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Article

Postharvest Quality of Plums Treated with Chitosan-Based Edible Coatings

by
Gabor Zsivanovits
*,
Stoil Zhelyazkov
and
Petya Sabeva
Department of Food Technology, Institute of Food Preservation and Quality, Agriculture Academy, 4003 Plovdiv, Bulgaria
*
Author to whom correspondence should be addressed.
Polysaccharides 2025, 6(3), 68; https://doi.org/10.3390/polysaccharides6030068
Submission received: 25 May 2025 / Revised: 4 July 2025 / Accepted: 30 July 2025 / Published: 7 August 2025
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Versions Notes

Abstract

This study aims to investigate the differences in the effects of spraying and immersing methods on edible coatings for halved and pitted plums. Earlier studies have shown that these biodegradable packaging materials can preserve the quality and safety of fruits for an extended shelf life. Halved and pitted plums (variety Stanley) were treated with chitosan and rosehip oil edible coating emulsions by spraying and immersing methods. The treated series were analyzed by physical, physicochemical, microbiological, and sensorial methods during refrigerated storage for nine days, until the onset of microbiological spoilage. At the beginning of the storage, there was a visible difference between the differently treated samples. The untreated series showed the fastest browning. The emulsion-sprayed samples presented the least changes in color, shape, and volume. A weaker effect of the immersion technique can be explained by a deep standing of the fruits in a treating solution or emulsion. Some of the immersed samples have an aqueous texture and received a smaller sensory rating. The advantages and disadvantages of the methods need further investigation, but on a production scale, spraying can guarantee uniform batches. In laboratory circumstances, immersion is an easier method that does not need expensive and difficult-to-use equipment and gives good results.

1. Introduction

Essential oil-loaded chitosan-based edible films are good alternatives to petroleum-based polymer packaging materials for extending the shelf life of perishable fruits [1]. The roles of the edible coating on the fresh-cut fruits are to slow down ripening, respiration, texture and color changes, and microbiological activity [2]. The addition of essential oil emulsions to chitosan films in low concentrations improves mechanical, physicochemical, antioxidant, and hydrophobic properties, but deteriorates the surface color and in this way reduces the consumer acceptability. The multicomponent films are softer and more stretchable than the pure chitosan films [3]. An increase in the oil concentration increases the antioxidant activity and the hydrophobicity of the films, which is expressed in a decrease in the affinity for water uptake and a change in their surface energy. The surface color and the transparency of the films are optimal at low oil concentration [4]. The evaluated physical and physicochemical properties show the potential of these films to reduce food waste. In addition, active packaging containing natural antioxidants (polyphenols, essential oils, etc.) is a cost-saving alternative that also has the potential to eliminate food safety risks [5].
Rosehip oil is rich in bio-active substances such as essential fatty acids, phytosterols, tocopherols, and carotenoids, and it might have functional benefits such as anti-inflammatory, anti-obesity, anti-oxidant, and anti-diabetic properties, skin protection, and other applications in the culinary, cosmetics, and pharmaceutical industries [6].
The efficacy of the applied edible coatings depends on the fruit surface, the film-forming capacity of the coating material, the adhesiveness of the coating to the surface, and on the method of application of the coating as well [7]. The most favored methods of applying coatings are immersing, spraying, and brushing [8]. Immersion is the simplest way, a suitable method for food materials with complex or rough surfaces like fruits, but the longer period in the coating solution can cause softening if too much water is diffused through the pores [9]. The other drawback to that technique is the need for a bigger amount of coating solution and the possibility of contamination from the other fruits. These problems create a barrier to the scaling up of that method for industrial use [10]. Brushing or spreading is useful for high-viscosity coating solutions, but the mechanical contact with the brush can easily damage the sensitive fruit surface or convey spoilage between the fruits [11]. Spraying is capable of forming a uniform coating layer on the surface of the fruits. The thickness and consistency of the layer depends on the size and distribution of the drops. It requires a coating solution with low viscosities [12]. That technique is easily scalable to industrial processes but it requires a more precise and expensive technique [13]. The choice between different methods should be based on the type of fruit and its sensitivity, the properties of the coating solution, production scale, and desired coating performance. Therefore, careful comparison of each individual system for coating the fruit helps ensure efficacy, cost-effectiveness, and fruit quality, making it a key decision point in postharvest handling and food processing.
Based on the results of our earlier study, incorporation of rosehip oil emulsion up to 3% in water-soluble chitosan is optimal for application as an edible coating on minimally processed fruits [14]. That study showed the optimization of the concentration of rosehip oil emulsion in water-soluble chitosan model film, resulting in mechanical and barrier properties. The present paper shows an application of this coating with two different methods (immersing and spraying) in the short storage of halved and pitted plum fruits. It aims to compare the two coating methods and determine which one is more suitable for better preserving minimally processed plums.

