Modified carnosine preservative, preparation method thereof and application of modified carnosine preservative in fruit and vegetable preservation
Through the application of modified L-carnosine preservative, the problems of quality decline and shelf life shortening caused by mechanical damage during storage of fresh-cut fruits and vegetables are solved, and the effects of significantly reducing the respiration rate, slowing down weight loss and delaying browning are achieved, maintaining Fruit and vegetable quality and extended shelf life.
Patent Information
- Application Number
- CN202411751973.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-02
- Publication Date
- 2025-01-21
AI Technical Summary
During storage, freshly cut fruits and vegetables accelerate water loss, increased respiration rate, accumulation of pigment and microbial infection, resulting in weight loss, softening, browning and rot, affecting quality and shelf life.
Modified L-carnosine is used as a preservative, and a modified L-carnosine aqueous solution is prepared by mixing and reacting L-carnosine, a protective group and an inorganic base in the presence of an acid-binding agent, which is used to preserve fresh-cut fruits and vegetables.
Modified L-carnosine preservative can significantly reduce the respiration rate of fruits and vegetables, slow down weight loss and browning, maintain the quality of fruits and vegetables, extend the shelf life and increase economic value.
Smart Images
Figure CN119326029A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of fruit and vegetable preservation, and in particular to a modified carnosine preservative, a preparation method and application thereof in preserving fresh-cut fruits and vegetables. Background Art
[0002] Fresh-cut fruits and vegetables are lightly processed products that are ready to eat or use. They can not only maintain the natural freshness and nutritional elements of fruits and vegetables, but also meet consumers' demand for convenient, ready-to-eat and ready-to-use products. Fresh-cut fruits and vegetables are an important development direction for the fruit and vegetable industry.
[0003] Fresh-cut fruits and vegetables will suffer serious mechanical damage. During storage, this damage will stimulate the accelerated water loss of fruits and vegetables, increase the respiration rate and induce pigment accumulation, resulting in weight loss, softening and browning. In addition, cutting will expose the surface of fruits and vegetables, making them susceptible to microbial infection and reproduction, leading to rot and deterioration of fruits and vegetables and shortening of shelf life, ultimately affecting the quality and economic value of fresh-cut fruits and vegetables.
[0004] Currently, there are many edible natural preservatives used to preserve fresh-cut fruits and vegetables, but their further development is limited by factors such as high cost, complex separation and extraction, and unclear chemical structure. Therefore, it is of great significance to develop a new natural preservative that is cheap, easy to obtain, controllable in structure, safe and non-toxic to improve the storage time, quality and shelf life of fresh-cut fruits and vegetables. Summary of the invention
[0005] The purpose of the present invention is to provide a modified L-carnosine preservative, a preparation method and its application in the preservation of fresh-cut fruits and vegetables. This type of preservative has the characteristics of low cost, simple synthesis method and significant preservation effect. During the storage of fresh-cut fruits and vegetables, the modified L-carnosine preservative has the effects of inhibiting the respiration intensity of fruits and vegetables, slowing down weight loss and delaying browning, which helps to maintain the quality of fruits and vegetables, prolong the shelf life of products and enhance their economic value.
[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows: A modified carnosine preservative comprises modified L-carnosine.
[0007] The invention discloses application of the modified L-carnosine in preparing a modified carnosine preservative.
[0008] In the present invention, the active ingredient of the modified carnosine preservative is modified L-carnosine. For example, a modified L-carnosine aqueous solution is used as the modified carnosine preservative. As an example, the modified L-carnosine is prepared into an aqueous solution with a concentration of 1 to 5 mmol / L, preferably 1 to 3 mmol / L, as a modified carnosine preservative, which has a good preservative effect on fresh-cut fruits and vegetables.
[0009] In the present invention, the chemical structure formula of modified L-carnosine is as follows: ; Wherein R is selected from one of the formyl groups; M + For metal ions.
[0010] Preferably, R is selected from tert-butyloxycarbonyl and 9-fluorenylmethoxycarbonyl; M + Selected from one of potassium ion and sodium ion.
