Interannual Variability in Apricot Quality: Role of Calcium and Postharvest Treatments During Cold Storage and Shelf Life

Abstract

Extending the postharvest life of apricots (Prunus armeniaca L.) while maintaining their quality is a significant challenge due to their perishability, climacteric ripening, and susceptibility to mechanical injury. This study evaluated the effects of preharvest calcium (Ca) application and postharvest treatments, including modified-atmosphere packaging (MAP) and 1-methylcyclopropene (1-MCP), on apricot quality during storage, carried out in two production years (2016 and 2017) under contrasting climatic conditions. Apricot fruits, cv. ‘Buda’, were treated with Ca before harvest and subjected to MAP or 1-MCP postharvest treatment. Quality parameters, including firmness, color, total soluble solids (TSS), titratable acidity (TA), carotenoids, phenols, respiration rate, and sensory attributes, were analyzed over 15 days of cold storage followed by 3 days of shelf life (15 + 3). The growing season significantly influenced all measured parameters. Fruits harvested in 2017 had double the initial firmness compared to those from 2016 (50.03 N vs. 24.3 N), with higher sweetness and acidity scores. Ca treatment effectively reduced firmness loss by 30% in 2016, particularly beneficial under that year’s wetter conditions, but showed limited impact in the drier 2017 season. MAP successfully delayed ripening and maintained higher acidity levels across both years compared to controls. While 1-MCP treatment preserved fruit firmness effectively, it reduced sweetness perception by 37–59% and limited aroma development, with effects most pronounced in 2017. Sensory evaluation revealed no negative impacts of the applied treatments on overall taste acceptance, with Ca-treated fruits scoring significantly higher for sweetness than controls. The combination of preharvest Ca and postharvest treatments showed potential for extending apricots’ shelf life, but their efficacy was highly dependent on yearly climatic variability. These findings demonstrate that treatment effectiveness varies substantially between years, with Ca applications providing greater benefits in wet years, while 1-MCP and MAP showed more a consistent performance across varying climatic conditions. Therefore, customized and specifically tailored pre- and postharvest protocols are greatly needed to maintain the fruit quality and achieve targeted storage outcomes.

1. Introduction

Apricot (Prunus armeniaca L.) fruits have limited storage potential due to their perishable nature. The global fresh apricot market is expected to grow from USD 16.70 billion in 2025 to USD 20.96 billion by 2030, with a CAGR of 4.65% during this period (2025–2030). This growth is largely based on rising consumer awareness of the fruit’s nutritional value and its versatile uses in food processing, according to Mordor Intelligence [1].

Therefore, extending their market availability remains an important challenge, complicated by both production and postharvest factors [2]. During production, moderate continental climates present challenges such as late spring frosts, early flowering, and apoplexy. Apricot fruits undergo climacteric ripening and are susceptible to mechanical injuries [3,4], making them more suitable for processing than long-term fresh storage [2,5]. At the same time, fruit processing leads to irreversible loss of nutritionally valuable components. Fresh apricots are rich in bioactive compounds, vitamins, fibers, and minerals [6]. Thus, it is highly important to develop optimal methods that not only preserve the overall quality and nutritional value of these fruits but also ensure that they meet consumers’ preferences.

Selection of cultivars adapted to external conditions accompanied by selection and application of appropriate preharvest treatments are just some of the practices used in intensive apricot production. One of these treatments is the application of calcium (Ca(NO₃)₂)) before harvest [7,8,9]. Ca affects preservation of the membrane and cell walls and delays the ripening process [10,11,12]. The application of 2% (Ca(NO₃)₂) before harvest made it possible to store ‘Canino’ apricots for 30 days at 0 °C, and to maintain fruit firmness and the content of total acids during storage [9]. Improved firmness was also recorded in the Ca-treated peach fruits [13]. The application of Wuxal^® Calcium delays the ripening of plum fruits and increases the contents of total acids and soluble solids after harvest [14].

The main challenge during storage of apricot fruits is rapid ripening and loss of fruit firmness [3,4]. During 14 days of cold storage (at 4 °C), apricot fruit firmness decreased by 25% [5]. Modified-atmosphere packaging (MAP) addresses this challenge by creating controlled atmospheres that slow the ripening process. MAP treatment reduced firmness loss in apricot cultivar ‘Buda’ during 15 days of cold storage [15], demonstrating its effectiveness in maintaining fruit quality. Moreover, apricot fruit firmness was preserved with the combination of Wuxal^® Calcium and MAP treatment in all four tested apricot cultivars [15]. MAP also reduced the intensity of respiration and loss of total phenol content [16,17]. Since respiration and ethylene production continue after harvest and during storage, the use of ethylene inhibitors, like 1-methylcyclopropene (1-MCP), becomes essential for effectively controlling the ripening processes of climacteric fruits, such as apricots [18,19]. 1-MCP delays the ripening process and extends the storage period of apricots, peaches, and plums [20,21,22,23]. According to some reports, the application of 1-MCP had no effect on the skin color of apricots and peaches [21,24]. The variable color responses to 1-MCP treatment across studies may reflect cultivar-specific differences and varying storage conditions [20,24], highlighting the need for cultivar-specific evaluation of treatment effects. On the other hand, the greatest color difference in apricot cultivar ‘Buda’ after storage was observed following 1-MCP treatment. These contradictory findings regarding 1-MCP’s effects on color development suggest that responses may be cultivar-dependent and influenced by storage conditions, emphasizing the importance of cultivar-specific treatment optimization. On the other hand, the combination of Ca preharvest treatment and postharvest 1-MCP did not show an improvement in fruit firmness compared to fruits treated only with 1-MCP [15].