2. Materials and Methods

Fruits: fresh plums (Prunus domestica, cv. ‘Stanley’, average fruit weight 37.8 ± 7.1 g) were harvested in full maturation [15], in 2023, in the Fruit Growing Institute—Plovdiv, Agricultural Academy of Bulgaria.
Coating materials: Chitosan hydrochloride (fungal origin, water-soluble, viscosity of 1% solution: 10–120 cps, degree of deacetylation: >85%) was purchased from Glentham Life Sciences Ltd. (Corsham, UK). Rosehip seed oil was produced by Green Gold International Ltd. (Plovdiv, Bulgaria) [16,17].
All of the other chemicals used in this experimental series were provided by Bulgarian distributors of international chemical companies with analytical grades.

2.1. Preparing the Coated Sample Series

The halved and pitted plums were treated by chitosan solution (chitosan 1%—Ch) and chitosan–rosehip oil emulsion (chitosan 1% + rosehip oil emulsion 3%—Ch_Rh) by immersion (Im) and spraying (Spray) from both sides and air-dried for 15 min [18]. The uncoated (UC) series was also refrigerated for comparison. Five trays were prepared from each treatment for further experiments. The fruit series were refrigerated at 4 ± 1 °C for 9 days until the onset of microbiological spoilage. The quality and safety parameters of the series were checked on the 1st, on the 5th, and on the 9th day.

2.2. Determination of the Physical Quality

2.2.1. Control of the Visual Disorders

A visual control was used to pick out the unhealthy or shape-changed fruit pieces before quality control. The percentage of the chosen pieces shows the losses [19,20,21].

2.2.2. Physiological Weight Loss

The series of halved plums (one series from each treatment, 30 halves of plums) were stored in an identified position and weighed on all measurement days to follow the weight loss. It is expressed in the percentage loss of the initial weight [22].

2.2.3. Surface Color Evaluation

The color parameters were determined using a colorimeter PCE-CSM 5 (PCE Deutschland GmbH, Meschede, Germany)—calibrated against a white calibration plate L* = 94.3; a* = −0.92; b* = −0.67, measuring geometry of 8°/d, Ø 8 mm, light source D65). The CIELAB color parameters L*, a*, b*, and c* were measured and ΔE* was calculated [23,24] for the different treated series between the 1st and 5th or 9th day.
∆ E * = ∆ L * 2 + ∆ a * 2 + ∆ b * 2
where:
∆ L * = L i * − L 0 * ; ∆ a * = ∆ a i * − ∆ a 0 * ; ∆ b * = ∆ b i * − ∆ b 0 * ;
0 = value at the 1st day; i = value at the 5th or 9th day.
The purpose of the use of ΔE* is that this parameter describes the differences arising during the shelf-life time. Based on the literature, it can be connected to the perceptual sensory color scale: trace level difference ΔE* = 0–0.5, slight difference ΔE* = 0.5–1.5, noticeable difference ΔE* = 1.5–3.0, appreciable difference ΔE* = 3.0–6.0, large difference ΔE* = 6.0–12.0, very obvious difference ΔE* > 12.0.
One tray (30 pieces, from both sides) of fruits was measured.

2.2.4. Texture Parameters

Fifteen fruits were examined by a slow puncture test with a TA.XT2 Texture Analyser (Stable Micro Systems, Surrey, UK). A 5 mm cylindrical probe was used to measure the firmness. The loading speed was 1 mm·s−1. The yield stress, the Young’s modulus, and the rupture stress were used for future evaluation [25].

2.3. Analysis of the Antioxidant Activity

The complex antioxidant capacity [26] was determined by free radical scavenging activity (DPPH) and ferric reducing antioxidant power (FRAP) assay. The total polyphenol content (TPP) was detected by the spectrophotometric method [27]. These parameters were analyzed in 3 repetitions.

