Preparation method of low-ester mango peel pectin

Abstract

The invention belongs to the technical field of agricultural product processing, and particularly relates to a preparation method and application of low-ester mango peel pectin. The mango peel pectin disclosed by the invention is extracted by adopting an ultrasonic-assisted acid method, is prepared by adopting an alcohol precipitation method, and is degreased by adopting an alkaline method. The low-ester mango peel pectin obtained through the method is high in purity, the esterification degree is low when the esterification degree ranges from 30% to 45%, the molecular weight is large, the pectin gel property and thickening property are good, the low-ester mango peel pectin is an additive of low-calorie food, and the method is short in process time, simple, convenient and easy to operate and has good application and popularization value.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural product processing, and particularly relates to a preparation method of low-ester mango peel pectin and application thereof. Background Art

[0002] Pectin is a natural polysaccharide found primarily in plant cell walls and has attracted attention due to its wide range of applications in the food, pharmaceutical, and cosmetic industries. As a valuable dietary fiber, pectin has a variety of functional properties, including gelling, thickening, stabilizing, and emulsifying abilities, which are of great value in commercial applications. Traditionally, citrus peels and apple pomace have been the main sources for commercial pectin extraction. However, the increasing industrial demand for pectin with multiple functional properties has led to an interest in sustainable and lower-cost alternatives, prompting the exploration of new sources of pectin from other agricultural by-products.

[0003] Mango (Mangifera indica L.) is one of the most widely grown tropical fruits in the world, and a large amount of peel is produced as a by-product during its processing. Mango peel accounts for about 15-20% of the fruit weight and is rich in bioactive compounds such as pectin, making it a promising candidate for pectin extraction.

[0004] According to the degree of methyl esterification DE on the HG domain of pectin, pectin can be divided into high-ester pectin (HMP, DE > 50%) and low-ester pectin (LMP, DE < 50%). Gelation performance is an important indicator for judging the quality of pectin. Based on different degrees of esterification, the gelation conditions required for HMP and LMP are different. HMP gels by lowering the pH value (usually pH 3.0) in the presence of high concentrations of co-solutes (usually 60-65% sucrose). LMP can interact with divalent metal ions to form an "egg box" gel structure, gel in a low-sugar or sugar-free environment, and is very suitable for the production of low-calorie foods. Therefore, compared with HMP, LMP has greater advantages in the application of gel performance and is more in line with consumers' concept of healthy diet.

[0005] At present, there are three common deesterification methods: acid method, alkali method, and enzyme method. The effect of acid-catalyzed deesterification is not significant, and the process is difficult to control; the enzyme method takes too long and is too expensive to be mass-produced industrially. The alkali method has a relatively fast reaction speed and the most significant effect, but the β-elimination reaction accompanying the ester reduction process causes a significant decrease in the molecular weight and viscosity of pectin, and the pectin structure is destroyed, so it cannot form a gel or the gelation degree formed is low. Therefore, the control of the β-elimination reaction is crucial to maintaining the quality of pectin. Summary of the invention

[0006] Technical Solution

[0007] The application value of low-ester pectin is closely related to its gelling properties. The rheological properties and gelling ability of pectin are of great significance to the structural regulation and sensory perception of foods such as jams, jellies and candies to which pectin is added. Therefore, in order to overcome the deficiencies in the prior art, the present invention proposes a method for preparing low-ester mango peel pectin, which can promote the release of mango peel pectin, improve the pectin yield, and reduce the destruction of pectin structure at the same time. The obtained pectin has a higher purity, a larger molecular weight, and good gelling properties and thickening properties. The low-ester pectin of the present invention can be used for the production of low-calorie foods.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A method for preparing low-ester mango peel pectin comprises the following steps: (1) mixing mango peel powder with an acidic solution to obtain a mixed solution, adjusting the pH value of the mixed solution to 2.0-4.0, and performing ultrasonic extraction at 70-90° C. to obtain an extract; (2) subjecting the extract obtained in step (1) to solid-liquid separation, adding ethanol to the filtrate for precipitation, filtering, washing, drying and crushing the precipitate to obtain crude mango peel pectin; (3) re-dissolving the crude mango peel pectin obtained in step (2), adding a protein removal agent, removing the protein, dialyzing to remove impurities, concentrating the dialyzate, adding ethanol to precipitate, filtering, washing, drying, and crushing the precipitate to obtain primary mango peel pectin; (4) The primary mango peel pectin obtained in step (3) is redissolved, an alkaline solution is added at low temperature, the pH value is adjusted to 10.0-11.0, and a deesterification reaction is carried out for 0.5-2 h. An acid is then added to adjust the pH value to 3.0 to terminate the deesterification reaction, and ethanol is added for precipitation. The precipitate is filtered, washed, dried, and crushed to obtain low-calorie, low-ester mango peel pectin.

