Application of soybean peptides in fruit preservation

Abstract

The application discloses application of soybean peptides in fruit preservation. The application discloses application of soybean peptides in fruit preservation, expands the application range of the soybean peptides, and can significantly maintain the hardness, ethylene content, titratable acid content and soluble sugar content of apple fruits, maintain the superoxide dismutase activity of the fruits, reduce browning of the fruits, and enable long-term preservation of the apples and is safe and reliable.

Description

Technical Field

[0001] This invention relates to the field of fruit preservation technology, specifically to the application of soybean peptides in fruit preservation. Background Technology

[0002] Fruit quality primarily refers to the superiority of the appearance, flavor, and nutritional value of harvested fruits and vegetables. The textural attributes of fruits mainly include firmness, toughness, juiciness, crispness, chewiness, and stickiness, with firmness being the most studied. During post-harvest storage, due to respiration and metabolism, the content of pectin in fruits changes, leading to an increase in soluble pectin and a decrease in insoluble pectin. Cell wall integrity is also disrupted, resulting in softening and a decrease in fruit firmness, thus reducing fruit quality. Fruit softening not only affects the texture and edibility of post-harvest fruits but also significantly limits their shelf life and post-harvest transportation. Fruit flavor includes taste and aroma, mainly produced by chemical substances in the fruit and vegetable tissues that stimulate human taste and smell. The four most important taste sensations in fresh fruits and vegetables are sweet, sour, bitter, and astringent, produced by sugars, organic acids, bitter substances, and tannins, respectively. Among these, sour and sweet components are important factors in the flavor of certain fruits and vegetables.

[0003] Postharvest fruit loss is a global problem that has attracted significant attention worldwide. After harvesting, fresh fruit suffers from softening, spoilage, and dehydration due to its own activity and unsuitable environmental or physicochemical factors. Therefore, to effectively reduce postharvest losses, physical measures such as low temperatures are used in conjunction with chemical pesticides (preservatives and fungicides) to control postharvest diseases and delay fruit senescence. However, long-term use of chemical agents can lead to pesticide resistance in pathogens, reducing disease control effectiveness. More seriously, the large-scale use of chemical agents increases pesticide residues on fruit, threatening human health. In today's emphasis on green practices, plant-derived preservatives are gaining increasing attention due to their lack of environmental pollution, pesticide residues, and resistance associated with chemical preservatives, as well as their advantages such as easily controllable storage conditions and targeted treatment. Therefore, developing safe and environmentally friendly plant-derived preservatives has become a research direction and hot topic both domestically and internationally.

[0004] Soybean peptides are peptides obtained from soybean protein through enzymatic hydrolysis. They possess low antigenicity, inhibit cholesterol, promote lipid metabolism, and aid in fermentation. When used in food, they can quickly replenish protein sources, alleviate fatigue, and act as growth factors for bifidobacteria. Furthermore, soybean peptides have antioxidant properties that inhibit free radicals, accelerate the repair of damaged cells, maintain bodily vitality, and reduce pigmentation, making them excellent ingredients for health foods. However, research on the application of soybean peptides in fruit preservation is scarce. Summary of the Invention

[0005] In view of the above-mentioned prior art, the purpose of this invention is to provide the application of soybean peptides in fruit preservation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides the application of soybean peptides in fruit preservation.

[0008] Preferably, the soybean peptides achieve fruit preservation through at least one of the following methods (1)-(5):

[0009] (1) Maintain fruit firmness during storage;

[0010] (2) Reduce the ethylene content during fruit storage;

[0011] (3) Maintain the titratable acid content of the fruit during storage;

[0012] (4) Maintain the soluble sugar content of the fruit during storage;

[0013] (5) Maintain superoxide dismutase activity during fruit storage.

[0014] Preferably, the fruit is an apple.

[0015] In a second aspect, the present invention provides a method for preserving apples by uniformly spraying an aqueous solution of soybean peptides onto the surface of the apples, repeating the process 2-4 times, and then storing the apples at 0-4°C.

[0016] The concentration of the soybean peptide aqueous solution is 0.05-0.15 g / L, the total spraying amount for each apple is 100-200 mL, and the spraying time is 10-15 min.