[0011] The invention discloses a preparation method of the modified carnosine preservative, comprising the following steps: in the presence of an acid-binding agent, L-carnosine, a protective group and an inorganic base are mixed and reacted to obtain modified L-carnosine; the modified carnosine preservative comprises modified L-carnosine.
[0012] Furthermore, L-carnosine, a protecting group and an acid-binding agent are mixed and reacted, and then the reaction solution is mixed with an inorganic base and the reaction is continued to obtain modified L-carnosine.
[0013] In the present invention, the protective agent is an ester compound; and the acid binding agent is an organic base.
[0014] Preferably, the protecting group is selected from di-tert-butyl dicarbonate and 9-fluorenylmethyl chloroformate.
[0015] Preferably, the acid binding agent is selected from one of triethylamine and 4-dimethylaminopyridine.
[0016] In the present invention, the molar ratio of L-carnosine:protecting group:acid-binding agent is 1:(1-2):(1-3).
[0017] The invention discloses the application of the modified carnosine preservative as or in the preparation of a preservative agent.
[0018] The invention discloses the application of the modified carnosine preservative as or in the preparation of an agricultural product preservative agent.
[0019] The invention discloses a method for preserving agricultural products, which comprises mixing the agricultural products with the modified carnosine preservative to achieve the preservation of the agricultural products.
[0020] In the present invention, agricultural products include fruit and vegetable products; preferably, agricultural products include fresh-cut fruits and vegetables.
[0021] The invention adopts a one-pot method, wherein L-carnosine, a protecting group and an acid-binding agent are reacted in a solvent at room temperature for 5 to 20 hours, preferably 8 to 15 hours, and then the reaction solution is poured into an inorganic alkali solution for reaction for 0.5 to 2 hours to obtain modified L-carnosine. Furthermore, after the reaction is completed, a recrystallization method is used to obtain the modified L-carnosine; and then a modified L-carnosine aqueous solution with a concentration of 1 to 5 mmol / L is prepared to be used as a fruit and vegetable preservative.
[0022] In the present invention, the solvent is selected from one of dichloromethane, chloroform and tetrahydrofuran.
[0023] In the present invention, the inorganic base is selected from one of sodium hydroxide, potassium hydroxide, sodium tert-butoxide and potassium tert-butoxide.
[0024] In the present invention, the solvent of the inorganic alkaline solution is selected from one of water and anhydrous ethanol. Compared with the prior art, the present invention has the following advantages: 1. The modified L-carnosine preservative disclosed in the present invention is derived from the natural product L-carnosine, and the raw material is easily available and low in cost.
[0025] 2. The present invention prepares the preservative modified L-carnosine through a one-pot method in organic synthesis, and its chemical structure is clear, the synthesis method is simple, and it is suitable for large-scale preparation.
[0026] 3. The preservation method disclosed in the present invention has the preservation effect of significantly reducing the respiration rate of fresh-cut fruits and vegetables, slowing down weight loss and inhibiting browning, which can better maintain the quality of fresh-cut fruits and vegetables and improve their economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 Changes in respiration of fresh-cut apples treated with preservatives and the control during storage at room temperature.
[0028] Figure 2 Changes in weight loss of fresh-cut apples treated with preservatives and the control treatment during storage at room temperature.
[0029] Figure 3 Color difference between fresh-cut apples treated with preservatives and those treated with controls when stored at room temperature.
[0030] The error limits and a, b, c, and d in the figures represent statistical differences (p < 0.05). DETAILED DESCRIPTION
[0031] The present invention provides a fresh-cut fruit and vegetable preservative, which is a modified L-carnosine. The preparation method thereof comprises the following steps: dissolving L-carnosine, a protecting group and an acid-binding agent in a solvent, reacting at room temperature for 10 to 13 hours, and then adding the reaction solution into an aqueous solution (8 to 12 wt %) of an inorganic base to obtain the modified L-carnosine, the chemical structure of which is shown in the general formula:
[0032] Wherein R is selected from: one of hydrogen, tert-butyloxycarbonyl, and tert-methoxycarbonyl; M + Selected from: one of potassium ion and sodium ion; The protecting group is selected from: di-tert-butyl dicarbonate, 9-fluorenylmethyl chloroformate; The acid binding agent is selected from: one of triethylamine and 4-dimethylaminopyridine; The solvent is selected from: one of dichloromethane, chloroform and tetrahydrofuran; The inorganic base is selected from: sodium hydroxide, potassium hydroxide, sodium tert-butoxide, potassium tert-butoxide; preferably, the molar ratio of L-carnosine to the inorganic base is 1: (0.8-2), such as 1: (1-1.5).
