Introduction

Chardonnay is one of the oldest and most globally cultivated grape varieties, known for its remarkable adaptability to diverse terroirs across nearly all winegrowing regions. This versatility has resulted in a wide range of Chardonnay styles, each distinguished with unique aroma, flavour, sweetness, bitterness, and acidity profiles (Gambetta et al., 2014). In an increasingly globalized wine market, oak barrel ageing has become a widely adopted technique to enhance wine complexity. Oak and other woods impart both volatile and non-volatile compounds that significantly influence the wine’s organoleptic properties (Liberatore et al., 2010). However, this method has several limitations, as it is time-consuming, expensive, and demands substantial storage space. Moreover, barrels have a limited lifespan due to continuous contact with wine which leads to wood degradation. Microbial contamination is another concern. Spoilage yeasts such as Brettanomyces and Dekkera may develop during barrel ageing, producing ethyl phenols that impart undesirable aromas reminiscent of horse sweat or medicinal notes (Oelofse et al., 2008). Additionally, evaporation losses during ageing—commonly referred to as the “angel’s share”—can lead to significant economic losses (Meusinger et al., 2013). Given these constraints, current research efforts focus on developing alternative ageing strategies that preserve or improve wine quality, while reducing time, cost, and spoilage risks. (Ma et al., 2022).

In this context, High Hydrostatic Pressure (HHP) is a promising and environmentally friendly technology that has been widely applied in the food industry in recent years (Aganovic et al., 2021; Chiozzi et al., 2022; Huang et al., 2017), due to its low energy consumption and minimal contamination impact (Tsevdou et al., 2019). HHP is a non-thermal processing technology which applies isostatic high pressure (100–600 MPa) transmitted through a liquid medium (typically water), to liquid or solid foods, usually at temperatures below 30 °C for durations ranging from a few seconds to over 20 minutes (Huang et al., 2017). In oenology, high hydrostatic pressure (HHP) has been investigated for various applications, such as enhancing the extraction of phenolic compounds from grapes, inactivating undesirable microorganisms and improving wine preservation. HHP has also been employed to modify the physicochemical and sensory properties of wine (Buzrul, 2012; Morata et al., 2017; Nunes et al., 2017; Van Wyk & Silva, 2019). Notably, HHP can induce reactions such as the synthesis, decomposition, and oxidation of phenolic compounds, as well as Maillard reactions similar to those occurring during traditional wine ageing, but at a faster rate and lower cost (Ma et al., 2022; Santos et al., 2012; Santos et al., 2013a; Santos et al., 2013b; Santos et al., 2015; Santos et al., 2016; Solar et al., 2021). These transformations are driven by the physical energy supplied during HHP treatment, which is converted into activation energy that accelerates the ageing process (Liu et al., 2018). Moreover, HHP is considered an emerging technology for improving solid-liquid extraction processes (Ninčević Grassino et al., 2020; Scepankova et al., 2018).

The use of oak chips is a well-established practice in winemaking, commonly employed during the ageing process to impart distinctive sensory characteristics to wine (Gómez-Plaza & Bautista-Ortín, 2019; Petrozziello et al., 2020). Numerous studies have shown that chips made from different wood species (Jordão & Cosme, 2022; Sánchez-Gómez et al., 2016) and crushed and toasted vine-shoots obtained post-pruning can be used as a novel oenological practice (Cebrián-Tarancón et al., 2018a; Cebrián-Tarancón et al., 2019a; Cebrián-Tarancón et al., 2019b; Cebrián-Tarancón et al., 2022a; Cebrián-Tarancón et al., 2022b; Fanzone et al., 2021; Noviello et al., 2024). Aligned with the current trend of recycling oenological waste and by-products (Troilo et al., 2021), reusing vine-shoots obtained after pruning represents an innovative alternative with both environmental and economic benefits for wineries. In fact, vine-shoot chips have an interesting phenolic and volatile profile comparable to that of oak chips, particularly after the toasting process (Cebrián-Tarancón et al., 2018a; Cebrián-Tarancón et al., 2018b; Delgado de La Torre et al., 2012; Delgado de La Torre et al., 2015; Sánchez-Gómez et al., 2016). The effect of vine-shoot chip treatments on the volatile and sensorial composition of wines, considered safe for humans (Cebrián-Tarancón et al., 2021), depends on several factors such as wine type (white or red), chip format and dose (6, 12, 24 g L^–1), timing of the addition during the winemaking process (before, during, or after alcoholic fermentation) and duration of contact (Cebrián-Tarancón et al., 2019a; Cebrián-Tarancón et al., 2019b; Cebrián-Tarancón et al., 2022a).

