Method for enhancing air permeability of fruit peel by using gamma-aminobutyric acid

Abstract

The invention belongs to the technical field of postharvest physiology and preservation of fruits and vegetables, and particularly relates to a method for enhancing the air permeability of fruit peels by using gamma-aminobutyric acid. Gamma-aminobutyric acid is utilized to enhance the air permeability from the upstream, the internal gas environment of the fruits is actively optimized, and the effect of improving the storage quality of the fruits is achieved by adopting a pre-harvest spraying mode, a post-harvest soaking mode and a post-harvest soaking and waxing mode. The result of the embodiment shows that the method has a definite, stable and universal effect on enhancing the air permeability of the citrus fruit peel, and the effect is not influenced by the treatment opportunity, the treatment mode and the subsequent post-harvest treatment link. In addition, the method further has the positive effect of promoting color change, and the appearance and commodity quality of the fruits are further improved.

Description

Technical Field

[0001] This invention belongs to the field of postharvest physiology and preservation technology of fruits and vegetables, specifically relating to a method for enhancing the air permeability of fruit peel using γ-aminobutyric acid. Background Technology

[0002] Citrus fruits, as a globally important economic crop, often suffer from quality deterioration and rot during post-harvest storage and transportation due to factors such as water loss, aging, physiological disorders, and diseases, resulting in economic losses. The key to solving this problem lies in adopting effective preservation measures, which fundamentally depend on regulating the physiological metabolic activities that continue after harvest. These metabolic processes, especially respiration, are highly dependent on the continuous exchange of O2 and CO2 between the fruit's interior and the external environment. The peel, as the only physical interface for this gas exchange, directly affects the efficiency of gas exchange, thus determining the balance of the fruit's internal microenvironment, metabolic rate, and storage quality and shelf life. Excessive permeability accelerates water loss and aging, while insufficient permeability easily leads to internal hypoxia and CO2 accumulation, causing physiological disorders such as anaerobic respiration.

[0003] Currently, mainstream fruit and vegetable preservation technologies mainly focus on coatings (such as wax liquids and chitosan), physical treatments (such as heat shock and ultraviolet irradiation), and the application of chemical regulators (such as calcium treatment and 1-methylcyclopropene). These methods primarily delay quality decline by inhibiting respiration, sterilizing, or forming physical barrier layers. Their mechanisms of action tend to reduce gas exchange rather than actively and precisely improving the permeability of the fruit peel. Therefore, there is still a lack of targeted technologies on how to safely and effectively improve the permeability of the fruit peel to optimize the internal gas composition and alleviate related physiological stresses, which represents a significant gap in the existing preservation system.

[0004] γ-Aminobutyric acid (GABA), as a naturally occurring non-protein amino acid, is a safe and bioactive natural substance. Current technologies mainly focus on its application in regulating organic acid metabolism, inhibiting decay, and delaying aging. There are no related technologies for its direct use in systematically regulating the permeability of fruit peel to improve the internal gas microenvironment of fruit.

[0005] In conclusion, developing a new method to enhance fruit permeability is of great practical significance for improving the postharvest preservation system. Summary of the Invention

[0006] The purpose of this invention is to provide a method for enhancing the permeability of fruit peel using γ-aminobutyric acid (GABA). The method provided by this invention can actively and safely enhance the permeability of fruit peel, thereby optimizing the internal gas microenvironment, delaying post-harvest senescence, and improving storage quality.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for enhancing the air permeability of fruit peel, the method comprising: pre-harvest treatment and / or post-harvest treatment of the fruit using γ-aminobutyric acid (GABA);

[0009] The pre-harvest treatment includes pre-harvest spraying treatment, the specific steps of which are: starting from the fruit color-changing period, spray the tree and fruit with a 1-50 mM GABA aqueous solution, with a spraying interval of 20-30 days, spraying 1-5 times, and harvesting after the last spraying.

