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Article

High Humidity Storage Close to Saturation Reduces Kiwifruit Postharvest Rots and Maintains Quality

by
Fabio Buonsenso
1,2,
Simona Prencipe
1,2,
Silvia Valente
1,2,
Giulia Remolif
1,2,
Jean de Barbeyrac
3,
Alberto Sardo
3,4 and
Davide Spadaro
1,2,*
1
Department of Agricultural, Forestry and Food Sciences (DISAFA), University of Turin, Largo Paolo Braccini 2, 10095 Grugliasco, Italy
2
Interdepartmental Centre for the Innovation in the Agro-Environmental Sector—AGROINNOVA, University of Turin, Largo Paolo Braccini 2, 10095 Grugliasco, Italy
3
XEDA International SA, 397 Route National 7, ZAC La Crau, 13670 Saint Andiol, France
4
CEDAX Srl, Via Filippo Guarini, 15, 47121 Forlì, Italy
*
Author to whom correspondence should be addressed.
Horticulturae 2025, 11(8), 883; https://doi.org/10.3390/horticulturae11080883 (registering DOI)
Submission received: 8 July 2025 / Revised: 25 July 2025 / Accepted: 29 July 2025 / Published: 31 July 2025
(This article belongs to the Collection New Advances in Fruit Quality: Pre-harvest Techniques and Postharvest Management)
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Abstract

Postharvest storage of kiwifruit requires the implementation of precise environmental conditions to maintain fruit quality and reduce decay. In this research, conducted over two years, we examined whether the storage conditions, characterized by low temperature (1 ± 1 °C) and ultra-high relative humidity (higher than 99%, close to saturation), generated by the Xedavap® machine from Xeda International, were effective in maintaining the fruit quality and reducing postharvest rots compared to standard storage conditions, characterized by involved low temperature (1 ± 1 °C) and high relative humidity (98%). Kiwifruits preserved under the experimental conditions exhibited a significantly lower rot incidence after 60 days of storage, with the treated fruits showing 4.48% rot compared to 23.03% under the standard conditions in the first year, using inoculated fruits, and 6.30% versus 9.20% in the second year using naturally infected fruits, respectively. After shelf life (second year only), rot incidence remained significantly lower in the treated fruits (12.80%) compared to the control (42.30%). Additionally, quality analyses showed better parameters when using the Xedavap® system over standard methods. The ripening process was effectively slowed down, as indicated by changes in the total soluble solids, firmness, and titratable acidity compared to the control. These results highlight the potential of ultra-high relative humidity conditions to reduce postharvest rot, extend the shelf life, and enhance the marketability of kiwifruit, presenting a promising and innovative solution for the horticultural industry.

