A method for postharvest preservation of pepper fruits

Abstract

This invention relates to a method for post-harvest preservation of chili peppers, comprising: harvesting fresh chili peppers, washing and drying them to obtain pre-treated chili peppers; immersing the pre-treated chili peppers in a GR24 aqueous solution; after immersion, removing the chili peppers and drying them; packaging the dried chili peppers in preservation bags and storing them at low temperature or room temperature. In this invention, the chili peppers are treated with a GR24 solution after washing and drying, followed by low-temperature or room-temperature storage, which can effectively delay post-harvest aging and quality decline, significantly inhibit the occurrence of chilling injury symptoms, maintain good sensory and nutritional quality of the fruit, extend shelf life, reduce post-harvest losses, and increase economic value. Furthermore, this method is safe, environmentally friendly, and easy to operate, possessing strong commercial application potential.

Description

Technical Field

[0001] This invention relates to the field of food preservation technology, specifically to a method for post-harvest preservation of chili peppers. Background Technology

[0002] Chili peppers are one of the most widely cultivated vegetable crops in my country, boasting the most complete industrial chain and playing a vital role in fresh consumption, condiment processing, and the food industry. Chili pepper fruits have a high water content, delicate tissue, and vigorous respiration and metabolism, making them highly susceptible to a series of quality deterioration problems after harvest, including water loss and shrinkage, peel collapse, dull color, softening of tissue, nutrient degradation, and infection by pathogenic microorganisms. These changes severely shorten shelf life, reduce commercial value, and cause significant economic losses.

[0003] Low-temperature storage is the most common method to delay post-harvest senescence in chili peppers. However, chili peppers are low-temperature sensitive fruits and vegetables, and during cold chain transportation and storage, they are prone to physiological disorders such as unstable cell membrane structure, enhanced lipid peroxidation, aggravated accumulation of reactive oxygen species (ROS), and increased cell membrane permeability, thereby inducing tissue damage and quality decline. Therefore, relying solely on low-temperature environments is insufficient to fundamentally solve the problem of rapid post-harvest quality deterioration in chili peppers.

[0004] In recent years, exogenous regulator treatments have gradually become an important direction for postharvest preservation, such as 1-MCP, melatonin, polyamines, and natural polysaccharide coatings. However, these treatments still have shortcomings, such as uneven treatment, high costs, or limited applicability to different varieties. Developing safe, low-dose, and efficient physiological regulation-based preservation technologies has significant application prospects. Summary of the Invention

[0005] This invention provides a method for post-harvest preservation of chili peppers.

[0006] Some implementation schemes for solving the above-mentioned technical problems include:

[0007] A method for post-harvest preservation of chili peppers includes the following steps:

[0008] (1) Pick fresh chili peppers, wash them, and dry them to obtain pre-treated chili peppers;

[0009] (2) The pretreated chili peppers were soaked in GR24 aqueous solution;

[0010] (3) After soaking, remove the chili peppers and let them air dry;

[0011] (4) Pack the dried chili peppers from step (3) in a plastic bag and store them in a low-temperature or normal-temperature environment.

[0012] Strigolactones are a novel class of plant hormones that play a crucial role in plant development regulation and stress response, participating in physiological processes such as antioxidant regulation, lipid metabolism regulation, cell membrane stability maintenance, and senescence delay. Their artificial analog GR24 has a stable structure and well-defined activity, and has been applied in plant stress physiology research. In this invention, GR24 is used to treat chili peppers post-harvest to improve their storage and preservation effects.

[0013] As a preferred option, in step (1), the surface moisture is dried in a ventilated environment at 10±2℃ and relative humidity of 50-70% for 30-60 minutes.

[0014] Preferably, the concentration of the GR24 aqueous solution is ≤10μM.

[0015] Preferably, the concentration of the GR24 aqueous solution is 0.4 μM.

[0016] Preferably, the pretreated chili peppers are soaked in a GR24 aqueous solution for 20-40 minutes.

[0017] Preferably, the soaking time is 30 minutes.

[0018] Preferably, the low-temperature environment is 4±0.5℃ and the relative humidity is 80%-90%.