In this context, several studies have explored the use of HHP to improve the release of oak-derived compounds from oak chips. Tao et al. (2016) reported that HHP enhanced the extraction of phenolic compounds from oak chips into young Merlot and Sangiovese red wines, and Valdés et al. (2021) demonstrated that the addition of holm oak (Quercus ilex L.) chips (5 g L^–1) to cv. Cayetana white wines treated with HHP (400 MPa, 5 and 30 minutes) modified the sensorial characteristics. However, while this ageing effect was observed in Cayetana white wine, only minimal effects were detected in the Tempranillo variety, suggesting the effect may depend on wine type.

Wine aroma is one of the most critical factors influencing perceived quality and consumer acceptance (Bakker & Clarke, 2011; Martínez-Pinilla et al., 2013). Volatile organic compounds (VOCs) play a fundamental role in defining the aroma and flavour profile of wines. In Chardonnay wines, the balance and concentration of these volatile compounds are key determinants of freshness and the overall aromatic character. However, the effects of HHP and vine-shoot chip treatments on the aromatic profile of Chardonnay wines remains scarcely researched, and, to the best of our knowledge, have never been studied in combination. The aim of this work was thus to investigate the effect of HHP and vine-shoot applications, both individually and in combination, on the volatile composition and aromatic characteristics of cv. Chardonnay A.O.C. Ribera del Guadiana (semiarid region of southwest Spain).

Materials and methods

1. Vine-shoot chips preparation

Vine shoots cv. Chardonnay were pruned randomly from a vineyard located in A.O.C. Ribera del Guadiana (Extremadura, southwest Spain) in January 2022, four months after grape harvest. A total of 5 kg of vine shoots was collected and dried in a forced-air oven (Memmert, Schwabach, Germany) at 40 °C for 24 hours. The shoots were then stored in the dark at ambient room temperature (18 ± 3 °C) for four months, following the method of Cebrián-Tarancón et al. (2017) with some modifications. After this period, the shoots were cut into 3–4 cm pieces, ground using a hammer miller (Ventura Forestry Machines, Aiguaviva, Girona, Spain) to a particle size of 2–20 mm, similar to that of commonly used oak chips, and toasted at 180 °C for 45 minutes in a muffle furnace (Hobersal Furnaces & Ovens Technology, Caldes de Montbui, Barcelona, Spain) according to the procedure described by Cebrián-Tarancón et al. (2018b).

2. Samples

Monovarietal white cv. Chardonnay wine (W) from the 2021 vintage was supplied by Romale winery (Almendralejo, Badajoz, Spain) located in A.O.C. Ribera del Guadiana. The study was conducted at the experimental plant, and the samples analysed in the laboratories, both part of CICYTEX-INTAEX (Agri-Food Technology Institute, Extremadura Centre for Scientific and Technological Research). The oenological characteristics of cv. Chardonnay were: 13.2 alcohol degree (% v/v), 21.9 g L^–1 dry extract, pH 3.6, total acidity 5.0 g L^–1 (tartaric acid,) volatile acidity 0.4 g L^–1 (acetic acid), and 28.7 and 158 mg L^–1 of free and total SO₂ respectively. These values are consistent for the monovarietal wines produced in this region.

3. Experimental design

The Chardonnay wine was distributed in 40 L portions into plastic bags (Mod. COEX3soldas 350 × 550 cm; Plasacar S.L., Sevilla, Spain). The bags were vacuum-packed and placed in a semi-industrial hydrostatic pressure unit with 55 L of capacity (Hiperbaric Wave 6000/55; Burgos, Spain) then subjected to a 600 MPa HHP treatment for 30 minutes. The initial water temperature inside the vessel was 10 °C.

The following treatments were carried out (Figure 1):

• W: wine untreated and considered as control;
• WCM: wine (W) with 35 days of contact (M) with 12 g L^–1 vine-shoot chips (C) in tanks;
• WP: wine (W) treated with HHP (P);
• WPC: wine (W) with 12 g L^–1 of vine-shoot chips (C) treated with HHP (P), and removal of chips after the HHP treatment;
• WPCM: wine (W) with 12 g L^–1 of vine-shoot chips (C), treated with HHP (P) and 35 days of contact with vine-shoot chips in tank (M).

Following the treatments, all wine samples were bottled in 350 mL dark glass bottles and stored in darkness at 20 °C for 35 days then analysed. All the experiments were carried out in triplicate. Table S1 shows the chemical composition of samples following this period.

4. Volatile compounds: extraction, identification, and quantification

4.1. Extraction of volatile compounds

HS-SPME-GC-ToFMS was used to analyse the volatile profile of the different experimental wines. Volatile compounds were extracted via SPME using a 50/30 μm, 1 cm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre supplied by Supelco (Bellefonte, PA, USA). 5 mL samples of wine and 0.6 g of sodium chloride were placed into 20 mL glass vials fitted with silicon septums (Honeywell Fluka, Germany). The vials were equilibrated at 40 °C for 5 minutes, after which the SPME fibre was exposed to the vial headspace for volatile extraction for 30 minutes at the same temperature. Following extraction, the fibre was inserted into the GC-ToFMS injection port and desorbed at 260 °C for 3 minutes in split mode, with a split ratio of 50:1. Sample preparation was performed using a CTC Analysis autosampler PAL-System (SepSolve Analytical, Zwingen, Switzerland). Fibre blanks were run periodically to ensure the absence of contaminants or carryover. All wines were analysed in triplicate.

