Chitosan oligosaccharide derivative capable of stabilizing vitamin C in aqueous solution as well as preparation method and application of chitosan oligosaccharide derivative

Abstract

The invention relates to a chitosan oligosaccharide derivative capable of stabilizing vitamin C in an aqueous solution as well as a preparation method and application of the chitosan oligosaccharide derivative. Different acyl groups are introduced to amino groups of glycine, acylated glycine is coupled to amino groups of chitosan oligosaccharide molecules, the proportion of the two acyl groups is controlled, and the water solubility of the derivative is improved through acetylglycine, so that the vitamin C in the aqueous solution can be stabilized. Through huge hydrophobicity of cinnamyl, attack of part of oxygen molecules to vitamin C molecules is blocked, so that a relatively good protection effect is achieved. The main raw materials are all green and pure natural raw materials, other synthesis raw materials belong to low-toxicity or non-toxic reagents and are cheap and easy to obtain, the reaction is simple, the reaction condition is mild, the yield is high, the reaction can be quantified, industrial mass production is easy to realize, and byproducts involved in the synthesis process can be recycled, so that the preparation cost is greatly saved.

Description

Technical Field

[0001] The invention relates to the field of additives, and in particular to a chitosan oligosaccharide derivative capable of stabilizing vitamin C in aqueous solution, and a preparation method and application thereof. Background Art

[0002] Vitamin C, also known as ascorbic acid, is a water-soluble vitamin with the chemical name of L-threose-2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone. Vitamin C has strong reducing properties and is a natural, highly effective antioxidant that can effectively remove free radicals produced by the human body, participate in many important biosynthetic processes, and improve the body's immunity. At the same time, vitamin C can also effectively inhibit the secretion of tyrosinase, reduce the synthesis and deposition of cellular melanin; it can also directly penetrate the skin and repair damage caused by ultraviolet rays, so it has a whitening effect.

[0003] In aqueous solution, vitamin C mainly exists in the enol structure. The two adjacent enol hydroxyl groups in the molecular structure are very easy to dissociate and release H+, so it is acidic.

[0004] The dienol structure of the molecule is easily oxidized to a diketone group and inactivated; at the same time, its lactone structure is also extremely unstable and is easily opened in the presence of oxygen, heat, light and alkaline conditions, especially in the presence of oxidases, copper, iron and other metal ions, it is very easy to be oxidized and destroyed. This is also the main reason why the content of some vitamin C-containing beverages decreases significantly after a certain storage period or shortly after opening. In the pasteurization process of beverages, the loss of vitamin C content varies with the temperature and time of the disinfection.

[0005] Judging from the oxidation site of the vitamin C molecule, the key to stabilizing vitamin C is to protect the two hydroxyl groups on carbons 2 and 3 from attack by oxidants. At present, the main methods for maintaining the stability of vitamin C are: 1) polymer protection method, that is, using carboxymethyl cellulose, chitosan, pectin, agar, polyethylene glycol, polyglutamic acid, polyols (such as glycerol) and other hydroxyl-rich substances, which can form multiple hydrogen bonds with vitamin C to form a certain complex, thereby stabilizing vitamin C; 2) microcapsule encapsulation method, that is, using cyclodextrin, liposomes, liposomes, etc. to encapsulate vitamin C; 3) emulsion protection method, that is, using non-ionic surfactants (such as Span-80 and Tween-80) and oily raw materials (such as palm oil, etc.) to prepare a solution containing vitamin C into a W / O / W emulsion, trying to make the solution containing vitamin C exist in the inner water phase, and using the encapsulation of the intermediate oil phase to effectively protect vitamin C; 4) derivatization protection method, that is, making vitamin C into derivatives, such as vitamin C ethyl ether, vitamin C glucoside, vitamin C sodium phosphate, etc.

[0006] Among the above protection methods, the polymer protection method is low in cost, simple in method, and most widely used. The advantage of this method is that the polymer skeleton provides a certain rigid structure, which is conducive to the stable binding of vitamin C thereto, but due to the poor matching of the formed complex structure, it is easily decomposed by the hydrogen bonds of water in the solution, and the protection effect is limited. The microcapsule encapsulation method has a very low encapsulation rate for vitamin C, and the stabilization effect is not ideal. The emulsion protection method requires a large amount of emulsifiers, which seriously affects the taste of the finished product and is not widely used. The derivatization protection cost is high and the application range is not wide.

