Chemical typicity of tropical tannat red wines from sub-middle São Francisco Valley, Brazil

Abstract

Tannat is a Vitis vinifera cultivar with typically high phenolic compound contents, showing intense coloration, well-bodied, and great aging potential. However, even with this great potential, this variety is still commercially underexplored in the Sub-middle São Francisco Valley (SSFV). This work aimed to characterize the typicity of Tannat red wines from Sub-middle São Francisco Valley (SSFV), Brazil. In addition, the present work represents the first study featuring phenolic compounds quantification and antioxidant activity of Tannat in tropical climate wine-producing regions. Considering the condition of a short-applied maceration time during the winemaking, the tropical Tannat wine showed significant antioxidant activity and high phenolic contents. Trans-caftaric, malvidin-3-O-glucoside, and procyanidin B1 stood out among the phenolic compounds quantified, presenting Tannat with the potential to be an important grape variety to tropical wine-producing regions in Brazil, containing high contents of bioactive compounds. Previously results to compounds (−)-epigallocatechin gallate, procyanidin B2, quercetin-3-β-D-glucoside, pelargonidin-3-O-glucoside, chlorogenic acid, and piceatannol were not found in Tannat wines. Further studies are necessary to make the Tannat grape’s adaptation better in tropical climate conditions, including investigating the phenolic profile and antioxidant activity of Tannat red wines with longer maceration times during the winemaking.

Graphical abstract

Introduction

Sub-middle São Francisco Valley (SSFV) is a recent wine-producing region in Northeast Brazil, with a tropical semi-arid climate and Caatinga biome, without the traditional well-defined occurrence of four seasons. Then, the terroir is composed of geographic characteristics such as high insolation (3000 sunny hours year⁻¹), low annual rainfall (500 mm), high average temperature (26 °C), relative moisture of 60%, and altitude of 350 m (Embrapa 2017). These features associated with the irrigation system and applied intervention technologies in the vineyard, permit more than two harvests per year and the production of full-bodied red wines, with a high concentration of phenolic compounds and values of antioxidant activity (Alves Filho et al. 2019). Syrah is the most commercially important wine grape to SSFV, however, few commercially explored grape varieties may present adaptation and growth potential, such as Tannat. This cultivar is one of the red grape varieties of Vitis vinifera with the highest anthocyanins and other phenolic compounds concentration, traits great to blend with other wines, enhancing the phenolic profile and antioxidant activity, as well as, sensory complexity, providing mainly more color intensity, structure, body, and aging potential to the beverage (Varela and Gámbaro 2006). This French variety is the principal grape of Uruguayan viticulture, which makes it known as the emblematic wine of Uruguay.

Extraordinary values of phenolics have been reported to Tannat, as total phenolic contents of 4410 mg GAE L⁻¹ (Pazzini et al. 2015), while in general the mean of total phenolics in red wines around 2000 mg GAE L⁻¹ (Waterhouse et al. 2016). Also, the name of Tannat is derived from the word “tannin”, due to its richness in phenolic compounds, which provide health benefits for the consumers and outstanding sensorial traits, such as color, structure, body, and stability (Varela and Gámbaro 2006; Vidal et al. 2018; Waterhouse et al. 2016). The phenolic compounds in red wines, both flavonoids (flavonols, monomeric flavanols and tannins, and anthocyanins), and non-flavonoids (phenolic acids and stilbenes), may be related to high antioxidant capacity and cardiovascular disease reduction. Therefore, the phenolic composition is an important parameter of red wines, especially in new regions. Then, this helps in understanding the geographic contribution of the region and provides the necessary knowledge to those producers to make decisions concerning new products potential and possible agronomic and oenological interventions.

Considering the possible projection that Tannat may assume, this research aimed to analyze, for the first time, the phenolic typicity and antioxidant potential of Tannat to produce tropical red wines in Sub-middle São Francisco Valley, Brazil, by comparing it with Syrah, the better-adapted variety in this region.

Material and methods

Raw material

Tannat and Syrah grapes were collected from vineyards diagrammed in Vertical Shoot Position (VSP) training system, rootstock Paulsen 1103, and irrigated per drip scheme. Tannat vineyards were planted in 2000, in the Mandacaru experimental vineyard at Juazeiro, Bahia, Brazil (latitude: 9° 24′ S, longitude 40° 26′ W, height 375.5 m). Pruning was performed on July 29th, 2019, and grapes were harvested on December 9th, 2019, about 133 days after pruning (DAP). Syrah vineyards were planted in 2013, in Bebedouro, an experimental field at Petrolina, Pernambuco, Brazil (latitude: 9° 9′ S, longitude 40° 22′ W, height 365.5 m). Pruning was carried out on August 9th, 2019, and the grapes were harvested on December 10th, 2019, with about 123 days DAP. Tannat (51 kg) and Syrah (49 kg) were received and processed on the same day in the Laboratory of Enology of Embrapa Semiárido, Petrolina, Pernambuco, Brazil.

Winemaking

Potassium metabisulfite (0.1 g L⁻¹, Synth, São Paulo, Brazil), pectinolytic enzyme (0.03 g L⁻¹ Endozym rouge, AEB–Brescia, Italy), dry yeasts (0.2 g L⁻¹, Saccharomyces cerevisiae bayannus–Mauvirim PDM, Amazon Group, Monte Belo do Sul, RS, Brazil), and fermentation activator (0.2 g L⁻¹, Gesferm plus, Amazon Group) were applied as enological inputs.