2.4. Safety Parameters

The microbiological safety of the samples was controlled (3 samples from one series) on the days of the sensory tests and used also for the establishment of the endpoint of the shelf-life period. To ensure fruit safety, total plate counts (BS EN ISO 4833-1: 2013) [28], molds and yeasts contamination (BS ISO 21527-2: 2011) [29], food-borne pathogens—Escherichia coli (BS ISO 16649-2: 2014) [30], and coliforms with colony-count technique (BS ISO 4832:2006) [31], Salmonella (BDS EN ISO 6579-1:2017/Amd 1:2020) were detected [32].

2.5. Sensory Analyses

The sensory quality tests were conducted by 15 volunteers aged between 20–50 years, on randomly numbered samples on the same days as the other experiments. Appearance, shape and size, color, fruit taste, aroma, firmness and cut surface were the evaluated attributes with a 9-point hedonic acceptance scale [33,34]. The non-coated (NC) samples were not subjected to analysis on the last day because of damaging.

2.6. Statistical Analysis of the Data

The measured results were statistically analyzed by the ANOVA function [35] of Statistica software (TIBCO Software Inc. ver. 14, Palo Alto, CA, USA).

3. Results and Discussion

3.1. Visual Changes During the Storage

The fresh plum halves showed differences depending on the treatment method, dipping or spraying, and the treatment material—uncoated, treatment with chitosan solution, or chitosan and rosehip oil emulsion (Figure 1).
During storage, the uncoated samples showed the greatest change in shape, volume, and color (browning). Halves with visible microbiological spoilage were removed from the series. By the fifth day, the treated samples had no significant change in shape and volume, but the sprayed samples maintained their lighter color. The least color changes were observed in the emulsion-coated samples. In immersed samples, diffusion of the solution or emulsion may cause tissue flooding on the pulp side. A thin layer is expected to form on the surface of the sprayed samples, which protects them from losses.
On day 9, the control samples were no longer suitable for consumption. The shape and volume of the halves no longer resembled those of fresh fruit. The coating still preserved to varying degrees the freshness of the fruit. Spoilage losses, changes in shape and volume were the least for samples that were sprayed with an emulsion coating. It can be explained by the different water-resistance ability of the coating layer [36]. The least browning was observed in these samples. The results of visual losses are in correlation with the visual quality changes in tomatoes described by Thumula (2006), for chitosan–lysozyme-film-coated tomatoes [37] and for wrinkling and color changes in ghost chili fruits with chitosan and essential oil-based coatings by Kalita et al. (2024) [38].

3.2. Weight Loss During Storage

During storage, fruits lose a part of their weight because of respiration. That activity can be controlled by edible coatings. The barrier activity of the coating depends on its components. The largest loss was shown by the uncoated samples (Figure 2). The chitosan-based coatings saved the fruit halves. The weight loss of the samples with immersion in a chitosan–rosehip oil combination was significantly different from the effect of the pure chitosan coating applied by immersion, which can be explained by the hydrophobic effect of the rosehip oil component. However, it was without differences from the chitosan applied by a spray technique, maybe because this produces a film with more uniform thickness [39]. The smallest waste was detected on the chitosan–rosehip oil sprayed series. Similar results were reported by Meng et al. (2008) [40] on chitosan-coated table grapes. Other authors also reported a significant reduction in the weight loss for different fruits and vegetables with similar coatings [41].