4.2. Identification and quantification of volatile compounds

GC-ToFMS analysis was carried out using an Agilent 8890 GC System (Agilent Technologies, UK) coupled to a Bench TOF-Select detector (Markes International, China). Data acquisition and analysis were performed using TOF-DS 4.1 software (Markes International). Chromatographic separation was performed on a Zebron ZB-WAX capillary column (60 m × 0.25 mm I.D. and 0.25 μm df; Phenomenex, Torrance, CA, USA). The oven temperature program started at 40 °C for 5 minutes, increased by 4 °C per minute to 240 °C, and then held for 5 minutes. Helium was used as the carrier gas. The MS transfer line and source temperatures were set at 250 °C. To determine the retention times and characteristic mass fragments of the analytes, mass spectra were recorded at 70 eV electron ionization (EI) on full scan mode over a range of 30 to 400 Da. Linear retention index values were calculated using a commercial hydrocarbon mixture (C₇–C₃₀) (Sigma-Aldrich, Shanghai, China), analysed under identical chromatographic conditions. The volatile compounds were tentatively identified by matching their mass spectra with reference spectra from the NIST mass spectral library (NIST MS Search Program version 2020), taking into account molecular structure and weight, and by comparing linear retention indices (LRI) with those reported in the literature (Bianchi et al., 2007; Oliveira et al., 2008; Mateus et al., 2010; Di Mattia et al., 2015; Santos et al., 2020; Pereira et al., 2021). The relative abundance of each compound was calculated as a percentage of its respective peak area relative to the total chromatographic peak area (% A).

For samples subjected to HHP treatments and samples stored in thanks, three independent replicates were collected for each treatment. All analyses were performed in triplicate.

5. Sensorial analysis

Sensory evaluation of the Chardonnay wines was conducted by the Vincalab-certified sensory panel of the A.O.C. Ribera del Guadiana, accredited under the UNE-EN ISO/IEC 17025 standard. The panel consisted of eight professional tasters, each with over five years of experience and subject to regular training to ensure consistent performance and calibration. The analysis was carried out in a dedicated sensory evaluation room equipped with individual booths, under controlled environmental conditions (20–22 °C) to minimize external interferences.

All procedures adhered to the ISO 3591:1977 standard for wine tasting, ensuring methodological rigor. Olfactory and gustatory descriptors were not generated ad hoc during the sessions but were selected from a validated, standardised list used in professional white wine sensory analysis. The descriptors included fruity notes such as citrus (lemon, orange, lime), yellow fruits (peach, apricot), white fruits (apple, pear), and exotic fruits (pineapple, mango). The panel also evaluated the presence or absence of secondary and tertiary aromas and flavours, including woody, smoky, tobacco, yeast, balsamic (eucalyptus, menthol), grassy (fresh-cut grass), and oxidative notes (bruised apple, sherry). In addition, the panellists rated overall aromatic intensity (low, medium, high) and persistence (duration of aroma perception post-tasting). To ensure reproducibility and minimise variability, each wine sample was assessed in duplicate by each panellist, and the results were averaged for final analysis.

6. Statistical analysis

The data were analysed using one-way ANOVA to assess the significance of treatments and two-way ANOVA to evaluate the effects of HHP (P), chips (C), and maceration (M), and as well as the combinations (P × C and P × M). Significance levels were set at p ≤ 0.001, p ≤ 0.01, and p ≤ 0.05 and Tukey’s test was applied as a post hoc test for parametric samples. Partial least squares regression (PLSR) was applied to show the relationship between chemical variables (X data) and sensory descriptors (Y data) of the wines. This is a data reduction technique that transforms the X variables into a set of uncorrelated factors that describe the variation in the dataset. Calculations were performed using XLStat-Pro (Addinsoft, Paris, 2009). Finally, clustering analysis coupled with a polar heatmap was used to analyse the volatile composition (considering compounds with area ≥ 0.1 %). OriginPro 2020 (OriginLab Corporation, Northampton, MA, USA) was used for this statistical analysis.

Results

1. Volatile organic compounds (VOCs) identified in cv. Chardonnay: effect of treatments

As shown in Table 1, the analysed samples contained comparable quantities of volatile organic compounds (VOCs): 141 in W, WCM, and WPCM, 134 in WP, and 143 in WPC. For all samples, the relative abundance of each compound was calculated as the percentage ratio (PRA) of its peak area in relation to the total peak area of the chromatogram. The identified compounds accounted for 100 % of the total chromatographic peak area.