[0007] In the era of advocating green and healthy food, the development of healthy drinks with high antioxidant properties using pure natural materials has become a potential pursuit of people. In particular, effectively improving the stability of vitamin C in water-soluble beverages is of great significance to improving the quality of beverages. After searching, no reports have been found on this type of oligomer with vitamin C protective function. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention proposes a chitosan oligosaccharide derivative capable of stabilizing vitamin C in aqueous solution, and a preparation method and application thereof. The present invention uses chitosan oligosaccharide as a carrier and designs a chitosan oligosaccharide derivative having a better matching structure with vitamin C molecules by coupling acyl glycine on the amino group thereof.

[0009] The technical solution of the present invention is as follows: A chitosan oligosaccharide derivative capable of stabilizing vitamin C in aqueous solution, the molecular structure of which is as follows: Denoted as C(A)GCO; where n=2~20.

[0010] A method for preparing the chitosan oligosaccharide derivative as described above comprises the following steps: Step 1) dissolve glycine and sodium carbonate in deionized water, cool to 0°C, add DMF solution of cinnamoyl chloride dropwise, stir for 2-4 h to complete the reaction; acidify with concentrated hydrochloric acid to pH = 1-2, then extract with ethyl acetate, wash, add anhydrous sodium sulfate and dry for 4-6 h; filter to remove the desiccant, and rotary evaporate the filtrate to obtain cinnamoyl glycine as a white solid product; Step 2) dissolving acetylglycine and the product of step 1) in DMF in a certain ratio to obtain a DMF mixed solution, adding triethylamine, cooling to 0°C, adding an equivalent amount of pivaloyl chloride solution dropwise, gradually heating to room temperature and reacting for 2h, filtering to remove white precipitate, and obtaining a mixed anhydride solution; Step 3) Weigh appropriate amounts of chitosan oligosaccharide and sodium carbonate and dissolve them in a certain amount of deionized water, add the mixed anhydride solution obtained in step 2) dropwise, react for 3-4 hours, filter the reaction solution, precipitate and filter with n-propanol, concentrate the centrifuged liquid to 1 / 4, precipitate the filtrate with solvent A, centrifuge and vacuum dry to obtain a chitosan oligosaccharide derivative (C(A)GCO).

[0011] Preferably, the molar ratio of the raw materials in step 1) is: glycine: sodium carbonate: cinnamoyl chloride = 1: 1.1-1.3: 1.1-1.4.

[0012] Preferably, the molar ratio of the raw materials in step 2) is: acetylglycine: cinnamoylglycine = 1: 1-3.

[0013] Preferably, the molar ratio of the raw materials is: DMF mixed solution: triethylamine: pivaloyl chloride = 1: 1.0-1.05: 1.0-1.05.

[0014] Preferably, the molar ratio of the raw materials in step 3) is: mixed anhydride solution: sodium carbonate: chitosan oligosaccharide = 1: 1.0-1.05: 0.9-1.05.

[0015] Preferably, the solvent A used in step 3) is selected from tetrahydrofuran, ethyl acetate or propyl acetate.

[0016] The crude product obtained by the above process can also be used to obtain fine products according to the needs of different users by the following method: dissolve the crude chitosan oligosaccharide derivative in an appropriate amount of water, add n-propanol for secondary precipitation, centrifuge, and vacuum dry to obtain a product with higher purity.

[0017] The invention relates to an application of the chitosan oligosaccharide derivative as a vitamin C protective agent in aqueous solution.

[0018] The chitosan oligosaccharide in the present invention is also called chitosan oligosaccharide or low-molecular chitosan. It is an oligosaccharide product obtained by degrading chitosan and having a polymerization degree of 2 to 20 and a molecular weight of ≤3200Da, which is composed of β-1,4-glycosidic bonds. Because its molecular structure is rich in highly polar hydroxyl and amino groups, it has excellent water solubility. However, due to the presence of amino groups on chitosan oligosaccharide (which can undergo Maillard reaction with carbonyl groups), it cannot be directly used to protect vitamin C. The amino groups must be derivatized to form derivatives that are stable in spatial structure. If the two enol hydroxyl structures of the vitamin C molecule can be matched with the polar groups of the rigid structure of chitosan oligosaccharide to undergo multi-site hydrogen bonding (i.e., firmly adhere to the molecular chain of the polymer), the purpose of effectively stabilizing vitamin C can be achieved.