[0017] The beneficial effects of this invention are:

[0018] The beneficial effects of this invention are that treating apples with soybean peptides can significantly maintain fruit firmness, reduce fruit ethylene release, maintain the content of titratable acid and soluble sugar in the fruit, maintain the activity of superoxide dismutase in the fruit, reduce fruit browning, and enable apples to be preserved for a long time safely and reliably. Attached Figure Description

[0019] Figure 1 Phenotypic image and cross-section of apple fruit after spraying with soybean peptide aqueous solution;

[0020] Figure 2 The firmness of apples in the control and experimental groups;

[0021] Figure 3Ethylene in apple fruits from the control and experimental groups;

[0022] Figure 4 Titratable acidity of apples in the control and experimental groups;

[0023] Figure 5 Soluble sugars in apples from the control and experimental groups;

[0024] Figure 6 Superoxide dismutase activity in apple fruits of the control and experimental groups. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0026] As described in the background section, after harvesting, fresh fruits suffer from softening, spoilage, and dehydration due to their own activity and unsuitable environmental or physicochemical factors. Excessive use of chemical preservatives increases pesticide residues on fruits, threatening human health. Plant-derived preservatives, lacking the environmental pollution, pesticide residues, and resistance issues associated with chemical preservatives, have become a research focus and hot topic both domestically and internationally. Soybean peptides, obtained from soybean protein through enzymatic hydrolysis, have been reported to possess antioxidant properties, but their application in fruit preservation has yet to be documented.

[0027] Based on this, the inventors explored the role of soybean peptides in fruit preservation. By spraying soybean peptides onto apples, they examined their effects on maintaining fruit firmness and flavor (soluble sugars, titratable acids), and also investigated their effects on ethylene, a hormone that promotes fruit senescence, and superoxide dismutase (SOD), a protective enzyme that scavenges reactive oxygen species in apples. They found that soybean peptides can maintain apple firmness, reduce ethylene content, and maintain titratable acids, soluble sugars, and SOD activity. Therefore, soybean peptides have broad application prospects in maintaining apple freshness and extending apple storage and shelf life.

[0028] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0029] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0030] The soybean peptides used in this invention were purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with product number S916495-25g.

[0031] Example 1:

[0032] Prepare a 0.1 g / L soybean peptide aqueous solution and spray it on apple fruits. The ambient temperature during spraying is 15℃. The spraying method is to spray from top to bottom, and spray evenly on the surface of the fruit. After spraying back and forth three times, place the fruit in a dark place to air dry naturally at room temperature. The total spraying amount for each apple is 150 mL, and the spraying time is 15 min. Store at 0℃.

[0033] Example 2:

[0034] Prepare a 0.05 g / L soybean peptide aqueous solution and spray it on apple fruits. The ambient temperature during spraying is 15℃. The spraying method is to spray from top to bottom, and spray evenly on the surface of the fruit. After spraying back and forth three times, place the fruit in a dark place to air dry naturally at room temperature. The total spraying amount for each apple is 150 mL. Store at 0℃.

[0035] Example 3:

[0036] Prepare a 0.15 g / L soybean peptide aqueous solution and spray it on apple fruits. The ambient temperature during spraying is 15℃. The spraying method is to spray from top to bottom, and spray evenly on the surface of the fruit. After spraying back and forth three times, place the fruit in a dark place to air dry naturally at room temperature. The total spraying amount for each apple is 150 mL, and the spraying time is 15 min. Store at 0℃.

[0037] Experimental example:

[0038] 1. Test method:

[0039] 1.1 Experimental Grouping:

[0040] Two hundred apples (each weighing 216.13g ± 32.57g) from the same batch, of the same variety and specifications, and with no difference in freshness and other indicators were selected and randomly divided into two groups of 100 apples each.

[0041] The experimental group treated the apples according to the method described in Example 1;

[0042] The control group was treated by spraying distilled water onto apples at a temperature of 15℃. The spraying method was to spray the fruit from top to bottom, evenly on the surface of the fruit, and spray back and forth three times. After spraying, the fruit was placed in a dark place to air dry naturally at room temperature. The spraying amount was 150mL, the spraying time was 15min, and the fruit was stored at 0℃.

[0043] Samples were taken at 0, 15, 30, 45, 60, 90 and 120 days after treatment to observe apple phenotype and measure apple firmness, ethylene content, titratable acid content, soluble sugar content and superoxide dismutase activity.

[0044] 1.2 Test Method:

[0045] 1.2.1 Hardness testing method:

[0046] Apple firmness was determined using a Stable Micro Systems TA.XT plus texture analyzer. A P / 2 cylindrical probe (2 mm diameter) was used for measurement. The initial speed was 2 mm / s, the measurement speed was 1 mm / s, and the subsequent speed was 5 mm / s. The penetration depth was 10 mm, and the minimum sensing force was 10 g. For each sampling day, six apples of each concentration were randomly selected. Four evenly spaced points were randomly chosen around the central equator of the apple for puncture testing perpendicular to the fruit surface. The measured fruit firmness values ​​were analyzed using Texture Exponent 32 software. The results for each experimental group were taken as the average of the six apples.