Graphical Abstract

1. Introduction

Kiwifruit (Actinidia deliciosa) is renowned for its distinctive flavor and exceptional nutritional profile. Rich in provitamin A carotenoids, vitamin C, polyphenols, minerals (potassium, calcium, magnesium, etc.), dietary fiber, and antioxidants, it represents a refreshing and health-promoting dietary choice [1,2,3]. Kiwifruit production, native to China, has expanded significantly worldwide, with various countries contributing to its growing market. Among these, Italy has emerged as a leading producer, cultivating kiwifruit not only for domestic consumption but also as a key export commodity, thereby supporting economic growth and international trade [4,5]. This success is largely attributed to the favorable conditions of regions, such as Latium, Veneto, and Piedmont, where the combination of fertile soils and temperate climate provides an ideal setting for kiwifruit cultivation [6,7]. Once harvested, kiwifruits are highly sensitive to the storage conditions, which play a decisive role in maintaining their quality and shelf life. Factors such as the temperature, relative humidity, carbon dioxide concentration, and ethylene exposure must be carefully managed to preserve the quality parameters and the organoleptic and nutritional properties of the fruit, minimizing the risk of fungal infections [3,8,9]. Low temperatures are critical for delaying ripening by slowing enzymatic processes, which help maintain the fruit flavor, color, and texture [10]. Proper refrigeration, with optimal storage temperatures ranging between 0 °C and 2 °C, also inhibits the growth of harmful microorganisms [11,12,13]. All kiwifruit genotypes are sensitive to cold injury at temperatures near 0 °C, with the severity of the damage depending on the fruit’s maturity. Inadequate temperature management can result in irreversible damage, such as freezing or accelerated spoilage [14,15,16].
Kiwifruits are typically stored in high-humidity environments, with relative humidity levels between 95% and 98%, helping to prevent water loss from the fruit. In fact, during the early days of storage, water depletion occurs rapidly, making the maintenance of high relative humidity essential to reduce this loss [3].
Storing horticultural products under high relative humidity (RH) conditions, close to saturation, has proven to be an effective strategy for preserving postharvest quality. RH levels between 98% and 100% significantly contribute to reducing weight loss and slowing down deterioration processes, as observed in various fruits and vegetables. High RH plays a crucial role in mitigating water deficit during storage, thereby inhibiting quality degradation [17,18,19].
This environmental condition has also shown beneficial effects in reducing chilling injury, which is commonly observed in cold-sensitive produce like citrus and cucumbers. Moreover, high RH has been associated with enhanced antioxidant activity in certain fruits, further supporting the maintenance of their nutritional and sensory attributes. These findings highlight the importance of relative humidity as a key storage parameter, emphasizing the need for precise microclimatic control to extend the shelf life and ensure the quality of fresh horticultural products [17,18,19].
Slowing down the ripening process and, consequently, extending the shelf life of fruits, can be also achieved by regulating the oxygen and carbon dioxide levels, as occurs during controlled atmosphere (CA) storage [20]. Kiwifruits are usually stored in an atmosphere characterized by approximately 5% CO2 and 2% O2 [21]. Controlled atmosphere (CA) storage, however, typically involves elevated CO2 levels acting synergistically with reduced O2 concentrations to enhance preservation outcomes. In particular, CA conditions consisting of 4.2–4.8% CO2 and 14.0–14.8% O2 have been shown to significantly improve the fruit physiological resilience. These conditions stimulate antioxidant enzyme activity, reduce malondialdehyde (MDA) accumulation, and suppress both ethylene production, a plant hormone that accelerates ripening, and lipoxygenase (LOX) activity [20,22,23,24,25].
Improper storage conditions can lead to the development of fungal pathogens, resulting in significant production losses. The most important postharvest pathogen affecting kiwifruit is Botrytis cinerea, the causal agent of gray mold [26,27]. Symptoms usually appear after 3–4 weeks of cold storage. The skin of the infected fruits usually appears darker than the healthy part and, when cut, infected tissues appear dark green and water-soaked. White to gray mycelium, sclerotia, and conidiophores may develop on infected kiwifruits [15].
Additionally, other pathogens are associated with kiwifruit postharvest rots, including Cadophora luteo-olivacea, Penicillium expansum, Alternaria alternata, Botryosphaeria spp., and Phomopsis spp. [26,27,28,29,30,31].
Therefore, effective storage conditions are essential to control postharvest pathogens and preserving the quality, freshness, and market value of kiwifruits from orchard to consumer [32,33,34,35]. Rather than relying on complex controlled atmosphere systems, the combination of low-temperature storage and ultra-high relative humidity offers a more accessible solution. Storage at 1 ± 1 °C slows enzymatic and microbial activity, delaying ripening and senescence, whereas maintaining relative humidity higher than 99% prevents water loss and preserves fruit turgor, thereby reducing weight loss and physiological disorders. The Xedavap® machine, used for the first time in this study and, to our knowledge, the first example reported in the literature, leverages these principles by generating a high-humidity storage atmosphere close to saturation at low temperature without full CA infrastructure.
Considering this scenario, the aim of the present study was to evaluate the impact of the Xedavap® machine on both postharvest rot incidence and key quality attributes, firmness, total soluble solids, titratable acidity, and weight loss, over extended storage periods. Our goal was to evaluate how ultra-high humidity combined with precise temperature control not only slows decay and preserves fruit quality, but also minimizes food waste, and enhances overall sustainability.

2. Materials and Methods

2.1. Postharvest Storage Conditions

The trials were conducted over two years (2018 and 2019) on kiwifruits cv. Hayward, harvested in Piedmont, northwestern Italy, with a maturity index of around 10.98 and 6.23 for the first and second year, respectively.
The Xedavap® machine, provided by Xeda International (Saint-Andiol, France), was employed for the atmosphere treatment of fruits. This device can modify the atmospheric conditions for storing fruits and vegetables, and it can also function as a cold evaporator [36].
Two storage conditions were tested. The standard conditions (normal atmosphere) involved low temperature (1 ± 1 °C) and high relative humidity (98%). The Xedavap® conditions were characterized by low temperature (1 ± 1 °C), ultra-high relative humidity (higher than 99%), and low CO2 levels (ranging from 0.1 to 0.5%), consistently maintained by the presence of potassium hydroxide dissolved in aqueous phase within the machine. In the Xedavap® machine, recirculated air is continuously brought into counter-current contact with a flow of water over a highly extended surface area. This process ensures that the air exiting the machine is nearly saturated with water vapor, without containing any liquid droplets. To prevent partial freezing of water vapor on the cooled surfaces due to temperature differences, the unit must be paired with an appropriately designed cooling system [22].
In the first year, a trial was conducted on artificially inoculated kiwifruits stored for 60 days under standard conditions to monitor the development of postharvest rots and assess the performance of the Xedavap® system, with the aim of optimizing its parameters for a larger-scale application in the second year of experimentation. Fruit boxes were artificially inoculated with Botrytis cinerea strains BOT1, BOT2, and BOT3 belonging to the University of Turin, plant pathology collection. B. cinerea (three strains in mixture) was artificially inoculated by dipping kiwifruits in a spore suspension (105 spores/mL). Ten percent of fruits were artificially wounded before pathogen inoculation. Four replicates for each storage condition tested were prepared, each consisting of 3 boxes of 115 fruits. Kiwifruits were stored under standard or Xedavap® conditions for 60 days.
In the second year, a larger-scale trial was conducted, storing naturally infected kiwifruits under normal atmosphere both with and without the Xedavap® system, to confirm its efficacy in reducing postharvest rots and preserving fruit quality. Four replicates for each storage condition tested were prepared, each consisting of 6 boxes of 115 fruits. Kiwifruits were stored under standard or Xedavap® conditions for 75 days, followed by an additional 15 days of shelf life at 15 ± 1 °C.
All trials were carried out under standard atmosphere, with kiwifruits harvested, stored, and sampled at the same time points for both years (harvest, storage, and sampling dates are provided in Table 1).

