Effect of Preharvest Aluminum-Coated Paper Bagging on Postharvest Quality, Storability, and Browning Behavior of ‘Afrata Volou’ Quince

Abstract

As consumer preferences tend toward safer, chemical residue-free, and nutritionally rich fruits, preharvest bagging has gained attention as a sustainable method for improving fruit quality and protecting produce from environmental and biological stressors and pesticide residues. This study assessed the impact of preharvest bagging using paper bags with inner aluminum coating on the physicochemical traits, storability, and browning susceptibility after cutting or bruising of ‘Afrata Volou’ quince (Cydonia oblonga Mill.) fruit grown in central Greece. Fruits were either bagged or left unbagged approximately 60 days before harvest, and evaluations were conducted at harvest and after three months of cold storage, plus two days of shelf-life. Fruit bagging reduced the quince’s flesh temperature on the tree crown. Bagging had minor effects on fruit and nutritional quality, except for more yellow skin and higher titratable acidity (TA). Also, at harvest, bagging did not significantly affect fruit flesh browning after cutting or bruising. After three months of storage, unbagged and bagged quince fruit developed more yellow skin color, without significant alterations in most quality characteristics and nutritional value, but increased total tannin content (TTC). After three months of storage, the quince flesh color determined immediately after cutting or bruising was brighter and more yellowish compared to that at harvest, due to continuation of fruit ripening, but it darkened faster with time after cutting or skin removal. Therefore, fruit bagging appears to be a sustainable practice for improving the aesthetic and some chemical quality characteristics of quince, particularly after storage, without negative impacts on other characteristics such as texture and phenolic content.

1. Introduction

In recent decades, people have tended to look for safer and more nutritious food choices, resulting in higher consumption of fruit and vegetables. Consumers prefer fruits of high quality and nutritional value, but also with low or no agrochemical residues. The European Union has phased out most of the insecticides that were used, rendering alternative methods to protect fruits extremely important, especially for minor crops with very few or no permitted plant protection products.

Fruit quality is a combination of its outside appearance (shape, size, and skin color) and organoleptic characteristics (texture, soluble solids content, and acidity). The nutritional value of fresh fruit is also of vital importance for selection by consumers since antioxidant capacity and total phenol content are essential for human health. All the above quality characteristics change substantially due to climate and agricultural practices [1,2,3]. In addition, during fruit growth and maturation, quality can be degraded by insects, birds, diseases, and mechanical reasons (hail, bruising from wind, scratches from shoots, etc.) [3,4].

Sunlight is necessary for quality fruit production. It influences fruit development by enhancing fruit size, improving skin color (particularly in red-skinned fruits through increased anthocyanin accumulation), and elevating the sugar content and ratio of soluble solids content/acidity. Generally, fruits exposed to light ripen earlier than shaded fruits [5]. However, exposure of fruits to high-intensity sunlight increases the risk of sunburn, especially in yellow fruits, as well as the possibility of postharvest skin browning [6]. Pre-harvest bagging during fruit growth is an alternative method that protects fruit from adverse weather effects, high-intensity sunlight, air pollution, pesticide residues, mechanical damage, sunburn, and pests [7]. Therefore, it is suggested as a cultivation practice suitable for organic farming, producing fruits with improved quality and safety [3]. In addition, fruit bagging may reduce physiological abnormalities, resulting in improved commercial value [4].

Several studies have reported the effect of preharvest bagging on fruit quality characteristics, but there is still a gap regarding the effects of bagging on quince. Individual fruit bags can alter fruits’ microenvironment, such as available light, temperature within the bag, fruit temperature, and humidity [7]. These changes can modify fruit quality characteristics (e.g., skin color) [8], depending on bag type, fruit growth stage, duration of bagging, days of bag removal before harvest, fruit species, and cultivar [9,10,11,12]. Bag type was found to play a crucial role in the external and internal quality of loquat and banana [11,12]. In the case of pome fruits, preharvest bagging of pears sometimes improved fruit skin color, but elsewhere, bagging treatment decreased total sugars and organic acids and led to a less attractive appearance, without affecting fruit size, weight, firmness, and soluble solid concentration [1]. In apples, enclosing fruit of cv. ‘Fuji’ in paper bags delayed and reduced red color development [9]. Varying the timing of pre-harvest bagging had different effects on the internal quality of apples, with delayed bagging shown to enhance soluble solids, firmness, total phenols, flavonoids, and other intrinsic quality indicators of the Ruixue apple, while also reducing the degree of peel browning [13]. In general, preharvest fruit bagging was found to decrease phenolic compounds of fruits, as in the case of pear fruit peel [10] and apple, where fruit bagging decreased most of the phenolic compound concentrations in both the peel and flesh [14].

