655 27.75 36.73 34.61 1401 0 457 2002 4230 1845 1613.32
1404 21,759 1668 23.52 33.97 31.60 1413 4 463 2009 4284 1872 1402.12
1354 20,737 1589 21.99 34.86 32.24 1341 5 442 1931 4105 1792 1462.90
1416 21,586 1657 24.15 36.55 34.33 1398 3 459 2017 4241 1850 1589.69
1430 21,489 1656 33.22 38.07 37.34 1400 9 456 2030 4198 1822 1665.84
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
275
Fig. 4. Statistical treatment. (a) Distribution in the canonical space derived from the LDA for the aged wines elaborated in different decades. (b) PCA performed on the following parameters: colour, antioxidant activity, low molecular weight phenolics, TPI and SO2 content. Scatterplot of the samples onto the plane defined by the first two principals components extracted.
Table 2 Factor loadings of the two first principal components extracted. Variable
CP1
CP2
Hydroxymethylfurfural Protocatechuic acid Furfural Protocatechualdehyde p-Hydroxybenzoic acid Tyrosol Vanillic acid p-Hydroxybenzaldehyde Syringic acid Vanillin p-Coumaric Syringaldehyde L⁄ a⁄ b⁄ H⁄ C⁄ Antioxidant activity TPI SO2
0.569 0.941 0.729 0.919 0.943 0.953 0.898 0.942 0.933 0.962 0.961 0.908 0.929 0.956 0.769 0.961 0.842 0.901 0.862 0.569
0.545 0.192 0.010 0.077 0.013 0.109 0.257 0.044 0.297 0.152 0.071 0.241 0.093 0.095 0.449 0.104 0.387 0.082 0.161 0.581
three principal components explain 89.61% of the total variance, although the first component, which alone explains 77.75%, contributes most. As can be observed in Fig. 4b, the samples are ordered along component one, being the most aged ones to the left and the least aged ones to the right, being possible, as a result, to relate component 1 with ageing. If we observe the weight of the variables (Table 2), we can see that most of them are related to such component, confirming the relationship of the studied variables with the ageing of the samples. Further, it is seen that hydroxymethylfurfural and SO2 are more weakly associated with component 1. 4. Conclusions Considering the aforementioned results, it can be concluded that the antioxidant activity of the old wines studied is a parameter clearly related to the ageing of the wine in cask, and to the polyphenols contributed by the wood during this period. Among the polyphenolic compounds studied, those that presented better correlation with antioxidant activity were protocatechuic acid, protocatechuic aldehyde and syringic acid. The wines also showed differences in their chromatic characteristics according to the
duration of ageing in years. The close relationship of the studied parameters with the ageing of the wines has been confirmed by the principal components analysis which has been carried out to the samples. Further, a linear discriminating analysis was successfully used to obtain a statistical model that allowed samples to be well discriminated in function of the length of their ageing. Acknowledgements The authors are most grateful to Bodegas Williams & Humbert for providing the samples. This study has been financed by Project P05-AGR-00767. References Alonso, Á. M., Castro, R., Rodríguez, M. C., Guillén, D. A., & Barroso, C. G. (2004). Study of the antioxidant power of brandies and vinegars derived from Sherry wines and correlation with their content in polyphenols. Food Research International, 37, 715–721. Alonso, A. M., Guillen, D., & Barroso, C. G. (2003). Development of an electrochemical method for the determination of antioxidant activity. Application to grapederived products. European Food Research and Technology, 216, 445–448. Alonso, A. M., Guillén, D. A., Barroso, C. G., Puertas, B., & García, A. (2002). Determination of antioxidant activity of wine byproducts and its correlation with polyphenolic content. Journal of Agricultural and Food Chemistry, 50, 5832–5836. Bosso, A., Guaita, M., Panero, L., Borsa, D., & Follis, R. (2009). Influence of two winemaking techniques on polyphenolic composition and color of wines. American Journal of Enology and Viticulture, 60, 379–385. C.I.E. (1986). Colorimetry, 2nd ed. Publication C.I.E. No.15.2, Central Bureau of the Commission Internationale de L’Eclairage, Vienna. Cadahía, E., Muñoz, L., De Simón, B. F., & García-Vallejo, M. C. (2001). Changes in low molecular weight phenolic compounds in Spanish, French, and American oak woods during natural seasoning and toasting. Journal of Agricultural and Food Chemistry, 49, 1790–1798. Cerezo, A. B., Tesfaye, W., Soria-Diaz, M. E., Torija, M. J., Mateo, E., García-Parrilla, M. C., & Troncoso, A. M. (2010). Effect of wood on the phenolic profile and sensory properties of wine vinegars during ageing. Journal of Food Composition and Analysis, 23, 175–184. De Quirós, A. R.-B., Lage-Yusty, M. A., & López-Hernández, J. (2009). HPLC-analysis of polyphenolic compounds in Spanish white wines and determination of their antioxidant activity by radical scavenging assay. Food Research International, 42, 1018–1022. Del Álamo, M., Nevares, I., Gallego, L., Martin, C., & Merino, S. (2008). Aging markers from bottled red wine aged with chips, staves and barrels. Analytica Chimica Acta, 621, 86–99. Del Alamo Sanza, M., Escudero, J. A. F., & De Castro Tori´o, R. (2004). Changes in phenolic compounds and colour parameters of red wine aged with oak chips and in oak barrels. Food Science and Technology International, 10, 233–241. Ferna´ndez-Pacho´n, M. S., Villaño, D., Troncoso, A. M., & Garci´a-Parrilla, M. C. (2006). Determination of the phenolic composition of sherry and table white wines by liquid chromatography and their relation with antioxidant activity. Analytica Chimica Acta, 563, 101–108.
