Effects of high hydrostatic pressure on aging acceleration and quality improvement of kiwifruit wine

Abstract

High hydrostatic pressure (HHP) shows promise as a method for shortening the aging period and enhancing the quality of kiwifruit (Actinidia spp.) wine. In this study, we aimed to evaluate the effects of HHP treatment (300, 400, 500, and 600 MPa) on the physicochemical properties, color, total phenolics and flavonoids, monomeric phenols, antioxidant activity, volatile compounds, and sensory attributes of kiwifruit wine. We found that HHP treatment substantially altered the physicochemical properties, promoted ester formation, and increased the variety of volatile compounds. The total volatile compound content substantially increased above 300 MPa, and the 400 MPa treatment yielded the greatest abundance of monomeric phenols. Wine treated at 400 MPa exhibited superior clarity, aroma intensity, and taste balance, while preserving the characteristic flavor of kiwifruit. This study provides a theoretical basis for accelerated aging and quality enhancement of kiwifruit wine.

Highlights

• •Investigated effects of high hydrostatic pressure on kiwifruit wine properties.
• •Wine retained phenols and antioxidant capacity after high pressure treatment.
• •Treatment promoted ester formation and increased variety of volatiles in wine.
• •High pressure treatment promoted aging and improved sensory quality of wine.
• •Kiwifruit wine treated at 400 MPa had superior clarity, aroma, and taste balance.

1. Introduction

Kiwifruit (Actinidia spp.) belongs to the Actinidiaceae family and is native to the Yangtze River region of China (Waswa et al., 2024). It contains more than 20 essential nutrients and abundant vitamins, particularly vitamin C (Han et al., 2023). Additionally, kiwifruit is rich in phytochemicals with antioxidant properties that combat free radicals, offering antiproliferative, anti-inflammatory, antimicrobial, antihypertensive, and antihypercholesterolemic benefits (Suriyaprom et al., 2022; Wang et al., 2021). Kiwifruit is a climacteric fruit; during ripening, its flesh softens and decays rapidly, leading to quality deterioration (Chai et al., 2024). During transport and storage, moisture loss can cause fruit shrinkage, metabolic alterations, and weight reduction, adversely affecting quality (Gwanpua et al., 2022). Although low-temperature storage and transportation can extend the shelf life, cold injury often develops during prolonged refrigeration (Niu et al., 2024), resulting in a phenomenon of “abundant harvest, poor income.” As a form of deep processing, making fruit wine not only diversifies kiwifruit's flavor profile but also enhances its bioactivity, yielding a unique, aromatic, and nutrient-rich beverage (Huang et al., 2022). However, current kiwifruit wines have long aging periods and exhibit pronounced sourness and astringency, bland aromas, and an unbalanced mouthfeel, which hinder high-quality industry development (Moysidou et al., 2024).

Post-fermentation aging involves slow oxidation and esterification, which rebalance the alcohols, esters, and acids; enrich the aroma; improve the flavor; and enhance the mouthfeel of kiwifruit wine (Stanzer et al., 2023).Studies on rapid aging techniques and their impact on flavor—a key quality determinant derived from aldehydes, esters, alcohols, and terpenes—remain scarce (Huang et al., 2021). Kiwifruit wine's aroma evolves through three stages: inherent fruit volatiles, fermentation-derived compounds, and aging-related transformations (Ascrizzi et al., 2022). In industrial production, prolonged maturation cycles and a dominant alcoholic taste impede commercialization (Huang et al., 2022). Common acceleration methods, such as fixed yeast strain usage, staged organic nitrogen addition, and ultrasonic treatment, are complex and costly, making them unsuitable for large-scale production (Zhang et al., 2023). Traditional fruit wine aging is time-consuming and costly. In recent years, several non-thermal technologies, including high hydrostatic pressure (HHP), pulsed electric field (PEF), and high-power ultrasound (US), have been applied to fruit wine aging. Among these methods, HHP offers distinct advantages. HHP is a nonthermal sterilization technology wherein liquid is pumped at pressures exceeding 300 MPa and then instantaneously depressurized (Morata & Guamis, 2020). As HHP can inactivate microorganisms and affect yeast viability, its benefits and drawbacks for brewing yeast require further investigation (Zhang et al., 2024). In wine applications, HHP has been shown to improve quality. For example, grape juice treated with HHP remained microbiologically stable at 4 °C for over 8 mo; retained its antioxidant activity, color, and phenolic content at levels comparable to those of SO₂-treated controls; exhibited complete polyphenol oxidase inactivation; and displayed enhanced sensory attributes (Loira et al., 2018; Puig-Pujol et al., 2023; Sun et al., 2015). HHP treatment has been shown to promote phenolic polymerization in red wine, with the degree of tannin polymerization and pyranoanthocyanin content approaching those achieved through traditional barrel aging (Santos et al., 2019). Treatment at 300 MPa for 20 min can also significantly increase total phenolic content and ester compounds that contribute to aroma (Yi et al., 2024). Compared with PEF and US technologies, HHP is more effective in preserving sensitive aroma compounds, minimizing oxidative loss, and preventing thermal damage. It is therefore particularly suitable for aging fruit wines with complex aroma profiles. In contrast, traditional kiwifruit wine requires 1–2 years of natural aging to achieve aroma balance and palate harmony, a process associated with long cycles, high costs, and variable quality. HHP technology offers distinct advantages over conventional aging, including short processing time, absence of thermal damage, controllable quality, and improved economic efficiency. By modifying phenolic structures and promoting the release of aromatic compounds, HHP can replicate the effects of long-term aging within a short period (Morata et al., 2017), providing a promising technological pathway for the industrial production of fruit wines.

To date, no studies have reported the effects of HHP on kiwifruit wine maturation, aging, or bioactive compound profiles. Therefore, in this study, we applied HHP to kiwifruit wine with the aim of comparing the physicochemical properties, color, phenolic content, in vitro antioxidant activity, volatile composition, and sensory qualities under various pressure conditions. Our results elucidate the potential of HHP as an accelerated aging technique and provide a theoretical basis for wine quality enhancement.

2. Materials and methods

2.1. Kiwifruit wine production

The kiwifruit (Actinidia deliciosa cv. Xuxiang) used in this study was sourced from the National-level Kiwifruit Industrial Park in Meixian County (33°59′00″–34°19′28″ N, 107°39′08″–108°00′51″ E). The fruit was manually harvested on November 23, 2023, ensuring that the kiwifruits were intact, free from pests, and without physical defects. After harvesting, the kiwifruits were allowed to ripen under warm ambient conditions (approximately 20–25 °C) before being set aside for further use. The wine yeast, Angel Yeast VIC, was purchased from Angel Yeast (Yichang, Hubei, China). We prepared the kiwifruit wine according to the production procedures described by Huang et al. (2021) and Liu, Qi, et al. (2020).

We began the preparation process by crushing and pulping the pre-treated kiwifruit, adding 50 mg/L of SO₂ to preserve the color. A pulping machine was used to automatically separate the juice from the pulp and skins, and the juice was then filtered through nylon gauze multiple times to obtain pure kiwifruit juice for later use. The soluble solids content (SSC) of the juice was measured using a refractometer, and white sugar was added to adjust the SSC to 20°Brix. The adjusted juice was divided into four 2 L portions and transferred into 2.5 L glass fermentation tanks. Next, 0.4 g of Angel Yeast VIC was weighed, slowly added to conical flasks containing 10 % sugar water at 35–40 °C, and activated through incubation at 37 °C for 15–20 min. The activated yeast was then added to each tank of kiwifruit juice and mixed thoroughly, ensuring that the temperature difference between the yeast solution and juice remained below 10 °C. Finally, the fermentation tanks were sealed with perforated plastic wrap and covered with eight layers of sterile gauze. The tanks were placed in a low-temperature incubator at 20 °C for fermentation. Every 24 h, samples were taken to measure the SSC. Fermentation was considered complete when the SSC reached a stable level. At this stage, the kiwifruit wine was centrifuged using a high-speed refrigerated centrifuge (Xiangyi Centrifuge Co., Ltd., China), transferred to a clean container, and stored at 4 °C.