Initially, the grapes were weighed, destemmed, and treated with potassium metabisulfite and enzyme. Then, the musts were placed in 20 L glass bottles, capped with glass valves of Müller airlock-type. Subsequently, the yeasts were inoculated to start the alcoholic fermentation (AF) under a controlled temperature of 24 ± 2 °C. AF and maceration evolution were monitored daily with density using an electronic hydrostatic balance (Super Alcomat, Gibertini, Milano, Italy). The wine pressing was performed after 96 h and AF completion (approximately 10 days) was determined with constant density lower than 0.999, confirmation of the alcoholic grade (≥ 11.6% v/v), and total reducing sugars content (≤ 2.7 g L⁻¹). The spontaneous malolactic fermentation was conducted at 18 ± 2 °C until all malic acid was converted to lactic acid. Its completion was determined through chromatography of malic acid paper. The stabilization was performed with cold storage (0 °C) for 20 days and with the addition of 400 mg L⁻¹ of a mixture of the arabic gum with the metatartaric acid stabilizer Stabigum® (AEB Group, Viseu, Portugal). The free sulfur dioxide content of the wines was adjusted to 50 mg L⁻¹. The wines were bottled (750 mL), corked, and stored in the cellar at 18 °C for 6 months until the analysis was accomplished.

Oenological classic parameters – physicochemical and color analyses

Classic oenological parameters of wines were determined by pH, using pHmeter (Hanna PAT. CPNQ Edge, Romênia); titratable acidity (TA) using NaOH 0.1 N as titrator, pH 8.2 as the turning point and expressing the result in tartaric acid (g L⁻¹); volatile acidity determined for steam distillation, using oenological distiller (Super Dee–Gibertini, Milano, Italy) and results expressed in acetic acid (g L⁻¹); density and dry extract using an electronic hydrostatic balance (Super Alcomat, Gibertini, Milano, Italy), expressed in g mL⁻¹ and g L⁻¹, respectively; alcohol content percentage using the same oenological distiller and electronic hydrostatic balance (OIV 2021). Total reducing sugars were determined using the Eynon Lane titratable method and the results were expressed in g L⁻¹ (Ribéreau-Gayon et al. 1980). Total phenolic index (TPI) was also performed (Harbertson and Spayd 2006), using a UV–Vis spectrophotometer (Thermo Fisher Scientific Oy Ratastie 2, FI-01620 Vantaa, Finland), at 280 nm wavelengths.

The wine’s color intensity (CI) was determined by the sum of the readings in the wavelengths 420, 520, and 620 nm using a spectrophotometer (Thermo Fisher Scientific Oy Ratastie 2, FI-01620 Vantaa, Finland) and the tonality by the reason among the readings in the 420 and 520 nm (Glories 1984).The color was performed in the colorimeter (HunterLab ColorQuest-XE, Virginia, USA) coupled with EasyMatch QC 4.81 software, in the transmittance mode, excluded specular, illuminant D65 and 10° observer angle (CIE 2004), using the CIELab and CIEL*C*h systems, to determine L* (luminosity), a* (red-green coordinate), b* (yellow-blue coordinate), C* (Chroma), and h (hue angle).

Bioactive contents – total phenolic and total monomeric anthocyanins

The content of total phenolic compounds was determined following Rufino et al. (2010). The content of phenolic compounds was quantified by reading the absorbance at 700 nm wavelengths in a spectrophotometer (Shimadzu Corporation, UV-1800, Japan), expressing results in mg L⁻¹ of the gallic acid equivalent of wine (mg GAE L⁻¹). Monomeric anthocyanins were determined according to buffer solutions (pH 1.0; 4.5) method (Lee et al. 2005), and the readings were performed at 520 nm and 700 nm in a spectrophotometer (Shimadzu Corporation, UV 1800, Japan).

Quantification of individual phenolic compounds by HPLC–DAD-FD

The phenolic compounds were quantified by High-Performance Liquid Chromatography (HPLC–DAD-FD), according to methods validated under the same analytical conditions (Da Costa et al. 2020; Natividade et al. 2013), using a chromatograph (Waters model Alliance e2695, USA) coupled simultaneously to the Diodes Array Detectors–DAD (280, 320, 360, and 520 nm) and Fluorescence–FD (280 nm excitation and 320 nm emission), Gemini-NX C18 analytical column (150 mm × 4.60 mm × 3 μm) and the Gemini-NX C18 security guard cartridge (4.0 mm × 3.0 mm), both from Phenomenex (Torrance, USA). 28 phenolic compounds were quantified in wines: malvidin-3-O-glucoside, cyanidin-3-O-glucoside, petunidin-3-O-glucoside, delphinidin-3-O-glucoside, peonidin-3-O-glucoside, and pelargonidin-3-O-glucoside (anthocyanins), gallic, caffeic, trans-caftaric, chlorogenic, ρ-cumaric and ferulic acids (phenolic acids), quercetin 3-β-D-glucoside, rutin, myricetin, kaempferol-3-O-glucoside and isorhamnetin-3-O-glucoside (flavonols), trans-resveratrol, cis-resveratrol, and piceatannol (stilbenes), (+)–catechin, (−)–epicatechin, (−)–epigallocatechin gallate, (−)–epicatechin gallate, procyanidins A2, B1 and B2 (flavanols and condensed tannins). Employing gradient elution, the mobile phase consisted of a 0.85% solution of orthophosphoric acid (Fluka, Switzerland) in ultra-pure water (Purelab Option Q Elga System, USA) as phase A, and acetonitrile HPLC grade (J. T. Baker, USA) as phase B, totaling 60 min of running. The oven temperature was maintained at 40 °C and the flow at 0.5 mL min⁻¹. The wine was injected without dilution in the equipment, after filtration in a 13 mm diameter nylon membrane and 0.45 µm pore size (Phenomenex®, USA), using 10 µL per sample as the injection volume.