276
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
Frangipane, M. T., Santis, D. D., & Ceccarelli, A. (2007). Influence of oak woods of different geographical origins on quality of wines aged in barriques and using oak chips. Food Chemistry, 103, 46–54. Frankel, E. N., Waterhouse, A. L., & Teissedre, P. L. (1995). Principal phenolic phytochemicals in selected California wines and their antioxidant activity in inhibiting oxidation of human low-density lipoproteins. Journal of Agricultural and Food Chemistry, 43, 890–894. García Moreno, M. V., & Garcia Barroso, C. (2002). Comparison of the evolution of low molecular weight phenolic compounds in typical Sherry wines: Fino, amontillado, and oloroso. Journal of Agricultural and Food Chemistry, 50, 7556–7563. Garci´a-Puente Rivas, E., Alcalde-Eon, C., Santos-Buelga, C., Rivas-Gonzalo, J. C., & Escribano-Bailo´n, M. T. (2006). Behaviour and characterisation of the colour during red wine making and maturation. Analytica Chimica Acta, 563, 215–222. Herna´ndez, T., Estrella, I., Duen~as, M., De Simo´n, B. F., & Cadahi´a, E. (2007). Influence of wood origin in the polyphenolic composition of a Spanish red wine aging in bottle, after storage in barrels of Spanish, French and American oak wood. European Food Research and Technology, 224, 695–705. Organisation International de la Vigne et du Vin (2009). Compendium of international methods of wine and must analysis (Vols. I and II), Paris. Ortega, T., De La Hera, E., Carretero, M. E., Gómez-Serranillos, P., Naval, M. V., Villar, A. M., Prodanov, M., Vacas, V. B., Arroyo, T., Hernández, T., & Estrella, I. (2008). Influence of grape varieties and their phenolic composition on vasorelaxing activity of young red wines. European Food Research and Technology, 227, 1641–1650. Paixão, N., Perestrelo, R., Marques, J. C., & Câmara, J. S. (2007). Relationship between antioxidant capacity and total phenolic content of red, rosé and white wines. Food Chemistry, 105, 204–214. Quesada, Granados. J., Villalón, Mir. M., Lopez, Serrana. H., & López Martinez, M. C. (1996). The influence of added caramel on furanic aldehyde content of matured brandies. Food Chemistry, 56, 415–419.
Recamales, A. F., Hernanz, D., Álvarez, C., González-Miret, M. L., & Heredia, F. (2007). Colour of Amontillado wines aged in two oak barrel types. Journal of European Food Research and Technology, 224, 321–327. Rodriguez, M. C., Guillén, D., Schwarz, M., & Barroso, C. G. (2010). Phenolic compounds and furanic derivatives in the characterization and quality control of Brandy de Jerez. Journal of Agricultural and Food Chemistry, 58, 990–997. Rodri´guez-Bencomo, J. J., Ortega-Heras, M., Pe´rez-Magarin~o, S., Gonza´lez-Huerta, C., & Gonza´lez-San Jose´, M. L. (2008). Importance of chip selection and elaboration process on the aromatic composition of finished wines. Journal of Agricultural and Food Chemistry, 56, 5102–5111. Satue´-Gracia, M. T., Andre´s-Lacueva, C., Lamuela-Ravento´s, R. M., & Frankel, E. N. (1999). Spanish sparkling wines (Cavas) as inhibitors of in vitro human lowdensity lipoprotein oxidation. Journal of Agricultural and Food Chemistry, 47, 2198–2202. Schwarz, M., Rodríguez, M. C., Guillén, D. A., & Barroso, C. G. (2009). Development and validation of UPLC for the determination of phenolic compounds and furanic derivatives in Brandy de Jerez. Journal of Separation Science, 32, 1782–1790. Schwarz, M., Rodríguez, M., Martínez, C., Bosquet, V., Guillén, D., & Barroso, C. G. (2009). Antioxidant activity of Brandy de Jerez and other aged distillates, and correlation with their polyphenolic content. Food Chemistry, 116, 29–33. Singleton, V. L., & Rossi, Joseph. A. (1965). Colorimetry of total phenolics with phosphomolybdic–phosphotungstic acid reagents. American Journal of Enology and Viticulture, 16, 144–158. Tesfaye, W., Morales, M. L., Garci´a-Parrilla, M. C., & Troncoso, A. M. (2002). Evolution of phenolic compounds during an experimental aging in wood of Sherry vinegar. Journal of Agricultural and Food Chemistry, 50, 7053–7061.