2.2. Sample preparation

The kiwifruit wine samples (150 mL) were placed into pressure-resistant plastic bottles, which were sealed, and then processed using an SSH-8.8 L HHP device (Shanxi Lidefu Technology Co., Ltd.). Water was used as the medium, and the samples were treated at pressures of 300, 400, 500, and 600 MPa for 20 min at a processing temperature of 20 °C (Tian et al., 2016; Yi et al., 2024). Various indicators were measured immediately after treatment, with untreated fruit wine used as a control.

2.3. Basic physicochemical indicator determination

2.3.1. Transmittance, soluble solids content, pH, total sugars, and titratable acidity

According to the method described by Liu, Wang, et al. (2020), using distilled water as the reference (T = 100 %), the transmittance of wine samples was measured using a UV1780 UV–visible spectrophotometer (Shimadzu Corporation, Japan). A 3.00 mL sample was placed in a transparent cuvette, and the transmittance (%) was measured at a wavelength of 680 nm in the UV–visible range.

The SSC was measured using a digital refractometer, and the pH was measured using a PHS-3C pH meter (Shanghai Precision Scientific Instrument Co., Ltd., China). Total sugar content was determined using the phenol–sulfuric acid method, following the procedure outlined by Yue et al. (2022). Titratable acidity was measured following the method described by Seong et al. (2016) and calculated using the following formula:

$$\mathrm{X}=\mathrm{C}\times \left({\mathrm{V}}_1–{\mathrm{V}}_0\right)/{\mathrm{V}}_2\times 75$$ (1)

where X is the acid content in the fermentation liquid (g/L), C is the concentration of the sodium hydroxide standard solution (mol/L), V₀ is the volume of NaOH consumed during titration of the blank test (mL), V₁ is the volume of NaOH consumed during titration of the sample (mL), V₂ is the volume of the sample (mL), and 75 is the molar mass of tartaric acid (g/mol).

2.3.2. Alcohol content

The supernatant (50 mL) and distilled water (50 mL) were added to a distillation flask. We collected 50 mL of distillate in a volumetric flask, and the alcohol content was measured directly using a DMA 35 portable density meter (Anton Paar GmbH, Austria).

2.4. Color measurement

Color was measured according to the method described by Liu et al. (2025). At room temperature, the instrument was zeroed using a blackboard and calibrated using a standard whiteboard as a reference. The processed sample (3 mL) was placed in a 4 × 4 × 1 cm transparent quartz cuvette and detected in front of a CM-5 colorimeter lens (Konica Minolta, Inc., Japan) to obtain the L* (lightness), a* (red/green), and b* (yellow/blue) values. The total color difference (ΔE) was calculated as follows:

$$△E={\left[{\left(L^{\ast }–{L_{\mathit{0}}}^{\ast }\right)}^2+{\left(a^{\ast }–{a_{\mathit{0}}}^{\ast }\right)}^2+{\left(b^{\ast }–{b_{\mathit{0}}}^{\ast }\right)}^2\right]}^{1/2}$$ (2)

where L* is the lightness value of the sample after fermentation with different yeasts; L₀* is the lightness value of the sample before fermentation; a* is the red/green value of the sample after fermentation; a₀* is the red/green value of the sample before fermentation; b* is the yellow/blue value of the sample after fermentation; and b₀* is the yellow/blue value of the sample before fermentation.

2.5. Total phenolic and flavonoid content determination

2.5.1. Total phenolic content

Using gallic acid as the standard, we determined the total phenolic content according to the method described by Li et al. (2018), with slight modifications. A 0.5 mL aliquot of wine sample, diluted 10–16 times, was added to 2.5 mL of Folin–Ciocalteu reagent, which had been diluted 10 times. After reacting for 3 min, 3.0 mL of a 20 % Na₂CO₃ solution was added to the mixture. The mixture was incubated in the dark at room temperature for 1 h, after which the absorbance was measured at 765 nm. The total phenolic content of the samples was calculated by substituting the absorbance into the standard curve. The regression equation for the standard curve was y = 0.0075× + 0.0129 (R² = 0.999).

2.5.2. Total flavonoid content

Using rutin as a standard, we used the method for determining the total flavonoid content outlined by Kwaw et al. (2018), with slight modifications. A 4 mL aliquot of the sample, diluted five times, was taken and mixed with 0.5 mL NaNO₂ solution (50 g/L) for 5 min. Subsequently, 1 mL of AlCl₃ solution (100 g/L) was added and allowed to react for 5 min, followed by the addition of 2 mL of NaOH solution (2 mol/L). The mixture was incubated in the dark at room temperature for 10 min, and the absorbance was measured at 510 nm. Total flavonoid content was calculated by substituting the absorbance into the standard curve. The regression equation for the standard curve was y = 5.6836× − 0.0152 (R² = 0.9928).

2.6. In vitro antioxidant activity determination

2.6.1. DPPH radical-scavenging activity

To determine the DPPH radical-scavenging activity, we used the method described by Wu et al. (2020), with slight modifications. A 2 mL aliquot of anhydrous ethanol and 2 mL of the sample were mixed with 2 mL of DPPH methanol solution (0.1 mM) and incubated in the dark at room temperature for 30 min. Absorbance was measured at 517 nm. The DPPH radical-scavenging activity was calculated using the following formula:

$$\text{DPPH radical}-\text{scavenging activity}\left(\%\right)=\left({\mathrm{A}}_0–{\mathrm{A}}_1\right)/{\mathrm{A}}_0\times 100$$ (3)

where A₀ is the absorbance of the blank sample and A₁ is the absorbance of the sample.

2.6.2. ABTS radical-scavenging activity

We determined the ABTS radical-scavenging activity using the method described by Di Cagno et al. (2019), with slight modifications. The ABTS radical cation stock solution was prepared by mixing equal volumes of ABTS solution (7 mmol/L) and K₂S₂O₈ solution (2.45 mmol/L) and incubating the mixture in the dark at room temperature for 16 h. The solution was diluted with 80 % anhydrous ethanol to achieve an absorbance of 0.70 ± 0.02 at 734 nm. A 400 μL aliquot of the diluted sample (50 times) was mixed with 3.6 mL of the ABTS solution and incubated in the dark at room temperature for 30 min. The absorbance was measured at 734 nm. The ABTS radical-scavenging activity was calculated as follows:

$$\text{ABTS radical}-\text{scavenging activity}\left(\%\right)=\left({\mathrm{A}}_0–{\mathrm{A}}_1\right)/{\mathrm{A}}_0\times 100$$ (4)

where A₀ is the absorbance of the blank sample and A₁ is the absorbance of the sample.

2.6.3. Ferric ion-reducing antioxidant power

The determination of ferric ion-reducing antioxidant power (FRAP) was conducted following the method described by Suárez-Jacobo et al. (2011), with slight modifications. The FRAP working solution was freshly prepared by mixing 0.3 mol/L acetate buffer solution (pH = 3.6), 20 mmol/L FeCl₃·6H₂O solution, and 10 mmol/L TPTZ solution (prepared in 40 mmol/L HCl) in a 10:1:1 ratio. The mixture was incubated in a water bath at 37 °C for 30 min.

