Effect of prolonged (150 days) post-fermentative maceration in steel tanks and oak barrels on Cabernet Sauvignon wine quality: mathematical modelization of the phenolic compounds behaviour

doi:10.21203/rs.3.rs-2243911/v1

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Effect of prolonged (150 days) post-fermentative maceration in steel tanks and oak barrels on Cabernet Sauvignon wine quality: mathematical modelization of the phenolic compounds behaviour

https://doi.org/10.21203/rs.3.rs-2243911/v1

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The aim of this study was to evaluate the effects of the prolonged post-fermentative maceration during the winemaking of Cabernet Sauvignon grapes in oak barrels and steel tanks and apply to this purpose a mathematical modelization to better and easily understand the dynamics and phenomena related to this process.

The study focused on the time series of phenolic and volatile compounds in wines during the maceration with solid parts and residual components of the alcoholic fermentation, only for anthocyanins and non-anthocyanic flavonoids two mathematical models were proposed.

The results showed that the presence of solid parts during the post-fermentative maceration phase provided a higher content of polyphenols and total flavonoids in both oak barrel and steel tanks. The largest contents of polyphenols and flavonoids were observed in oak barrels trials. Among the anthocyanins in both trials we have assisted to a decreasing trend in delphinidin-3 glucoside, cyanidin-3glucoside, petunidin-3-glucoside and peonidin-3-glucoside, with a more accentuated process for the first two molecules in barrique trial, also acetylated anthocyanins showed a decreasing trend more intense in barrique trial. Finally, the post fermentative maceration did not affect HCTA and flavonols concentrations in wines, but rather it affects their chemical stability through the time.

Post-fermentative maceration improved the sensory characteristics in terms of intensity, complexity, and persistence at both olfactory and gustatory level, especially in oak barrel vinification.

Cabernet Sauvignon

mathematical modelization

post-fermentative maceration

steel tanks and oak barrels

polyphenols

volatile compounds

sensory analysis

The concentration and composition of phenolic compounds play a pivotal role in red wines quality, since they affect sensory attributes such as colour, astringency, and bitterness (Bindon et al., 2014). Given that phenolic compounds are mainly found in skins and seeds of grape berries, the optimal extraction of these compounds through the contact with the pomace is a crucial factor in the red winemaking (Bindon et al., 2010). The duration and the methods of maceration influence the extraction of anthocyanins and other phenolic compounds, and the reactions in which they are involved (González-Neves et al., 2008; Soto Vàzquez et al., 2010).

In fact, different kinds of phenolic compounds are extracted from grapes to must/wine during the maceration process with different kinetics, depending on their chemical nature and extractability characteristics. The anthocyanins and low-molecular weight flavanols, that are confined to the first epidermal layers of the skins and to seeds, respectively (Ortega-Regules et al., 2007), are extracted in aqueous medium during the first step of maceration (pre-fermentative maceration) (Rivero et al., 2019).

High-molecular weight flavanols, flavonols and phenolic acids, that are located in both seeds and skins, are more soluble in alcoholic solution. Therefore, they are extracted when the alcoholic fermentation occurs (González-Neves et al., 2015). Post-fermentative maceration allows a further extraction of polyphenolic compounds, mainly proanthocyanidins and condensed tannins, providing mouthfeel modifications (Weber et al., 2012) and stability of coloured compounds (Bindon et al., 2014) through the formation of polymeric pigments. These chemical species are formed by covalent reactions between anthocyanins, tannins and other non-phenolic materials (Somers, 1971).

The maceration phase also influences the sensory profile of the resulting wines because other compounds, such as aromatic substances and precursors, are released during this time (de Beer et al., 2017).

Under standard conditions, in the red winemaking the contact of solid parts of grapes with the must is limited to the duration of the alcoholic fermentation, that is typically completed in 8–13 days after crushing.

During winemaking and ageing, phenolic compounds undergo several reactions that may lead to colour loss or its stabilization, and to astringency modifications. These reactions include polymerization of tannins and reactions between tannins and anthocyanins. The conversion of monomeric anthocyanins in new and more stable polymeric pigments is the reason for the change from the purple red of young wines to the tawny hue observed in older red wines (Gómez-Plaza et al., 2004). These reactions are more intense during oxidative ageing in wood. The barrel, in fact, acts as an active vessel, providing a mild oxygenation that improves the stabilization of the red wine colour and other chemical reactions between wine compounds and other chemical species released by the wood (Ribéreau-Gayon, 1933), improving its physical, chemical, and sensory properties. The oxygen transfer depends on different factors, such us intrinsic properties of the wood and, at barrel level, the internal volume of the vessel (Roussey et al., 2021). In fact, the maturation effects that are attributed to barrels (evaporation, extraction, oxidation) depend on the ratio between the wine surface area in contact with wood and the wine volume. The greater the ratio (the minor the volume of the barrel) the greater the reactions rate. Post-fermentative maceration (PFM) prolongs skin and seed contact after the must has fermented to dryness (Sacchi et al., 2005; Casassa et al., 2014). The duration of post-fermentative maceration could be extremely variable, ranging from 1 to few months. This practice has gathered attention because of its potential to enhance phenolic extraction (Auw et al. 1996; Canals et al. 2005), stabilise wine colour (Auw et al., 1996; Puertas et al., 2008) and modify mouthfeel properties (Schmidt and Noble, 1983; Joscelyne, 2009).

Therefore, the main objective of this work was to evaluate the influence of post-fermentative maceration of 150 days duration on the vinification Cabernet Sauvignon grapes, conducted in steel tanks and oak barrels, on the evolution of polyphenolic and volatile organic compounds (VOC) profiles.

2.1 Wine making

Cabernet Sauvignon grapes were grown in the "Cossentino" organic vineyard on Castellammare del Golfo hills (Trapani, Sicily, Italy). The vineyard is located at 350 meters above sea level, bred in spurred cordon with a planting density of 2.0 m x 1.0 m. Grapes were harvested at about 24.5–25.5 °Brix, were transported in boxes and, after sorting to eliminate unhealthy grapes, were destemmed, and softly crushed. 50 mg/kg of SO₂ equivalents were added to the crushed grapes. The vinification of the trials was carried out in duplicate and for this purpose the total bulk was separated into two stainless-steel tanks (5 hL,) and into two oak barrels (25 hL,), to obtain two different trials corresponding to: steel tank trial with post-fermentative maceration (PFMS) and oak barrel trial with post-fermentative maceration (PFMB). The barrels (three years) used for the experiments had the capacity of 25 hL and an oval shape to enhance the solid-liquid exchange of the marc cap.

The crushed grapes were fermented by the inoculation of a pied de cuvè prepared with 10 g/L of Saccharomyces cerevisiae yeasts (Lalvin EC 1118). Then, diammonium phosphate (DAP) containing thiamine (0.25%) (Hnutrix® Dhizote F, HTS enologia, Marsala, Italy) was added to each trial, until musts reached 200 mg/L of promptly assimilable nitrogen.

During the alcoholic fermentation, the temperature was kept at 26 ± 1°C and, to favour the extraction of phenolic compounds and homogenize the must, one pump-over per day was done until the end of alcoholic fermentation.

In both steel tank and oak barrel trials with post-fermentative maceration (PFMS and PFMB) the racking was carried out on 150th day after grapes crushing. After the end of the spontaneous malolactic fermentation, a second addition of SO₂ was performed to restore about 25–30 mg/L of free SO₂ equivalents. A further correction of free SO₂ about 25–30 mg/L of free SO₂ was carried out until 150th day from the crushing grapes. Then, the wines were filtered (5.0-µm pore size filter) and bottled. The wines were stored at 16°C and 80% of RH for 1 months.

The must/wine has been analysed several times during the whole vinification process. Fourteen samplings were carried out from must/wine at a 0, 3, 8, 13, 20, 30, 40, 50, 60, 70, 90, 110, 130 and 150 days from the crushing grapes.

2.2 Chemical and physical parameters

A replicate for each sample of must and wine (2) were used to determine the chemical-physical parameters. Ethanol content (% v/v), reducing sugars (g/L), glycerol (g/L), malic acid (g/L), lactic acid (g/L), total acidity (g/L), volatile acidity (g/L) and pH were determined by means of Winescan (FOSS, Hilleroed, Denmark) calibrated following EEC 2676 standard procedure (EEC, 1990).

2.3 Determination of Polyphenols Content

A replicate for each sample (2) of must and wine were used to determine polyphenols content.

Total polyphenols (mg/L), total flavonoids (mg/L as (+)-catechin), total anthocyanins (mg/L as malvin) and monomers anthocyanins (mg/L as malvin) contents were determined by UV–Vis spectrophotometry, as reported by Di Stefano et al. (1989), Di Stefano and Cravero (1991) and Corona et al. (2015). Monomer anthocyanins profiles, hydroxycinnamoyl tartaric acids (HCTA) and flavonols contents were determined through HPLC (Agilent series 1200 instrument, Milan, Italy), equipped with a DAD detector and with a C18 column (EconosphereTM C18, 5 µm, 250 × 4.6 mm i.d., Lokeren, Belgium, part n° 70,066), injected volume 20 µL, flow rate 0.48 mL/min. as reported by Squadrito et al. (2007 and 2010).

For HPLC analysis of anthocyanins, the mobile phase was a linear gradient of HCOOH:CH₃OH:H₂O (10:40:50 v:v:v; solvent B) in HCOOH:H₂O (10:90 v:v; solvent A), the flow rate was 0.48 mL/min, and the oven temperature was 45°C. The proportions of solvent B were as follows: isocratic for 15 min with 45%; 15–35 min, 45–70%; 35–45 min, 70–90%; 45–50 min, 90–99%; isocratic 50–54 min, 99%; 54–56 min, 99 − 45%. Detection was performed at 520 nm.

