Method for stabilizing anthocyanin through ultrahigh pressure treatment of blueberry pectin and application

Abstract

The invention provides a method for stabilizing anthocyanin through ultrahigh pressure treatment of blueberry pectin, and belongs to the technical field of food processing. The method comprises the following steps: treating blueberry pectin by using ultrahigh pressure, mixing the treated blueberry pectin with an anthocyanin solution, and treating the mixed solution by using ultrahigh pressure again. The interaction of the blueberry pectin treated by the ultrahigh pressure and the anthocyanin is a novel method for stabilizing the anthocyanin, the structure of the blueberry pectin is changed by the ultrahigh pressure treatment, and the blueberry pectin and the anthocyanin are interacted to form a blueberry pectin-anthocyanin compound, so that the stability of the anthocyanin is improved. Compared with general pectin (such as citrus peel pectin), the blueberry pectin-anthocyanin compound produced by the invention can stabilize the color and luster of blueberry juice and improve the quality of the blueberry juice.

Description

Technical Field

[0001] The invention belongs to the field of food processing, and particularly relates to a method for ultra-high pressure treatment of blueberry pectin to stabilize anthocyanins and an application thereof. Background Art

[0002] Anthocyanins are an important type of natural water-soluble pigments, widely found in plants such as blueberries, grapes, and purple cabbage. Due to their excellent antioxidant activity and coloring ability, they are widely used in the food industry to modify the color of beverages, jams, dairy products, and other products. However, the chemical structure of anthocyanins contains unstable glycosidic bonds and phenolic hydroxyl groups, which are easily affected by factors such as temperature, light, pH value, and metal ions, causing degradation or structural changes, resulting in color fading and quality degradation during food processing and storage. This defect severely limits its long-term application in food, especially in heat-processed products.

[0003] At present, common methods to improve the stability of anthocyanins include adding stabilizers (such as polysaccharides, proteins), microencapsulation technology, chemical modification (such as acylation, methylation), and forming complexes with other macromolecules. However, these methods have certain limitations. Pectin, as a natural polysaccharide, has the potential to bind to anthocyanins due to the galacturonic acid and neutral sugar side chains in its molecular structure. In particular, RG-I type pectin, with its unique rhamnogalacturonic acid polysaccharide backbone and complex neutral sugar side chain structure, may form stable complexes with anthocyanins through hydrophobic interactions, hydrogen bonds or electrostatic interactions.

[0004] However, in the prior art, the research on pectin structure modification is mostly focused on acid / alkali treatment, enzymatic modification or heat treatment, which may destroy the functional groups of pectin or cause excessive degradation of the molecular chain, but reduce its binding ability with anthocyanins. For example, patent CN113647623A discloses a method of using ultra-high pressure treatment to blend RG-I pectin and anthocyanins, which improves the stability of anthocyanins by non-covalent bonding. However, this method has the following limitations: it uses conventional RG-I pectin (such as citrus pectin), which is not optimized for the blueberry system. The molecular structure of blueberry anthocyanins is different from that of the citrus system, and it is difficult for universal pectin to fully expose the binding site, resulting in low composite efficiency; a single ultra-high pressure treatment can only partially enhance the interaction between pectin and anthocyanins, and the pectin pretreatment process is not optimized, and the thermal stability and antioxidant properties of anthocyanins in the composite are still not ideal. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for stabilizing anthocyanins by ultrahigh pressure treatment of blueberry pectin, thereby improving the stability of anthocyanins and helping to improve the problem of easy deterioration of the color of blueberry juice.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A method for ultra-high pressure treatment of blueberry pectin to stabilize anthocyanins comprises the following steps: treating blueberry pectin with ultra-high pressure, mixing the treated blueberry pectin with anthocyanin solution, and treating the mixed solution with ultra-high pressure again.

[0008] Preferably, the pressure of the first ultra-high pressure treatment is 200-600 MPa, and the time is 5-25 min; the pressure of the second ultra-high pressure treatment is 400-600 MPa, and the time is 5-20 min.

[0009] Preferably, the concentration of the blueberry pectin is 0.1-0.5 mg / mL, and the concentration of the anthocyanin solution is 0.1-0.2 mg / mL.