Apricots exhibit a unique ripening physiology that is highly sensitive to temperature conditions. At low temperatures, such as those typical of cold storage (around 0–4 °C), apricots maintain firmness and do not undergo significant ripening due to the suppression of metabolic activity and ethylene production [4]. However, upon exposure to higher temperatures, such as those encountered during shelf life at market conditions (approximately 20 °C), rapid softening occurs alongside the release of aroma volatiles and the conversion of starch into soluble sugars, which enhances sweetness [3]. These changes are attributed to the climacteric nature of apricots, where ethylene-triggered ripening processes accelerate under warmer conditions [20]. The combination of cold storage followed by a simulated shelf-life period is therefore critical for evaluating postharvest quality, as it mimics real-world handling and consumption scenarios. During cold storage alone, changes in fruit quality parameters such as firmness, color, and bioactive compounds are less pronounced, whereas significant transformations occur during the subsequent shelf-life phase, underscoring the importance of including this period in experimental designs [5].

Many studies have shown that besides the cultivar and orchard age, weather conditions are also important factors affecting the physicochemical properties of fruit. One of the major challenges in research is that multi-year data is often presented as an average, which can obscure significant year-to-year differences that may provide valuable insights. Khasawneh et al. [25] found that photosynthesis values of apricot were about 30% higher and fruit yield doubled in the second year versus the first year of research. According to Miodragović et al. [26], a four-year study of four apricot cultivars revealed differences in yield between years. Despite the recognized importance of environmental variability, systematic multi-year evaluations of pre- and postharvest treatment efficacy in apricots remain scarce, limiting our understanding of how climatic conditions influence fruit responses to these treatments.

The present study aimed to assess the effects of preharvest Ca treatment, postharvest (MAP) and 1-MCP treatments, as well as their combinations on the storage outcomes of apricots across two distinctly different growing seasons. Special attention was given to understanding how climatic variability between the years influenced the efficacy of specific pre- and postharvest treatments in maintaining fruit quality during cold storage and subsequent shelf life. This knowledge gap has significant commercial implications, as current postharvest recommendations typically provide universal protocols without accounting for seasonal variability, potentially leading to inconsistent results and economic losses.

2. Materials and Methods

2.1. Apricot Production and Preharvest and Postharvest Treatments

Apricot (Prunus armeniaca L.) fruits of cultivar ‘Buda’ were harvested from the trees grown at the Experimental Orchard of the Faculty of Agriculture, Novi Sad, Serbia (45°33′82″ N and 19°84′45″ E, 86 m a.s.l.). Cultivar ‘Buda’ was grafted on Myrobalan seedling (P. cerasifera Ehrh.) rootstock with blackthorn (Prunus spinosa L.) as an interstock. ‘Buda’ is a cultivar with large fruits, which is symmetrical, round in shape, and light orange with a slightly pronounced orange–red color of medium intensity [27].

The orchard was five years old with a planting distance of 4 m × 2 m (1250 trees ha⁻¹), covered with an anti-hail net, had a drip irrigation system, and was subject to all standard agronomic practices. Wuxal^® Calcium (0.1%) (Agrosava, Šimanovci, Serbia) was applied as a preharvest foliar treatment at 0.1% dilution (1 L product per 1000 L water per hectare) in three repetitions at 2, 4, and 6 weeks after flowering [28,29,30]. Besides 15% of CaNO₃ and 10% of N, Wuxal^® Calcium also contains 2% of Mg and the following microelements: B, Cu, Fe, Mn, Mo. The experimental design employed a completely randomized layout in the field, with six single trees randomly selected per treatment to minimize spatial effects and ensure representative sampling across the orchard. Fruits were harvested on the same day from six trees, ensuring that all samples were free from external damage, and selected based on a range of I_AD index values (0.4–0.8). The I_AD index (Index of Absorbance Difference), measured using a DA meter (T.R. Turoni Srl, Forlì, Italy), is a non-destructive parameter for evaluating fruit maturity based on the chlorophyll content, calculated from absorbance differences at 670 and 720 nm. Lower I_AD values indicate advanced ripeness, making it a reliable tool for maturity assessment in stone fruits [31,32]. Following harvest, all fruits meeting the I_AD index criteria (0.4–0.8) were pooled and then randomly allocated to experimental treatment combinations, to ensure an unbiased distribution across all preharvest and postharvest treatment groups.

The average monthly temperatures during both years of this study did not significantly deviate from the long-term average. In 2016, the exceptions were observed in February, the month before the start of vegetation, with above-average temperatures, and in April, with slightly higher temperatures compared to the long-term average. The vegetation period in 2016 had above-average precipitation in all months (March, April, May, and June), with June being particularly notable, recording 141 mm of rainfall. In 2017, after a rainy April and May, a dry June and July followed, with average monthly temperatures 2 °C higher than the average.

Apricots were analyzed at room temperature, both at harvest and after postharvest treatments. The experimental design included six treatment combinations: three groups from untreated trees (control + control, control + MAP, control + 1-MCP) and three groups from Ca-treated trees (Ca + control, Ca + MAP, Ca + 1-MCP) per year, where the first term indicates preharvest treatment and the second indicates postharvest treatment. For each treatment combination, approximately 40 kg of fruits was selected for uniformity in size, color, maturity stage, and absence of visible mechanical damage, then systematically randomized across wooden crates (50 cm × 30 cm × 8 cm, 8 crates per treatment) to ensure unbiased sampling for postharvest treatments [31]. MAP or 1-MCP (SmartFreshTM) was applied to samples of previously chilled fruits, respectively. MAP treatment was achieved using Xtend^® bags (StePac, Tefen, Israel) with micro-perforations designed to regulate O₂ and CO₂ levels according to fruit respiration rates. The final CO₂ concentration in the bags ranged from 6.5% to 7.0% during storage. Prior to quality analyses, MAP-treated fruits were equilibrated at room temperature for 12 h. 1-MCP was applied using SmartFresh™ 0.14 Technology (AgroFresh Solutions Inc., Philadelphia, PA, USA), containing 0.14% active 1-methylcyclopropene. Fruits were treated in hermetically sealed plastic containers for 24 h at the storage temperature (1 ± 1 °C) with continuous air circulation. Following treatment, fruits were stored under a normal atmosphere at 1 ± 1 °C and 80 ± 10% relative humidity. All fruits were then subjected to 15 days of cold storage at 1 ± 1 °C and 80 ± 10% relative humidity, followed by exposure to shelf-life conditions (20 ± 2 °C) for 3 days [32,33].

