Aroma Enhancement of La Mancha White Wines Using Coupage Technique

Abstract

Volatile compounds and aroma sensory profile of wines were researched in order to determine the effect of the coupage technique using monovarietal young white wines from La Mancha region. To conduct this study, the aroma compositions of Airén, Chardonnay, and Vermentino monovarietal wines and the wines obtained by blending monovarietal wines were extensively studied. Free aroma compounds were isolated by solid phase extraction (SPE) using dichloromethane and then analyzed by gas chromatography–mass spectrometry (GC-MS). Sensory aroma profile was determined using Quantitative Descriptive Sensory Analysis (QDA). Seventy-one (71) free aroma compounds were identified and quantified. C₆ and benzenic compounds were the principal groups of varietal aroma compounds in Airén and Chardonnay wines. The varietal aroma of monovarietal Vermentino wines is characterized by higher concentrations of terpene and C₁₃-norisoprenoids compounds. Wines obtained by the blending of monovarietal wines showed a higher concentration of principal aroma compounds of monovarietal wines and exhibited a higher sensory complexity than the monovarietal wines. The coupage technique intensified the principal sensory properties of Airén, Chardonnay, and Vermentino monovarietal wines and these were scored very positively by wine assessors, especially when the different grape variety contents of the blended monovarietal wines were split equally at 33% each, which provided wines with more aroma typicity than monovarietal wines.

1. Introduction

The wine industry is undergoing a continuous evolution driven by increasing consumer demand for high-quality wines that accurately reflect the aromatic typicity of the grape varieties used in their production [1]. In addition to traditional expectations, modern consumers seek wines with more complex and innovative aromatic profiles, surpassing those obtained through conventional vinification methods and the widely used grape varieties [1,2]. This growing preference has fostered advancements in oenological practices and grape selection, encouraging winemakers to explore novel techniques [3,4] and varieties to enhance their sensory diversity and appeal.

Wine is a complex oenological matrix with multiple sensory attributes that significantly influence consumer perceptions [5]. Sensory attributes such as visual appearance, aromatic profile, flavor complexity, astringency, body, mouthfeel, and aftertaste intensity influence the perceived quality and consumer acceptance of wine [6,7,8]. However, owing to the inherent variability in grape composition and winemaking processes, single-varietal wines do not always achieve optimal sensory balance. Consequently, the blend of different grape varieties or wines has emerged as a critical strategy in enology [9].

Blending can be implemented through co-fermentation, which involves the simultaneous fermentation of multiple grape varieties, or through the post-fermentation mixing of monovarietal wines, known as coupage or assemblage. Although there is no fixed stage in the winemaking process for blending, monovarietal wines are commonly combined after alcoholic fermentation [10]. Despite research on blending beginning in the 1960s [11], this technique remains under-explored [12,13].

From an enological perspective, blending enables winemakers to refine their wine’s aromatic and flavor attributes, mitigate sensory imbalances, and achieve a cohesive stylistic profile. Moreover, strategic blending offers economic advantages by optimizing grape variety utilization and reducing production costs [12]. This manipulation significantly influences sensory properties and aromatic complexity, ultimately shaping the final profile of wine [14].

One of the most widely adopted practices to address market demand is the production of “coupages,” wherein monovarietal wines are blended to enhance complexity and quality. The term “coupage”, derived from French, refers to the art of combining wines to harmonize, refine, or amplify their attributes. The practice of blending wines with different compositional profiles permits the modification of the principal components of wines such as free and bound volatile compounds, phenolic compounds, sugars, and acids, and can influence sensory characteristics. A pioneering study on wine blending was conducted by Singleton and Ough in 1962 [11] in which they evaluated the sensory quality of 34 wine blends composed in equal parts (50:50) and compared them to their original, unblended counterparts. The results indicated that seven of the blends received higher quality ratings than either of their individual components, while none of the blends were rated lower than the least favorable of the original wines. Despite the growing interest in wine innovation, recent years have seen limited research focused on blending techniques and varietal combinations. Nevertheless, some studies have shown that blended wines tend to achieve a more harmonious balance between anthocyanins and flavanols compared to single-varietal wines, which contributes to enhanced flavor complexity and greater color stability [14,15,16,17].

Most studies on wine blending (coupage) have primarily focused on its impact on color and phenolic composition, while relatively few have explored its influence on the aromatic profile of white wines, highlighting the need for further research in this area. Vilanova and Freire [18] have demonstrated the effects of blending on the volatiles of Albariño and Loureira wines. Wines obtained from blending led to changes in volatile composition, increasing the content of some volatile compounds. Through blending, the specific properties of wines may be modified, contributing to unique and distinct sensory profiles [19].

Therefore, in order to meet with consumer demand, there is a requirement to diversify and improve the quality of produced white wines; consequently, there is a need to study the potential of use of wines from different grape varieties as blending partners in white wine production. For this aim, it is necessary to confirm that the obtained blends will enable the production of new original and high-quality white wines while being highly competitive on the national and international wine market [20,21,22]. In this sense, the purpose of this study was to determine how blending affects the volatile composition and sensory characteristics of Chardonnay, Airén, and Vermentino white wines. The use of two grape varieties traditionally cultivated in La Mancha region—Airén and Chardonnay—was proposed alongside Vermentino, a minority variety in this area that has successfully adapted to the region’s extreme climatic conditions. Monovarietal wines were produced for each variety, as well as blended wines (coupages) in different proportions, with the aim of achieving greater aromatic complexity.

2. Materials and Methods

2.1. Chemicals and Standards

Merck (Darmstadt, Germany) provided the dichloromethane, ethanol, and methanol and Panreac (Barcelona, Spain) provided anhydrous sodium sulfate. A Milli-Q purification system by Millipore (Bedford, VA, USA) was used in order to obtain ultrapure water, with a conductivity of 0.000006 S/m. LiChrolut EN resins were supplied by Merck (Darmstadt, Germany).

In order to determine the linear retention index (RI) of volatile compounds, a solution of alkane compounds in dichloromethane (C₇–C₂₄, Supelco, PA, USA) was used. Pure standards were acquired from Sigma-Aldrich (Madrid, Spain), Merck (Darmstadt, Germany), Fluka (Madrid, Spain), Lancaster (Strasbourg, France), and Firmenich (Geneva, Switzerland). This information is shown in Table S1.

2.2. Samples

White grapes of Vitis vinifera from the varieties Airén, Chardonnay, and Vermentino, cultivated in an experimental vineyard, were manually harvested (approximately 400 kg of each grape variety) at their optimal maturity (20–22° Brix) and in perfect sanitary conditions. This experimental vineyard was situated in the Regional Institute of Agri-Food and Forestry Research and Development of Castilla–La Mancha (IRIAF), in Tomelloso, Spain (latitude 39°10′34″ N, longitude 3°00′01″ W; altitude 660 m.a.s.l.).

The wines were produced following a standard white winemaking protocol, using 100 L stainless steel tanks housed in the experimental cellar of the Castilla–La Mancha Vine and Wine Institute (IVICAM). The grapes were destemmed and crushed, after which 100 mg/L of SO₂ (Panreac, Barcelona, Spain) was added. Fermentations were carried out at a controlled temperature of 24 °C using Saccharomyces cerevisiae (Uvaferm VN^®) at a rate of 20 g per 100 kg of crushed grape. All fermentations were carried out in duplicate. The wines were produced with the following blends of the single-varietal wines: 100% Chardonnay, 100% Airén, 100% Vermentino, 50% Chardonnay + 50% Airén, 50% Airén + 50% Vermentino, 50% Chardonnay + 50% Vermentino, and 33% Chardonnay + 33% Airén + 33% Vermentino. The coupage of each wine was made in duplicate using the wines obtained by each fermentation replicate.

2.3. Conventional Analysis

The conventional analyses of studied wines, pH, total acidity, volatile acidity, and ethanol were carried out according to the methods proposed by the International Organisation de la Vigne et du Vin in 2022 [23]. All samples were analyzed in duplicate.

