Flavonoid Profiling of Aglianico and Cabernet Sauvignon Cultivars from Campania, Sicily, and Molise, Three Regions of Southern Italy

Abstract

In the 2020 and 2021 vintages, some chemical and phytochemical parameters of the Aglianico and Cabernet Sauvignon cultivars grown in three regions of Southern Italy (Campania, Molise, and Sicily) were determined. In particular, the aim of this study was the investigation of flavanol, monomeric anthocyanin, and pigment contents in grapes and wines. The data collected showed that the main chemical parameters and flavonoids analyzed in the grapes and wines were influenced by the vintage, grape variety, and geographical location. Specifically, in the Aglianico grapes, the latitude and vintage highly influenced the titratable acidity and flavonoids in terms of richness in flavanols, compared to Cabernet Sauvignon. On the other hand, the location of the vineyard influenced monomeric anthocyanins in both varieties, highlighting a relationship of these phytochemicals with soil fertility and availability of certain chemical elements such as nitrogen and iron. All results support the idea that the interaction between grape variety, soil type, and geographical origin plays a decisive role in shaping the characteristics of wine.

1. Introduction

The quality of a wine is the result of a complex interplay of factors, from the vineyard to the winery. These factors, including soil type, environmental conditions, grapevine microbiome, viticultural practices, climatic conditions, vine phenology, and winemaking processes all contribute to the “terroir” effect that can determine the chemical composition and quality of grapes and wines [1,2,3,4,5,6,7]. In this regard, resolution OIV/VITI 333/2010 of the International Organization of Vine and Wine (OIV) defines vitivinicultural terroir as a concept that refers to an area in which collective knowledge of the interactions between the identifiable physical and biological environment and applied vitivinicultural practices develops, providing distinctive characteristics for the products originating from this area [8]. The cultivated grapevine, Vitis vinifera subsp. vinifera, possesses a rich biodiversity with numerous varieties. Each variety adapts differently to different soil and climatic conditions, which greatly influence the expression of the terroir [9,10,11]. Thus, the same grape variety cultivated in different regions gives rise to wines with different features [3,12]. Moreover, the quality of wines is directly linked to the composition of the different tissues of the fruit (pulp, skin, and seeds) and indirectly to the winemaking process.

Over the years, phenolic compounds have received much attention because they are a key factor in the quality of wines, particularly red wines [13]. They are secondary metabolites found in grapes and wines that can be formed and transformed during the winemaking process and aging [14,15]. Specifically, anthocyanins, flavanols, catechin, and other flavonoids are responsible for the sensory characteristics of wine, particularly color, astringency, bitterness, and flavor [16]. In addition, phenolic compounds have various positive effects on human health, especially due to their antioxidant properties [17,18,19].

During berry maturation, the biosynthesis and accumulation of phenolic compounds through the general phenylpropanoid pathway and its downstream reactions are influenced by several factors, including cultivar varieties, environmental factors (agro-pedological, topographical, and climatic), and cultural practices [15,20,21]. For these reasons, the same grape variety growing in different viticultural regions with diverse climatic conditions can give rise to wines with different contents of phenolic compounds in different vintages or in the same vintage [22,23,24,25,26]. Several studies have emphasized the role of phenolic compounds as markers of different aspects of wine quality, from grape varieties to geographical origin, to the year of harvest, to the winemaking process, and to the aging of the wine [27,28,29].

The influence of pedoclimatic conditions has been extensively investigated in major grapevine cultivars, particularly Cabernet Sauvignon, which is widely recognized for producing high-quality, long-aging red wines. Due to their greater phenotypic uniformity, international cultivars often displace indigenous varieties on a global scale [30]. In the context of climate change, increased attention should be directed toward indigenous cultivars, as they may offer viable alternatives to widely cultivated international types and contribute to enhancing the resilience of viticultural systems. Within the category of full-bodied, long-aged red wines, Aglianico represents a promising alternative to the widely cultivated Cabernet Sauvignon due to its high phenolic content and remarkable aging potential, despite its elevated tannin content. Both cultivars are late-ripening [31,32], and several studies have investigated the influence of pedoclimatic conditions on vine performance and the key technological parameters for both cultivars [33,34]. Recently, it has been shown that the phenotypic response of Aglianico and Cabernet Sauvignon grape varieties in terms of vigor, production, and fruit quality is strongly influenced by soil and climatic conditions and, in particular, by the physical properties of the soil [1,33,35].

However, while anthocyanins, polymeric pigments, and flavanols are recognized as major contributors to red wine quality and longevity, and it is clear that vintage can affect their concentrations for both cultivars [36,37], no study to date has directly compared the two cultivars in terms of these important flavonoid compounds across multiple pedoclimatic conditions and vintages in grapes and wines.

A direct assessment of the influence of pedoclimatic conditions on the pigment and flavanol composition of wines produced from both an international and an indigenous grape cultivar, each characterized by their suitability for long-term aging, can provide valuable insights into variety-specific metabolic responses to environmental factors. Such comparative analyses could be crucial for informing strategic decisions regarding varietal selection and adaptation in the context of climate change. In particular, identifying cultivars that maintain desirable phenolic profiles under warmer conditions could support the development of more resilient viticultural systems and help safeguard wine quality and typicity in future climatic scenarios.