For HPLC analysis of HCTA and flavonoids the mobile phase was a linear gradient of H₃PO₄ 10^− 3 M (solvent B) in CH₃OH (solvent A), the flow rate was 0.48 mL/min, and the oven temperature was 40°C. The proportions of solvent B were as follows: 5 min with 5%; 5–10 min, 5–10%; 5–20 min, 10–30%; 20–30 min, 30–60%; 30–40 min, 60–100%; 40–48 min, 100-5%; 48–53 min, 5%. Detection was performed at 320 nm for HCTA and 360 nm flavonoids.

The different phenolic compounds determined by HPLC were identified and quantified by comparing the retention times of the standards when possible and by comparing the spectra of the unknown compound and the pure standard using a diode array detector (Hewlett-Packard 1100 DAD), maintaining all the same other chromatographic conditions. Caffeoyl tartaric acid (caftaric acid) and p-coumaroyl tartaric acid (coutaric acid) were isolated according to the method described by Singleton et al. (1978). The anthocyanins concentration was expressed as malvidin-3-glucoside and flavonoids concentration was expressed as (+)-catechin, which was isolated using the method described by Wulf and Nagel (1978). The anthocyanins profile is reported as percentage content of each anthocyanin.

2.4 Determination of Volatile Organic Compounds

A replicate for each sample (2) of must and wine were used to determine volatile organic compounds (VOC). VOCs were determined by Gas Chromatography (GC) and Gas Chromatography/Mass Spectrometry (GC-MS) as reported by Corona (2010) and Corona et al., 2019).

Briefly, 25 mL of wine, spiked with 1-heptanol as internal standard (0.25 mL of 40 mg/L hydroalcoholic solution), diluted to 75 mL with distilled H₂O, was passed through a 1 g C18 cartridge (Isolute, SPE Columns, Uppsala, Sweden, part n° 221-0100-C) previously activated with 3 mL of methanol followed by 4 mL of distilled H₂O. After washing with 30 mL of distilled H₂O, volatiles were recovered by elution with 12 mL of dichloromethane, dehydrated and evaporated to 0.5 mL prior to injection in splitless mode into the gas-chromatograph coupled with mass spectrometer (Agilent 6890 Series GC system, Agilent 5973 NetWork Mass Selective Detector, Milan, Italy), equipped with a DB-WAX column (Agilent Technologies, 30 m, 0.250 mm i.d., film thickness 0.25 µm, part n° 122–7032). Oven temperatures were: 40°C kept 2 min, from 40 to 60°C with a rate of 30°C/min, 60°C kept for 2 min, from 60 to 190°C with a rate of 2°C/min, 190°C kept for 0 min, from 190 to 230 with a rate of 5°C/min, 230°C kept for 15 min. Temperature of split/splitless injector 250°C, transfer line 230°C, carrier helium with a column flow of 1 mL/min.

Volatile organic compounds were identified by comparison of the mass spectra and GC retention times and by comparing their mass spectra with those within the NIST/EPA/NIH Mass Spectral Library database (Version 2.0d, build 2005). The concentration (mg/L) of volatile organic compounds was determined as 1-heptanol equivalents.

2.5 Sensory evaluation

The sensory profiles of the wines were evaluated by a descriptive method (UNI 10957, 2003). Nine judges were trained in preliminary sessions using different samples of Cabernet Sauvignon commercial wines to develop a common vocabulary for the description of the sensory attributes of the experimental wines, as well as to familiarise with scales and procedures. Each attribute was extensively described and explained to avoid any doubt about the relevant meaning. The standards used to define descriptors were chosen according to Noble et al. (1987). Based on frequency of citation (> 60%), 14 descriptors were included in the analysis: colour intensity and purple reflexes for visual evaluation; fruity, wild berries, dried fruits, floral, herbaceous, spicy and odour complexity for olfactory evaluation; acid, salty, bitter, astringent and taste complexity for gustatory evaluation. The wine samples were randomly evaluated by assigning a score between 1.00 (absence of sensation) and 9.00 (extremely intense).

2.6 Statistical analysis

The extraction kinetics of polyphenolic compounds and the concentrations of volatile organic compounds in relation to the maceration time were modelled by linear and non-linear regression techniques, using Minitab 21 Statistical Software for Windows (State College, PA).

A specific modelization approach for total anthocyanin, total flavonoids and non-anthocyanic flavonoids was performed with R statistics 4.0.3 (The R Foundation for Statistical Computing, R Core Team, 2020), using the package “drc” (Ritz et al., 2015).

To test the means differences along the time a linear mixed effect model considering the repeated measurement as random factor was fitted for every volatile compound, the marginal means extracted from the model were compared through LSD Bonferroni α value corrected post hoc with a complessive α value of 0.05 on the Student’s t distribution, the software used was R 4.0.3 (The R Foundation for Statistical Computing, R Core Team, 2020) using the packages “nmle” (Pinheiro et al., 2021), “emmeans” (Russel, 2021), “multcomp” and (Torsten et al., 2008).

To establish the mean differences among same times of different trials (PFMS compared to PFMB), a student’s t test was carried out for every volatile compound using an α value of 0.05 on the Student’s t distribution using R 4.0.3 (The R Foundation for Statistical Computing, R Core Team, 2020).

2.7 Proposed approach for the study of total flavonoids, non-anthocyanic flavonoids and anthocyanins

2.7.1 Anthocyanins

Our proposed approach is to divide the anthocyanin kinetic in two stages: the first one called stage I, from zero to the maximum concentration detected, the second one is called stage II and it start from the maximum concentration reached.

The first stage can be fitted by the following second-degree equation

Equation 1

$${A}_{I}=\alpha \bullet {t}^{2}+\beta \bullet t+\gamma$$

Where:

A _I is the concentration of anthocyanin in the stage I;

t = time

The second stage is modelized by fitting the following equation:

Equation 2

$${A}_{II}=a-(a-b){e}^{-ct}$$

Where:

A _II is the concentration of anthocyanin in stage II;

a = A_II horizontal asymptote concentration;

b = intercept of the equation;

c = factor proportional to the slopes of the equation;

t = time.

It is worth to mention that the parameter b in this application has not a real meaning of intercept because the domain of this function start from the first t decreasing point measured.

2.7.2 Speed of the anthocyanin extraction in stage I

The speed of extraction can be examined and compared through the first derivative of A_I respect to time

Equation 3

$$\frac{d{A}_{I}}{dt}=2\alpha \bullet t + \beta$$

In which β can represent the starting speed of extraction of anthocyanin and 2α is the factor of speed decreasing during the time (second derivative of A_I respect to time).

2.7.3 Stage II dynamics

The dynamics of anthocyanin concentration in stage II can be examined and compared through the value c and the difference between a and b. Values that for a specific time are proportional with the derivative of the function respect to time (proportional to the decreasing in concentration over the time).

2.7.4 Non-anthocyanic flavonoids

Non-anthocyanic flavonoids (NAF) are a group of compounds comprehending flavan-3-ols and flavonols, technically speaking, can be considered a good estimation of the flavan-3-ols contained in grapes and wine.

The method to calculate this index was furnished by Di Stefano et al., 1989, as follow

Equation 4

$$NAF = [{ABS{\prime }}_{280}-{(ABS}_{max vis}\bullet {3.5}^{-1})]\bullet 82.4\bullet d$$

In which:

NAF = non-anthocyanic flavonoids concentration expressed as mg equivalent of (+)-catechin ∙ L^− 1;

ABS’₂₈₀ = 280 nm absorbance corrected as described by Di Stefano et al. in 1989;

ABS_{max vis} = maximum absorbance detected in visible range, this approach contains a simplification, or rather we use the same coefficient of molar absorbance for slightly different wavelength;

d = number of dilutions made.

2.7.5 Modelization of NAF

NAF fitting was made with the same asymptotical equation described for anthocyanin stage II:

Equation 5

$$NAF=a-(a-b){e}^{-ct}$$

Where:

NAF = concentration of non anthocyanic flavonoids;

a = horizontal asymptote concentration;

b = intercept;

c = factor proportional to the slopes of the equation;

t = time.

3.1 Chemical-physical analyses

On 13th day after crushing the alcoholic fermentation ended in all samples, with similar residual sugar values (Table 1).