In wines not subjected to High Hydrostatic Pressure (HHP), specifically W and WCM, the most abundant volatile compounds were primarily esters and acetates. Among these, octanoic acid, ethyl ester (E19) exhibited the highest Perceived Relative Aroma (PRA) values: 29.75 in W and 43.88 in WCM. Other relevant esters included hexanoic acid, ethyl ester (E11) and decanoic acid, ethyl ester (E26), while the major acetates were ethyl acetate (AC2), 1-butanol-3-methyl acetate (AC6), and acetic acid, hexyl ester (AC10). Dodecanoic acid, ethyl ester (E38) showed a significantly lower PRA value in WCM compared to W (p < 0.05). Several compounds were exclusively detected in W, including acetic acid, octyl ester (AC13), dodecanoic acid, methyl ester (E36), 3-methylbutyl dodecanoate, and hexanoic acid, 2-phenylethyl ester (E44 and E45).

In contrast, wines treated with HHP (WP, WPC, and WPCM) were dominated by alcohols and acetates, particularly 1-butanol, 3-methyl (AL4) and 1-butanol-3-methyl acetate/isoamyl acetate (AC6), which showed the highest PRA values, with values approaching 20. Ethyl acetate (AC2) also showed elevated levels, exceeding 5 %, and was significantly more abundant in treated wines than in untreated ones (p < 0.05). Conversely, esters such as octanoic acid, ethyl ester (E19), decanoic acid, ethyl ester (E26), and dodecanoic acid, ethyl ester (E38) were significantly less abundant in HHP-treated wines compared to W (p < 0.05), with E38 showing PRA values consistently below 1 across all treated samples.

Certain compounds were generated exclusively in treated samples, while others were only detected in the untreated samples. Specifically, 1-octen-3-ol (AL11), aldehydes (AD2, AD4, AD5, AD10, AD11, and AD14), ketones (K3, K6, K9, and K11), and trans-caryophyllene (T3) were present in WPMC but were not detected in the control sample W.

Figure 2 shows a polar heatmap with a circular dendrogram generated from hierarchical cluster analysis. This clustering approach groups wines and volatile compounds based on similarities in their profiles. The samples were clustered into two distinct groups (red and blue) based on their volatile compositions while the volatile compounds were clustered into five distinct groups (red, blue, green, violet, and brown). Wines treated with HHP (WP, WPC, WPCM) exhibit a volatile profile different from that of W and WCM. The first cluster (red), associated with HHP-treated wines, contains 38 VOCs, primarily alcohols, esters, and acetates (12, 7 and 6 VOCs respectively). The second and third clusters contain predominantly terpenes, norisoprenoids, and fatty acids. The fourth cluster (violet) consists of 11 VOCs, mainly ethyl esters, which are most abundant in W and WC wines. The fifth cluster (brown) comprises 5 VOCs, predominantly ethyl esters and aldehydes, which are characteristic of WCM wines. The polar heatmap demonstrates that the different treatments significantly alter the volatile compound profile. The wines treated with HHP exhibit a distinct profile, with higher concentrations of certain compounds such as furfural. The clustering of compounds suggests well-defined patterns in VOC distribution according to the applied treatment.

2. Effect of treatments on family compounds

The VOCs detected in W, WP, WPC, WPCM, and WCM were grouped into the following chemical classes: acetates (14, 12, 13, 12, and 13 compounds, respectively), alcohols (21, 21, 21, 22, and 20), aldehydes (9, 11, 14, 15, and 14), aromatic hydrocarbons (2 compounds in all treatments), esters (51, 44, 46, 44, and 48), fatty acids (9, 9, 8, 9, and 8), furans (5, 3, 4, 3, and 5), ketones (9, 10, 11, 12, and 9), norisoprenoids (4 in all samples), and terpenes (4, 5, 5, 4, and 5, respectively).

Figure 3 presents the PRA values of VOCs and the effects of treatments on the chemical classes detected in the Chardonnay samples. In W and WCM, esters, alcohols, and acetates exhibited the highest PRA values, in that order, whereas norisoprenoids and aromatic hydrocarbons showed the lowest values (< 0.1 in all cases). In WP, WPC, and WPCM, the most abundant classes were alcohols > esters > acetates.

Compared to W, HHP treatment had a significant impact on the aromatic profile, resulting in WP, WPC, and WPCM showing: (i) a considerable and significant decrease in ester PRA values; (ii) an increase in alcohol and acetate PRA values; and (iii) an increasing trend in the remaining VOC families, except for norisoprenoids and aromatic hydrocarbons. In contrast, the WCM treatment (35 days of contact with vine-shoot chips in a tank) had a minimal effect on the aromatic profile, with PRA values in W and WCM samples remaining similar, although an increase in terpene PRA values was observed.

The two-way ANOVA indicated the effect of HHP (P), was stronger than vine-shoot chips (C) and maceration (M). In fact, P significatively modified the PRA values of seven chemical classes, whereas C and M affected only 2 and 3, respectively. Interactions P × C and P × M were only significant for aldehydes and terpenes. The effects also appear class-dependent: PRA of aldehydes was significatively influenced by P, C, and M, whereas norisoprenoid PRA values remained unaffected.