[0010] The postharvest treatment includes postharvest soaking treatment, the specific steps of which are: soaking the harvested fruit in a 0.1-10 mM GABA aqueous solution for 1-10 minutes.

[0011] Preferably, the concentration of the GABA aqueous solution used for pre-harvest spraying is 5-20 mM, the spraying interval is 15-25 days, and a total of 2-4 times are applied.

[0012] Preferably, the concentration of the GABA aqueous solution in the postharvest soaking treatment is 0.5-5 mM, and the soaking time is 2-5 minutes.

[0013] Preferably, the post-harvest treatment further includes: applying a wax coating after the post-harvest soaking treatment.

[0014] Preferably, the post-harvest treatment further includes: bagging each fruit individually with polyethylene film after post-harvest soaking treatment.

[0015] Preferably, the fruit is a citrus fruit.

[0016] Preferably, the citrus fruit is of the variety of Wenzhou mandarin orange, Wogan mandarin orange, Murcott mandarin orange, or Satsuma mandarin orange.

[0017] The present invention also provides a storage method, the method comprising: treating the fruit using the above method and then storing it, wherein the storage conditions are a temperature of 20±2℃ and a relative humidity of 55-70%.

[0018] The present invention also provides the application of the above-mentioned method for enhancing the air permeability of fruit peel in promoting fruit color change.

[0019] The beneficial effects of this invention are:

[0020] This invention reveals for the first time that GABA has a novel physiological function of directly enhancing the permeability of fruit peel, which breaks through the traditional understanding of its preservation effect by those skilled in the art and provides a new target for postharvest physiological regulation.

[0021] This invention is an innovative technology based on GABA to enhance the permeability of the fruit peel, providing a novel technical approach to improve storage quality by optimizing gas exchange pathways. Specifically, it enhances permeability from upstream, actively optimizing the internal gas environment of the fruit, laying a physiological foundation for maintaining normal aerobic metabolism and delaying aging, thus representing a more fundamental preservation strategy. This strategy offers a particularly effective solution for citrus varieties (such as Wogan and Murcott) whose poor permeability is due to their compact peel structure.

[0022] This invention complements and enhances existing technologies, and is particularly suitable for commercial waxing applications. GABA pretreatment effectively improves the overall air permeability of the peel composite system after waxing, mitigating the risks of internal hypoxia and metabolic disorders that may be caused by the coating while retaining the advantages of the coating. It is an important supplement and improvement to existing preservation technologies and concepts. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The effects of GABA treatment on the appearance, peel gas permeability, and weight loss of Wenzhou mandarin oranges were investigated. A: Fruit appearance and cross-section (scale bar = 3 cm); B: Peel gas permeability; C: Fruit weight loss. Data were analyzed using a two-tailed Student's t-test. Significance levels were defined as: *P<0.05, **P<0.01, ***P<0.001. Values ​​in the figures are mean ± standard error (n≥8 biological replicates).

[0025] Figure 2 To investigate the effects of GABA pretreatment on the appearance, peel gas permeability, and internal oxygen partial pressure of wax-coated Satsuma mandarins, the following data were analyzed: A: Fruit appearance and cross-section (scale bar = 3 cm); B: Peel gas permeability (Note: 0 d corresponds to the peel gas permeability of the fruit before treatment); C: Internal oxygen partial pressure of the fruit (Note: 0 d corresponds to the internal oxygen partial pressure of the fruit before treatment). Data were analyzed using a two-tailed Student's t-test, with significance levels defined as: *P<0.05, **P<0.01, ***P<0.001; values ​​in the figures are mean ± standard error (n≥8 biological replicates).

