Application of nicotinamide in anti-browning of apples

Abstract

The invention discloses an application of nicotinamide in anti-browning of apples. The niacinamide aqueous solution is used for treating the fresh-cut apples (Fuji), so that the browning process can be obviously delayed, and the niacinamide aqueous solution has the effects of inhibiting L * value reduction in the fresh-cut apples, inhibiting a * value and b * value increase in the fresh-cut apples, inhibiting O2-and H2O2 content increase in the fresh-cut apples, maintaining SOD and CAT activity of the fresh-cut apples, enhancing oxidation resistance of the fresh-cut surfaces of the apples, and improving the fresh-cut apple quality. The activity of PPO and POD on the surfaces of the fresh-cut apples is inhibited, and the content of total phenols and chlorogenic acid is inhibited. The niacinamide aqueous solution as the fruit and vegetable anti-browning inhibitor can keep fresh, is safe and reliable, and has no toxic or side effect.

Description

Technical Field

[0001] The present invention relates to the technical field of fruit preservation, and in particular to application of nicotinamide in preventing apple from browning. Background Art

[0002] apple( Malus domestica Apple (Prunus mume), a plant of the Rosaceae family, is rich in a variety of nutrients beneficial to the human body, such as polyphenols, flavonoids, and vitamins. Fresh-cut apple processing disrupts the integrity of its cells, causing polyphenol oxidase (PPO) within the cells to come into contact with a large amount of phenolic substrates. Under the action of oxygen, an enzymatic browning reaction rapidly occurs, generating dark brown quinone polymers. This seriously affects the appearance, color, and flavor quality of fresh-cut apples, resulting in waste of food resources and economic losses. Currently, anti-browning technologies for fresh-cut apples primarily involve chemical and physical treatments. Regarding chemical treatments, commonly used anti-browning agents, such as ascorbic acid and its derivatives, can inhibit browning by reducing quinones. However, these agents are susceptible to oxidation and discoloration, are relatively unstable, and their effectiveness is significantly reduced under high-temperature or prolonged storage conditions. Acidic substances such as citric acid can inhibit enzyme activity by lowering pH, but their effectiveness is limited when used alone, and excessive acidity can affect the taste of apples. While sulfites offer significant anti-browning effects, their use poses a food safety risk, potentially triggering allergic reactions in some consumers, and their use in fresh-cut fruit has been restricted or banned in many countries and regions. Physical treatments, such as low-temperature storage and modified atmosphere packaging, can slow the browning process to a certain extent, but they struggle to fundamentally inhibit enzymatic browning reactions. Furthermore, they require high-quality equipment and storage conditions, increasing production costs. Furthermore, existing research on fresh-cut apple anti-browning has largely focused on single anti-browning agents or the optimization of traditional technologies. The development of new, safe, and effective anti-browning agents and the exploration of synergistic mechanisms remain insufficient. Nicotinamide, a water-soluble vitamin B3, is widely used in food, medicine, and cosmetics. It exhibits excellent biosafety and stability (a daily intake of 500-1000 mg is considered safe for humans) and has demonstrated potential in other fields, such as antioxidant and enzyme regulation. However, there are currently no technical solutions for systematically applying nicotinamide to fresh-cut apple anti-browning, and in-depth research on its mechanism of action and optimal application conditions is also lacking. Therefore, there is an urgent need to develop a nicotinamide-based anti-browning method for fresh-cut apples to overcome the shortcomings of existing technologies and enhance the quality and commercial value of fresh-cut apples. Summary of the Invention

[0003] In view of the above prior art, the present invention aims to provide an application of nicotinamide in anti-browning of apples. The present invention sprays the nicotinamide aqueous solution evenly on the surface of fresh-cut fruits, which can inhibit the growth of fresh-cut apples. L* Value decreases, a* Value and b*The value increases, significantly enhancing the antioxidant capacity of the fresh-cut apple surface, inhibiting the PPO and POD activities on the fresh-cut apple surface, and inhibiting the total phenol and chlorogenic acid content. The method of the present invention has a good anti-browning effect and is safe and reliable.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A first aspect of the present invention provides the use of nicotinamide in preventing browning of fruits and vegetables.

