3.1. Classical Enological Parameters and Antioxidant Activity
The results for the classic enological parameters and the antioxidant capacity of sparkling wines are shown in Table 1
. It can be observed that significant variations did not occur among the sparkling wines in terms of residual sugar and volatile acidity, and the values are within the limits allowed by Brazilian and OIV legislations [15
]. However, the results for relative density and dry extract of the four sparkling wines tested showed significant differences and were separated into two groups: the varietals (Chenin Blanc and Syrah), which showed the lowest values, and the blends CB+SY-W and CB+SY-R, which showed the highest values. This may be related to the lower alcohol content values presented by CB+SY-W and CB+SY-R sparkling wines. Sparkling wines generally have higher total acidity as compared to still wines (especially in the case of red wines). Chenin Blanc sparkling wine had the highest total acidity (9.68 g L−1
) and the lowest pH (3.42) (Table 1
). These results may be justified by the lower degree of maturity of the Chenin Blanc grapes at harvest. Chenin Blanc grapes presented total titratable acidity of 10.15 g L−1
(equivalent to tartaric acid), two grams per liter more than titratable acidity of the Syrah must (8.15 g L −1
) (data not shown).
The phenolic compounds are important to the sensorial because they contribute to the astringency, bitterness, and color; in addition, they present bioactive activity, are responsible for several beneficial effects for health [1
]. The direct relation between phenolic composition and antioxidant capacity of the sparkling wines can be observed in the CB+SY-R sparkling wine (Table 1
), which had higher total polyphenols concentration (190.2 mg L−1
) and antioxidant capacity (DPPH = 0.90 mM TEAC L−1
). Studying commercial wines from SFV, Padilha et al. [1
] evidenced that the antioxidant capacity, determined also by DPPH and ABTS, influenced each individual wine phenolic compounds, which explains the variation of the antioxidant capacity observed in the present study. These total polyphenols values are higher than those found by Caliari et al. [14
], studying Moscato Giallo sparkling wines (variation between 88.0 mg L−1
and 95.7 mg L−1
) in the South of Brazil. The highest concentration of total phenolic compounds in the CB+SY-R sparkling wine can be justified by the pre-fermentative maceration occurred. In a study with Spanish sparkling wines with Pedro Ximenez variety, Ruiz-Moreno et al. [23
] also observed higher concentration of total polyphenols in the sparkling wine whose must has been pre-fermentative macerated. In the same way, the absorption at 420 nm (yellow) was higher for the CB+SY-R sparkling wine.
3.2. Volatile Composition
A total of 33 volatile compounds were tentatively identified and first time reported in the sparkling wines produced by the traditional method in SFV (Table 2
). The values of the calculated LTPRI and the LTPRI from literature, as well as the aromatic descriptors of each compound are also shown in Table 2
Differences lower than or equal to 15 units between the calculated LTPRI and LTPRI values of the literature were accepted for the tentative identification process of the compounds. It can be noted that from 33 compounds identified in the headspace, 11 are higher alcohols, 13 volatile esters, five carboxylic acids, and four belong to distinct chemical classes: one terpene, one sulfurated, one aldehyde and one phenol (Table 2
). The quantity of volatile compounds identified in the sparkling wines from SFV is similar to findings in previous studies carried out in other countries, where monodimensional gas chromatography was also used. Wang et al. [24
] identified 26 aromatic compounds in the headspace of Chenin Blanc wines from China, with esters representing the highest number of compounds, while Chin et al. [25
] found 35 volatile compounds in Australian Shiraz wines.
The volatile compounds identified in the four traditional sparkling wines from SFV are shown in Table 3
. It can be observed that 8 compounds had a normalized chromatographic area of ≥ 1:3 alcohols (3-methyl-1-butanol, 2,3-butanediol, 2-phenylethanol), three esters (ethyl octanoate, diethyl butanedioate, 2-phenyl ethyl acetate), and two carboxylic acids (hexanoic and octanoic).
According to von Muhlen et al. [22
], these data contribute to the tentative identification of volatile compounds in wines.