2.4. Volatile Composition of Wines

The identification of minor volatile compounds in the analyzed wines was conducted using a gas chromatograph (Agilent 6890N) coupled with a Mass Selective Detector (5973 inert Agilent Technologies, Palo Alto, CA, USA) and equipped with a BP-21 capillary column (60 m × 0.25 mm internal diameter; 0.25 µm film thickness).

Isolation of volatile compounds: Wine samples (100 mL), containing 40 µL of the internal standard (4-nonanol at 1.04 g/L), were processed through solid-phase extraction (SPE) cartridges (500 mg LiChrolut EN resins) provided by Merck, with a flow rate of 1 mL/min [24]. Elution of the volatile compounds was performed with 10 mL of dichloromethane, and the resulting organic extract was concentrated under a nitrogen stream to reach a final volume of 200 µL.

Analysis of volatile compounds: A 1 µL extract was injected at 250 °C in splitless mode, using helium as the carrier gas at a flow rate of 1 mL/min. The temperature program for the oven started at 70 °C (held for 5 min), then rose at 1 °C/min to 95 °C (held for 10 min), followed by an increase to 200 °C at 2 °C/min, which was then held for 40 min. The mass spectrometer operated in electron impact mode at 70 eV, with full-scan data acquisition across a mass range of 40–450 m/z and an ion source temperature of 280 °C.

Identification and quantification of volatile compounds: Volatile compound identification was based on comparisons between experimental mass spectra and those of authentic standards, as well as library data (NBS75K). The linear retention index (LRI) was calculated for confirmation purposes using retention times from a mixture of straight-chain alkanes (C₇–C₂₄) analyzed under identical chromatographic conditions. Quantification of volatile compounds was achieved through calibration curves constructed from reference standards at twelve concentration levels in a model wine matrix (12% ethanol, 5 g/L tartaric acid, pH 3.5). For compounds without authentic standards, concentrations were estimated by comparing GC-MS signal intensities with the internal standard signal, applying relative response factors. All measurements were performed in duplicate at the time of bottling.

2.5. Descriptive Sensory Analysis

The sensory analysis conducted in this study involved voluntary participation in a non-invasive wine tasting session. No personal data or biological samples were collected, and participants were not exposed to any physical or psychological risk. In accordance with Spanish legislation (Ley 14/2007, de Investigación Biomédica), ethical approval is required for biomedical research involving interventions on human beings or the use of biological samples. As our study does not fall under these categories, formal approval from an ethics committee was not required. Additionally, as the University of Castilla–La Mancha do not have a research ethics committee for sensory analysis involving humans or a formal documentation process, panelists were selected from the community of this institution. All participants were informed about the nature of the study, gave their verbal consent prior to participation; the study was conducted in accordance with ethical standards and the rights and privacy of all participants were protected.

Monovarietal and blending white wines were evaluated in duplicate by a panel of 10 trainers assessors (5 female and 5 male) with ages ranging from 30 to 55 years using Quantitative Descriptive Sensory Analysis (QDA). Assessment took place in a standard sensory analysis chamber (UNE-EN ISO 8589:2010) [25] equipped with separate booths. Wine samples (30 mL) were presented in coded standard wine testing glasses (ISO 3591, 1997) [26] covered with a watch glass to minimize the escape of volatile components at 10 °C for the detection of odor and aroma sensory attributes. In order to quantify the intensity of each attribute, the assessors used a non-structured scale of 10 cm where the left-hand end of the scale was “not perceptible” and the right-hand end was “strongly perceptible”.

2.6. Statistical Analysis

The impact of the elaboration technique was assessed through one-way analysis of variance (ANOVA) at a significance level of p < 0.05, followed by a Student–Newman–Keuls post hoc test. Principal component analysis (PCA) was employed to screen, extract, and condense the dataset, aiming to pinpoint the key volatile compounds in the wines based on grape variety. All statistical analyses were performed using the SPSS 28.0 software for Windows.

3. Results and Discussion

3.1. Conventional Analysis

The results of physicochemical analysis of Airén, Chardonnay, and Vermentino monovarietal wines and wines obtained by blending of monovarietal wines are shown in

Table 1. Conventional analysis of monovarietal wines of Airén, Chardonnay, and Vermentino grape varieties. A + C: coupage of Airén and Chardonnay; A + V: coupage of Airén and Vermentino; C + V: coupage of Chardonnay and Vermentino; A + C + V: coupage of Airén, Chardonnay and Vermentino. Mean values (n = 2) and relative standard deviation.

	Airén	Chardonnay	Vermentino	A + C	A + V	C + V	A + C + V
Ethanol (% v/v)	12.35 a (3.26)	12.97 b (1.23)	14.06 c (0.15)	12.57 a (2.23)	13.20 b (2.45)	13.60 c (1.21)	13.13 b (3.45)
Total acidity (g/L tartaric acid)	3.74 a (1.34)	4.50 b (2.15)	5.16 c (1.56)	4.20 b (1.35)	4.61 b (1.52)	4.80 c (1.15)	4.50 b (1.78)
pH	3.62 b (0.12)	3.47 a (0.48)	3.43 a (0.16)	3.52 b (0.25)	3.53 b (0.28)	3.51 b (0.30)	3.55 b (0.25)
Volatile acidity (g/L acetic acid)	0.23 a (3.45)	0.35 c (1.26)	0.35 c (1.48)	0.28 a (2.45)	0.30 b (3.12)	0.37 c (1.26)	0.32 b (0.56)
Total SO2 (mg/L)	72.94 b (3.59)	73.31 c (0.04)	72.25 a (0.65)	73.13 c (2.15)	72.60 b (3.15)	72.80 b (1.25)	72.90 b (2.29)
Free SO2 (mg/L)	15.45 c (0.69)	15.20 b (0.42)	14.95 a (1.35)	15.35 b (0.35)	15.20 b (1.56)	15.10 b (1.65)	15.25 b (1.72)

^a–c: Different superscripts in the same row indicate significant differences (α = 0.05) between samples according to SNK test.

. The values of these parameters revealed distinct characteristics among the three varieties. Ethanol content varied significantly, with Vermentino showing the highest concentration at 14.06% v/v, followed by Chardonnay (12.97% v/v) and Airén (12.35% v/v). Statistical analysis indicated a significant difference between Vermentino and the other two varieties (p < 0.05). Vermentino wine showed the highest value of total acidity, followed by Chardonnay and Airén, and Chardonnay and Vermentino showed significantly higher acidity compared to Airén. According to pH levels, they were inversely related to total acidity, with Airén having the highest pH. Significant differences were observed between Airén and the other two varieties. Volatile acidity, measured as g/L acetic acid, was lower in Airén compared to Chardonnay and Vermentino. Total SO₂ concentrations were similar across all three wines, ranging from 72.25 mg/L to 73.31 mg/L. However, free SO₂ levels showed significant differences among all three varieties, with Airén having the highest concentration. These results highlight the distinct physicochemical profiles of Airén, Chardonnay, and Vermentino wines, particularly in terms of alcohol content, acidity, and SO₂ levels. No significant differences were found between the mean values of the blended wines and the monovarietal wines used for their production.

The differences observed in alcohol content, pH, total acidity, and volatile acidity among the monovarietal wines indeed contribute to variations in the wine matrix, which can influence the volatility and perception of aromatic compounds. Higher alcohol levels generally enhance the solubility of less polar volatile compounds, potentially reducing their release, while lower pH and higher acidity can increase the volatility of certain esters and higher alcohols.

3.2. Volatile Composition of Wines

A total of seventy-one volatile compounds were identified and quantified in at least one of the six analyzed wines (monovarietal and coupage wines). Figures S1 and S2 show a representative chromatogram of the monovarietal wines and blended wines under study. Table 2 and Table 3 showed, respectively, the varietal volatile compounds and the volatile compounds formed mainly during alcoholic fermentation.

3.2.1. Varietal Volatile Compounds

The GC-MS analysis facilitated the identification of 26 different varietal aroma compounds in the wines, including C₆ compounds, benzenic compounds, terpenic compounds, and C₁₃-norisoprenoids. Generally, C₆ and benzenic compounds were the most abundant groups in all the wines examined, except for the monovarietal wines of the Vermentino variety, where terpenes and C₁₃-norisoprenoids were the dominant compounds.