Contents lists available at SciVerse ScienceDirect
Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Evolution of the colour, antioxidant activity and polyphenols in unusually aged Sherry wines Mónica Schwarz ⇑, M. Carmen Rodríguez, Dominico A. Guillén, Carmelo G. Barroso Centro Andaluz de Investigaciones Vitivinícolas (CAIV), Agrifood Campus of International Excellence, University of Cádiz, P.O. Box 40, Pol. Río San Pedro, 11510 Puerto Real, Cádiz, Spain
a r t i c l e
i n f o
Article history: Received 23 November 2010 Received in revised form 3 October 2011 Accepted 14 January 2012 Available online 25 January 2012 Keywords: Ageing Antioxidant activity Polyphenols Colour Sherry wine
a b s t r a c t The present paper reports the results of a study monitoring several key analytical parameters in a set of aged samples of vintages from 1999 back to 1935. The analysed parameters were: colour, antioxidant activity, low molecular weight phenolics, index of total polyphenols and SO2 content. It can be concluded that the antioxidant activity of the old wines studied is clearly related to the ageing time and to the polyphenols extracted from the wood during this period. The wines also showed differences in their chromatic characteristics according to the duration of their ageing in years. A principal component analysis confirmed that most of the studied variables (except hydroximethylfurfural and SO2) are strictly linked to ageing, which allowed a discrimination of 100% of the wines belonging to different decades, according to the results obtained by means of the application of linear discriminant analysis. Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction Many studies have been published about the relationship between the consumption of antioxidants and decreases in the incidence of certain cardiovascular diseases and cancer (Frankel, Waterhouse, & Teissedre, 1995; Satue´-Gracia et al., 1999). The antioxidant activity of wine is largely due to its polyphenolic compounds (Alonso, Guillén, Barroso, Puertas, & García, 2002; De Quirós, Lage-Yusty, & López-Hernández, 2009; Ferna´ndez-Pacho´n, Villaño, Troncoso, & Garci´a-Parrilla, 2006; Paixão, Perestrelo, Marques, & Câmara, 2007). These polyphenolic compounds are contributed not only by the raw material of the wine, the grapes, but also by the wood of the casks in which it is aged. This process is influenced by diverse factors such as the type of wood (Cerezo et al., 2010; Frangipane, Santis, & Ceccarelli, 2007; Herna´ndez, Estrella, Dueñas, De Simo´n, & Cadahi´a, 2007) and the toasting that may be applied to the inner surface of the cask (Cadahía, Muñoz, De Simón, & García-Vallejo, 2001). Since there is a tendency for the concentration of polyphenolic compounds in the wine to increase during the course of its ageing process (Del Alamo Sanza, Escudero, & De Castro Torío, 2004), in principle it should be possible to establish a direct relationship between the antioxidant activity of a particular wine and the duration of the time it has spent ageing in wood. However, the time spent ageing in wood is not ⇑ Corresponding author. Address: Department of Analytical Chemistry, Faculty of Sciences, University of Cádiz, República Saharui s/n, 11510-Puerto Real, Cádiz, Spain. Tel.: +34 956016363; fax: +34 956016460. E-mail address: [email protected] (M. Schwarz). 0308-8146/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2012.01.019
the only factor influencing the concentration of polyphenolic compounds in wine: the concentration also depends on diverse factors including the variety of grape utilised (Bosso, Guaita, Panero, Borsa, & Follis, 2009) and the production process utilised in the winemaking (Ortega et al., 2008). Due to these facts and also due to the fact that not all polyphenolic compounds present the same antioxidant activity (Alonso, Castro, Rodríguez, Guillén, & Barroso, 2004), this may vary. Several authors have studied the evolution of the polyphenols of low molecular weight in various enological products of Jerez during their period of ageing. García Moreno and Garcia Barroso (2002) studied this evolution during one year in three different types of Sherry wine aged by the dynamic system of solera and criaderas, and identified the differences between them; Tesfaye, Morales, Garci´a-Parrilla, and Troncoso (2002) studied the evolution over two years of polyphenols in aged Sherry wine vinegars; they found a considerable increase in the concentration of the majority of the compounds over the course of the period of time studied. In addition, there are many studies describing the evolution of colour in wines during their ageing (Del Alamo et al., 2004; Garci´a-Puente Rivas, Alcalde-Eon, Santos-Buelga, Rivas-Gonzalo, & Escribano-Bailo´n, 2006), and in some cases this evolution has been used as a parameter indicative of the age of the enological product studied (Del Álamo, Nevares, Gallego, Martin, & Merino, 2008). Among the studies of colour in Sherry wines, one of the most relevant is that carried out by Recamales, Hernanz, Álvarez, González-Miret, and Heredia (2007) on amontillado wine, utilising the colour as a parameter indicative of the type of wood in which the wine has been aged.