2.7. Monophenol content determination

The monophenol content of the fruit wine was determined using an LC-20 A high-performance liquid chromatography (HPLC) system (Shimadzu Corporation, Japan) according to the method described by Kaprasob et al. (2017), with slight modifications. A C18 reversed-phase analytical column (Waters Corporation, USA) was used, with specifications of 5 μm and 250 mm × 4.6 mm. The column temperature was set to 30 °C, and detection was performed at 280 nm using a diode array detector. The flow rate was 1 mL/min, and the injection volume was 10 μL. The mobile phase consisted of solvent A (1 % formic acid in water) and solvent B (acetonitrile), using the following gradient elution program: 0–5 min (5 % B); 5–25 min (12 % B); 25–40 min (30 % B); 40–50 min (45 % B); and 50–60 min (5 % B).

Prior to measurement, all samples and standard solutions were degassed using a UP3200H ultrasonic cleaner (Panda Group Nanjing Electronic Measurement Co., Ltd., China) and filtered through a 0.45 μm membrane filter. The external standard method was used for linear regression analysis of the 10 phenolic compounds, and the regression equations for the working curves are shown in Table 1.

Table 1.

Equation of liner regression of 10 phenolic profiles.

Component	Standard curve	Coefficient of determination(R2)
Gallic acid	y = 30,697× – 16,655	0.9979
Chlorogenic acid	y = 20,773× – 36,505	0.9973
Caffeic acid	y = 126,939× – 43,643	0.9988
L-Epicatechin	y = 7272.4× – 1986.9	0.9997
P-Coumaric acid	y = 59,479× – 73,919	0.9951
Ferulic acid	y = 30,963× – 17,164	0.9978
Ellagic acid	y = 6378.5× – 24,833	0.9956
Rutin	y = 9009.4× – 7373.2	0.9987
Phlorizin	y = 26,342× – 71,597	0.9952
Quercetin	y = 23,765× – 41,745	0.9992

2.8. Volatile component determination

An 8 mL sample of kiwifruit wine was placed in a 20 mL vial specifically designed for solid-phase microextraction (SPME). Sequentially, 1.5 g of sodium chloride and 10.0 μL of the internal standard 2-octanol (final concentration of 62.4 μg/L) were added, and the vial was sealed with a PTFE–silicon septum. The freshly purchased SPME fiber was preconditioned by inserting it into the injection port of a GCMS-QP2010 Ultra gas chromatograph–mass spectrometer (Shimadzu Corporation, Japan) at 250 °C for 30 min. The sample was placed on the autosampler tray and extracted at 45 °C for 60 min. After adsorption, the fiber was automatically inserted into the gas chromatography–mass spectrometry (GC–MS) injection port for desorption at 230 °C for 2 min (Salas-Millán et al., 2022), followed by GC–MS analysis.

The initial column temperature was set to 40 °C, with an injection port temperature of 230 °C. The temperature program was as follows: the initial temperature was held at 40 °C for 3 min, increased to 110 °C at a rate of 3 °C/min, increased to 120 °C at a rate of 4 °C/min, increased to 210 °C at a rate of 6 °C/min, and held at 210 °C for 9 min. The temperature was then increased to 240 °C at a rate of 25 °C/min and maintained for 3 min. We used He as the carrier gas at a flow rate of 1.0 mL/min, with splitless injection. The mass spectrometry conditions were as follows: ionization was conducted using an EI source with an electron energy of 70 eV; the ion source temperature was 230 °C; and the mass scan range was m/z 35–500 amu (Wang et al., 2025).

The unknown compounds were analyzed using computer-assisted matching against the NIST (107 k compounds) and Wiley (320 k compounds, version 6.0) libraries for qualitative analysis. Results with a similarity exceeding 85 % were retained. For the semi-quantitative analysis of common representative acids, alcohols, esters, aldehydes, and ketones in kiwifruit wine, 2-octanol was used as an internal standard. The concentrations of the volatile compounds were calculated by comparing the peak areas of each volatile compound with those of the internal standard using the following equation:

$$\text{Concentration of each component}\left(\mathrm{\mu g}/\mathrm{L}\right)=\left(\text{peak area of each component}\times \text{concentrations of the internal standard}\right)/\text{areas of the internal standard}$$ (5)

2.9. Kiwifruit wine sensory evaluation

A scoring system for kiwifruit wine was established, with a total score of 100 points. A panel of 10 professional evaluators assessed the clarity (10 points), color (10 points), aroma (30 points), taste (30 points), and typicality (20 points) of kiwifruit wine before and after HHP treatment. The evaluations were conducted using ISO official tasting glasses (ISO 3591.1977), and corresponding scores were assigned accordingly.

2.10. Statistical analysis

Data processing and analysis were conducted using Excel 2018 and Minitab 18. Stacked bar charts, cluster heat maps, and radar charts were generated using Origin 2021 software. CNSplots (https://cnsknowall.com/#/HomePage) was used to draw a Venn diagram. Principal component analysis (PCA) and further analysis were performed with MetaboAnalyst 6.0 (https://new.metaboanalyst.ca/MetaboAnalyst/ModuleView.xhtml). Each experiment was performed in triplicate, with statistical significance defined as p < 0.05.

3. Results and discussion

3.1. Effects of HHP treatment on the physicochemical properties of kiwifruit wine

The basic physicochemical properties of kiwifruit wine before and after HHP treatment are listed in Table 2. Key indicators commonly used to assess the quality of fruit wines, such as alcohol content, residual sugar, total acidity, pH, and dry extract content, were also evaluated. The SSC was the lowest in wine treated at 400 MPa, with a value of 8.50°Brix. This decrease in SSC may be attributable to structural changes within the fruit tissue caused by HHP, such as slight damage to cell walls and membranes, which may have affected the SSC content (Bernaerts et al., 2019).

Table 2.

Physicochemical properties of kiwifruit wine treated with different high hydrostati c pressure.

Physico-chemical Parameters	Untreated Wine	300 MPa	400 MPa	500 MPa	600 MPa
soluble solid content	8.83 ± 0.06a	8.77 ± 0.06a	8.50 ± 0.17a	8.73 ± 0.21a	8.67 ± 0.15a
Alcohol by volume	11.9 ± 0.00b	11.9 ± 0.00b	11.5 ± 0.00c	12.1 ± 0.00a	12.1 ± 0.00a
PH	3.26 ± 0.02b	3.33 ± 0.01a	3.34 ± 0.02a	3.35 ± 0.02a	3.34 ± 0.02a
Total acidity	14.25 ± 0.37b	15.38 ± 0.19a	14.81 ± 0.19ab	15.06 ± 0.29a	15.28 ± 0.26a
Transmittance	83.10 ± 0.32b	84.10 ± 0.18a	82.73 ± 0.13b	82.65 ± 0.06b	83.68 ± 0.20a

Note: SSC (°Brix), Alcohol content (% vol), Titratable acidity expressed as tartaric acid.

(g/L), Transmittance (%), different letters in the table indicate significant differences betwe.

en groups (p < 0.05).

The pH of wine treated at 500 MPa was significantly higher than that of the control group (p < 0.05), peaking at 3.35. However, the differences in pH among the treatment groups were not significant (p < 0.05). Similarly, Briones-Labarca et al. (2017) reported that red wine subjected to 300–500 MPa for 5, 10, and 15 min showed no significant changes in pH, which aligns with the results of this study. The increase in pH may be attributed to the conformational changes of proteins and the inhibition of peroxidase activity in kiwifruit wine induced by HHP, which could affect the stability or degradation of organic acids, thereby indirectly altering the pH value (Fang et al., 2008).

The alcohol content decreased significantly compared with that of the control group only when the wine was subjected to 400 MPa (p < 0.05), with a reduction of 3.4 %. This pressure may promote oxidation and esterification reactions in kiwifruit wine. Additionally, HHP provides energy that facilitates various chemical reactions within wine, potentially contributing to a reduction in the ethanol content (Zhao et al., 2017). Conversely, at 500 and 600 MPa, the alcohol content increased significantly compared with that in the control group (p < 0.05). Under these conditions, esterification-related enzymes may undergo conformational changes, suppressing esterification and leading to reduced ester levels with a relative increase in free alcohols, thereby elevating the measured alcohol content. Similar observations have been reported in wines subjected to high hydrostatic pressure (Otero et al., 2025).