[0019] This case found that if a certain N-acyl amino acid acyl group is introduced into the amino group of chitosan oligosaccharide, the small peptide chain formed thereby can form a "T"-shaped conformation with the chitosan oligosaccharide skeleton in space. The carbonyl oxygen and imino groups on the small peptide chain, as well as the multiple hydroxyl groups on the chitosan oligosaccharide skeleton, can form multiple hydrogen bonds with vitamin C in different directions, forming a better match with the vitamin C molecular structure, which is very beneficial to the stability of vitamin C.

[0020] In the present invention, cinnamic acid (scientific name 3-phenyl-2-acrylic acid) is an edible flavoring agent allowed for use in my country, which can be used as a plant growth regulator and bactericide, a preservative for fruits and vegetables, an ultraviolet agent, etc., and is widely used in the flavoring industry and the pharmaceutical industry. Since the carbonyl group in the molecular structure of cinnamic acid and the connected carbon-carbon double bond and the benzene ring can form a conjugated system, the entire molecule can be kept in a plane. When the cinnamoyl group is coupled to the amino group of the amino acid, this planar structure will not hinder the vitamin C molecule from approaching the "T"-shaped structure part on the chitosan oligosaccharide to form a complex due to molecular folding. The styryl group has a large hydrophobicity, which can form a certain hydrophobic area on both sides of the chitosan oligosaccharide derivative skeleton on the one hand, and the oxygen molecule is a non-polar molecule, which is easier to enter therein, thereby reducing the concentration of oxygen molecules attacking the vitamin C molecules, thereby achieving the effect of protecting the vitamin C molecules. On the other hand, this hydrophobic region is easy to bind to the hydrophobic region on the surface of the microbial cell membrane. Since the styrene group is connected to the chitosan oligosaccharide structure through amino acids (equivalent to extending the length of 2 carbon chains), it can be inserted into the interior of the hydrophobic protein (mainly the enzyme on the surface of the cell membrane), thereby affecting the activity of the enzyme; at the same time, chitosan oligosaccharide itself has a strong film-forming property. Once a film is formed on the surface of the cell (the molecular weight of chitosan oligosaccharide is small, and the density of the formed film is higher than that of chitosan), it will definitely affect the cell's acquisition of external nutrients. Therefore, this chitosan oligosaccharide derivative will have a certain bactericidal or antibacterial effect. Generally speaking, the content of vitamin C in food or beverages is not high, and not too much protective agent is needed. Therefore, this chitosan oligosaccharide derivative used as a vitamin C protective group only needs to play an antibacterial role.

[0021] In the present invention, glycine is selected as the amino acid used. This is because when the mixed anhydride is prepared by the pivaloyl chloride method, the amino group can theoretically attack any carbonyl carbon atom in the anhydride. From the molecular structure of the anhydride, due to the steric hindrance and electron-donating effect of the tert-butyl group, the reaction activity of the nucleophilic reaction on the carbonyl carbon atom of the anhydride connected to the tert-butyl group is low, so the amino group mainly attacks the other carbonyl carbon atom of the anhydride (i.e., the carbonyl carbon atom at the end of the amino acid) and the carbonyl carbon atom on the target carboxylic acid side.

[0022] Compared with other amino acids, glycine is selected as the supporting amino acid in this case to reduce the influence of effective coupling caused by the steric hindrance caused by the side chain residues. Since the anhydride has high activity, the coupling efficiency is also high.

[0023] Another object of the present invention is to provide the application of the above C(A)GCO in protecting vitamin C in aqueous solution. Taking the preparation of sugar water containing vitamin C as an example, the following components are calculated by mass percentage: sucrose 2%, vitamin C 0.1%, citric acid 0.63%, sodium citrate 0.45%, C(A)GCO 0.3%, potassium sorbate 0.02%, and the balance is drinking water. For the convenience of comparison, the formula of C(A)GCO is used as a control.

