Improving the Color and Aging Aptitude of Syrah Wines in Warm Climate by Wood–grape Mix Maceration

Depósito de investigación de la Universidad de Sevilla https://idus.us.es/ “This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s00217-016-2767-0” 1 Improving the color and aging aptitude of Syrah wines in warm climate by woodgrape mix maceration María Jesús Cejudo-Bastante, Francisco J. Rivero-Granados, Francisco J. Heredia* Food Colour and Quality Laboratory, Dept. Nutrition and Food Science, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain María Jesús Cejudo-Bastante: [email protected] Francisco J. Rivero-Granados: [email protected] Francisco J. Heredia: [email protected] * Corresponding author: Francisco J. Heredia Food Colour & Quality Laboratory, Dept. Nutrition & Food Science. Facultad de Farmacia. Universidad de Sevilla. 41012-Sevilla, Spain Tel.: +34 954556495 Fax: +34 954556110 e-mail: [email protected] 2 ABSTRACT The amelioration of aging aptitude of Syrah red wines from warm climate regions by adding oak wood chips to the grape maceration/fermentation has been developed. Our attention was focused on the tristimulus colorimetry, differential colorimetry and phenolic composition. This technique was applied with an eye toward improving color stabilization of wines in a warm climate region where common loss of color normally occurs. On the basis of the results, a color enhancement (by an increment of chroma, C*ab) and significant (p < 0.05) higher amounts of total polyphenols, anthocyanins, flavan-3-ols and esters of hydroxycinnamic acids was observed in Syrah red wines, favoring a significantly (p < 0.05) higher percentage of copigmentation and, hence, color stabilization. Finally, it could be affirmed that the joint addition of oak wood chips (both during fermentation and aging) induced visually perceptible color differences (ΔE*ab > 3), mainly quantitative (Δ2L*ab and Δ2C*ab), from the early months of storage. KEYWORDS American oak wood chips, polyphenolic compounds, CIELAB, differential colorimetry, aging, warm climate. 3 INTRODUCTION Obtaining high quality red wines in warm climate regions is difficult because of the usual color instability over time due to the high temperatures. This fact is produced because both phenolic and technologic maturities do not coincide at the moment of harvesting as occurred in colder viniculture zones [1]. As a consequence, seeds remain unripen and the low quantities of pigments and copigments occurred [2], hampering copigmentation phenomena (which contribute to color stabilization). As a result, it is common to notice a fall of color after some months of storage in either bottle or barrels, showing difficulties of ageing the red wines elaborated in warm climate regions. In the search for color stabilization, phenolic compounds are the main contributors of the quality of the wines, taking into account the color and astringency. Phenolic compounds such as anthocyanins (mainly in skins) were not only the responsible for the final color of wines, but flavonols, flavan-3-ols and other compounds (normally colorless) act as copigments, improving the color stabilization of aged wines by means of copigmentation reactions [3]. Whereas some other reactions involving anthocyanins could produce loss of color (oxidation, hydration or adsorption), the formation of polymeric pigments take importance and contribute to the stabilization of the wines [4]. With the objective of increasing the quantities of pigment concentrations (tending to reach an optimal color stabilization), implementation with tannins have been recently developed in warm climate, both derived from grape and wood. That is the case of Gordillo et al. [5], who studied the stabilization of the color by adding Pedro Ximenez white pomace to Spanish Syrah red wines during fermentation, or Baiano et al. [6] in a study about the addition of French oak wood chips to two Italian grape varieties (Montepulciano and Aglianico), or the research of a native Greek variety (Agiorgitiko) by using oak chips from different sources [7]. However, despite of this practice, color 4 losses normally occurred after a short period of time in warm climate winemaking, so researches looking for new alternatives are of particular interest. These evidences led us to think that, probably, the implement with tannins would be carried out at the initial points of the vinification, in order to assure sufficient tannin concentration during vinification. Thus, in that sense, our research group studied the addition of oak wood chips during fermentation of red grapes [8], obtaining positive results in terms of color stabilization. However, it could be hesitated if wines elaborated in that way could be appropriate for long-lasting aging. Thus, this research work sought to scrutinize the capacity of aging of Syrah wines, the more cultivated grape variety in D.O. Condado de Huelva (southwestern of Spain) and normally employed to elaborate young wine. To date, this research study is the first attempt to deeply scrutinize the effect of aging wines with an implement with tannins (by the addition of oak wood chips) in the early stages of vinification in warm climate regions. Our interest was focused on the study of phenolic composition (anthocyanins, benzoic acids, hydroxycinnamic acid derivatives, flavan-3-ols and flavonols), chromatic characteristics by applying differential colorimetry, copigmentation and polymerization. MATERIAL AND METHODS Winemaking Around 600 Kg of Vitis vinifera Syrah grapes were harvested in “Condado de Huelva” Designation of Origin, in the southwestern Spain, in a good maturity (12.4 ºBrix). After destemming and crushing, the must were distributed in three stainless steel tanks of 220 L for skin maceration. 