Compared with that of the control group, the titratable acidity of the kiwifruit wine increased under most HHP treatments, except at 400 MPa, where it was the lowest. This may have been caused by reactions in which alcohols and acids formed esters, followed by the oxidation of alcohols to aldehydes and further to acids, ultimately increasing total acidity. The lower acidity observed at 400 MPa may help preserve a higher concentration of aromatic compounds, allowing the wine to retain more of its characteristic fruity aroma. This contributes to enhanced fragrance, reduced harshness, and a more balanced flavor profile.

The transmittance was highest at 300 MPa and exhibited a trend of first decreasing and then increasing as pressure increased. Transmittance in the 300 and 600 MPa groups was significantly higher than that in the untreated group, suggesting that moderate HHP treatment improved wine clarity by reducing turbidity (p < 0.05).

3.2. Effects of HHP treatment on the color of kiwifruit wine

Table 3 shows the color changes in kiwifruit wine under different pressure treatments. The L* value reflects wine lightness, with a positive correlation between the L* value and brightness. A smaller L* value indicates a darker wine color and vice versa. Kiwifruit wine treated with HHP displayed significantly lower L* values than the untreated control (p < 0.05), with values ranging from 91.73 to 92.64. This decrease may be attributable to pressure-induced aggregation within the wine matrix (Jaeckels et al., 2016). Despite this reduction, the L* values remained high, indicating that the wine retained considerable brightness. Notably, Rios-Corripio et al. (2020) suggested that L* values may be influenced by various factors, such as the type of fruit used in fermentation, complexity of the food matrix, and different HHP pressures and durations.

Table 3.

The color of kiwifruit wine treated with different high hydrostatic pressure.

Color Indices	L*	a*	b*	ΔE
Untreated wine	93.01 ± 0.01a	−1.40 ± 0.01b	15.38 ± 0.06c	–
300 MPa	92.64 ± 0.02ab	−1.30 ± 0.01b	15.34 ± 0.08c	0.39 ± 0.01b
400 MPa	91.73 ± 0.60c	−1.12 ± 0.07a	15.41 ± 0.10c	1.31 ± 0.60 ab
500 MPa	91.93 ± 0.09bc	−1.18 ± 0.01a	15.85 ± 0.15b	1.20 ± 0.14 ab
600 MPa	91.58 ± 0.41c	−1.09 ± 0.06a	16.15 ± 0.13a	1.65 ± 0.42a

Note: Different letters in the table indicate significant differences between groups (p < 0.05).

The a* value reflects the red/green balance of wine color. Higher a* values indicate deeper red tones, whereas lower a* values indicate more green tones. The untreated kiwifruit wine had an a* value of approximately −1.40. After HHP, the a* values ranged from −1.30 to −1.09, showing a gradual increase with increasing pressure and reaching the highest a* value of −1.09 at 600 MPa. Therefore, the wine exhibited the deepest red tone at 600 MPa. This change may have been primarily due to high pressure-induced covalent bonding between anthocyanins and other organic acids or flavonols, leading to deeper red hues in the wine (Cao et al., 2023).

The b* value reflects the yellow/blue balance of wine color. A higher b* value indicates a stronger yellow tone. As shown in Table 3, the untreated wine had a b* value of 15.38. The b* value in the treated groups increased with increasing pressure, reaching a maximum of 16.15 at 600 MPa, indicating that the wine had the most pronounced yellow color at this pressure.

In summary, after HHP, the L* value of kiwifruit wine significantly decreased (p < 0.05), whereas the a* and b* values gradually increased, resulting in a color shift toward pale green and yellow. According to Li et al. (2022), the color of kiwifruit wine is influenced by factors such as the variety and morphology of the raw materials; however, wines with a more vivid yellow or green color closer to the natural color of kiwifruit are generally preferred by consumers.

To determine whether the color changes in kiwifruit wine after HHP were noticeable by the naked eye, the total color difference (ΔE) was calculated to assess the visual impact of HHP. The results showed that the ΔE values for all treated wines were < 3, indicating that the color changes were not perceptible by the naked eye. In particular, the wine treated at 300 MPa exhibited a color closest to that of the untreated wine.

According to Keenan et al. (2011), although the color parameters of pomegranate beverages changed after HHP, these changes were not detectable by the naked eye, confirming the results of the current study. This suggests that, overall, HHP had little impact on the appearance of kiwifruit wine. A visual comparison of the color of kiwifruit wine before and after HHP is shown in Fig. 1.

Fig. 1.

Color of kiwifruit wine before and after high hydrostatic pressure treatment.

3.3. Effects of HHP treatment on the total phenolic and flavonoid contents of kiwifruit wine

The total phenolic and flavonoid contents of kiwifruit wine subjected to different HHP conditions are shown in Fig. 2. These bioactive compounds are crucial for assessing the nutritional and functional qualities of wines. The results of this study elucidate how HHP treatment affects the retention or degradation of these compounds, ultimately influencing the health benefits and quality of the final product.

Fig. 2.

Total phenols content (A) and total flavonoids content (B) of kiwifruit wine treated with different high hydrostatic pressure.Note: Different lowercase letters above the bars indicate significant differences between groups (p < 0.05).

Polyphenols are the primary active compounds in fruit wines and represent one of the most important parameters reflecting the overall quality of wine. As shown in Fig. 2A, the untreated kiwifruit wine had a total phenolic content of 884.00 mg gallic acid equivalent (GAE)/L. After HHP treatment, the total phenolic content initially increased with increasing pressure and then decreased, with values of 891.24, 924.67, 882.13, and 877.56 mg GAE/L at 300, 400, 500, and 600 MPa, respectively. The highest total phenolic content was observed at 400 MPa, reaching 924.67 mg GAE/L, which was 4.60 % higher than that of the untreated group. Overall, the differences between the treated and untreated groups were not significant (p < 0.05), indicating that HHP treatment had a minimal effect on the total phenolic content.

Flavonoids in kiwifruit wine primarily enhance the antioxidant activity, improve the overall quality, and potentially enrich the sensory attributes (Oliveira et al., 2022). Fig. 2B shows that the total flavonoid content of kiwifruit wine decreased significantly under HHP treatment compared with that under the control (p < 0.05). The total flavonoid content of the control wine was 410.68 mg rutin equivalents (RE)/L, and those of the wine treated with 300, 400, 500, and 600 MPa were 367.17, 357.81, 371.30, and 343.62 mg RE/L, respectively. The smallest reduction occurred at 500 MPa (9.59 %), followed by that at 300 MPa (10.59 %). Studies have shown that HHP treatment can alter the complex chemical bonds within flavonoids and promote their reactivity with other compounds (Kim et al., 2024). Although direct evidence is limited, studies on similar systems suggest that HHP significantly reduces the flavonoid content (p < 0.05). For instance, Sun et al. (2016) reported that HHP markedly decreased the levels of flavonoid compounds, such as flavan-3-ols, during red wine aging (p < 0.05). The pressure, time, and temperature parameters of HHP may influence the total flavonoid content, although the underlying mechanisms have not been identified.