All orchard management practices (irrigation, fertilization, pest control) followed standard good agricultural practices, with applications adjusted to seasonal conditions as per normal farm protocols. However, experimental treatments (preharvest Ca applications and postharvest MAP/1-MCP protocols) were standardized across both years using identical timing, concentrations, and application methods. This approach ensured that observed differences in treatment efficacy between years resulted from genuine climate–treatment interactions rather than variations in experimental protocols. The contrasting climatic conditions (wet 2016 vs. dry 2017) thus served as natural experimental variables for evaluating treatment effectiveness under different environmental scenarios.

2.2. Texture and Fruit Color

Flesh firmness (N) was measured on 10 randomly selected apricots. A small circle of fruit skin was removed with a sharp blade and the test performed on the opposite sides of each fruit. The penetration test was performed using TA. We utilized an XT Plus Texture Analyzer (Stable Micro Systems, Godalming, UK) with a stainless-steel rounded cylinder probe of 8 mm diameter. Measurements were conducted at a penetration depth of 3 mm, probe speed of 10 mm/s, and trigger force of 25 g [31].

Fruit color parameters in L*a*b* color space (lightness L*, red tone intensity a*, yellow tone intensity b*, hue°, and chromaticity C*) were measured on 10 randomly selected apricots, with two measurements on the opposite sides, by a CR-400 Chroma Meter (Konica Minolta, Osaka, Japan). Color difference (ΔE) was calculated according to the following formula:

$$∆E_{ab}^{*}=\sqrt{{\left(L_2^{*}\right.\left.{-L}_1^{*}\right)}^2+{{\left(a_2^{*}\right.\left.-a_1^{*}\right)}^2+\left(b_2^{*}\right.-\left.b_1^{*}\right)}^2}$$

2.3. Respiration Rate

The respiration rate was determined in triplicate, with approximately 250–300 g of fruits placed in a 770 mL container, hermetically sealed with multilayer foil. CO₂ measurement was performed by direct puncture of the sealed foil with a sampling needle of OXYBABY^® 6.0 (WIT-Gasetechnik GmbH & Co KG T, Witten, Germany) [32,33]. The analysis was performed at 24 °C (±2 °C), both after harvest (0 days) and following cold storage (15 days), on the third day of shelf life (15 + 3 days).

Production of CO₂ (μL g⁻¹ h⁻¹) was obtained through the difference in CO₂ concentration before sealing the dish and after 4 h. The calculation incorporated the weight of the fruit in the container, its volume, the volume of the container, and the exact time from sealing the container until sampling was performed.

2.4. Chemical Analysis

Chemical analyses were performed in each sampling period (0 days and 15 + 3 days) by preparing the composite sample from quarters of 10 randomly selected fruits, which were homogenized and immediately frozen in dry ice for subsequent analysis. All measurements were carried out in triplicate.

Total soluble solids (TSS; %) were measured by the digital refractometer ATR-ST plus (Schmidt + Haensch, Berlin, Germany). Titratable acidity (TA; g malic acid/100 g) was analyzed on 3 g of sample dissolved in 30 mL of deionized water. Following the homogenization and centrifugation (Centrifuge 5804R, Ependorf, Hamburg, Germany) at 13,776 g for 5 min, 10 mL of supernatant was used for titration with 0.1 M NaOH [31,32].

The carotenoid content (mg/100 g FW) was determined according to Andreu-Coll et al. [34], and the phenol content (mg/100 g) according to the Folin–Ciocalteu method [35].

2.5. Sensory Evaluation

The sensory evaluation of apricot fruits after 15 ± 3 days of storage was carried out by a trained panel of 10 assessors (5 women and 5 men, aged 20–60 years), following the methodology of Milović et al. and Prasad et al. [33,36]. Panelists were qualified to perform both qualitative and quantitative assessments of horticultural products and underwent multiple practice sessions to standardize scoring criteria and terminology. During evaluation, six attributes (sweetness, acidity, flavor, off-flavor, crispiness, and gumminess) were assessed on fruit slices using a continuous 0–100 scale in individual booths under controlled conditions (20 ± 1 °C, neutral white lighting). Samples were coded with randomly assigned three-digit numbers, and assessors were blinded to treatment identity and evaluation year. Each sample was assessed in duplicate, with palate cleansers (water and plain crackers) provided between evaluations to minimize carryover effects. Panel consistency across assessors and years was confirmed by analysis of variance components and monitoring of panelist × sample interactions, demonstrating a reliable and reproducible performance.

2.6. Statistical Evaluation

Obtained data were processed by four-way factorial ANOVA (year × preharvest treatment × postharvest treatment × storage time). Statistical significance of differences between means was tested by Duncan’s multiple range test (p < 0.05). Principal component analysis (PCA) was performed on standardized data to identify relationships between variables and treatment effects. Components with eigenvalues > 1.0 were retained. All analyses were conducted using Statistica software version 14.0 (TIBCO Software Inc., Palo Alto, CA, USA).

3. Results and Discussion

The overall quality and postharvest behavior of apricot cultivar ‘Buda’ were examined through the analysis of the most significant physicochemical parameters, including fruit color, firmness, content of bioactive compounds, biochemical composition, respiration rate, and sensory attributes, to assess the effects of applied pre- and postharvest treatments across two growing seasons (2016 and 2017).

The results demonstrate that climatic conditions during the growing season were the primary determinant of both fruit quality and treatment efficacy, with year effects consistently outweighing all other factors across measured parameters. Detailed observations are given in the following sections, offering comprehensive insights into the complex relationship between climate, preharvest treatments, and postharvest handling.