[0019] Preferably, the ambient temperature is 15~20℃ and the relative humidity is 85%-95%.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] In this invention, chili peppers are washed, dried, and then soaked in a GR24 solution before being stored at low or room temperature. This effectively delays post-harvest senescence and quality decline, significantly inhibits chilling injury symptoms (such as surface depressions, water spots, and browning), maintains good sensory quality (color and plumpness) and nutritional quality (such as vitamin C and soluble solids content), extends shelf life, reduces post-harvest losses, and increases economic value. Furthermore, this method is safe, environmentally friendly, and easy to operate, possessing strong commercial application potential. Attached Figure Description

[0022] Figure 1 The effect of different concentrations of GR24 on the chilling injury index of chili peppers during low-temperature storage.

[0023] Figure 2 The effect of different concentrations of GR24 on the incidence of chilling injury in peppers during low-temperature storage.

[0024] Figure 3The effect of different concentrations of GR24 on the weight loss rate of chili peppers during low-temperature storage.

[0025] Figure 4 The effect of different concentrations of GR24 on the change in hardness of chili peppers during low-temperature storage.

[0026] Figure 5 This study investigated the effects of different concentrations of GR24 treatment on the changes in soluble solids content of chili peppers during low-temperature storage.

[0027] Figure 6 The effect of different concentrations of GR24 on the change in relative conductivity of chili peppers during low-temperature storage.

[0028] Figure 7 The effect of different concentrations of GR24 on the change of malondialdehyde (MDA) content in chili peppers during low-temperature storage.

[0029] Figure 8 The effect of different concentrations of GR24 on the change of proline content in capsicum during low-temperature storage.

[0030] Figure 9 Images of the appearance and sections of the chili peppers (a. 0-day appearance; b. 4 μM 30-day appearance; c. 0 μM 30-day appearance; d. 0-day section; e. 4 μM 30-day section; f. 0 μM 30-day section).

[0031] Figure 10 For observation of the ultrastructure of pepper (a, d: 0-day ultrastructure; b, e: 4 μM 30-day ultrastructure; c, f: 0 μM 30-day ultrastructure; CW: cell wall; Cp: chloroplast).

[0032] Figure 11 The effect of 4 μM GR24 treatment on the ascorbic acid (AsA) content in chili peppers.

[0033] Figure 12 The effect of 4 μM GR24 treatment on the change of glutathione (GSH) content in chili peppers.

[0034] Figure 13 Effect of 4 μM GR24 treatment on changes in pepper peroxidase (POD) activity.

[0035] Figure 14 Effects of 4 μM GR24 treatment on the activity of superoxide dismutase (SOD) in chili peppers.

[0036] Figure 15 This is a GC-MS total ion chromatogram (TIC plot) of fatty acids in chili peppers.

[0037] Figure 16 The effect of 4 μM GR24 treatment on the change of fatty acid double bond index in chili peppers.

[0038] Figure 17 Effect of 4 μM GR24 treatment on the activity of phospholipase D (PLD) in pepper.

[0039] Figure 18 Effect of 4 μM GR24 treatment on changes in capsicum lipoxygenase (LOX) activity. Detailed Implementation

[0040] The specific embodiments shown below are intended to describe various configurations of the subject matter of the invention and are not intended to represent the only configuration in which the subject matter of the invention can be practiced. The specific embodiments include particular details intended to provide a thorough understanding of the subject matter of the invention. However, it will be clear and apparent to those skilled in the art that the subject matter of the invention is not limited to the specific details shown herein and can be practiced without these specific details.

[0041] Example 1

[0042] Effects of different concentrations of GR24 on the quality of postharvest chili peppers during low-temperature storage and screening of the optimal concentration

[0043] 1. Material handling

[0044] The green peppers used in the experiment were purchased from Lai Mai Cai Vegetable Store in Shangcheng District, Hangzhou City, Zhejiang Province on July 6, 2025. Fresh green peppers without mechanical damage, pests or diseases, uniform size and shape, similar maturity, intact calyxes, and an average weight of 225-250 g were selected. The peppers were randomly divided into four groups and treated with distilled water (0 μM group), 1 μmol / L GR24 aqueous solution (1 μM group), 4 μmol / L GR24 aqueous solution (4 μM group), and 8 μmol / L GR24 aqueous solution (8 μM group), respectively, for 25 min each. After drying, they were packaged in open PE plastic film and stored at 4℃ and 80% relative humidity. The first day of storage was recorded as day 0 of the experiment. Samples were taken every 5 days to calculate the chilling injury index and measure related indicators. Simultaneously, every 5 days, some peppers were transferred to room temperature (20±1℃) and placed for 24 h, and the chilling injury rate was recorded. After 25 days of storage, the two groups of test materials were transferred to room temperature and placed for three days to simulate the shelf life of the product (25+3 days) and samples were taken.