3.4. Effects of HHP treatment on the in vitro antioxidant activity of kiwifruit wine

The effects of different pressure treatments on the in vitro antioxidant activity of kiwifruit wine were investigated, and the results are shown in Fig. 3. Wine treated at 400 MPa exhibited the strongest DPPH radical-scavenging activity (66.12 %) (Fig. 3A), which was 4.99 % higher than that of the control. The DPPH radical-scavenging abilities of the other treatment groups were lower than those of the control group. The 400 MPa treatment not only resulted in the highest total phenolic content but also enhanced the ability to scavenge DPPH radicals. This demonstrates that the 400 MPa treatment had a considerable retention effect on the phenolic compounds in kiwifruit wine, leading to stronger DPPH radical-scavenging activity. These findings were consistent with those of Shen et al. (2016), who observed a significant increase in the total phenolic content at 400 MPa, and with those of previous reports that wines with higher total phenolic contents exhibit greater antioxidant activity (Olejar et al., 2015; Shen et al., 2016).

Fig. 3.

DPPH radical scavenging capacity (A), ABTS radical-scavenging capacity (B) and FRAP (C) of kiwifruit wine treated with different high hydrostatic pressure.Note: Different lowercase letters above the bars indicate significant differences between groups(p < 0.05).

As shown in Fig. 3B, within the 300–500 MPa pressure range, the ABTS radical-scavenging activity of kiwifruit wine was slightly enhanced. Wine treated at 300 MPa demonstrated a significantly stronger ABTS radical-scavenging ability than the control group, with an increase of 5.47 % (p < 0.05). Fig. 3C shows that most pressure treatments increased the FRAP of kiwifruit wine compared with that of the untreated wine. The wine treated at 600 MPa exhibited the highest FRAP value of 6.84 mmol Trolox/L, which was 10.32 % higher than that of the control.

Although total polyphenol content peaked at 400 MPa, the FRAP value peaked at 600 MPa, indicating that the antioxidant activity of kiwifruit wine cannot be ascribed solely to polyphenolic compounds. Research has demonstrated that HPP effectively preserves water-soluble antioxidants such as ascorbic acid (vitamin C), which contribute substantially to FRAP measurements (Pérez-Lamela, Franco and Falqué, 2021a, Pérez-Lamela, Franco and Falqué, 2021b). Additionally, higher pressure conditions may induce Maillard reactions, generating products (MRPs) that exhibit metal ion chelation and free radical scavenging properties while enhancing FRAP-reducing capacity (Nooshkam et al., 2019). The 600 MPa treatment may have promoted Maillard reaction product formation or enhanced the activity of other antioxidants, such as ascorbic acid, thereby augmenting the wine's iron-reducing capacity. In summary, HPP technology likely increased the permeability of semi-permeable membranes, disrupted ion gradients, and promoted the release of intracellular compounds. By targeting cell walls, it efficiently released antioxidants such as polyphenols, anthocyanins, and carotenoids while better preserving antioxidant activity compared with thermal treatment.

3.5. Effects of HHP treatment on the monophenol content of kiwifruit wine

Numerous studies have shown that polyphenolic compounds affect the color and flavor of fruit wines (Cabral et al., 2022). The monophenol content of kiwifruit wine before and after HHP treatment was determined and analyzed using HPLC. The results (Table 4) indicate that nine phenolic compounds, including gallic acid, chlorogenic acid, and caffeic acid, were identified in kiwifruit wine samples. Among the untreated wines, ellagic acid had the highest concentration (7.91 mg/L), followed by epicatechin (2.80 mg/L) and chlorogenic acid (2.78 mg/L). In the control group, ellagic acid showed the highest concentration (7.91 mg/L), significantly exceeding that of other common phenolic compounds. This elevated level is unlikely to originate solely from the fruit but may instead result from extraction during contact with oak barrels (Michel et al., 2011), as ellagic acid can leach from oak into the wine. Hydrolyzable tannins and their derivatives, together with low-molecular-weight phenolics, may also be released during barrel contact, thereby increasing the phenolic content and influencing wine flavor and stability (Tarko et al., 2024). Moreover, the Folin–Ciocalteu assay often attributes wood-derived phenols to “tannin equivalents,” further amplifying the measured values. Similar phenomena have been observed in barrel-aged ciders, plum wines, and other fruit wines (Pérez et al., 2023). Therefore, the elevated ellagic acid content observed in this study is most likely attributable to exogenous input from barrel contact.

Table 4.

Phenolic profiles (mg/L) of kiwifruit wine treated with different high hydrostatic pressure.

Phenolic compound	Retention time (min)	Unprocessed wine	300 MPa	400 MPa	500 MPa	600 MPa
Gallic acid	5.02	1.40 ± 0.005d	2.73 ± 0.050b	5.36 ± 0.082a	2.03 ± 0.076c	1.94 ± 0.063c
Chlorogenic acid	21.19	2.78 ± 0.099b	2.85 ± 0.039b	2.32 ± 0.033d	2.60 ± 0.030c	3.25 ± 0.002a
Caffeic acid	26.53	0.40 ± 0.001c	0.61 ± 0.006a	0.47 ± 0.004b	0.38 ± 0.001d	0.38 ± 0.000a
L-Epicatechin	30.40	2.80 ± 0.175a	1.98 ± 0.178b	2.07 ± 0.314b	2.74 ± 0.003a	0.93 ± 0.011c
p-Coumaric acid	35.37	2.18 ± 0.031a	1.44 ± 0.015c	1.77 ± 0.034b	1.27 ± 0.000d	1.41 ± 0.002c
Ferulic acid	36.03	0.66 ± 0.013d	1.76 ± 0.060a	1.51 ± 0.032b	0.91 ± 0.010c	0.97 ± 0.028c
Ellagic acid	38.12	7.91 ± 0.000a	5.39 ± 0.086c	5.97 ± 0.096b	4.94 ± 0.031e	5.19 ± 0.006d
Rutin	36.70	1.34 ± 0.015e	1.99 ± 0.009d	2.60 ± 0.004c	3.57 ± 0.015b	3.91 ± 0.044a
Phlorizin	43.80	1.94 ± 0.063d	2.97 ± 0.065b	3.11 ± 0.019a	2.78 ± 0.010d	2.88 ± 0.007c

Note: Different lowercase letters in the table indicate significant differences between group.

s(p < 0.05).

After HHP treatment, ellagic acid remained the most abundant phenolic compound, with levels ranging from 4.94 to 5.97 mg/L. However, compared with that in the control group, the content in the treatment groups was significantly decreased (p < 0.05). Additionally, the ellagic acid content showed a trend of first increasing, then decreasing, and finally increasing again as the pressure increased, with the highest value of 5.97 mg/L observed at 400 MPa, which was significantly higher than that at the other pressures (p < 0.05).

The gallic acid, rutin, naringin, and ferulic acid contents increased significantly (p < 0.05) after HHP treatment compared with those in the control group, whereas the epicatechin and p-coumaric acid levels decreased. The caffeic acid content increased at processing pressures below 400 MPa but declined at higher pressures. This increase may have resulted from enhanced hydrolysis of chlorogenic acid under mild HPP conditions, leading to greater caffeic acid release (Pérez-Lamela, Franco and Falqué, 2021a, Pérez-Lamela, Franco and Falqué, 2021b). Above 400 MPa, caffeic acid may undergo oxidative degradation or polymerize with other phenolics into larger molecules, thereby reducing its free form content (Jeż et al., 2018).

At 400 MPa, the levels of gallic acid and naringin in kiwifruit wine significantly increased (p < 0.05). Compared with that in the untreated group, the naringin content increased 1.6 fold, and the gallic acid content increased by approximately 4 fold, which may be attributable to the hydrolysis of certain ellagitannins. Overall, the total monophenol content of kiwifruit wine increased under the 400 MPa treatment, which was consistent with the results of previous studies showing that HHP treatment has a positive effect on the enrichment of phenolic compounds, thereby improving the sensory quality of kiwifruit wine (Hossain et al., 2022; Kim et al., 2017).