3.1. Physicochemical Quality Parameters

Fruit color was influenced by climactic conditions, as differences in lightness (L*) and chromaticity (C*) were observed between the two years (

Table 1. The color of apricot fruits cv. ‘Buda’ in respect to preharvest treatment with Ca and postharvest treatments with MAP and 1-MCP measured at harvest and after 15 days of cold storage followed by 3 days of shelf life (15 + 3).

Preharvest Treatment	Postharvest Treatment	Storage (Days)	L*	C*	hue°	∆E
2016
control	control	0	63.81 a	32.95 f	77.83 ab	3.88
		15 + 3	55.40 f	37.90 b	67.88 efg
	MAP	0	63.53 a	34.25 ef	78.45 ab	3.57
		15 + 3	56.52 def	38.11 b	69.05 efg
	1-MCP	0	62.96 a	35.78 cde	77.0 bc	4.22
		15 + 3	55.46 f	40.89 a	66.61 efg
Ca treatment	control	0	63.96 a	35.77 cde	83.93 a	4.45
		15 + 3	57.06 cdef	37.68 b	71.57 cde
	MAP	0	63.54 a	35.30 cde	81.77 ab	4.56
		15 + 3	56.49 def	33.39 f	68.53 efg
	1-MCP	0	62.49 a	35.49 cde	77.74 ab	4.18
		15 + 3	56.14 ef	39.77 a	66.99 efg
2017
control	control	0	59.13 bc	35.19 de	82.14 ab	4.12
		15 + 3	58.79 bcd	35.64 cde	70.67 def
	MAP	0	56.90 cdef	39.64 a	75.80 bcd	1.76
		15 + 3	57.10 cdef	34.09 ef	67.60 efg
	1-MCP	0	57.00 cdef	40.36 a	79.30 ab	5.33
		15 + 3	57.14 cdef	37.07 bc	64.53 fg
Ca treatment	control	0	59.91 b	35.58 cde	80.34 ab	4.24
		15 + 3	58.49 bcde	36.68 bcd	68.51 efg
	MAP	0	56.80 cdef	40.42 a	77.88 abc	3.59
		15 + 3	58.03 bcde	35.85 cde	67.30 efg
	1-MCP	0	56.72 def	40.87 a	76.03 bcd	4.71
		15 + 3	56.18 ef	36.79 bcd	62.65 g
Statistical significance
Year (Y)			**	**	ns
Ca treatment (Ca)			ns	ns	ns
Postharvest treatments (PT)			**	**	**
Storage (S)			**	ns	**
Y × Ca			ns	*	*
Y × PT			*	**	ns
Ca × PT			ns	*	ns
Y × S			**	**	ns
Ca × S			ns	**	ns
PT × S			ns	**	ns
Y × Ca × PT			ns	**	ns
Y × Ca × S			ns	**	ns
Y × PT × S			ns	**	ns
Ca × PT × S			ns	ns	ns
Y × Ca × PT × S			ns	**	ns

L*—lightness, C*—chroma, H°—hue angle, ∆E—color difference, ^a–g—numbers designated by the same letter are not significantly different (p > 0.05); main factors and their interactions are presented, and their significance is annotated as follows: ns—non-significant, *—statistically significant at p < 0.05; **—statistically significant at 0.01.

). In 2016, the L* values for various treatments ranged from approximately 62.49 to 63.96 at the beginning of storage and decreased notably after cold storage (15 + 3), indicating a loss of fruit lightness. Conversely, the 2017 data showed initial L* values between approximately 56.72 and 59.91, with a less pronounced decrease after the same storage period. At harvest, C* values in 2016 ranged from 32.95 to 35.78, which generally increased after storage. In contrast, 2017 apricots exhibited higher C* values at harvest (35.19 to 40.87), with post storage trends being more variable. This suggests the impact of the growing season on the color of apricot fruits, with those from 2016 having higher L* and lower C* than those from 2017. In 2016, ΔE values after cold storage ranged from approximately 3.57 to 4.56, suggesting a moderate change in color that may be noticeable to consumers. In contrast, in apricots from 2017, ΔE values exhibited a broader range (1.76 and 5.33), reflecting variations in color retention and shifts in visual quality. The application of preharvest Ca treatment did not affect fruit color, confirming the findings of Crisosto et al.’s [7] foliar application of Ca, which had no impact on color change in three peach cultivars. In 2017, fruits subjected to postharvest treatments had slightly lower hue◦ values after the cold storage and developed a more intense red tone versus the respective control, which agrees with Milović et al. [15]. In apricots subjected to the combination of Ca application and postharvest treatments, we recorded lower L* values after cold storage compared to the control, indicating a darker color of the skin. Significant changes in C* were not detected during storage, which agrees with Fan et al. [20].

Fruit firmness is one of the main quality-related determinants and plays a key role in shaping consumer preference [34,37]. According to the results, apricots from 2017 had greater firmness than those from 2016 at harvest (

Table 2. Quality parameters: firmness, phenols, carotenoids, total soluble solids (TSS), total acids (TA), ripening index (TSS/TA) of apricot fruits cv. ‘Buda’ in respect to preharvest treatment with Ca and postharvest treatments with MAP and 1-MCP, evaluated at harvest and following 15 days of cold storage followed by 3 days of shelf life (15 + 3).