[0026] Figure 3The study investigated the effects of GABA pre-harvest treatment on fruit appearance, color difference index (CCI), and peel gas permeability in Murcott, Orah, and Shatang citrus varieties. A: Fruit appearance and cross-section (scale bar = 4 cm); BD: Color difference index (CCI) of Murcott, Orah, and Shatang fruits; EG: Peel gas permeability of the corresponding varieties. Data were analyzed using a two-tailed Student's t-test. Significance levels were defined as *P < 0.05, **P < 0.01, and ***P < 0.001. Values ​​are presented as mean ± standard error (n ≥ 8 biological replicates). Detailed Implementation

[0027] Unless otherwise specified, the production processes, experimental methods, or testing methods involved in the embodiments of this invention are all conventional methods in the prior art, and their names and / or abbreviations are all conventional names in the field, which are very clear and distinct in the relevant application areas. Those skilled in the art can understand the conventional process steps based on the names and apply the corresponding equipment, and implement them according to conventional conditions or conditions recommended by the manufacturer.

[0028] The various instruments, equipment, raw materials or reagents used in the embodiments of this invention are not subject to any special restrictions on their source. They are all conventional products that can be purchased through regular commercial channels and can be prepared according to conventional methods known to those skilled in the art.

[0029] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1

[0031] 1. Materials and Methods

[0032] Wenzhou mandarin oranges (Citrus unshiu Marc.) were harvested from commercial orchards in Yichang City, Hubei Province. Fruits of uniform size and color, without obvious defects or mechanical damage, were selected. They were treated with a 0.5 mM GABA aqueous solution for 5 minutes, then naturally air-dried and individually bagged with polyethylene film. The treated fruits were stored at 20 ± 2 ℃ and 55-70% relative humidity, and indicators such as peel gas permeability were measured at predetermined time points.

[0033] 2. Test Results

[0034] Fruit appearance and coloring: During storage, both groups of fruits showed a gradual deterioration in appearance and internal structure. Towards the later stages of storage, the fruit treated with GABA exhibited significantly better coloring than the control group. Figure 1 A).

[0035] Pericarp gas permeability: GABA treatment showed a significant effect on pericarp gas permeability in the early stages of storage. Measurements on days 5 and 10 showed that the pericarp gas permeability of the GABA-treated group was significantly higher than that of the control group, being 1.3 times and 1.4 times higher, respectively. Figure 1 B). Subsequently, the osmotic rate of both groups of fruits continued to increase, reaching a peak around day 15 (3.2–3.5 μmol·s⁻¹). -1 ·m -2 ·Pa -1 At this point, there was no significant difference between the two groups. Figure 1 B).

[0036] Fruit weight loss rate: Throughout the storage process, the fruit weight loss rate in the GABA-treated group was consistently significantly lower than that in the control group. Figure 1 C). This indicates that GABA treatment not only effectively increases the gas permeability of the pericarp at specific stages, but also helps to inhibit water loss from the fruit, thereby synergistically maintaining postharvest quality.

[0037] 3. Conclusion

[0038] In summary, this embodiment demonstrates that the technique of soaking the fruit in a 0.5 mM GABA aqueous solution for 5 minutes significantly improves the gas permeability of the peel in the early stages of storage, thereby promoting gas exchange in the fruit. Simultaneously, this method maintains a lower fruit weight loss rate throughout the entire storage period, effectively inhibits moisture loss, and promotes the fruit's color change process. The synergistic effects described above in improving permeability, retaining moisture, and promoting color change are significantly effective in maintaining the post-harvest quality of citrus fruit and extending its shelf life.

[0039] Example 2

[0040] 1. Materials and Methods

[0041] Wenzhou mandarin oranges were harvested from commercial orchards in Yichang City, Hubei Province. Fruits of uniform size and color, without obvious visible defects or mechanical damage, were selected and randomly divided into two groups: the experimental group (GABA+Wax) was treated with a 0.5 mM GABA aqueous solution for 5 minutes, naturally air-dried, and then manually coated with commercial Xianliang 402D fruit wax; the control group (CK+Wax) was treated with deionized water for 5 minutes, followed by the same waxing procedure as the experimental group. After treatment, the fruits were stored at 20±2 ℃ and 55-70% relative humidity. The gas permeability of the peel and the partial pressure of oxygen inside the fruit were measured at preset time points.