We performed PCA of individual phenolic compounds to elucidate their impact on the overall quality of kiwifruit wine. As illustrated in Fig. 4, most phenolics loaded positively on both the first (PC1, 45.3 %) and second (PC2, 30.9 %) principal components, whereas chlorogenic acid and rutin exhibited negative loadings on PC2. Kiwifruit wines treated at 300 and 400 MPa were located in the first quadrant, which contributed to both PC1 and PC2 and were highly correlated with caffeic acid and ferulic acid components. The distinct spatial distribution of samples across quadrants underscored the differential effects of varying HHP treatments on the wine's phenolic profile.

Fig. 4.

Principal component analysis (PCA) of aromatic compounds under different pressure treatments A and B. Note: A is a PCA plane diagram. B is a 3D diagram.

3.6. Effects of HHP treatment on the volatile components of kiwifruit wine

The volatile components of kiwifruit wine before and after HHP were analyzed using GC–MS (Table 5). As shown in Fig. 5A, analysis of the volatile components in kiwifruit wine before and after HHP treatment revealed that the untreated wine contained 44 volatile components, including 15 alcohols, 22 esters, 2 acids, and 5 aldehydes and ketones, with concentrations of 663.44, 321.81, 3.66, and 5.07 μg/L, respectively. Fig. 5B illustrates that alcohols and esters accounted for 66.75 % and 32.38 % of the total volatile content, respectively. After various pressure treatments, the total number of volatile components in the kiwifruit wine increased significantly (p < 0.05). As shown in Fig. 5C and Table 5, the volatile components in the four pressure-treated wine samples were as follows: 300 MPa (52 components, 940.98 μg/L), 400 MPa (50 components, 1066.14 μg/L), 500 MPa (54 components, 1329.70 μg/L), and 600 MPa (53 components, 1176.57 μg/L). Notably, the number of volatile aromatic components and the total volatile content were the highest in the 500 MPa-treated wine.

Table 5.

Analysis of volatile compounds (μg/L) of kiwifruit wine treated with different high hydrostatic pressure(means ± SD, n = 3).

Number	Compounds	Unprocessed wine	300 MPa	400 MPa	500 MPa	600 MPa
	Alcohol
1	2-Methyl-1-propanol	66.24 ± 2.29a	ND	45.64 ± 1.33c	60.87 ± 1.54b	ND
2	Butanol	1.31 ± 0.04a	0.79 ± 0.03c	0.52 ± 0.02d	1.02 ± 0.03b	1.04 ± 0.01b
3	3-Methyl-1-butanol	250.60 ± 7.71a	153.44 ± 3.05e	171.73 ± 2.25d	226.74 ± 5.10c	240.03 ± 4.10b
4	2-Methyl-1-butanol	107.36 ± 2.91a	72.06 ± 1.16e	76.61 ± 2.30d	96.86 ± 2.64b	91.38 ± 2.27c
5	Pentanol	1.00 ± 0.03	ND	ND	ND	ND
6	Ethanol,2-(1-methylethoxy)-	12.72 ± 0.46	ND	ND	ND	ND
7	(R,R)-2,3-Butanediol	1.67 ± 0.04	ND	ND	ND	ND
8	(E)-3-Hexen-1-ol	1.52 ± 0.04a	0.88 ± 0.03c	0.81 ± 0.02d	1.12 ± 0.02b	1.53 ± 0.03a
9	Hexyl alcohol	81.05 ± 2.43a	51.35 ± 1.39d	55.25 ± 1.53c	72.19 ± 1.97b	ND
10	3-Methylthiopropanol	ND	ND	1.65 ± 0.05	2.40 ± 0.10	ND
11	Heptanol	ND	0.41 ± 0.02c	0.90 ± 0.03b	1.12 ± 0.04a	ND
12	2-Octanol	62.42 ± 0	62.42 ± 0	62.42 ± 0	62.42 ± 0	62.42 ± 0
13	Benzyl alcohol	ND	ND	ND	ND	0.77 ± 0.02
14	Cineole	15.28 ± 0.50a	9.23 ± 0.31c	9.56 ± 0.35c	12.63 ± 0.41b	14.96 ± 0.50a
15	trans-2-Octen-1-ol	0.78 ± 0.02b	0.43 ± 0.01e	0.54 ± 0.02d	0.62 ± 0.02c	1.05 ± 0.03a
16	1-Octanol	5.83 ± 0.25a	3.40 ± 0.10d	4.09 ± 0.20c	4.84 ± 0.15b	5.86 ± 0.15a
17	Phenethyl alcohol	48.44 ± 1.28a	23.00 ± 1.00d	36.65 ± 1.04c	42.66 ± 1.01b	41.86 ± 1.00b
18	Nonanol	3.00 ± 0.10c	3.40 ± 0.10b	ND	6.55 ± 0.25a	ND
19	Decyl alcohol	7.21 ± 0.20	ND	ND	ND	ND
	Acids
1	Acetic acid	ND	ND	ND	4.30 ± 0.10	4.03 ± 0.15
2	Butyric acid	ND	ND	1.62 ± 0.04	ND	ND
3	2-Methylbutyric acid	0.87 ± 0.03	ND	ND	ND	0.91 ± 0.03
4	Hexanoic acid	2.78 ± 0.08b	1.95 ± 0.05d	2.50 ± 0.10c	2.50 ± 0.05c	4.16 ± 0.15a
5	Nonanoic acid	ND	ND	ND	ND	8.61 ± 0.36
	Ketones
1	3-Octanone	1.27 ± 0.04a	0.56 ± 0.02c	ND	0.73 ± 0.03b	ND
2	2-Octanone	0.47 ± 0.02	0.27 ± 0.01	ND	ND	ND
3	2-Heptanone	ND	ND	ND	ND	0.39 ± 0.01
4	Acetaldehyde	0.75 ± 0.03	ND	ND	ND	ND
5	Benzaldehyde	2.23 ± 0.08a	ND	0.73 ± 0.02d	1.10 ± 0.03c	1.30 ± 0.04b
6	(E)-2-Octenal	ND	0.53 ± 0.02c	0.66 ± 0.03b	1.05 ± 0.05a	0.72 ± 0.03b
7	Decanal	ND	0.38 ± 0.02c	0.66 ± 0.03b	ND	0.78 ± 0.03a
8	trans-2-Decenal	0.34 ± 0.01e	0.40 ± 0.02d	0.47 ± 0.02c	0.85 ± 0.03a	0.74 ± 0.03b
1	Methyl acetate	ND	ND	ND	0.97 ± 0.03	0.90 ± 0.03
2	Ethyl acetate	71.14 ± 2.35a	45.03 ± 1.45e	48.75 ± 1.75d	58.45 ± 2.00b	54.94 ± 1.78c
3	Silanediol,1,1-dimethyl-	10.44 ± 0.42a	5.58 ± 0.27d	9.59 ± 0.30b	9.95 ± 0.41ab	6.90 ± 0.30c
4	Ethyl propionate	ND	0.19 ± 0.01	0.20 ± 0.01	ND	ND
5	Methyl butyrate	17.30 ± 0.60a	11.45 ± 0.35c	11.70 ± 0.40c	15.45 ± 0.55b	15.39 ± 0.60b
6	Ethyl isobutyrate	2.79 ± 0.09b	0.79 ± 0.03d	ND	1.39 ± 0.04c	2.99 ± 0.10a
7	Butyl acetate	ND	ND	4.43 ± 0.15	ND	ND
8	Isobutyl acetate	ND	4.20 ± 0.20b	ND	7.50 ± 0.36a	7.98 ± 0.38a
9	Ethyl butyrate	37.27 ± 1.20a	23.99 ± 0.80c	24.83 ± 0.85c	33.01 ± 1.00b	34.00 ± 1.01b
10	Ethyl lactate	1.15 ± 0.04a	0.40 ± 0.02e	0.52 ± 0.02d	0.72 ± 0.02c	0.97 ± 0.03b
11	Isoamyl acetate	32.20 ± 1.00a	21.50 ± 0.70c	22.65 ± 0.75c	28.60 ± 0.90b	29.27 ± 0.96b
12	2-Methylbutyl acetate	7.18 ± 0.31a	4.41 ± 0.26c	4.55 ± 0.26c	5.92 ± 0.26b	6.29 ± 0.30b
13	Methyl hexanoate	0.71 ± 0.02a	0.44 ± 0.02b	0.42 ± 0.02c	0.60 ± 0.02d	0.60 ± 0.02d
14	Isobutyl butyrate	0.82 ± 0.03a	0.38 ± 0.01c	0.39 ± 0.01c	0.51 ± 0.02b	0.80 ± 0.03a
15	Ethyl caproate	110.64 ± 3.76a	74.62 ± 2.40c	77.11 ± 2.59c	97.88 ± 3.15b	98.28 ± 3.26b
16	Hexyl acetate	5.08 ± 0.18a	3.31 ± 0.10d	3.39 ± 0.10d	4.35 ± 0.15c	4.71 ± 0.15b
17	Isoamyl butyrate	2.90 ± 0.10a	1.84 ± 0.06d	2.08 ± 0.08c	2.57 ± 0.09b	2.68 ± 0.10b
18	Methyl benzoate	1.58 ± 0.05a	ND	0.92 ± 0.03c	1.28 ± 0.04b	1.54 ± 0.05a
19	Ethyl heptanoate	2.16 ± 0.07a	1.39 ± 0.05d	1.48 ± 0.05d	1.83 ± 0.06c	1.98 ± 0.06b
20	Methyl octanoate	7.53 ± 0.26a	2.84 ± 0.10d	ND	3.79 ± 0.13c	6.83 ± 0.26b
21	Isobutyl hexanoate	ND	1.01 ± 0.04	1.08 ± 0.04	ND	ND
22	Ethyl benzoate	ND	2.40 ± 0.10	ND	ND	ND
23	Hexyl butyrate	ND	0.16 ± 0.01	0.15 ± 0.01	ND	ND
24	Ethyl caprylate	ND	209.42 ± 7.01c	227.62 ± 7.40b	276.13 ± 9.17a	261.87 ± 9.05a
25	Phenethyl acetate	0.56 ± 0.02a	0.31 ± 0.01d	0.45 ± 0.02b	0.40 ± 0.02c	0.54 ± 0.02a
26	Isopentyl hexanoate	2.07 ± 0.07a	1.43 ± 0.05d	1.55 ± 0.06c	1.76 ± 0.07b	1.77 ± 0.06b
27	Caprylicacidisopropylester	ND	0.21 ± 0.01	ND	0.26 ± 0.01	ND
28	Ethyl nonanoate	3.61 ± 0.10a	2.87 ± 0.10c	3.13 ± 0.11b	3.44 ± 0.11a	3.01 ± 0.10bc
29	Methyl n-caprate	2.90 ± 0.10a	1.07 ± 0.04e	1.35 ± 0.05d	1.57 ± 0.05c	2.37 ± 0.08b
30	Octanoic acid,2-methylpropyl ester	ND	ND	1.56 ± 0.06b	1.78 ± 0.07a	1.52 ± 0.05b
31	Butyl benzoate	ND	ND	ND	ND	0.93 ± 0.03
32	Isobutyl octanoate	1.79 ± 0.06	1.47 ± 0.05	ND	ND	ND
33	Ethyl caprate	ND	105.72 ± 3.59b	111.10 ± 3.68b	130.46 ± 4.28a	111.15 ± 3.56b
34	Decanoic acid,2-methylpropyl ester	ND	0.74 ± 0.03a	0.61 ± 0.02c	0.66 ± 0.02b	0.72 ± 0.02a
35	Ethyl laurate	ND	24.40 ± 0.80b	24.66 ± 0.85b	27.23 ± 0.91a	22.42 ± 0.75c
36	Decanoic acid, 3-methylbutyl ester	ND	0.88 ± 0.03c	0.84 ± 0.03c	1.09 ± 0.04b	1.57 ± 0.05a
37	Ethyl myristate	ND	2.93 ± 0.10b	2.92 ± 0.10b	3.38 ± 0.11a	3.56 ± 0.12a
38	Isopropyl myristate	0.26 ± 0.01c	0.52 ± 0.02a	0.41 ± 0.02b	0.25 ± 0.01c	0.26 ± 0.01c
39	Dodecanoic acid,3-methylbutyl ester	ND	ND	0.27 ± 0.01	ND	ND
40	Dibutyl phthalate	ND	ND	ND	0.21 ± 0.01	ND
41	9-Hexadecenoic acid,ethyl ester	ND	ND	0.30 ± 0.01	0.30 ± 0.01	ND
42	Ethyl palmitate	1.86 ± 0.05d	2.84 ± 0.10c	3.27 ± 0.11a	3.07 ± 0.10b	1.86 ± 0.05d