In this study, we investigated the influence of vineyard location and vintage on the base chemical parameters and flavonoids of the Aglianico and Cabernet Sauvignon grapes grown in three different regions of Southern Italy (Campania, Molise, and Sicily) and on wines made from the different grapes.

2. Materials and Methods

2.1. Vineyard Characteristics

The studied grapevines were Aglianico and Cabernet Sauvignon cultivars planted between 2008 and 2010 on 140 Ruggieri rootstocks. The study areas were located in three Italian regions: Molise (San Biase, Campobasso district; Aglianico: 41°72′49.57″ N, 14°57′28.16″ E; Cabernet Sauvignon: 41°71′49.35″ N, 14°57′22.93″ E; 600 m a.s.l.), Campania (Galluccio, Caserta district; Aglianico: 41°33′38.27″ N, 13°89′31.16″ E; Cabernet Sauvignon: 41°33′32.79″ N, 13°90′39.65″ E; 125 m a.s.l.), and Sicily (Zafferana Etnea, Catania; Aglianico: 37°39′35.61″ N, 15°05′08.59″ E; Cabernet Sauvignon: 37°41′18.66″ N, 15°07′28.42″ E; 720 m a.s.l.). All vines were planted in north–south rows and trained according to the espalier Guyot, placed in a flat area. In previous studies, the soils of these experimental sites were classified as follows: a deep clay soil in Molise (vertisol), a deep clay loam volcanic soil in the Campania site (andosol), and a shallow volcanic sandy soil in the Sicily site (andosol). The main physical and chemical parameters of the soil for each study area were reported by Nicolosi et al. [38]. As far as fertility is concerned, the soil of the Sicily site had the highest organic matter (43.2 g/kg), with a C/N ratio of 10.7, compared to the Campania site (6.4 g/kg of organic matter; C/N ratio of 7) and the Molise site (18.6 g/kg of organic matter; C/N ratio of 7.6).

In the 2020 season (April–October), the soil moisture and temperature (averaged along soil profiles) were 50% and 17.2 °C for the Molise site, 38% and 20.2 °C for the Campania site, and 12% and 19.6 °C for the Sicily site, while from 1 April to 31 October 2021, the average recorded values of soil moisture and temperature were 55% and 12.8 °C, 41% and 17.8 °C, and 15% and 16.5 °C in Molise, Campania, and Sicily, respectively [33,35].

2.2. Winemaking Trials

Six experimental samples were considered: Aglianico Molise (AM), Aglianico Campania (AC), Aglianico Sicilia (AS), Cabernet Sauvignon Molise (CM), Cabernet Sauvignon Campania (CC), and Cabernet Sauvignon Sicilia (CS). Grapes were harvested during the 2020 and 2021 vintages at the full ripening stage [39,40]. In each vintage, the grapes were transported to the laboratory of the Department of Agricultural, Environmental, and Food Sciences of the University of Molise where they were destemmed and crushed without the addition of adjuvants. The chemical parameters of the must samples are reported in Table S1 (Supplementary Materials). Before the vinification process started, 80 mg/L of potassium metabisulfite (Essedielle srl, Ortona, Italy) was added to the grape musts. All samples were inoculated with 20 g/hL of Saccharomyces cerevisiae Lalvin ICV D254 (Lallemand Inc., Montreal, QC, Canada). The fermentation took place at 26 °C in stainless steel tanks, and the caps were immersed twice a day. After 8 days of maceration, the musts were pressed, and free-run and press-run fractions were assembled in stainless steel tanks (working volume, 1 hL). At the end of alcoholic fermentation, the wines obtained were subjected to chemical analysis.

2.3. Grapes and Wines Analysis

2.3.1. Grape Extraction

For grape analysis, two independent pools of 100 whole berries for each experimental sample were selected prior to the winemaking process. In the juice extracted from pulp pH, soluble solids (°Brix), and titratable acidity (g/L of tartaric acid) were measured as successively described (par. 2.2.4). For the analysis of polyphenols, separate extractions from skin and seeds, simulating the maceration process necessary for red wine production, were performed [37]. Briefly, a hydroalcoholic solution consisting of EtOH:H₂O (12:88 v/v), containing 5 g/L of tartaric acid and neutralized with NaOH up to pH = 3.2, was used for the extraction. After the manual separation of berries from stems, the berries were randomly selected, counted, and weighed. Skins and seeds were carefully separated, with pulp removed to preserve skin integrity. Individual skins were immediately immersed in the hydroalcoholic solution, weighed, deoxygenated with liquid nitrogen, sealed, and incubated at 30 °C for five days with daily manual agitation. The seeds were rinsed, dried, weighed, and extracted similarly. Following incubation, the flasks were cooled, and the solid residues were separated and gently pressed. The resulting liquid was combined and centrifuged at 4900 rpm for 9 min, and the clarified extract was transferred into dark glass bottles, sealed, and stored at 4 °C in the dark until analysis.