3.3. Changes in the Color Parameters

Color change depends on the storage time and the treatment method, and can be evaluated by the values and significance of the total color difference (ΔE*—Figure 3).
On the peel side of the half plums, the biggest change was observed for the uncoated fruits, where, on the fifth day, there was already a visible change. By the end of the storage period, the shape changed, and the color became darker, with large differences. For the treated fruits up to the fifth day, the change in the fruits that were sprayed with chitosan solution or with an emulsion from water-soluble chitosan and rosehip oil was insignificant. A similar slight change was observed for the samples coated by the other methods. At the end of the storage, the changes increased to the smallest extent in the sprayed fruit. In contrast, immersed fruits showed already significant differences. Spraying of the coatings supports the faster formation of a thin layer on the surface of the fruit, and the oil content of the emulsions reduces the permeability of gas and water vapors. On the fleshy side of the fruit, the trends are similar, but the changes were more significant. On the fleshy side, this change was expressed as browning. This process was the fastest and with the greatest changes in the uncoated fruits. The dipped fruits on the fifth day already showed visible changes.
The samples immersed in chitosan solution showed very similar values on both sides at the end of the storage. Sprayed fruits showed slight changes up to the fifth day. At the end of the storage, the differences increased, and visible differences remained only in the fruits sprayed with an emulsion of water-soluble chitosan and rosehip oil, because the oil improved the barrier properties of the thin film formed. The effect of other coating methods was weaker, and the differences are significant. The weaker effect of the immersion method can be explained by a longer stay of the fruits in the treatment media. In the case of sprayed fruits, the treatment solution or emulsion forms a thin film on the surface in a short time, which is the reason for better color protection. Based on other authors, alginate coatings also delayed the color changes by retarding postharvest ripening [42]. Similar results were obtained with minimally processed peaches [43] and melons [44]. Similar results of color change have been observed in other groups working with cherries and polyvinyl alcohol and chitosan composite films, which found smaller changes in packaged fruits compared to unpackaged ones over a storage period of 15 days [45].

3.4. Changes in the Texture Parameters

Changes in texture are complex, due to the drying of the fruits and, on the other hand, to the rupture of the cell wall and the destruction of the cells [46]. Textural parameters show the different sensitivity of fruits to coating composition and changes during refrigerated storage. Water content plays a crucial role in determining the plum’s mechanical properties. Edible coatings limit water loss and thus reduce the change in yield stress and hardness. Controlling the water content, water-vapor barrier properties, and hydrophobicity of the studied coatings is essential for designing effective packaging materials that can extend shelf life, maintain quality, and ensure the safety of coated products [47]. The incorporation of Rh into the polymer matrix resulted in a decrease in the equilibrium moisture content, indicating improved water resistance. This phenomenon can be attributed to the reduced availability of amino groups in chitosan, probably due to electrostatic neutralization with the carboxylate groups present in Rh. Similar observations were made by Butnaru et al. (2019) [48] for chitosan–rosehip oil films, and Pereda et al. (2012) [49] for chitosan–olive oil coatings. In summary, the addition of Rh emulsion reduces the water binding sites and improves the hydrophobic properties of the coatings. Additionally, the coating components and the treating methods contribute significantly to the fruit’s hardness, influencing their texture. To analyze the texture, yield and rupture stress, as well as the Young’s modulus, were assessed (Figure 4). The yield stress of the uncoated plums was without any change during the shelf-life time. The film-forming ability of the applied coatings can explain the slight increase in the yield stress on the first day. That increase depended on the composition of the coating and on the coating method as well. There were no changes with Ch_Rh_Spray coating. Most likely, these samples had the most uniform coating. During storage, the yield stress at first decreased, maybe because the high water content burst the cells. After that, the wrinkled and partly damaged fruit pieces could be dried to a chewier consistency which caused a larger increase in that parameter. Just the sprayed emulsion coating showed a slow but tendentious increase. On the pulp side, the UC probes showed a high increase as a result of the drying. The consequences of the coatings are unclear [50].
The coatings form a thin film layer, which makes the surface of the fruits harder, reducing the respiration and the intensity of evaporation. The coatings increase the hardness of the fruits at the beginning of the shelf-life period (Figure 5). The improved firmness of the coated fruits is due to the better uniformity of the sprayed coating [51] and the delay in cell wall hydrolysis [52]. The changes in the yield stress and the hardness are very similar, but the effects of the coatings are hard to explain [53].
The increase in hardness parameters may result in the inelastic cuticle surface and shriveled appearance of the fruits [54]. That increase is smaller for the plums coated with rosehip oil emulsion. The elasticity of the uncoated fruits decreased during storage (Figure 6) [55]. The fruit halves became plastic with a rubbery texture.
The coated samples show a higher, but also decreasing, tendency, and just the sprayed rosehip emulsion-coated series preserved its elasticity during refrigeration. The decrease in the texture parameters is the result of cell-wall enzyme activity, which can be controlled by the coating solutions. The level of maintenance depends on the components and the other circumstances of the coating as well [56].
Changes in firmness and elasticity mean loss of freshness of the fruit and affect the appearance and sensory acceptance by consumers. The results obtained show better preservation of the fruit’s freshness when coated in edible packaging during refrigerated storage.