Table 1

Chemical-physical composition of wines during alcoholic fermentation and long post-fermentative maceration
	pH		Reducing Sugars (g/L)		Ethanol content (% w/v)		Total Titratable Acidity (g/L of tartaric acid )		Volatile Acidity (g/L of acetic acid)		Malic Acid (g/L)		Lactic Acid (g/L)		Dry Extract (g/L)		Glycerol (g/L)
	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB
Must	3.39 ± 0.01	3.44 ± 0.09	251.99 ± 6.22	251.85 ± 8.01	< LOQ	< LOQ	3.78 ± 0.09	3.85 ± 0.07	< LOQ	< LOQ	1.92 ± 0.01	1.99 ± 0.01	< LOQ	< LOQ	277.43 ± 6.54	278.65 ± 8.45	< LOQ	< LOQ
Day 3	3.41 ± 0.02	3.40 ± 0.08	150.27 ± 3.44	203.40 ± 6.32	5.48 ± 0.01	3.14 ± 0.01	6.91 ± 0.08	6.16 ± 0.11	0.20 ± 0.02	0.37 ± 0.02	1.37 ± 0.01	1.44 ± 0.01	0.61 ± 0.01	0.48 ± 0.01	191.19 ± 4.52	239.56 ± 7.12	4.51 ± 0.12	4.38 ± 0.11
Day 8	3.35 ± 0.01	3.57 ± 0.11	2.84 ± 0.02	55.03 ± 2.28	14.47 ± 0.22	11.16 ± 0.17	6.56 ± 0.11	6.13 ± 0.09	0.42 ± 0.02	0.41 ± 0.03	0.85 ± 0.01	1.38 ± 0.01	0.97 ± 0.01	0.55 ± 0.01	35.43 ± 2.32	100.61 ± 2.32	8.63 ± 0.21	7.52 ± 0.16
Day 13	3.36 ± 0.01	3.54 ± 0.08	1.85 ± 0.01	1.53 ± 0.01	14.51 ± 0.24	14.54 ± 0.22	6.31 ± 0.08	6.13 ± 0.08	0.43 ± 0.03	0.49 ± 0.03	0.84 ± 0.00	1.29 ± 0.01	0.95 ± 0.01	0.65 ± 0.01	33.45 ± 1.12	45.82 ± 1.45	8.66 ± 0.19	9.29 ± 0.18
Day 20	3.52 ± 0.01	3.51 ± 0.07	1.93 ± 0.01	1.47 ± 0.02	14.59 ± 0.29	14.59 ± 0.24	5.06 ± 0.07	6.02 ± 0.07	0.47 ± 0.04	0.48 ± 0.02	< LOQ	0.86 ± 0.01	1.83 ± 0.01	1.15 ± 0.01	33.41 ± 1.54	34.01 ± 1.24	8.69 ± 0.17	9.38 ± 0.21
Day 30	3.51 ± 0.02	3.50 ± 0.09	1.82 ± 0.02	1.42 ± 0.01	14.56 ± 0.27	14.55 ± 0.26	4.98 ± 0.09	4.85 ± 0.09	0.45 ± 0.03	0.42 ± 0.02	< LOQ	< LOQ	1.89 ± 0.02	2.10 ± 0.01	33.47 ± 1.63	34.53 ± 1.23	8.72 ± 0.21	9.36 ± 0.19
Day 40	3.52 ± 0.01	3.55 ± 0.12	1.84 ± 0.01	1.27 ± 0.01	14.54 ± 0.25	14.55 ± 0.25	4.89 ± 0.12	4.75 ± 0.09	0.43 ± 0.02	0.45 ± 0.02	< LOQ	< LOQ	1.85 ± 0.02	2.11 ± 0.02	33.43 ± 1.21	34.13 ± 1.14	8.60 ± 0.19	9.85 ± 0.15
Day 50	3.51 ± 0.02	3.53 ± 0.11	1.87 ± 0.01	1.25 ± 0.02	14.53 ± 0.26	14.51 ± 0.23	4.86 ± 0.11	4.79 ± 0.08	0.44 ± 0.02	0.44 ± 0.02	< LOQ	< LOQ	1.91 ± 0.02	2.09 ± 0.02	30.47 ± 1.74	33.90 ± 1.27	8.65 ± 0.13	9.81 ± 0.16
Day 60	3.55 ± 0.01	3.50 ± 0.09	1.74 ± 0.01	1.21 ± 0.03	14.53 ± 0.25	14.52 ± 0.24	4.80 ± 0.09	4.78 ± 0.12	0.45 ± 0.03	0.47 ± 0.03	< LOQ	< LOQ	1.93 ± 0.02	2.10 ± 0.02	30.18 ± 1.54	33.62 ± 1.21	8.60 ± 0.15	9.83 ± 0.14
Day 70	3.52 ± 0.01	3.55 ± 0.08	1.72 ± 0.02	1.21 ± 0.01	14.54 ± 0.24	14.54 ± 0.27	4.77 ± 0.08	4.59 ± 0.11	0.49 ± 0.02	0.44 ± 0.02	< LOQ	< LOQ	1.89 ± 0.01	2.11 ± 0.01	30.10 ± 1.24	32.68 ± 1.14	8.63 ± 0.12	9.84 ± 0.21
Day 90	3.48 ± 0.01	3.52 ± 0.07	1.72 ± 0.01	1.11 ± 0.01	14.53 ± 0.23	14.51 ± 0.23	4.86 ± 0.07	4.56 ± 0.12	0.47 ± 0.02	0.45 ± 0.02	< LOQ	< LOQ	1.85 ± 0.02	2.11 ± 0.01	30.09 ± 1.21	32.76 ± 1.15	8.64 ± 0.14	9.87 ± 0.19
Day 110	3.45 ± 0.02	3.51 ± 0.09	1.73 ± 0.01	1.12 ± 0.01	14.55 ± 0.24	14.52 ± 0.22	4.85 ± 0.09	4.59 ± 0.09	0.42 ± 0.03	0.47 ± 0.04	< LOQ	< LOQ	1.90 ± 0.02	2.09 ± 0.02	30.59 ± 1.11	32.75 ± 1.16	8.69 ± 0.21	9.86 ± 0.20
Day 130	3.50 ± 0.01	3.54 ± 0.09	1.73 ± 0.02	1.12 ± 0.01	14.52 ± 0.22	14.52 ± 0.21	4.81 ± 0.09	4.55 ± 0.08	0.48 ± 0.03	0.49 ± 0.04	< LOQ	< LOQ	1.91 ± 0.03	2.10 ± 0.02	30.49 ± 1.14	32.76 ± 1.18	8.68 ± 0.19	9.85 ± 0.19
Day 150*	3.48 ± 0.01	3.51 ± 0.08	1.73 ± 0.03	1.12 ± 0.01	14.54 ± 0.21	14.53 ± 0.24	4.83 ± 0.08	4.56 ± 0.09	0.46 ± 0.02	0.46 ± 0.03	< LOQ	< LOQ	1.92 ± 0.03	2.11 ± 0.02	30.62 ± 1.19	32.99 ± 1.24	8.65 ± 0.21	9.87 ± 0.18

All trials reached the same ethanol concentration (14.5% v/v). The pH value slightly increased during alcoholic fermentation in all trials (pH = 3.5) and total titratable acidity, decreased due to the precipitation of potassium bitartrate in the alcoholic medium (Coulter et al., 2015), with an average value of 5.45 g/L (expressed as tartaric acid) (Table 1). The titratable acidity further decreased during post-fermentative maceration, reaching the value of 4.8 g/L in steel tank trial and 4.6 g/L in oak barrel trial. The volatile acidity, Table 1, at the end of alcoholic fermentation was less than 0.5 g/L in all trials and remained unchanged during post-fermentative maceration. The glycerol content (Table 1) at the end of vinification process was higher in oak barrel trials (10 g/L) than in steel tanks trials (9 g/L). The malolactic fermentation started at the same time as the alcoholic fermentation (3rd day after crushing), as often occurs in hot environments when the supply of SO₂ to the crushed product is limited. The degradation of malic acid was more rapid in steel tanks trials than in oak barrel trials, this fact could be attributable to the effect of oak hydrolysable tannins on malolactic bacteria. The malolactic fermentation ended on 20th day after crushing in steel tanks trials, whereas it ended on 30th day in oak barrel trials (Table1). The dry extract was about 35 g/L in all trials (Table 1).

3.2 Phenolic compounds

The total polyphenols content increased from crushing until 30th day after crushing in all trials (Fig. 1a). Steel tank post fermentative maceration trial reached the value of 2330 mg/L of (+)-catechin on 40th day of maceration, whereas significantly higher values (about more than 20%) were observed in oak barrel post fermentative maceration trial, in which the mean value of 2900 mg/L ((+)-catechin) was kept from 30th to 70th day after crushing.

The evolution of total flavonoids followed almost the same trend of total polyphenols (Fig. 1b). The flavonoid content increased from crushing until the 40th day after crushing in steel tank post fermentative maceration trial, reaching the value of 2400 mg/L ((+)-catechin). Significantly higher values were observed in oak barrel post fermentative maceration trial, in which the mean value of 3000 mg/L ((+)-catechin) was kept from 20th to 70th day after crushing.

The content of total anthocyanins increased from crushing until 13th day, when the content of about 700 mg/L (malvidin-3-glucoside) was reached in all trials (Fig. 1c). Total anthocyanins content gradually decreased during post fermentative maceration, reaching the contents of 200 mg/L of malvidin-3-glucoside in steel tank trials and of 280 mg/L of malvidin-3-glucoside in oak barrel trials.

Monomer anthocyanins content increased from crushing, reaching the maximum value of 555 mg/L (malvidin-3-glucoside) on 8th day after crushing in steel tank trials and the mean value of 450 mg/L (malvidin-3-glucoside) between 8th and 13th day after crushing in oak barrel trials (Fig. 1d). Then, a strong reduction was observed during post fermentative maceration with a content of 100 mg/L of malvidin-3-glucoside in steel trial and 130 mg/L of malvidin-3-glucoside in oak barrel trial, with no significant differences.

Figure 2 shows the anthocyanin profiles (%) of Cabernet Sauvignon trials during the alcoholic fermentation and the post-fermentative maceration. The anthocyanin profile was characterized by the prevalence of trisubstituted anthocyanins (malvidin, petunidin and delphinidin-3-glucoside). The content of malvidin-3-glucoside, that is the compound most involved in the formation of the wine colour, is about 58% in steel tank trials, and about 65% in oak barrel trials, even though no significant differences were observed among the trials.

The contents of petunidin-3-glucoside and delphinidin-3-glucoside remained almost constant during the alcoholic fermentation and post-fermentative maceration (6.5% and 1.5%, respectively), with no significant differences among the trials.

Cyanidin-3-glucoside content was about 0.6% in steel tank trials, that is significantly higher than the oak barrel trial content (0.35%).

Peonidin-3-glucoside content is about 3.5% in all trials, with no significant differences among them.

Acylated anthocyanins were mainly represented by acetylated forms if compared to p-coumaroylated ones. Acetylated anthocyanins content remained almost constant during alcoholic fermentation and post fermentative maceration in all trials, with the mean value of 24% in steel tank trial and 20% in oak barrel trials, even though no significant differences were observed.

p-coumaroylated anthocyanins content was about 4.5% in all trials and remained constant during alcoholic fermentation and post fermentative maceration with no significant differences among the trials.