[0045] 2. Detection indicators and methods

[0046] 2.1 Chilling Injury Index: Based on the area of ​​sunken spots on the surface of pepper fruits, the degree of chilling injury is divided into four levels. The calculation method for the chilling injury index is as follows:

[0047] ;

[0048] 2.2 Chilling injury incidence: When sampling was conducted every five days, the samples were placed in a normal temperature environment for 24 hours before the chilling injury incidence was calculated using the following formula:

[0049] ;

[0050] Where N CI The number of green peppers that suffered chilling injury after being stored at room temperature for 24 hours is represented by N, which represents the total number of samples.

[0051] 2.3 Weight loss rate: Weigh the initial mass of each group of fruits and the mass at each sampling point. The calculation formula is as follows:

[0052] ;

[0053] 2.4 Hardness: Hardness was measured using a texture analyzer. A small amount of skin was removed from the equatorial region of the fruit. The texture analyzer was equipped with a cylindrical probe (2 mm in diameter), a measurement speed of 1 mm / s, and an indentation depth of 4 mm. The maximum force generated during indentation was recorded as the fruit hardness index.

[0054] 2.5 Soluble solids (TSS) content: The content was determined using a handheld refractometer. A small amount of fruit was homogenized and filtered to obtain clear juice. The refractive index was measured using a digital refractometer, and the soluble solids content was expressed as °Brix.

[0055] 2.6 Relative Conductivity: Pepper tissue was perforated into uniformly thick circular slices using a punch, placed in a beaker, and rinsed three times with deionized water. Then, deionized water was added again, and the samples were soaked at room temperature for 3 hours. The conductivity of the samples was measured using a conductivity meter, and the calculation formula is as follows:

[0056] ;

[0057] 2.7 Malondialdehyde (MDA) content: Take 1g of chili pepper fruit, add 5 mL of 10% trichloroacetic acid (TCA), mix well, then centrifuge at 12000g, 4℃ for 30min. Take 2mL of the supernatant, add 2mL of 0.67% thiobarbituric acid (TBA), mix well, and boil in a water bath for 15min. After rapid cooling, centrifuge at 10000g for 10min. Measure the absorbance of the supernatant at 450nm, 532nm, and 600nm. The formula for calculating the MDA content is:

[0058] ;

[0059] Among them, V t V represents the total volume of the sample extract; s is the volume of the sample extract taken during the determination; m is the sample mass.

[0060] 2.8 Proline Content: Take 2.0 g of fresh chili pulp, add 5 mL of 30 g / L sulfosalicylic acid solution and grind. Transfer the mixture to a test tube and boil in boiling water for 10 min, shaking the test tube continuously during this time. After boiling, cool to room temperature and centrifuge at 1000 × g for 15 min. Take 2 mL of the supernatant and add it to a mixture containing 2 mL of glacial acetic acid and 3 mL of ninhydrin. Boil the mixture again for 30 min. After cooling, add 4 mL of toluene and mix thoroughly. Measure the absorbance of the supernatant at 520 nm and 680 nm, and calculate the proline content in the sample using a proline standard curve.

[0061] 3. Results and Analysis

[0062] like Figure 1 and Figure 2 As shown, under 4℃ low-temperature storage conditions, the chilling injury index and chilling injury incidence of pepper fruits in each treatment group gradually increased with the extension of storage time. The chilling injury index of the control group increased rapidly after 10 days of storage, reaching 25.0–28.0 at 15 days, while the chilling injury index of the 1μM treatment group was only 10.0–11.0 at the same time, significantly lower than that of the control group (P<0.05). The chilling injury index of the 4μM treatment remained at 0 throughout the entire storage period, showing the strongest chilling injury inhibition effect; although chilling injury symptoms appeared in the middle and late stages of the 8μM treatment, its chilling injury index was still significantly lower than that of the control group.