3.5. Changes in the Antioxidant Activity

Plums are a good source of natural antioxidants. Minimal processing reduces the antioxidant activity of uncoated and chitosan-coated plums (Figure 7). The area and the disposition of the triangles show the complex changes on the radar diagrams.
The coating components added their antioxidant activity but could not control the decrease in their values. The differences and the changes in the antioxidant activity of the sample were small and barely significant. The amount of polyphenols increased relatively, but this was a result of drying the samples. The decrease in the antioxidant activity was the highest for the uncoated samples [57]. The best preservation of antioxidant capacity and total polyphenol content is seen for the samples coated by spraying with chitosan/rosehip emulsion [58]. Similar results were received for maintenance of the antioxidant capacity by Panahirad et al. [59] for plums coated with blended carboxymethylcellulose and pectin-based coatings. That result can be explained by the strong enzyme-activity delaying effect and barrier properties of the applied coatings [60].

3.6. Changes in the Safety Parameters

The fruit safety control was the determining parameter for the shelf-life time (Table 1). The detected number of total microorganisms, molds and yeasts was below the standard limited values. Safety-critical food-borne pathogens were not detected during the storage period [61]. The uncoated samples lost their safety during the 5th day. The coatings preserved the fruits from microbiological contamination in different measures [62]. In the case of plums without coating and with pure chitosan coating, the difference after coating of the fruit is visible—chitosan limits the development of molds and yeasts and significantly reduces the total number of microorganisms in the fruit samples. The results of immersing and spraying at the packaging stage do not differ in the considered indicators. The smallest spoilage losses are seen on the emulsion-sprayed samples [63]. The reported result could be due to the antimicrobial nature of the chitosan against Gram-positive and Gram-negative bacteria [64] and enhancement of it by the essential oil [65]. Coating with Ch_Rh emulsion gave higher spoilage results in total microbial count data compared to a pure Ch coating, but the values were lower than the control. For molds and yeasts, rosehip emulsion packaging limited their development, proving that it managed to preserve them in both coating options (immersion and spray) better than grape emulsion [66]. Spraying results were significantly better than immersing the fruit. For the coating with chitosan, the total number of microorganisms increased in 5 days up to 2 times in the immersed samples, and in the sprayed ones there was an increase, but it was smaller. Molds and yeasts were at low levels during this period—chitosan managed to suppress their growth and development.
This has also been proven by other authors and teams who have worked with chitosan coatings on various fruits: cherry tomatoes, strawberries, papaya, and apples [67]. Coating with chitosan and rosehip oil gives the most stable result when spraying—there are minimal changes in the values, which is due to the good preservation of the rosehip oil from the development of microorganisms.
After 9 days of storage, the samples without coating significantly increased the level of microorganisms, making them unfit for consumption. This was also confirmed by their appearance (darkened, wrinkled).
Coating with chitosan by immersion for 9 days also did not give satisfactory results for the total number of microorganisms, molds and yeasts. With chitosan applied by spraying, the results were significantly better, as it managed to preserve minimally processed fruits well.
The emulsion packaging with chitosan and rosehip oil gave the best results by the end of the test. The variant with spraying had the lowest recorded number of microorganisms for the entire period. Molds and yeasts developed at low levels. This indicates good preservation of the fruits from this coating in both methods. For the emulsion with chitosan and grape seed oil, in the earlier study, high values were established by immersion [68].
The application of essential oils, by spraying and steam application, has been proven by other groups to preserve the quality and limit the development of molds in grapes during refrigerated storage [69]. Despite the increase in the result, the data are within acceptable values for chilled, minimally processed fruits (total number of microorganisms < 10,000 cfu/g; molds < 5000 cfu/g) [70].