3 g/L of American oak (Quercus alba) wood low-toasted chips of 1 cm2 average size (Tonelería Martín y Vázquez, Logroño, Spain) were added to the must, together with skins. Fermentation caps were punched down at each tank once a day during the on-skin maceration period, which lasted four days (fermentative 5 alcoholic fermentation). Alcoholic fermentation, and the subsequent malolactic fermentation, were correctly and spontaneous developed, guided by assays of density and enzymatic measurements of malic and lactic acid contents, respectively. Then, wines were racked to stainsteel tanks of 50 L and were kept for stabilization. After around four months (130 days), wines were racked again. Subsequently, two types of experiences were carried out: (i) three tanks were submitted to the additional treatment with 3 g/L of American oak wood medium-toasted chips during 40 days (CCp), and (ii) other three tanks contained wine with the only addition of oak wood chips during fermentation (C). Experiments were carried out in triplicate. Oenological parameters The official methods established by European Union were used to obtained the conventional oenological parameters such as pH, total and volatile acidity, reducing sugars, and free and total SO2 [9]. Spectrophotometric color measurement A Hewlett-Packard UV-vis HP8452 spectrophotometers (Palo Alto, CA) was used to determine the whole visible spectrum (380-770 nm) at constant intervals (Δλ=2 nm), using 2 mm path length glass cells and distilled water as reference. The CIELAB color parameters (L*, a*, b*, C*ab, and hab) were determined by using the original software CromaLab© [10], following the Commission Internationale de L’Eclariage’s, CIE, recommendations [11]: the CIE 1964 10° Standard Observer and the CIE Standard Illuminant D65. The L* value (vertical axis) defines the lightness (property according to which each color can be considered as equivalent to a member of the gray scale, between black and white, with values ranging between 0 and 100, respectively). The parameters a* and b* are the colorimetric coordinates, which represent opponent redgreen and blue-yellow axes. The parameters hue (hab) and chroma (C*ab) are defined 6 from L*, a* and b*. Hue angle (hab) is the attribute according to which colors have been traditionally defined as red, yellow, etc. Besides, the chroma (C*ab) allows each hue to be determined by its degree of difference in comparison to a gray color with the same lightness. Moreover, these colorimetric parameters indicate a quantitative (L* and C*ab) or qualitative (hab) contribution to color [12]. Euclidean distance between two points in the three-dimensional space define by L*, a*, and b* were used for calculating color differences (ΔE*ab): ΔE*ab = [(ΔL*)2 + (Δa*)2 + (Δb*)2]1/2. Previous adjustment to pH 3.6 using 1 M NaOH and HCl, the percentage contributions of copigmented anthocyanins (% copigmented pigments) to the total wine color and the degree of anthocyanin polymerization (% polymeric pigments) were determined [13]. Folin-Ciocalteau reagent was used for the analysis of total phenolics [14]. HPLC-DAD analysis of phenolic compounds in wines An Agilent 1200 chromatographic system, equipped with a quaternary pump, and UV- vis diode-array detector, an automatic injector, and ChemStation software (Palo Alto, CA), was used to the HPLC separation, identification and quantification of phenolic compounds. Prior direct injection, the samples were filtered through a 0.45 μm Nylon filter (E0034, Análisis Vínicos, Tomelloso, Spain). All analyses were made in triplicate. The method proposed by Heredia et al. [15] was used for the anthocyanin identification. Acetonitrile-formic acid-water (3:10:87) as solvent A and acetonitrile-formic acid-water (50:10:40) as solvent B were used. The elution profile was as follows: 0-10 min 94% A - 6% B; 10-15 min 70% A - 30% B; 15-25 min 60% A – 40% B; 25-35 min 55% A - 45% B; 35-40 min 50% A - 50% B; 40-42 min 40% A - 60% B; 42-43 min 94% A - 6% B. The flow rate was 0.8 mL/min, and the injection volume was 50 μl. A reversed-phase column Zorbax C18 (250 x 4.6 mm, 5 μm particle size), thermostatted at 38 ºC, were used. UV-Vis spectra were recorded from 200 to 800 nm with a bandwidth of 2.0 nm. 7 The quantification was made at 525 nm by comparing the areas and the retention times with the malvidin 3-glucoside standard. For the identification of the phenolic compounds (flavan-3-ols, flavonols, hydroxycinnamic acid derivatives and other low molecular weight phenolic compounds), the method developed by Gordillo et al. [8] was used. A