[0042] 2. Test Results

[0043] Fruit appearance and coloring: compared with unwaxed fruit ( Figure 1A) Waxing significantly improved the gloss of the fruit surface, but the appearance and internal structure of both groups of waxed fruits deteriorated with prolonged storage. Figure 2 A). It is worth noting that the promoting effect of GABA pretreatment on fruit coloring remained significant in waxed fruits: in the later stages of storage, the coloring degree of the experimental group was significantly better than that of the control group ( Figure 2 A).

[0044] Peel gas permeability: Waxing treatment reduced peel gas permeability by approximately 20 times compared to before treatment (0 d), and the gas permeability of both groups of waxed fruits gradually increased over time during storage. Notably, throughout the entire storage period, the gas permeability of the experimental group pretreated with GABA was consistently significantly higher than that of the control group, specifically 1.4 to 2.3 times that of the control group. Figure 2 B). This result directly demonstrates that GABA pretreatment can significantly improve the gas permeability of the peel of waxed fruit.

[0045] Oxygen inside the fruit: To analyze the physiological effects of changes in gas permeability, the partial pressure of oxygen inside the fruit was further measured. The results showed that waxing treatment significantly reduced the partial pressure of oxygen inside the fruit compared to the baseline value (0 d), and its dynamic change trend with storage time was consistent with the changes in gas permeability of the fruit peel. Figure 2 C). Throughout the storage period, the partial pressure of oxygen inside the fruit in the experimental group was consistently significantly higher than that in the control group, ranging from 5% to 15% higher. Figure 2 C). This indicates that GABA pretreatment effectively alleviates the insufficient oxygen supply inside the fruit that may be caused by post-harvest coating treatment by improving the overall air permeability of the fruit peel composite system after waxing.

[0046] 3. Conclusion

[0047] This embodiment demonstrates that postharvest soaking pretreatment with a 0.5 mM GABA aqueous solution effectively mitigates the decrease in fruit peel permeability caused by commercial waxing. This treatment maintains a high gas permeability in waxed fruit throughout the storage period, significantly improving oxygen supply within the fruit. Simultaneously, the pretreatment also exhibits a sustained promoting effect on fruit coloring. This technical solution successfully achieves synergistic regulation of "barrier properties" and "permeability" in coating preservation, providing an effective strategy for resolving this long-standing industry contradiction. This not only significantly supplements and enhances the performance of existing postharvest coating treatment processes but also lays a new foundation for developing next-generation composite preservation technologies that combine efficient water retention with good gas exchange capabilities.

[0048] Example 3

[0049] 1. Materials and Methods

[0050] To investigate the general effect of GABA treatment on citrus varieties with different peel permeability, this study selected three representative varieties: Wogan (C. reticulata Blanco 'Orah') and Murcott (C. reticulata 'W. Murcott'), with compact peel structure and relatively poor permeability, and Shatangju (C. reticulata 'Shatangju'), a loose-skinned citrus with good permeability, as a control. The experiment was conducted in the same orchard in Gongcheng County, Guilin City. Each variety underwent an independent experimental design: six healthy trees with similar vigor, fruit load, and color-changing progress were randomly divided into two groups (three trees in each group). At the early stage of fruit color-changing, the experimental group (GABA) was sprayed evenly across the entire canopy with a 10 mM GABA aqueous solution, while the control group (CK) was sprayed with an equal volume of water at the same time. Treatment was repeated three times at 20-day intervals. Fruits were harvested according to commercial standards after ripening, and peel gas permeability was measured immediately after harvest.

[0051] 2. Test Results

[0052] Fruit appearance and coloring: Preharvest treatment with GABA significantly promoted the color change process of Murcott and Wogan tangerines, and their color difference index (CCI) was also significantly higher than that of their respective control groups. Figure 3 AC). However, this treatment had no significant effect on the color change process or CCI value of the mandarin orange. Figure 3 (A, D). This difference may be related to the fact that the color-changing process of the mandarins was already in the middle or late stage when the treatment began.