[0010] More preferably, the mass ratio of blueberry pectin to anthocyanin is 2:1.

[0011] Preferably, the blueberry pectin is blueberry RG-I type pectin.

[0012] More preferably, the blueberry pectin is prepared as follows: blueberry freeze-dried powder is taken, extracted with citric acid in a water bath, cooled and centrifuged to obtain a supernatant; the supernatant is precipitated with alcohol, and the precipitate is collected; the precipitate is redissolved in water, centrifuged to remove impurities, dialyzed and purified using a dialysis bag with a cutoff of 7 kDa, and freeze-dried to obtain a crude polysaccharide; the crude polysaccharide is subjected to Cellulose DE-52 ion exchange chromatography, and gradient eluted with pure water and 0.1-0.5 mol / L NaCl solution in sequence, and the target elution peak is collected; the eluate is dialyzed and desalted using a dialysis bag with a cutoff of 500 Da, and freeze-dried to obtain blueberry RG-I type pectin.

[0013] Preferably, the anthocyanin is cyanidin-3-glucoside.

[0014] Preferably, the method further comprises centrifuging the mixture of blueberry pectin and anthocyanin solution and freeze-drying the precipitate to prepare the blueberry pectin-anthocyanin complex.

[0015] The present invention also provides a blueberry pectin-anthocyanin complex prepared by the method.

[0016] The present invention also provides the method and application of the prepared blueberry pectin-anthocyanin complex in food processing.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention regulates the molecular conformation of blueberry pectin through ultra-high pressure physical modification technology, directly utilizes the natural interaction between pectin and anthocyanins to form a complex, and does not require the introduction of chemical stabilizers or chemical modification; ultra-high pressure treatment can accurately regulate the degree of modification of pectin, avoid excessive degradation of molecular chains or destruction of functional groups caused by traditional acid / alkali treatment or enzymatic modification, ensure that the active sites of pectin are fully exposed, and enhance its hydrogen bonding, hydrophobicity and electrostatic synergy with anthocyanins; the present invention effectively solves the problem of color deterioration caused by anthocyanin degradation during processing and storage of heat-sensitive products such as blueberry juice.

[0019] The blueberry pectin-anthocyanin complex prepared by the present invention not only has excellent stability, but can also be directly applied to food systems such as beverages and jams as a natural pigment, and has thickening, stabilizing and antioxidant functions, thus simplifying the formulation design process and reducing production costs. By inhibiting the oxidation and degradation of anthocyanins, the application of the complex can significantly delay the color fading and quality degradation of food, and is particularly suitable for deep-processed blueberry products that require long-term storage or high-temperature sterilization, and has significant industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Thermal stability of blueberry pectin-anthocyanin complexes formed under different ultrahigh pressure treatment conditions. DETAILED DESCRIPTION

[0021] The invention provides a method for stabilizing anthocyanins by ultrahigh pressure treatment of blueberry pectin, comprising the following steps: treating blueberry pectin by ultrahigh pressure, mixing the treated blueberry pectin with anthocyanin solution, and treating the mixed solution by ultrahigh pressure again.

[0022] The first ultra-high pressure treatment of the present invention promotes the three-dimensional network structure of blueberry pectin to unfold, exposing the originally wrapped hydrophobic region and charged group, enhancing its binding ability with anthocyanin molecules, and the exposed hydrophobic region of pectin combines with the aromatic ring of anthocyanin through hydrophobic action, reducing the contact between anthocyanin and water molecules and inhibiting hydrolysis. At the same time, ultra-high pressure treatment can break the hydrogen bonds within the pectin molecules, increase the flexibility and accessibility of the molecular chain, and make it easier to form multi-point binding with groups such as phenolic hydroxyl groups and glycosidic bonds of anthocyanin. Under acidic conditions (such as juice system), the negatively charged surface of pectin can adsorb positively charged anthocyanins through electrostatic attraction. The formation of the blueberry pectin-anthocyanin complex causes the anthocyanin molecules to be wrapped in the network structure of pectin, physically blocking the degradation-promoting factors such as oxygen and metal ions, and reducing the oxidation and chelation reaction rates. The second ultrahigh pressure treatment promoted the penetration of anthocyanins into the interior of blueberry pectin, further enhancing the hydrophobic interaction, hydrogen bonding and electrostatic interaction between the initially combined blueberry pectin and anthocyanins, which helped to generate a more stable blueberry pectin-anthocyanin complex.