[0005] Preferably, the fruits and vegetables are fresh-cut apples.

[0006] Preferably, the fresh-cut apples are Fuji apples.

[0007] Preferably, the nicotinamide achieves anti-browning of fruits and vegetables through at least one of the following pathways (1) to (4): (1) Inhibit the L* The value decreases, inhibiting the a* Value and b* Value increases; (2) Inhibit O in fruits and vegetables 2- and H2O2 content increases, maintaining the activity of SOD and CAT in fruits and vegetables; (3) Inhibit the activity of PPO and POD in fruits and vegetables; (4) Inhibit the content of total phenols and chlorogenic acid in fruits and vegetables.

[0008] A second aspect of the present invention provides a fruit and vegetable browning inhibitor, wherein the fruit and vegetable browning inhibitor contains nicotinamide as an active ingredient.

[0009] Preferably, the inhibitor is obtained by mixing nicotinamide and distilled water; the concentration of the nicotinamide aqueous solution is 1-100 mM / L.

[0010] Preferably, the concentration of the nicotinamide aqueous solution is 10 mM / L.

[0011] A third aspect of the present invention provides a method for preventing browning of fresh-cut apples using a fruit and vegetable browning inhibitor. The method comprises spraying or soaking the cut surface of the fresh-cut apples with the fruit and vegetable browning inhibitor, and then drying the cut surface after treatment to prevent browning of the fresh-cut apples.

[0012] Preferably, the concentration of the fruit and vegetable browning inhibitor is 10 mM / L.

[0013] Preferably, the amount of the spraying treatment is 0.02~0.03mL / cm 2 .

[0014] Beneficial effects of the present invention: The present invention uses nicotinamide aqueous solution to treat fresh-cut apples (Fuji) to significantly delay the browning process, which is manifested by inhibiting the growth ofL* The value decreased and the a* Value and b* The value rises, inhibiting the O 2- It increases the content of H2O2, maintains the activity of SOD and CAT in fresh-cut apples, enhances the antioxidant capacity of the surface of fresh-cut apples, inhibits the activity of PPO and POD on the surface of fresh-cut apples, and suppresses the content of total phenols and chlorogenic acid. It can preserve freshness and is safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 :The phenotype and color value of the browning degree of fresh-cut Fuji apples treated with different concentrations of nicotinamide, where A is the phenotype and B is L* Value, C is a* Value, D is b* value; Figure 2 :Effects of 10 mM / L nicotinamide and distilled water treatment on the antioxidant capacity of fresh-cut Fuji apples, where A is O 2- A is the content, B is the H2O2 content, C is the SOD activity, and D is the CAT activity; Figure 3 :Effects of 10 mM / L nicotinamide and distilled water treatment on the browning-related enzyme activities of fresh-cut Fuji apples, where A represents PPO activity and B represents POD activity; Figure 4 : Effects of 10 mM / L nicotinamide and distilled water treatment on browning-related substrates in fresh-cut Fuji apples, where A is the total phenolic content and B is the chlorogenic acid content. DETAILED DESCRIPTION

[0016] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0017] As described in the background art, after fresh-cut apples, mechanical damage destroys the integrity of the apple cells, causing the PPO in the cells to come into contact with a large amount of phenolic substrates. Under the action of oxygen, an enzymatic browning reaction quickly occurs, generating dark brown quinone polymers. This not only seriously affects the appearance, color, and flavor quality of fresh-cut apples, but also significantly shortens their shelf life, resulting in waste of food resources and economic losses. Nicotinamide, as a water-soluble vitamin, is one of the essential nutrients for organisms and exhibits potential functions such as anti-oxidation and regulation of enzyme activity. However, there is currently no technical solution for applying the nicotinamide system to the anti-browning of fresh-cut apples.