2.2. Evaluation of Rot Incidence and Fungal Identification

In the first-year trial, rot incidence was assessed after 60 days of storage. In the second year, evaluations were performed after 30, 60, and 75 days of storage and after shelf life by counting the number of diseased fruits per replication per treatment.
Representative fruit with rots were used to isolate fungal pathogens. Diseased tissues, washed in 1% sodium hypochlorite for 60 s and rinsed into sterile distilled water, were excised from the margin between the healthy and diseased tissues, cultured on potato dextrose agar (PDA, VWR International, Leuven, Belgium) amended with 25 μg streptomycin (Merck, Darmstadt, Germany) per liter, and incubated at 24 °C. After five days, single colonies were cultured on PDA, and the isolates were identified based on micro- and macro-morphology observations and DNA sequencing. Fungal mycelium grown on PDA was scratched with a sterile blade and used for DNA extraction. Genomic DNA was extracted using the E.Z.N.A. Fungal DNA mini kit (Omega Bio-Tek, Norcross, GA, USA) according to manufacturer instructions. The rDNA internal transcribed spacer (ITS) was amplified and sequenced using primers ITS1/ITS4 and thermocycler protocol as reported by White et al. (1990) [37]. After gel electrophoresis, the amplicons were purified and sequenced in both directions by Macrogen Inc. (Amsterdam, The Netherlands). DNA Baser program was used to clean and to obtain the consensus sequences. BLASTN tool of the National Centre of Biotechnology Information (http://blast.ncbi.nlm.nih.gov/Blast.cgi, accessed on 23 April 2020) was used to identify the isolates.

2.3. Quality Analyses

Fruit quality analyses were performed by measuring the firmness, total soluble solids, and titratable acidity [38,39,40,41] at harvest, after 30 and 60 days of storage in the first year, and at harvest, after 30, 60, and 75 days of storage, and after 15 days of shelf life in the second year. Each parameter was measured in five fruits per box (n = 15) per treatment.
Firmness. The firmness values (N/cm2) were determined through the fruit pressure tester FT 327 (EFFEGI, Alfonsine, Italy) with an 8 mm diameter plunger tip on two sides of the fruits after removing the skin. The capacity of the instrument is equal to 12.7 kg × 100 g and is designed for measurements between 11.77 N and 120.17 N, converted into pressure in N/cm2 by dividing by the application area.
Total soluble solids (TSS). The TSS content was measured using the digital refractometer NR151 refractometer (Rose Scientific Ltd., Edmonton, AB, Canada), by squeezing one drop of juice from each end of the kiwifruits. Values obtained were expressed as a percentage of the TSS content.
Titratable acidity (TA). TA was obtained by titration of 6 g of clear juice, diluted with distilled water (final volume 30 mL), with NaOH 0.1 N up to a final pH value of 8.0, measured using a FP20-Std-Kit FiveEasy Plus pH meter (Mettler Toledo, Milano, Italy). The TA was expressed as a percentage of citric acid, calculated using the following equation:
T A = V N a O H   ×   0.0064   ×   100 6
where 0.0064 indicates the acidity factor of the citric acid and the value 6 represents the grams of juice analyzed.

2.4. Weight Loss

Weight loss was assessed at 60 days of storage during the first year, and at 60 and 75 days of storage and after shelf life during the second year, using the following formula:
%   w e i g h t   l o s s = i n i t i a l   w e i g h t − f i n a l   w e i g h t i n i t i a l   w e i g h t   ×   100

2.5. Sensory Analysis

In the second year of experimentation, eighty trained panelists aged 20–60 years, recruited from faculty staff and students at the University of Turin, performed the sensory analysis. Three samples for each treatment were pooled and presented in coded trays to prevent subjectivity. The evaluation was performed at room temperature (24 °C). The assay evaluated the preference according to sweetness, acidity, firmness (crispness), presence of flavor, and general taste, based on a 5-point hedonic scale (5-point hedonic scale: l—poor, 2—fair, 3—good, 4—very good, 5—excellent) [42].