[0024] S1. Heat the drinking water to boiling for 15 minutes and cool it for later use; S2 weighed sucrose, citric acid, sodium citrate, potassium sorbate according to the ratio, added to the sterilized container 1, dissolved in water prepared by S1; S3 weighed vitamin C, C (A) GCO according to the ratio was added to the sterilized container 2, dissolved in water prepared in S1; S4. Mix the solutions obtained in S2 and S3, fill, pasteurize (90℃75s) and cool to obtain the finished product.

[0025] The advantages of the present invention are: (1) From the perspective of molecular design, the double bond of the cinnamoyl group is conjugated with the benzene ring to keep the molecule in a planar structure. The small peptide chain formed after coupling is a rigid structure, which is conducive to the stability of the "T" configuration of the branched structure formed on the amino group of chitosan oligosaccharide, and will not cause the vitamin C molecule to be unable to approach the chitosan oligosaccharide skeleton and bind to it due to self-folding; (2) Different acyl groups are introduced into the amino group of glycine, and then the acylated glycine is coupled to the amino group of the chitosan oligosaccharide molecule. The ratio of the two acyl groups is controlled, and the water solubility of the derivative is improved by acetylglycine. The huge hydrophobicity of the cinnamoyl group is used to block the attack of some oxygen molecules on the vitamin C molecules, thereby achieving a better protective effect.

[0026] (3) All the main raw materials are green and pure natural raw materials, and other synthetic raw materials are low-toxic or non-toxic reagents, cheap and easy to obtain, simple reaction, mild reaction conditions, high yield, quantitative reaction, and easy to achieve industrial mass production. Most of the by-products involved in the synthesis process (such as acetic acid, triethylamine hydrochloride, pivalic acid, etc.) can be recycled, thereby greatly saving the preparation cost.

[0027] The beneficial effects of the present invention are as follows: 1. It can achieve the purpose of protecting vitamin C in aqueous solution (or delaying its oxidation time).

[0028] 2. It can improve the antioxidant properties of vitamin C aqueous solution.

[0029] 3. Due to its antibacterial properties, it can reduce the amount of preservatives in the vitamin C aqueous solution.

[0030] 4. The present invention adopts the pivaloyl chloride method to couple carboxylic acid and amino group, that is, carboxylic acid reacts with pivaloyl chloride to generate corresponding carboxylic acid-pivalic anhydride, which is then coupled with amino group. This method has high yield and low production cost and is very suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the H NMR spectrum of cinnamoylglycine prepared in Example 1.

[0032] Figure 2 This is the C NMR spectrum of cinnamoylglycine prepared in Example 1.

[0033] Figure 3 This is the infrared spectrum of C(A)GCO prepared in Example 1.

[0034] Figure 4 This is the UV test spectrum of C(A)GCO prepared in Example 1 (the concentration is 72 μg / mL).

[0035] Figure 5 This is a comparison chart of the antibacterial effects of the prepared C(A)GCO at a concentration of 60 mg / mL; A: Staphylococcus aureus; B: Escherichia coli.

[0036] Figure 6 This is the UV scanning diagram in 1% hydrochloric acid after adding different concentrations of C(A)GCO to the Vc solution.

[0037] Figure 7 This is the optimized configuration diagram of the complex formed by vitamin C and C(A)GCO monomer for computer simulation.

[0038] Figure 8 This is a graph showing the decrease in the UV absorption value of vitamin C in 1% hydrochloric acid medium after adding different proportions of C(A)GCO to vitamin C solution (90.9μM) and treating it in a 90℃ water bath for 75s.

[0039] Fig. 9 This is the UV scanning peak change diagram of VC concentration after adding C(A)GCO into VC aqueous solution during storage time (λ=243nm, 1% HCl).

[0040] Fig.10 This is a graph showing the temporal variation trend of vitamin C concentration after adding C(A)GCO to the vitamin C-containing sugar water (λ=252nm, 1% HCl). DETAILED DESCRIPTION

[0041] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0043] Embodiment 1: The molecular reaction formula for synthesizing chitosan oligosaccharide derivatives is as follows: Among them, n=2~20.