272
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
The evolution of the chromatic characteristics, the antioxidant activity and the polyphenols content are studied, together with the relationship between these last two parameters, in old Sherry wines. Secondary objectives are to check if the antioxidant activity of a wine is increased by the polyphenols passed from the wood to the wine as a result of the ageing of the wine in oak casks, and to determine whether such an increase in antioxidant activity can be related directly to the age of the wine, whether it, can be also used as one of the parameters for indicating the quality of the product. In addition the set of samples has been treated statistically, and a model has been obtained that would allow an unknown sample to be classified in function of its age.
2. Materials and methods
2.4. Measurement of the antioxidant activity The majority of methods for measuring antioxidant activity are based on the inhibition of certain reactions in the presence of antioxidants. The most frequently used methods consider the generation of free radicals, which disappear by the effect of antioxidants. The method used in this work (Alonso, Guillen, & Barroso, 2003) has been developed and validated in the research group, on the basis of a previous design (an electrochemical test of accelerated browning). It consists of the electrochemical oxidation of a solution of ABTS (50 lM), to which the sample to be tested was added. Initially, a continuous current of 2 mA was applied, and results are recorded at 414 and 734 nm; these are the two wavelengths at which ABTS+ presents its principal maximum values. The response function monitored is the amount of electric charge, in coulombs, required for the oxidation of the added sample.
2.1. Samples 2.5. Analysis by UPLC The 26 samples analysed in this study correspond to wines aged by the static system of añadas, from vintages ranging from 1935 to 1999. These Sherry wines are of the oloroso type, and therefore have been made by the oxidative method (not with secondary fermentation under flor yeasts), with white grapes of the Palomino Fino variety, and aged in barrels of American oak. The samples and the data corresponding to the age of each wine were supplied by Bodegas Williams & Humbert; this company operates a special winery for wines of this type. The samples analysed in the present work are considered to be extremely valuable, since in some cases they constitute samples of very rare and very old wine, aged according to the static system of vintages (añadas) from years between 1935 and 1999.
2.2. Reagents Folin reagent (Sigma–Aldrich, Madrid, Spain) and sodium carbonate (Panreac, Barcelona, Spain) were employed for measurement of the Folin–Ciocalteu total polyphenolic index. The calibration curve was constructed using gallic acid (Merck, Darmstadt, Germany). A saturated solution of Zn (CH3COO)2 (Panreac) and a solution of 2,20 -azino-bis (3ethylbenzthiazoline-6-sulphonic acid) (ABTS) (Sigma–Aldrich) in a phosphate buffer medium (pH 6) were used in the electrolytic system. 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), supplied by Sigma–Aldrich, was used to construct the calibration curve. The solvents employed for the UPLC analysis were prepared with acetonitrile, acetic acid (HPLC quality, Scharlau, Barcelona, Spain) and water purified in a Milli-Q system (Millipore, Bedford, MA). Calibration curves were constructed for the polyphenols identified, supplied by Sigma Aldrich, Merck, and Fluka (Buchs, Switzerland). The pure compounds were added to a solution of Milli-Q water containing ethanol (15% v/v) and adjusted to pH 3.5 with tartaric acid.
2.3. Index of total polyphenols and determination of SO2 Total Phenols were determined using the Folin–Ciocalteu reagent (Singleton & Rossi, 1965). The reaction mixture contained 250 lL of sample, 1250 lL of Folin–Ciocalteu reagent and 5 mL of 20% sodium carbonate. Dilutions were carried out in duplicate and calculated from a calibration curve obtained with gallic acid. The absorbance was measured at 750 nm. Determination of SO2 was performed according to the OIV method (OIV, 2009).