The most prevalent C₆ compound in all wines was 1-hexanol, which was found in higher concentrations in monovarietal Airén wines. This higher concentration is due to the slightly lower ripeness of the grapes used in their production compared to other grape varieties, despite their overall greater maturity (Table 2). Wines blended with the Airén variety showed reduced green notes and lower concentrations of 1-hexanol, with a similar effect observed when blending was performed using wines from all three studied varieties. The concentration of terpenes and C₁₃-norisoprenoids is a significant group of varietal aroma compounds due to their low olfactory perception thresholds, often acting as “impact compounds” in the wine’s aroma profile.

Terpenic compounds are characteristic of aromatic grape varieties like Muscat and are generally associated with floral and citrus aromas, exhibiting low perception thresholds [27,28]. In this study, the Vermentino variety showed high concentrations of terpenic compounds and C₁₃-norisoprenoids, classifying it as an aromatic grape variety, while Airén and Chardonnay are considered neutral varieties. In all wines studied that included the Vermentino variety in their production, except for blends with Airén, the concentration of linalool exceeded its olfactory perception threshold of 6 µg/L [27]. The concentrations of the remaining terpenic compounds, primarily identified and quantified in wines made using the Vermentino variety, did not exceed their olfactory perception thresholds, suggesting their contribution to the wine’s aroma occurs synergistically [27].

Regarding C₁₃-norisoprenoids, β-damascenone and vomifoliol were particularly noteworthy. β-damascenone concentrations exceeded its olfactory perception threshold (0.009 µg/L) [28] in all cases. This compound is regarded as a positive contributor to wine aroma [29,30]. Wines produced through blending exhibited higher concentrations of terpenic compounds and C₁₃-norisoprenoids compared to Airén and Chardonnay wines, provided Vermentino was included in the blend. This inclusion would translate, from a sensory perspective, into an increased aromatic complexity in Chardonnay and Airén blends incorporating Vermentino.

Benzenic compounds formed a quantitatively and qualitatively significant group concerning the aroma of the studied wines. Among these compounds are aromatic alcohols, aldehydes, volatile phenols, and derivatives of shikimic acid. The monovarietal Vermentino wine exhibited the highest concentration of these compounds. Volatile phenols represent a significant subgroup within benzenic compounds, known for their distinctive contribution to wine aroma. Their impact on the overall bouquet can be either beneficial or detrimental, contingent upon their concentrations. In this investigation, the concentrations of volatile phenols did not reach levels sufficient to impart undesirable aromas to the wine. Notably, 4-vinylguaiacol was the sole volatile phenol identified, with its concentration consistently remaining below its olfactory perception threshold of 10,000 µg/L [28].

Table 2. Mean concentration (μg/L) and relative standard deviation (n = 2) of varietal volatile compounds of monovarietal and coupage wines of Airén, Chardonnay, and Vermentino grape varieties. A + C: coupage of Airén and Chardonnay; A + V: coupage of Airén and Vermentino; C + V: coupage of Chardonnay and Vermentino; A + C + V: coupage of Airén, Chardonnay, and Vermentino.

	Airén		Chardonnay		Vermentino		A + C		A + V		C + V		A + C + V
	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR
1-hexanol	418.31 c	(3.05)	494.87 d	(1.51)	182.09 a	(3.74)	321.64 b	(7.98)	189.30 a	(1.31)	322.49 b	(1.32)	285.20 b	(8.17)
(E)-3-Hexen-1-ol	74.45 b,c	(1.64)	114.62 d	(3.00)	46.87 a	(2.67)	93.79 c	(4.30)	63.84 a	(9.01)	78.60 b,c	(4.85)	76.18 b,c	(8.59)
(Z)-3-Hexen-1-ol	264.98 c,d	(3.03)	170.19 b	(0.61)	11.28 a	(6.87)	337.22 d	(7.70)	297.25 d	(9.44)	33.59 a	(1.17)	241.98 c	(6.09)
(Z)-2-hexen-1-ol	n.d.	-	n.d.	-	1.11 b	(5.57)	n.d.	-	0.94 a	(1.15)	n.d.	-	3.13 c	(1.21)
2-ethyl-1-hexanol	2.79 a	(5.78)	7.45 c	(1.87)	10.60 d	(3.64)	10.19 d	(0.71)	10.90 d,e	(5.32)	11.56 e	(0.80)	3.50 b	(0.12)
C6 Compounds	760.53		787.13		251.95		762.84		562.23		446.24		609.99
Linalool	2.29 a	(2.84)	2.77 a	(2.34)	65.46 c	(6.18)	3.03 a	(0.01)	25.52 b	(8.68)	30.42 b	(3.85)	25.54 b	(0.97)
Hotrienol	n.d.	-	n.d.	-	19.79 c	(5.96)	n.d.	-	9.04 b	(6.95)	7.87 b	(0.37)	5.40 a	(3.64)
β-Citronellol	n.d.	-	n.d.	-	13.03 d	(1.71)	n.d.	-	7.58 e	(9.66)	6.10 b	(2.71)	3.82 a	(4.24)
Nerol	n.d.	-	2.84 a	(1.57)	6.05 b	(2.52)	n.d.	-	4.75 b	(3.86)	8.65 c	(2.33)	3.21 a	(1.21)
Geraniol	0.8 a	(5.98)	1.25 a	(1.26)	8.44 c	(4.54)	4.79 b	(3.18)	8.54 c	(7.21)	12.69 e	(1.34)	10.99 d	(1.67)
2,6-dimethyl-3,7-octadiene-2,6-diol	n.d.	-	n.d.	-	139.48 c	(3.05)	n.d.	-	63.14 b	(1.07)	7.11 a	(4.87)	63.72 b	(5.80)
Trans 8-Hidroxilinalool	n.d.	-	n.d.	-	56.69 b	(4.52)	n.d.	-	16.88 a	(7.95)	n.d.	-	n.d.	-
β-damascenone	0.88 a	(0.20)	1.74 a	(0.57)	11.96 d	(7.66)	5.77 b	(8.54)	8.75 c	(5.98)	9.46 c	(0.40)	9.71 c	(4.66)
Vomifoliol	4.61 b	(2.28)	n.d.	-	n.d.	-	7.51 c	(0.44)	2.59 a	(5.75)	n.d.	-	n.d.	-
Terpenic compounds + C13-norisoprenoids	8.58		8.60		320.90		21.10		146.79		82.30		122.39
Benzaldehyde	0.32 a	(5.19)	n.d.	-	0.75 a	(2.61)	5.02 c	(6.52)	0.47 a	(6.92)	n.d.	-	3.83 b	(1.94)
-2-methyl-3(2H)-dihydro-thiophenone	20.47 a	(4.66)	21.8 a	(5.73)	35.36 c	(5.15)	24.15 a	(6.23)	24.20 a	(1.60)	29.76 b	(1.05)	23.77 a	(1.26)
Benzyl alcohol	27.40 a	(1.54)	50.36 b	(1.26)	68.89 c	(7.12)	30.55 a	(2.82)	27.01 a	(2.58)	31.06 a	(1.51)	37.61 a	(1.25)
2,3-dihydrobenzofuran	n.d.	-	2.97 c	(5.51)	n.d.	-	2.24 b	(8.68)	2.27 b	(1.93)	3.47 d	(1.49)	4.57 e	(7.90)
4-vinylguaiacol	4.61 b	(2.28)	n.d.	-	n.d.	-	7.51 c	(0.44)	2.59 a	(5.75)	n.d.	-	n.d.	-
4-methoxyacetophenone	22.06 a	(6.57)	167.38 c	(1.14)	330.48 e	(0.90)	105.27 b	(5.69)	202.81 d	(2.72)	20.48 a	(1.03)	102.63 b	(9.90)
Eugenol	n.d.	-	3.03 b	(8.23)	9.44 e	(3.53)	2.67 b	(1.19)	5.78 d	(4.40)	4.72 c	(2.51)	9.50 e	(0.87)
Methyl vanillate	4.07 c	(0.96)	3.49 a	(1.27)	n.d.	-	4.31 c	(6.57)	5.58 d	(8.96)	2.64 b	(8.63)	4.33 c	(0.47)
Vanillin	4.53 a	(6.18)	12.04 c	(9.07)	n.d.	-	5.58 a	(6.25)	6.20 b	(4.82)	18.06 d	(1.82)	6.09 b	(3.35)
Acetovanillone	14.40 a	(8.60)	44.17 c	(2.23)	25.26 b	(2.37)	18.23 a	(2.53)	15.17 c	(6.57)	46.41 a	(1.71)	12.17 a	(0.51)
Zingerone	5.40 c	(0.71)	2.93 b	(5.67)	25.44 f	(3.35)	6.05 c,d	(5.78)	20.2 e	(6.57)	0.45 a	(5.38)	7.38 d	(6.03)
Bencenic compounds	103.26		308.17		495.62		211.58		312.28		157.05		211.88

^a–f: Different superscripts in the same row indicate significant differences (α = 0.05) between samples according to SNK test. n.d.: not detected.