Preharvest Treatment	Postharvest Treatment	Storage (Days)	Firmness (N)	Phenols (mg/100 g)	Carotenoids (mg/100 g FW)	TSS (%)	TA (g Malic Acid/ 100 g)	Ripening Index (TSS/TA) (%)
2016
control	control	0	24.3 c	47.0 a	0.85 h	8.64 j	1.78 b	79 cde
		15 + 3	2.93 h	45.0 b	2.00 a	11.14 d	1.47 b	87 a
	MAP	15 + 3	7.70 fg	45.2 b	1.69 c	9.82 i	1.44 b	85 a
	1-MCP	15 + 3	6.76 fgh	39.9 d	1.80 b	10.90 e	1.53 b	86 a
Ca treatment	control	0	19.20 d	46.1 ab	1.06 fg	10.58 f	1.50 b	86 a
		15 + 3	8.06 fg	39.7 d	1.89 ab	10.12 h	1.55 b	85 a
	MAP	15 + 3	5.03 gh	32.9 fg	1.39 e	10.20 gh	1.51 b	85 a
	1-MCP	15 + 3	5.08 gh	39.9 d	1.51 d	11.3 c	1.66 b	85 a
2017
control	control	0	50.03 a	39.4 d	1.16 fg	9.90 i	2.38 a	76 e
		15 + 3	14.54 e	37.0 e	1.12 fg	9.48 j	1.48 b	84.5 ab
	MAP	15 + 3	11.33 ef	34.2 f	1.15 fg	10.55 f	1.43 b	86.5 a
	1-MCP	15 + 3	8.14 fg	42.7 c	1.15 fg	12.09 b	1.41 b	88.5 a
Ca treatment	control	0	36.9 b	40.6 d	1.04 g	10.27 g	1.31 b	87 a
		15 + 3	4.62 gh	32.7 fg	1.18 f	11.0 e	1.55 b	86 a
	MAP	15 + 3	13.20 e	34.1 f	1.16 fg	10.51 f	1.69 b	84 abc
	1-MCP	15 + 3	5.36 gh	36.1 e	1.11 gf	13.04 a	1.71 b	87 a
Statistical significance			**	**	**	**	ns	ns
Year (Y)			**	**	*	**	**	**
Ca treatment (Ca)			ns	**	**	**	ns	ns
Postharvest treatments (PT)			**	**	**	**	**	**
Storage (S)			**	**	ns	**	*	**
Y × Ca			ns	**	**	**	ns	ns
Y × PT			ns	ns	ns	**	ns	ns
Ca × PT			**	**	**	ns	ns	ns
Y × S			**	**	**	**	**	ns
Ca × S			ns	**	**	**	ns	ns
PT × S			**	**	ns	**	ns	ns
Y × Ca × PT			ns	**	*	**	**	ns
Y × Ca × S			ns	**	*	**	ns	ns
Y × PT × S			ns	ns	ns	**	ns	ns
Ca × PT × S			**	**	ns	**	ns	ns
Y × Ca × PT × S

^a–j—Numbers designated by the same letter are not significantly different (p > 0.05). Main factors and their interactions are presented, and their significance is annotated as follows: ns—non-significant, *—statistically significant at 0.05; **—statistically significant at p < 0.01.

). However, Ca-treated fruits in 2016 exhibited better firmness retention (58% loss vs. 88% in controls) after storage, likely due to the higher moisture content and larger fruit size, which indicated the role of Ca in cell wall stabilization [7]. The smaller, firmer fruits from 2017 showed less benefit from Ca, as drought conditions naturally reduced water loss and softening.

3.2. Biochemical Composition

Titratable acidity (TA) serves as an indicator of fruit ripeness. Despite differences in TA between the growing seasons, the year as a factor was not significant (Table 2). At harvest, Ca-treated apricots had lower TA compared to the control, in both growing seasons. After cold storage, Ca contributed to retaining TA in treated apricots versus the control, supporting its application as a method for fruit quality preservation during storage.

Total soluble solids (TSS) are another parameter of fruit quality that significantly affects the taste of the fruit [35]. Ca treatment increased the TSS content compared to untreated apricots in both examined years (Table 2). This corresponds with the higher sweetness scores of apricots in the sensory evaluation (

Table 3. Sensory attributes of apricot fruits cv. ‘Buda’ in respect to preharvest treatment with Ca and postharvest treatments: MAP or 1-MCP after 15 + 3 days of storage.

Preharvest Treatment	Postharvest Treatment	Sweetness	Acidity	Aroma	Foreign Taste	Crispiness	Gumminess
2016
control	control	27 def	28 def	39 ab	0 a	6.5 c	24.5 ab
	MAP	28 def	40 bcde	29.5 bc	2.5 a	18.5 c	22.5 ab
	1-MCP	24 ef	41 bcde	28 bc	2.5 a	20 c	34.5 ab
Ca treatment	control	45 abc	16 f	52 a	0 a	7 c	18.5 ab
	MAP	38.5 abcde	24.5 cde	51 a	5 a	9.5 c	21 ab
	1-MCP	47.5 ab	21 ef	55 a	0 a	10 c	24 ab
2017
control	control	35 bcdef	59 ab	19 c	0 a	64 ab	16.5 b
	MAP	30 cdef	46 bcd	32 bc	10 a	49 b	34 ab
	1-MCP	22 f	56 b	17 c	8 a	56 b	44.5 a
Ca treatment	control	54 a	31 cdef	38.5 ab	0 a	18 c	13 b
	MAP	42.5 abcd	53 bc	19 c	2 a	50 b	26 b
	1-MCP	21 f	77.5 a	13 c	12 a	75 a	36 ab
Statistical significance
Year (Y)		**	**	**	ns	**	ns
Ca treatment (Ca)		**	ns	**	ns	*	ns
Postharvest treatments (PT)		**	*	ns	ns	**	*
Y × Ca		ns	ns	**	ns	ns	ns
Y × PT		**	ns	ns	ns	ns	ns
Ca × PT		ns	ns	ns	ns	**	ns
Y × Ca × PT		ns	*	*	ns	**	ns

^a–f—Numbers designated by the same letter are not significantly different (p > 0.05). Main factors and their interactions are presented, and their significance is annotated as follows: ns—non-significant, *—statistically significant at 0.05; **—statistically significant at 0.01%.