3. Discrimination of samples

Principal component analysis (PCA) was performed to investigate potential differentiation among treatments based on aromatic profile. The PCAs included only VOC classes showing significant results. Figure 4 shows that the first two principal components, F1 and F2, accounted for 90.71 % of the total variance (76.12 % and 14.59 %, respectively). F1 was positively associated with acetates, ketones, fatty acids, alcohols, and furans, and negatively associated with esters. F2 was characterized by positive loadings for norisoprenoids and negative loadings for aldehydes.

Figure 4 also shows clear discrimination based on HHP treatment. The PCA shows three clear groups: the first, on the negative side of F1, comprised the control wine (W) and the wines subjected to classical maceration treatment (WCM). The WP, WPC, and WPCM wines were positioned on the positive side of F1. In this group, two subgroups can be distinguished: i) WP, and ii) WPC and WPCM. Based on the PCA, the results affirm that HHP process, with or without vine-shoots, modified the aromatic profile. Specifically, W and WCM wines were mainly characterised by high PRA values of esters, whereas WPC and WPCM wines showed a predominance of acetates and ketones. This result was particularly interesting and highlights the potential of HHP to direct outcomes.

4. Sensorial analysis

The colour of all the cv. Chardonnay wines was assessed as pale golden with medium intensity. The values in Figure 5 represent the percentage of judges (% J) who perceived each descriptor in the respective wine sample, with higher values indicating a greater proportion of the panel detected a given characteristic. Yellow fruits, white fruits, and exotic fruits were frequently identified across all samples. The W sample exhibited the highest detection of white fruits, with 63 % of judges detecting this descriptor, whereas the other samples showed lower frequencies. The yeast descriptor was detected by a moderate percentage of judges (13–25 %), indicating a consistent but not dominant perception of fermentation aroma. Wood aroma was detected at varying levels, with WPCM (75 %) showing the highest % J, confirming a stronger influence of vine-shoot chips in these samples.

Balsamic aromas were less frequently perceived (≤ 25 % J), suggesting these characteristics are not dominant in these wines. Grass aroma was observed only in WCM (38 %) and WPCM (25 %), suggesting a more pronounced vegetal expression in these samples. Oxidation aromas were detected by a small percentage of judges, with slightly higher values in WP (25 % J) and WPCM (13 %), indicating a potential for greater wine evolution. With respect to the gustatory profile, acidity was identified by a low proportion of judges across all samples, with the highest detection in WP (25 % J). Bitterness was reported in WP (50 %), WCM (38 %), and WPCM (38 %), possibly linked to vine shoot influence in the latter two. Astringency was noted only in WCM (13 %), suggesting a mild perception of tannins.

Samples with higher wood influence (WPC and WPCM) showed the highest perception of wood notes, accompanied by a lower percentage of judges detecting fresh fruit aromas. Sample W was most frequently described as fruity, particularly with white and yellow fruit characteristics, while WP exhibited the highest perception of bitterness and oxidation, consistent with more advanced wine evolution. WCM and WPCM displayed a balanced profile of fruit, herbal, and wood descriptors, but also showed higher frequencies of bitterness and astringency, possibly due to tannin content. Finally, as shown in Table 2, W exhibited the highest olfactory intensity and persistence. In contrast, WP showed the lowest olfactory intensity, suggesting a less expressive aromatic profile, while WPC exhibited a moderate intensity, possibly influenced by a balance between fruitiness and wood-derived aromas.

5. PLS modelling relationships between sensory descriptors and chemical composition of wines

Partial least squares regression (PLSR) was applied to examine correlations between sensory attributes and chemical compounds in Chardonnay wines subjected to different treatments. Prior to analysis, the data were standardized to ensure comparability across variables. Figure 6 presents the correlation plot based on the first two latent variables, t1 and t2, which are linear combinations of the original variables that capture the maximum covariance between the chemical (X) and sensory (Y) datasets. These components define a two-dimensional latent space in which the relationships among variables can be visualized.

The PLSR model demonstrated strong explanatory and predictive performance, with a cumulative R²Y of 0.800 and Q² of 1.000. The results revealed robust associations between sensory attributes such as colour and taste, and volatile compounds. In the plot, variables are represented as coloured points: blue for chemical compounds (X variables), red for sensory attributes (Y variables), and green for active variables. The correlation circle facilitates interpretation of the direction and strength of each variable’s contribution to the model. This visualization provides valuable insights into how different treatments influence both the chemical composition and sensory perception of Chardonnay wines.