2.3.2. Base Parameters of Grapes and Wines

Standard chemical analyses of wines included pH, soluble solids (°Brix), titratable acidity (g/L of tartaric acid), volatile acidity (g/L of acetic acid), alcohol content (% v/v), and acetaldehyde content (mg/L) and were carried out according to the OIV methods [41]. In particular, pH was determined using a Fisherbrand accumet Basic AB315 Benchtop Laboratory pH-meter (Segrate, Milan, Italy). The titratable acidity was considered as the sum of titratable acidities when wine is titrated to pH 7 against a standard alkaline solution (NaOH 0.1 N). Carbon dioxide was not included in the titratable acidity. Alcohol content (% v/v) was analyzed by obtaining the distillate using a DE distillation unit (Gibertini, Milan, Italy). Measurements of the alcoholic strength were performed by means of densimetry using an ALCOMAT hydrostatic balance (Gibertini, Milan, Italy). Volatile acidity was determined as the sum of volatile acids and expressed as g/L of acetic acid. Carbon dioxide was first removed from the wine. Volatile acids were separated from the wine by steam distillation (using the DE distillation unit) and titrated using standard sodium hydroxide (0.1 N), using two drops of phenolphthalein as an indicator. L-malic acid (g/L), L-lactic acid (g/L), and citric acid (mg/L) were determined using enzymatic kits (Steroglass, Perugia, Italy) according to the manufacturer’s instructions.

2.3.3. Spectrophotometric Analysis

Flavanols were determined as vanillin reactive flavans according to Gambuti et al. [42]. One hundred microliters of wine were diluted 1:10 with methanol. For the assay, 125 μL of the diluted sample was transferred into a 1.5 mL microcentrifuge tube and mixed with 750 μL of a 4% vanillin solution in methanol. After 5 min, the tube was placed in an ice bath (4 °C), and 375 μL of concentrated hydrochloric acid was added. The mixture was incubated at room temperature (20 °C) for 15 min, after which absorbance was measured at 500 nm. A blank was prepared by substituting the vanillin solution with 750 μL of pure methanol. The total flavanol concentrations were calculated as (+)-catechin equivalents (mg/L) using a calibration curve.

The total polymeric pigments were determined according to Harberston et al. [43] and were expressed as the sum of short polymeric pigments (SPPs) and large polymeric pigments (LPPs). Briefly, SPPs and LPPs were distinguished on the basis of their different stability and reactivity: both types of pigments are resistant to sulfur dioxide bleaching, but only LPPs precipitate in the presence of proteins. Accordingly, SPPs were measured in bisulfite-treated samples, and LPPs were quantified by combining the first result obtained after the addition of SO₂ with those of the supernatant obtained after protein precipitation with bovine serum albumin (BSA).

2.4. High-Performance Liquid Chromatography Analyses of Anthocyanins and Acetaldehyde

Analyses of monomeric anthocyanins for each experimental sample were performed using an HPLC Shimadzu LC10 ADVP apparatus (Shimadzu Italy, Milan, Italy) equipped with a SCL-10AVP system controller, two LC-10ADVP pumps to create the needed solvent gradient, an SPD-M 10 AVP detector, and a Rheodyne 7725 full injection system (Rheodyne, Cotati, CA, USA). The analyses were performed according to the OIV methods [41]. The HPLC solvents were as follows: solvent A: Milli-Q water (Sigma-Aldrich, Milan, Italy)/formic acid (Sigma-Aldrich, ≥95%)/acetonitrile (Sigma-Aldrich, ≥99.9%) (87:10:3 v/v); solvent B: water/formic acid/acetonitrile (40:10:50 v/v). The gradient was as follows: zero-time conditions, 94% A and 6% B; after 15 min, the pumps were adjusted to 70% A and 30% B, at 30 min—to 50% A and 50% B, at 35 min—to 40% A and 60% B, at 41 min (end of analysis)—to 94% A and 6% B. Five minutes of re-equilibration time were applied before the successive analysis. The column used for the analyses was a Waters Spherisorb column (C 18, silica particle substrate, ODS2, with 4.6 mm inner diameter, 250 mm length and 5 μm particle diameter, 80 Å pore size; Waters S.p.a., Sesto San Giovanni, Italy) with a precolumn. Fifty microliters of calibration standards or wine were injected into the column. The absorbance signals at 520 nm were detected. Detector sensitivity was 0.01 Absorbance Units Full Scale (AUFS). All the samples were filtered through 0.45 µm Durapore membrane filters (Millipore, Carrigtwohill, Ireland) into glass vials and immediately injected into the HPLC system. The calibration curve was obtained by injecting 5 solutions (in triplicate) containing increasing concentrations of malvidin-3-monoglucoside (Extrasynthese, Lyon, France).