[0023] In the present invention, the pressure of the first ultra-high pressure treatment is preferably 200-600 MPa, more preferably 400 MPa; the time of the first ultra-high pressure treatment is preferably 5-25 min, more preferably 10 min. The pressure of the second ultra-high pressure treatment is preferably 400-600 MPa, more preferably 500 MPa; the time of the second ultra-high pressure treatment is preferably 5-20 min, more preferably 10 min.

[0024] In the present invention, the concentration of blueberry pectin is preferably 0.1-0.5 mg / mL, more preferably 0.4 mg / mL; the concentration of anthocyanin solution is preferably 0.1-0.2 mg / mL, more preferably 0.2 mg / mL. More preferably, the mass ratio of blueberry pectin to anthocyanin is 2:1. As an implementable method, a 0.4 mg / mL blueberry pectin solution is prepared, and after ultrahigh pressure treatment, it is mixed with an equal volume of a 0.2 mg / mL anthocyanin solution.

[0025] In the present invention, the preferred blueberry pectin is blueberry RG-I type pectin; the further preferred blueberry pectin preparation method is as follows: take blueberry freeze-dried powder, extract with citric acid in a water bath, cool and centrifuge to obtain a supernatant; precipitate the supernatant with alcohol, collect the precipitate; redissolve the precipitate in water, centrifuge to remove impurities, dialysis and purification with a dialysis bag with a cutoff of 7kDa, freeze-dry to obtain a crude polysaccharide; the crude polysaccharide is subjected to Cellulose DE-52 ion exchange chromatography, gradient eluted with pure water and 0.1-0.5mol / LNaCl solution in turn, and the target elution peak is collected; the eluate is dialyzed and desalted with a dialysis bag with a cutoff of 500Da, and freeze-dried to obtain blueberry RG-I type pectin. A more preferred preparation method is as follows:

[0026] (1) Use a wall-breaking machine to crush fresh blueberries into a paste, and freeze-dry them into blueberry freeze-dried powder for later use.

[0027] (2) Extraction with citric acid. Weigh 10 g of blueberry freeze-dried powder and add it to 150 mL of 5% (w / v) citric acid solution at a solid-liquid ratio of 1:15. Adjust the mixture system to pH = 2.0 with 0.1 mol / L NaCl at room temperature. Place the above system in a 500 mL beaker, extract in a water bath at 80°C for 2 h (magnetic stirring), cool, and centrifuge at 6000 rpm for 10 min. Take the supernatant.

[0028] (3) The supernatant was adjusted to pH 6.5 with 1 mol / L NaCl solution, and 4 volumes of anhydrous ethanol (80%, v / v) were added. The mixture was stirred for 10 min and allowed to precipitate overnight at room temperature. The mixture was centrifuged at 6000 rpm for 10 min and the precipitate was washed twice with ethanol until the ethanol was colorless.

[0029] (4) The precipitate was redissolved in water and centrifuged again to remove insoluble impurities. The supernatant was retained and dialyzed for 48 h using a dialysis bag with a cutoff of 7 kDa, during which the water was continuously changed. The blueberry crude polysaccharide was obtained by freeze-drying.