), suggesting that Ca application enhances both biochemicals and perceived sweetness. The application of 1-MCP was generally more effective in increasing TSS compared to the MAP across both years. As MAP treatment slows ripening, it results in a lower TSS content in the treated fruits, which aligns with the findings from Ozturk et al. [17] and Argenta et al. [22]. According to Fan et al. [20], 1-MPC-treated apricot cultivar ‘Perfection’ had higher TA in comparison to the untreated fruits. The impact of the applied treatments on TSS varies between the years, potentially due to differences in Ca availability and supply within the plant, since an adequate volume of nutrients promotes starch hydrolysis into sugars, leading to an increase in TSS [36]. The impact of the year and postharvest treatments had no notable impact on the TSS/TA ratio expressed through the ripening index. Preharvest Ca treatment positively influenced the ripening index, as shown by the higher values (Table 2). Leccese et al. [5] stated that the TSS values, as well as the TSS/TA ratio, depend on the fruit maturity stage, position in the canopy, cultivation system, season (year), and weather conditions.

3.3. Bioactive Compounds

Apricots are a rich source of carotenoids, and their content increases during storage, regardless of the treatment [38]. Leccese et al. [5] claimed that storage of fruits had no negative effect on the content of carotenoids, which is also confirmed by our results (Table 2). The present study found a strong dependence of the carotenoid content on the growing season, highlighting the year as a one of the key factors. The slight increase in carotenoid content in 2017 vs. 2016 may reflect the influence of oxidative stress under dry conditions, which can stimulate carotenoid synthesis [39]. After harvest (0 day), Ca treatments contributed to a higher content of carotenoids in apricots from 2016, but not in those from 2017. Cold storage increased the carotenoid content in all treatments from 2016, while in 2017, this effect was recorded only with Ca treatment, when compared to the control fruits (Table 2). A comparison of postharvest treatments in 2016 showed that 1-MCP application resulted in a higher carotenoid content when compared to MAP, supporting previous reports that MAP treatment has no significant impact on the total carotenoid content [39,40]. During 2017, the differences in carotenoids between postharvest treatments were not significant.

Several studies have indicated that levels of phenolic compounds tend to decrease during storage [17,41,42,43]. At harvest, the phenolic content varied depending on the year, with notably lower levels recorded in 2017 (Table 2). After storage, almost all apricots had a decrease in phenolic content, except for 1-MCP-treated control fruits from 2017 (Table 2). Ca treatments did not result in a higher phenolic content compared to the control, and the combination of Ca and postharvest treatments had no significant impact on these compounds. Most authors agree that the content of carotenoids and phenols during storage is influenced by many factors such as climatic conditions, fruit maturity, oxidative and abiotic stress, position of the orchard, and method of cultivation [39,44,45,46,47,48].

3.4. Respiration Rate

Monitoring respiration intensity, along with other ripeness and quality parameters, facilitates efforts at determining the moment of harvest [49], as well as fruit senescence [50]. In general, apricots from 2017 exhibited a slightly higher respiration rate compared to those from 2016, both after the harvest and after cold storage (Figure 1a,b). As expected, respiration markedly increased after cold storage, across all treatments, reflecting intensified metabolic activity, likely associated with ripening or storage-induced stress (Figure 1a,b). In 2017, preharvest Ca slightly elevated respiration at harvest, suggesting enhanced metabolic activity during fruit development. Postharvest treatments (MAP and 1-MCP) showed different effectiveness in reducing the respiration rate, depending on the year. After storage, in 2016, MAP, 1-MCP, and Ca individually suppressed the respiration rate, delaying ripening and senescence (Figure 1a). Interestingly, in 2017, MAP and Ca individually increased respiration (unlike 1-MCP) (Figure 1b), possibly due to higher initial fruit firmness and reduced permeability of the fruit skin, which may have trapped respiratory gases and created a suboptimal internal atmosphere [42]. Also, the reduced effectiveness of 1-MCP in lowering the respiration rate in 2017 fruits vs. those in 2016 may be due to elevated ethylene receptor activity under drought stress, thus requiring higher inhibitor concentrations (1-MCP) for optimal results [51]. Combined treatments (Ca + MAP or Ca + 1-MCP) had contrasting outcomes, indicating a possible complex interaction among the treatments.

The reduced respiration intensity in apricots at the beginning of the experiment in 2016 may be attributed to the observed differences in TA between the fruits from the two years [52]. Rapid loss of moisture can also be the reason for this variability, as fruit weight loss is often associated with the speed of water vapor transfer and increased respiration intensity [42]. Additionally, the skin of the apricot is covered with fine hair, which can sometimes be the reason for lower absorption of the applied treatment. The observed variability in apricot respiration rate between 2016 and 2017 strongly points to a complex interaction between environmental factors and applied treatments, emphasizing the need for further exploration of treatment combinations for optimal postharvest quality management.

3.5. Sensory Analysis

Consumer preferences are decisively shaped by the sensory attributes of apricots, such as sweetness, acidity, aroma, and texture, which are widely appreciated by consumers. If a specific level of these attributes is not met, even all the well-documented nutritional values and health benefits [36,53] may not be sufficient to encourage apricot consumption, as the fruit fails to meet consumers’ expectations. The sensory attributes strongly influence the overall acceptance and perceived quality of the fruit, directly influencing consumer purchasing decisions. Therefore, in addition to extensive analysis of physicochemical attributes, it was equally important to examine the influence of the applied treatments and the growing season on the sensory attributes of the fruit (Table 3).