Total acetaldehyde was quantified according to the OIV methods [41]. Briefly, 100 μL of wine was transferred into a vial and mixed with 20 μL of a 1.120 mg/L SO₂ solution prepared from a 2 g/L K₂S₂O₅ stock. Subsequently, 2 μL of 25% sulfuric acid (96%, Carlo Erba, Milan, Italy) and 140 μL of 2 g/L dinitrophenylhydrazine (DNPH) reagent (Merck KGaA, Darmstadt, Germany) were added. After mixing, samples were incubated at 65 °C for 15 min, then cooled to room temperature. Analysis was performed by means of HPLC using the same system employed for anthocyanin quantification, equipped with a Waters Spherisorb column (4.6 mm inner diameter, 250 mm length, 4 μm particle size; Waters S.p.a., Sesto San Giovanni, Italy). Chromatographic conditions included a 50 μL injection volume, a flow rate of 0.75 mL/min, and a column temperature of 35 °C. The mobile phases were (A) 0.5% formic acid in Milli-Q water and (B) acetonitrile. Gradient elution started at 35% B, increased to 60% B at 8 min, 90% B at 13 min, and 95% B at 15 min (held for 2 min), then returned to 35% B over 4 min, for a total run time of 21 min. Identification and quantification were based on comparison with a calibration curve built with derivatized acetaldehyde standards (≥99.5%, Sigma Chemistry, St. Louis, MO, USA).

2.5. Statistical Analysis

Quantitative data were compared using Tukey’s least significant differences procedure. All the variances were homogeneous. When the variances were not homogeneous, data were analyzed using the Kruskal–Wallis test. When results of the Kruskal–Wallis test were significant (p < 0.05), the significance of between-group differences was determined by means of the Bonferroni–Dunn test (5% significance level). These analyses were performed using XLSTAT (version 2013.6.04; Addinsoft, Paris, France). All the data were expressed as the means ± standard deviations of four replicates (two experimental replicates × two analytical replicates).

3. Results and Discussion

3.1. Chemical Parameters in Grapes and Wines

Grape technological ripening was evaluated by determining the soluble solids content (Figure 1), titratable acidity (Figure 2), technological maturity index, and pH (Figure 3 and Figure 4, respectively) in the 2020 and 2021 vintages. As shown in Figure 1, no clear trend in sugar content was observed across the two experimental vintages.

Notably, when vintage and location were considered, significant differences in the soluble solids levels were registered in all the samples. Although the soluble solids content of a grape sample is expressed as a percentage by mass of sucrose (degrees Brix), as juice density during grape ripening is primarily influenced by glucose and fructose concentrations, its increase can be considered an indirect indicator of the enhanced synthesis of these fermentable monosaccharides. Commonly, the kinetics of sugar accumulation is affected by the cultivar, temperature, and their interaction [44,45,46]. In terms of climate factors, the vapor pressure deficit affects sugar accumulation, as lower evaporative demand leads to a lower transpiration rate, resulting in less sugar accumulation [47]. In addition, higher levels of photosynthetically active radiation have been shown to significantly influence the rate and total amount of sugar accumulation [48]. In our study, the biosynthesis of sugars in the 2020 and 2021 vintages may have been influenced by climatic fluctuations recorded in these years [49].

The effect of vintage and vineyard location was also observed for titratable acidity (Figure 2), regardless of the different climatic conditions [49]. In particular, in the 2020 vintage, titratable acidity in the Aglianico grapes ranged from 6.16 g/L to 10.30 g/L, while in Cabernet Sauvignon, it ranged from 5.23 g/L to 8.57 g/L. In the 2021 vintage, the values ranged from 4.26 g/L to 11.89 g/L for Aglianico and from 4.85 g/L to 8.39 g/L for Cabernet Sauvignon. Titratable acidity is significantly influenced by temperature, whereas tartaric acid, the primary organic acid in grapes, remains relatively stable under temperature variations. In contrast, malic acid levels are highly dependent on both ripeness and temperature, decreasing as temperature increases [50,51].

The trend of the technological maturity index, given by the soluble solids/titratable acidity ratio, was strongly influenced by vintage and vineyard location (Figure 3), as already reported for soluble solids and titratable acidity.

The maturity index is a useful indicator to understand if the raw material is suitable for winemaking and if the resulting wine is balanced from a compositional point of view. Values higher than 4 were detected for grape samples AS 2021, CS 2021, and CC 2020. In general, high values of the maturity index may indicate an impairment of the smooth progress of wine fermentation and possible microbial contamination that could cause an imbalance in the composition of the wine, with the production of unpleasant flavors by contamination and undesirable microorganisms [52].

As for pH, a significant increase in this parameter is generally due to high temperatures, as has already been reported in many wine-growing regions worldwide [53,54]. Grape berry pH and the balance of organic acids are strongly influenced by temperature [55]. Among the primary acids (tartaric, malic, and citric acids), malic acid is the most temperature-sensitive, with its concentration declining markedly during ripening, particularly under elevated temperatures. This reduction results from its utilization as a respiratory substrate in the later stages of ripening, a process accelerated by temperature-induced increases in enzymatic activity. Simultaneously, berry pH increases, driven in part by the accumulation of potassium (K⁺), a temperature-dependent process involving redistribution from vegetative tissues. As the major cation at maturity, potassium plays essential roles in enzyme activation, membrane transport, and osmotic regulation and contributes to pH modulation by partially neutralizing tartaric acid. For these reasons, the pH is also influenced by vineyard location and, in general, by pedoclimatic conditions [1]. In our case (Figure 4), the pH of both the Cabernet Sauvignon and Aglianico grapes was influenced by these factors.