[0030] (5) Take 200g of Cellulose DE-52 ion exchange cellulose, swell and balance to room temperature, and then load it into the column. Use 2mol / L NaCl solution and 0.1mol / L acetic acid solution for balance, and then use pure water for balance for more than 5 column volumes. Take another 50g of Cellulose DE-52 ion exchange cellulose, swell and balance it according to the same operation, and then reduce the pressure and filter it to make it basically dry. Weigh 500mg of decolorized and deproteinized blueberry crude polysaccharide and dissolve it in 30mL pure water. Slowly add the basically dried Cellulose DE-52 ion exchange cellulose and mix it thoroughly to make the crude polysaccharide solution adsorbed on the cellulose. Then add an appropriate amount of pure water to make the mixed filler evenly stirred for column loading. Slowly add cellulose filler mixed with crude polysaccharide sample to the balanced cellulose column, let stand for stratification, open the column, elute 1 column volume with pure water, 0.1, 0.2, 0.3, 0.4, 0.5 mol / L NaCl solution, control the flow rate to 1 mL / min, and collect the eluent in centrifuge tubes, 8 mL per tube. Detect the total sugar content of the eluent by phenol-sulfuric acid method, and draw the elution curve. Collect the pectin components BP1, BP2, and BP3. Transfer the pectin components BP1-BP3 to a dialysis bag with a molecular weight cutoff of 500 Da, dialyze four times with more than 100 times pure water to fully remove NaCl, and freeze-dry again to obtain blueberry RG-I type pectin.

[0031] The external standard method was used for quantitative analysis. The standard curve was drawn by using different concentrations of each monosaccharide standard sample to quantitatively analyze the monosaccharide composition of BP1, BP2 and BP3, as shown in Table 1. As shown in Table 1, the RG-I fructose content of BP1, BP2 and BP3 was 93.50%, 67.35% and 83.09%, respectively (refer to the method proposed by Rahmani et al.). Compared with general pectin (such as citrus peel RG-I pectin), it better meets the requirements of ultra-high pressure treatment for stabilizing anthocyanins.

[0032] Table 1 Monosaccharide composition results of BP1, BP2 and BP3

[0033]

[0034] In the present invention, the anthocyanin is preferably cyanidin-3-glucoside.

[0035] In the present invention, it is preferred that the mixture of blueberry pectin and anthocyanin solution is centrifuged and the precipitate is freeze-dried to prepare a blueberry pectin-anthocyanin complex; more preferably, centrifugation at 4500-6000 rpm for 10 min; and more preferably, freeze-drying for 48 h.

[0036] The present invention also provides a blueberry pectin-anthocyanin complex prepared by the method.

[0037] The present invention also provides the use of the above method and the obtained blueberry pectin-anthocyanin complex in food processing, preferably in the processing and / or storage of anthocyanin-rich foods.

[0038] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0039] Example 1

[0040] A method for ultra-high pressure treatment of blueberry pectin to stabilize anthocyanins, comprising the following steps:

[0041] Take 5 mL of blueberry pectin solution (0.4 mg / mL RG-I type pectin), treat it with ultra high pressure 200 MPa for 10 minutes, mix it with 5 mL of anthocyanin solution (0.2 mg / mL cyanidin-3-glucoside), and treat it with ultra high pressure 500 MPa again for 10 minutes. Centrifuge the mixture at 4500 rpm for 10 minutes, and freeze-dry the precipitate for 48 hours to obtain the blueberry pectin-anthocyanin complex.

[0042] Example 2

[0043] The pressure of the first ultrahigh pressure treatment in Example 1 was increased to 300 MPa.

[0044] Example 3

[0045] The first ultrahigh pressure treatment pressure of Example 1 was increased to 400 MPa.

[0046] Example 4

[0047] The pressure of the first ultrahigh pressure treatment in Example 1 was increased to 500 MPa.

[0048] Example 5

[0049] The pressure of the first ultrahigh pressure treatment in Example 1 was increased to 600 MPa.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that 5 mL of water was added to 5 mL of anthocyanin solution to serve as an anthocyanin control group.

[0052] Comparative Example 2

[0053] The difference from Example 1 is that 5 mL of blueberry pectin solution that was not treated with ultrahigh pressure was added to 5 mL of anthocyanin solution to form an untreated group.

[0054] The samples of Examples 1-5, the anthocyanin control group and the untreated group were placed in a water bath at 90° C. for 120 min. The absorbance of the solution at 520 nm was measured using a UV-visible spectrophotometer at 0, 20, 40, 60, 80, 100 and 120 min.

[0055] Retention rate = A1 / A0;

[0056] A0 is the absorbance value at 0 min, and A1 is the absorbance value after water bath.