[0044] Step 1) Dissolve 150 mg of glycine and 212 mg of sodium carbonate in an appropriate amount of deionized water, cool to 0°C, add 10 mL of DMF solution containing 341 mg of cinnamoyl chloride dropwise, and stir for 2 to 4 hours to complete the reaction. Acidify with concentrated hydrochloric acid to pH = 1 to 2, then extract with 5 mL of ethyl acetate three times, wash and add anhydrous sodium sulfate to dry for 4 to 6 hours; filter to remove the desiccant, and rotary evaporate the filtrate to obtain a white solid product, cinnamoyl glycine; Characterized by NMR, H spectrum (see attached Figure 1 ) and carbon spectrum (attached Figure 2 ) The results are as follows: 1H NMR (400 MHz, DMSO-d6) δ12.52 (s, 1H), 8.42 (t, J = 6.0 Hz, 1H), 7.58 (d, J = 6.7 Hz, 2H), 7.48-7.36 (m, 4H), 6.73 (d, J = 15.8 Hz, 1H), 3.90 (d, J = 5.9 Hz, 2H); 13C NMR (100 MHz, DMSO-d6) δ171.33, 165.28, 139.20, 134.80, 129.56, 128.96, 127.59,121.68, 40.83.

[0045] Step 2) Dissolve 70 mg of acetylglycine and 287 mg of the product of step 1) in 8 ml of DMF, add 287 μL of triethylamine, cool to 0°C, add 254 μL of pivaloyl chloride solution dropwise, gradually warm to room temperature and react for 2 h, filter to remove the white precipitate, and obtain a mixed anhydride solution; Step 3) Weigh 322 mg of chitosan oligosaccharide and 212 mg of sodium carbonate and dissolve them in a certain amount of deionized water, add the mixed anhydride solution obtained in step 2) dropwise, react for 3-4 hours, filter the reaction solution, precipitate and filter with n-propanol, concentrate the centrifuged liquid to 1 / 4, precipitate the filtrate with ethyl acetate after filtration, centrifuge and vacuum dry to obtain the chitosan oligosaccharide derivative.

[0046] According to elemental analysis, the content of each element is: C56.8%, N9.6%, O33.6%, which is basically consistent with the theoretical results (C57.6%, N9.2%, O33.2%).

[0047] The infrared spectrum of C(A)GCO prepared by this method is shown in the attached figure. Figure 3 shown.

[0048] In the attached Figure 3 The broad peak near 3294 cm-1 is mainly the stretching vibration peak of OH on the hydroxyl group and NH on the amide group on glucosamine, and the absorption near 2930 cm-1~2810 cm-1 is the stretching vibration peak of the CH bond on the carbon-carbon double bond; the absorption at 1632 cm-1~1597 cm-1 is mainly the conjugation of the stretching vibration peak of the amide bond and the characteristic absorption peak of the benzene ring skeleton vibration.

[0049] The UV spectra of C(A)GCO and raw chitosan oligosaccharide (CO) prepared by this method are shown in the attached figure. Figure 4 As shown in the figure, the raw chitosan oligosaccharide has almost no absorption peak in the wavelength range of 200 nm – 400 nm, and after the reaction, there are obvious absorption peaks at 218 nm and 280 nm. The peak shape is similar to the ultraviolet spectrum of cinnamic acid in the literature, indicating the presence of cinnamoyl groups in the product.

[0050] Attached Figure 5 The following is a picture showing the inhibitory effect of the prepared C(A)GCO on the culture of Escherichia coli and Staphylococcus aureus at a concentration of 60 mg / mL (Oxford cup method). Figure 5It can be seen that C(A)GCO forms obvious inhibition zones or rings (both with diameters greater than 7 mm) for both bacteria at the action concentration, among which the inhibition zone for Staphylococcus aureus is larger than that for Escherichia coli, indicating that C(A)GCO has significant antibacterial effects on both bacteria. The reason for the formation of the inhibition zone for Staphylococcus aureus may be that the C(A)GCO sample solution is added to the Oxford cup, and C(A)GCO produces a diffusion effect on the culture medium. Since the derivatives are composed of oligomers of different molecular weights, oligomers with small molecular weight diffuse faster, while those with large molecular weight diffuse relatively slowly. Oligomers with small molecular weight bind to bacteria in large numbers and have good antibacterial effects, while oligomers with large molecular weight bind to bacteria less and have poor antibacterial effects. There are still oligomers with high concentrations that have not diffused in the Oxford cup, so the Oxford cup also produces an antibacterial effect.