The ferulic acid standard was obtained from ChemService (West Chester, USA). The caffeic, trans-caftaric, ρ-coumaric, chlorogenic and gallic acids, and piceatannol were acquired from Sigma-Aldrich (USA). The (−)-epicatechin gallate, (−)-epigallocatechin gallate, (+)-catechin, (−)-epicatechin, procyanidins A2, B1, B2, kaempferol-3-O-glucoside, quercetin 3-β-D-glucoside, isorhamnetin-3-O-glucoside, rutin, malvidin-3-O-glucoside, petunidin-3-O-glucoside, peonidin-3-O-glucoside, pelargonidin-3-O-glucoside, delphinidin-3-O-glucoside, and trans-resveratrol standards were obtained from Extrasynthese (France); and the cis-resveratrol was acquired from Cayman Chemical (Michigan, USA).

Antioxidant capacity

The in vitro antioxidant capacity was determined using the FRAP and ABTS methods, following Rufino et al. (2010). FRAP (ferric reduction method) readings were performed with 595 nm and results were expressed in mmol ferrous sulfate L⁻¹ of the sample. ABTS (2,2-azino-bis (3-eth- ylbenzthiazoline-6-sulphonic acid)) results were expressed in mmol Trolox Equivalent Antioxidant Capacity (TEAC) L⁻¹ of the sample, with readings at 743 nm. Both analyses used a spectrophotometer (Shimadzu Corporation, UV-1800, Japan).

Statistical analysis

Each replicate of vinification of the Tannat and Syrah red wines was analyzed using three different bottles in triplicate. All data were evaluated by the analyses of variance (one-way ANOVA) using the R Studio Desktop program (1.4.1106 version, Boston, USA) to statistically certify the equality or differences among the results (p ≤ 0.05). Shapiro–Wilk, Levene, and Student’s t-Test (p ≤ 0.05) were applied to test the means’ normality, variance homogeneity, and the comparison, respectively.

Results and discussion

Wine musts parameters

Tannat and Syrah musts presented 3.71 and 3.70 of pH; titrable acidity (TA) of 5.80 and 6.90 g L⁻¹; 1.0890 and 1.0965 g mL⁻¹ of density; soluble solids of 21.34 and 23.03° Brix; 212.94 and 225.76 g L⁻¹ of reducing sugars.

Classic parameters

The results of the classic parameters are presented in Fig. 1. All quality parameters (total acidity, total reducing sugars, alcohol, and volatile acidity) are following Brazilian current legislation to table dry wines (Brasil 2004; Brasil 2010). The pH and titratable acidity (TA) presented consistent and inversely proportional results, that is, 4.06 and 3.85 for pH; 4.77 and 5.07 g L⁻¹ for TA, concerning Tannat and Syrah, respectively. According to the literature, typical values of pH and TA in red wines ranged 3.3–3.7 and 5–8 g L⁻¹, respectively (Jackson 2014; Waterhouse et al. 2016). Uruguayan commercial Tannat wines were reported with a pH of 3.39 (Valentin et al. 2020). Also, these authors presented similar pH results for Uruguayan Tannat (3.39), Argentinian Malbec (3.37), Chilean Carménère (3.38), and Brazilian (Southern) Merlot (3.37) wines, which may indicate few influences of the grape variety in the pH values. Thus, this parameter is possibly more influenced by the similarities of climatic conditions of these regions and distinct from tropical climate regions, as the Sub-middle São Francisco Valley (SSFV).

Fig. 1.

Physicochemical analyses of tropical Tannat and Syrah red wines from Sub-middle São Francisco Valley, Brazil. Means with asterisks differ by Student’s t-Test ‘*’(p ≤ 0.05) ‘**’(p ≤ 0.01)

Thus, in SSFV the intense temperature and sunlight exposure, and the high levels of potassium in the soil (Albuquerque et al. 2009; Oliveira et al. 2018) may be responsible for the high pH and low acidity obtained in the Tannat and Syrah red wines (Fig. 1). The heat may increase plant respiratory activity and maturation reactions, harming the organic acid accumulation. Furthermore, in this present research, these climatic conditions are related to the phenological shorter cycle of grapes (133 DAP to Tannat), compared with temperate wine-producing regions, which have the four seasons well-defined and grapes’ harvest once per year. Additionally, the high potassium in soil enhances the potassium in the wine, decreasing free tartaric acid by the precipitation with potassium forming potassium bitartrate, and consequently decreasing acidity and increasing the pH of the beverage (Oliveira et al. 2018).