Table 2. Mean concentration (μg/L) and relative standard deviation (n = 2) of varietal volatile compounds of monovarietal and coupage wines of Airén, Chardonnay, and Vermentino grape varieties. A + C: coupage of Airén and Chardonnay; A + V: coupage of Airén and Vermentino; C + V: coupage of Chardonnay and Vermentino; A + C + V: coupage of Airén, Chardonnay, and Vermentino.

	Airén		Chardonnay		Vermentino		A + C		A + V		C + V		A + C + V
	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR
1-hexanol	418.31 c	(3.05)	494.87 d	(1.51)	182.09 a	(3.74)	321.64 b	(7.98)	189.30 a	(1.31)	322.49 b	(1.32)	285.20 b	(8.17)
(E)-3-Hexen-1-ol	74.45 b,c	(1.64)	114.62 d	(3.00)	46.87 a	(2.67)	93.79 c	(4.30)	63.84 a	(9.01)	78.60 b,c	(4.85)	76.18 b,c	(8.59)
(Z)-3-Hexen-1-ol	264.98 c,d	(3.03)	170.19 b	(0.61)	11.28 a	(6.87)	337.22 d	(7.70)	297.25 d	(9.44)	33.59 a	(1.17)	241.98 c	(6.09)
(Z)-2-hexen-1-ol	n.d.	-	n.d.	-	1.11 b	(5.57)	n.d.	-	0.94 a	(1.15)	n.d.	-	3.13 c	(1.21)
2-ethyl-1-hexanol	2.79 a	(5.78)	7.45 c	(1.87)	10.60 d	(3.64)	10.19 d	(0.71)	10.90 d,e	(5.32)	11.56 e	(0.80)	3.50 b	(0.12)
C6 Compounds	760.53		787.13		251.95		762.84		562.23		446.24		609.99
Linalool	2.29 a	(2.84)	2.77 a	(2.34)	65.46 c	(6.18)	3.03 a	(0.01)	25.52 b	(8.68)	30.42 b	(3.85)	25.54 b	(0.97)
Hotrienol	n.d.	-	n.d.	-	19.79 c	(5.96)	n.d.	-	9.04 b	(6.95)	7.87 b	(0.37)	5.40 a	(3.64)
β-Citronellol	n.d.	-	n.d.	-	13.03 d	(1.71)	n.d.	-	7.58 e	(9.66)	6.10 b	(2.71)	3.82 a	(4.24)
Nerol	n.d.	-	2.84 a	(1.57)	6.05 b	(2.52)	n.d.	-	4.75 b	(3.86)	8.65 c	(2.33)	3.21 a	(1.21)
Geraniol	0.8 a	(5.98)	1.25 a	(1.26)	8.44 c	(4.54)	4.79 b	(3.18)	8.54 c	(7.21)	12.69 e	(1.34)	10.99 d	(1.67)
2,6-dimethyl-3,7-octadiene-2,6-diol	n.d.	-	n.d.	-	139.48 c	(3.05)	n.d.	-	63.14 b	(1.07)	7.11 a	(4.87)	63.72 b	(5.80)
Trans 8-Hidroxilinalool	n.d.	-	n.d.	-	56.69 b	(4.52)	n.d.	-	16.88 a	(7.95)	n.d.	-	n.d.	-
β-damascenone	0.88 a	(0.20)	1.74 a	(0.57)	11.96 d	(7.66)	5.77 b	(8.54)	8.75 c	(5.98)	9.46 c	(0.40)	9.71 c	(4.66)
Vomifoliol	4.61 b	(2.28)	n.d.	-	n.d.	-	7.51 c	(0.44)	2.59 a	(5.75)	n.d.	-	n.d.	-
Terpenic compounds + C13-norisoprenoids	8.58		8.60		320.90		21.10		146.79		82.30		122.39
Benzaldehyde	0.32 a	(5.19)	n.d.	-	0.75 a	(2.61)	5.02 c	(6.52)	0.47 a	(6.92)	n.d.	-	3.83 b	(1.94)
-2-methyl-3(2H)-dihydro-thiophenone	20.47 a	(4.66)	21.8 a	(5.73)	35.36 c	(5.15)	24.15 a	(6.23)	24.20 a	(1.60)	29.76 b	(1.05)	23.77 a	(1.26)
Benzyl alcohol	27.40 a	(1.54)	50.36 b	(1.26)	68.89 c	(7.12)	30.55 a	(2.82)	27.01 a	(2.58)	31.06 a	(1.51)	37.61 a	(1.25)
2,3-dihydrobenzofuran	n.d.	-	2.97 c	(5.51)	n.d.	-	2.24 b	(8.68)	2.27 b	(1.93)	3.47 d	(1.49)	4.57 e	(7.90)
4-vinylguaiacol	4.61 b	(2.28)	n.d.	-	n.d.	-	7.51 c	(0.44)	2.59 a	(5.75)	n.d.	-	n.d.	-
4-methoxyacetophenone	22.06 a	(6.57)	167.38 c	(1.14)	330.48 e	(0.90)	105.27 b	(5.69)	202.81 d	(2.72)	20.48 a	(1.03)	102.63 b	(9.90)
Eugenol	n.d.	-	3.03 b	(8.23)	9.44 e	(3.53)	2.67 b	(1.19)	5.78 d	(4.40)	4.72 c	(2.51)	9.50 e	(0.87)
Methyl vanillate	4.07 c	(0.96)	3.49 a	(1.27)	n.d.	-	4.31 c	(6.57)	5.58 d	(8.96)	2.64 b	(8.63)	4.33 c	(0.47)
Vanillin	4.53 a	(6.18)	12.04 c	(9.07)	n.d.	-	5.58 a	(6.25)	6.20 b	(4.82)	18.06 d	(1.82)	6.09 b	(3.35)
Acetovanillone	14.40 a	(8.60)	44.17 c	(2.23)	25.26 b	(2.37)	18.23 a	(2.53)	15.17 c	(6.57)	46.41 a	(1.71)	12.17 a	(0.51)
Zingerone	5.40 c	(0.71)	2.93 b	(5.67)	25.44 f	(3.35)	6.05 c,d	(5.78)	20.2 e	(6.57)	0.45 a	(5.38)	7.38 d	(6.03)
Bencenic compounds	103.26		308.17		495.62		211.58		312.28		157.05		211.88

^a–f: Different superscripts in the same row indicate significant differences (α = 0.05) between samples according to SNK test. n.d.: not detected.

Table 3. Mean concentration (μg/L) and relative standard deviation (n = 2) of fermentative volatile compounds of monovarietal and coupage wines of Airén, Chardonnay, and Vermentino grape varieties. A + C: coupage of Airén and Chardonnay; A + V: coupage of Airén and Vermentino; C + V: coupage of Chardonnay and Vermentino; A + C + V: coupage of Airén, Chardonnay, and Vermentino.