The ratio acetylated/p-coumaroylated anthocyanins ranged from 4 to 6.

Figure 3 shows the evolution of hydroxycinnamoyl tartaric acids in Cabernet Sauvignon trials during alcoholic fermentation and post-fermentative maceration.

All hydroxycinnamoyl tartaric acids (HCTA), shown as the sum of cis and trans configuration, followed almost the same evolution in all trials, with an increasing trend during alcoholic fermentation, followed by a decreasing trend during post fermentative maceration, with significantly higher values in oak barrel trials. In particular, cis and trans caffeoyl tartaric acid content reached the maximum value of 87 mg/L on 20th day after crushing in steel tank trials, and the maximum value of 117 mg/L on 20th day after crushing in oak barrel trials. Cis and trans p-coumaroyl tartaric acid content reached the maximum value of 47 mg/L on 13th day after crushing in steel tank trials, and the maximum value of 60 mg/L in oak barrel trials. Cis and trans feruloyl tartaric acid content reached the maximum value of 1.6 mg/L on 13th day after crushing in steel tank trials, and the maximum value of 3.2 mg/L on 13th day after crushing in oak barrel trials.

On 150th day the two isomer forms of caffeoyl tartaric acid showed values of 50 mg/L in steel trials and 86 mg/L in oak barrel trials; coumaroyl tartaric acid showed values of 20 mg/L in steel trials and 39 mg/L in oak barrel trials; feruloyl tartaric acid showed values of 1.2 mg/L in steel trials and 1.6 mg/L in oak barrel trials. The contents of HCTA in oak barrel trials remained significantly higher than the content in steel tank trials until the end of post fermentative maceration.

Caffeic acid content reached the maximum value of 3.1 mg/L on 13th day after crushing in steel tank trials, and the maximum value of 3.3 mg/L in oak barrel trials on the same date. Then, the content slightly decreased in all trials, even though the content in oak barrel trial remained significantly higher than that in steel tank trial.

Figure 4 shows the evolution of flavonols content in Cabernet Sauvignon wines during alcoholic fermentation and post-fermentative maceration.

Flavonols, compounds belonging to the class of flavonoids, are shown as the sum of 3-glucuronide and 3-glucoside forms except for the syringetin, that was determined only in the 3-glucoside form (Fig. 4).

Myricetin-3-glucuronide and 3-glucoside content increased during alcoholic fermentation reaching the maximum value of 4.5 mg/L on 20th day after crushing in steel tank trials and the maximum value of 6.4 mg/L on 8th day after crushing in oak barrel trials. Then, the content decreased during post fermentative maceration, even though the content in oak barrel trial was significantly higher than that in steel tank trial on 150th day after crushing.

Quercetin-3-glucuronide and 3-glucoside content reached the maximum value of 9.2 mg/L between 8th and 13th day after crushing in steel tank trials and the maximum value of 9.3 mg/L on 8th day after crushing in oak barrel trials. The content decreased during post fermentative maceration, reaching the value of 3.4 mg/L in steel tank post fermentative maceration trial and the value of 5.5 mg/L in oak barrel post fermentative maceration trial, that are significantly different.

Kampferol-3-glucuronide and 3-glucoside content reached the maximum value of 0.8 mg/L between 8th and 13th day after crushing in steel tank trials. Then, the content slightly decreased until 150th day after crushing reaching the value of 0.5 mg/L. In oak barrel trials the content of Kaempferol remained almost constant during the whole process and no significant differences were observed with the content of steel tank trial on 150th day.

Syringetin-3-glucoside content in steel tank trials reached the maximum value of 3.6 mg/L between 3rd and 8th day after crushing, followed by a decrease during post fermentative maceration, reaching the value of 0.5 mg/L on 150th day.

In oak barrel trials the content reached the minimum value of 2.2 mg/L on 8th day after crushing. However, the content increased during post fermentative maceration, and remained significantly higher than that observed in steel tank trials until the end of the process.

The evolution of the different classes of phenolic compounds during the long contact with the solid parts of the grapes suggested that the post fermentative maceration provide a higher content of these substances in wine, especially total polyphenols, and total flavonoids in oak barrel trials. The losses recorded were limited especially in oak barrel trials.

3.2.1 Modelized Anthocyanin first stage

As it is possible to observe from Fig. 5 and Table 2, the initial speed of anthocyanin extraction for PFMS resulted greater than PFMB (β parameter), also the decreasing in extraction speed resulted greater for PFMS (2α). The net effect was that PFMS reached the maximum concentration of anthocyanin after 8 days while PFMB after 13 days.

Table 2

parameters of the anthocyanins first stage
Anthocyanin first stage	PFMS	PFMB
α	-4.71	-4.59
β	107.39	103.49
γ	156.85	137.15
R²	1.0000	0.9951
Days max	8	13
Max conc reached	714.31	712.80
2α	-9.43	-9.17

3.2.2 Modelized anthocyanin second stage

As it is possible to see from the Fig. 5 and from the Table 3 PFMS showed a greater “c” parameter and a delta a-b more negative than PFMB determining a faster decreasing in anthocyanin. At day 150 we still have registered a greater concentration of anthocyanin in PFMB.

Table 3

anthocyanin stage II
Parameter	PFMS	PFMB
b	962.97	780.82
c	3.47∙ 10^− 2	9.58 ∙ 10^− 3
a (predicted horizontal asymptote)	222.32	96.96
Concentration at 150 days	202.99	276.51
R²	0.9303	0.9637

3.2.3 Modelized non-anthocyanic flavonoids

From the Fig. 6 and Table 4 it is possible to note that PFMS showed a slightly greater “c” parameter, or rather it approaches slightly faster to the asymptote of non-anthocyanic flavonoids (NAF) compared to PFMB, however PFMB showed a net greater concentration of NAF.

Table 4

non-anthocyanic flavonoids parameters
Parameter	PFMS	PFMB
b	221.85	165.52
c	1.27 ∙ 10^− 1	1.12∙ 10^− 1
a	1619.00	2179.70
Concentration at 150 days	1671.78	2181.65
R²	0.9429	0.9811

3.3 Volatile organic compounds

Volatile organic compounds (VOCs) of wine belong to various chemical classes such as alcohols, ester, acids, aldehydes, and volatile phenols. Tables 5a and 5b show volatile organic compounds (mg/L) of Cabernet Sauvignon wines during alcoholic fermentation and post-fermentative maceration.

Table 5

a - Volatile organic compounds (g/L) of wine *Cabernet Sauvignon* during alcoholic fermentation and long post-fermentative maceration
Time and phase	Total Alcohols		Total Esters		Total Acids		Total Phenols
Alcoholic fermentation	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB	PFMS	PFMB
Day 30	36.52 ± 1.43 A,a	125.46 ± 4.93 E,b	4.43 ± 0.17 A,a	6.19 ± 0.24 A,b	6.19 ± 0.24 E,b	3.78 ± 0.15 A,a	0.97 ± 0.04 I, b	0.51 ± 0.02 E
Day 8	75.86 ± 2.98 B,a	164.20 ± 6.45 H,b	10.37 ± 0.41 B	11.66 ± 0.46 B	4.25 ± 0.17 B,a	5.36 ± 0.21 B,b	0.53 ± 0.02 D	0.58 ± 0.02 F
Day 13	94.74 ± 3.72 D,a	173.47 ± 6.81 I,b	25.13 ± 0.99 C,b	20.37 ± 0.80 C,a	8.45 ± 0.33 G,a	13.61 ± 0.53 EF,b	0.84 ± 0.03 H,b	0.61 ± 0.02 GH
Post-fermentation maceration
Day 20	86.17 ± 3.38 C,a	155.75 ± 6.12 G,b	23.29 ± 0.91 C	24.84 ± 0.98 D	7.36 ± 0.29 F,a	13.28 ± 0.52 E,b	0.45 ± 0.02 C	0.65 ± 0.02 IJ,b
Day 30	87.87 ± 3.45 CD,a	137.75 ± 5.41 F,b	34.31 ± 1.35 D,b	24.32 ± 0.96 D,a	5.69 ± 0.22 D,a	12.95 ± 0.51 E,b	0.58 ± 0.02 E,b	0.39 ± 0.02 D
Day 40	171.46 ± 6.74 G,b	138.72 ± 5.45 F,a	45.83 ± 1.80 F,b	29.30 ± 1.15 FG,a	9.43 ± 0.37 H,a	16.71 ± 0.66 G,b	0.71 ± 0.03 G	0.68 ± 0.03 J
Day 50	200.11 ± 7.86 H	139.99 ± 5.50 F,a	45.21 ± 1.78 F,b	36.06 ± 1.42 I,a	10.36 ± 0.41 I,a	19.86 ± 0.78 H,b	0.64 ± 0.02 F	0.58 ± 0.02 FG
Day 60	140.17 ± 5.51 F	122.83 ± 4.82 E	36.67 ± 1.44 E	34.57 ± 1.36 I	6.27 ± 0.25 E,a	14.35 ± 0.56 F,b	0.58 ± 0.02 E	0.64 ± 0.02 HI
Day 70	110.62 ± 4.35 E	93.89 ± 3.69 D	36.27 ± 1.42 DE	32.24 ± 1.27 H	5.46 ± 0.21 D,a	10.83 ± 0.43 D,b	0.51 ± 0.02 D,b	0.42 ± 0.02 D
Day 90	81.07 ± 3.18 BC,b	64.95 ± 2.55 A,a	35.88 ± 1.41 DE,b	29.92 ± 1.18 G,a	4.65 ± 0.18 C,a	7.30 ± 0.29 C,b	0.44 ± 0.02 C,b	0.20 ± 0.01 AB
Day 110	85.66 ± 3.36 C,b	72.15 ± 2.83 A,a	36.33 ± 1.43 DE,b	27.29 ± 1.07 E,a	5.49 ± 0.22 D,b	2.81 ± 0.11 A,a	0.39 ± 0.01 B,b	0.18 ± 0.01 A
Day 130	82.90 ± 3.26 BC	79.34 ± 3.12 C	34.47 ± 1.35 D,b	27.92 ± 1.10 EF,a	3.15 ± 0.12 A,a	4.96 ± 0.19 B,b	0.24 ± 0.01 A	0.23 ± 0.01 BC
Day 150*	87.75 ± 3.45 CD	83.79 ± 3.29 C	35.04 ± 1.38 DE,b	27.56 ± 1.08 E,a	4.07 ± 0.16 B,b	3.43 ± 0.13 A,a	0.24 ± 0.01 A	0.23 ± 0.01 C
PFMS: post-fermentative maceration in steel; PFMB: post-fermentative maceration in barrel;
* racking PFMS and PFMB trials
n.d.: not detected
Values are expressed as mean ± standard deviation (n = 3).
Uppercase letters indicate differences over time within a single column (post hoc), lowercase letters indicate differences between samples, PFMS and PFMB, (t test).