[0053] Peel gas permeability: Measurements at harvest showed significant differences in baseline peel gas permeability among different varieties: Murcott was the worst, at only 33% of that of Satsuma mandarin; Wogan was second, at 80% of that of Satsuma mandarin. Crucially, GABA treatment showed a consistent enhancing effect on all three varieties. Compared to their respective control groups, GABA treatment significantly increased the peel gas permeability of Murcott, Wogan, and Satsuma mandarin by 43%, 50%, and 63%, respectively. Figure 3 EG).

[0054] 3. Conclusion

[0055] This embodiment demonstrates that pre-harvest spraying with a 10 mM GABA aqueous solution during the color-changing stage is a universally applicable strategy that can significantly improve the gas permeability of the peel of mature fruits from different citrus varieties (by 43-63%). Particularly noteworthy is that for varieties with naturally poor aeration, such as Murcott and Wogan, GABA treatment can achieve a substantial improvement in their already low baseline aeration (by 43% and 50%, respectively), which is crucial for fundamentally addressing post-harvest gas exchange bottlenecks and alleviating physiological stress. Furthermore, the results of this embodiment indicate that pre-harvest application of GABA exhibits the additional effect of promoting fruit color change.

[0056] As demonstrated by the above examples, this invention systematically confirmed through Examples 1 (post-harvest soaking), 2 (post-harvest soaking + waxing), and 3 (pre-harvest spraying) that γ-aminobutyric acid (GABA) treatment has a clear, stable, and universal effect on enhancing the permeability of citrus fruit peel. This effect is unaffected by the timing, method, or subsequent post-harvest treatment steps. Furthermore, this invention also found that both pre-harvest and post-harvest application of GABA positively promotes color change, further improving the fruit's appearance and commercial quality. This dual effect indicates that GABA can achieve a synergistic improvement from appearance and commercial quality to internal storage quality by optimizing peel physiology and gas exchange, fully validating its innovativeness and application potential as a core functional substance in post-harvest preservation.

[0057] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for enhancing the air permeability of fruit peel, characterized in that, The method is as follows: pre-harvest treatment and / or post-harvest treatment of the fruit using γ-aminobutyric acid (GABA); The pre-harvest treatment includes pre-harvest spraying treatment, the specific steps of which are: starting from the fruit color-changing period, spray the tree and fruit with a 1-50 mM GABA aqueous solution, with a spraying interval of 20-30 days, spraying 1-5 times, and harvesting after the last spraying. The postharvest treatment includes postharvest soaking treatment, the specific steps of which are: soaking the harvested fruit in a 0.1-10 mM GABA aqueous solution for 1-10 minutes.

2. The method according to claim 1, characterized in that, The concentration of the GABA aqueous solution used for pre-harvest spraying is 5-20 mM, and the spraying interval is 15-25 days, for a total of 2-4 times.

3. The method according to claim 1, characterized in that, The concentration of the GABA aqueous solution in the postharvest soaking treatment is 0.5-5 mM, and the soaking time is 2-5 minutes.

4. The method according to claim 1, characterized in that, The post-harvest treatment also includes: waxing treatment after post-harvest soaking treatment.

5. The method according to claim 1, characterized in that, The post-harvest treatment also includes: bagging each fruit individually with polyethylene film after post-harvest soaking treatment.

6. The method according to any one of claims 1-5, characterized in that, The fruit in question is a citrus fruit.

7. The method according to claim 6, characterized in that, The citrus fruits mentioned are Wenzhou mandarin oranges, Wogan mandarins, Murcott mandarins, or sugar mandarins.

8. A storage method, characterized in that, The method includes: treating the fruit with the method described in any one of claims 1-5 and then storing it, wherein the storage conditions are a temperature of 20±2℃ and a relative humidity of 55-70%.

9. The application of the method according to any one of claims 1-5 in promoting fruit color change.

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