Based on the results obtained, the year was the primary factor influencing many of the evaluated attributes (four out of six): sweetness, acidity, aroma, and crispiness (Table 3). The drier and warmer conditions in 2017 likely concentrated sugars and acids in the fruit, intensifying perceived sweetness and acidity. Conversely, the wetter conditions in 2016 may have led to a dilution of these compounds, resulting in lower sensory scores. These seasonal differences significantly influenced texture, flavor, and the overall quality of fresh apricots. Sweetness increased in all Ca-treated apricots, with the highest values for Ca + 1-MCP in 2016 and Ca + control in 2017. Conversely, 1-MCP markedly reduced sweetness in 2017. Acidity was generally higher in 2017, particularly in Ca + 1-MCP fruits. Notably lower acidity was recorded in fruits from 2016, especially Ca-treated. Aroma was intensified in Ca-treated apricots in 2016, whereas in 2017, this effect was observed in Ca-treated fruits immediately after harvest. Crispiness was higher in apricots from 2017 versus those from 2016. Furthermore, crispiness increased across all treatments following storage, with the most pronounced effect observed in 2017 for apricots subjected to a combination of Ca and postharvest treatments, particularly those treated with Ca + 1-MCP. Gumminess was influenced only by postharvest treatments in a way that increased in almost all treated apricots, except in control + MAP in 2016. Ca improved sweetness and aroma, which was supported by higher TSS levels and delayed ripening, as supported by biochemical analyses. However, this treatment had a limited textural impact. 1-MCP increased crispiness and aroma scores in treated apricots, which aligns with their superior firmness retention and delayed ripening. This observation highlights the effectiveness of 1-MCP in maintaining textural quality. MAP effects were inconsistent, requiring further evaluation under varying storage conditions. No foreign taste was observed in the examined apricots, which is an important observation, as our goal was to ensure that the applied treatments did not negatively affect the apricots’ flavor. Our findings align with those of Muftuoğlu et al. [40], who reported that apricot fruits subjected to MAP technology can be stored for up to 28 days without any negative effect on taste. These findings underscore the importance of combining sensory data with physicochemical measurements to gain a comprehensive understanding of how storage treatments influence fruit quality.

The sensory–physicochemical relationships revealed complex interactions that varied by treatment and year. Ca-treated fruits demonstrated that enhanced sweetness perception correlated with a higher TSS content, supporting the biochemical basis for improved sensory quality. However, the relationship between firmness and sweetness was treatment-dependent: while Ca treatment enhanced both firmness retention and sweetness perception, MAP consistently maintained higher acidity and delivered a more stable physicochemical performance across years, supporting better flavor retention, and 1-MCP was more effective at preserving firmness but reduced sweetness perception and aroma development, especially in apricots from 2017. This finding highlights the differential impacts of these two treatments on physicochemical properties and sensory attributes. The positive correlation between measured TSS and sensory sweetness scores validates the reliability of both assessment methods, while the divergent responses to different treatments highlight that texture and flavor development can be independently influenced by postharvest interventions, underscoring the need for integrated quality assessment. Such evidence reinforces the importance of considering both physicochemical and sensory perspectives when evaluating postharvest strategies, as correlations do not necessarily imply direct causation but rather reflect complex metabolic and perceptual networks.

Principal component analysis (PCA) (Figure 2) was performed to evaluate the effects of preharvest calcium (Ca) and postharvest treatments (MAP, and 1-MCP treatment, cold storage, and shelf life) on the physicochemical properties of apricots over two seasons (2016 and 2017).

The first two principal components (PCs) explained a total of 65.03% of the variation in the dataset, with PC1 accounting for 44.26% and PC2 for 20.77%. The score plot revealed a clear separation between seasons, indicating a strong year-to-year effect. Within each year, fruit treated with Ca is clustered separately from untreated controls, suggesting a significant impact of Ca treatment on fruit characteristics. A time-dependent shift along PC1 was observed from day 0 to 15 + 3 days of storage, reflecting postharvest changes in fruit quality. The corresponding loading plot showed that PC1 was primarily associated with traits related to ripening and metabolic activity, such as total soluble solids (TSS), TSS/TA ratio, carotenoids, and CO₂ production, whereas PC2 was more closely related to firmness, titratable acidity (TA), lightness (L*), and phenols, which are indicators of structural and nutritional quality. These findings demonstrate that Ca application, in combination with appropriate postharvest handling, can influence the direction of quality changes in apricot fruit during storage.

However, the initial PCA based solely on physicochemical attributes did not allow for a clear differentiation among the postharvest treatments. Therefore, an additional PCA was performed, incorporating both physicochemical and sensory traits, to better evaluate the combined effects of preharvest Ca application and different postharvest treatments (MAP and 1-MCP) on apricot fruit quality after 15 days of cold storage followed by 3 days of shelf life (Figure 3). The first two principal components explained 66.32% of the total variance, with PC1 (39.18%) capturing variation related to flavor and nutritional attributes (sweetness, aroma, carotenoids, phenols, and TSS), and PC2 (27.14%) representing variation in textural and biochemical properties (firmness, TA, CO₂ production, L*, crispiness, and gumminess). The score plot revealed a clear separation among treatments, with Ca-treated fruit and MAP samples showing higher scores for sensory and nutritional quality, while MCP-treated fruit aligned with preserved texture and delayed ripening characteristics. Year-based separation remained evident, emphasizing the influence of seasonal variability. These findings demonstrate that both preharvest and postharvest strategies distinctly influence the overall quality profile of apricot fruit, with Ca and MAP treatments promoting a better retention of sensory quality attributes.

The growing season had a pronounced influence on the physicochemical and sensory properties of apricot fruit. In both PCA analyses, samples from 2016 and 2017 formed distinct clusters, indicating strong year-to-year variability. These differences likely reflect variations in environmental conditions such as temperature, rainfall, and sunlight exposure during fruit development, which are known to affect ripening and quality traits. For example, fruit harvested in 2017, grown under drier conditions, aligned more closely with firmness, crispiness, and titratable acidity, suggesting delayed softening and greater structural integrity. In contrast, fruits from 2016, grown under more favorable conditions with abundant precipitation, were characterized by a more intense aroma and sweetness, as well as higher carotenoid and phenol contents. These traits reflect enhanced secondary metabolite accumulation and improved nutritional quality. Such seasonal effects emphasize the importance of evaluating postharvest technologies across different growing conditions to ensure a consistent fruit quality.