[0047] 1.2.2 Method for determining ethylene release rate:

[0048] Two apple fruit samples were placed in a 1L glass container, sealed, and placed at 25℃ for 6 hours. One sample was then taken. mL Gas injection was performed using a gas chromatograph (GC-2014 model, Shimadzu, Kyoto, Japan) equipped with an activated alumina column and a flame ionization detector to determine ethylene concentration. The settings were based on Liu Jingxuan's (2017) method, with slight modifications (see Table 1). Measurements were repeated three times, and the average value was taken.

[0049] Table 1. Ethylene determination conditions

[0050]

[0051] Calculation formula: Ethylene release rate = C × (V0 - V1) ÷ W ÷ T

[0052] C: Ethylene concentration (µL·mL⁻¹); V0: Beaker volume (mL); V1: Sample volume (mL); T: Sealing time (h); W: Apple mass (g).

[0053] 1.2.3 Method for determining titratable acids:

[0054] (1) Weigh 10.0g of the well-mixed apple sample, grind it in a mortar, transfer it to a 100ml volumetric flask, rinse the mortar with distilled water and transfer it into the volumetric flask, then make up to the mark and shake well. Filter after standing for 30min.

[0055] (2) Pipette 20.0 ml of the filtrate into an Erlenmeyer flask, add 2 drops of 1% phenolphthalein indicator, and titrate with a standardized sodium hydroxide solution. The endpoint is reached when the solution initially turns pink and does not fade within 0.5 min (pH = 8.1-8.8). Record the volume of sodium hydroxide titrant used, and repeat three times. Then titrate with distilled water instead of the filtrate as a blank control.

[0056] (3) Take 1 mL of extract 2 and add it to the precipitate. Heat in a water bath at 90℃ for 1 h, cool, centrifuge at 8000×g and 25℃ for 15 min, and keep the supernatant for testing.

[0057] (4) Calculate the titratable acid content in fruit and vegetable tissues based on the amount of sodium hydroxide titrant consumed, expressed as a mass fraction (%). Calculation formula: Titratable acid content = V × c × (V1-V0) × f / Vs / m × 100%.

[0058] V: Total volume of sample extract; c: Concentration of sodium hydroxide titrant; V1: Volume of sodium hydroxide solution consumed in titration of filtrate; V0: Volume of sodium hydroxide solution consumed in titration of distilled water; f: Conversion factor (0.067 g / mmol for apples); Vs: Volume of filtrate taken during titration; m: Fresh weight of sample (g).

[0059] The titratable acid content was calculated once at each sampling time, and the results of each experimental group were taken as the average of 6 apples.

[0060] 1.2.4 Method for determining soluble sugars:

[0061] (1) Weigh 0.5g of the well-mixed apple sample, add 1ml of phosphate buffer (0.05mol / L, pH=7.8), grind in an ice bath, add another 1ml of phosphate buffer, pour into a centrifuge tube, wash the mortar with 2ml of phosphate buffer, pour into a centrifuge tube, equilibrate, centrifuge at low temperature for 20min, and then take the supernatant and store it in the refrigerator.

[0062] (2) Take 0.5 ml of the supernatant and add 1.5 ml of distilled water, then add 0.5 ml of anthrone ethyl acetate reagent and 5 ml of concentrated sulfuric acid. Shake well and immediately put the test tube into a boiling water bath and keep it warm for 1 min. After taking it out, let it cool naturally to room temperature. Use the blank as a reference and measure the absorbance at 630 nm. Calculate the content of soluble sugar in the sample according to the standard curve.

[0063] (3) Plotting the standard curve:

[0064] Table 2. Plotting the Standard Curve

[0065]

[0066] (4) Calculation formula: Soluble sugar content = (C × V / a × n) / W × 10 3 .

[0067] C: Sugar content in µg; a: Sample liquid volume in mL; V: Extracted liquid volume in mL; n: Dilution factor; W: Fruit weight (g). Soluble sugar content was calculated at each sampling time, and the results for each experimental group were the average of 6 apples.

[0068] 1.2.5 Superoxide dismutase assay method:

[0069] (1) Weigh 0.5g of the well-mixed apple sample, add 1ml of phosphate buffer (0.05mol / L, pH=7.8), grind in an ice bath, add another 1ml of phosphate buffer, pour into a centrifuge tube, wash the mortar with 2ml of phosphate buffer, pour into a centrifuge tube, equilibrate, centrifuge at low temperature for 20min, and then take the supernatant and store it in the refrigerator.