The results of the chemical analysis of the wines are shown in

Table 1. Chemical parameters of the Aglianico and Cabernet Sauvignon wines produced from the grapes harvested in the 2020 and 2021 vintages. For each year, different lowercase letters in each column indicate significant differences (p < 0.05).

Years	Samples	pH	Titratable Acidity (g/L)	Volatile Acidity (g/L)	Alcohol (% v/v)	L-Malic Acid (g/L)	L-Lactic Acid (g/L)	Citric Acid (mg/L)
2020	AM	3.30 ± 0.01 d	7.28 ± 0.14 a	0.34 ± 0.04 bc	13.8 ± 0.1 a	0.21 ± 0.06 c	1.05 ± 0.05 a	0.25 ± 0.03 c
	AC	3.63 ± 0.02 c	5.55 ± 0.16 b	0.27 ± 0.02 c	13.2 ± 0.1 b	0.24 ± 0.06 bc	0.54 ± 0.03 d	0.37 ± 0.06 a
	AS	3.80 ± 0.01 a	5.23 ± 0.13 bc	0.53 ± 0.05 a	12.4 ± 0.2 c	0.51 ± 0.07 a	1.05 ± 0.03 a	0.33 ± 0.01 abc
	CM	3.70 ± 0.05 bc	4.85 ± 0.17 c	0.35 ± 0.05 bc	13.5 ± 0.2 ab	0.24 ± 0.06 bc	0.94 ± 0.04 ab	0.35 ± 0.01 ab
	CC	3.80 ± 0.05 ab	5.00 ± 0.20 c	0.40 ± 0.05 abc	14.0 ± 0.2 a	0.33 ± 0.05 bc	0.83 ± 0.05 bc	0.26 ± 0.01 c
	CS	3.70 ± 0.03 bc	5.15 ± 0.13 bc	0.41 ± 0.06 ab	11.5 ± 0.2 d	0.39 ± 0.01 ab	0.74 ± 0.03 c	0.27 ± 0.04 bc
2021	AM	3.28 ± 0.02 c	9.30 ± 0.20 a	0.24 ± 0.04 d	12.7 ± 0.1 de	2.46 ± 0.06 a	0.43 ± 0.07 bc	0.44 ± 0.01 c
	AC	3.32 ± 0.02 c	6.38 ± 0.12 b	0.39 ± 0.04 c	13.5 ± 0.3 b	1.32 ± 0.06 c	0.29 ± 0.08 c	0.53 ± 0.02 b
	AS	3.78 ± 0.02 a	4.42 ± 0.17 d	0.49 ± 0.03 b	13.4 ± 0.1 bc	1.06 ± 0.04 d	0.63 ± 0.09 ab	0.37 ± 0.01 cd
	CM	3.45 ± 0.05 b	5.40 ± 0.10 c	0.34 ± 0.04 c	14.5 ± 0.1 a	1.95 ± 0.05 b	0.29 ± 0.09 c	0.32 ± 0.02 d
	CC	3.54 ± 0.04 b	5.10 ± 0.10 c	0.59 ± 0.01 a	12.2 ± 0.2 e	0.84 ± 0.04 e	0.67 ± 0.03 a	0.61 ± 0.03 a
	CS	3.53 ± 0.05 b	4.54 ± 0.24 d	0.51 ± 0.02 ab	12.9 ± 0.1 cd	0.65 ± 0.02 f	0.46 ± 0.06 abc	0.41 ± 0.03 c

. Alcoholic fermentation was completed in all wine samples from both the 2020 and 2021 vintages. Considering the Cabernet Sauvignon wines, the highest alcohol contents were observed in the CC 2020 and CM 2021 wines (14.0% and 14.5% v/v, respectively), while the lowest alcohol content was detected in CS 2020 (11.5% v/v), in accordance with the initial sugar concentration in the grapes (Figure 1). A similar observation can be made for the Aglianico wines, as the highest (13.8% v/v) and the lowest (12.4% v/v) alcohol contents were observed in the wines AM 2020 and AS 2020, respectively, in agreement with the initial sugar concentration. The sugar content of grape berries directly affected the final alcohol concentration of the wines. In turn, sugar composition and accumulation undergo dynamic changes during berry ripening and are influenced by multiple factors, including environmental conditions and viticultural practices [56].