The determination of phenolic compounds was performed following the method developed by Schwarz, Rodriguez, Guillén, and Barroso (2009). These analyses were performed on Waters Acquity UPLC system coupled to a photodiode array detection device. An Acquity UPLC BEH C18 column (100 2.1 mm I.D., with 1.7 lm particle size), also from Waters, was used. The column temperature was maintained at 47 °C. The binary system phases were: A (3% acetonitrile, 2% acetic acid, 95% water) and B (85% acetonitrile, 2% acetic acid, 13% water), with a flow rate of 0.7 mL min1, giving a maximum back pressure of 10,400 psi, which is within the capabilities of the UPLC. The injection volume was 2.5 lL. The 6.5 min gradient was as follows: 0 min 100% A, 3 min 90% A (curve 6), 4 min 90% A, 6.5 min 25% A (curve 6). Finally, the column was washed with 100% B for 3 min and equilibrated with 100% A for 3 min. All the samples were filtered through 0.22 lm nylon filters from Scharlab (Barcelona, Spain). The identification of each compound was carried out by comparing retention times and UV–Vis spectra of the peaks in wine with those previously obtained by the injection of standards. 2.6. Colour Colour measurements were made using a Helios UV–Vis spectrophotometer over the visible range 380–770 nm. Colour analyses were carried out following the method of the CIE (Commission Internationale de l´Eclairage) (C.I.E., 1986). 2.7. Data treatment For each compound or parameter, one-way ANOVA was initially used to determine significant differences between the several groups of samples. A principal component analysis was employed to study the influence of the different parameters which have been studied in ageing. A linear discriminant analysis (LDA) was performed to obtain the equations that would enable a particular sample to be classified according to the age. The Statistica 7.0 program (Tulsa, Oklahoma, USA) was used for all these analyses. 3. Results and discussion 3.1. Evolution of the polyphenols studied Fig. 1 shows the evolution of the different compounds quantified in the samples from the different vintages. As can be observed,
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
273
Fig. 1. Evolution of the different polyphenolic compounds studied.
Fig. 2. Typical Chromatograms of aged Sherry wines, vintage 1935 (A) and vintage 1980 (B). Detection wavelength was set at 280 nm. (1) 5-Hydroxymethylfurfural, (2) protocatechuic acid, (3) furfural, (4) protocatechualdehyde, (5) p-hydroxybenzoic acid, (6) Tyrosol, (7) vanillic acid, (8) p-hydroxybenzaldehyde, (9) syringic acid, (10) vanillin, (11) p-coumaric acid and (12) syringaldehyde.
to stay constant as a consequence of the periodic dilutions of older with younger wine in the transfers between scales, during the samplings (Rodriguez, Guillén, Schwarz, & Barroso, 2010). However, the samples used in the present study have been aged by a static system of ageing; therefore logically, practically all the compounds are expected to show increasing concentration levels in line with the increased length of ageing period. In addition, in the relevant reference studies found, the evolution was monitored over periods of time notably shorter than those considered in the present work. The compounds that are found in higher concentration in the samples aged for longer periods are the furanic aldehydes (hydroxymethylfurfural and furfural), protocatechuic acid, tyrosol, p-coumaric acid and syringaldehyde. The furanic aldehydes, especially hydroxymethylfurfural, are majority compounds in the various different enological products of the zone of Jerez, in wines (García Moreno et al., 2002), brandies (Schwarz, Rodríguez, Martínez, Bosquet, Guillén & Barroso, 2009) and vinegars (Tesfaye et al., 2002). There are two fundamental reasons for the presence of these furanic compounds: the addition of caramel colouring (Quesada, Villalón, Lopez, & López Martinez, 1996) and the ageing in wood (Rodri´guez-Bencomo, Ortega-Heras, Pe´rez-Magarin~o, Gonza´lezHuerta, & Gonza´lez-San Jose´, 2008). However, because the colour of the analysed samples has not been rectified by the addition of caramel, the presence of the furfuraldehydes in our samples must be due to their ageing in wood. Typical chromatograms of aged sherry wines are shown in Fig. 2. As expected, the highest concentration of polyphenols is found in the wine with the longest ageing, whereas the youngest wine has a lower amount of polyphenols.
3.2. Antioxidant activity, index of total polyphenols and SO2 content in general, the concentration of each compound studied tended to be higher in the wines aged for more years. García Moreno et al. (2002) studied the evolution of polyphenols in oloroso, fino and amontillado Sherry wines aged in a dynamic system of Solera and Criaderas. In their investigations in respect of oloroso wine, they observed that the concentration of the benzoic acids was higher in the samples aged for longer periods but that similar increased levels were not observed for the rest of the compounds studied. The difference of behaviour between those samples and the ones of our study is very probably due to the system of ageing. In the dynamic system of solera and criaderas, the concentration of the compounds increases in the initial years of ageing but later tends
If the evolution of the antioxidant activity is observed in relation to the years of ageing, it can be seen that, in general, there is a rising evolution in line with the length of ageing period of the samples, with values ranging from 0.19 mM Trolox for the youngest wine to 5.6 mM Trolox for the oldest one. In addition it can be seen that the oldest samples present an extraordinarily high antioxidant activity. Taking into account that the wines studied are made with white grapes, which have lower polyphenolic content and less antioxidant activity than the black varieties, it can safely be assumed that the high antioxidant activity of these samples is due to the polyphenols that have been contributed during the long
274
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
value of the luminosity parameter L⁄) with an increase of the red and yellow tonalities (larger values of a⁄ and b⁄), with differences in magnitude, which translates to a tone (H⁄) with a greater contribution of red. In Fig. 3, a projection of the CIELab variables a⁄ against b⁄, it is observed that there is a certain ranking in function of the age of the samples. 3.4. Statistical treatment
⁄
⁄
Fig. 3. CIELab colour parameters of aged sherry wines in a b plane.