Different lowercase letters in the table indicate significant differences between groups(p < 0.05); ‘ND’ means not detected.

Fig. 5.

Analysis of volatile components in kiwifruit wine treated with different ultra-high pressures. (A) Quantity of compounds; (B) Percentage composition of different compounds; (C) Venn diagram of compounds; (D) Principle component analysis biplot of compounds.

Further analysis of key aroma compounds with OAV > 1 (isobutanol, isoamyl alcohol, 2-methyl-1-butanol, n-hexanol, ethyl acetate, ethyl isobutyrate, ethyl butyrate, ethyl isovalerate, 2-methylbutyl acetate, ethyl hexanoate, and ethyl heptanoate) showed that HHP treatment did not significantly enhance their contents but instead tended to decrease them. In contrast, HHP markedly increased the diversity of ester volatiles. Except for the 300 MPa group, all other pressure treatments significantly elevated total volatile concentrations. This enrichment is likely due to HHP facilitating the release or transformation of aroma precursors. Several mechanisms may explain this phenomenon. First, HHP disrupts cell walls and subcellular structures, promoting the release of bound or encapsulated aroma precursors such as amino acids and fatty acids (Lomelí-Martín et al., 2021). Second, HHP can regulate aroma-related enzymes, including alcohol dehydrogenase (ADH) and alcohol acyltransferase (AAT), thereby promoting alcohol-to-ester conversion under certain pressure conditions (Zheng et al., 2024). Moreover, high pressure may shift reaction equilibria, accelerating esterification or oxidation, which reduces some key alcohols while increasing newly formed esters (Sun et al., 2023). These results suggest that HHP not only reshapes the volatile profile of kiwifruit wine but may also accelerate wine aging by enhancing precursor release and modulating enzyme activity.

To further clarify how HHP promotes ester formation and accelerates aging, both enzymatic and thermodynamic aspects must be considered. From an enzymatic perspective, moderate pressure (300–500 MPa) can alter protein conformation, improve substrate accessibility of ester-synthesizing enzymes such as alcohol acetyltransferase, and selectively inhibit ester hydrolases. This dual effect of “enhanced synthesis and suppressed hydrolysis” favors a net increase in esters (De Maria et al., 2017). From a thermodynamic perspective, when the activation volume of esterification is negative, high pressure drives the equilibrium toward ester formation (Mozhaev et al., 1996). In addition, HHP may weaken interactions between inhibitory compounds (e.g., polyphenols) and enzymes or substrates, thereby reducing inhibition of esterification (Ling et al., 2025). Traditional wine aging relies on slow oxidation–esterification processes, with the ester-to-alcohol ratio gradually approaching equilibrium (Díaz-Maroto et al., 2005). By contrast, HHP can accelerate these transformations within a short time, producing aroma changes similar to those achieved through long-term aging.