As expected after fermentation, lower values of titratable acidity and higher levels of pH were detected, attributable to the formation and precipitation of potassium bitartrate crystals. This process is driven by the release of potassium from the pulp and skins, as well as by the rising ethanol concentration during fermentation. The highest titratable acidity values were recorded in the AM wines, with 7.28 g/L and 9.30 g/L in the 2020 and 2021 vintages, respectively, while the values of pH were equal. Because the acidity is expressed as g/L of tartaric acid, this difference could be attributed to the occurrence of malolactic fermentation in the sample AM 2020, but not in the AM 2021, as evidenced by the respective malic and lactic acid concentrations (Table 1). Malolactic fermentation is known to reduce titratable acidity by converting malic acid to lactic acid and carbon dioxide. Because of the higher pKa of lactic acid (3.86) compared to the first pKa of malic acid (pKa1 = 3.40), the titratable acidity of wine containing more of the weaker acid is lower. In addition, in a pioneering study [57] where the two acids were compared at the same pH, malic acid appeared to be the most “sour” of the acids tasted, and therefore, more roundness would be expected in this wine, even for the sensory characteristics of different grape acids [46].

The pH values of the wine samples ranged between 3.28 and 3.80, considering both different experimental years (2020 and 2021) and vineyard locations. In a sensory study conducted on Cabernet Sauvignon, aimed at determining which sensory attributes most drive consumer and expert acceptance of Cabernet Sauvignon and Shiraz wines, pH values between 3.4 and 3.5 were those of Cabernet Sauvignon wines in the group of wines with the highest liking scores, also indicating that there was a significant positive linear correlation between the average “acidity” ratings and the titratable acidity and pH values [58]. Given the typically higher tannin content of Aglianico, maintaining similar or slightly higher pH values may be desirable to achieve high sensory quality in wines produced from this cultivar. Thus, with the exception of the AM wines in both vintages and the AC in 2021, all the samples showed values typical of highly regarded, full-bodied red wines.

The increase in pH is primarily attributed to the direct effect of temperature on the rate of malic acid degradation [59]. The lower titratable acidity, which is typically associated with higher pH values, is probably due to the interaction between potassium and tartaric acid, leading to its precipitation [51]. In addition, the degradation of malic acid, especially in the AM, CM, CC, and AS samples of the 2020 vintage, may have further contributed to the observed increase in pH, since an increase in lactic acid was also found in the same samples.

The highest citric acid values were found in the 2021 vintage, in particular, for the CC (0.53 g/L) and AC (0.61 g/L) wines, but in general, all the wines showed citric acid concentrations in normal ranges. Citric acid values are related to the cultivar and the pedoclimatic conditions. Moreover, the concentration of citric acid is strongly dependent on oxygen availability during the alcoholic fermentation [60]. Citric acid can be partially or fully metabolized by lactic acid bacteria, leading to the formation of acetic acid, diacetyl, acetoin, and 2,3-butanediol [61,62].

Finally, the volatile acidity values found in all the analyzed wines ranged between 0.24 and 0.59 g/L, that is, within the acceptable range established by current regulations, which set the maximum allowable limit for wines at 1.2 g/L [63].

3.2. Flavonoid Profile of Grapes and Wines

Total flavanols and anthocyanins were the main classes of phenolic compounds considered. Flavanols are compounds contained in wine and responsible for bitterness and astringency. The total flavanol content as extracted from the skin and seeds of the grapes is shown in Figure 5.

In the 2021 vintage, the accumulation of these compounds was higher for both cultivars in almost all the samples compared to the 2020 vintage, probably due to the effect of higher biosynthesis and lower water content in the berries [49]. The effect of the vintage was more pronounced in the case of Cabernet Sauvignon grapes than in Aglianico grapes, while vineyard location had a lower effect. In agreement with the literature [1,64], a higher concentration of flavanols was observed in Aglianico compared to Cabernet Sauvignon, especially in the 2020 vintage. Considering the wines (Figure 6), the lower values of total flavanols detected in wines in comparison to grapes are attributable to reactions of oxidation, polymerization, and precipitation that native phenolic compounds underwent, as already reported by Iorizzo et al. [1].

Specifically, the data analysis showed higher values of total flavanols in the 2021 vintage than in the 2020 vintage in all the samples, generally mirroring what had already been observed for grape berries. The location of the vineyard had a minor influence on the flavonoid content. It is necessary to underline that, in some cases, a higher flavonoid content can give an excessive astringency to wines and, therefore, it is important to define winemaking protocols useful to limit their extraction during the maceration and fermentation of grapes [65].

A significant effect of vineyard location was found for the monomeric anthocyanin content in grapes (Figure 7) and wines (Figure 8). In particular, for both cultivars, the content decreased from the highest latitude (Molise) to the lowest (Sicily) for grapes, with a few exceptions, such as the grape sample CS 2021 (Figure 7). The same trend was not observed in wines (Figure 8), probably due to the transformations of these compounds during vinification processes [14,15]. It is known that the biosynthesis of anthocyanins depends on UV radiation and thermal excursion. The higher the radiation and the thermal excursion, the higher the synthesis of anthocyanins. On the other hand, average night temperatures above 20 °C lead to less biosynthesis of anthocyanins during berry ripening [66,67]. Therefore, the higher night temperature and the lower thermal excursion of Sicily can easily explain the great difference between Molise and Sicily for both cultivars [1].