Table 5

b - Volatile organic compounds (mg/L) of wine *Cabernet Sauvignon* during alcoholic fermentation and post-fermentative maceration
		Alcoholic fermentation			Post-fermentation maceration
		Day 3	Day 8	Day 13	Day 20	Day 30	Day 40	Day 50	Day 60	Day 70	Day 90	Day 110	Day 130	Day 150*
1-hexanol	PFMS	1.73 ± 0.07 D	2.10 ± 0.08 E,b	2.95 ± 0.11 H,b	2.78 ± 0.11 G,b	2.70 ± 0.10 FG,b	2.63 ± 0.10 F	3.05 ± 0.12 H,b	1.76 ± 0.07 D,b	1.59 ± 0.06 C	1.43 ± 0.05 B	2.20 ± 0.08 E,b	1.65 ± 0.06 CD,b	1.16 ± 0.04 A
1-hexanol	PFMB	1.69 ± 0.06 DE	1.77 ± 0.07 E,a	1.89 ± 0.07 F,a	1.99 ± 0.08 G,a	2.10 ± 0.08 H,a	2.35 ± 0.09 I	2.49 ± 0.10 J,a	2.09 ± 0.08 H,a	1.66 ± 0.06 D	1.23 ± 0.05 C	1.15 ± 0.04 B,a	1.07 ± 0.04 A,a	1.18 ± 0.05 BC
trans-3-Hexenol	PFMS	0.12 ± 0.00 B,a	0.19 ± 0.01 C	0.20 ± 0.01 CD	0.26 ± 0.01 E,b	0.19 ± 0.01 C	0.12 ± 0.00 B,a	0.33 ± 0.01 F,b	0.31 ± 0.01 F,b	0.22 ± 0.01 D,b	0.12 ± 0.00 B,b	0.03 ± 0.00 A,a	0.03 ± 0.00 A,a	0.03 ± 0.00 A,a
trans-3-Hexenol	PFMB	0.16 ± 0.01 E,b	0.18 ± 0.01 G	0.20 ± 0.01 I	0.13 ± 0.01 D,a	0.18 ± 0.01 FG	0.19 ± 0.01 H,b	0.17 ± 0.01 F,a	0.15 ± 0.01 E,a	0.12 ± 0.00 C,a	0.09 ± 0.00 A,a	0.10 ± 0.00 B,b	0.12 ± 0.00 C,b	0.11 ± 0.00 B,b
cis-3-Hexenol	PFMS	0.06 ± 0.00 D,b	0.04 ± 0.00 C,b	0.02 ± 0.00 A,b	0.08 ± 0.00 F	0.09 ± 0.00 G,b	0.11 ± 0.00 H,b	0.16 ± 0.01 I,b	0.07 ± 0.00 EF,b	0.07 ± 0.00 DE,b	0.06 ± 0.00 D,b	0.04 ± 0.00 C,b	0.05 ± 0.00 C	0.03 ± 0.00 B,a
cis-3-Hexenol	PFMB	0.03 ± 0.00 BC,a	0.03 ± 0.00 D,a	0.03 ± 0.00 B,a	0.08 ± 0.00 H	0.06 ± 0.00 G,a	0.04 ± 0.00 E,a	0.06 ± 0.00 F,a	0.04 ± 0.00 E,a	0.03 ± 0.00 BCD,a	0.02 ± 0.00 A,a	0.03 ± 0.00 CD,a	0.04 ± 0.00 E	0.04 ± 0.00 E,b
2-Phenylethanol*	PFMS	35.41 ± 1.35 A,a	75.30 ± 2.88 B,a	93.56 ± 3.58 D,a	84.73 ± 3.24 C,a	86.54 ± 3.31 CD,a	172.36 ± 6.5 G,b	200.98 ± 7.6 H,b	141.12 ± 5.3 F	111.18 ± 4.2 E,b	81.25 ± 3.11 BC,b	85.04 ± 3.25 C	82.87 ± 3.17 BC	88.35 ± 3.38 CD
2-Phenylethanol*	PFMB	126.56 ± 4.8 E,b	166.33 ± 6.3 H,b	175.69 ± 6.7 I,b	157.16 ± 6.0 G,b	138.63 ± 5.3 F,b	139.22 ± 5.3 F,a	140.30 ± 5.3 F,a	123.20 ± 4.7 E D	94.09 ± 3.60 D,a	64.98 ± 2.48 A,a	72.38 ± 2.77 BAB	79.78 ± 3.05 CBC	84.20 ± 3.22 CBC
Benzyl alcohol*	PFMS	0.21 ± 0.01 A,a	0.33 ± 0.01 B,a	0.64 ± 0.02 D,b	0.71 ± 0.03 E	0.78 ± 0.03 FG,b	1.01 ± 0.04 H,b	1.14 ± 0.04 I,b	0.80 ± 0.03 G	0.63 ± 0.02 D	0.46 ± 0.02 C	0.74 ± 0.03 EF,b	0.60 ± 0.02 D	0.62 ± 0.02 D
Benzyl alcohol*	PFMB	0.51 ± 0.02 B,b	0.46 ± 0.02 A,b	0.49 ± 0.02 B,a	0.71 ± 0.03 F	0.62 ± 0.02 E,a	0.78 ± 0.03 G,a	0.86 ± 0.03 H,a	0.75 ± 0.03 G	0.59 ± 0.02 D	0.43 ± 0.02 A	0.48 ± 0.02 B,a	0.53 ± 0.02 C	0.59 ± 0.02 D
Ethyl 3-hydroxy-butanoate	PFMS	0.01 ± 0.00 A,a	0.06 ± 0.00 BC,a	0.07 ± 0.00 CD,b	0.11 ± 0.00 F,b	0.16 ± 0.01 H,b	0.15 ± 0.01 G,b	0.18 ± 0.01 I,b	0.08 ± 0.00 E	0.07 ± 0.00 DE,b	0.07 ± 0.00 CD,b	0.06 ± 0.00 B,b	0.07 ± 0.00 BC,b	0.07 ± 0.00 CD,b
Ethyl 3-hydroxy-butanoate	PFMB	0.11 ± 0.00 GH,b	0.11 ± 0.00 G,b	0.05 ± 0.00 D,a	0.06 ± 0.00 DE,a	0.06 ± 0.00 DE,a	0.10 ± 0.00 F,a	0.11 ± 0.00 H,a	0.09 ± 0.00 F	0.06 ± 0.00 E,a	0.03 ± 0.00 A,a	0.03 ± 0.00 B,a	0.04 ± 0.00 C,a	0.04 ± 0.00 C,a
Ethyl 4-hydroxy-butyrate	PFMS	0.53 ± 0.02 A,b	3.67 ± 0.14 E	15.81 ± 0.60 H,b	11.39 ± 0.44 G,b	11.07 ± 0.42 G,b	11.36 ± 0.43 G,b	9.82 ± 0.38 F,b	1.17 ± 0.04 AB,a	1.76 ± 0.07 BC,a	2.34 ± 0.09 CD,a	2.35 ± 0.09 CD,a	2.39 ± 0.09 CD,a	2.85 ± 0.11 DE
Ethyl 4-hydroxy-butyrate	PFMB	0.00 ± 0.00 A,a	3.87 ± 0.15 D	10.08 ± 0.39 H,a	6.64 ± 0.25 F,a	3.20 ± 0.12 C,a	6.78 ± 0.26 FG,a	7.16 ± 0.27 G,a	6.38 ± 0.24 F,b	5.30 ± 0.20 E,b	4.23 ± 0.16 D,b	2.09 ± 0.08 B B	3.02 ± 0.12 C,b	2.46 ± 0.09 B
γ-nonalactone	PFMS	0.00 ± 0.00 A,a	0.05 ± 0.00 E,b	0.07 ± 0.00 G,b	0.06 ± 0.00 F,b	0.04 ± 0.00 D,b	0.07 ± 0.00 G,b	0.09 ± 0.00 I,b	0.11 ± 0.00 J,b	0.08 ± 0.00 H,b	0.04 ± 0.00 D,b	0.02 ± 0.00 B	0.03 ± 0.00 C,b	0.03 ± 0.00 C,b
γ-nonalactone	PFMB	0.07 ± 0.00 H,b	0.04 ± 0.00 DE,a	0.03 ± 0.00 DE,a	0.03 ± 0.00 C,a	0.02 ± 0.00 B,a	0.05 ± 0.00 G,a	0.04 ± 0.00 F,a	0.04 ± 0.00 EF,a	0.03 ± 0.00 D,a	0.03 ± 0.00 C,a	0.02 ± 0.00 B	0.01 ± 0.00 A,a	0.02 ± 0.00 B,a
Diethyl malate*	PFMS	0.00 ± 0.00 A,a	0.03 ± 0.00 B,a	0.10 ± 0.00 D,b	0.05 ± 0.00 C,a	0.23 ± 0.01 J,b	0.21 ± 0.01 I,b	0.24 ± 0.01 J,b	0.19 ± 0.01 H,b	0.17 ± 0.01 G,b	0.15 ± 0.01 F,b	0.17 ± 0.01 G,b	0.12 ± 0.00 E,b	0.14 ± 0.01 F,b
Diethyl malate*	PFMB	0.09 ± 0.00 F,b	0.04 ± 0.00 B,b	0.05 ± 0.00 B,a	0.08 ± 0.00 E,b	0.11 ± 0.00 H,a	0.12 ± 0.00 I,a	0.10 ± 0.00 G,a	0.08 ± 0.00 E,a	0.05 ± 0.00 C,a	0.03 ± 0.00 A,a	0.04 ± 0.00 B,a	0.06 ± 0.00 D,a	0.06 ± 0.00 D,a
Isoamyl lactate	PFMS	0.19 ± 0.01 B,b	0.15 ± 0.01 A,a	0.23 ± 0.01 C,a	0.15 ± 0.01 A,a	0.39 ± 0.01 F,a	0.49 ± 0.02 I,a	0.44 ± 0.02 H,a	0.35 ± 0.01 E,a	0.38 ± 0.01 F,a	0.41 ± 0.02 G	0.29 ± 0.01 D,a	0.39 ± 0.02 FG,a	0.55 ± 0.02 J
Isoamyl lactate	PFMB	0.14 ± 0.01 A,a	0.42 ± 0.02 B,b	0.66 ± 0.03 D,b	0.82 ± 0.03 E,b	0.67 ± 0.03 D,b	0.84 ± 0.03 E,b	0.96 ± 0.04 F,b	0.95 ± 0.04 F,b	0.68 ± 0.03 D,b	0.42 ± 0.02 B	0.54 ± 0.02 C,b	0.65 ± 0.02 D,b	0.51 ± 0.02 C