Quince (Cydonia oblonga Miller) is an aromatic climacteric pome fruit that provides many benefits to human health due to the presence of bioactive components and, in particular, polyphenols, including tannins, with increased antioxidant activity [15,16,17,18,19]. Although quince is not preferred for raw consumption due to its astringent/tart taste [20,21], it is widely used after processing, mainly as baked desserts, juices, jams, and jellies [17,18,22,23]. This fruit is mostly cultivated in warm temperate climates such as the Mediterranean basin [16], where warm weather persists during early autumn. As the fruit growing cycle is long, quince is exposed to many risks. One of the most important hazards in the Mediterranean region, and particularly in Greece, is the Mediterranean fruit fly, which annihilates fruit quality [24]. In addition, the codling moth has at least three generations per year, requiring repeated insecticide applications that possibly leave residue on the fruit. Finally, although quince is a minor crop in Greece, farmers earn a good profit, as market demand is significant. Consequently, more research is required for alternative methods to insecticide use and their impact on fruit quality and storability.

Insufficient research has been conducted about quince fruit quality and storability compared to other pome fruits [22]. Quince fruit can be stored for two to six months in a regular air storage room at 0 or 2 °C [25]. Nevertheless, commercially, quince fruit are not stored for more than 3–4 months in Greece. The storage period of quince is also cultivar-dependent during cold storage with 0 ± 1 °C and 90 ± 5% relative humidity (RH) [26]. Throughout the storage period, quince fruit present several quality changes. Total soluble solids and the ratio of soluble solids to titratable acidity increase, reaching their peak in the fourth month of storage. In contrast, fruit firmness decreases, and weight loss continues to rise over the five-month storage duration [26]. An extended storage duration was found to affect the intrinsic quality of quince, resulting in a reduction in phenol content across all studied cultivars and genotypes [26]. Further fruit storage for up to seven months is possible under controlled atmosphere conditions of 2 kPa O₂ and 3 kPa CO₂ at 2 °C. The treatment of quince fruit with 1-MCP effectively preserved quality characteristics during storage. Additionally, hot water treatment prior to storage has been explored as a potential method for maintaining fruit quality during long-term storage under regular air conditions at 0 ± 1 °C and 85–90% RH for up to six months [25].

Quince fruit are susceptible to flesh browning [17], which has adverse effects on the commercial value of fruit and consumer acceptance [22]. Browning is related to enzymatic reactions and occurs either due to cutting and exposure of the injured flesh to the ambient air [27] or bruising during harvest, storage, or commercial handling [18]. Various chemical, physical, and ultrasound treatments have been investigated for their effects on the shelf life of fresh-cut quince fruit, aiming to reduce enzymatic browning. Among these methods, ultrasound treatment was the most effective in preserving color and preventing enzymatic browning [28]. A study on the browning kinetics and color changes in quince fruit slices exposed to atmospheric conditions showed that quince undergoes significant browning, with the most substantial color changes occurring within the first 30 min of exposure [29]. Polyphenol oxidase (PPO) and peroxidase (POD) are the main enzymes involved in fruit phenolics, including tannin transformations [17,30,31,32]. Phenolic compounds are found in higher concentrations in the peel and core of quince fruit, followed by the flesh, so browning intensity varies between different fruit parts [17]. Bagging was used to protect fruit from insect damage in the era of pesticide use and residue reduction. The present research aimed to study the effect of individual fruit inclusion in a paper bag with an inner aluminum coating on the quality of quince fruit at harvest and after three-month cold storage, and on fruit sensitivity in browning rate after cutting or bruising. The assumption of the present study is that the specific paper bags with an inner aluminum coating would create an environment of total darkness with a minor effect on the air and fruit temperature within the bag. This microenvironment could result in fruit quality alterations, which was the main scope of the research. Limited relevant research has been conducted on quince fruit bagging, and the current study provides new insights on quince fruit preharvest and postharvest handling, as well as the effect of bagging and cold storage on quince fruit behavior after cutting or bruising.

2. Materials and Methods

2.1. Experimental Trees

The study was conducted on quince trees of a local variety ‘Afrata Volou’ in the experimental farm of the University of Thessaly in Velestino, central Greece (39°23′40.0164″ N, 22°45′25.6392″ E). Quince trees were 19 years old and trained as an open vase. The usual local horticultural practices were applied.

2.2. Treatments

In July (25 July 2020), about 60 days before the expected harvest (mid-September–mid-October) [16] and 90 days after full bloom, fruits were bagged in individual paper bags with an inner aluminum coating. The aluminum-coated paper bags provided 0% light transmittance while preventing excessive fruit heating. Treatment consisted of seven replications (one tree per replication). Bagged fruits were 50% of the fruit on every tree, while the rest were kept unbagged. Selected fruits from the two treatments were located both on the sunny and shaded parts of the tree crown, uniformly spread throughout the canopy. Every single paper bag was tightly secured with a paper stapler around the fruit stalk. Quince fruit were kept bagged until hand harvest. Unbagged and bagged fruit were harvested at the optimum market maturity stage of unbagged treatment, as is customary locally, in early October (10 July 2020). In this stage, quince fruit were mature with a light green skin color [15].