Color intensity (CI) and TPI results were consistent with each other (Fig. 2). As expected, Tannat presented considerably higher levels of CI and TPI than Syrah, due to the varieties’ traits. Also, lower luminosity and higher chromaticity (Fig. 2d and g, respectively) confirm Tannat’s stronger color depth, while a* and b* showed the lower feature of redness and yellowness of Syrah. In complement, the hue angle (h) shows Tannat closer to redness than Syrah. However, lower values of L* (16.67) in commercial Tannat wines (Valentin et al. 2020) and higher levels of CI (around 9.5–20.5) (González-Neves et al. 2014) in experimental Tannat wines with 8 days of maceration (192 h), were reported. These results indicate that higher maceration time during the winemaking possibly will be induced to the major extraction of pigments and intensity of color in the Tannat wine from the SSFV.

Fig. 2.

Total phenolic index and color measurements of tropical Tannat and Syrah red wines from Sub-middle São Francisco Valley, Brazil. Means with asterisks differ by Student’s t-Test ‘*’(p ≤ 0.05) ‘**’(p ≤ 0.01)

Phenolic compounds

Flavanols

The monomeric flavanols and proanthocyanidins (condensed tannins) contents of the red wines analyzed are shown in Table 1, where the total quantified varied from 43.02 to 65.83 mg L⁻¹ for Syrah and Tannat wines, respectively. Significant differences were observed in most compounds. The monomeric flavanols and proanthocyanidins quantified in the greatest composition were procyanidin B1, followed by (+)-catechin, and procyanidin B2. Tannat presented higher values to (+)-catechin (11.94 mg L⁻¹), procyanidin A2 (2.23 mg L⁻¹), procyanidin B1 (28.95 mg L⁻¹), and procyanidin B2 (9.17 mg L⁻¹), except for (−)-epigallocatechin gallate, that Syrah presented higher content (4.77 mg L⁻¹).

Table 1.

Phenolic compounds in Tannat and Syrah tropical red wines from Sub-middle São Francisco Valley, Brazil

Phenolic compounds (mg L−1)1,2	Tannat wine	Syrah wine
Flavanols
(+)-Catequin	11.94 ± 0.69**	9.79 ± 0.56
(−)-Epicatechin	8.04 ± 0.82	6.95 ± 1.41
(−)-Epicatechin gallate	2.44 ± 0.47	2.25 ± 0.16
(−)-Epigallocatechin gallate	3.07 ± 0.52	4.77 ± 0.18**
Procyanidin A2	2.23 ± 0.62**	1.09 ± 0.28
Procyanidin B1	28.95 ± 1.15**	12.14 ± 0.21
Procyanidin B2	9.17 ± 0.49**	6.04 ± 0.17
Total flavanols	65.84 ± 3.71**	43.03 ± 1.94
Flavonols
Kaempferol-3-O-glucoside	0.97 ± 0.09	3.25 ± 0.44**
Quercetin 3-β-D-glucoside	4.66 ± 0.17	25.74 ± 1.29**
Isorhamnetin-3-O-glucoside	2.44 ± 0.18	15.35 ± 0.92**
Myricetin	0.56 ± 0.04	0.52 ± 0.05
Rutin	1.11 ± 0.03	1.1 ± 0.16
Total flavonols	9.74 ± 0.3	45.96 ± 2.71**
Anthocyanins
Malvidin-3-O-glucoside	72.49 ± 1.22**	18.07 ± 0.6
Pelargonidin-3-O-glucoside	7.37 ± 0.17**	0.56 ± 0.02
Cyanidin-3-O-glucoside chloride	0.3 ± 0.04	0.21 ± 0.01
Delphinidin-3-O-glucoside	2.13 ± 0.06	ND
Petunidin-3-O-glucoside	0.84 ± 0.03**	0.49 ± 0.02
Peonidin-3-O-glucoside	0.94 ± 0.0377	1.47 ± 0.03**
Total anthocyanins	84.07 ± 1.43**	20.8 ± 0.65
Phenolic acids
Gallic acid	11.77 ± 0.42**	6.15 ± 0.29
Ferulic acid	0.33 ± 0.01	0.59 ± 0.01**
ρ-Coumaric acid	4.38 ± 0.17	21.11 ± 0.8**
Caffeic acid	8.31 ± 0.21	25.77 ± 0.45**
trans-Caftaric acid	298.78 ± 1.42	523.69 ± 4.24**
Chlorogenic acid	0.83 ± 0.04	0.94 ± 0.07**
Total phenolic acids	324.40 ± 4.7**	578.25 ± 4.83**
Stilbenes
trans-Resveratrol	0.27 ± 0.01	0.29 ± 0.01**
cis-Resveratrol	0.46 ± 0.01	0.63 ± 0.01**
Piceatannol	0.37 ± 0.01**	0.29 ± 0.01
Total stilbenes	1.10 ± 0.01	1.21 ± 0.01**
Total phenolic compounds3	1212.87 ± 57.98**	596.85 ± 33.85**
Total monomeric anthocyanins4	151.54 ± 5.3**	69.08 ± 5.43**