2.6. Statistical Analyses

Statistical analyses were performed using Student’s t-test to compare treated and control fruits. Statistical significance was judged at the level of p-value < 0.05 or p-value < 0.01. Data were analyzed using IBM SPSS Statistics, Version: 28.0.1.0 (142) (IBM Corp., Armonk, NY, USA).

3. Results

3.1. Evaluation of Rot Incidence

In the trial conducted during the first year, rot incidence was evaluated after 60 days of storage at 1 ± 1 °C (Table 2). At this time point, rot incidence was significantly lower in the treated kiwifruits (4.48%) compared to the control group (23.03%), highlighting the effectiveness of the treatment in reducing postharvest decay.
In the second year, assessments were expanded and carried out at multiple time points, after 30, 60, and 75 days of storage at 1 ± 1 °C, as well as after shelf life at 15 ± 1 °C, by counting the number of diseased fruits per replicate for each treatment (Table 2). After 30 days of storage, no significant differences were found concerning the rot incidence between the control and treated fruits. A significant difference was found after 60 days of storage between the treated and control kiwifruits, with 6.30% and 9.20% gray mold incidence, respectively. In contrast, after 75 days of storage, no significant difference was observed between the control (9.80%) and treated fruits (8.51%).
Finally, over 40% rotten fruit was found in the control after shelf life, whereas fruits stored with Xedavap® showed a significantly lower rot incidence (12.80%).
Isolation from the rotten fruits, performed during the second year, confirmed the high prevalence of Botrytis cinerea, agent of gray rot, isolated from 97.3% of the sampled fruits.

3.2. Quality Analyses

Quality analyses were performed on kiwifruits by measuring the firmness (Table 3), TSS (Table 4), and TA (Table 5) under the storage conditions tested.
In the first trial conducted during the first year, at harvest, the mean firmness was 53.17 N/cm2, the TSS was 10.03%, and the acidity was 1.61%. After 30 days of storage, fruits stored under standard conditions exhibited significantly lower firmness, with an average value of 3.95 N/cm2, compared to 11.34 N/cm2 for kiwifruits stored using the Xedavap® machine. A significantly higher TSS content was also observed in the control kiwifruits, with a mean value of 13.65%, compared to 12.78% in the treated fruits. Similarly, kiwifruits stored using the Xedavap® machine showed significantly higher titratable acidity, averaging 1.50%, compared to 1.38% in the control group. Finally, after 60 days of storage, it was not possible to measure the fruit firmness, as it was lower than the limit of detection of the instrument. At this time point, in the kiwifruits stored using the Xedavap® machine, a non-significant increase in total soluble solids (14.22%) and a significant increase in titratable acidity (1.49%) were observed.
In the second year, at harvest, the mean firmness was 23.67 N/cm2, the TSS was 10.54%, and the acidity was 0.96%.
After 30 days of storage, a lower but not significant firmness was observed in fruits stored under standard conditions, with a mean value of 11.92 N/cm2 compared to 12.72 N/cm2 registered for kiwifruits stored with the Xedavap® machine. A significantly higher TSS content was observed in the control kiwifruits (mean 16.67%) compared to the treated kiwifruits (13.45%). Similarly, significantly higher acidity was observed for the kiwifruits stored with the Xedavap® machine, with a mean value of 0.58%, compared to 0.51% for the control fruits.
After 60 days of storage, a significantly lower firmness was observed in the control fruits with a mean value of 6.32 N/cm2 compared to 9.83 N/cm2 registered for the kiwifruits stored with the Xedavap® machine. Moreover, a significantly higher TSS content was observed in the control kiwifruits (17.95%), compared to the treated kiwifruits (13.99%). The acidity of the kiwifruits was comparable for both the treatment and control (0.57%).
After 75 days of storage, it was not possible to measure the fruit firmness, as it was lower than the limit of detection of the instrument. A significantly lower content of total soluble solids (13.79%) and acidity (0.61%) was observed in the kiwifruits stored with the Xedavap® machine, compared to the control fruits.
After shelf life, no significant differences in the TSS and TA of the fruits were detected and it was not possible to measure the fruit firmness.

3.3. Weight Loss

In the trial conducted during the first year, weight loss was evaluated exclusively after 60 days of storage at 1 ± 1 °C (Table 6). At this time point, no statistically significant difference was observed between the control fruits (10.26%) and those treated with the Xedavap® machine (8.85%).
In the second year, the weight loss (Table 6) of the stored kiwifruits was evaluated at harvest, after 30, 60, and 75 days of storage, and after 15 days of shelf life at 15 ± 1 °C.
After 60 days, no statistically significant differences in weight loss were observed between the control (5.65%) and treated fruits (4.64%). A reduced and significant weight loss was observed in the treated kiwifruits both after 75 days of storage (6.23%) and after shelf life (8.42%) compared to the control fruit values (7.36% and 10.50% after 75 days of storage and after 15 days of shelf life, respectively).