2.3. Measurements

2.3.1. Field Measurements Before Harvest

Fruit temperature (°C) on the quince crown was measured a few days before harvest, at 12:00 and 14:30, using a digital thermometer (Oregon Scientific, model no. SA880SSX, Tualatin, Oregon, USA) equipped with a probe measuring the mean fruit flesh temperature from a 5 cm depth.

2.3.2. Fruit Quality Measurements

Quince fruit quality of the two treatments was determined both at harvest and after a three-month cold storage time (−1 °C and >95% RH) with an additional two-day shelf-life (dSL) at ambient conditions (20 °C, 40–50% RH—proper temperature for ripening [33]). Bagged fruit were harvested and stored in paper bags to avoid exposure to light until fruit quality measurement.

The fruit quality at harvest and after three months of storage of both treatments was evaluated in seven replications of five fruit each, after skin fuzz removal with a soft cotton cloth. Quality measurements included fruit mass (FrMass), skin fuzz mass (FMass), skin and flesh color, flesh firmness (FF), soluble solid content (SSC), titratable acidity (TA), and the calculated ratio SSC/TA.

For FrMass and Fmass determination, a laboratory two-decimal digit scale was used.

Skin color was estimated on the equator at four sides around the fruit. Flesh color was measured immediately after peel removal. The Minolta chroma meter (Model CR-400, Minolta Ltd., Osaka, Japan) was used to determine skin and flesh color with CIE L*, a*, and b* values. The above parameters were used to calculate the hue angle (color saturation) with the following equation [34]:

$$\mathrm{H}\mathrm{u}\mathrm{e}={\mathrm{t}\mathrm{a}\mathrm{n}}^{-1}\left({\displaystyle \frac{{\mathrm{b}}^{\mathrm{*}}}{{\mathrm{a}}^{\mathrm{*}}}}\right)$$

A hue angle of 0° or 360° indicates a red color, while hue angles of 90°, 180°, and 270° represent yellow, green, and blue colors, respectively [35].

After peel removal with a hand peeler, FF was determined in Newton (N) on the equator at two opposite sides of each fruit with a digital penetrometer (model 53205, Turoni Srl, Forli, Italy) equipped with an 8 mm plunger. SSC was measured from the juice squeezed from the middle part of two opposite-sided longitudinal slices of each fruit with an Atago Refractometer (PAL-1, Atago Co., Tokyo, Japan). Finally, TA was calculated using the above juice diluted with water to 1:10, after titration with 0.1 N NaOH up to pH 8.2, and expressed as g of malic acid per 100 mL of quince juice.

2.3.3. Flesh Color Changes with Time After Cutting

For both treatments, five quince fruits were sampled from each of the seven replications, cut in half, and left in the laboratory exposed to atmospheric conditions at a room temperature of about 20 °C and 40–50% RH. The laboratory room was well-lit, receiving abundant natural light through the windows. Flesh color was estimated by a Minolta chroma meter from 5 to 20 min after cutting with L*, a*, and b* color parameters measured every 5 min. Then, the total color difference and the browning index were calculated.

Calculation of total color difference

Total color difference (ΔE) was calculated by the following equation [36]:

$$\mathsf{\Delta }\mathrm{E}=\sqrt{{\left({\mathrm{L}}_0^{\mathrm{*}}-{\mathrm{L}}^{\mathrm{*}}\right)}^2+{\left({\mathrm{a}}_0^{\mathrm{*}}-{\mathrm{a}}^{\mathrm{*}}\right)}^2+{\left({\mathrm{b}}_0^{\mathrm{*}}-{\mathrm{b}}^{\mathrm{*}}\right)}^2}$$

where L₀*, a₀*, and b₀* represent the reference flesh colors.

ΔE is a parameter of color often used to characterize color alteration. Greater ΔE value indicates a larger deviation from the initial color of the reference material [29].

Calculation of browning index (BI)

BI was calculated using L*, a*, and b* flesh color parameters and was applied as an indicator of brown discoloration intensity by the equation below [37]:

$$\mathrm{B}\mathrm{I}={\displaystyle \frac{\left[100\left(\mathrm{x}-0.31\right)\right]}{0.17}}$$

where:

$$\mathrm{x}={\displaystyle \frac{({\mathrm{a}}^{\mathrm{*}}+1.75{\mathrm{L}}^{\mathrm{*}})}{(5.645{\mathrm{L}}^{\mathrm{*}}+{\mathrm{a}}^{\mathrm{*}}-3.012{\mathrm{b}}^{\mathrm{*}})}}$$

(1)

2.3.4. Total Phenolic Content and Total Antioxidant Activity

To measure the total phenolic content (TPC) and total antioxidant activity (TAA) of quince fruit, seven replications of five fruit each per treatment were used. Ten slices of fruit (two from each fruit from opposite sides) were homogenized and a sample of 5 g slurry (flesh plus peel) was extracted with 25 mL of methanol. The methanolic extract was centrifuged at 4000× g for 10 min at room temperature. TPC and TAA were measured with the supernatant by a UV–Vis spectrophotometer (Optizen Pop, Mecacys, Daejeon, Republic of Korea). TPC was measured as previously described using Folin–Ciocalteu reagent at 760 nm and expressed as mg of gallic acid equivalents per g of fresh weight [38]. TAA was expressed as μmol of ascorbic acid equivalents per g of fresh weight and evaluated by DPPH assay at 517 nm using 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and a FRAP assay at 593 nm with the ferric ion-reducing antioxidant power method, as previously described [39,40].