3.7. Sensory Analysis of the Samples with Different Treatment Types

The storage time and the packaging type significantly affected the assessed sensory characteristics (Figure 8). Among the sensory quality indicators, the appearance was best preserved throughout the storage period when the fruits were sprayed with chitosan/rosehip oil emulsion (Ch_Rh_Spray).
The greatest deterioration of these indicators of the treated samples is seen when spraying with chitosan solution was applied (Ch_Spray). Color acceptation was the least changed by immersion treatment with chitosan solution (Ch_Rh_Im). The evaluation of these indicators is variable for other packages; it is highest for chitosan solution and emulsion. The consistency was best preserved when plums were immersed in chitosan/rosehip emulsion (Ch_Rh_Im). The taste and odor acceptance was the best for the entire storage time with Ch_Rh_Spray.
The sweetness rating was variable, and most likely depended on the water content of the fruit. The reduction in astringency was the least for the samples immersed in chitosan/rosehip oil emulsion (Ch_Rh_Im treatment). The retention of juiciness was about the same for different coatings and methods.
The influence of the storage time in evaluating quality indicators depends on subjective external factors, such as the memory of the consumers of fresh fruit. On the first day, consumers rated the uncoated samples the highest and could not differentiate between the different coated samples (Figure 9).
During storage, uncoated fruits lost their sensory quality the fastest and to the greatest extent. On the 5th day, they obtained the lowest scores. From the treated samples, the immersed samples and the samples sprayed with chitosan solution (Ch_Im, Ch_Spray, Ch_Rh_Im) received almost the same ratings from the evaluators. The highest scores were for the samples sprayed with chitosan/rosehip oil emulsion (Ch_Rh_Spray) with a significant difference compared to the other samples. On the 9th day, the uncoated samples were no longer suitable for consumption and were not tested. From the coated fruits, those treated by dipping or spraying with a chitosan solution lost their sensory qualities to the greatest extent. Treatment with oil emulsions showed significantly better results.
The applied coatings preserved the safety and quality of the halved and pitted plum fruits for a maximum of 9 days.
Similar results are described for maintaining the sensory attributes by Won et al. (2018) [71] for plum fruits coated with essential oil-loaded hydroxypropyl methylcellulose.

4. Conclusions

The results confirm that both immersing and spraying with edible coatings based on chitosan and rosehip oil improve the storage stability of halved and pitted plums during refrigerated storage for up to 9 days. However, the investigated parameters show differences depending on the treatment method. Weight loss in Ch_Rh_Spray samples remains below 30% by day 9, compared to 50% in uncoated samples. The total color change (ΔE) on the pulp side of Ch-Rh coated fruits is below 4, indicating only a “noticeable” difference, while uncoated samples exceeded 12—classified as a “very obvious” change. Young’s modulus remains above 3.0 MPa in Ch_Rh_Spray samples, while dropping below 1.5 MPa in the uncoated control. The parameters investigated show differences between the immersion and spraying treatments. Sensory evaluation showed the highest overall acceptance scores for Ch_Rh_Spray samples, scoring over 7.5 out of 9, whereas other treatments scored below 5, and uncoated fruits were disqualified from testing after day 5. Based on the results obtained, one can conclude that the spraying method using a chitosan and rosehip oil emulsion (Ch_Rh_Spray) showed the most effective performance across physicochemical, microbiological, and sensory parameters. While immersion is an easy-to-apply method in laboratory settings and yields satisfactory results, for industrial applications, the spraying of chitosan–rosehip oil emulsions is more suitable. It ensures more uniform coating, lower moisture loss, better color and texture retention, and enhanced microbiological safety, making it the preferred method for preserving the quality and safety of minimally processed plums.

Author Contributions

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

Funding

This research was funded by the Agricultural Academy of Bulgaria, project № TN 14: “Influence of bioactive edible packaging on the quality of fruits and vegetables during storage (2022–2024)”.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the corresponding author on request.

Acknowledgments

The authors thank the Agricultural Academy of Bulgaria and for the Institute of Food Preservation and Quality, Plovdiv, for providing access to the scientific infrastructure and sophisticated equip-ment for this work. The authors also thank the Fruit Growing Institute–Plovdiv, Agricultural Academy of Bulgaria for providing free fruits for the experiments.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
UCUncoated samples
ChSamples coated with chitosan solution
Ch_ImSamples coated with chitosan solution by immersion method
Ch_RhSamples coated with chitosan and rosehip oil emulsion
Ch_Rh_ImSamples coated with chitosan and rosehip oil emulsion by immersion method
Ch_spraySamples coated with chitosan solution by spraying method
Ch_Rh_SpraySamples coated with chitosan and rosehip oil emulsion by spraying method