As previously reported, the soil of the Sicily site had the highest organic matter. The soil can affect vine’s vegetative development through the modulation of water and nutrient dynamics, indirectly influencing the accumulation of anthocyanins [68]. In this regard, Bambina et al. [69] found that the anthocyanin profile of Nero d’Avola red wines was influenced by the different soil types, and soils with low nutrient availability (low-fertile soils) appeared to favor anthocyanin synthesis.

Particularly high nitrogen and iron availability significantly impacts anthocyanin levels in grapes. Low nitrogen and iron levels can stimulate anthocyanin synthesis, while water stress can also lead to increased anthocyanin concentrations, especially in specific soil types such as clay loam [70,71,72,73].

This is in line with what was observed in the present study, namely that highly fertile soils (Sicily site) and soils richer in elements such as nitrogen and iron [38] produced grapes with a lower total anthocyanin content (Figure 7) than the Molise site containing less organic matter and iron.

Regarding soil types, Bambina et al. [68,69] highlighted that the clay and silt content in soils was negatively correlated with anthocyanins. On the other hand, our results show that for both grape varieties, there is almost always a positive correlation between the clay and silt content in the soils (Molise and Campania sites) and the total monomeric anthocyanins (Figure 7). This could be explained by the prevalence of other factors mentioned above, such as soil fertility, over the synthesis of these compounds.

The cultivar most sensitive to latitude was Aglianico, which showed approximately twofold higher values of total monomeric anthocyanins in grapes from the Molise region than in Sicily.

Concerning the monomeric anthocyanins (

Table 2. Monomeric anthocyanins (mg/L) of the Aglianico and Cabernet Sauvignon wines (2020 and 2021 vintages).

Years	Anthocyanins	AM	AC	AS	CM	CC	CS
2020	Delf-3mg	12.62 ± 4.37 Aa	3.30 ± 0.22 Bb	1.57 ± 0.42 Ba	8.87 ± 2.52 Ab	2.91 ± 0.40 Bb	4.50 ± 0.81 Ba
	Cyan-3mg	0.43 ± 0.09 ABb	0.21 ± 0.04 Cb	0.21 ± 0.17 Cb	0.55 ± 0.15 Aa	0.35 ± 0.03 ABCa	0.24 ± 0.06 BCb
	Pet-3mg	16.96 ± 4.59 Aa	5.51 ± 0.21 Cb	3.22 ± 0.45 Ca	11.54 ± 2.35 Bb	6.91 ± 0.87 Ca	6.24 ± 1.40 Ca
	Peon-3mg	3.82 ± 1.11 Bb	8.50 ± 0.88 Aa	2.54 ± 0.25 Ca	0.91 ± 0.28 Db	0.82 ± 0.09 Db	2.56 ± 0.32 Ca
	Malv-3mg	145.10 ± 26.50 Aa	89.27 ± 6.05 Bb	101.74 ± 9.34 Ba	101.65 ± 16.27 Ba	88.06 ± 9.26 Ba	86.41 ± 19.16 Ba
	Malv-Ac	14.18 ± 2.30 Ca	5.78 ± 0.32 Da	9.57 ± 1.18 CDa	35.31 ± 7.22 ABa	41.56 ± 4.27 Aa	28.02 ± 5.65 Ba
	Malv-Cum	15.28 ± 2.49 Aa	8.86 ± 0.77 BCDb	9.64 ± 1.25 BCa	7.92 ± 1.33 CDa	11.19 ± 1.40 Ba	6.56 ± 1.57 Da
2021	Delf-3mg	13.01 ± 4.09 Ba	4.647 ± 0.14 Ca	1.28 ± 0.33 Da	17.21 ± 1.41 Aa	4.93 ± 0.42 Ca	3.89 ± 0.09 CDa
	Cyan-3mg	0.86 ± 0.27 Aa	0.523 ± 0.09 BCa	0.46 ± 0.04 BCa	0.58 ± 0.07 Ba	0.38 ± 0.18 BCa	0.32 ± 0.04 Ca
	Pet-3mg	14.73 ± 1.08 Aa	8.538 ± 0.68 Ba	2.94 ± 0.12 Da	14.43 ± 1.19 Aa	5.74 ± 0.31 Cb	3.85 ± 0.11 Db
	Peon-3mg	5.97 ± 0.24 Aa	5.174 ± 0.17 Bb	2.20 ± 0.07 Cb	5.60 ± 0.51 ABa	2.35 ± 0.10 Ca	2.35 ± 0.07 Ca
	Malv-3mg	125.64 ± 8.13 Aa	104.879 ± 10.19 Ba	84.32 ± 3.06 Cb	104.94 ± 8.36 Ba	56.67 ± 3.05 Db	44.09 ± 1.13 Eb
	Malv-Ac	16.79 ± 17.96 BCa	4.485 ± 0.68 Cb	8.68 ± 0.49 Ca	35.99 ± 2.64 Aa	22.93 ± 0.93 Bb	15.01 ± 0.37 BCb
	Malv-Cum	11.36 ± 2.59 Ab	12.080 ± 1.98 Aa	4.21 ± 0.34 Cb	7.29 ± 0.51 Ba	3.40 ± 0.28 Cb	2.03 ± 0.12 Cb