2.3.5. Total Tannin Content

To measure the total tannin content (TTC) of quince fruit, seven replications of five fruit each were used. Ten slices of the fruits (two from each fruit on opposite sides) were squeezed, and the juice was diluted with distilled water at 1:10. The measurement of TTC was conducted on the diluted quince juice at 760 nm using a spectrophotometer (Optizen POP, Mecasys Co., Ltd., Daejeon, Republic of Korea) with the Folin–Denis reagent and expressed as mg of tannic acid equivalents per 100 mL of juice, according to Nair et al. [41].

2.3.6. Bruising

Five healthy fruits from each of the seven replications of both treatments were selected to measure bruising severity at harvest and after three months of storage. According to Opara [42], the fruits were marked with a marker in the equatorial area. Artificial bruising was induced using a 400 g iron bar (simulating the weight of quince fruit) with a flat contact surface, dropped from a height of 30 cm onto a marked area through a vertical hollow PVC tube. Immediately after bruising, the skin was removed, and the flesh color was measured before any flesh color change. Then, measurements of the flesh color were taken every 10 min up to 40 min. Finally, the flesh BI and flesh ΔE were calculated as mentioned above. According to Wang et al. [43], the degrees of difference for the ΔE scales are characterized as a perceptible difference when ΔΕ = 3.0–6.0, a strong color difference when ΔΕ = 6.0–12.0, and different colors when ΔΕ > 12.0.

2.4. Statistical Analysis

Analysis of variance was conducted over treatment and time of storage by SPSS (SPSS 29.0, IBM Corp., Armonk, NY, USA). The difference among treatments and storage time were evaluated using the least significant difference (LSD) and Tukey mean separation for p ≤ 0.05 significance level.

3. Results and Discussion

3.1. Fruit Temperature

From temperature measurements of quince fruit on the tree crown, one week before fruit harvest, bagged fruit had lower temperatures (up to 3 °C at 12:00 and up to 8 °C at 14:30) than unbagged fruits. The above measurements agree with Ali et al. [3], who mentioned that the presence of a bag reduces the sunlight on the fruit surface and fruit temperature by 2.95 to 6.67 °C in Fuji apples bagged in two different paper bags. Furthermore, Buthelezi et al. [8] mentioned that bags with a reflective inner coating (like in our experiments) can protect fruits from excessive temperatures.

3.2. Fruit Quality

Fruit mass was similar in both treatments and measurement times (

Table 1. Fruit and skin fuzz mass of unbagged and bagged ‘Afrata Volou’ quince at harvest and after three months of storage plus two additional days of shelf-life.

Time	Treatment	Fruit Mass (g)	Fuzz Mass (g)
Harvest	Unbagged	326 ± 13	0.21 ± 0.02 b
	Bagged	321 ± 26	0.38 ± 0.03 a
3 months storage + 2 d SL	Unbagged	316 ± 17	-
	Bagged	315 ± 16	-
Significance	Time	NS	-
	Treatment	NS	***
LSD0.05		53	-

Each value is mean ± SE. Values followed by different letters within each column are significantly different according to the LSD multiple-range test at p ≤ 0.05. ***—significant differences at p ≤ 0.001; NS—non-significant differences.

). Wang et al. (2024) [13], in accordance with our results, found that bagging of Ruixue apples 90 DAFB had no effect on fruit size and shape compared to unbagged apples. However, Sharma et al. [4,44] reported contradictory results of pre-harvest fruit bagging on fruit size and mass due to different types of bags used, fruit type, fruit development stage at bagging, climatic conditions of the research area, and postharvest conditions. At harvest, the skin fuzz mass of bagged fruit was higher compared to unbagged ones (Table 1). However, Konarska [45] and Karabourniotis et al. [46] mentioned that trichome grows as protection against excessive solar radiation and temperature, which contrasts with our research conditions (dark environment and lower temperature inside the bag).