period of ageing in wood. Therefore the degree of antioxidant activity is clearly related to the length of ageing in wood. The index of total polyphenols and the antioxidant activity were measured for all the samples, and a good relationship, r2 = 0.8416, has been found. Thus the strong influence of the polyphenols on the antioxidant activity is confirmed. However, as stated by other authors (Alonso et al., 2004), not all polyphenols have the same influence on the antioxidant activity; for this reason it is important to study the relationship between the individual polyphenols studied and the antioxidant activity measured in the samples. Protocatechuic acid, protocatechuic aldehyde, syringic acid, vanillin and p-coumaric acid are the compounds that show the closest correlations (r2 > 0.7). These results appear to be consonant with those reported by Alonso et al. (2004), who also obtained a good correlation for these same compounds (except protocatechuic aldehyde) in Sherry wine vinegars aged in wood. The possible correlation between antioxidant activity and SO2 content was then assessed. The SO2 concentrations which were obtained for this group of wines varied between 8 and 17 mg L1. When it was correlated with the antioxidant activity, an r2 of 0.23 was obtained, which shows that the influence of SO2 in the antioxidant activity is not significant in this case.
3.3. Colour In accordance with the values of the chromatic parameters, the samples aged for longer periods present a darker colour (a lower
Taking into account the vintage, the aged samples were grouped in seven different sets, in function of the decade in which the ageing of the samples was initiated. A statistical study was made of all the samples analysed. First, an analysis of the variance was performed to investigate the possibility of differentiating the various groups pre-established, based on these compounds. All the variables presented statistically significant differences between the seven groups of samples (p < 0.05). However, on performing the post hoc (Bonferroni) comparisons, it was found that none of the compounds allowed the discrimination between the seven groups; therefore it was decided to apply multivariate analysis to all the samples using linear discriminant analysis (LDA). The concentrations of the polyphenols and furanic aldehydes were expressed in mg L1. On applying the LDA to the set of samples, the equations are obtained that allow an unknown sample to be classified to one of the groups previously defined according to its mean time of ageing. Thus, Table 1 presents the functions of classification that would make possible the assignment of age. The most discriminant, participating variables were: antioxidant activity, total phenolic content, protocatechuic aldehyde, protocatechuic acid, p-hydroxybenzoic acid, p-hydroxybenzaldehyde and hydroxymethylfurfural. A classification of 100% was obtained as can be observed in Fig. 4a, in which a certain ranking of the samples according to their age by component 2 is observed. In this component the variables that obtained a greater weight were syringic acid, syringaldehyde, vanillic acid, p-coumaric acid, p-hydroxybenzoic acid and the index of total polyphenols; all of these parameters are directly correlated with the length of ageing in wood, which would explain this ranking. A principal component analysis was employed to study the influence of the variables in the ageing of the samples. The first
Table 1 Classification functions.
TPI p-Hydroxybenzoic acid Protocatechuicaldehyde 5-Hydrox ymethylfurfural b⁄ Antioxidant activity Syringaldehyde p-Hydroxybenzaldehyde Protocatechuic acid Syringic acid L⁄ Furfural C⁄ H⁄ p-Coumaric acid Vanillic acid Constant
Samples from 1935 to 1940
Samples from 1941 to 1950
Samples from 1951 to 1960
Samples from 1961 to 1970
Samples from 1971 to 1980
Samples from 1981 to 1990
Samples from 1991 to 1999
18 9951 14,630 287
21 11,261 16,479 329
20 10,733 15,757 314
20 10,852 15,931 317
19 10,337 15,215 301
20 10,728 15,797 314
20 10,665 15,672 314
1277 19,836 1512 16.86 31.61 28.81 1284 23 424 1829 3985 1748 1343.53
1437 22,546 1733 34.73 37.98 35.89 1465 0 478 2062 4413 1931 1740.46
1403 21,545 1655 27.75 36.73 34.61 1401 0 457 2002 4230 1845 1613.32
1404 21,759 1668 23.52 33.97 31.60 1413 4 463 2009 4284 1872 1402.12
1354 20,737 1589 21.99 34.86 32.24 1341 5 442 1931 4105 1792 1462.90
1416 21,586 1657 24.15 36.55 34.33 1398 3 459 2017 4241 1850 1589.69
1430 21,489 1656 33.22 38.07 37.34 1400 9 456 2030 4198 1822 1665.84
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
275
Fig. 4. Statistical treatment. (a) Distribution in the canonical space derived from the LDA for the aged wines elaborated in different decades. (b) PCA performed on the following parameters: colour, antioxidant activity, low molecular weight phenolics, TPI and SO2 content. Scatterplot of the samples onto the plane defined by the first two principals components extracted.