¹Means followed by asterisks differ by Student’s t-Test ‘*’(p ≤ 0.05) ‘**’(p ≤ 0.01). ²ND = not detected. ³Total phenolic compounds results expressed in mg GAE L⁻¹, using the spectrophotometric method and Folin Ciocateau reagent (Rufino et al. 2010). ⁴Total monomeric anthocyanins result expressed in malvidin-3-O-glucoside mg L⁻¹, as in Lee et al. (2005)

Valentin et al. (2020) characterized phenolics of 14 commercials Uruguayan Tannat wines, obtaining (+)-catechin (20.19 mg L⁻¹), and (−)-epicatechin (19.1 mg L⁻¹) as the flavanols quantified (Table 2). These contents were higher than presented in this research, probably due to the low maceration time applied (96 h), which justifies lower values herein presented. Young red wines are commonly pressed after five days (120 h) of maceration during alcoholic fermentation (Jackson 2014). In this sense, surprising contents of (+)-catechin (43 mg L⁻¹) and (−)-epicatechin (65 mg L⁻¹), in Tannat wines from Southern Uruguay, with 15 days of maceration were reported (Boido et al. 2011). Phenolic data from Syrah musts from SSFV evaluated every 5 days during 30 days of maceration have been reported (Alencar et al. 2018). With 5 days of vinification, only (−)-epigallocatechin gallate (5.6 mg L⁻¹) presented higher values than Syrah and Tannat wines from the present research, whereas (+)-catechin (4.5 mg L⁻¹), (−)-epicatechin (1.0 mg L⁻¹), (−)-epicatechin gallate (6.2 mg L⁻¹), procyanidin A2 (0.3 mg L⁻¹), procyanidin B1 (3.4 mg L⁻¹), and procyanidin B2 (4.6 mg L⁻¹) presented lower values.

Table 2.

Comparative results of the quantification of phenolic compounds in tropical Tannat red wine from Sub-middle São Francisco Valley, Brazil, and Tannat red wines from other wine-producing regions

Phenolic compounds1	Brazilian Tannat wines		Uruguayan Tannat wines
	SSFV2	De Andrade et al. (2013)3	Valentin et al. (2020)	Vidal et al. (2018)	Boido et al. (2011)	Favre et al. 2014)
Flavanols
(+)-Catequin	11.94 ± 0.69	–	20.19 ± 1.94	48.8 ± 13.7	43 ± 6	0.80 ± 0.16
(−)-Epicatechin	8.04 ± 0.82	–	19.10 ± 1.20	36.3 ± 14.9	65 ± 7	–
(−)-Epicatechin gallate	2.44 ± 0.47	–	–	4.7 ± 2.4	–	–
(−)-Epigallocatechin gallate	3.07 ± 0.52	–	–	–	–	–
Procyanidin A2	2.23 ± 0.62	–	–	–	–	–
Procyanidin B1	28.95 ± 1.15	–	–	–	–	0.61 ± 0.02
Procyanidin B2	9.17 ± 0.49	–	–	–	–	–
Procyanidin-dimmer-B3	–	–	–	–	–	1.48 ± 0.42
Procyanidin-dimmer-C1	–	–	–	–	–	1.49 ± 0.05
Flavonols
Kaempferol-3-O-glucoside	0.97 ± 0.09	-	3.86 ± 0.40	-	-	-
Quercetin 3-β-D-glucoside	4.66 ± 0.17	–	–	–	–	–
Isorhamnetin-3-O-glucoside	2.44 ± 0.18	–	–	2.7 ± 1.9	–	–
Myricetin	0.56 ± 0.04	–	16.18 ± 1.49	5.0 ± 3.3	–	–
Rutin	1.11 ± 0.03	–	6.70 ± 0.58	–	–	–
Quercetin	–	–	7.21 ± 0.69	3.0 ± 2.1	–	1.60 ± 0.13
Anthocyanins
Malvidin-3-O-glucoside	72.49 ± 1.22	8.34–86.5	56.31 ± 6.94	70.7 ± 48.5	470 ± 36	–
Pelargonidin-3-O-glucoside	7.37 ± 0.17	–	–	–	–	–
Cyanidin-3-O-glucoside	0.3 ± 0.04	7.14–7.99	1.80 ± 0.26	0.9 ± 0.8	14 ± 1	–
Delphinidin-3-O-glucoside	2.13 ± 0.06	6.32–16.4	6.03 ± 0.65	5.3 ± 4.4	98 ± 8	–
Petunidin-3-O-glucoside	0.84 ± 0.01	14.8–18.2	6.73 ± 0.89	13.7 ± 10.9	106 ± 13	–
Peonidin-3-O-glucoside	0.94 ± 0.04	6.49–14.6	8.48 ± 1.27	5.4 ± 4.4	27 ± 3	–
Phenolic acids
Gallic acid	11.77 ± 0.42	–	15.20 ± 1.65	84.1 ± 38.9	86 ± 11	5.13 ± 0.48
Ferulic acid	0.33 ± 0.01	–	2.93 ± 0.29	–	–	–
ρ-Coumaric acid	4.38 ± 0.17	–	–	92.0 ± 32.2	30 ± 22	–
Caffeic acid	8.31 ± 0.21	–	6.46 ± 0.56	–	–	–
cis-Caftaric acid	–	–	–	110.0 ± 45.0	48 ± 39	–
trans-Caftaric acid	298.78 ± 1.42	–	–	49.2 ± 70.4	41 ± 25	10.85 ± 1.57
Chlorogenic acid	0.83 ± 0.04	–	–	–	–	–
Stilbenes
trans-Resveratrol	0.27 ± 0.01	–	–	–	–	0.26 ± 0.01
cis-Resveratrol	0.46 ± 0.01	–	–	–	–	0.38 ± 0.03
Piceatannol	0.37 ± 0.01	–	–	–	–	–