Bagged quince fruits had brighter skin (higher L* color parameter) than unbagged fruit at harvest (Figure 1a). Similar skin color differences were found after three months of storage. This agrees with previous research on aluminum bagged loquat [45] and bagged pears [1,47,48]. Although Wang et al. [13] mentioned a decrease in skin brightness at delayed bagged yellow-skinned ‘Ruixue’ apples, at harvest, fruit from both treatments had a more greenish skin color than after the three-month storage time, when skin tended to become yellow, as also mentioned by Gunes [22]. This color change is due to the climacteric character of quince that continues to ripen after harvest [34,49], resulting in the degradation of skin chlorophyll [50]. Only at harvest, bagged fruit had less greenish skin color (higher a* and lower Hue) than unbagged fruit (Figure 1b,c). Guan et al. [48] also mentioned an increase in the skin a* color value of bagged ‘Huangguan’ pears. Fruit bagging enhances the destruction of chlorophyll on the quince skin due to the obstruction of sunlight [8,24,47]. Improved skin color was also noticed after preharvest bagging on non-red apple cultivars [51]. Similarly, storage in the dark further reduces the green skin color in fruit.

Quince FF was not affected by either bagging treatment (

Table 2. FF, SSC, TA, and SSC/TA ratio of unbagged and bagged ‘Afrata Volou’ quince fruit at harvest and after three months of storage plus two additional days of shelf-life.

Time	Treatment	FF (N)	SSC (%)	TA (%)	SSC/TA
Harvest	Unbagged	67.8 ± 2.8	17.3 ± 0.1 b	0.69 ± 0.01 c	25.1 ± 0.5 a
	Bagged	69.2 ± 2.4	17.1 ± 0.2 b	0.76 ± 0.01 b	22.5 ± 0.9 b
3 months storage + 2 d SL	Unbagged	70.3 ± 5.8	16.4 ± 0.2 c	0.68 ± 0.02 c	24.1 ± 0.7 ab
	Bagged	62.5 ± 2.2	17.8 ± 0.2 a	0.90 ± 0.03 a	19.8 ± 0.6 c
Significance	Time	NS	NS	**	*
	Treatment	NS	***	***	NS
LSD0.05		10.2	0.5	0.06	1.8

Each value is mean ± SE. Values followed by different letters within each column are significantly different according to the LSD multiple-range test at p ≤ 0.05. ***—significant differences at p ≤ 0.001; **—significant differences at p ≤ 0.01; *—significant differences at p ≤ 0.05; NS—non-significant differences.

). Similarly, bagging loquat fruit for 75 days with an aluminum bag also had no effect on fruit FF compared to unbagged ones [11]. FF was not modified with storage duration up to three months, because of fruit maturation, although Nanos et al. [23] and Gunes [22] reported that quince flesh firmness decreased to a degree with fruit maturation. Bagging of ‘sand pear’ showed increased firmness at harvest [48]. Preharvest bagging of pear fruit increased flesh softening during postharvest storage [1]. It is generally observed that quince fruit flesh firmness is less affected by ripening compared to pears. Bagging had no significant effect on quince SSC at harvest, but SSC of bagged fruits was higher after three-month storage than unbagged fruit due to a loss of SSC of unbagged fruit (Table 2). The highest percentage of SSC was 17.8%, observed on bagged quince fruit after three months of storage. Preharvest bagging was previously found to reduce SSC and TA in pears and apples due to dark conditions inside the bag that inhibit photosynthesis [13,48] or may reduce sink strength. TA was significantly higher on bagged fruit than unbagged, both at harvest (+10.1%) and after three months storage (+32.4%) (Table 2). Bagged fruits may have decreased respiration as fruit remained bagged during storage, which led to increased fruit acidity compared to unbagged ones [52]. Kumar et al. [53] noticed that preharvest fruit bagging had varying effects on the SSC of pears and apples, while it increased TA in pears. TA of unbagged fruit was not affected by cold storage but increased by 18.4% on bagged quince fruits (Table 2). Moradi et al. [54] reported that four-month cold storage of quince fruit resulted in a decrease in FF and TA and an increase in SSC. In our study, the SSC/TA ratio calculated was lower οn bagged fruit compared to unbagged. The decrease was about 10.4% at harvest and 17.8% after three months of storage (Table 2). In contrast to our results, the ratio of SSC/TA in loquat fruits was not affected by the aluminum bagging for 75 days [11]. After quince storage, SSC/TA ratio showed a slight decline in unbagged fruit and a significant decrease of 12.0% in bagged quinces (Table 2).

3.3. Fruit Nutritional Quality

3.3.1. Fruit TPC and TTC

At both harvest and after three months of storage, TPC was slightly lower (not significant) on bagged quince fruits compared to unbagged ones (Figure 2a). TPC levels of the studied cultivar were similar to those mentioned by Göksel [55], who found a range of 0.65–1.67 mg GAE/g fw on 36 quince genotypes, while Moradi et al. [56] reported a range of 1.58–3.81 mg GAE/g fw on 15 quince genotypes. Although no references were found on the effect of bagging on TPC content of quince fruit, corresponding studies on apples showed a decreased concentration of TPC in bagged fruits compared to unbagged, due to limited light inside the bag [2,13]. Similarly, the TPC of aluminum bagged loquat fruit was found to be significantly lower than unbagged fruit [11]. Storage for three months did not significantly affect the TPC of ‘Afrata Volou’ quince fruit of both treatments; however, a downward trend was observed in bagged fruits (Figure 2a). Storage at 2 °C for five months was found to decrease the TPC content of 15 quince genotypes [56].