[0070] (2) Take test tubes of the same type, add 50µL of supernatant to each test tube (add 50µL of phosphate buffer to each of the 4 control test tubes), add 3ml of reaction solution to each, place 2 control test tubes in the dark, and react the remaining tubes under 4000lx sunlight for 20-30min (the light exposure of each tube should be consistent, with higher temperature and shorter time, and lower temperature and longer time). After the reaction is completed, use the control test tubes that are not exposed to light as blanks, and measure the absorbance value at 560nm.

[0071] (3) 150ml reaction solution composition: water 12.7ml, phosphate buffer 76.5ml, Met 15.25ml, NBT 15.25ml, EDTA-Na 2 15.25ml, riboflavin 15.25ml.

[0072] (4) Calculation formula: The amount of enzyme required to inhibit 50% photochemical reduction of NBT is the enzyme activity unit (U);

[0073] SOD activity = (A ck -A s )×V / (A ck ×0.5 ×FW×V1).

[0074] A ck : Absorbance of the control tube; A s : Absorbance of sample tube; V: Total sample volume (mL); V1: Amount of sample used during measurement (ml); FW: Apple mass (g).

[0075] Superoxide dismutase activity was calculated at each sampling time, and the results for each experimental group were the average of 6 apples.

[0076] 1.3 Experimental Results:

[0077] The test results are shown in Figures 1-6 .

[0078] Figure 1 The phenotypic diagram of apples in their optimal fruit condition, from Figure 1 As can be seen, at 120 days, the browning of the pulp inside the fruit in the control group was more pronounced than that in the treatment group.

[0079] Figure 2 To determine the firmness of apples in each experimental group, from Figure 2 It can be seen that on day 0, the hardness of each component was at the same level; on day 60, the hardness of apples in the control group dropped to below 2, while the hardness of apples sprayed with soybean peptide was greater than or equal to 2; on day 120, the hardness of apples in the sprayed group was still the lowest among all experimental groups after the control group, indicating that spraying apples with soybean peptide can effectively maintain the hardness of apple fruits.

[0080] Figure 3 The ethylene content of apples in each experimental group was calculated from... Figure 3 It can be seen that on day 60, the ethylene release of apples in the control group increased significantly, while the ethylene release of apples sprayed with soybean peptides was significantly lower than that in the control group; on day 120, the ethylene release of apples sprayed with soybean peptides was still lower than that in the control group, indicating that spraying apples with soybean peptides can effectively reduce the ethylene release of apple fruits.

[0081] Figure 4 The titratable acid content of apple fruits in each experimental group was determined from... Figure 4 It can be seen that during the experiment, the titratable acid content of the experimental group was always higher than that of the control group. On day 60, the titratable acid content of apples in the experimental group was 60% higher than that in the control group. On day 120, the titratable acid content of apples sprayed with soybean peptides was still higher than that in the control group, indicating that spraying apples with soybean peptides can effectively maintain the titratable acid content of apple fruits.

[0082] Figure 5 The soluble sugar content of apples in each experimental group was determined from... Figure 5 It can be seen that after 30 days, the soluble sugar content of the experimental group was always higher than that of the control group. On the 45th and 60th days, the soluble sugar content of the experimental group was 38% and 29% higher than that of the control group, respectively. On the 120th day, the soluble sugar content of the apples after spraying with soybean peptides was still higher than that of the control group, indicating that spraying apples with soybean peptides can effectively maintain the soluble sugar content of apple fruits.

[0083] Figure 6To measure the superoxide dismutase (SOD) activity in apples from each experimental group, the SOD activity in the experimental groups was consistently significantly higher than that in the control group throughout the experiment. On day 60, the SOD activity in the experimental groups was 117% higher than that in the control group. On day 120, the SOD activity in the apples treated with soybean peptides was still higher than that in the control group, indicating that treating apples with soybean peptides effectively maintains the SOD activity in the fruit. Based on the above experiments, it can be clearly concluded that treating apples with a 0.1 g / L soybean peptide aqueous solution has a good preservation effect.

[0084] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. The application of soybean peptides as the sole active ingredient in postharvest preservation of apple fruit, characterized by: The soybean peptide was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with product number S916495-25g. The postharvest preservation of apples includes: maintaining fruit firmness, reducing fruit ethylene release, maintaining the content of titratable acid and soluble sugar in the fruit, maintaining the activity of superoxide dismutase in the fruit, and reducing fruit browning.

2. A method for preserving apples, characterized in that, Spray the soybean peptide aqueous solution evenly onto the surface of apple fruit, repeating 2-4 times, and store at 0-4℃ after spraying. The concentration of the soybean peptide aqueous solution is 0.05-0.15 g / L, the total spraying amount for each apple is 100-200 mL, and the spraying time is 10-15 min.

Images