Butyrolactone	PFMS	0.05 ± 0.00 A,a	0.52 ± 0.02 D,a	0.95 ± 0.04 I,b	0.99 ± 0.04 I	0.72 ± 0.03 F,a	0.69 ± 0.03 F,b	0.88 ± 0.03 H,b	0.78 ± 0.03 G,b	0.56 ± 0.02 DE,b	0.33 ± 0.01 B B	0.60 ± 0.02 E,b	0.43 ± 0.02 C,b	0.35 ± 0.01 B
Butyrolactone	PFMB	0.11 ± 0.00 A,b	0.99 ± 0.04 H,b	0.64 ± 0.02 F,a	0.91 ± 0.03 G	1.62 ± 0.06 I,b	0.48 ± 0.02 E,a	0.42 ± 0.02 DE,a	0.43 ± 0.02 DE,a	0.40 ± 0.02 D,a	0.38 ± 0.01 D D	0.30 ± 0.01 C,a	0.21 ± 0.01 B,a	0.38 ± 0.01 D
Isoamyl 4-hydroxybutyrate	PFMS	0.20 ± 0.01 A,b	0.37 ± 0.01 D	0.29 ± 0.01 BC,a	0.21 ± 0.01 A,a	0.39 ± 0.01 D,a	1.02 ± 0.04 G,b	0.63 ± 0.02 F,a	0.45 ± 0.02 E,a	0.35 ± 0.01 D,a	0.26 ± 0.01 B,b	0.31 ± 0.01 C,b	0.17 ± 0.01 A,a	0.21 ± 0.01 A
Isoamyl 4-hydroxybutyrate	PFMB	0.13 ± 0.01 A,a	0.35 ± 0.01 D	1.16 ± 0.04 I,b	0.90 ± 0.03 H,b	0.79 ± 0.03 G,b	0.67 ± 0.03 F,a	0.86 ± 0.03 H,b	0.88 ± 0.03 H,b	0.52 ± 0.02 E,b	0.16 ± 0.01 AB,a	0.20 ± 0.01 BC,a	0.25 ± 0.01 C,b	0.22 ± 0.01 C
Ethyl lactate*	PFMS	0.03 ± 0.00 A,a	0.14 ± 0.01 A,a	0.21 ± 0.01 A,a	0.28 ± 0.01 A,a	0.23 ± 0.01 A,a	0.18 ± 0.01 A,a	2.01 ± 0.08 B,a	3.84 ± 0.15 C,a	3.80 ± 0.15 C,a	3.75 ± 0.14 C	4.80 ± 0.18 D,b	5.17 ± 0.20 D,b	5.60 ± 0.21 E,b
Ethyl lactate*	PFMB	1.39 ± 0.05 A,b	1.59 ± 0.06 AB,b	1.79 ± 0.07 B,b	5.22 ± 0.20 G,b	4.26 ± 0.16 DE,b	4.83 ± 0.18 F,b	6.18 ± 0.24 H,b	6.09 ± 0.23 H,b	4.96 ± 0.19 FG,b	3.83 ± 0.15 C	4.02 ± 0.15 CD,a	4.22 ± 0.16 DE,a	4.43 ± 0.17 E,a
Monoethyl succinate*	PFMS	0.00 ± 0.00 A,a	0.50 ± 0.02 AB,b	0.97 ± 0.04 B,b	0.93 ± 0.04 B,b	10.94 ± 0.42 H,b	9.54 ± 0.36 G,b	7.04 ± 0.27 F,b	4.39 ± 0.17 E,b	3.07 ± 0.12 D,b	1.75 ± 0.07 C,b	2.58 ± 0.10 D,b	0.90 ± 0.03 B,b	1.67 ± 0.06 C,b
Monoethyl succinate*	PFMB	0.11 ± 0.00 E,b	0.16 ± 0.01 H,a	0.21 ± 0.01 K,a	0.20 ± 0.01 J,a	0.19 ± 0.01 I,a	0.11 ± 0.00 EF,a	0.12 ± 0.00 F,a	0.13 ± 0.01 G,a	0.09 ± 0.00 D,a	0.04 ± 0.00 A,a	0.05 ± 0.00 AB,a	0.06 ± 0.00 B,a	0.08 ± 0.00 C,a
Diethyl succinate*	PFMS	0.02 ± 0.00 A,a	0.10 ± 0.00 A,a	2.94 ± 0.11 B,b	4.72 ± 0.18 BC,a	6.51 ± 0.25 C,a	18.86 ± 0.72 D,b	21.24 ± 0.81 E,b	22.98 ± 0.88 EFG,b	23.83 ± 0.91 FG,b	24.68 ± 0.94 G,b	23.42 ± 0.90 FG,b	23.42 ± 0.90 FG,b	22.61 ± 0.86 EF,b
Diethyl succinate*	PFMB	0.12 ± 0.00 A,b	0.21 ± 0.01 A,b	1.88 ± 0.07 B,a	6.35 ± 0.24 C,b	10.83 ± 0.41 D,b	12.72 ± 0.49 E,a	18.42 ± 0.70 FG,a	17.48 ± 0.67 F,a	18.66 ± 0.71 FGH,a	19.84 ± 0.76 H,a	19.22 ± 0.73 GH,a	18.59 ± 0.71 FGH,a	18.40 ± 0.70 FG,a
Ethyl hexanoate	PFMS	0.55 ± 0.02 B	1.52 ± 0.06 G,b	0.57 ± 0.02 B,a	0.85 ± 0.03 D	0.93 ± 0.04 E	1.01 ± 0.04 F,a	0.96 ± 0.04 EF	0.84 ± 0.03 D,a	0.83 ± 0.03 D,b	0.82 ± 0.03 D,b	0.75 ± 0.03 C,b	0.56 ± 0.02 B	0.47 ± 0.02 A,a
Ethyl hexanoate	PFMB	0.52 ± 0.02 C	0.74 ± 0.03 E,a	0.82 ± 0.03 F,b	0.91 ± 0.03 G	1.00 ± 0.04 H	1.37 ± 0.05 I,b	0.88 ± 0.03 G	1.00 ± 0.04 H,b	0.67 ± 0.03 D,a	0.34 ± 0.01 A,a	0.42 ± 0.02 B,a	0.50 ± 0.02 C	0.72 ± 0.03 DE,b
Ethyl octanoate	PFMS	0.52 ± 0.02 D,b	0.55 ± 0.02 F,b	0.53 ± 0.02 DE,b	0.69 ± 0.03 J,b	0.60 ± 0.02 H,b	0.57 ± 0.02 G,b	0.54 ± 0.02 EF,b	0.62 ± 0.02 I	0.54 ± 0.02 DEF	0.45 ± 0.02 B	0.50 ± 0.02 C,b	0.50 ± 0.02 C,b	0.27 ± 0.01 A,b
Ethyl octanoate	PFMB	0.25 ± 0.01 D,a	0.15 ± 0.01 B,a	0.40 ± 0.02 F,a	125.46 ± 4.93 E,b	0.11 ± 0.00 A,a	0.44 ± 0.02 G,a	0.20 ± 0.01 C,a	0.56 ± 0.02 I	0.48 ± 0.02 H	0.40 ± 0.02 F	0.32 ± 0.01 E,a	0.34 ± 0.01 E,a	0.21 ± 0.01 C,a
Ethyl decanoate	PFMS	0.10 ± 0.00 B,a	0.21 ± 0.01 CD	0.18 ± 0.01 C,a	0.51 ± 0.02 G,b	0.46 ± 0.02 F,b	0.60 ± 0.02 H,b	0.43 ± 0.02 F,b	0.27 ± 0.01 E,a	0.23 ± 0.01 D	0.19 ± 0.01 C	0.10 ± 0.00 B,b	0.10 ± 0.00 B	0.06 ± 0.00 A,a
Ethyl decanoate	PFMB	0.26 ± 0.01 GH,b	0.19 ± 0.01 C	0.24 ± 0.01 EF,b	0.23 ± 0.01 DE,a	0.22 ± 0.01 D,a	0.27 ± 0.01 H,a	0.29 ± 0.01 I,a	0.31 ± 0.01 J,b	0.25 ± 0.01 FG	0.18 ± 0.01 C	0.05 ± 0.00 A,a	0.09 ± 0.00 B	0.09 ± 0.00 B,b
Ethyl octadecanoate	PFMS	0.00 ± 0.00 A,a	0.18 ± 0.01 D,b	0.33 ± 0.01 E,b	0.45 ± 0.02 G,b	0.43 ± 0.02 G,b	0.62 ± 0.02 H,b	0.40 ± 0.02 F,b	0.18 ± 0.01 D,b	0.17 ± 0.01 D,b	0.17 ± 0.01 D,b	0.08 ± 0.00 BC,b	0.05 ± 0.00 B,b	0.10 ± 0.00 C,b
Ethyl octadecanoate	PFMB	0.04 ± 0.00 A,b	0.08 ± 0.00 D,a	0.13 ± 0.00 F,a	0.17 ± 0.01 G,a	0.20 ± 0.01 H,a	0.13 ± 0.00 F,a	0.06 ± 0.00 C,a	0.11 ± 0.00 E,a	0.08 ± 0.00 D,a	0.05 ± 0.00 B,a	0.05 ± 0.00 AB,a	0.04 ± 0.00 A,a	0.05 ± 0.00 B,a
Isoamyl acetate	PFMS	1.86 ± 0.07 I,b	1.61 ± 0.06 H,a	1.82 ± 0.07 I,a	2.31 ± 0.09 J,b	1.88 ± 0.07 I,b	1.38 ± 0.05 G,b	1.19 ± 0.05 F,b	1.06 ± 0.04 E,b	0.91 ± 0.03 D,b	0.76 ± 0.03 C,b	0.49 ± 0.02 A	0.61 ± 0.02 B,b	0.57 ± 0.02 AB,b
Isoamyl acetate	PFMB	0.50 ± 0.02 AB,a	2.24 ± 0.09 H,b	2.02 ± 0.08 G,b	2.00 ± 0.08 G,a	1.30 ± 0.05 F,a	0.84 ± 0.03 D,a	0.96 ± 0.04 E,a	0.70 ± 0.03 C,a	0.65 ± 0.02 C,a	0.60 ± 0.02 BC,a	0.53 ± 0.02 AB	0.46 ± 0.02 A,a	0.47 ± 0.02 A,a
Hexyl acetate	PFMS	0.16 ± 0.01 AB,a	0.16 ± 0.01 A,a	0.16 ± 0.01 A,a	0.17 ± 0.01 AB,a	0.19 ± 0.01 BC,a	0.21 ± 0.01 C,a	0.22 ± 0.01 C,b	0.30 ± 0.01 D,b	0.46 ± 0.02 G,b	0.62 ± 0.02 H,b	0.64 ± 0.02 H,b	0.39 ± 0.01 F,b	0.33 ± 0.01 E,b