[0063] from Figure 2 As can be seen, chilling injury occurred in the control group at 5+1 days of storage, with an incidence rate of 20%, which increased to 40% and 80% at 10+1 days and 15+1 days, respectively. Different concentrations of treatment could reduce the incidence of chilling injury to some extent, but the mitigation effects varied. The 4 μM treatment group maintained a chilling injury incidence rate of 0% throughout the entire 15+1 day storage period, and was significantly lower than the control group from 5+1 days onwards (P < 0.05), demonstrating a significantly better inhibitory effect than other treatment groups.

[0064] Depend on Figure 3 It was observed that the weight loss rate of the fruit in all treatment groups gradually increased with prolonged storage time, but significant differences existed among the different treatments. The weight loss rates of the control group were 4.67% and 10.40% at 5 and 15 days of storage, respectively. After treatment with different concentrations, the water loss of the fruit was inhibited to varying degrees. The 4 μM treatment group had the lowest weight loss rate, at 1.47% and 4.44% at 5 and 15 days, respectively, significantly lower than the control group (P < 0.05), and its overall inhibitory effect was superior to other treatment groups. This indicates that appropriate concentrations of GR24 treatment help slow down fruit water loss and maintain good marketability.

[0065] like Figure 4As shown, the firmness of the fruit in all treatment groups decreased with prolonged storage time, but the decrease was significantly smaller in the treatment groups than in the control group. The firmness of the control group decreased to 10.42 N and 7.99 N after 10 and 15 days of storage, respectively. After treatment with different concentrations, the rate of decrease in fruit firmness slowed down. The 4 μM treatment group maintained the highest firmness level within the same storage period, reaching 10.95 N and 8.47 N at 10 and 15 days, respectively, significantly higher than the control group (P < 0.05), indicating that its effect in delaying fruit softening was superior to other treatment groups.

[0066] like Figure 5 As shown, the TSS content of the control group fruit continued to decrease with prolonged storage time, from an initial 4.25°Brix to 3.00°Brix at 15 days. After treatment with different concentrations, the downward trend in fruit TSS content was somewhat alleviated. Specifically, the 4μM treatment group maintained TSS content at 4.25°Brix and 4.05°Brix at 10 and 15 days of storage, respectively, significantly higher than the control group from day 10 onwards (P < 0.05), indicating that 4μM treatment helps to better delay the consumption of fruit nutrients and maintain good edible quality.

[0067] Depend on Figure 6 It was found that the relative conductivity of the control group fruits remained at a high level during storage, averaging 0.21, indicating that the cell membrane structure was significantly damaged under low temperature conditions. Different concentrations of treatment could reduce the relative conductivity to some extent. The 4 μM treatment group reduced it to 0.15 after 5 days of storage and remained significantly lower than the control group throughout the entire storage period (P < 0.05), indicating that this treatment could effectively alleviate low temperature-induced cell membrane damage, with the 4 μM treatment being the optimal choice.

[0068] like Figure 7 As shown, the MDA content of the control group fruits increased significantly with storage time, reaching its highest level in the later stage of storage; while the MDA content of the treatment group was consistently significantly lower than that of the control group (P < 0.05). Among them, the MDA content of the 1 μM and 4 μM treatments was reduced by about 30%–45% compared with the control group in the later stage of storage, indicating that the treatment effectively inhibited membrane lipid peroxidation and reduced oxidative damage.

[0069] like Figure 8As shown, the proline content in pepper fruits showed a continuous upward trend during storage. Compared with the control group, exogenous GR24 treatment significantly promoted proline accumulation, exhibiting a certain concentration dependence, with 4 μM and 8 μM treatments showing the most significant effects. In the middle and late stages of storage, the proline content in the GR24-treated groups was significantly higher than that in the control (P < 0.05). As an important osmotic regulator and antioxidant molecule, the large accumulation of proline helps maintain cellular osmotic balance, stabilize protein and membrane structures, and alleviate damage caused by reactive oxygen species, indicating that GR24 treatment enhances the physiological adaptability of pepper fruits to low-temperature stress.