Table 2 Factor loadings of the two first principal components extracted. Variable
CP1
CP2
Hydroxymethylfurfural Protocatechuic acid Furfural Protocatechualdehyde p-Hydroxybenzoic acid Tyrosol Vanillic acid p-Hydroxybenzaldehyde Syringic acid Vanillin p-Coumaric Syringaldehyde L⁄ a⁄ b⁄ H⁄ C⁄ Antioxidant activity TPI SO2
0.569 0.941 0.729 0.919 0.943 0.953 0.898 0.942 0.933 0.962 0.961 0.908 0.929 0.956 0.769 0.961 0.842 0.901 0.862 0.569
0.545 0.192 0.010 0.077 0.013 0.109 0.257 0.044 0.297 0.152 0.071 0.241 0.093 0.095 0.449 0.104 0.387 0.082 0.161 0.581
three principal components explain 89.61% of the total variance, although the first component, which alone explains 77.75%, contributes most. As can be observed in Fig. 4b, the samples are ordered along component one, being the most aged ones to the left and the least aged ones to the right, being possible, as a result, to relate component 1 with ageing. If we observe the weight of the variables (Table 2), we can see that most of them are related to such component, confirming the relationship of the studied variables with the ageing of the samples. Further, it is seen that hydroxymethylfurfural and SO2 are more weakly associated with component 1. 4. Conclusions Considering the aforementioned results, it can be concluded that the antioxidant activity of the old wines studied is a parameter clearly related to the ageing of the wine in cask, and to the polyphenols contributed by the wood during this period. Among the polyphenolic compounds studied, those that presented better correlation with antioxidant activity were protocatechuic acid, protocatechuic aldehyde and syringic acid. The wines also showed differences in their chromatic characteristics according to the
duration of ageing in years. The close relationship of the studied parameters with the ageing of the wines has been confirmed by the principal components analysis which has been carried out to the samples. Further, a linear discriminating analysis was successfully used to obtain a statistical model that allowed samples to be well discriminated in function of the length of their ageing. Acknowledgements The authors are most grateful to Bodegas Williams & Humbert for providing the samples. This study has been financed by Project P05-AGR-00767. References Alonso, Á. M., Castro, R., Rodríguez, M. C., Guillén, D. A., & Barroso, C. G. (2004). Study of the antioxidant power of brandies and vinegars derived from Sherry wines and correlation with their content in polyphenols. Food Research International, 37, 715–721. Alonso, A. M., Guillen, D., & Barroso, C. G. (2003). Development of an electrochemical method for the determination of antioxidant activity. Application to grapederived products. European Food Research and Technology, 216, 445–448. Alonso, A. M., Guillén, D. A., Barroso, C. G., Puertas, B., & García, A. (2002). Determination of antioxidant activity of wine byproducts and its correlation with polyphenolic content. Journal of Agricultural and Food Chemistry, 50, 5832–5836. Bosso, A., Guaita, M., Panero, L., Borsa, D., & Follis, R. (2009). Influence of two winemaking techniques on polyphenolic composition and color of wines. American Journal of Enology and Viticulture, 60, 379–385. C.I.E. (1986). Colorimetry, 2nd ed. Publication C.I.E. No.15.2, Central Bureau of the Commission Internationale de L’Eclairage, Vienna. Cadahía, E., Muñoz, L., De Simón, B. F., & García-Vallejo, M. C. (2001). Changes in low molecular weight phenolic compounds in Spanish, French, and American oak woods during natural seasoning and toasting. Journal of Agricultural and Food Chemistry, 49, 1790–1798. Cerezo, A. B., Tesfaye, W., Soria-Diaz, M. E., Torija, M. J., Mateo, E., García-Parrilla, M. C., & Troncoso, A. M. (2010). Effect of wood on the phenolic profile and sensory properties of wine vinegars during ageing. Journal of Food Composition and Analysis, 23, 175–184. De Quirós, A. R.-B., Lage-Yusty, M. A., & López-Hernández, J. (2009). HPLC-analysis of polyphenolic compounds in Spanish white wines and determination of their antioxidant activity by radical scavenging assay. Food Research International, 42, 1018–1022. Del Álamo, M., Nevares, I., Gallego, L., Martin, C., & Merino, S. (2008). Aging markers from bottled red wine aged with chips, staves and barrels. Analytica Chimica Acta, 621, 86–99. Del Alamo Sanza, M., Escudero, J. A. F., & De Castro Tori´o, R. (2004). Changes in phenolic compounds and colour parameters of red wine aged with oak chips and in oak barrels. Food Science and Technology International, 10, 233–241. Ferna´ndez-Pacho´n, M. S., Villaño, D., Troncoso, A. M., & Garci´a-Parrilla, M. C. (2006). Determination of the phenolic composition of sherry and table white wines by liquid chromatography and their relation with antioxidant activity. Analytica Chimica Acta, 563, 101–108.