	Airén		Chardonnay		Vermentino		A + C		A + V		C + V		A + C + V
	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR
Ethyl butyrate	94.84 a	(2.63)	150.38 b	(5.22)	214.70 c	(1.87)	97.95 a	(6.14)	117.31 a,b	(8.87)	251.18 d	(5.84)	117.31 a,b	(0.20)
Isoamyl acetate	1813.48 b	(5.11)	1485.15 a,b	(1.85)	354.36 a,b	(1.63)	1185.42 a	(4.53)	1106.46 a	(1.60)	1157.43 a,b	(2.03)	1265.95 a,b	(4.26)
Hexyl acetate	69.09 a	(5.42)	145.37 c	(3.93)	66.44 a	(1.76)	89.16 a,b	(2.96)	71.90 a	(1.80)	99.32 b	(7.59)	80.27 a,b	(8.00)
Ethyl hexanoate	341.04 a	(3.70)	564.12 b	(3.29)	354.36 c	(9.36)	431.48 a,b	(3.23)	464.49 a,b	(3.96)	823.83 c	(1.49)	519.09 b	(1.40)
Ethyl lactate	256.78 c	(8.02)	146.25 a	(1.74)	284.25 c	(8.81)	121.77 a	(1.75)	173.19 a,b	(9.74)	208.98 b	(9.04)	165.03 ab	(3.30)
Ethyl octanoate	1030.53 a,b	(3.98)	1275.22 a,b	(4.34)	1449.48 b	(3.87)	1306.62 a,b	(1.46)	898.41 a	(8.98)	1200.21 a,b	(9.57)	1099.04 a,b	(8.72)
3-hydroxyethyl butyrate	17.42 a	(4.55)	51.13 e	(6.62)	40.62 d	(7.36)	29.70 b,c	(6.72)	26.65 b	(8.92)	38.28 d	(5.16)	34.95 c,d	(2.59)
Ethyl decanoate	276.07 a	(1.52)	453.67 b	(4.42)	485.10 b	(0.99)	244.41 a	(1.05)	268.91 a	(8.19)	450.78 b	(5.55)	394.57 b	(3.43)
Diethyl succinate	249.72 a	(2.78)	436.78 b	(1.41)	916.32 c	(5.93)	319.18 a	(3.90)	493.47 b	(8.11)	236.87 a	(9.90)	564.15 b	(1.36)
Ethyl-9-decenoate	257.7 c,d	(2.59)	110.06 a	(4.48)	320.51 d	(2.93)	178.6 a,b	(5.13)	250.59 c,d	(7.71)	191.82 b,c	(0.90)	264.77 c,d	(3.18)
2-phenethyl acetate	159.19 a	(1.95)	192.47 a	(9.07)	264.65 b	(7.55)	156.49 a	(6.32)	182.98 a	(6.80)	200.24 a	(1.05)	253.69 b	(7.06)
4-hydroxyethyl butyrate	254.26 a	(6.47)	436.36 b	(9.16)	519.41 c	(6.96)	185.05 a	(5.52)	677.54 d	(2.60)	421.61 b	(8.96)	543.70 c	(7.09)
Ethyl dodecanoate	24.29 a	(3.49)	37.69 a	(5.97)	36.64 a	(7.60)	18.40 a	(7.72)	20.6 a	(6.63)	30.37 a	(2.88)	333.83 b	(6.13)
Diethyl malate	68.50 a	(5.00)	411.75 e	(6.80)	316.93 d	(1.06)	216.06 c	(9.58)	160.4 b	(4.30)	367.99 d	(6.43)	319.37 d	(1.00)
Esters	4912.91		5896.40		5597.07		4580.29		4912.90		5678.91		5955.72
2-methyl-1- propanol	500.77 c	(1.52)	227.15 a	(7.50)	354.36 b	(4.52)	316.27 b	(3.88)	308.04 b	(4.22)	307.83 b	(0.77)	322.09 b	(9.77)
1-pentanol	10.25 a	(6.82)	28.71 b,c	(0.76)	35.29 c	(6.21)	23.57 b	(5.54)	16.21 a	(6.39)	32.74 c	(4.87)	26.60 b,c	(2.58)
3-methyl-1-pentanol	24.00 c	(4.43)	2.52 a	(1.79)	5.32 a	(0.83)	3.61 a	(9.38)	6.53 a	(4.18)	24.71 c	(0.99)	13.66 b	(2.01)
4-methyl-1-pentanol	22.16 c	(0.69)	38.26 d	(2.81)	2.80 a	(2.58)	23.59 c	(1.33)	3.25 a	(7.72)	8.72 a	(0.24)	11.56 b	(2.14)
1 -heptanol	44.07 e	(1.48)	16.86 b	(9.58)	5.85 a	(0.97)	26.58 c,d	(2.58)	29.55 d	(5.42)	14.68 b	(9.42)	24.02 c	(8.93)
2,3-Butanodiol (levo)	5.48 a	(5.70)	12.24 b	(5.42)	40.60 d	(6.66)	13.72 b	(8.50)	19.74 c	(3.01)	14.49 b	(8.98)	5.52 a	(0.88)
2,3-Butanodiol (meso)	4.14 c	(8.67)	2.17 a	(5.87)	30.42 g	(0.23)	7.73 e	(3.67)	3.47 b	(1.27)	15.04 f	(3.60)	5.33 d	(3.70)
3-methylthio-1-propanol	95.28 b	(3.80)	58.08 a	(3.22)	70.12 a	(7.10)	69.42 a	(1.14)	90.94 b	(7.80)	60.13 a	(0.34)	96.14 b	(4.31)
2-phenylethanol	9146.68 a,b	(0.13)	7411.73 a,b	(8.93)	7859.56 a,b	(0.49)	6836.43 a,b	(3.56)	6322.92 a	(4.47)	7804.38 a,b	(2.79)	9496.12 b	(5.25)
Alcohols	9852.83		7797.72		8404.32		7320.92		6800.65		8282.73		10,001.04
Acetic acid	11.86 c	(3.91)	16.49 e	(4.25)	n.d.	-	14.09 d	(4.43)	28.26 f	(0.00)	3.10 b	(2.96)	3.44 b	(0.00)
Propanoic acid	0.58 a,b	(7.75)	1.53 b	(5.56)	7.66 c	(4.81)	0.56 a,b	(1.23)	1.03 a,b	(8.29)	n.d.	-	9.12 d	(8.91)
Isobutyric acid	52.71 a,b	(2.68)	42.66 a	(5.96)	43.62 a	(0.24)	64.77 b	(1.67)	49.78 a,b	(5.87)	44.84 a	(6.72)	52.7 a,b	(1.05)
Butanoic acid	87.45 a	(7.04)	97.96 a	(1.99)	76.47 a	(3.81)	90.37 a	(3.97)	86.21 a	(7.06)	98.97 a	(0.65)	97.95 a	(1.28)
Pentanoic acid	2.31 a	(1.11)	2.89 a,b	(2.13)	5.51 c	(1.82)	4.84 b,c	(8.78)	4.12 a,b,c	(7.85)	6.23 c	(6.72)	6.11 c	(9.47)
Hexanoic acid	1597.42 b	(4.56)	1540.43 b	(6.74)	2016.45 c	(0.47)	1282.72 a	(5.77)	1189.47 a	(2.66)	1814.81 b,c	(3.57)	1933.69 c	(8.30)
trans 2-hexenoic acid	17.24 c	(1.33)	50.11 f	(0.60)	10.35 b	(1.75)	33.19 d	(4.15)	5.54 a	(6.12)	37.31 e	(5.62)	36.35 e	(1.43)
trans 3-hexenoic acid	22.56 c	(5.95)	8.04 a	(2.50)	13.31 b	(9.97)	12.59 b	(7.46)	6.83 a	(0.97)	11.69 b	(7.31)	23.61 c	(7.34)
Octanoic acid	1962.17 a	(1.90)	3200.73 b,c	(1.13)	4190.72 d	(2.75)	2468.75 a,b	(6.47)	2391.44 a,b	(3.16)	3742.93 c,d	(2.92)	4048.69 d	(1.91)
Nonanoic acid	7.85 a	(0.42)	11.69 a,b	(2.36)	21.35 c	(2.71)	8.90 a	(6.65)	16.67 b,c	(2.41)	11.77 ab	(3.95)	27.95 d	(7.12)
Decanoic acid	670.87 a	(6.25)	1419.71 c	(1.04)	1796.55 d	(8.62)	971.41 b	(5.99)	1017.3 b	(1.00)	1355.46 c	(4.24)	1678.05 d	(5.06)
3-methylthio-1-propanoic acid	n.d.	-	1.58 c	(7.65)	n.d.	-	0.52 b	(2.35)	n.d.	-	3.80 d	(4.23)	5.07 e	(5.91)
Dodecanoic acid	39.93 a	(1.28)	42.67 a	(2.68)	143.57 c	(6.44)	35.57 a	(1.51)	157.27 d	(1.41)	37.75 a	(3.70)	116.13 b	(2.37)
Acids	4472.97		6436.47		8325.56		4988.28		4953.92		7168.67		8038.88
γ-Butyrolactone	232.07 d	(1.75)	2.97 a	(6.51)	16.09 a	(5.67)	12.45 a	(3.04)	56.3 b	(3.24)	213.43 d	(0.84)	99.31 c	(8.32)
Lactones	232.07		2.97		16.09		12.45		56.30		213.43		99.31