No differences in quince TTC were observed between unbagged and bagged fruits of this experiment, both at harvest and after three months of storage (Figure 2b). Although, Campbell et al. [57] mentioned that 80% shade on Cabernet Sauvignon increased the tannin content of grapes. TTC increased in unbagged and bagged quince fruit with storage, and this increase was bigger for bagged quinces (+27.5%) (Figure 2b). In India, the concentration of whole quince fruit tannins was about 0.8% [24], while Najman et al. [17] found 4.47 ± 0.09 g of tannins/100 g in freshly squeezed quince juice, which seems extremely high.

Tannins, primarily composed of condensed and hydrolyzable polyphenols, contribute to the astringency and antioxidant profile of fruits. Their synthesis and accumulation are tightly regulated by developmental, environmental, and postharvest factors. As reviewed by He et al. [58], the biosynthesis of tannins involves a complex network of the shikimic acid, phenylpropanoid, and flavonoid pathways, which are influenced by transcriptional and post-translational regulation. The observed increase in TTC during storage may result from the enhanced expression of tannin biosynthesis-related genes or reduced activity of enzymes responsible for tannin polymer breakdown.

According to Montes-Ávila et al. [59], postharvest conditions can promote the oxidation and condensation of tannins, increasing their extractability and possibly their measured concentration. Storage may also enable changes in cell wall integrity, releasing bound phenolics into extractable forms. Furthermore, Wu et al. [60] emphasized the role of molecular signals and hormonal cues, such as abscisic acid and ethylene, in modulating the accumulation and solubilization of tannins in fruit tissues during ripening and storage. Their findings support the idea that the increase in TTC observed in this study, particularly in bagged quince, could be linked to altered hormonal and gene expression profiles induced by microclimatic changes from bagging and cold storage.

3.3.2. Fruit TAA

At harvest and after three months of storage, TAA measured on quince fruit with the DPPH method was similar in both treatments (Figure 3a). However, DPPH values decreased after storage compared to harvest by 11% for unbagged and 30% for bagged fruits (Figure 3a). The TAA values of quince fruit determined with the FRAP method were not affected by the treatments and storage time (Figure 3b). In Hungary, TAA using the FRAP method was 59.9–631.0 μmol AA equivalents/g fw in 12 genotypes of quince [61]. Buthelezi et al. [8], opposite to our findings, mentioned that preharvest fruit bagging promotes the biosynthesis of secondary metabolites such as phenols and antioxidants. Finally, the results demonstrate that quince fruits are rich in bioactive components with potential health benefits [55].

3.4. Flesh Color Changes with Time After Cutting

At harvest, quince flesh color darkened and browned (lower L* and Hue) severely from 0 to 5 min after fruit cutting and remained relatively constant until 20 min on both bagged and unbagged fruit (Figure 4a,b). However, flesh became darker and browned gradually with time after cutting in stored quince fruit, regardless of treatment (Figure 4a,b). Although fruits after storage consistently exhibited brighter and less brown flesh immediately after cutting compared to fruits at harvest, the degree of color change over time was more pronounced, suggesting a distinct browning dynamic influenced by postharvest physiological changes.

The quince flesh darkening and browning after cutting is primarily attributed to enzymatic browning, a process induced after injury and exposure to air. Skin removal causes an increase in ethylene production, which prompts higher enzymatic activity and synthesis of phenolic compounds [62]. Similar results on 14 apple cultivars were reported by Serra et al. [63]. Browning of the cut area of apples usually occurs within the first 10 min or slightly more [64], which aligns well with the rapid browning dynamics observed in quince at harvest in this study. This enzymatic process happens due to the activation of phenolic compounds, especially 5-O-caffeoylquinic acid, a predominant phenolic compound in quince fruit, which is the main substrate of the PPO enzyme [18,65]. PPO is contained within organelles, while phenolic substrates are stored in the vacuoles [66]. The activation of PPO only happens when these compartments are disrupted by tissue wounding [30,67], i.e., phenolic compounds are released and oxygen is present [27,31]. PPO catalyzes the oxidation of these phenolic compounds into quinones, which then polymerize into brown pigments (melanins) [27]. Quince fruit has a much higher concentration of total phenols than apple [55]; in addition to the large activity of PPO present in quince fruit [68], rapid flesh browning occurs after cutting. At harvest, the rapid flesh browning suggests high PPO activity, while after storage, the slower flesh browning indicates reduced PPO activity due to cold storage [69,70]. Similar delayed browning responses were described in sand pear by Fan et al. [71], who found that cold storage and wounding modulated the expression of key browning-related genes (PPO, PAL, and POD) and impacted the progression of oxidative browning upon cutting.