Higher alcohols are secondary aromatic compounds originating from the fermentation process. They are produced from sugars and amino acids during alcohol fermentation and include aliphatic and aromatic compounds, which can positively or negatively influence the wine aroma [14
]. The compound 3-methyl-1-butanol (aroma of solvent, chemical) was the alcohol with greatest normalized chromatographic area, regardless the grape variety used in the sparkling wine production. High values of this compound were also found by Santos et al. [34
], and Wang et al. [24
] in Chenin Blanc wines. Ubeda et al. [35
] reported also high values of 3-methyl-1-butanol in Chilean sparkling wines. However, Condurso et al. [36
] noted that this compound has a high perception threshold. Other alcohols, such as 2-phenylethanol (aroma related to honey and flowers) and 2,3-butanediol (fruity aroma) were also found in the sparkling wines from SFV, but without significant differences among the four sparkling wines analyzed (Table 3
). According to Ferreira et al. [37
], 2-phenylethanol is considered one of the most important aromatic alcohols in terms of wine sensory quality. It was the second highest volatile compound identified in the traditional sparkling wines from SFV, regardless the variety used.
The hexan-1-ol (herbaceous flavour), a compound formed by linoleic and linolenic acids degradation in the pre-fermentative stage [14
], was also found in the sparkling wines from SFV. Its presence ranged from 0.166 (Syrah sparkling wine) to 0.550 (CB+SY-R sparkling wine) (Table 3
). Significant quantities of this alcohol were also observed by Wang et al. [38
] in rosé sparkling wines produced through the traditional method in Australian. Among the other alcohols identified in the sparkling wines from SFV, presence of 3-ethoxypropan-1-ol (particularly in the Chenin Blanc sparkling wine) can be highlighted, despite the normalized chromatographic area low (0.047). This compound can contribute to the volatile composition of sparkling wines with fruity aroma.
Esters contribute to sensory attributes of wines, mainly in relation to floral and fruity aromas [12
]. The concentrations of these esters are influenced by multiple factors, including yeasts, temperature of fermentation, aeration degree during alcoholic fermentation, and sugar concentration [6
]. A notable ester was diethyl succinate (fruity aroma), which presented higher chromatographic area in the Chenin Blanc sparkling wine (Table 3
), which suggests that this compound is one of the most relevant esters for the volatile profile in SFV. This compound was the third most important in rosés sparkling wines from Australia [38
], and concentrations ranged from 3.9 μg L−1
to 10,000 μg L−1
. However, Wang et al. [24
] noted that diethyl succinate was one of the lowest ester compounds in Chenin Blanc wines in China.
The compounds 2-phenylethyl acetate and ethyl octanoate contribute to the floral and fruity aroma, respectively, and they were also found in the sparkling wines produced in the SFV. 2-phenylethyl acetate was found with the highest area in the Chenin Blanc sparkling wine (Table 3
). Isoamyl, hexyl and cis
-3-hexen-1-ol acetates were present in high chromatographic areas in Syrah sparkling wine, while Chenin Blanc showed higher chromatographic areas of ethyl decanoate, diethyl pentanedioate and diethyl malate (Table 3
). In relation to the esters ethyl butanoate and ethyl hexanoate, no difference was found between the four sparkling wines analyzed.
Carboxylic acids are produced during alcohol fermentation and may have different origins. The hexanoic, octanoic, and decanoic acids can also be formed during the catabolism of the long chain fatty acids [6
]. Depending on the concentration, these acids are related to a decrease in the sensory quality of wines [9
]. Shinohara [39
] showed that in concentrations of 4 to 10 mg L−1
the C6 to C10 acids contribute to an agreeable wine aroma, while in concentrations above 20 mg L−1
they have a negative impact on the organoleptic quality of wines.
The sparkling wines produced by traditional method in the SFV presented higher normalized chromatographic areas for octonoic, hexanoic and n-decanoic acids (the last on was higher in CB+SY-R sparkling wines, as shown in Table 3
). The high chromatographic areas of these acids may be related to two alcoholic fermentations that sparkling wines elaborated by traditional methods have undergone. Welke et al. [8
] observed an increase of the chromatographic area for almost all the acids identified in the volatile profile of base wines and their resulting sparklings.