According to Figure 6, esters showed a strong positive contribution to component 1 (t1), corresponding to the control wine (W), which is located in the right quadrant of the PLSR biplot. This wine was characterised by fresh and fruity sensory descriptors, including citrus, white fruits, exotic fruits, yellow fruits, olfactory persistence, and fermentation aromas. Ethyl esters, such as ethyl hexanoate (E11) and ethyl octanoate (E19), are well known for their contribution to fruity and floral aromas. Both compounds were detected in W (Table 1), with ethyl octanoate being the most abundant volatile compound. Their presence explains the strong correlation with the sensory attributes observed in the control wine (W). Furthermore, as shown in Figure 3, the % PRA of esters was highest in W, further reinforcing their role as key contributors to fruitiness and freshness in untreated Chardonnay wines.

In contrast, acetates, alcohols, volatile fatty acids, ketones, and furans exhibited a strong negative contribution to component 1 (t1), suggesting an association with less fresh and more oxidized sensory profiles. These compounds classes are typically linked to oxidative processes and contribute to complex aromatic characteristics. The higher alcohols identified-1-propanol (AL1), 1-propanol, 2-methyl (AL2), 1-butanol (AL3), and 1-butanol, 3-methyl (AL4) (Table 1), are known to impart pungent or fusel-like notes. Fatty acids, such as hexanoic and octanoic acids are frequently associated with cheesy or rancid aromas. Furans and ketones, often formed through thermal degradation or wood contact, contribute to toasty, caramel, or oxidized nuances.

The HHP-treated wine (WP), positioned in the upper-left quadrant of the PLSR biplot, was closely associated with these oxidation-related compounds, particularly acetaldehyde, furans, and volatile fatty acids, which evoke bruised apple, nutty, and oxidized aromas. As shown in Figure 3, WP exhibited the highest % PRA values for acetates, alcohols, aldehydes, furans, and terpenes, consistent with its chemical composition and sensory positioning within the oxidative spectrum. These results further support the perception of oxidative and alcoholic notes in this sample.

WPC and WPMC, located in the lower-left quadrant of the PLSR biplot, were associated with furans and sensory descriptors such as woody, balsamic, and bitterness. Furans—particularly furfural (AD7) which showed the highest % PRA in WPMC (Table 1)—are characteristic of wood ageing and are likely derived from the thermal degradation of lignin in vine-shoot chips. As shown in Figure 3, WPC also exhibited high % PRA values for furans and aldehydes, supporting its association with wood-derived compounds and the corresponding sensory attributes observed in this quadrant. The perception of balsamic notes may also be linked to aromatic hydrocarbons and phenolic aldehydes, which contribute to aromatic complexity.

WCM (maceration with chips for 35 days without HHP treatment) was positioned in the lower-right quadrant of the PLSR biplot. This wine was associated with aldehydes, astringency, olfactory intensity, and grassy sensory notes. Aldehydes such as hexanal (AD5) and nonanal (AD6), which were not detected in the untreated wines but were detected in WCM (Table 1), are known to impart green, grassy, or herbaceous aromas, consistent with the sensory profile of this wine. The pronounced astringency may be due to phenolic extraction during the extended maceration period with vine-shoot chips. As shown in Figure 3, WCM exhibited moderate % PRA values for aldehydes and fatty acids, supporting its association with green, grassy, and astringent characteristics, likely resulting from prolonged contact with vine shoot material.

The PLSR biplot reveals a clear separation between fresh, fruity wines (right side, associated with esters and the control wine) and oxidized or wood-influenced wines (left side, associated with HHP and vine shoot treatments). This suggests that: i) esters are key markers of freshness and fruitiness, especially in W (untreated wines); ii) oxidation-related compounds including aldehydes, volatile fatty acids, ketones, reflect the effect of HHP treatment; iii) furans and aromatic hydrocarbons, likely derived from vine-shoot chips, contribute to woody and balsamic notes; and iv) aldehydes and phenolic compounds may contribute to astringency and green sensory attributes, particularly in wines subjected to extended chip contact (WCM).

Discussion

Our results indicate that vine-shoot maceration, high hydrostatic pressure (HHP), and the combined application of both techniques influenced the aromatic profile of Chardonnay wines in distinct ways, with varying levels of statistical significance. The treatments affected the frequency with which trained panellists detected key sensory attributes, including fruitiness, wood-related aromas, oxidative notes, and mouthfeel properties such as bitterness and astringency.

The volatile profile of untreated Chardonnay wines was dominated by esters, which contribute a wide range of fruity notes, including apple, pear, citrus and tropical fruits, alongside notable levels of alcohols, acetals, aldehydes, ketones, and aromatic hydrocarbons. Only a limited number of monoterpenes were detected, including D-limonene, linalool, α-terpineol, and β-citronellol. The presence of norisoprenoids such as trans-vitispirane, cis-vitispirane, TDN, and damascenone was consistent with previous studies (Simpson & Miller, 1984; Cejudo-Bastante et al., 2013; Gambetta et al., 2014). The high % PRA values for 2-phenylethanol, ethyl hexanoate, and isoamyl alcohol supports the findings of Louw et al. (2010), who reported that most yeast-derived compounds—particularly alcohols, acids, and esters—were unaffected by vintage. This suggests that these compounds may be characteristic of the Chardonnay cultivar. In the untreated wines, esters predominated, positively contributing to fruit-forward aromas, leading panellists to perceive yellow and white fruit aromas typically associated with young Chardonnay wines.