[0033] In the above technical solution, the molar ratio of L-carnosine:protecting group:acid binding agent is 1.0:1.5:2.0.
[0034] The reaction process of the above technical solution can be expressed as:
[0035] The present invention also provides a method for preserving fresh-cut fruits and vegetables, which comprises soaking the fresh-cut fruits and vegetables in the above-mentioned fruit and vegetable preservative aqueous solution, taking them out after 1 to 3 minutes, draining the water, and storing them at room temperature to achieve fresh-cut fruits and vegetables preservation.
[0036] In the above technical solution, the fruit and vegetable preservative is an aqueous solution of modified L-carnosine, wherein the concentration is 2 mmol / L; In the above technical solution, the fresh-cut fruits and vegetables are apples.
[0037] The present invention will be further described below in conjunction with the embodiments.
[0038] The raw materials used are all commercially available products, the specific preparation operations and performance tests are all conventional techniques, and the statistical difference analysis is a conventional technique.
[0039] Example 1 Synthesis of modified L-carnosine 1
[0040] Taking L-carnosine as raw material, the reaction steps are as follows: (1) L-carnosine (2262 mg, 10 mmol), di-tert-butyl dicarbonate (3274 mg, 15 mmol), 4-dimethylaminopyridine (2443 mg, DMAP) (20 mmol) and chloroform (100 mL) were added to a reaction flask, and the mixture was reacted at room temperature for 12 hours. Subsequently, 40 mL of 10% sodium hydroxide aqueous solution was poured into the reaction solution and reacted for 1 hour; (2) After the reaction, the target product 1 was obtained by GC detection with a yield of 81%. After the solvent was removed by rotary evaporation, the purified product 1 (2821 mg) was recrystallized from ethanol / water (3:2). The analytical data are as follows: 1 H NMR (400 MHz, DMSO- d 6): δ 8.37 (s, 1H), 8.30 (s, 1H), 7.98 (s, 1H), 7.64 (s, 1H), 7.08(s, 1H), 4.82 (t,1H), 3.21 (d, 2H), 3.07 (m ,2H), 2.34 (t, 2H), 1.39 (s, 9H).
[0041] Example 2 Synthesis of modified L-carnosine 2
[0042] Taking L-carnosine as raw material, the reaction steps are as follows: (1) L-carnosine (2262 mg, 10 mmol), 9-fluorenylmethyl chloroformate (3880 mg, 15 mmol), triethylamine (2024 mg, 20 mmol) and dichloromethane (100 mL) were added to a reaction flask, and the mixture was reacted at room temperature for 12 hours. Subsequently, 45 mL of 10% potassium hydroxide aqueous solution was poured into the reaction solution and reacted for 1 hour; (2) After the reaction, the target product 2 was obtained by GC detection with a yield of 84%. After the solvent was removed by rotary evaporation, the purified product 2 (4087 mg) was recrystallized from ethanol / water (3:2). The analytical data are as follows: 1 H NMR (400 MHz, DMSO- d 6): δ 8.39 (s, 1H), 8.31 (s, 1H), 8.00 (s, 1H) 7.28-7.87 (m, 8H), 7.06 (s, 1H), 4.96-4.80 (m, 3H), 3.45 (m, 3H), 3.24 (d, 2H), 2.40 (t, 2H).