Delf-3mg = delphinidin monoglucoside. Cyan-3mg = cyanidin 3-monoglucoside. Pet-3mg = petunidin 3-monoglucoside. Peon-3mg = peonidin 3-monoglucoside. Malv-3mg = malvidin 3-glucoside. Malv-Ac = malvidin 3-(6^II-acetyl)-glucoside. Malv-Cum = malvidin 3-(6^II-coumaroyl)-glucoside. All the data are expressed as the means ± standard deviations of four replicates (two experimental replicates × two analytical replicates). Uppercase letters (A, B, C, D, E) indicate significant differences (p < 0.05) between the same molecules among the wines produced in the same year. Lowercase letters (a, b) indicate significant differences (p < 0.05) in the same wine in different year.

), in agreement with the previous literature, the Cabernet Sauvignon wines differed from the Aglianico wines in the higher ratio of acetyl to coumaroyl anthocyanins [26]. These data confirm that, regardless of environmental conditions, this ratio is genetically driven and is a good marker of the authenticity of grapes and wines when young, before native anthocyanins are consumed in reactions, giving new pigments [74]. The content of malvidin-3-monoglucoside was significantly influenced by the years, especially in the Molise area and for the Aglianico grape variety. On the other hand, a strong effect of the year was observed only for the Cabernet Sauvignon wines produced in Campania and Sicily. Since the effect was observed for all anthocyanin derivatives, it is clear that it depends more on the synthesis of anthocyanidin aglycones than on the acylation and possible degradation of monomeric anthocyanins during winemaking [75].

Data on polymeric pigments can help to understand the overall effect of environmental conditions on red wine pigments and provide more complete information (Figure 9). Native anthocyanins started to react with other grape phenolics from maceration–fermentation, due to the fact that they have both electrophilic and nucleophilic carbons, so that flavanols can react with them to give condensation products [76]. These reactions produce new pigments that are more stable, can have a different molecular weight, and can be divided into short and large polymeric pigments on the basis of their reactivity towards BSA and SO₂ [43]. Our data clearly show that these compounds were higher in the wines obtained from grapes with a higher flavanol/anthocyanin ratio. Similar results were also obtained in Aglianico, Barbera, and Sangiovese wines when subjected to oxidative stress such as that occurring during wine aging [77].

The large amount of polymeric pigments in the CS samples from Sicily in 2021 compared to 2020 could also be attributed to a greater formation of structures containing ethanal bridges due to the higher amount of acetaldehyde in the wines produced in 2021 (Figure 10).

Acetaldehyde is a strong electrophile at wine pH and reacts with many other compounds in the medium [56,57]. On the other hand, it is also of great interest to understand why it is only in these specific wines that the concentration of acetaldehyde is more than twice as high as in other wines. It is known that acetaldehyde has multiple origins, microbial and chemical. The higher values of acetaldehyde found in the wines produced from grapes grown in Sicily could be related to the lower levels of titratable acidity of these grapes, determining a higher risk of oxidation [78]. Data on the acetaldehyde detected are well below the sensory threshold, and the higher the level of this electrophile, the higher the stability of color and polymeric pigments present in aged wines, confirming the positive role of moderate amounts of acetaldehyde for wine aging [79,80].

4. Conclusions

The parameters of the wines evaluated in this study were influenced by the grape variety, but also by other important factors such as the vintage and the location of the vineyard. In both cultivars, the monomeric anthocyanin content decreased as a function of latitude due to different environmental conditions. While, a different effect of latitude was observed for flavanols and monomeric anthocyanins in Cabernet Sauvignon and Aglianico wines. As for the varietal effect, acidity, and phenolic compounds, the grape variety with the highest sensitivity to latitude and vintage was Aglianico. In Molise, and to a lesser extent in Campania, the Aglianico wines were found to have higher concentrations of anthocyanins and lower levels of flavanols than the Cabernet Sauvignon wines produced under the same conditions. This phenolic profile suggests that the local pedoclimatic conditions are more favorable for the production of long-aged Aglianico wines, at least in terms of pigment and flavanol composition. This result, combined with the observation of lower pH values in the Aglianico wines and the expected trend of increasing pH under future climate scenarios, further supports the suitability of Aglianico as a varietal for maintaining wine quality and longevity in these regions. Thus, the ability of Aglianico to maintain favorable phenolic profiles and acidity under current conditions suggests a strong potential for adaptation to warmer climates in the south–central regions of Italy, reinforcing its value in climate-resilient viticultural strategies.

In light of our results, the technological maturity index, which is still determined by the sugar/acidity ratio of the grape pulp, should be combined with phenolic maturity indices, which should, however, be determined according to the cultivar and the different environmental conditions.