[0018] Based on this, the inventors conducted a systematic study on the role of nicotinamide in preventing browning in fresh-cut apples. Nicotinamide was sprayed on fresh-cut Fuji apples to examine its effects on physiological indicators such as the degree of browning on the fruit's cut surface, antioxidant capacity, PPO and POD activity, and total phenolic and chlorogenic acid content. The results showed that nicotinamide significantly inhibited the browning of fresh-cut apples; significantly enhanced the antioxidant capacity of the fresh-cut apple surface; inhibited the activity of the browning-related enzymes PPO and POD on the fresh-cut apple surface; and reduced the content of total phenolic and chlorogenic acid, browning-related substrates. In summary, nicotinamide demonstrates broad potential for inhibiting browning in fresh-cut apples.

[0019] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below with reference to specific embodiments.

[0020] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0021] Example Nicotinamide was added to distilled water to prepare aqueous solutions of nicotinamide at concentrations of 1, 10, and 100 mM / L. The aqueous solution of nicotinamide was diluted at 0.026 mL / cm 2 Spray onto the cut surface of fresh-cut apples respectively. After drying, the fresh-cut apples can be protected from browning.

[0022] Test example 1. Test methods 1.1 Trial Grouping and Treatment Four Fuji apple fruits (each with a transverse diameter of 75-85 mm) from the same batch, variety, and specifications, with no differences in freshness, were selected. The apples were evenly cut using a stainless steel apple splitter. 16 apple slices of consistent size and weight were selected and divided into four groups, with four slices in each group (from different apples, ensuring both biological replication for each sample group and consistency in sample source between groups). 1 mL of 1, 10, or 100 mM nicotinamide solution was evenly sprayed on the surface of the cut apple flesh (sprayed three times, approximately 0.33 mL each time, with a spray volume of approximately 0.026 mL / cm). 2 The control group was sprayed with an equal amount of distilled water. The treated samples were placed in an environment with a temperature of 25 ± 1°C and a humidity of 60 ± 5%. Colorimetric measurements, photographs, and sampling were performed at 0, 12, 24, 48, and 72 hours.

[0023] The surface chromaticity of apple slices was measured using a Konica Minolta CR-400 colorimeter (Tokyo, Japan). Each sample was measured three times and the average value was obtained. The brightness value was obtained based on the CIELAB color space ( L* )、Red and Green Value(a* ) and yellow-blue values ​​( b* ), the optimal application concentration of nicotinamide was found by quantifying the color difference values ​​of each group of fruits. Figure 1 .

[0024] According to the optimal application concentration of niacin mentioned above, the O 2- and H2O2 content, SOD and CAT activities, PPO and POD activities, total phenolic and chlorogenic acid contents. Figure 2-4 .

[0025] For all the above spraying methods, the spraying amount was 1 mL / apple slice, and the apples were stored at room temperature of 25°C after spraying.

[0026] 1.2 Detection method 1.2.1 Detection methods of antioxidant capacity indicators O 2- , H2O2, SOD, and CAT content were determined using dedicated test kits from Suzhou Keming Biotechnology Co., Ltd. 0.5 g of fresh apple tissue was added to 5 mL of pre-chilled 50 mM phosphate buffer (pH 7.8). The tissue was thoroughly homogenized in an ice bath using a tissue homogenizer. The sample was then centrifuged at 12,000 × g for 20 minutes at 4°C. The supernatant was then assayed according to the respective kit instructions.

[0027] 1.2.2 Detection methods of browning-related enzyme activities PPO and POD PPO and POD activities were determined using spectrophotometric assay kits from Suzhou Kangming Biotechnology Co., Ltd. 0.5 g of apple tissue was added to 5 mL of pre-chilled extraction buffer (provided with the kit), homogenized in an ice bath, and centrifuged at 12,000 × g for 15 min at 4°C. The supernatant was collected and assayed according to the kit instructions.