^a–g: Different superscripts in the same row indicate significant differences (α = 0.05) between samples according to SNK test. n.d.: not detected. 3.3. Principal Component Analysis.

Table 3. Mean concentration (μg/L) and relative standard deviation (n = 2) of fermentative volatile compounds of monovarietal and coupage wines of Airén, Chardonnay, and Vermentino grape varieties. A + C: coupage of Airén and Chardonnay; A + V: coupage of Airén and Vermentino; C + V: coupage of Chardonnay and Vermentino; A + C + V: coupage of Airén, Chardonnay, and Vermentino.

	Airén		Chardonnay		Vermentino		A + C		A + V		C + V		A + C + V
	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR	Mean	%DSR
Ethyl butyrate	94.84 a	(2.63)	150.38 b	(5.22)	214.70 c	(1.87)	97.95 a	(6.14)	117.31 a,b	(8.87)	251.18 d	(5.84)	117.31 a,b	(0.20)
Isoamyl acetate	1813.48 b	(5.11)	1485.15 a,b	(1.85)	354.36 a,b	(1.63)	1185.42 a	(4.53)	1106.46 a	(1.60)	1157.43 a,b	(2.03)	1265.95 a,b	(4.26)
Hexyl acetate	69.09 a	(5.42)	145.37 c	(3.93)	66.44 a	(1.76)	89.16 a,b	(2.96)	71.90 a	(1.80)	99.32 b	(7.59)	80.27 a,b	(8.00)
Ethyl hexanoate	341.04 a	(3.70)	564.12 b	(3.29)	354.36 c	(9.36)	431.48 a,b	(3.23)	464.49 a,b	(3.96)	823.83 c	(1.49)	519.09 b	(1.40)
Ethyl lactate	256.78 c	(8.02)	146.25 a	(1.74)	284.25 c	(8.81)	121.77 a	(1.75)	173.19 a,b	(9.74)	208.98 b	(9.04)	165.03 ab	(3.30)
Ethyl octanoate	1030.53 a,b	(3.98)	1275.22 a,b	(4.34)	1449.48 b	(3.87)	1306.62 a,b	(1.46)	898.41 a	(8.98)	1200.21 a,b	(9.57)	1099.04 a,b	(8.72)
3-hydroxyethyl butyrate	17.42 a	(4.55)	51.13 e	(6.62)	40.62 d	(7.36)	29.70 b,c	(6.72)	26.65 b	(8.92)	38.28 d	(5.16)	34.95 c,d	(2.59)
Ethyl decanoate	276.07 a	(1.52)	453.67 b	(4.42)	485.10 b	(0.99)	244.41 a	(1.05)	268.91 a	(8.19)	450.78 b	(5.55)	394.57 b	(3.43)
Diethyl succinate	249.72 a	(2.78)	436.78 b	(1.41)	916.32 c	(5.93)	319.18 a	(3.90)	493.47 b	(8.11)	236.87 a	(9.90)	564.15 b	(1.36)
Ethyl-9-decenoate	257.7 c,d	(2.59)	110.06 a	(4.48)	320.51 d	(2.93)	178.6 a,b	(5.13)	250.59 c,d	(7.71)	191.82 b,c	(0.90)	264.77 c,d	(3.18)
2-phenethyl acetate	159.19 a	(1.95)	192.47 a	(9.07)	264.65 b	(7.55)	156.49 a	(6.32)	182.98 a	(6.80)	200.24 a	(1.05)	253.69 b	(7.06)
4-hydroxyethyl butyrate	254.26 a	(6.47)	436.36 b	(9.16)	519.41 c	(6.96)	185.05 a	(5.52)	677.54 d	(2.60)	421.61 b	(8.96)	543.70 c	(7.09)
Ethyl dodecanoate	24.29 a	(3.49)	37.69 a	(5.97)	36.64 a	(7.60)	18.40 a	(7.72)	20.6 a	(6.63)	30.37 a	(2.88)	333.83 b	(6.13)
Diethyl malate	68.50 a	(5.00)	411.75 e	(6.80)	316.93 d	(1.06)	216.06 c	(9.58)	160.4 b	(4.30)	367.99 d	(6.43)	319.37 d	(1.00)
Esters	4912.91		5896.40		5597.07		4580.29		4912.90		5678.91		5955.72
2-methyl-1- propanol	500.77 c	(1.52)	227.15 a	(7.50)	354.36 b	(4.52)	316.27 b	(3.88)	308.04 b	(4.22)	307.83 b	(0.77)	322.09 b	(9.77)
1-pentanol	10.25 a	(6.82)	28.71 b,c	(0.76)	35.29 c	(6.21)	23.57 b	(5.54)	16.21 a	(6.39)	32.74 c	(4.87)	26.60 b,c	(2.58)
3-methyl-1-pentanol	24.00 c	(4.43)	2.52 a	(1.79)	5.32 a	(0.83)	3.61 a	(9.38)	6.53 a	(4.18)	24.71 c	(0.99)	13.66 b	(2.01)
4-methyl-1-pentanol	22.16 c	(0.69)	38.26 d	(2.81)	2.80 a	(2.58)	23.59 c	(1.33)	3.25 a	(7.72)	8.72 a	(0.24)	11.56 b	(2.14)
1 -heptanol	44.07 e	(1.48)	16.86 b	(9.58)	5.85 a	(0.97)	26.58 c,d	(2.58)	29.55 d	(5.42)	14.68 b	(9.42)	24.02 c	(8.93)
2,3-Butanodiol (levo)	5.48 a	(5.70)	12.24 b	(5.42)	40.60 d	(6.66)	13.72 b	(8.50)	19.74 c	(3.01)	14.49 b	(8.98)	5.52 a	(0.88)
2,3-Butanodiol (meso)	4.14 c	(8.67)	2.17 a	(5.87)	30.42 g	(0.23)	7.73 e	(3.67)	3.47 b	(1.27)	15.04 f	(3.60)	5.33 d	(3.70)
3-methylthio-1-propanol	95.28 b	(3.80)	58.08 a	(3.22)	70.12 a	(7.10)	69.42 a	(1.14)	90.94 b	(7.80)	60.13 a	(0.34)	96.14 b	(4.31)
2-phenylethanol	9146.68 a,b	(0.13)	7411.73 a,b	(8.93)	7859.56 a,b	(0.49)	6836.43 a,b	(3.56)	6322.92 a	(4.47)	7804.38 a,b	(2.79)	9496.12 b	(5.25)
Alcohols	9852.83		7797.72		8404.32		7320.92		6800.65		8282.73		10,001.04
Acetic acid	11.86 c	(3.91)	16.49 e	(4.25)	n.d.	-	14.09 d	(4.43)	28.26 f	(0.00)	3.10 b	(2.96)	3.44 b	(0.00)
Propanoic acid	0.58 a,b	(7.75)	1.53 b	(5.56)	7.66 c	(4.81)	0.56 a,b	(1.23)	1.03 a,b	(8.29)	n.d.	-	9.12 d	(8.91)
Isobutyric acid	52.71 a,b	(2.68)	42.66 a	(5.96)	43.62 a	(0.24)	64.77 b	(1.67)	49.78 a,b	(5.87)	44.84 a	(6.72)	52.7 a,b	(1.05)
Butanoic acid	87.45 a	(7.04)	97.96 a	(1.99)	76.47 a	(3.81)	90.37 a	(3.97)	86.21 a	(7.06)	98.97 a	(0.65)	97.95 a	(1.28)
Pentanoic acid	2.31 a	(1.11)	2.89 a,b	(2.13)	5.51 c	(1.82)	4.84 b,c	(8.78)	4.12 a,b,c	(7.85)	6.23 c	(6.72)	6.11 c	(9.47)
Hexanoic acid	1597.42 b	(4.56)	1540.43 b	(6.74)	2016.45 c	(0.47)	1282.72 a	(5.77)	1189.47 a	(2.66)	1814.81 b,c	(3.57)	1933.69 c	(8.30)
trans 2-hexenoic acid	17.24 c	(1.33)	50.11 f	(0.60)	10.35 b	(1.75)	33.19 d	(4.15)	5.54 a	(6.12)	37.31 e	(5.62)	36.35 e	(1.43)
trans 3-hexenoic acid	22.56 c	(5.95)	8.04 a	(2.50)	13.31 b	(9.97)	12.59 b	(7.46)	6.83 a	(0.97)	11.69 b	(7.31)	23.61 c	(7.34)
Octanoic acid	1962.17 a	(1.90)	3200.73 b,c	(1.13)	4190.72 d	(2.75)	2468.75 a,b	(6.47)	2391.44 a,b	(3.16)	3742.93 c,d	(2.92)	4048.69 d	(1.91)
Nonanoic acid	7.85 a	(0.42)	11.69 a,b	(2.36)	21.35 c	(2.71)	8.90 a	(6.65)	16.67 b,c	(2.41)	11.77 ab	(3.95)	27.95 d	(7.12)
Decanoic acid	670.87 a	(6.25)	1419.71 c	(1.04)	1796.55 d	(8.62)	971.41 b	(5.99)	1017.3 b	(1.00)	1355.46 c	(4.24)	1678.05 d	(5.06)
3-methylthio-1-propanoic acid	n.d.	-	1.58 c	(7.65)	n.d.	-	0.52 b	(2.35)	n.d.	-	3.80 d	(4.23)	5.07 e	(5.91)
Dodecanoic acid	39.93 a	(1.28)	42.67 a	(2.68)	143.57 c	(6.44)	35.57 a	(1.51)	157.27 d	(1.41)	37.75 a	(3.70)	116.13 b	(2.37)
Acids	4472.97		6436.47		8325.56		4988.28		4953.92		7168.67		8038.88
γ-Butyrolactone	232.07 d	(1.75)	2.97 a	(6.51)	16.09 a	(5.67)	12.45 a	(3.04)	56.3 b	(3.24)	213.43 d	(0.84)	99.31 c	(8.32)
Lactones	232.07		2.97		16.09		12.45		56.30		213.43		99.31