[0070] In summary, the 4 μM GR24 treatment showed the best results in inhibiting chilling injury, reducing weight loss, maintaining firmness and nutritional quality, and protecting cell membrane structure.

[0071] 4. Conclusion

[0072] Under low-temperature storage conditions, exogenous GR24 treatment significantly improved the storage quality of postharvest pepper fruits, with 4 μM being the optimal treatment concentration. This concentration of GR24 effectively inhibited chilling injury, reduced weight loss, delayed fruit softening, maintained soluble solids content, and mitigated cell membrane damage, providing optimal treatment parameters for further in-depth research on the mechanism of action and practical application of GR24.

[0073] Example 2

[0074] The profound effects of 4 μM GR24 treatment on the microstructure, antioxidant capacity and membrane lipid metabolism of pepper fruits

[0075] 1. Material handling

[0076] The green peppers used in the experiment were purchased on July 6, 2025, from Lai Maicai Vegetable Store in Shangcheng District, Hangzhou City, Zhejiang Province. Fresh, undamaged, disease-free, uniform in size and shape, similar in maturity, with intact calyxes, and an average weight of 225-250 g were selected. The fruits were randomly divided into two groups, treated with distilled water (0 μM group) and 4 μmol / L GR24 aqueous solution (4 μM group), respectively, for 25 min per pepper. After drying, they were packaged in open PE plastic film and stored at 4℃ and 80% relative humidity. The first day of storage was recorded as day 0 of the experiment. Samples were taken every 5 days, and the flesh of the equatorial portion of the green pepper fruit was quickly cut off with a scalpel and immediately frozen in liquid nitrogen, stored at -80℃ for subsequent experiments. After 25 days of storage, both groups of materials were transferred to room temperature for three days to simulate the shelf life of a commercial product (25+3 days), and samples were taken again. The slice structure and ultrastructure of bell pepper fruits were observed using samples stored for 0 days and 25 days, respectively.

[0077] 2. Detection Indicators and Methods

[0078] 2.1 Microstructure observation:

[0079] 2.1.1 Appearance Changes and Stereomicroscopic Observation: The overall appearance was recorded using a professional camera. For patch observation, the bell pepper fruit was cut longitudinally, and a 5 mm × 10 mm piece of pulp was placed on the stereomicroscope stage to observe the anatomical structure and capture images.

[0080] 2.1.2 Transmission Electron Microscopy (TEM) Observation: Small pieces of green bell pepper pulp tissue measuring 1 mm × 1 mm × 3 mm were immediately fixed in 2.5% glutaraldehyde. After the green bell pepper tissue pieces sank, the fixative was removed. After fixing the samples with 1% osmium tetroxide for 2 h and rinsing them thoroughly with phosphate buffer (pH 7.2), the samples were successively placed in 50% ethanol, 70% ethanol, 80% acetone, and 90% acetone, and finally immersed three times in 100% acetone for dehydration. The samples were then embedded, sectioned using ultrathin sections, and collected on a copper grid. After staining with uranyl acetate and citric acid, the ultrastructure of the samples was observed and photographed using TEM.

[0081] 2.2 Antioxidant capacity test

[0082] 2.2.1 Ascorbic Acid (AsA) Content: Weigh 2.5 g of green bell pepper pulp sample, add 5 mL of 5% trichloroacetic acid solution under low temperature conditions for homogenization to prevent ascorbic acid oxidation. Centrifuge the homogenate at 12000 g and 4℃ for 15 min, and collect the supernatant. The supernatant is then reacted sequentially with 0.2 M pH 7.4 phosphate buffer, 0.5% α-bipyridine dissolved in 70% ethanol, and 0.03% FeCl3 solution at 25℃ in the dark for 30 min to form a stable colorimetric system under acidic conditions. The absorbance is measured at 525 nm. A standard curve is plotted using ascorbic acid standard solution, and the AsA content in the sample is calculated, expressed in μg·mg. -1 express.