Preharvest Ca application was the second most influential factor affecting fruit quality across both seasons, after the growing season. Ca-treated fruit consistently separated from controls in the PCA score plots, particularly in 2016, and aligned with physicochemical traits associated with an improved storage quality, including higher firmness and titratable acidity. In the PCA that included sensory attributes, Ca-treated apricots were also positively associated with sweetness, aroma, carotenoids, and phenols. These findings indicate that Ca not only contributes to delay softening and reduced metabolic activity but may also enhance nutritional and sensory quality, particularly under favorable environmental conditions. The effects of preharvest Ca application and postharvest treatments were strongly modulated by the growing season. In 2016, Ca-treated fruit exhibited enhanced sweetness and a brighter color (reflected by higher PC2 scores), while non-treated fruit maintained higher levels of phenols and carotenoids. In 2017, the influence of Ca was less pronounced, though it slightly relates to acidity and crispiness.

The differential response of Ca treatment between years demonstrates that its effectiveness depends on environmental conditions affecting Ca uptake and fruit physiology. Under the wetter 2016 conditions, enhanced Ca availability and improved transport resulted in greater treatment benefits, while the water-limited 2017 season reduced Ca effectiveness. Montanaro et al. (2006) [28] reported that more than half of the Ca concentration acquired by the fruit was the result of transpiration; therefore, it can be concluded that increasing the fruit transpiration rate in the early stage of the season would be beneficial for improved Ca nutrition, as already demonstrated for kiwifruit. Additionally, the larger, more hydrated fruits produced in 2016 were likely more susceptible to postharvest softening, possibly due to altered cell wall integrity. Under these conditions, Ca application might have provided greater benefits through its proposed role in cross-linking pectic substances. The smaller fruits from the drier 2017 season may have experienced both reduced Ca uptake efficiency and inherently less need for firmness enhancement due to their naturally denser structure. This climate dependency challenges the conventional approach of standardized treatment protocols and supports the need for adaptive management strategies based on seasonal conditions.

Postharvest treatments played a critical role in determining fruit quality during storage and shelf life. MAP was positively associated with flavor- and nutrition-related traits such as sweetness, aroma, carotenoids, and phenols, particularly when combined with preharvest Ca application. This suggests a synergistic effect that supports the retention of sensory quality. In contrast, 1-MCP treatment was more strongly associated with traits such as crispiness, acidity, TSS, and gumminess, reflecting its effectiveness in delaying ripening and senescence. However, 1-MCP-treated fruits were generally less aligned with favorable sensory traits, indicating a trade-off between shelf-life extension and full flavor development. Control fruit was typically positioned away from quality-related variables, highlighting accelerated quality degradation in the absence of postharvest intervention. Postharvest treatment effects also varied between growing seasons. In 2016, both MAP and 1-MCP had relatively limited differential impacts. In contrast, during the drier 2017 season, 1-MCP treatment led to a more distinct shift toward higher TSS and gumminess. Notably, the combination of Ca and 1-MCP in 2017 further enhanced acidity and crispiness, demonstrating a synergistic effect under water-limited conditions. These findings underline the importance of tailoring both preharvest and postharvest strategies to seasonal conditions to optimize the maintenance of apricot quality during storage and shelf life.

MAP and 1-MCP employ fundamentally different preservation mechanisms with distinct advantages. MAP creates modified-atmospheric conditions (reduced O₂, elevated CO₂) that slow metabolic processes and delay ripening [54], while 1-MCP blocks ethylene receptors, directly inhibiting ethylene-triggered ripening cascades [55]. In our study, MAP consistently maintained higher acidity levels across both years and showed a more predictable performance regardless of climatic conditions (Table 2). In contrast, 1-MCP was more effective at preserving firmness but reduced sweetness perception and aroma development, with effects more pronounced in 2017 (Table 2 and Table 3). These findings suggest that MAP may be more suitable when flavor retention is prioritized, while 1-MCP offers superior texture preservation but potentially at the cost of sensory quality.

This study has several limitations that should be considered. The two-year duration may not capture the full range of climatic variability affecting treatment efficacy, and results are specific to apricot cv. ‘Buda’ under controlled orchard conditions. Treatment responses may vary among different cultivars and under commercial production environments with greater variability in storage conditions. Additionally, consumer acceptance studies and detailed economic analyses would strengthen the practical applicability of these findings. Despite these limitations, this study provides the first systematic evidence for climate-dependent pre- and postharvest treatment efficacy in apricots.

4. Conclusions

The observed differences in the overall quality of apricot fruit between 2016 and 2017 emphasize the critical role of climatic conditions in the efficiency of treatment at shaping fruit quality. Environmental factors, including precipitation, temperature, and drought stress, significantly influence both fruit physiology at harvest and the response to preharvest and postharvest treatments.

Calcium emerged as the second most influential factor on apricot fruits, after the seasonal effect. Its application prominently reduced the loss of fruit firmness in the wetter 2016 in respect to control apricots but showed limited benefits in the drier 2017. MAP delayed ripening and maintained higher acidity levels than in the respective control, while 1-MCP preserved firmness, but reduced sweetness and aroma, particularly in 2017. Sensory evaluation confirmed that Ca-treated fruits were perceived as sweeter, with no negative impacts on overall taste, supporting the feasibility of these treatments for extending shelf life. PCA revealed that the greatest impact on apricot quality was attributed to the year and preharvest Ca treatment, while postharvest treatments had a lower impact, with similar outcomes regardless of the treatment or initial fruit quality. In general, for commercial applications, Ca treatments should be prioritized during wet seasons, while MAP provides consistent benefits regardless of climatic conditions.

The present observation of year-dependent treatment responses challenges the current paradigm of universal postharvest protocols and establishes the foundation for climate-responsive fruit-handling strategies

Also, the findings underline the importance of conducting multi-year studies to account for interannual variability and develop specifically tailored protocols that can ensure the optimal fruit quality of apricots under varying environmental conditions.

Given the significant role of apricots both domestically in Serbia and in global markets, the present findings contribute to efforts aimed at ensuring a consistent quality in the face of climatic variability, which is crucial for meeting consumer preferences and sustaining economic profitability through reduced postharvest losses and prolonged market availability.