[0057] The test results are as follows Figure 1 As shown. Figure 1 It can be seen that as the pressure of ultra-high pressure treatment of blueberry pectin increases, the stability of anthocyanins after mixing increases. However, after exceeding 400 MPa, the stability of anthocyanins in the composite decreases. The thermal stability of the blueberry pectin-anthocyanin composite after 400 MPa and 10 min treatment is the highest. When blueberry pectin that has not been treated with ultra-high pressure is directly mixed with anthocyanins, after a certain period of time, the stability of anthocyanins is lower than that of Examples 1-5.

[0058] Example 6

[0059] A method for ultra-high pressure treatment of blueberry pectin to stabilize anthocyanins, comprising the following steps:

[0060] Take 5 mL of blueberry pectin solution (0.2 mg / mL RG-I type pectin), treat it with ultra high pressure 600 MPa for 5 minutes, mix it with 5 mL of anthocyanin solution (0.1 mg / mL cyanidin-3-glucoside), and treat it with ultra high pressure 600 MPa for 5 minutes again. Centrifuge the mixture at 6000 rpm for 10 minutes, and freeze-dry the precipitate for 48 hours to obtain the blueberry pectin-anthocyanin complex.

[0061] Example 7

[0062] A method for ultra-high pressure treatment of blueberry pectin to stabilize anthocyanins, comprising the following steps:

[0063] Take 5 mL of blueberry pectin solution (0.5 mg / mL RG-I type pectin), treat it at ultrahigh pressure of 200 MPa for 25 minutes, mix it with 5 mL of anthocyanin solution (0.2 mg / mL cyanidin-3-glucoside), and treat it at ultrahigh pressure of 400 MPa for 20 minutes. Centrifuge the mixture at 5000 rpm for 10 minutes, and freeze-dry the precipitate for 48 hours to obtain the blueberry pectin-anthocyanin complex.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for ultra-high pressure treatment of blueberry pectin to stabilize anthocyanins, characterized in that: The following steps are involved: The blueberry pectin is treated by ultra-high pressure, the treated blueberry pectin is mixed with anthocyanin solution, and the mixture is treated by ultra-high pressure again.

2. The method according to claim 1, characterized in that The pressure of the first ultra-high pressure treatment is 200-600 MPa, and the time is 5-25 min; the pressure of the second ultra-high pressure treatment is 400-600 MPa, and the time is 5-20 min.

3. The method according to claim 1, characterized in that The concentration of the blueberry pectin is 0.1-0.5 mg / mL, and the concentration of the anthocyanin solution is 0.1-0.2 mg / mL.

4. The method according to claim 3, characterized in that The mixing mass ratio of the blueberry pectin to anthocyanin is 2:

1.

5. The method according to claim 1, characterized in that The blueberry pectin is blueberry RG-I type pectin.

6. The method according to claim 1 or 5, characterized in that: The preparation method of the blueberry pectin is as follows: taking blueberry freeze-dried powder, extracting it in a citric acid water bath, cooling it and centrifuging it to obtain a supernatant; subjecting the supernatant to alcohol precipitation, collecting the precipitate; redissolving the precipitate in water, centrifuging it to remove impurities, dialysis purification using a dialysis bag with a cutoff of 7 kDa, and freeze-drying it to obtain a crude polysaccharide; subjecting the crude polysaccharide to Cellulose DE-52 ion exchange chromatography, gradient eluting it with pure water and a 0.1-0.5 mol / L NaCl solution in sequence, and collecting the target elution peak; subjecting the eluate to dialysis desalting using a dialysis bag with a cutoff of 500 Da, and freeze-drying it to obtain blueberry RG-I type pectin.

7. The method according to claim 1, characterized in that The anthocyanin is cyanidin-3-glucoside.

8. The method according to claim 1, characterized in that The method also includes centrifuging the mixture of the blueberry pectin and the anthocyanin solution and freeze-drying the precipitate to prepare a blueberry pectin-anthocyanin complex.

9. The blueberry pectin-anthocyanin complex prepared by the method according to claim 8.

10. Use of the method according to any one of claims 1 to 8 or the blueberry pectin-anthocyanin complex according to claim 9 in food processing.

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