[0083] 2.2.2 Glutathione (GSH) content: Weigh 2.5g of chili pulp sample, add 10 mL of 5% phosphate buffer containing 5 mM EDTA, homogenize, and then centrifuge at 13000 ×g for 18 min at 4℃ to obtain the supernatant. Mix 0.4 mL of the supernatant, 1.0 mL of pH 7.6 100 mM sodium phosphate buffer, and 0.6 mL of 4 mM DTNB, and react at 25℃ for 10 min. Immediately after the reaction, measure the absorbance of the reaction solution at 412 nm. Plot a standard curve using glutathione standard solution, and calculate the GSH content in the sample, expressed as μmol·g⁻¹.

[0084] 2.2.3 Peroxidase (POD) activity: 2.5 g of pepper pulp sample was weighed and homogenized in 10 mL of 0.2 M phosphate buffer (pH 7.0, containing 1% PVPP and 5 mM EDTA-Na2) in an ice bath. The homogenate was then centrifuged at 13000 × g for 18 min at 4 °C to obtain the supernatant. 0.5 mL of the supernatant, 3.0 mL of 25 mM guaiacol, and 220 μL of 0.5 M H2O2 solution were mixed thoroughly. Immediately after the reaction, the absorbance of the reaction solution at 470 nm was measured in U·g. -1 FW indicates POD activity.

[0085] 2.2.4 Superoxide dismutase (SOD) activity: The activity was determined according to the instructions of the superoxide dismutase kit (Beijing Solarbio Science & Technology Co., Ltd.).

[0086] 2.3 Membrane lipid metabolism detection

[0087] 2.3.1 Membrane lipid fatty acid composition analysis (GC-MS):

[0088] 2.3.1.1 Lipid Extraction: The fatty acid content in green peppers was quantified using the internal standard method. 10.0 g of green pepper tissue was ground into powder, placed in a 100℃ drying oven for 10 min to inactivate enzymes, and then potassium heptadecanate (C17:0 ME; internal standard) and 10 mL of a 2:1 chloroform:methanol mixture were added. The mixture was centrifuged at 10000×g for 20 min at room temperature. The lower lipid phase was aspirated and 5 mL of 0.76% sodium chloride solution was added. After shaking for 15 min at room temperature, the lower layer was evaporated under reduced pressure to obtain the total lipids.

[0089] 2.3.1.2 Fatty acid methyl esterification: Add 6 mL of saturated methanol to the total lipids, mix thoroughly, collect the lower layer, and add 1 mL of chromatographic grade methanol-dissolved potassium hydroxide solution (0.4 mol / L), 4 mL of a benzene-petroleum ether mixture (v / v), and 8 mL of distilled water sequentially. Shake and allow to stand until separation occurs. Evaporate the supernatant under reduced pressure to dryness, dissolve the dry matter in chromatographic grade n-hexane, and then perform instrumental analysis.

[0090] 2.3.1.3 GC-MS Analysis: The initial column oven temperature was set to 800℃ and increased at a rate of 20℃ / min. When the temperature reached 170℃, it was increased to 200℃ at a rate of 20℃ / min and maintained for 15 min. To calculate the response coefficients of each fatty acid component to the internal standard, standard samples containing methyl esters of seven fatty acids (C14:0, C15:0, C16:0, C17:0 (internal standard), C18:0, C18:1, C18:2) were first separated and analyzed using the method described above. The quantitative methods for each fatty acid component were based on the national standard GB5009.168-2016, and the types and relative contents of each fatty acid were determined by comparison with the standard. The double bond index (DBI = ∑(molar percentage of each fatty acid × number of double bonds)) was calculated.

[0091] 2.3.2 Phospholipase D (PLD) activity: Take 5 g of pepper fruit tissue, add 5 mL of pre-cooled phosphate buffer (0.1 M Na2HPO4·12H2O and 0.1 M NaH2PO4·2H2O), and grind on ice until homogenized. Then centrifuge at 7000 g, 4℃ for 20 min, collect the supernatant for subsequent enzyme activity analysis, and use the phospholipase D kit (Suzhou Grease Biotechnology Co., Ltd.) according to the instructions.

[0092] 2.3.3 Lipoxygenase (LOX) activity: The supernatant after pretreatment was measured using PLD according to the instructions of the lipoxygenase kit (Shanghai Yuanye Biotechnology Co., Ltd.).