Hexyl acetate	PFMB	0.32 ± 0.01 F,b	0.33 ± 0.01 F,b	0.32 ± 0.01 F,b	0.40 ± 0.02 G,b	0.24 ± 0.01 E,b	0.18 ± 0.01 D,a	0.08 ± 0.00 C,a	0.06 ± 0.00 BC,a	0.05 ± 0.00 B,a	0.05 ± 0.00 AB,a	0.04 ± 0.00 AB,a	0.04 ± 0.00 AB,a	0.03 ± 0.00 A,a
2-phenylethyl acetate	PFMS	0.34 ± 0.01 E,a	0.84 ± 0.03 G,b	0.60 ± 0.02 F,b	0.08 ± 0.00 A,a	0.09 ± 0.00 ABC,a	0.14 ± 0.01 D,a	0.15 ± 0.01 D,a	0.08 ± 0.00 A,a	0.08 ± 0.00 AB,a	0.09 ± 0.00 ABC,a	0.16 ± 0.01 D,b	0.13 ± 0.00 CD	0.12 ± 0.00 BCD
2-phenylethyl acetate	PFMB	2.21 ± 0.08 E,b	0.47 ± 0.02 D,a	0.43 ± 0.02 CD,a	0.34 ± 0.01 C,b	0.18 ± 0.01 AB,b	0.19 ± 0.01 AB,b	0.21 ± 0.01 AB,b	0.22 ± 0.01 B,b	0.18 ± 0.01 AB,b	0.14 ± 0.01 AB,b	0.13 ± 0.00 AB,a	0.12 ± 0.00 A	0.14 ± 0.01 AB
Isovalerianic acid	PFMS	0.47 ± 0.02 B	0.61 ± 0.02 C,a	0.76 ± 0.03 D,a	0.45 ± 0.02 B,a	1.11 ± 0.04 F,b	1.19 ± 0.05 G,b	1.85 ± 0.07 H,b	0.27 ± 0.01 A,a	0.46 ± 0.02 B	0.65 ± 0.02 C,b	0.98 ± 0.04 E,b	0.58 ± 0.02 C,b	0.61 ± 0.02 C,b
Isovalerianic acid	PFMB	0.56 ± 0.02 D	0.90 ± 0.03 FG,a	1.32 ± 0.05 I,b	1.08 ± 0.04 H,b	0.85 ± 0.03 F,a	0.95 ± 0.04 G,a	1.10 ± 0.04 H,a	0.76 ± 0.03 E,b	0.48 ± 0.02 C	0.20 ± 0.01 A,a	0.34 ± 0.01 B,a	0.48 ± 0.02 C,a	0.46 ± 0.02 C,a
Hexanoic acid	PFMS	2.53 ± 0.10 E,b	1.33 ± 0.05 B,b	2.70 ± 0.10 F,b	2.28 ± 0.09 D,b	1.85 ± 0.07 C,b	3.31 ± 0.13 G,b	3.71 ± 0.14 H,b	2.50 ± 0.10 E,b	1.89 ± 0.07 C,b	1.29 ± 0.05 B,b	1.77 ± 0.07 C,b	0.98 ± 0.04 A,b	1.20 ± 0.05 B,b
Hexanoic acid	PFMB	1.16 ± 0.04 E,a	0.92 ± 0.03 CD,a	1.38 ± 0.05 F,a	1.11 ± 0.04 E,a	0.85 ± 0.03 C,a	2.03 ± 0.08 G,a	1.96 ± 0.07 G,a	1.44 ± 0.05 F,a	1.19 ± 0.05 E,a	0.94 ± 0.04 D,a	0.44 ± 0.02 A,a	0.72 ± 0.03 B,a	0.72 ± 0.03 B,a
Octanoic acid	PFMS	1.92 ± 0.07 E	1.40 ± 0.05 C,a	4.13 ± 0.16 I	3.87 ± 0.15 H	1.55 ± 0.06 CD,a	3.29 ± 0.13 G,b	3.17 ± 0.12 G,b	2.27 ± 0.09 F	1.83 ± 0.07 E	1.38 ± 0.05 C,b	1.59 ± 0.06 D,b	0.70 ± 0.03 A,a	1.01 ± 0.04 B,a
Octanoic acid	PFMB	1.66 ± 0.06 C	2.80 ± 0.11 FG,b	3.94 ± 0.15 I	3.30 ± 0.13 H	2.65 ± 0.10 EF,b	2.56 ± 0.10 E,a	2.99 ± 0.11 G,a	2.30 ± 0.09 D	1.55 ± 0.06 C	0.80 ± 0.03 B,a	0.54 ± 0.02 A,a	0.89 ± 0.03 B,b	0.79 ± 0.03 B,a
Decanoic acid	PFMS	0.58 ± 0.02 D,b	0.51 ± 0.02 C,b	0.44 ± 0.02 B,a	0.26 ± 0.01 A,a	0.46 ± 0.02 B,b	0.72 ± 0.03 E	0.79 ± 0.03 F	0.62 ± 0.02 D	0.76 ± 0.03 F,b	0.91 ± 0.03 H,b	1.02 ± 0.04 I,b	0.86 ± 0.03 G,b	1.03 ± 0.04 I,b
Decanoic acid	PFMB	0.12 ± 0.00 B,a	0.29 ± 0.01 C,a	1.54 ± 0.06 G,b	0.82 ± 0.03 F,b	0.11 ± 0.00 AB,a	0.74 ± 0.03 E	0.81 ± 0.03 EF	0.62 ± 0.02 D	0.33 ± 0.01 C,a	0.03 ± 0.00 A,a	0.15 ± 0.01 B,a	0.26 ± 0.01 C,a	0.18 ± 0.01 B,a
9-Decenoic acid	PFMS	0.85 ± 0.03 I,b	0.41 ± 0.02 DE,a	0.33 ± 0.01 C,a	0.30 ± 0.01 C,a	0.40 ± 0.02 D,a	0.54 ± 0.02 FG,a	0.71 ± 0.03 H,a	0.57 ± 0.02 G,a	0.51 ± 0.02 F,a	0.44 ± 0.02 E,a	0.22 ± 0.01 B,a	0.06 ± 0.00 A,a	0.25 ± 0.01 B,a
9-Decenoic acid	PFMB	0.38 ± 0.01 A,a	0.60 ± 0.02 A,b	5.82 ± 0.22 D,b	7.34 ± 0.28 E,b	8.85 ± 0.34 F,b	10.89 ± 0.42 H,b	13.54 ± 0.52 I,b	9.63 ± 0.37 G,b	7.58 ± 0.29 E,b	5.52 ± 0.21 D,b	1.41 ± 0.05 B,b	2.74 ± 0.10 C,b	1.37 ± 0.05 B,b
Dodecanoic acid	PFMS	0.00 ± 0.00 A	0.11 ± 0.00 D	0.32 ± 0.01 G	0.42 ± 0.02 H	0.47 ± 0.02 I	0.64 ± 0.02 J	0.43 ± 0.02 H	0.21 ± 0.01 F	0.16 ± 0.01 E	0.11 ± 0.00 D	0.07 ± 0.00 BC	0.04 ± 0.00 B	0.08 ± 0.00 CD
Dodecanoic acid	PFMB	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Benzaldehyde	PFMS	0.07 ± 0.00 F,b	0.06 ± 0.00 D,b	0.05 ± 0.00 B,b	0.05 ± 0.00 AB,b	0.05 ± 0.00 C,b	0.05 ± 0.00 A,a	0.07 ± 0.00 F	0.09 ± 0.00 G	0.09 ± 0.00 G	0.09 ± 0.00 G	0.07 ± 0.00 E	0.07 ± 0.00 E	0.05 ± 0.00 B,a
Benzaldehyde	PFMB	0.05 ± 0.00 D,a	0.04 ± 0.00 C,a	0.03 ± 0.00 A,a	0.04 ± 0.00 BC,a	0.04 ± 0.00 B,a	0.06 ± 0.00 E,b	0.09 ± 0.00 I	0.09 ± 0.00 J	0.09 ± 0.00 J	0.09 ± 0.00 J	0.08 ± 0.00 H	0.07 ± 0.00 F	0.07 ± 0.00 G,b
Guaiacol	PFMS	0.16 ± 0.01 D,b	0.14 ± 0.01 C,a	0.21 ± 0.01 E	0.24 ± 0.01 F	0.26 ± 0.01 G,b	0.36 ± 0.01 I,b	0.23 ± 0.01 F,b	0.34 ± 0.01 H,b	0.23 ± 0.01 EF,b	0.12 ± 0.00 C,b	0.05 ± 0.00 A,b	0.07 ± 0.00 B,b	0.08 ± 0.00 B,b
Guaiacol	PFMB	0.13 ± 0.00 E,a	0.19 ± 0.01 F,b	0.22 ± 0.01 G	0.26 ± 0.01 H	0.11 ± 0.00 D,a	0.30 ± 0.01 I,a	0.19 ± 0.01 F,a	0.20 ± 0.01 F,a	0.11 ± 0.00 D,a	0.02 ± 0.00 A,a	0.04 ± 0.00 AB,a	0.05 ± 0.00 BC,a	0.06 ± 0.00 C,a
4-vinylguaiacol	PFMS	0.73 ± 0.03 H,b	0.33 ± 0.01 F	0.57 ± 0.02 G,b	0.16 ± 0.01 B,a	0.27 ± 0.01 E	0.30 ± 0.01 EF	0.33 ± 0.01 F	0.16 ± 0.01 B,a	0.19 ± 0.01 C	0.23 ± 0.01 D,b	0.27 ± 0.01 E,b	0.10 ± 0.00 A	0.11 ± 0.00 A
4-vinylguaiacol	PFMB	0.33 ± 0.01 FG,a	0.34 ± 0.01 GH	0.37 ± 0.01 I,a	0.35 ± 0.01 HI,b	0.24 ± 0.01 E	0.32 ± 0.01 FD	0.31 ± 0.01 F	0.35 ± 0.01 HI,b	0.22 ± 0.01 D	0.09 ± 0.00 B,a	0.07 ± 0.00 A,a	0.11 ± 0.00 C	0.10 ± 0.00 BC
PFMB: post-fermentative maceration in barrel
* racking PFMS and PFMB trialsn.d.: not detected Values are expressed as mean ± standard deviation (n = 3).
Uppercase letters indicate differences over time within a single column (ANOVA), lowercase letters indicate differences between samples, PFMS and PFMB, (t test).