In this study, vine-shoots were toasted to be applied as an oenological practice in a manner analogous to the common application of commercial oak chips. Previous studies have studied the impact of wood contact on Chardonnay wines (Guchu et al., 2006; Herrero et al., 2016). From an aromatic perspective, interaction with wood—particularly oak, the most frequently used species—is typically associated with the presence of furanic and benzenoid compounds, followed by whiskey lactones, and to a lesser extent, terpenes. The concentration and proportion of these compounds in wine depend on the wood’s origin, the level of toasting applied, and, in the case of chips, their shape and size (Guchu et al., 2006). To the best of our knowledge, this study represents the first use of toasted vine-shoots from Vitis vinifera cv. Chardonnay. In this context, the present study builds on the research of Cebrián-Tarancón et al. (2018a), who investigated the use of vine shoots as an innovative oenological practice. These researchers analysed the volatile composition of vine shoots from Airén and Cencibel cultivars toasted at 180 °C for 45 minutes. Their analysis identified furanic compounds, benzenoids, norisoprenoids, terpenes, C₆ alcohols, other volatiles, and trans- and cis-whiskey lactones in toasted Airén vine shoots. In the current study, decanal and nonanal-minimally present in the control-were detected in Chardonnay wines treated with vine-shoot chips (WCM wines). Notably. nonanal had previously been identified in vine-shoot chips from Airén and Tempranillo cultivars by the aforementioned authors.

The results (Table 1; Figures 2–6) indicated that 35 days of maceration in tank with toasted vine-shoot chips from Chardonnay vines had a limited impact on the aromatic profile. The % PRA values for most compounds were similar between W and WCM wines. The main differences were observed in the esters, with decreases in 14 compounds in WCM compared to W, and in aldehydes, where 4 compounds showed increased levels in WCM. When comparing W and WCM, statistically significant differences were detected only in aldehydes.

However, tasters perceived greater astringency in WCM, and PLSR analysis (Figure 6) indicated that longer maceration with vine-shoot chips may increase polyphenol extraction, resulting in wines that are more tannic, structured, and intense, in contrast to the fresh and fruity profile of the control wines. These findings suggest that under these conditions, both contact time and vine-shoot chip concentration require further investigation, as the parameters may not have been optimal for effective transfer of volatile compounds from the vine-shoots to the wine.

Previous studies explored the impact of different high hydrostatic pressure (HHP) conditions on the volatile composition and sensory properties of wines, demonstrating that the treatment parameters—pressure, temperature, and time—significantly influence the outcomes. Briones-Labarca et al. (2017) reported that HHP treatment of Sauvignon blanc wines at 300 MPa reduced microbial load, improved organoleptic properties, and induced imperceptible colour changes. In cv. Marselan wines, Yi et al. (2024) examined HHP treatments ranging from 100 to 600 MPa for 10 to 30 minutes, identifying 300 MPa for 20 minutes as the optimal condition for enhancing the aromatic profile and taste perception. More recently, Cheng et al. (2025) applied a response surface design of experiments (RSDE) on the same variety, determining optimal HHP conditions to be 470 MPa, 26 °C, for 40 minutes. Under the applied parameters, wines exhibited increased complexity, with enhanced fruity, floral, and herbaceous aromas, as well as improved drinkability. These effects were attributed to elevated concentrations of esters (e.g., ethyl acetate, diethyl succinate), as well as the generation of terpenes (e.g., citronellol, myrcene) and higher alcohols (e.g., 2-ethylhexanol, 2-heptanol). In Chardonnay wines subjected to the experimental conditions in this study (600 MPa for 30 minutes), a significant impact on the aromatic profile was observed. HHP significantly affected the relative aromatic proportions (% PRAS) of nearly all volatile compound classes, with the exception of norisoprenoids (Figure 3). Principal component analysis (PCA) and the partial least squares regression (PLSR) clearly distinguished treated from untreated wines regardless of the presence of oak chips during processing. However, contrary to the promising results reported by previous studies, the HHP-treated wines in this study did not show improved sensory characteristics. Specifically, wines subjected to HHP (WP) were associated with oxidative, acidic, and bitter sensory attributes. This suggests that HHP may have accelerated oxidative processes, thereby diminishing fruity and fresh aromatic notes. Oxidation is known to generate aldehydes, ketones, alcohols, acetates, volatile fatty acids, and furans, which contribute to aged or stale aromas and reduce the perception of freshness (del Barrio-Galán et al., 2024). The underlying mechanism likely involves the conversion of applied physical pressure into activation energy, which facilitates chemical reactions characteristic of wine ageing. This energy input can disrupt hydrogen bonds and promote both synthesis and degradation processes (Liu et al., 2018; Tao et al., 2014). Although pressure levels between 100 and 600 MPa are known to affect molecular dynamics—particularly polyphenol polymerisation and the distribution of volatile compounds (Nunes et al., 2017)—the synergistic effects of pressure, temperature, and treatment time remain insufficiently understood in oenological applications. Temperature may also play an important role in modulating these effects, influencing both colour and aromatic stability (Liu et al., 2018). Given the observed trade-off between freshness (esters, fruity notes) and oxidative or wood-derived characteristics, these findings highlight the importance of carefully controlling both HHP treatment and wood exposure during Chardonnay winemaking. Furthermore, they highlight the need for a variety-specific approach to HHP application and for further studies focused at optimising treatment conditions tailored to different wine matrices.