[0051] Embodiment 2: In order to confirm the existence of a strong molecular interaction between C(A)GCO and VC molecules, the method is as follows.

[0052] Prepare 1 mg / mL C(A)GCO and VC aqueous solutions respectively, take 120 μL vitamin C solution, add C(A)GCO solution according to the ratio (1:1.25, 1:1.33, 1:42), dilute with water to 5 mL, scan its UV absorption, the results are shown in Figure 6 .

[0053] Figure 6 In the ultraviolet absorption spectrum of VC solution, there is a maximum absorption peak at 243 nm, while the spectrum of the mixed aqueous solution of C(A)GCO and VC has an absorption spectrum at 280 nm-317 nm that is obviously different from VC, in addition to the maximum absorption peak at 243 nm. As the proportion of C(A)GCO in the mixed solution increases, the absorption at 243 nm shows a decreasing trend. This shows that as the concentration of C(A)GCO in the solution increases, the amount of complexes formed between it and VC increases, which is reflected in the ultraviolet absorption spectrum, causing the absorption at 243 nm to decrease. Therefore, it is confirmed that there is a strong molecular interaction between C(A)GCO and VC molecules.

[0054] Figure 7 The diagram of the molecular structure coordination of C(A)GCO and VC under vacuum conditions simulated by computer. The hydroxyl groups on carbons 2, 3 and 5 in the VC molecular structure form three hydrogen bonds with the amide group in the middle of the C(A)GCO molecular structure and the hydroxyl oxygen atom on C1 of the pyran ring, respectively. Obviously, the formation of this hydrogen bond is related to the "T" structure of the C(A)GCO molecule.

[0055] Embodiment 3: In order to find out the amount of C(A)GCO added to the solution to protect the VC molecules, the method is as follows.

[0056] Prepare 1 mg / mL C(A)GCO and VC aqueous solutions respectively, take 120 μL vitamin C solution, add C(A)GCO solution according to the ratio (1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8), dilute to 5 mL with water, and scan its UV absorption spectrum; put each ratio solution into a 90℃ water bath for 75s, quickly put into ice water to cool, and scan its UV absorption spectrum. Use blank VC solution as control. Compare the decrease in the UV absorption peak of VC content at λ=243nm (1% hydrochloric acid medium) after heating treatment of each ratio solution. The results are shown in Figure 8 .

[0057] Depend on Figure 8 It can be seen that after the blank VC solution is heated, the peak value at λ=243nm of the UV scan can drop by up to 0.32, and when the ratio of C(A)GCO added reaches 1.7, the UV absorption peak drops by only 0.054 and reaches an inflection point on the spectrum line. Continuing to add C(A)GCO does not significantly improve the protective effect of VC, so this ratio is a suitable addition ratio.

[0058] Example 4 In order to verify the protective effect of C(A)GCO on VC molecules in aqueous solution, the method was as follows.

[0059] Prepare 1 mg / mL VC aqueous solution, add C(A)GCO at a ratio of 1:1.7, dissolve by ultrasonic, mix evenly, and store in a 4°C refrigerator. Take samples weekly and perform UV scanning in 1% hydrochloric acid to compare the changes in the VC absorption peak. Use blank VC solution as control. Fig. 9 .

[0060] Fig. 9 In the first 4 weeks, the UV absorption values ​​of VC in the two samples almost showed a linear decline, and the trend of the spectrum line change slowed down significantly after 4 weeks. There was a significant difference between the UV absorption spectra of VC in the sample with C(A)GCO added. After 8 weeks, the VC content in the blank solution was almost half of that in the sample with C(A)GCO added. This shows that the addition of C(A)GCO can protect VC from oxidation in the solution.

[0061] Example 5 In order to verify the protective effect of C(A)GCO on VC molecules in sugar water containing vitamin C, the method is as follows.

[0062] The following components by mass percentage: sucrose 2%, vitamin C 0.1%, citric acid 0.63%, sodium citrate 0.45%, C(A)GCO 0.3%, potassium sorbate 0.02%, and the balance is drinking water.