¹Phenolic compounds expressed in mg L⁻¹. ²Wines from Sub-middle São Francisco Valley are analyzed in the present study. ³Wines from Vale dos Vinhedos localized in the Brazilian South region with temperate climate conditions

(−)-Epicatechin and procyanidin B2 were reported as the principal flavanols presented in skins and seeds of Syrah grapes in SSFV (Oliveira et al. 2019). Also, procyanidin B2 and, procyanidin B1 as (+)-catechin were reported as the major flavanols present in commercial Vitis vinifera red wines from this region (Padilha et al. 2017). The finding procyanidin B1 content presented surprising results in the Tannat tropical wine. A Uruguayan Tannat approach has shown a strongly lower value (0.61 mg L⁻¹) to procyanidin B1 (Favre et al. 2014), in comparison with the Tannat from SSFV (28.95 mg L⁻¹). Procyanidins, such as B1 and B2, are strongly related to astringency perception (Waterhouse et al. 2016) and antioxidant activity in SSFV red wines (Alencar et al. 2018).

Anthocyanins

Table 1 provides the monomeric anthocyanins amounts. Total anthocyanins by HPLC–DAD-FD presented a huge difference between the varieties, being 84.07 mg L⁻¹ to Tannat and 20.80 mg L⁻¹ to Syrah wines. In agreement, Tannat presented quite higher total monomeric anthocyanins quantified by spectrophotometry method than Syrah, about 151.54 and 69.08 mg L⁻¹, respectively. These results presented the same behavior as CI, TPI, and colorimetry, with Tannat having a deeper color, shown in Fig. 2. In an approach with Uruguayan red wines, Tannat also presented higher total monomeric anthocyanins than Syrah (González-Neves et al. 2016).

Regarding individual anthocyanins, Tannat showed greatly higher results than Syrah to malvidin-3-O-glucoside (72.49 mg L⁻¹), pelargonidin-3-O-glucoside (7.37 mg L⁻¹), cyanidin-3-O-glucoside (0.3 mg L⁻¹), and petunidin-3-O-glucoside (0.84 mg L⁻¹); and delphinidin-3-O-glucoside (2.13 mg L⁻¹), while only peonidin-3-O-glucoside were higher to Syrah red wines (1.47 mg L⁻¹). The behavior of these results agrees with data reported to Uruguayan Tannat and Syrah wines (González-Neves et al. 2016), showing delphinidin-3-O-glucoside (11.8 and 3.3 mg L⁻¹), cyanidin-3-O-glucoside (0.9 and 0.8 mg L⁻¹), malvidin-3-O-glucoside (143.0 and 137.3 mg L⁻¹), petunidin-3-O-glucoside (23.4 and 8.2 mg L⁻¹), and peonidin-3-O-glucoside (6.7 and 8.5 mg L⁻¹). In both samples, only the peonidin-3-O-glucoside was higher in Syrah wines, and malvidin-3-O-glucoside was the most abundant anthocyanin.

Southern Brazilian Tannat wines (Campanha Gaúcha and Serra Gaúcha) presented higher concentrations than the Northeastern Tannat ones of delphinidin-3-O-glucoside (6.23–16.4 mg L⁻¹), malvidin-3-O-glucoside (8.34–86.5 mg L⁻¹), and petunidin-3-O-glucoside (14.8–18.2 mg L⁻¹) (De Andrade et al. 2013), as shown in Table 2. On the other hand, Tannat from the Northeast showed higher results to cyanidin-3-O-glucoside (4.69–11.5 mg L⁻¹) and peonidin-3-O-glucoside (5.68–19.1 mg L⁻¹) than the Southern ones. These authors suggest a different biosynthetic pathway of anthocyanins in wines from SSFV, explaining the most more representative proportion of cyanidin-3-O-glucoside (11%) and peonidin-3-O-glucoside (16%), decreasing the proportion of malvidin-3-O-glucoside (43%) in tropical red wines from this region. However, the anthocyanins in this present study did not present the same behavior, as malvidin-3-O-glucoside showed strongly greater representativity (86.22%), while cyanidin-3-O-glucoside (0.36%) and peonidin-3-O-glucoside (1.12%) presented the least percentages. In addition, complement, lower values of malvidin-3-O-glucoside (56.31 mg L⁻¹) have been reported to commercial Uruguayan Tannat wines (Valentin et al. 2020), in comparison to the wine Tannat herein presented.