3.4. Sensory Evaluation

In the sensory evaluation (Figure 1), conducted in the second year of the experiment, the panel showed a higher preference for the control kiwifruits (74%). This percentage was lower in males (63% of males preferred control kiwifruits) than in women. People that preferred the treated kiwifruits described them as crispier, whereas people who preferred the control fruits described them as sweeter and tastier.

4. Discussion

The efficacy of an innovative system for modifying the fruit storage conditions, characterized by ultra-high relative humidity higher than 99% and low CO2 levels, was evaluated for the storage of kiwifruits. In the Xedavap® machine, air is recirculated and continuously meets a water flow against the current on a very extended surface. In this way, the air flowing out of the machine is almost saturated in water, but without any water droplet, preventing condensation on the fruit surface, which is crucial for limiting microbial growth and rot development during storage. Unlike high-humidity systems without air circulation, where condensation can rapidly accelerate deterioration, this approach helps preserve the integrity of fruits over time.
The concentration of the different gases in the storage environment is important for prolonging the shelf life of fruits. Among the different gases, oxygen and carbon dioxide play a crucial role in maintaining the correct metabolic activity inside the fruit in a storage atmosphere [43,44]. O2 is essential for maintaining aerobic respiration in fruits and the reduction in the oxygen concentration in the atmosphere plays a key role in slowing or inhibiting metabolism [44], whereas adjusting the CO2 concentration helps minimize respiration, delay senescence, and slows the growth of pathogenic fungi, in particular Botrytis cinerea [26,27]. Although high RH does not directly inhibit B. cinerea, it plays a critical role in preventing infection. Indeed, B. cinerea cannot invade fruits with intact and healthy skin. To overcome this barrier, the fungus secretes specific enzymes that degrade the skin, facilitating its penetration. However, these enzymes become inactivated under conditions of very high RH, thereby reducing the likelihood of infection [22]. During two years of experiments, the postharvest rot incidence was significantly lower in fruits stored under high relative humidity (RH) and low CO2 concentrations generated by the Xedavap® machine than in fruits stored under standard conditions. After 60 days of storage, rot incidence in the treated fruits was 4.48% in the first year using inoculated fruits, and 6.30% in the second year using naturally infected fruits, compared with 23.03% and 9.20% in the control fruits, respectively. After shelf life (second year only), rot incidence was 12.80% in the treated fruits versus 42.30% in the controls.
Relative humidity, a crucial environmental factor during storage [45,46], is defined as the humidity content of the air that corresponds to the ratio between the partial pressure of the water vapor contained in the air and the pressure of the saturated vapor at the same temperature. It is therefore a measure of the ratio between the water vapor content of the air and its maximum capacity to contain it in the same conditions. Typically, during the first days of storage of horticultural products, a rapid water loss is observed. In fact, fruits and vegetables are stored in an atmosphere with RH ranging from 90 to 98%, depending on the commodity [3]. The difficulty in reaching higher values of RH is due to the strong impact of condensation that necessarily occurs in conventional systems, due to various factors such as the cooling of the fruit products, which present a temperature higher than the storage temperature upon entry, or to the exothermic respiration of the fruits stored, which requires storage space for cooling. Furthermore, the structural conditions of the storage chambers such as the temperature difference between the external and internal walls, or the walls being warmer and in contact with external air, can influence the RH. Water loss can be limited by increasing the RH (with a value equal to or greater than 99%), in the storage chambers, and in this context, systems such as the Xedavap® machine, which can control the RH and other environmental parameters described below (including temperature and concentration of carbon dioxide) and, as a consequence, indirectly modulate the level of ethylene, are effective in increasing the shelf life of fruits. Water loss causes not only the reduction in fruit weight, but also the reduction in aesthetic quality (due to the presence of wilting, softening, loss of freshness and juiciness) and nutritional values [47,48,49]. In particular, fresh weight reduction, due to water loss, can accelerate the degradation of ascorbic acid [50]. These characteristics can be preserved by maintaining controlled RH levels. The increase in RH to a value higher than 99% obtained using the Xedavap® machine, characterized by the humidification of the atmosphere with water vapor at room temperature until the air is saturated [51], has a consequent increase in the condensation effect. In the first year, after 60 days of storage at 1 ± 1 °C, the weight loss was 10.26% in the control fruits versus 8.85% in the Xedavap®-treated fruits, a statistically significant difference. Also, during the second year of the experiment, this system effectively minimized weight loss both during storage at 1 ± 1 °C (6.23% after 75 days) and throughout shelf life at 15 ± 1 °C (8.42%), outperforming the control under standard humidity conditions (7.36% after 75 days at 1 ± 1 °C and 10.50% during shelf life at 15 ± 1 °C).