276
M. Schwarz et al. / Food Chemistry 133 (2012) 271–276
Frangipane, M. T., Santis, D. D., & Ceccarelli, A. (2007). Influence of oak woods of different geographical origins on quality of wines aged in barriques and using oak chips. Food Chemistry, 103, 46–54. Frankel, E. N., Waterhouse, A. L., & Teissedre, P. L. (1995). Principal phenolic phytochemicals in selected California wines and their antioxidant activity in inhibiting oxidation of human low-density lipoproteins. Journal of Agricultural and Food Chemistry, 43, 890–894. García Moreno, M. V., & Garcia Barroso, C. (2002). Comparison of the evolution of low molecular weight phenolic compounds in typical Sherry wines: Fino, amontillado, and oloroso. Journal of Agricultural and Food Chemistry, 50, 7556–7563. Garci´a-Puente Rivas, E., Alcalde-Eon, C., Santos-Buelga, C., Rivas-Gonzalo, J. C., & Escribano-Bailo´n, M. T. (2006). Behaviour and characterisation of the colour during red wine making and maturation. Analytica Chimica Acta, 563, 215–222. Herna´ndez, T., Estrella, I., Duen~as, M., De Simo´n, B. F., & Cadahi´a, E. (2007). Influence of wood origin in the polyphenolic composition of a Spanish red wine aging in bottle, after storage in barrels of Spanish, French and American oak wood. European Food Research and Technology, 224, 695–705. Organisation International de la Vigne et du Vin (2009). Compendium of international methods of wine and must analysis (Vols. I and II), Paris. Ortega, T., De La Hera, E., Carretero, M. E., Gómez-Serranillos, P., Naval, M. V., Villar, A. M., Prodanov, M., Vacas, V. B., Arroyo, T., Hernández, T., & Estrella, I. (2008). Influence of grape varieties and their phenolic composition on vasorelaxing activity of young red wines. European Food Research and Technology, 227, 1641–1650. Paixão, N., Perestrelo, R., Marques, J. C., & Câmara, J. S. (2007). Relationship between antioxidant capacity and total phenolic content of red, rosé and white wines. Food Chemistry, 105, 204–214. Quesada, Granados. J., Villalón, Mir. M., Lopez, Serrana. H., & López Martinez, M. C. (1996). The influence of added caramel on furanic aldehyde content of matured brandies. Food Chemistry, 56, 415–419.
Recamales, A. F., Hernanz, D., Álvarez, C., González-Miret, M. L., & Heredia, F. (2007). Colour of Amontillado wines aged in two oak barrel types. Journal of European Food Research and Technology, 224, 321–327. Rodriguez, M. C., Guillén, D., Schwarz, M., & Barroso, C. G. (2010). Phenolic compounds and furanic derivatives in the characterization and quality control of Brandy de Jerez. Journal of Agricultural and Food Chemistry, 58, 990–997. Rodri´guez-Bencomo, J. J., Ortega-Heras, M., Pe´rez-Magarin~o, S., Gonza´lez-Huerta, C., & Gonza´lez-San Jose´, M. L. (2008). Importance of chip selection and elaboration process on the aromatic composition of finished wines. Journal of Agricultural and Food Chemistry, 56, 5102–5111. Satue´-Gracia, M. T., Andre´s-Lacueva, C., Lamuela-Ravento´s, R. M., & Frankel, E. N. (1999). Spanish sparkling wines (Cavas) as inhibitors of in vitro human lowdensity lipoprotein oxidation. Journal of Agricultural and Food Chemistry, 47, 2198–2202. Schwarz, M., Rodríguez, M. C., Guillén, D. A., & Barroso, C. G. (2009). Development and validation of UPLC for the determination of phenolic compounds and furanic derivatives in Brandy de Jerez. Journal of Separation Science, 32, 1782–1790. Schwarz, M., Rodríguez, M., Martínez, C., Bosquet, V., Guillén, D., & Barroso, C. G. (2009). Antioxidant activity of Brandy de Jerez and other aged distillates, and correlation with their polyphenolic content. Food Chemistry, 116, 29–33. Singleton, V. L., & Rossi, Joseph. A. (1965). Colorimetry of total phenolics with phosphomolybdic–phosphotungstic acid reagents. American Journal of Enology and Viticulture, 16, 144–158. Tesfaye, W., Morales, M. L., Garci´a-Parrilla, M. C., & Troncoso, A. M. (2002). Evolution of phenolic compounds during an experimental aging in wood of Sherry vinegar. Journal of Agricultural and Food Chemistry, 50, 7053–7061.