Phenolic acids

Results obtained from phenolic acids are shown in Table 1. Total phenolic acids were the highest phenolic quantified in these wines, presenting 324.40 and 578.24 mg L⁻¹, to Tannat and Syrah wines, respectively. Syrah showed higher contents to ferulic acid (0.59 mg L⁻¹), ρ–coumaric acid (21.11 mg L⁻¹), caffeic acid (25.77 mg L⁻¹), trans-caftaric acid (523.69 mg L⁻¹), and chlorogenic (0.94 mg L⁻¹) acids whereas only gallic acid (11.77 mg L⁻¹) presented higher values to Tannat. Similar results were reported to gallic (15.2 mg L⁻¹) and caffeic (6.46 mg L⁻¹), concerning commercial Tannat wines (Valentin et al. 2020), as shown in Table 2, while previously chlorogenic acid values were not found to Tannat wines.

Isomers of caftaric acid were reported to Uruguayan Tannat wines (Table 2), cis-caftaric (48 mg L⁻¹), and trans-caftaric (41 mg L⁻¹), being strongly below in comparison with data herein presented (Boido et al. 2011). Also, even lower results of 10.85 mg L⁻¹ were presented to trans-caftaric in another approach (Favre et al. 2014). These data confirm the greater value of trans-caftaric (298.78 mg L⁻¹) to Tannat wine from SSFV. Likewise, trans-caftaric acid has been reported as the principal phenolic acid obtained in grapes and wines from the SSFV region (Padilha et al. 2019) and as the major non-flavonoid in grapes (Jackson 2014).

Flavonols and stilbenes

Quantifications of the classes of flavonols and stilbenes are also shown in Table 1. Tannat presented lower contents to flavonols: kaempferol-3-O-glucoside (0.97 mg L⁻¹), quercetin 3-β-D-glucoside (4.66 mg L⁻¹), and isorhamnetin-3-O-glucoside (2.44 mg L⁻¹), while myricetin and rutin did not present significant difference among the wines. Similar results of isorhamnetin-3-O-glucoside (2.7 mg L⁻¹) and higher values of myricetin (5.0 mg L⁻¹) were reported in Uruguayan Tannat wines (Vidal et al. 2018). Also, rutin (6.7 mg L⁻¹) and kaempferol-3-O-glucoside (3.86 mg L⁻¹) from commercial Tannat wines were quantified in higher amounts than this present study (Valentin et al. 2020).

Flavonols are presented in grape skins and their extraction in red wines depends on maceration. Besides, sunlight exposure may enhance this flavonols synthesis (Waterhouse et al. 2016), which can relate these compounds with great contents found in SSFV red wines. This can explain the great values obtained for quercetin 3-β-D-glucoside and isorhamnetin-3-O-glucoside from Syrah wines, due to cultivar good adaptation in this region.

According to Table 1, piceatannol presented higher contents to Tannat (0.34 mg L⁻¹), whereas the isomers trans-resveratrol and cis-resveratrol were more abundant in Syrah wines (0.29 and 0.63 mg L⁻¹, respectively). There is a scarce of studies with piceatannol quantification in Tannat and tropical red wines, which reinforces the importance of characterization of this compound.

The contents of resveratrol isomers are consistent with those found in Uruguayan Tannat wines, with 0.26 and 0.38 mg L⁻¹ for trans and cis forms, respectively (Favre et al. 2014). Generally, grapes produce the trans form, while the cis is obtained with light-inducing (Waterhouse et al. 2016). Also, some authors have suggested that regions with high temperature and luminosity presented major amounts to cis form, following that light-inducing isomerization (Padilha et al. 2017), which may confirm herein results to higher cis form to both studied varieties. Furthermore, resveratrol is the major stilbene present in wines and its synthesis is related to a response against fungal attacks. This compound is related to heart diseases and cancer reduction, but the concentrations in red wines would require more than 10 times the doses of a glass of wine (Waterhouse et al. 2016).

Total bioactive compounds and antioxidant activity

Total phenolic compounds (TPC) presented significant differences between the varieties studied (Table 1), being Tannat (1212.38 mg GAE L⁻¹) with higher results than Syrah ones (596.85 mg GAE L⁻¹), as expected. According to Waterhouse et al. (2016), TPC in red wines varies around 2000 mg GAE L⁻¹, and a value of 4410 mg GAE L⁻¹ has been reported for a commercial Tannat wine from the Rio Grande do Sul, Brazil (Pazzini et al. 2015). Therefore, as already described, this low concentration presented is due to the short maceration applied, only 96 h. Nevertheless, Tannat is a grape with high phenolic potential, which explains the quantification of total phenolic compounds to Tannat wine be twice over to Syrah wine. Similar data to this research were reported by Favre et al. (2014) to Uruguayan Tannat wine vinified with eight days (192 h) of maceration. This comparison may indicate that the cultivar Tannat from the SSFV stood out in the potential to synthesize bioactive compounds, favored by the geographic conditions of this region.