Higher alcohols content increased during alcoholic fermentation in all trials, because of pre-fermentative enzymatic activities (lipoxygenase) and yeast activity (Nicolini et al., 1996; Houtman and Du Plessis, 1986). In PFMS the maximum content of alcohols was 200.11 mg/L on 50th day after crushing. Then, the content decreases to 87.75 mg/L on 150th day after crushing.

In PFMB the maximum content of alcohols was 173.47 mg/L on 13th day after crushing. Then, the content gradually decreased to the value 83.79 mg/L, with no significant differences with the content of steel tank trial.

The esters content showed an increasing trend during alcoholic fermentation in all trials especially given by the ethyl esters of hydroxyacids (aging esters). In steel tank trial the maximum value of 45.83 mg/L was observed between 40th and 50th day after crushing. Then, the content decreased to 35.04 mg/L on 150th day after crushing. In oak barrel trial the maximum value of 36.05 mg/L was observed between 50th and 60th day after crushing. Then, the content decreased to 27.56 mg/L on 150th day after crushing, that is significantly different from the content of PFMS.

The acids content increased during alcoholic fermentation in all trials. PFMS trial the maximum value of 10.36 mg/L was observed on 50th day after crushing. Then, the content decreased to 3.15 mg/L on 130th day after crushing. In oak barrel trial the maximum value of 16,71 mg/L was observed between 50th day after crushing. Then, the content decreased to 3.43 mg/L on 150th day after crushing, that is significantly different from the content of steel tank trial.

The decreasing evolution of hexanoic and octanoic acid content is not significatively negatively correlated with ethyl hexanoate and octanoate concentration (Pearson’s R acid-ester PFMS 0.1038, 0.537; Pearson’s R acid-ester PFMB 0.7001, -0.1455) that indicates us that this disappearance is not due by esters chemical formation as also confirmed by the decreasing in these esters concentration. We suppose that an adsorbing phenomenon of these molecules on grape solids or yeast cells could be involved.

During maceration, the concentrations of the different chemical classes were higher in PFMB and then became similar on day 150 (racking), except for esters, which were present in larger quantities in steel samples.

3.4 Sensory profile

Figure 7 shows the sensory profile of Cabernet Sauvignon wines vinified with post fermentative maceration in steel tanks and oak barrels a day 150 (racking).

Results showed significant differences among wines, especially for the oak barrel post fermentative maceration trial. This trial showed significantly higher values in dried fruits, wild berries, spicy, salty, odour complexity and taste complexity, while it showed significantly lower values in astringent, bitter, acid and herbaceous.

Wines vinified with post-fermentative maceration had a very intense and lively colour, a persistent and complex aroma, attributable to the technique adopted. In particular, the wine vinified in barrel with post-fermentative maceration (PFMB) appeared to be of higher quality than the one vinified in steel tank.

3.5 Conclusions

This study evaluated the effects of post-fermentative maceration of 150 days duration on the winemaking Cabernet Sauvignon grapes introducing a new approach regarding the anthocyanins and non-anthocyanic flavonoids study. In particular, we can easily evaluate and understand the speeds of extraction/decreasing concentration of the mentioned above compounds and also interpolate values of these molecules in different maceration processes compared to them thanks to the nature of continuous functions applied in our approach.

The analytical determination of total polyphenols and flavonoids showed significantly higher values (about more than 20%) in oak barrel post-fermentative maceration trial (PFMB) than that in steel tank post-fermentative maceration trial (PFMS).

The sensory analyses showed that the wines vinified with post-fermentative maceration had a very intense and lively colour, a persistent and complex aroma and taste complexity sensations if compared to wines without post fermentative maceration. In particular, the wine vinified in barrel with post-fermentative maceration (PFMB) appeared to be of higher quality than the one vinified in steel tank. The wine vinified in barrel with post-fermentative maceration (PFMB) showed significantly higher values for colour intensity, odour complexity and taste complexity, as well as for fruity, wild berries, dried fruits and spicy odours, salty and astringent taste, while in steel tank post-fermentative maceration trial (PFMS) showed significantly higher values for herbaceous odour and for acid and bitter taste.

Author's contribution

Paola Bambina: laboratory analysis, statistics and paper writing; Matteo Pollon: mathematical function fitting, statistical elaborations and paper writing; Margherita Squadrito: laboratory analysis; Stefano Barone: supervision of statistics and mathematical functions fitting; Luciano Cinquanta experimental design and supervision of the study; Onofrio Corona experimental design and supervision of the study.

Funding

All the activities were financed by the University of Palermo.

Conflict of interest

The authors declare no conflict of interest with companies, institutions or individuals involved in this study.

Data availability statement

Data obtained in this study are available on request.

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No competing interests reported.

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Effect of prolonged (150 days) post-fermentative maceration in steel tanks and oak barrels on Cabernet Sauvignon wine quality: mathematical modelization of the phenolic compounds behaviour

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Abstract

Figures

1. Introduction

2. Materials And Methods

2.1 Wine making

2.2 Chemical and physical parameters

2.3 Determination of Polyphenols Content

2.4 Determination of Volatile Organic Compounds

2.5 Sensory evaluation

2.6 Statistical analysis

2.7 Proposed approach for the study of total flavonoids, non-anthocyanic flavonoids and anthocyanins

2.7.1 Anthocyanins

2.7.2 Speed of the anthocyanin extraction in stage I

2.7.3 Stage II dynamics

2.7.4 Non-anthocyanic flavonoids

2.7.5 Modelization of NAF

3. Results And Discussion

3.1 Chemical-physical analyses

3.2 Phenolic compounds

3.2.1 Modelized Anthocyanin first stage

3.2.2 Modelized anthocyanin second stage

3.2.3 Modelized non-anthocyanic flavonoids

3.3 Volatile organic compounds

3.4 Sensory profile

3.5 Conclusions

Declarations

References

Additional Declarations

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