[0093] 3. Results and Analysis

[0094] like Figure 9 As shown, compared with the early stage of storage, the pepper fruits in the control group showed obvious dents, water-soaked spots and dehydration and wrinkling after 25 days of low-temperature storage, and the flesh was loose. In contrast, the fruits in the 4μM GR24 treatment group remained plump, the surface chilling injury symptoms were significantly reduced, and the integrity of the cut surface tissue structure was significantly better than that of the control group.

[0095] Transmission electron microscopy observation results ( Figure 10 The results showed that after 25 days of storage, the cell structure of the control group fruits was severely damaged, with irregular cell wall morphology, severe plasmolysis, blurred organelle structure, and obvious disintegration of the chloroplast membrane system. In contrast, the cell wall structure of the 4 μM GR24 treatment group was clear, the cell membrane continuity was better, and the chloroplasts and other organelles were relatively intact, indicating that GR24 treatment helps maintain the stability of cell ultrastructure.

[0096] like Figure 11 and Figure 12As shown, 4 μM GR24 treatment significantly increased and maintained the AsA and GSH contents in pepper fruits. The AsA content in the control group increased from the initial 16.66 μg·mg... -1 The levels decreased rapidly, reaching only 7.80 μg·mg⁻¹ by day 15. In contrast, the 4 μM GR24 treatment group maintained levels of 14.78 μg·mg⁻¹ at days 10 and 15, respectively. -1 and 9.70 μg·mg -1 The difference between the control group and the control group was significant from day 5 onwards (P < 0.001). The GSH content in the control group decreased from 37.78 μmol·g⁻¹. -1 Decreased to 22.99 μmol·g -1 The GSH content in the 4 μM GR24 treatment group remained at 33.92 μmol·g⁻¹ after 10 days of storage. -1 The levels of these substances were significantly higher than those in the control group (P < 0.001) and remained high even after 15 days. Compared with the control group, the GR24-treated group maintained higher levels of both non-enzymatic antioxidants throughout the storage period, indicating that exogenous GR24 treatment helps enhance the antioxidant reserves of pepper fruits.

[0097] Depend on Figure 13 It was observed that the POD activity in the control group showed a slow, fluctuating upward trend during storage. The POD activity in the 4 μM GR24 treatment group increased rapidly in the early stage of storage, reaching approximately 13.38 U·g⁻¹ FW at 10 days. Although it subsequently declined slightly, it remained significantly higher than the control group (P < 0.001), and further increased to approximately 16.01 U·g⁻¹ at the end of storage (25 ± 3 days). -1 This indicates that 4 μM GR24 treatment significantly enhanced POD activity in pepper fruits and maintained a high level of enzyme activity throughout the entire storage period, especially in the middle and late stages. This suggests that the treatment can effectively enhance the antioxidant enzyme activity of pepper fruits, thereby improving their antioxidant capacity.

[0098] Depend on Figure 14 It can be seen that the SOD activity in the control group remained at 3.95 U·g during storage. -1 The levels were lower in the 4 μM GR24 treatment group, while they increased to 4.59 U·g after 5 days. -1 It reached 5.22 U·g after 10 days. -1 The activity of SOD in pepper fruits was significantly higher than that in the control group from day 5 (P < 0.05). The 4 μM GR24 treatment significantly increased the SOD activity in pepper fruits and maintained a high level in the middle and late stages of storage, indicating that it can effectively activate the antioxidant enzyme system.

[0099] Results of fatty acid composition analysis ( Figure 15The results showed that the fatty acid types in the cell membranes of pepper fruits mainly included saturated fatty acids and unsaturated fatty acids. Further calculations of the DBI (see...) Figure 16 The study found that the DBI of the control group decreased significantly during storage, while the DBI of the 4 μM GR24 treatment group decreased less, indicating that GR24 treatment helps maintain the degree of membrane lipid unsaturation and slows down the deterioration of membrane lipid structure.

[0100] like Figure 17 As shown, PLD activity generally increased during storage, with the control group showing a significant increase in the middle and late stages (after 20 days), indicating accelerated membrane phospholipid degradation. Treatment with 4 μM GR24 significantly delayed the increase in PLD activity, showing significantly lower levels than the control group at 10, 20, 25, and 25+3 days (P < 0.05). PLD is a key initiating enzyme for membrane lipid degradation, hydrolyzing membrane phospholipids to phosphatidic acid, which in turn leads to membrane structural disorder. The inhibition of PLD activity by GR24 indicates that it can slow down the process of membrane phospholipid hydrolysis, thereby maintaining the stability of cell membrane structure.