volume of 50 μl was injected in triplicate onto a Zorbax C18 column (250 x 4.6mm, 5 μm particle size), maintained at 40 ºC, with a flow rate of 0.63 mL/min. Acetonitrile-formic acid-water (3:10:87) as solvent A and acetonitrile-formic acid-water (50:10:40) as solvent B were used. The elution profile was as follows: 0 min 94% A - 6% B; 5 min 89% A - 11% B; 10 min 89% A - 11% B; 15 min 80% A - 20% B; 20 min 77% A - 23% B; 25 min 74% A - 26% B; 30 min 60% A - 40% B; 35 min 50% A - 50% B; 38 min 40% A - 60% B; 46 min 94% A - 6% B. UV-Vis spectra were recorded from 200 to 800 nm with a bandwidth of 2.0 nm. The quantification was made at 280, 320 and 360 nm by comparing the areas and the retention times with the gallic acid, caffeic acid, and quercetin standards, respectively. Total anthocyanins, flavonols and flavan-3-ols were calculated as sum of individual phenolic compounds identified by HPLC. Statistical Analysis All statistical analyses were performed using Statistica v.8.0 software [16]. Univariate analysis of variance (ANOVA) was applied using the general linear model program to establish whether mean values of the sample data differed significantly each other. The means values of each set of samples (n = 3) were compared by the Tukey test at a significance level of p < 0.05. Moreover, multivariate analysis of data (linear discriminant analysis, LDA) was performed in order to classify wine samples according to phenolic compounds and color parameters. This method was applied to the set of data 8 consisting of 70 rows (wine samples) and 28 columns (individual phenolic compounds and colorimetric variables). RESULTS AND DISCUSSION Climate conditions The “Condado de Huelva” Designation of Origin is a typical warm climate region. According to the Köppen climatic classification [17], the southwestern of Spain has a “Csa” assignation, according to the classification of the main climates and precipitation and temperature conditions. Thus, “C” refers to “warm temperature”, “s” to “summer dry” and “a” to “hot summer”, respectively. Fig. 1 shows the maximum, minimum and average temperature, relative humidity and rainfall of the summer (from 21st June to 21st September) of the area of “Condado de Huelva” Designation of Origin recorded for the last ten years. On the one hand, the values of temperature and relative humidity was almost constant over the last ten years. The average temperature was around 25 ºC, although it ranged between 14 and 41 ºC. Moreover, relative humidity ranged between 8 and 97 %, establishing around 50 % the medium value. Although some high peaks of rainfall were registered depending on the year, the average rainfall was established under 1 mm/day. These data have been provided by Instituto de Investigación y Formación Agraria y Pesquera (IFAPA), Junta de Andalucía, Spain. Enological parameters The results of analytical parameters of Syrah red wines revealed the correct development of the alcoholic fermentation (reducing sugars < 2.0 g/L), considering them as dry wines. pH values and total acidity were similar (around 3.4 units and 5.0 as tartaric acid, respectively) and volatile acidity values were below the limit established 15 to the evaluation of the chromatic quality of Tempranillo red wines elaborated in warm climate. Influence of the presence of oak wood chips during fermentation. Food Chem 141:2184-2190 9. UE (2003) Official Methods to Wine Analyses, Reglamento 440/2003 10. Heredia FJ, Álvarez C, González-Miret ML, Ramírez A (2004) CromaLab, Análisis de Color. Registro General de la Propiedad Intelectual 11. CIE (2004) Technical Report Colorimetry. Vienna, Austria, Commission Internationale de l'Eclairage Central Bureau 12. 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Santos-Buelga C, Bravo-Haro S, Rivas-Gonzalo JC (1995) Interactions between catechin and malvidin-3-monoglucoside in model solutions. Eur Food Res Technol 201:269-274 30. Martínez JA, Melgosa M, Pérez MM, Hita E, Negueruela AI (2001) Note. Visual and instrumental color evaluation in red wines. Food Sci Technol Internat 7:439- 444 18 FIGURE CAPTIONS Fig. 1. Maximum (max), minimum (min) and average (averg) temperature (A), relative humidity (RH, B) and rainfall (RF, C) of the summers of the area of “Condado de Huelva” Designation of Origin recorded for the last ten years. Fig. 2. Total polyphenols content (mg/L) evolution during vinification of Syrah red wines with the addition of oak wood chips during fermentation (C) and with the additional aging with oak wood chips (CCp). For each day, asterisks denote significant differences according to Tukey test (p < 0.05) between both kind of wines. Fig. 3. Evolution of CIELAB parameters (L* (A), C*ab (B) and hab (C)) during vinification of Syrah red wines with the addition of oak wood chips during fermentation (C) and with the additional aging with oak wood chips (CCp). For each day, asterisks denote significant differences according to Tukey test (p < 0.05) between both kind of wines. Fig. 4. Scatterplot of the canonical variate obtained by LDA: Syrah red wines with the addition of oak wood chips during fermentation (C) and with the additional aging with oak wood chips (CCp).