Temperature plays a crucial role during the postharvest storage period, preserving the physicochemical and nutritional properties of kiwifruits, also influencing the decrease in fruit firmness and increasing the percentage of total soluble solids thanks to lower respiration and to modulation of ethylene production [9,14,52]. Higher temperatures, such as 10 °C, lead to faster metabolic activities, which reduce the shelf life, in addition to the variation in firmness (accelerate fruit softening), total soluble solids (TSS), and titratable acidity (TA) [53].
The slowdown in metabolism achieved with the Xedavap® system was clearly demonstrated by both a higher firmness and lower sugar accumulation in the treated kiwifruits compared with the controls. In the first year, after 30 days of storage, the treated fruits displayed a firmness of 11.34 N/cm2 (versus 3.95 N/cm2 in the control) and a TSS of 12.78% (versus 13.64% in the control). In the second year, the treated fruits maintained a firmness of 12.72 N/cm2 after 30 days and 9.83 N/cm2 after 60 days (compared to 11.92 and 6.32 N/cm2 in the controls), whereas their TSS levels remained lower throughout storage, compared to the control. These data confirm that Xedavap® effectively reduced respiration and metabolism, delaying ripening and preserving textural quality. As reported in the literature, the reduction in firmness is caused by a stimulation of the activity of the enzyme pectin esterase, which increases the deesterification of cell wall pectin, as well as the loss of solubilized pectin [54,55]. The enzyme xyloglucan endo-transglycosylase could be involved in the early stages of fruit ripening, acting on the cell wall [56]. The pericarp softens more rapidly than the fruit core [57]. The consistency of the pulp decreases significantly during storage regardless of the harvest time [50].
The TSS content is considered an index of fruit maturity at harvest time and an increase in TSS corresponds to a metabolization of starch into soluble sugars [58]. At harvest, the reference value of the optimal concentration of total soluble solids is equal to 6.2% [59,60]. This value is indicated as the moment at which the fruit switches from starch accumulation to starch degradation, resulting in an increase in TSS [61]. However, fruit can still reach 6.2% without starch degradation, through a prolonged period of slow accumulation of soluble carbohydrates [59]. After ripening, the concentration of TSS should be around a value of 14%. In fruits stored at 1 ± 1 °C for 75 days, TSS was statistically higher for the control fruits than for the treated fruits with Xedavap®, consistent with the values found in the literature [50]. The concentration of TSS in the untreated fruits increased with the decreasing firmness and increasing weight loss. In contrast, fruits in the atmosphere generated by Xedavap®, show an almost unchanged percentage of TSS (yet still above harvest values) along with a higher firmness of the fruit and a decrease in weight loss. In fact, a lower weight loss of the fruits under modified storage conditions, probably due to a lower transpiration rate, was recorded and a decrease in titratable acidity was observed after 30 days of storage.
The TA content of kiwifruit consists mainly of citric acid, which is metabolized by the fruit throughout the ripening process [62,63]. In the first year, fruits stored under Xedavap® atmosphere showed titratable acidity of 1.50% at 30 days and 1.49% at 60 days, statistically higher compared with 1.38% and 1.30%, respectively, in the control. In the second year, kiwifruits treated in the Xedavap® atmosphere were statistically different (0.58 and 0.61%) compared to the control (0.51 and 0.65%) in terms of the percentage of titratable acidity after 30 and after 75 days of storage at 1 ± 1 °C. Fruits stored under standard conditions had a lower percentage of titratable acidity after 75 days of storage compared to the fruits in a modified atmosphere with Xedavap®.
These results indicate that the atmosphere generated by the Xedavap® machine is able to slow down the metabolism, and consequently the ripening, of the fruits in the postharvest period and extend shelf life.
Finally, in the sensory evaluation, the panel showed a higher preference for the control kiwifruits (74%), as they showed a higher degree of maturation. This preference was lower among males, with 63% favoring the control kiwifruits, compared to females. Females, in fact, showed a higher sensitivity to sweet taste compared to men [64,65], which leads them to prefer the control fruits, which have a higher percentage of TSS, over those treated with Xedavap®. People that preferred the treated kiwifruits described them as crispier, whereas people who preferred the untreated fruits described them as sweeter and tastier. These data are in accordance with the results obtained from the analysis of the quality parameters, where the treated kiwifruits had a lower sugar content compared to the control kiwifruits. However, it could be possible that people would prefer kiwifruits treated with Xedavap® after shelf life due to a similar sugar content and acidity, but reduced water loss.