[0063] S1. Heat 200 mL of drinking water to boiling for 15 minutes, and cool it for later use; S2. Weigh 2 g sucrose, 0.63 g citric acid, 0.45 g sodium citrate, and 0.02 g potassium sorbate according to the ratio, add them to the sterilized container 1, and dissolve them in 50 mL of water prepared in S1; S3. Weigh 0.1 g of vitamin C and 0.3 g of C(A)GCO according to the ratio and add them to the sterilized container 2, and dissolve them in 50 mL of water prepared in S1; S4. Mix the solutions obtained in S2 and S3, fill, pasteurize (90℃75s), and cool to obtain the finished product. Store in a refrigerator at 4℃.

[0064] Samples were taken weekly and scanned by UV in 1% hydrochloric acid medium to record the changes in the peak value. For comparison purposes, sugar water without C(A)GCO was used as a control. Fig.10 .

[0065] Fig.10 In the experiment, the UV scanning absorption peaks (λ=252nm) of the two sugar water samples showed a downward trend. The UV absorption spectrum peaks of the samples with C(A)GCO added decreased significantly more slowly than those of the sugar water samples without C(A)GCO. After 6 weeks, the decrease in the UV scanning peak value of the samples with C(A)GCO added was about 77.9% of the decrease in the peak value of the reference sample. This shows that the addition of C(A)GCO can also protect VC from oxidation in sugar water solutions.

[0066] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A chitosan oligosaccharide derivative capable of stabilizing vitamin C in aqueous solution, characterized in that: Its molecular structure is as follows: Among them, n=2~20.

2. A method for preparing a chitosan oligosaccharide derivative as claimed in claim 1, characterized in that: The following steps are involved: Step 1) dissolve glycine and sodium carbonate in deionized water, cool to 0°C, add DMF solution of cinnamoyl chloride dropwise, stir for 2-4 h to complete the reaction; acidify with concentrated hydrochloric acid to pH = 1-2, then extract with ethyl acetate, wash, add anhydrous sodium sulfate and dry for 4-6 h; filter to remove the desiccant, and rotary evaporate the filtrate to obtain cinnamoyl glycine as a white solid product; Step 2) dissolving acetylglycine and the product of step 1) in DMF in a certain ratio to obtain a DMF mixed solution, adding triethylamine, cooling to 0°C, adding an equivalent amount of pivaloyl chloride solution dropwise, gradually heating to room temperature and reacting for 2h, filtering to remove white precipitate, and obtaining a mixed anhydride solution; Step 3) Weigh appropriate amounts of chitosan oligosaccharide and sodium carbonate and dissolve them in a certain amount of deionized water, add the mixed anhydride solution obtained in step 2) dropwise, react for 3-4 hours, filter the reaction solution, precipitate and filter with n-propanol, concentrate the centrifuged liquid to 1 / 4, precipitate the filtrate with solvent A, centrifuge and vacuum dry to obtain the chitosan oligosaccharide derivative.

3. The method for preparing the chitosan oligosaccharide derivative according to claim 2, characterized in that: The molar ratio of the raw materials in step 1) is: glycine: sodium carbonate: cinnamoyl chloride = 1: 1.1-1.3: 1.1-1.

4.

4. The method for preparing the chitosan oligosaccharide derivative according to claim 2, characterized in that: The molar ratio of the raw materials in step 2) is: acetylglycine: cinnamoylglycine = 1: 1-3.

5. The method for preparing the chitosan oligosaccharide derivative according to claim 2, characterized in that: The molar ratio of the raw materials is: DMF mixed solution: triethylamine: pivaloyl chloride = 1: 1.0~1.05: 1.0~1.

05.

6. The method for preparing the chitosan oligosaccharide derivative according to claim 2, characterized in that: The molar ratio of the raw materials in step 3) is: mixed anhydride solution: sodium carbonate: chitosan oligosaccharide = 1: 1.0-1.05: 0.9-1.

05.

7. The method for preparing the chitosan oligosaccharide derivative according to claim 2, characterized in that: The solvent A used in step 3) is selected from tetrahydrofuran, ethyl acetate or propyl acetate.

8. Use of the chitosan oligosaccharide derivative as claimed in claim 1 as a vitamin C protective agent in aqueous solution.

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