^a–g: Different superscripts in the same row indicate significant differences (α = 0.05) between samples according to SNK test. n.d.: not detected. 3.3. Principal Component Analysis.

Another noteworthy category within benzenic compounds includes shikimic acid derivatives, which possess a pronounced sensory influence. These compounds are derived from the metabolic pathways of aromatic amino acids in plants or yeast, although they may also be extracted from wood [31]. Among these, vanillin and its derivatives are prominent, contributing sweet spice notes to the wine’s aroma. Their concentrations were relatively low across all wines examined, with blended wines displaying intermediate levels compared to the monovarietal wines utilized in their production. Additionally, benzaldehyde, benzyl alcohol, and eugenol warrant attention within benzenic compounds. The concentrations of benzaldehyde and benzyl alcohol did not exceed their respective olfactory perception thresholds of 350 and 10,000 µg/L [27], although they may synergistically enhance fruity and floral notes in the wine aroma. The presence of eugenol is linked to sweet spice aromas, particularly clove-like notes. Monovarietal Vermentino wines and blends of all three studied varieties exhibited significantly higher concentrations of this compound compared to other wines, surpassing its olfactory perception threshold of 5 µg/L [28] and thereby contributing distinctively to their aroma profiles.

3.2.2. Volatile Compounds Formed Mainly During Alcoholic Fermentation

While grape-derived compounds predominantly contribute to the varietal characteristics of wines, compounds formed during alcoholic fermentation via yeast metabolism can exert either beneficial or detrimental effects on the sensory attributes of wines [32]. Table 3 delineates the concentrations (µg/L) of volatile compounds primarily generated during the alcoholic fermentation of monovarietal and coupage wines, presented as the average of two duplicate analyses. The principal fermentation-derived compounds, alcohols, ethyl esters, acetates, and acids, were identified at comparable concentrations across all wines, albeit with some variations.

Ethyl esters of fatty acids and acetates are considered significant contributors to wine aroma, as they impart fruity notes commonly associated with the aromatic profile of wines [24,32,33]. The identified concentrations of diethyl succinate and ethyl lactate in the studied wines ranged from 916.32 to 236.87 µg/L for diethyl succinate and from 284.25 to 146.25 µg/L for ethyl lactate. Monovarietal Airén and Vermentino wines exhibited the highest ethyl lactate concentrations. Coupage wines generally displayed lower concentrations of these compounds compared to monovarietal wines, except for Chardonnay blends.

Acetate esters (isoamyl acetate, hexyl acetate, and 2-phenylethyl acetate) are recognized as quality markers in young wines [34,35]. None of the wines studied surpassed the olfactory perception threshold of these compounds, though their aroma may contribute synergistically with other wine components. This phenomenon occurs because their aromatic descriptors—banana and floral notes—are often used to characterize the aroma of these wine varieties [36].

Regarding ethyl esters, the most abundant were ethyl hexanoate (823.83–341.04 µg/L) and ethyl octanoate (1449.48–898.41 µg/L), both exceeding their olfactory perception thresholds—200 µg/L and 5 µg/L, respectively [27,28]—suggesting that they individually contribute to wine aroma.

Regarding minor alcohols, the notably high concentration of 2-phenylethanol, primarily produced through yeast metabolism [27,37], is significant due to its floral aroma with rose-like notes. However, in none of the wines studied did its concentration exceed the olfactory perception threshold (10,000 µg/L) [28], precluding its individual contribution to wine aroma [38], although it may have a synergistic effect. Monovarietal Airén wines and coupages of the three studied varieties exhibited the highest concentrations of this compound.

Among carboxylic acids, butyric, hexanoic, octanoic, and decanoic acids were the most abundant. While acids are not typically associated with wine quality, they play a crucial role in aroma complexity [39]. Their production is primarily influenced by must composition and fermentation conditions [40], resulting in minimal variations in acid concentrations between blended wines and monovarietal wines.

Given the extensive array of compounds identified in wine aroma and their varying concentrations, discerning which compounds contribute to the differences in the chemical aroma profile of the wines under study is a complex task. To facilitate this analysis, principal component analysis (PCA) was employed on the aroma compounds of the wines to identify the key compounds correlated with the wine samples.

The first three principal components account for 72.86% of the total variance among the monovarietal wines and those produced through the blending technique of monovarietal wines.

Table 4. Correlation coefficients for wine volatile compounds against principal components 1, 2, and 3.