[0028] 1.2.3 Detection methods for total phenolic and chlorogenic acid content in browning-related substrates 1.2.3.1 Total phenols were determined using the Folin-Ciocalteu method Weigh 0.2 g of fresh sample into a 15 ml centrifuge tube, add 10 ml of extraction solution (2% hydrochloric acid in methanol), shake in the dark for 4 h, then centrifuge at 4°C and 5000 g for 10 min, and take the supernatant for testing.

[0029] Place 40 μL of the test solution in a 10 mL centrifuge tube, add 1 mL of folin-phenol solution, 0.8 mL of 7.5% sodium carbonate solution, and 0.16 mL of distilled water. After gentle shaking for 15 minutes, measure the absorbance at 765 nm using a spectrophotometer. Construct a standard curve using gallic acid as the standard, and calculate the total phenol content based on the absorbance. Perform three replicates for each sample and calculate the average value.

[0030] 1.2.3.2 Determination of chlorogenic acid using HPLC Chlorogenic acid standard (purity ≥98%, purchased from Shanghai Yuyuan Biotechnology Co., Ltd.); chromatography-grade acetonitrile; analytical-grade phosphoric acid; and ultrapure water. All solutions were filtered through a 0.45 μm microporous membrane before use. An Agilent 1260 Infinity II HPLC system equipped with a DAD detector was used. The chromatographic column was a Thermo Hypersil GOLD C18 column (250 mm × 4.6 mm, 5 μm), and the column temperature was 30°C. The mobile phase consisted of 0.5% aqueous phosphoric acid (A) and acetonitrile (B), with a volume ratio of 90:10, isocratic elution. The flow rate was 1.0 mL / min, and the detection wavelength was 330 nm. The injection volume was 20 μL.

[0031] Grind apple tissue into a powder in a liquid nitrogen-cooled mortar. Weigh 0.75 g of the tissue and homogenize it in 20 mL of pre-chilled 80% ethanol. Centrifuge at 10,000 × g for 10 min at 4°C. Collect the supernatant and dilute to 50 mL with 80% ethanol. Filter a portion of the solution through a 0.45 μm microporous membrane and transfer to a sample vial for analysis.

[0032] Accurately weigh the chlorogenic acid standard and dilute to volume with 80% ethanol to prepare standard solutions at concentrations of 1.0, 5.0, 10.0, 20.0, 50.0, and 100.0 μg / mL. Calculate the standard curve equation based on the peak area and concentration. Substitute the peak area of ​​the sample solution into the equation to calculate the chlorogenic acid content.

[0033] 1.3 Test results The test results are shown in Figures 1-4 .

[0034] Figure 1 The phenotype and chromaticity values ​​of the browning degree of fresh-cut Fuji apples at 0, 12, 24, 48, and 72 h after exposure to different concentrations of nicotinamide are shown. The chromaticity values ​​include the brightness value ( L* )、Red and Green Value( a* ) and yellow-blue values ​​( b* ).from Figure 1As can be seen in Figure A, nicotinamide has a significant inhibitory effect on the browning of fresh-cut apples, with 10mM and 100mM concentrations showing the best effect. Figures B, C, and D show the brightness values ​​of each surface ( L* )、Red and Green Value( a* ) and yellow-blue values ​​( b* ). After the apple is cut, the surface is in contact with the air. L* The value gradually decreases, a* Value and b* The value gradually increased, and nicotinamide treatment significantly inhibited L* The decrease in value and a*b* However, a comparison of the effects of nicotinamide on apple browning and color values ​​at concentrations ranging from 1 to 100 mM revealed no statistically significant difference between 10 mM and 100 mM. Considering the cost, 10 mM / L was selected as the optimal concentration for subsequent experiments.