Sulphur compounds are originated from fermentative process contributing to the aromatic complexity of the wines, when present in low concentrations. However, in high concentrations, they may be responsible for unpleasant aromas [40
]. As reported in Table 3
, the 3-(methylthio)-1-propanol was identified in low normalized chromatographic areas in the sparkling wines produced in the SFV (ranging from 0.027 to 0.031).
Aldehydes are formed from decarboxylation of unsaturated fatty acids and they can also be considered as products of lipoxygenase catalysis [41
]. The presence of benzaldehyde was statistically higher in the Syrah sparkling wine, as compared to the others. But in general, the chromatographic areas was lower than 0.4 in the headspace for all the sparkling wines of the SFV (Table 3
The volatile phenols can have a negative effect on the global aroma of wines, providing aromas described as “animal”, “horse sweat”, “leather”, or “medicinal”. However, in low concentrations they contribute to increasing the aroma complexity [9
]. The presence of this type of volatile compound in the sparkling wines of the SFV was discrete, ranging from 0.051 (Chenin Blanc and CB+SY-W) to 0.067 (Syrah) in the chromatographic area (Table 3
The terpenes are responsible for the younger and floral aromas of wines and they are related to the varietal aromas of certain groups of varieties, mainly muscats [8
]. In this study, the only terpene that was tentatively identified was carvone, which presented the highest normalized chromatographic area in CB+SY-W and Chenin Blanc sparkling wines (Table 3
). Despite being related to varietal aromas, terpenes are not frequently identified in wines from Chenin Blanc and Syrah varieties. Wang et al. [24
] found two terpenes in Chenin Blanc wines and Zang et al. [42
] identified four in Syrah wines.
In order to link volatile compounds and identify main parameters contributing to discriminate four different sparkling wines from SFV, principal component analysis (PCA) was applied in the average of three replicates of the results obtained with 1D-GC/qMS (Table 3
), from each one of the four sparklings evaluated. The PCA (Figure 1
) showed that two PCs explained 81.57% of total variability of the data, separating the sparkling wines samples according to the grape varieties and blends used.
The first principal component (PC1) explained 60.19% of the total variability from GC-MS data, separating the sparkling wines produced from Chenin Blanc, located in the positive side of the X
-axis, from the Syrah sparkling wine located in the negative side of the X
-axis (Figure 1
). It can be observed that Chenin Blanc sparkling wines were characterized principally by the volatile compounds 1,3-butanediol (Bt13), 2,3-butanediol (Bt23), 3-ethoxypropan-1-ol (Etp), 2-phenylethyl acetate (Ph2ac), diethyl succinate (Dsuc), diethyl pentanedioate (Dpen), ethyl decanoate (Edec), ethyl butanoate (Ebut), diethyl malate (Dmal), 3-methyl-1-butanol (M3b), and 2-phenylethanol (Ph2ol), which present, especially, the floral and fruity aromatic descriptors. Syrah sparkling wines were characterized by the compounds benzaldehyde (Bnz), butanoic acid (Bac), phenol (Phen), isoamyl acetate (Isa), octanoic acid (Oac), cis-3-hexen-1-ol acetate (Cis3h), ethyl hexanoate (Ehex), (z)-3-hexen-1-ol (Hex3) and hexyl acetate (Hact), whose aromatic descriptors are sweet, buttery, cheese, fruity, vegetal, oily, cherry, and pear.
The second principal component (PC2) explained 21.38% of the data variability and grouped CB+SY-W and CB+SY-R sparkling wines in the negative side of the Y-axis, separated from the other two varietal wines (Syrah and Chenin Blanc), located in the positive side of Y-axis. CB+SY-W and CB+SY-R sparkling wines were characterized by the compounds 3-(methylthio)-1-propanol and 3-methyl-1-pentanol. These results showed that blending two varieties, even different wines, one white and other rosé, volatile profile of the blends were similar and could not be distinguished.
In this study, the volatile compounds present in sparkling wines produced in the SFV using the traditional method, with the two most important varieties in the region, were determined and reported for the first time. The wines presented different characteristics whose volatile compounds allowed to discriminate between samples with specific typicality of each wine to be preliminarily described. In the next step of this research, quantitative analysis should be carried out as well as the determination of the odor activity value (OAV). In addition, the correlation of the data obtained from sensory analysis should allow improving the information obtained and better describe the sparkling wines produced by the traditional method in the SFV.