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Figure 1. Changes in the immersed and sprayed samples during storage.
Figure 1. Changes in the immersed and sprayed samples during storage.
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Figure 2. Weight loss of the samples during storage (a–d: different letters show the statistical differences between the treatments at the same day, p < 0.05).
Figure 2. Weight loss of the samples during storage (a–d: different letters show the statistical differences between the treatments at the same day, p < 0.05).
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Figure 3. Changes in the total color differences (a–e: different letters show the statistical differences between the treatments on the same day, p < 0.05).
Figure 3. Changes in the total color differences (a–e: different letters show the statistical differences between the treatments on the same day, p < 0.05).
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Figure 4. Yield stress changes during refrigerating (lower case a–d: different letters show the statistical differences between the treatments on the same day; upper case A–C: different letters show the statistical differences between the days with the same treatment, p < 0.05).
Figure 4. Yield stress changes during refrigerating (lower case a–d: different letters show the statistical differences between the treatments on the same day; upper case A–C: different letters show the statistical differences between the days with the same treatment, p < 0.05).
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Figure 5. Rupture stress changes during refrigerating (lower case a–d: different letters show the statistical differences between the treatments on the same day; upper case A–C: different letters show the statistical differences between the days with the same treatment, p < 0.05).
Figure 5. Rupture stress changes during refrigerating (lower case a–d: different letters show the statistical differences between the treatments on the same day; upper case A–C: different letters show the statistical differences between the days with the same treatment, p < 0.05).
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Figure 6. Young’s modulus changes during refrigerating (lower case a–d: different letters show the statistical differences between the treatments on the same day; upper case A–C: different letters show the statistical differences between the days with the same treatment, p < 0.05).
Figure 6. Young’s modulus changes during refrigerating (lower case a–d: different letters show the statistical differences between the treatments on the same day; upper case A–C: different letters show the statistical differences between the days with the same treatment, p < 0.05).
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Figure 7. Antioxidant activity changes during refrigerating.
Figure 7. Antioxidant activity changes during refrigerating.
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Figure 8. Sensory parameter changes during refrigerating.
Figure 8. Sensory parameter changes during refrigerating.
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Figure 9. General acceptation based on the area of the sensorial diagram.
Figure 9. General acceptation based on the area of the sensorial diagram.
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Table 1. Microbiological spoilage during the storage period.
Table 1. Microbiological spoilage during the storage period.
Storage DayCoating TypeTotal Number of
Microorganisms		Number of Molds and Yeasts
1st dayUC9.0 × 1012.5 × 101
Ch_Im1.0 × 101<10
Ch_Rh_Im6.5 × 101<10
Ch_spray1.0 × 101<10
Ch_Rh_Spray1.5 × 101<10
5th dayUC1.2 × 1031.2 × 102
Ch_Im2.5 × 1021.0 × 101
Ch_Rh_Im2.2 × 1034.0 × 102
Ch_spray7.0 × 101<10
Ch_Rh_Spray6.0 × 101<10
9th dayUC6.0 × 1031.0 × 103
Ch_Im9.0 × 1031.2 × 102
Ch_Rh_Im4.7 × 1038.5 × 102
Ch_spray1.0 × 1031.0 × 101
Ch_Rh_Spray1.8 × 1031.0 × 101
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Zsivanovits, G.; Zhelyazkov, S.; Sabeva, P. Postharvest Quality of Plums Treated with Chitosan-Based Edible Coatings. Polysaccharides 2025, 6, 68. https://doi.org/10.3390/polysaccharides6030068

AMA Style

Zsivanovits G, Zhelyazkov S, Sabeva P. Postharvest Quality of Plums Treated with Chitosan-Based Edible Coatings. Polysaccharides. 2025; 6(3):68. https://doi.org/10.3390/polysaccharides6030068

Chicago/Turabian Style

Zsivanovits, Gabor, Stoil Zhelyazkov, and Petya Sabeva. 2025. "Postharvest Quality of Plums Treated with Chitosan-Based Edible Coatings" Polysaccharides 6, no. 3: 68. https://doi.org/10.3390/polysaccharides6030068

APA Style

Zsivanovits, G., Zhelyazkov, S., & Sabeva, P. (2025). Postharvest Quality of Plums Treated with Chitosan-Based Edible Coatings. Polysaccharides, 6(3), 68. https://doi.org/10.3390/polysaccharides6030068

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