5. Conclusions

In this study, the use of the Xedavap® machine, capable of generating a highly saturated storage atmosphere and controlled CO2 level, created conditions that hindered the growth of fungal pathogens and, as a consequence, minimized the natural development of postharvest rot, leading to a decrease, during the shelf life, in the incidence of rotten fruits (12.80%) compared to the control group (42.03%). Furthermore, these conditions slowed down the ripening of kiwifruits for extended periods (over 60 days), reducing water loss and preserving key quality attributes, such as total soluble solids and titratable acidity. The sensory analyses, conducted through the evaluation of five different parameters by a heterogeneous population of consumers, showed that the atmosphere generated by Xedavap® positively impacted on the kiwifruit flavor, resulting in crunchier and slightly more sour fruits. Therefore, employing the Xedavap® machine to control the atmospheric parameters in packinghouse storage can extend fruit shelf life by preserving their physicochemical characteristics. Future research could explore the integration of Xedavap® atmospheres with compounds such as 1-methylcyclopropene (1-MCP) or essential oils to mitigate the development of postharvest diseases and further delay fruit ripening, and integrate more quality and sensory analysis to better understand the effect of the machine on the physiological, biochemical, and structural effects This makes the ultra-high relative humidity condition a promising alternative for the horticultural industry, providing an effective solution to postharvest challenges and reducing food losses. These findings offer valuable insights for developing sustainable strategies, enhancing overall sustainability, to minimize fruit losses during storage without using full CA infrastructure.

Author Contributions

Conceptualization, D.S., S.P., S.V., A.S., and J.d.B.; methodology, S.P., S.V., and D.S.; validation, D.S., A.S., J.d.B., S.V., S.P., and F.B.; formal analysis, S.P. and S.V.; investigation, S.P. and S.V.; resources, D.S.; data curation, F.B., S.P., S.V., and G.R.; writing—original draft preparation, F.B.; writing—review and editing, S.P., S.V., F.B., and D.S.; visualization, F.B.; supervision, D.S.; project administration, D.S.; funding acquisition, D.S. All authors have read and agreed to the published version of the manuscript.

Funding

The authors wish to thank PRIMA, a program supported by the European Union, for funding the project “StopMedWaste—Innovative Sustainable technologies TO extend the shelf-life of Perishable MEDiterranean fresh fruit, vegetables and aromatic plants and to reduce WASTE” and the Italian Ministry of University and Research for funding the project “KVD-Biome—Unveiling the plant exposome to dissect a multifactorial disease: the kiwifruit vine decline”.

Data Availability Statement

Data is contained within the article.

Acknowledgments

The authors wish to thank Cedax S.r.l. (part of the group of Xeda International) and Xeda International for providing the Xedavap® machine.

Conflicts of Interest

The funders that provided the Xedavap® machine (J.d.B. and A.S., Cedax S.r.l. and Xeda International) had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results. The remaining 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.