[0035] Figure 2 The effects of 10 mM / L nicotinic acid and distilled water on the antioxidant capacity of fresh-cut Fuji apples are shown in Figure 2. 2- , H2O2, SOD and CAT. Figure 2 It can be seen that after the apple is freshly cut and exposed to the air, the oxidative stress index O 2- The content of H2O2 increased significantly, and the antioxidant enzymes SOD and CAT decreased significantly. Nicotinamide treatment can significantly increase the activity of SOD and CAT on the surface of fresh-cut apples, and significantly reduce O 2- and H2O2 content. This shows that nicotinamide can accelerate the oxidation of 2- and H2O2, thereby effectively alleviating oxidative stress.

[0036] Figure 3 The effects of 10 mM / L nicotinamide and distilled water treatment on the activities of PPO and POD, enzymes involved in browning, in fresh-cut Fuji apples. PPO and POD activities showed a continuous upward trend from 0 to 72 hours, providing catalytic conditions for the browning reaction. The increase in activity was particularly significant from 0 to 24 hours, suggesting that browning primarily occurs during the early stages of fresh-cut apples. Comparing the increases in enzyme activity revealed that PPO activity increased significantly more than POD, suggesting that it may play a more critical catalytic role in the browning process. Treatment with 10 mM / L nicotinamide effectively inhibited the increase in PPO and POD activity, demonstrating that nicotinamide can block the browning process at the enzymatic level.

[0037] Figure 4The effects of 10 mM / L niacinamide and distilled water on the browning substrates—total phenols and chlorogenic acid—in fresh-cut Fuji apples. Total phenolic content continued to rise after fresh-cut, reaching a peak after 48 hours. Chlorogenic acid, a key substrate for browning, also showed a gradual increase. Treatment with 10 mM / L niacinamide significantly inhibited the upward trend in total phenolic content. Although still above initial levels, the rate of increase slowed significantly. Nicotinamide also significantly regulated chlorogenic acid content, effectively maintaining it at its initial level. This suggests that niacinamide can modulate the content of browning substrates, weakening the conditions for browning at a material level. This, in conjunction with enzyme inhibition, provides a multi-dimensional basis for controlling browning in fresh-cut apples.

[0038] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. Application of niacinamide in anti-browning of fruits and vegetables.

2. The use according to claim 1, characterized in that The fruits and vegetables are fresh-cut apples.

3. The use according to claim 1, characterized in that The nicotinamide achieves anti-browning of fruits and vegetables through at least one of the following pathways (1) to (4): (1) Inhibit the L* The value decreases, inhibiting the a* Value and b* Value increases; (2) Inhibit O in fruits and vegetables 2- and H2O2 content increases, maintaining the activity of SOD and CAT in fruits and vegetables; (3) Inhibit the activity of PPO and POD in fruits and vegetables; (4) Inhibit the content of total phenols and chlorogenic acid in fruits and vegetables.

4. A fruit and vegetable browning inhibitor, characterized in that: The fruit and vegetable browning inhibitor uses nicotinamide as an effective ingredient.

5. The fruit and vegetable browning inhibitor according to claim 4, characterized in that The inhibitor is obtained by mixing nicotinamide and distilled water; the concentration of the nicotinamide aqueous solution is 1-100 mM / L.

6. The fruit and vegetable browning inhibitor according to claim 5, characterized in that The concentration of the nicotinamide aqueous solution is 10 mM / L.

7. A method for preventing fresh-cut apples from browning using the fruit and vegetable browning inhibitor according to claims 4 to 6, characterized in that: The method comprises spraying or soaking the cut surface of fresh-cut apples with the fruit and vegetable browning inhibitor according to claims 4 to 6, and then drying the cut surface after the treatment, thereby achieving anti-browning of the fresh-cut apples.

8. The method according to claim 7, characterized in that The concentration of the fruit and vegetable browning inhibitor is 10 mM / L.

9. The method according to claim 7, characterized in that The dosage of the spraying treatment is 0.02~0.03mL / cm 2 .

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