Following HHP treatment, the number and content of alcohol compounds decreased compared with those in untreated wine (Fig. 6), with contents ranging from 377.42 to 592.05 μg/L. In contrast, the ester content increased significantly (p < 0.05), ranging from 559.48 to 727.12 μg/L. Among all treated samples, esters represented the highest proportion of the total volatile aromatic content in the following order: 300 MPa (59.46 %), 600 MPa (58.99 %), 400 MPa (55.66 %), and 500 MPa (54.68 %). Alcohols comprised the highest proportion of the volatile content in the following order: 500 MPa (44.53 %), 400 MPa (43.74 %), 300 MPa (40.11 %), and 600 MPa (39.17 %). These results suggest that high-pressure treatment significantly reduced the alcohol content in kiwifruit wine (p < 0.05), promoted the conversion of alcohols to esters, and aided in the aging process, shifting the wine from exhibiting an alcohol-dominant to an ester-dominant aroma type (Liu, Weng, & Wu, 2020).

Fig. 6.

Heat map of volatile compoundsNote: A heat map combines a heat map with a bar chart, where the heat map shows the size of each data point in the table as changes in color intensity in a matrix, while the bar chart shows the average value of each group to indicate the high and low levels of each category vertically and horizontally.

To better distinguish the changes in volatile components under different pressures, we performed PCA of the aroma components. Fig. 5D shows that PC1 accounted for 81 %, PC2 accounted for 11 %, and the cumulative contribution rate reached 92 %. This indicated that the flavor characteristics of kiwifruit wine under various HHP treatments exhibited strong distinguishability and were independent of each other. Furthermore, these two principal components effectively represented the primary flavor characteristics of the samples. The results for each group were clearly separated, demonstrating good data stability and reproducibility. On PC1, the 300, 400, 500, and 600 MPa treatment groups were clustered on the positive axis, while the control group was positioned on the negative axis. On PC2, the 300 and 400 MPa treatment groups were distributed along the positive axis, while the control and other treatment groups were positioned on the negative axis. In conclusion, PCA effectively distinguished the aroma components of kiwifruit wine under different treatments. The results indicate that the aroma profiles of the 500 and 600 MPa treatment groups were relatively similar, whereas significant differences existed between those of the control group and the treatment groups.

3.7. Effects of HHP treatment on the sensory quality of kiwifruit wine

A flavor radar chart was constructed to visually highlight the differences between kiwifruit wine samples treated under various pressure conditions. HHP treatment significantly improved the sensory quality of kiwifruit wine (p < 0.05).The results are presented in Fig. 7. As illustrated, the clarity of the wines showed little variation, with all treatment groups overlapping closely with the untreated sample, except for the 600 MPa group. This suggests minimal differences in clarity among the samples. However, significant differences were observed in aroma, with the treated groups exhibiting more pronounced changes compared with the control (p < 0.05), indicating that HHP treatment effectively enhanced and enriched the aroma profile of kiwifruit wine. The 400 MPa group showed a clear advantage in this regard, followed by the 300 and 500 MPa groups, while the 600 MPa group displayed a relatively weaker aroma. In terms of color, kiwifruit wine processed at 400 MPa displayed the most vibrant hue (p < 0.05), followed by that treated at 500 MPa. The remaining groups overlapped with the control and showed negligible differences. Regarding typicity, wines treated at 400 and 500 MPa exhibited the most distinct characteristics, with a strong and prominent style. In contrast, wines treated at 600 and 300 MPa demonstrated relatively weaker typicity, although their differences from the 400 and 500 MPa groups were not significant (p < 0.05), and their typicity was still stronger than that of the untreated wine. In terms of taste, little difference was observed between the 400 and 500 MPa groups, as well as between the 300 and 600 MPa groups; however, the latter two lacked the richness, fullness, and harmonious balance of the former two. After HHP treatment, the five key characteristics of kiwifruit wine were significantly enhanced (p < 0.05), contributing to the wine's aging process. Among the pressure treatments, 400 MPa best preserved the unique flavor of kiwifruit, imparted a relatively brighter color, and offered a relatively purer, more balanced taste and a pleasant aroma, making it the most favored by tasters.

Fig. 7.

Flavor radar chart of kiwifruit wine under different pressure treatments.

4. Conclusion

The results of this study offer valuable insights into the acceleration of kiwifruit wine maturation and aging, along with its quality enhancement. Investigations were conducted on the physicochemical properties, phenolic compounds, antioxidant activity, volatile components, and sensory qualities of kiwifruit wine under different HHP treatments. Based on the results, the following conclusions can be drawn:

• (1)Following HHP treatment, the SSC of the wine decreased, the pH increased, and the taste became more balanced and full-bodied. A significant reduction in alcohol content was observed only at 400 MPa, indicating that this pressure promoted oxidative and esterification reactions in kiwifruit wine and resulted in the lowest titratable acid content. After HHP treatment, the wine's color shifted toward light green and yellow. The contents of gallic acid, rutin, genistein, and ferulic acid increased significantly, while those of epicatechin and p-coumaric acid decreased. Under the 400 MPa treatment, the monomeric phenol content was higher than that under the other treatments.
• (2)The total phenolic content did not decrease following HHP treatment. Wine treated at 400 MPa exhibited the highest phenolic content, reaching 924.67 mg GAE/L. A significant decline in total flavonoid content was observed after HHP treatment. Wine treated at 400 MPa demonstrated the highest DPPH radical-scavenging capacity (66.12 %), which significantly surpassed those of the other treatment groups, indicating excellent retention of total phenols and antioxidant capacity. Within the 300–500 MPa pressure range, the ABTS radical-scavenging capacity of the wine slightly increased, while wine treated at 600 MPa exhibited the highest FRAP value of 6.84 mmol Trolox/L, representing a 10.32 % increase compared with that of the control. In most pressure-treated groups, the DPPH radical-scavenging capacity decreased, the ABTS radical-scavenging capacity slightly increased, and the iron ion-reduction capacity improved.
• (3)Following different pressure treatments, the variety of volatile components in the wine significantly increased, and they were primarily classified as alcohols, esters, acids, and aldehydes/ketones. High-pressure treatment significantly reduced the types and concentrations of alcohols while increasing the ester content, promoting esterification reactions and shifting the aroma profile of the wine from alcohol-dominant to ester-dominant.
• (4)Treatment with HHP promoted aging and improved the wine's sensory quality, including enhanced aroma and flavor, improved color, and strong typicity. Kiwifruit wine treated at 400 MPa exhibited a clear, vibrant color; intense aroma; and pure, harmonious taste, and it displayed the distinctive style and characteristics unique to kiwifruit wine.

The results of this study confirm that HHP technology promoted aging in kiwifruit wine, facilitated the formation of esters, and enhanced the wine quality. Kiwifruit wine treated at 400 MPa emerged as the most satisfactory.

CRediT authorship contribution statement

Shuo Zeng: Writing – original draft, Software, Methodology, Data curation. Xinyu Guo: Data curation. Dongsheng Niu: Validation, Investigation. Feng Li: Writing – review & editing.

Ethics statement

All sensory evaluation procedures involving human participants were conducted in accordance with the ethical standards of the Ethics Committee of Xinjiang Agricultural University and with the 1964 Helsinki Declaration and its later amendments. This study was reviewed and approved by the Ethics Committee of Xinjiang Agricultural University. All participants provided written informed consent prior to their participation. They were informed that their participation was voluntary and that they could withdraw from the study at any time without penalty. All collected data were anonymized and used exclusively for research purposes.

Funding sources

This work was funded by the Talent Development Fund of Xinjiang Uygur Autonomous Region's “Tianchi Talent” Introduction Program.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

Data will be made available on request.