[0043] Example 3 Synthesis of modified L-carnosine 3
[0044] Taking L-carnosine as raw material, the reaction steps are as follows: (1) L-carnosine (2262 mg, 10 mmol), di-tert-butyl dicarbonate (3274 mg, 15 mmol), triethylamine (2024 mg, 20 mmol) and tetrahydrofuran (100 mL) were added to a reaction flask, and the mixture was reacted at room temperature for 12 hours. Subsequently, 145 mL of 10% sodium tert-butoxide in anhydrous ethanol was poured into the reaction solution and reacted for 1 hour; (2) After the reaction, the target product 3 was obtained by GC detection with a yield of 87%. After the solvent was removed by rotary evaporation, the purified product 3 (3030 mg) was recrystallized from ethanol / water (3:2). The analytical data are as follows: 1 H NMR (400 MHz, DMSO- d 6): δ 8.37 (s, 1H), 8.30 (s, 1H), 7.96 (s, 1H), 7.64 (s, 1H), 7.06(s, 1H), 4.83 (t,1H), 3.23 (d, 2H), 3.07 (m ,2H), 2.34 (t, 2H), 1.39 (s, 9H).
[0045] Example 4 Synthesis of modified L-carnosine 4
[0046] Taking L-carnosine as raw material, the reaction steps are as follows: (1) L-carnosine (2262 mg, 10 mmol), di-tert-butyl dicarbonate (3274 mg, 15 mmol), triethylamine (2024 mg, 20 mmol) and dichloromethane (100 mL) were added to a reaction flask. The mixture was reacted at room temperature for 12 hours. Subsequently, 225 mL of 10% potassium tert-butoxide in anhydrous ethanol was poured into the reaction solution and reacted for 1 hour. (2) After the reaction, the target product 4 was obtained by GC with a yield of 83%. After the solvent was removed by rotary evaporation, the purified product 4 (3025 mg) was recrystallized from ethanol / water (3:2). The analytical data are as follows: 1 H NMR (400 MHz, DMSO- d 6): δ 8.31 (s, 1H), 7.93 (s, 1H) 7.64 (s, 1H), 7.07(s, 1H), 4.83 (t, 1H), 3.22 (d,2H), 3.06 (m ,2H), 2.35 (t, 2H), 1.37 (s, 9H).
[0047] Example 5 Synthesis of modified L-carnosine 5
[0048] Taking L-carnosine as raw material, the reaction steps are as follows: (1) Add L-carnosine (2262 mg, 10 mmol) and 10% sodium tert-butoxide in anhydrous ethanol (96 mL) (the amount is 1.0 equivalent) to the reaction bottle and react for 1 hour; (2) After the reaction, the target product 5 (2408 mg) was obtained by GC with a yield of 97%. After the solvent was removed by rotary evaporation, the purified product 5 was recrystallized from ethanol / water (3:2). The analytical data are as follows: 1 H NMR (400 MHz, DMSO- d 6): δ 7.95 (s, 1H), 7.00 (s, 1H), 4.85 (t, 1H), 3.22 (d, 2H), 3.06 (m, 2H), 2.35 (t, 2H).
[0049] Application Example 1: Use of modified L-carnosine preservative to preserve fresh-cut apples Preparation of preservative: 2 mmol modified L-carnosine was dissolved in deionized water and diluted to 1000 mL to obtain a modified L-carnosine solution with a concentration of 2 mmol / L as a preservative; CK, water, and L-carnosine were used as comparisons, and CK was a NaClO aqueous solution with a concentration of 0.03% (mass ratio).
[0050] Fresh-cut apple preservation treatment: The experiment was conducted in a completely randomized manner, and each experiment was repeated three times. Select newly picked apples without disease or mechanical damage, soak them in a 0.03% (mass ratio, M / M) NaClO aqueous solution for 3 min for disinfection, then remove them, wash them with clean water, and dry them. Use an apple cutter to cut the apples evenly into pieces, soak them in the preservative solution for 3 min, remove them, drain them, and store them in a constant temperature (26°C) and constant humidity (60%) box.
[0051] Data processing: Data were expressed as mean ± standard error (SE) and analyzed by analysis of variance (ANOVA). p <0.05 indicated a significant difference based on the least significant difference (LSD) test.