The speed and severity of enzymatic browning in plant products are influenced by the nature and content of polyphenols, the availability of oxygen, and the activity of related enzymes. This activity is affected by physicochemical conditions such as temperature, pH, and water activity, along with the presence of natural inhibitors [66]. Sultan et al. [72] emphasized that changes in membrane integrity, tissue microstructure, and stress-related gene expression during storage can also affect the browning process, often in a cultivar- or species-dependent manner. In this context, the altered browning kinetics observed in stored quince may reflect a shift in tissue responsiveness and oxidative balance due to storage-induced metabolic adjustments. The above physicochemical conditions can inactivate enzymes that are responsible for flesh browning [73]. Overall, the results support the conclusion that quince is highly susceptible to enzymatic browning, particularly at harvest due to its high PPO activity and phenolic content. However, storage appears to modulate this response, delaying the onset of browning but potentially increasing the sensitivity of the tissue to oxidation over time.

Flesh color difference (ΔΕ) was strong according to Wang et al. [43] on both unbagged and bagged quince fruits in the first five min after fruit cutting and was not affected by the three-month storage (

Table 3. Flesh color difference (ΔΕ) of ‘Afrata Volou’ quince fruit calculated from 0 to 5 and 0 to 20 min after cutting, at harvest, and after three months of storage plus two additional days of shelf-life of unbagged and bagged fruits.

Time	Treatment	ΔE0–5	ΔE0–20
Harvest	Unbagged	6.32 ± 0.54	9.25 ± 0.97 b
	Bagged	7.27 ± 0.72	8.42 ± 0.57 b
3 months storage + 2 d SL	Unbagged	7.94 ± 1.71	13.41 ± 1.25 a
	Bagged	7.07 ± 1.49	14.65 ± 0.98 a
Significance	Time	NS	***
	Treatment	NS	NS
LSD0.05		2.45	2.76

Each value is mean ± SE. Values followed by different letters within each column are significantly different according to the LSD multiple-range test at p ≤ 0.05. NS—non-significant differences; ***—significant differences at p ≤ 0.001.

). Usually, higher ΔΕ means higher enzymatic browning activity [69]. The major flesh ΔΕ was observed from 0 to 20 min after cutting, regardless of the treatment, especially after the three-month storage (Table 3), when the flesh color changed substantially according to the scale of Wang et al. [43]. Our results agree with Najman et al. [17], who mentioned that the most intense change in flesh color to darker shades was observed in the first 30 min after quince fruit cutting and its exposure to the atmosphere. The significant color change in cold-stored fruit after cutting can be attributed to the increase in total tannins, since tannins are also enzymatic browning substrates [66]. Moreover, the effect of cold storage plus shelf-life on the strong increase in quince flesh ΔΕ agrees with previous research on lichi fruit [74]. They found an increase in lipase, phospholipase D, and lipoxygenase (LOX) activities and energy shortage in cold-stored litchi fruit at 3–5 °C, followed by shelf life at 25 °C, which led to decreased membrane integrity and a loss of compartmentalization, causing accelerated browning and quality deterioration.

The browning index (BI) indicates the purity of flesh color and is a useful parameter to follow enzymatic or non-enzymatic browning [43]. BI is more specifically related to the brown coloration than ΔE, as ΔE does not reveal the direction of the color change [69]. The treatment with individual bags did not significantly affect the quince’s flesh color during the time after cutting compared to unbagged fruit (Figure 5). At harvest, flesh browning increased rapidly in both treatments from 0 to 5 min after fruit cutting and remained unchanged thereafter until 20 min after cutting (Figure 5). In contrast, after three months of storage, fruit flesh browning increased gradually from 0 to 15 min after cutting and remained unchanged thereafter in both treatments (Figure 5). Specifically, the increase in flesh BI at harvest was 27.7% for unbagged and 27.3% for bagged quinces. After the three-month storage, this increase reached 77.6% and 70.4% for unbagged and bagged fruit, respectively (Figure 5). Plant organ stress (i.e., physiological stress from prolonged storage) plays an important role in cell content relocation that induces browning of flesh tissues, especially when exposed to atmospheric oxygen [66]. However, unbagged and bagged quince fruits after three months of storage developed less of a brown flesh color (decreased BI values) compared to those at harvest at all time periods measured after cutting (Figure 5). Enzymatic browning was reduced in plant tissues with the decrease in pH [66]; this explains the reduction in bagged fruit flesh browning after three months of storage, since an increase in TA was observed at the same time. Also, the localization of PPO within plant tissues varies depending on the plant species and its stage of growth, i.e., in young apples, PPO is distributed throughout the entire fruit, whereas in mature fruit, it is primarily concentrated around the core [64]. This may contribute to the lower BI after quince storage, when the fruit is more mature compared to the harvest.