Compound	Component
	1	2	3
3-oxo-alpha-ionol	0.961	0.068	−0.042
Methyl vanillate	−0.949	−0.131	0.098
3-hydroxyethyl butyrate	0.869	−0.194	0.144
Ethyl decanoate	0.844	0.032	0.235
1-pentanol	0.837	0.051	0.164
1-heptanol	−0.835	−0.218	−0.096
Diethyl malate	0.828	−0.295	0.238
Benzyl alcohol	0.788	0.482	0.203
Ethyl octanoate	0.785	0.179	−0.08
3-methylthio-1-propanol	−0.751	0.209	0.473
(Z)-3-Hexen-1-ol	−0.75	−0.244	0.081
Acetovanillone	0.718	−0.398	−0.409
Decanoic acid	0.704	0.192	0.577
Ethyl hexanoate	0.689	0.114	−0.04
Octanoic acid	0.675	0.119	0.524
Ethyl butyrate	0.661	0.127	−0.181
Zingerone	−0.032	0.941	0.136
8-hydroxylinalool	0.352	0.925	0.036
(E)-2-hexenoic acid	0.47	−0.853	0.117
Diendiol I	0.209	0.841	0.432
2,3-Butanediol (levo)	0.453	0.826	−0.157
Butanoic acid	0.045	−0.823	0.154
(E)-3-Hexen-1-ol	0.196	−0.82	−0.155
Hotrienol	0.311	0.791	0.153
Ethyl 9-decanoate	−0.238	0.772	0.369
Vanillin	0.197	−0.767	−0.285
Citronellol	0.24	0.767	0.128
4-hydroxy-3-methylacetophenone	0.388	0.758	0.151
Diethyl succinate	0.411	0.748	0.462
Linalool	0.375	0.727	0.24
Dodecanoic acid	−0.153	0.716	0.474
% Variance explained by PC	39.20	21.19	12.47
Cumulative% of variance	39.20	60.38	72.86

presents the compounds that exhibited the highest correlation with the first three principal components.

Figure 1 illustrates the projection of the three monovarietal wines and the four coupage wines, plotted within the plane defined by the first two principal components. The volatile aroma compounds most correlated with these two principal components are also represented.

Based on the results, Principal Component 1 (PC1) distinguishes monovarietal Chardonnay and Vermentino wines, as well as their blended wines, due to their higher concentrations of zingerone, 8-hydroxylinalool, diendiol I, hotrienol, 2,3-butanediol (levo), citronellol, ethyl 9-decanoate, dodecanoic acid, diethyl succinate, linalool, and 4-methoxycetophenone. Monovarietal Airén wines and blends incorporating Airén are positioned to the left of PC1 due to their higher concentrations of methyl vanillate, (Z)-3-hexen-1-ol, 1-heptanol, and 3-methylthio-1-propanol.

Regarding Principal Component 2 (PC2), this separates monovarietal Vermentino and Chardonnay wines and their blends from monovarietal Airén wine and its blends with the other grape varieties, based on their higher concentrations of 3-oxo-alpha-ionol, ethyl 3-hydroxybutanoate, 1-pentanol, ethyl decanoate, diethyl malate, benzyl alcohol, ethyl octanoate, decanoic acid, ethyl hexanoate, acetovanillone, and hexanoic acid. The remaining wines cluster in the negative PC2 region due to their higher concentrations of methyl vanillate, (Z)-3-hexen-1-ol, 3-methylthio-1-propanol, and 1-heptanol.

3.3. Quantitative Descriptive Sensory Analysis

Mean values intensity of principal aroma attributes and standard deviation of studied wines is show in

Table 5. Sensory descriptive analyses of wines. Mean scores of 10 judges and standard deviations (two replicates). A + C: coupage of Airén and Chardonnay; A + V: coupage of Airén and Vermentino; C + V: coupage of Chardonnay and Vermentino; A + C + V: coupage of Airén, Chardonnay, and Vermentino.

	Airén	Chardonnay	Vermentino	A + C	A + V	C + V	A + C + V
Aroma intensity	6.98 a	6.58 a	7.86 a	6.78 a	7.42 a	7.22 a	8.00 a
	(0.99)	(0.93)	(1.11)	(0.96)	(1.05)	(1.02)	(1.13)
Fresh	6.54 a	5.68 a	7.26 a	6.11 a	6.90 a	6.47 a	7.21 a
	(0.92)	(0.80)	(1.03)	(0.86)	(0.98)	(0.91)	(1.02)
Citrus	6.58 c	n.d.	3.45 a,b	3.29 a,b	5.02 b,c	1.73 a	5.46 c
	(0.93)		(0.49)	(0.47)	(0.71)	(0.24)	(0.77)
Tropical fruit	n.d.	4.25 a,b	7.59 c,d	2.13 a	3.80 a,b	5.92 b,c	8.21 d
		(0.60)	(1.07)	(0.30)	(0.54)	(0.84)	(1.16)
Pasion fruit	n.d.	3.24 b,c	8.25 e	1.62 a	4.13 c,d	5.75 d	7.59 e
		(0.46)	(1.17)	(0.23)	(0.58)	(0.81)	(1.07)
Green apple	6.54 c	1.54 a	2.10 a	4.04 b	4.32 b	1.82 a	4.68 b
	(0.92)	(0.22)	(0.30)	(0.57)	(0.61)	(0.26)	(0.66)
Floral	2.50 a	2.00 a	6.70 c	2.25 a	4.60 b	4.35 b	5.89 b,c
	(0.35)	(0.28)	(0.95)	(0.32)	(0.65)	(0.62)	(0.83)
Sweet	1.54 a	4.35 b,c	6.54 d	2.95 a	4.04 b,c	5.45 c,d	5.64 c,d
	(0.22)	(0.62)	(0.92)	(0.42)	(0.57)	(0.77)	(0.80)

^a–d Different superscripts in the same row indicate significant differences between samples according to SNK test. n.d.: not detected.

. In order to discriminate among the means, the Student–Newman–Keuls test was employed.

Based on the results, the assessors found some variations in the aroma sensory profiles of the wines. The monovarietal wines made from the Chardonnay grape variety showed an aroma profile with fresh, tropical fruit and sweet aroma attributes with notes of citrus, green apple, and floral. Airén monovarietal wines are characterized by fresh, citrus, and green apple aromas with floral notes. The sensory profile of monovarietal Vermentino wines was characterized by fresh, tropical fruit, passion fruit, floral and sweet scents with notes of green apple and citrus.

The aroma profile of wines obtained from the blending of both monovarietal wines showed a more complex and a greater intensity in the general attributes than the monovarietal wines. Wines obtained by blending of two monovarietal wines showed aroma sensory attributes like Vermentino wines, but the intensity of these attributes was lower than in the monovarietal ones.

Finally, the aroma profile of wines made from the blending of the three monovarietal wines were the most complex of all the studied wines, because the assessors found notes from the three monovarietal wines, sometimes producing a synergistic effect and enhancing the aromatic characteristics of monovarietal wines.

4. Conclusions

The general chemical composition of monovarietal wines remained unaffected by the “coupage” technique, with all wines demonstrating enological characteristics that qualify them as quality wines. The free aroma fraction of wines from the Airén, Chardonnay, and Vermentino varieties, as well as those produced through the “coupage” technique in varying proportions, has been characterized. The free aroma fraction of monovarietal wines was marked by elevated concentrations of C₆ compounds, with 1-hexanol being the predominant compound in all instances. In monovarietal Airén and Chardonnay wines, benzenic compounds constituted the second major group of varietal aroma compounds. The volatile fraction of monovarietal Vermentino wines exhibited high concentrations of terpenes and C₁₃-norisoprenoids, classifying it as a terpene-dependent variety. Overall, the “coupage” technique applied to the studied monovarietal wines resulted in wines with an intermediate free aromatic composition between those of the monovarietal wines used in their production. Based on the results, Vermentino is a white grape variety known for its aromatic complexity, freshness, and adaptability to warm climates, making it a valuable component in blends aimed at enhancing sensory profiles and market appeal. Its cultivation is expanding in La Mancha region due to its resilience. Incorporating Vermentino into blends of monovarietal wines elaborated with traditional grape varieties from La Mancha region can offer winemakers a strategic tool to diversify their products, respond to evolving consumer preferences, and potentially increase the commercial value of their wines. This approach aligns with current trends in the wine industry that favor innovation and differentiation through blending. We therefore propose the use of the “coupage” technique for these wine varieties as a method to expand wine offerings to consumers and enhance the differentiation of our wines in both national and international markets.