The in vitro Antioxidant Activity (AOX), obtained using FRAP and ABTS assays, is shown in Fig. 3. Tannat and Syrah wines presented 11.55 and 5.46 mmol TEAC L⁻¹ to ABTS, and 34.14 and 21.34 mmol FeSO₄ L⁻¹ to FRAP, respectively. The AOX presented the same behavior as TPC and TPI, exposing quite higher results to Tannat than Syrah wine, relating both methods. AOX using ABTS scavenging method ranging from 11.2 to 23.17 mmol TEAC L⁻¹ has been reported for various Southern Brazilian red wines (Gris et al. 2011). Similar results from these red wines and the Tannat wine from SSFV may confirm its greatly phenolic and antioxidant potential. Also, an approach with Merlot wines from Serbia, France, Italy, Macedonia, Slovenia, and Spain (Majkić et al. 2019) has reported to ABTS results with great variability (5.22–17.9 mmol TEAC L⁻¹) and lower AOX results to FRAP (8.08–19.2 FeSO₄ mmol L⁻¹), in comparison with Tannat wines from SSFV. Furthermore, SSFV environmental conditions may influence the synthesis of phenolic compounds with great AOX, highlighting the potential of these compounds (Padilha et al. 2017).

Fig. 3.

In vitro antioxidant activity (ABTS and FRAP assays) of Tannat and Syrah tropical red wines from São Sub-middle Francisco Valley. Means with asterisks differ by Student’s t-Test ‘*’(p ≤ 0.05) ‘**’(p ≤ 0.01). FeSO₄ = Ferrous sulfate; TEAC = Trolox equivalent antioxidant capacity

Some individual phenolic compounds may be important in increasing AOX. The flavonoid AOX approach has been reported, showing (−)-epicatechin gallate, (−)-epigallocatechin gallate, (+)-catechin, and (−)-epicatechin as having high ABTS scavenging capacity and ferric reducing power in FRAP. Furthermore, the authors presented caffeic and chlorogenic acids showing higher FRAP reactivity, while ρ-coumaric acid had high ABTS scavenging capacity (Grzesik et al. 2018). Moreover, peonidin-3-O-glucoside, ρ-coumaric acid, (+)-catechin, cyanidin-3-O-glucoside, procyanidin A2, and (−)-epicatechin have been reported to be highly correlated with the ABTS scavenging method (Padilha et al. 2017). Thus, among these compounds, (+)-catechin, gallic acid, delphinidin-3-O-glucoside, and procyanidin A2 may have positively influenced the great AOX of Tannat wines.

Conclusion

This was the first research featuring phenolic compounds and antioxidant activity of tropical red wine Tannat from the SSFV region, Brazil. These wines showed interesting values of bioactive compound contents, even with the short maceration time applied in the winemaking. Additionally, as expected, Tannat wine had higher total phenolic compounds and antioxidant activity (by ABTS and FRAP assays) than Syrah wine, as well as, had higher total phenolic index (TPI), color intensity (CI), total monomeric anthocyanins, and flavanols, including monomeric flavanols and proanthocyanidins. Regarding individual phenolic compounds quantified by HPLC–DAD-FD, Tannat wine had important contents of procyanidin B1, (+)-catechin, procyanidin B2, gallic acid, malvidin-3-O-glucoside, cyanidin-3-O-glucoside, delphinidin-3-O-glucoside, and pelargonidin-3-O-glucoside. Previously results to compounds (−)-epigallocatechin gallate, procyanidin B2, quercetin-3-β-D-glucoside, pelargonidin-3-O-glucoside, chlorogenic acid, and piceatannol were not found in Tannat wines. Therefore, the excellent results of trans-caftaric acid and procyanidin B1 in tropical Tannat wines compared to Tannat from temperate climate wine-producing regions may suggest the influence of the distinct environmental conditions in the Brazilian semi-arid region of SSFV in increasing concentrations of these compounds in the grapevines. The Tannat cultivar has a great phenolic and antioxidant potential to be explored in wine-producing regions with tropical climate conditions. These geographical conditions may enhance nutraceutical the variety’s potential and use it for the production of blends and full-bodied wines. Therefore, future studies are necessary to expand the knowledge about the behavior of this variety in the SSFV region, mainly applying typical commercial maceration time during winemaking.

Authors’ contributions

Carlos Artur Nascimento Alves: Conceptualization, Formal analysis, Investigation, Methodology, Resources, Visualization, Writing-original draft, Writing-review & editing. Aline Camarão Telles Biasoto: Supervision, Conceptualization, Methodology, Resources, Visualization, Writing-review & editing. Luís Henrique P. S. Torres: Formal analysis, Investigation, Methodology, Visualization. Luiz C. Corrêa: Formal analysis, Investigation, Methodology, Resources, Visualization. Patrícia Coelho S. Leão: Methodology, Resources, Visualization, Writing-review & editing. Ana Paula A. Barros: Methodology, Visualization, Writing-review & editing. Lucicleia B. de Vasconcelos: Supervision, Conceptualization, Methodology, Resources, Visualization, Writing-review & editing.

Funding

Grapes, oenological inputs, and all support to physicochemical evaluations were provided by Embrapa Semiárido. Support to spectrophotometric analyses were provided by Fruit Laboratory from Food Engineering Department of the Federal University of Ceará. Scholarship was provided by CAPES from Brazilian Government.

Availability of data and material

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

Consent to participate

This work been submitted in Journal of Food Science and Technology is approved by all authors.

Consent for publication

All authors provide consent for publication in Journal of Food Science and Technology, if the work is approved.