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Figure 1. Radar chart illustrating the sensory evaluation results of control and Xedavap®-treated kiwifruits. Sensory parameters—sweetness, acidity, firmness (crispness), presence of flavor, and general taste—were evaluated, with the scores plotted to compare the two treatments.
Figure 1. Radar chart illustrating the sensory evaluation results of control and Xedavap®-treated kiwifruits. Sensory parameters—sweetness, acidity, firmness (crispness), presence of flavor, and general taste—were evaluated, with the scores plotted to compare the two treatments.
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Table 1. Harvest, storage, and sampling dates of kiwifruit for each trial conducted during the two-year study.
Table 1. Harvest, storage, and sampling dates of kiwifruit for each trial conducted during the two-year study.
Time Points
1st Year2nd Year
Fruit harvest8 November 201818 November 2019
Beginning of storage22 November 201818 November 2019
Survey at harvest time-19 November 2019
Survey at 30 days21 December 201818 December 2019
Survey at 60 days21 January 201920 January 2020
Survey at 75 days-5 February 2020
Survey after shelf life-20 February 2020
Table 2. Rot incidence (%) of kiwifruit ‘Hayward’ at harvest and after 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.m. = not measurable; N.s. = not significant.
Table 2. Rot incidence (%) of kiwifruit ‘Hayward’ at harvest and after 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.m. = not measurable; N.s. = not significant.
Rot Incidence (%)
1st Year2nd Year
Time of AnalysisTreatmentMean ± S.D.t-StudentMean ± S.D.t-Student
At harvest-N.m.-N.m.-
30 days of storageControl--0.85 ± 0.30N.s.
Xedavap®-0.63 ± 0.14
60 days of storageControl23.03 ± 2.56**9.20 ± 0.79**
Xedavap®4.48 ± 2.906.30 ± 0.76
75 days of storageControl--9.80 ± 1.20N.s.
Xedavap®-8.51 ± 1.53
After shelf lifeControl--42.03 ± 2.98**
Xedavap®-12.80 ± 4.49
Table 3. Firmness (N/cm2) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Firmness after 75 days of storage and after shelf life was not measured due to instrumental limits. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant; N.m. = not measurable.
Table 3. Firmness (N/cm2) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Firmness after 75 days of storage and after shelf life was not measured due to instrumental limits. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant; N.m. = not measurable.
Firmness (N/cm2)
1st Year2nd Year
Time of AnalysisTreatmentMean ± S.D.t-StudentMean ± S.D.t-Student
At harvest-53.17 ± 0.66-23.67 ± 6.58-
30 days of storageControl3.95 ± 0.29**11.92 ± 0.21N.s.
Xedavap®11.34 ± 0.4012.72 ± 1.90
60 days of storageControlN.m.N.m.6.32 ± 0.16*
Xedavap®N.m.9.83 ± 3.15
75 days of storageControl--N.m.N.m.
Xedavap®-N.m.
After shelf lifeControl--N.m.N.m.
Xedavap®-N.m.
Table 4. TSS (%) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant.
Table 4. TSS (%) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant.
TSS (%)
1st Year2nd Year
Time of AnalysisTreatmentMean ± S.D.t-StudentMean ± S.D.t-Student
At harvest-10.03 ± 0.63-10.54 ± 1.09-
30 days of storageControl13.65 ± 0.60*16.67 ± 0.05**
Xedavap®12.78 ± 0.6113.45 ± 0.41
60 days of storageControl14.39 ± 0.62N.s.17.95 ± 0.42**
Xedavap®14.22 ± 0.6313.99 ± 0.32
75 days of storageControl--17.99 ± 1.04**
Xedavap®-13.79 ± 1.10
After shelf lifeControl--15.17 ± 2.79N.s.
Xedavap®-14.84 ± 1.04
Table 5. TA (%) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Student’s t-test was used to compare the treatments. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant.
Table 5. TA (%) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30 and 60 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Student’s t-test was used to compare the treatments. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant.
TA (%)
1st Year2nd Year
Time of AnalysisTreatmentMean ± S.D.t-StudentMean ± S.D.t-Student
At harvest-1.61 ± 0.19-0.96 ± 0.16-
30 days of storageControl1.38 ± 0.10**0.51 ± 0.03*
Xedavap®1.50 ± 0.610.58 ± 0.02
60 days of storageControl1.30 ± 0.10**0.57 ± 0.09N.s.
Xedavap®1.49 ± 0.040.57 ± 0.05
75 days of storageControl--0.65 ± 0.03*
Xedavap®-0.61 ± 0.04
After shelf lifeControl--0.73 ± 0.04N.s.
Xedavap®-0.72 ± 0.09
Table 6. Weight loss (%) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30, 60 and 75 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant; N.m. = not measurable.
Table 6. Weight loss (%) of kiwifruit ‘Hayward’ at harvest, after 30 and 60 days of storage at 1 ± 1 °C in the first-year experiment, and at harvest, after 30, 60 and 75 days of storage at 1 ± 1 °C, and after 15 days of shelf life at 15 ± 1 °C in the second-year experiment. Atmospheric parameters: 98% RH for control, and ultra-high relative humidity (greater than 99%), and low CO2 levels for treatment with Xedavap® machine. Each value is the mean of n = 5 fruits. Asterisks indicate the level of statistical significance (* p < 0.05; ** p < 0.01) in comparison with the control by Student’s t-test. S.D. = standard deviation; N.s. = not significant; N.m. = not measurable.
Weight Loss (%)
1st Year2nd Year
Time of AnalysisTreatmentMean ± S.D.t-StudentMean ± S.D.t-Student
At harvest-N.m.-N.m.-
30 days of storageControlN.m.-N.m.-
Xedavap®N.m.N.m.
60 days of storageControl10.26 ± 0.74N.s.5.65 ± 0.14N.s.
Xedavap®8.85 ± 0.614.64 ± 1.13
75 days of storageControl--7.36 ± 0.16*
Xedavap®-6.23 ± 1.16
After shelf lifeControl--10.50 ± 0.54**
Xedavap®-8.42 ± 1.19
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MDPI and ACS Style

Buonsenso, F.; Prencipe, S.; Valente, S.; Remolif, G.; de Barbeyrac, J.; Sardo, A.; Spadaro, D. High Humidity Storage Close to Saturation Reduces Kiwifruit Postharvest Rots and Maintains Quality. Horticulturae 2025, 11, 883. https://doi.org/10.3390/horticulturae11080883

AMA Style

Buonsenso F, Prencipe S, Valente S, Remolif G, de Barbeyrac J, Sardo A, Spadaro D. High Humidity Storage Close to Saturation Reduces Kiwifruit Postharvest Rots and Maintains Quality. Horticulturae. 2025; 11(8):883. https://doi.org/10.3390/horticulturae11080883

Chicago/Turabian Style

Buonsenso, Fabio, Simona Prencipe, Silvia Valente, Giulia Remolif, Jean de Barbeyrac, Alberto Sardo, and Davide Spadaro. 2025. "High Humidity Storage Close to Saturation Reduces Kiwifruit Postharvest Rots and Maintains Quality" Horticulturae 11, no. 8: 883. https://doi.org/10.3390/horticulturae11080883

APA Style

Buonsenso, F., Prencipe, S., Valente, S., Remolif, G., de Barbeyrac, J., Sardo, A., & Spadaro, D. (2025). High Humidity Storage Close to Saturation Reduces Kiwifruit Postharvest Rots and Maintains Quality. Horticulturae, 11(8), 883. https://doi.org/10.3390/horticulturae11080883

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