[0101] like Figure 18 As shown, during storage, the LOX activity in the control group fruits increased significantly over time, especially after 20 days, showing a rapid upward trend and reaching a high level at 25 days and during the recovery phase, indicating that low-temperature storage exacerbated the membrane lipid peroxidation process. In contrast, treatment with 4 μM GR24 significantly inhibited the increase in LOX activity, showing significantly lower levels than the control at 5 days, 20 days, 25 days, and 25+3 days (P < 0.01). LOX is a key enzyme catalyzing the oxidation of polyunsaturated fatty acids, and its enhanced activity is usually closely related to membrane lipid peroxidation and membrane structure damage. Therefore, the inhibition of LOX activity by GR24 indicates that it can slow down membrane lipid oxidation and reduce the damage of oxidative stress to the cell membrane system.

[0102] Based on the combined results of microstructure, antioxidant capacity and membrane lipid metabolism, it can be concluded that 4μM GR24 treatment can synergistically alleviate the damage of low temperature stress to pepper fruits from both structural and metabolic perspectives.

[0103] 4. Conclusion

[0104] Treatment with 4μM GR24 effectively reduced damage to cells and membrane systems during low-temperature storage by maintaining the integrity of pepper fruit cell structure, enhancing antioxidant defense capabilities, and regulating membrane lipid metabolism stability, thereby delaying fruit senescence and quality deterioration. This provides a clear physiological and structural basis for the application of GR24 in postharvest preservation of peppers.

[0105] In summary, this invention provides a postharvest preservation method for chili peppers based on the novel plant hormone GR24. This method has a clear principle, significant effect, feasible operation, and is safe and environmentally friendly, with good prospects for industrial application. It can provide strong technical support for improving the quality and efficiency of the chili pepper industry and reducing postharvest losses.

[0106] The technical solution of the present invention and its corresponding details have been described above. It is understood that the above description is only some implementation schemes of the technical solution of the present invention, and some details may be omitted in the specific implementation.

[0107] Furthermore, in some embodiments of the above invention, multiple embodiments may be combined; however, due to space limitations, all such combinations will not be listed here. Those skilled in the art can freely combine and implement the above embodiments according to their needs to obtain a better application experience.

[0108] When implementing the subject matter of this invention, those skilled in the art can obtain other detailed configurations or drawings based on the subject matter and drawings. Obviously, these details are still within the scope of the subject matter of this invention without departing from it.

Claims

1. A method for post-harvest preservation of chili pepper fruits, characterized in that, Includes the following steps: (1) Pick fresh chili peppers, wash them, and dry them to obtain pre-treated chili peppers; (2) The pretreated chili peppers were soaked in GR24 aqueous solution; (3) After soaking, remove the chili peppers and let them air dry; (4) Pack the dried chili peppers from step (3) in a plastic bag and store them in a low-temperature or normal-temperature environment.

2. The method for post-harvest preservation of chili peppers according to claim 1, characterized in that, When drying in step (1), the surface moisture is dried in a ventilated environment at 10±2℃ and relative humidity of 50-70% for 30-60 minutes.

3. The method for post-harvest preservation of chili peppers according to claim 2, characterized in that, The concentration of the GR24 aqueous solution is ≤10μM.

4. The method for post-harvest preservation of chili peppers according to claim 3, characterized in that, The concentration of the GR24 aqueous solution was 0.4 μM.

5. The method for post-harvest preservation of chili peppers according to any one of claims 3-4, characterized in that, The pretreated chili peppers were soaked in GR24 aqueous solution for 20-40 minutes.

6. The method for post-harvest preservation of chili peppers according to claim 5, characterized in that, The soaking time is 30 minutes.

7. The method for post-harvest preservation of chili peppers according to claim 1, characterized in that, The low-temperature environment is 4±0.5℃ and the relative humidity is 80%-90%.

8. The method for post-harvest preservation of chili peppers according to claim 1, characterized in that, The ambient temperature is 15~20℃ and the relative humidity is 85%-95%.

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