Finally, the combined application of high hydrostatic pressure (HHP) and wood-derived products has been extensively studied due to its potential to accelerate wine ageing processes. In the present study, wines treated with vine-shoot chips and HHP (WPC and WPCM) exhibited significant increases in acetates, alcohols, aldehydes, fatty acids, furans, and ketones compared with the control (Figure 3). These increases were associated with sensory attributes typically found in aged wines, such as woody and balsamic notes. The correlation between woody and balsamic sensory descriptors, particularly in WPCM samples (Figures 5 and 6) suggests that the combination of HHP, vine-shoot chips, and short maceration enhances complexity and structure, without inducing the undesirable oxidative, bitter, and astringent notes observed in WP wines. The theoretical foundation of this approach lies in the synergistic interaction between HHP and wood components. Firstly, HHP can replicate certain aspects of the micro-oxygenation that occurs during traditional barrel ageing. Secondly, wood products provide key aromatic and structural compounds. Thirdly, HHP promotes the extraction (leaching) of these compounds, thereby shortening the ageing period and facilitating the incorporation of wood-derived constituents into the wine.

The results obtained in this study are of particular interest. Although not statistically significant P × M interactions were detected in the PRA of volatile compounds, sensory analysis indicated that the most effective strategy involves enhancing the extraction of wood-derived compounds through HHP, followed by a 35-day maceration. The process required only 35 days to produce notable sensory characteristics in the wines. Valdés et al. (2021) reported similar findings when they applied HHP in combination with holm oak (Quercus ilex) to white (cv. Cayetana) and red (cv. Tempranillo) wines. They observed that HHP increased polyphenol content, altered chromatic properties in white wine, and raised oxidation susceptibility, resulting in reduced fresh and fruity aromas and a rise in oxidation-associated compounds. However, the effects of accelerated ageing were more evident in the white wine, whereas only minor sensory changes were detected in the red wine. These results highlight the importance of optimizing HHP processing conditions (pressure and holding time) according to grape variety and wood chip concentrations. Further studies are therefore necessary, as modulating HHP parameters or adjusting the dose of vine-shoot chips may eliminate the need for subsequent maceration.

Conclusion

This study demonstrates that both vine-shoot chip maceration and HHP treatment can influence the aromatic and sensory profiles of Chardonnay wines to varying degrees. Untreated wines exhibited the fruity, fresh character typical of young Chardonnay, while HHP-treated wines (WP) showed increased levels of oxidation-related compounds and associated sensory attributes, such as bitterness and acidity, suggesting that the applied conditions may have accelerated undesirable oxidative reactions. Vine-shoot chips represent a novel oenological practice for imparting distinctive sensory attributes to wine. However, maceration with vine-shoot chips alone (WCM) had a limited effect on the volatile composition, although it enhanced astringency and structure, possibly due to polyphenol extraction. The combined application of vine-shoot chips and HHP (WPCM) promoted the development of aged, woody, and balsamic notes, increasing complexity and improving structural balance, without the oxidative drawbacks observed in HHP-only treatments.

These findings highlight the potential of combining HHP with alternative wood sources such as vine shoots to influence wine style and accelerate the ageing process. However, the variability observed across treatments indicates the need to optimise processing parameters, particularly pressure, maceration time, and wood chip composition, for each grape variety to achieve the desired oenological outcomes. Further research is required to refine these interventions and consistently enhance wine quality.

Acknowledgements

This work has been funded by the project: Valorization of natural plant-based resources. Development and digitalisation of processes to improve the sustainability and competitiveness of the productive sector in Extremadura (VAVEGEX), within the framework of the FEDER Operational Programme Extremadura 2021–2027. Action 1A1103. Development of scientific research, technological development, and innovation capacity, co-financed at 85 %. Authors also give thanks to MED—Mediterranean Institute for Agriculture, Environment and Development (DOI 10.54499/UIDB/05183/2020); CHANGE—Global Change and Sustainability Institute (DOI 10.54499/LA/P/0121/2020).