3.5. Bruised Fruit Flesh Color Changes with Time After Skin Removal

The flesh color of quince fruit darkened (lower L* values) abruptly from 0 to 10 min after bruising, became darker gradually from 10 to 30 min, and remained almost stable at 40 min after bruising on both treatments at harvest and after three months of storage (Figure 6a). In both treatments, immediately after skin removal, the fruit bruised at harvest or after three months of storage had similar flesh L* values; however, flesh brightness measured from 10 to 40 min after bruising was lower at harvest than after storage (Figure 6a). The flesh of bruised fruit at harvest became darker from 0 to 40 min after bruising by about 30.1% for unbagged fruit and 28.9% for the bagged ones, and after storage by about 17.3% and 23.4% for unbagged and bagged fruit, respectively (Figure 6a). At harvest and after three months of fruit storage, the hue parameter of bruised fruits was not significantly affected by the treatments at all measurement times after skin removal. Flesh hue of the bagged and unbagged fruit bruised at harvest sharply decreased within the first 10 min after skin removal, with a small reduction until 40 min. However, on fruits of both treatments bruised after storage, a significant gradual decrease in the flesh hue parameter from 0 to 20 min after skin removal was observed, while from 20 to 40 min, the decrease continued at a slower rate (Figure 6b).

Bruising is a form of internal tissue damage in fresh produce that occurs without rupturing the skin, typically visible as a discolored area that signals injury beneath the skin. Bruising triggers both physiological and biochemical reactions in the affected tissue, as well as in distant, unaffected cells [62]. Depending on the damage severity, bruises may take up to 12 h to become visible; therefore, they may be only noticeable by consumers at the marketplace or even at the time of consumption [75]. This damage is similar to the cell rupture after fruit cutting described above.

BI of bruised quince fruit flesh was not affected either by treatment or storage when calculated immediately after fruit bruising and skin removal (Figure 7). BI of quince fruit flesh bruised at harvest more than doubled from 0 to 10 min after skin removal and then slightly increased until 40 min at both treatments (Figure 7). In contrast, BI of bruised bagged and unbagged fruit flesh after three months of storage gradually increased from 0 to 40 min after skin removal with lower values compared to fruit bruised at harvest, especially the unbagged ones (Figure 7).

Flesh color difference in the first 10 min after skin removal of bruised fruit after three-month storage under both treatments was significantly lower (by 71.6% and 52.8% on unbagged and bagged fruit, respectively) compared to bruised fruit at harvest (

Table 4. Flesh color difference (ΔE) of bruised ‘Afrata Volou’ quince fruit calculated from 0 to 10 and 0 to 40 min after skin removal, at harvest, and after three months of storage plus two additional days of shelf-life of unbagged and bagged fruits.

Time	Treatment	ΔE0–10	ΔE0–40
Harvest	Unbagged	19.0 ± 1.6 a	27.7 ± 1.3 a
	Bagged	19.7 ± 1.0 a	27.4 ± 1.1 a
3 months storage + 2 d SL	Unbagged	5.4 ± 1.8 b	16.2 ± 2.7 c
	Bagged	9.3 ± 2.2 b	22.3 ± 1.9 b
Significance	Time	***	***
	Treatment	NS	NS
LSD0.05		3.9	4.4

Each value is mean ± SE. Values followed by different letters within each column are significantly different according to the LSD multiple-range test at p ≤ 0.05. NS—non-significant differences; ***—significant differences at p ≤ 0.001.

). According to Wang et al. [43], both unbagged and bagged fruits bruised at harvest had different flesh colors within the first 10 min after skin removal, although fruit bruised after three months of storage showed perceptible and strong ΔE for unbagged and bagged treatment, respectively. Therefore, bruised quince flesh color did not change on stored fruit as much as at harvest, likely due to lower PPO activity after exposure to low temperatures [76]. The highest flesh ΔE of bruised fruit was observed from 0 to 40 min after cutting at harvest, while it decreased for both treatments after storage (Table 4). After three months of storage, flesh ΔΕ of bruised fruit from 0 to 40 min after cutting was higher on bagged fruit compared to unbagged ones (Table 4). Flesh color of bruised fruit from 0 to 40 min after cutting changed significantly according to Wang et al.’s scale [43].

4. Conclusions

Overall, preharvest bagging improved certain aesthetic and chemical aspects of quince fruit, particularly by enhancing skin brightness and maintaining higher acidity. However, it had limited influence on internal traits such as flesh browning and antioxidant activity. Storage had a more pronounced effect, notably slowing the initial progression of flesh browning, likely due to suppression of browning-related enzymes and shifts in phenolic metabolism. Despite this, color changes after cutting became more severe over time in stored fruit, suggesting increased oxidative sensitivity. Additionally, the taste quality indicator (SSC/TA ratio) declined more sharply in bagged fruit after storage compared to unbagged ones, indicating a greater imbalance between sugars and acids that may affect flavor. These findings highlight the complex and distinct impacts of preharvest and postharvest factors on the overall quality of quince fruit.