[0052] Respiratory rate measurement ( Figure 1 ): Peach fruit respiration rate was measured using a SY-1022 fruit respiration meter. Unit: mg CO2 kg -1 FWf -1 .
[0053] Determination of weight loss ( Figure 2 ): The treated peach fruits were randomly divided into groups, with 10 pieces in each group. Samples were taken and weighed on the day of storage (0 day) and on the 4th, 8th, 12th, 16th, 20th, and 24th days. The weight loss rate of the peach fruit was determined by measuring the weight loss during storage by weighing method, and the weight loss rate was calculated according to the following formula: weight loss rate = (original weight - weight after storage) / original weight × 100%.
[0054] Determination of color difference value ( Figure 3 ): The color of peach pulp was measured using a CR-10 (Japan) colorimeter. The calculation formula is: ΔE=[(L*-L0) 2 +(a*-a0) 2 +(b*-b0) 2 ] 1 / 2 .
[0055] Figure 1 Changes in respiration of fresh-cut apples treated with preservatives and the control treatment when stored at room temperature. Figure 1 Description: The present invention can effectively reduce the respiration rate of fresh-cut apples during storage, thereby extending the storage time and shelf life of the fresh-cut apples.
[0056] Figure 2 Weight loss changes of fresh-cut apples treated with preservatives and control treatments during storage at room temperature. Figure 2 Description: The invention can significantly delay the weight loss of fresh-cut apples during storage, slow down the softening of fresh-cut apples, and help maintain the taste.
[0057] Figure 3 Color difference between fresh-cut apples treated with preservatives and those treated with controls when stored at room temperature. Figure 3 Description: The present invention can inhibit the browning of fresh-cut apples during storage, which is beneficial to maintaining the quality of fresh-cut apples.
[0058] Application results: (1) Compared with other treatments, the respiration rate of fresh-cut apples treated with modified L-carnosine 1 preservative was significantly reduced ( p <0.05, delaying the weight loss of apples and effectively inhibiting their browning ( p <0.05). During storage, the fresh-cut apples better maintained their flavor and quality. Therefore, the preservative, preparation method and application of the present invention can effectively improve the storage quality of fresh-cut fruits and vegetables, extend the shelf life, and help improve the economic value of fresh-cut fruits and vegetables.
Claims
1. A modified carnosine preservative, characterized in that: The modified carnosine preservative comprises modified L-carnosine.
2. The modified carnosine preservative according to claim 1, characterized in that: The general chemical structure of modified L-carnosine is as follows: ； Wherein R is selected from one of the formyl groups; M + For metal ions.
3. The modified carnosine preservative according to claim 1, characterized in that: R is selected from tert-butyloxycarbonyl and 9-fluorenylmethoxycarbonyl; M + Selected from one of potassium ion and sodium ion.
4. The method for preparing the modified carnosine preservative according to claim 1, characterized in that: The method comprises the following steps: in the presence of an acid-binding agent, L-carnosine, a protective group and an inorganic base are mixed and reacted to obtain modified L-carnosine; the modified carnosine preservative comprises modified L-carnosine.
5. The method for preparing the modified carnosine preservative according to claim 4, characterized in that: The protective agent is an ester compound; the acid-binding agent is an organic base.
6. The method for preparing the modified carnosine preservative according to claim 4, characterized in that: L-carnosine, a protecting group and an acid-binding agent are mixed for reaction, and then the reaction solution is mixed with an inorganic base and the reaction is continued to obtain modified L-carnosine.
7. The method for preparing the modified carnosine preservative according to claim 4, characterized in that: In terms of molar ratio, L-carnosine: protecting group: acid-binding agent is 1.0: (1-2): (1-3).
8. The application of modified L-carnosine in preparing a modified carnosine preservative, characterized in that: The general chemical structure of modified L-carnosine is as follows: ； Wherein R is selected from one of the formyl groups; M + For metal ions.
9. Use of the modified carnosine preservative according to claim 1 as or in the preparation of a preservative agent.
10. A method for preserving agricultural products, characterized in that: The agricultural products are mixed with the modified carnosine preservative according to claim 1 to achieve the preservation of the agricultural products.