[0009] In one embodiment, mango peel is blanched to inactivate enzymes, dried, crushed and sieved to obtain mango peel powder.

[0010] In one embodiment, the protein removal agent is one or more of trichloroacetic acid, ammonium sulfate, picric acid, and tannic acid, preferably trichloroacetic acid.

[0011] In one embodiment, the acidic solution in step (1) is one of hydrochloric acid or acetic acid, preferably hydrochloric acid. The solid-liquid mass ratio of the mango peel powder and the hydrochloric acid aqueous solution in step (1) is 1:(10-30); the ultrasonic extraction power is 100-400W, and the extraction time is 1-2 h.

[0012] In one embodiment, the volume concentration of the ethanol solution in step (2), step (3) and step (4) is ≥95%, the volume ratio of the filtrate to the ethanol solution is 1:(1-3), the precipitation time is 12 h, and the number of washings is 1-3 times.

[0013] In one embodiment, the drying in step (2), step (3) and step (4) is forced air drying, the drying temperature is 40-60° C., and the drying time is 1-4 h.

[0014] In one embodiment, the protein removal agent in step (3) is trichloroacetic acid; the mass concentration of the crude mango peel pectin solution after re-dissolution is 1% to 3%, the trichloroacetic acid concentration is 5% to 10%, the deproteinization is repeated 1 to 3 times, the dialysis time is 2 to 4 days, and the dialysate is concentrated to 1 / 2 to 1 / 4 of the original volume.

[0015] In one embodiment, the mass concentration of the primary mango peel pectin solution after redissolution in step (4) is 1%-3%, the low temperature is 10-20°C, the alkaline solution used is NaOH, the acid used is HCl, and the concentration of NaOH and HCl solution is 1 M.

[0016] In one aspect of the present invention, the present invention provides low-ester mango peel pectin prepared by the method of the present invention.

[0017] In the present invention, the prepared primary mango peel pectin has an esterification degree of 80% to 90% and a galacturonic acid content of 65% to 75%.

[0018] In the present invention, the prepared low-ester mango peel pectin has an esterification degree of 30% to 45%, a galacturonic acid content of 70% to 80%, and a molecular weight of 300 to 600 KDa.

[0019] In one aspect of the present invention, the present invention provides the use of the low-ester mango peel pectin of the present invention in preparing food, health food and medicine.

[0020] In one embodiment, the low-ester mango peel pectin prepared by the present invention is used in low-calorie foods. Preferably, the low-calorie foods are low-calorie beverages, yogurt or jam.

[0021] In one embodiment, the low-ester mango peel pectin of the present invention is used to prepare a low-sugar gel. The gel is prepared by the following method: after re-dissolving the low-ester mango peel pectin, adjusting the pH of the pectin solution, adding sucrose, heating and stirring, adding calcium chloride solution, and cooling to obtain a low-sugar gel.

[0022] In one embodiment, the mass concentration of the reconstituted pectin solution is 1% to 3%, the pH is adjusted to 3.0 to 3.3, the mass concentration of sucrose is 20%, the heating and stirring is heating in a constant temperature water bath at 90° C. for 30 min, and after the calcium chloride solution is added, the calcium ion content in the final gel system is 50 to 60 mg / g pectin. Beneficial Effects

[0023] Compared with the prior art, the present invention has the following advantages: (1) The alkaline deesterification of the present invention carries out the ester reduction reaction at a relatively mild temperature, thereby reducing the hydrolysis reaction and the β-elimination reaction as much as possible, and can relatively completely retain the original structure of pectin.

[0024] (2) The alkaline deesterification process of the present invention is simple and easy to operate, economically feasible, and easy to industrialize.

[0025] (3) The low-ester mango peel pectin extracted by the present invention has an esterification degree of 30% to 45%, which belongs to low-ester pectin and is significantly better than that obtained by the acid method.

[0026] (4) The low-sugar gel formed by the low-ester mango peel pectin prepared by the present invention has a higher hardness.

[0027] (5) The low-ester pectin mango peel pectin prepared by the present invention has a good thickening effect after being cross-linked with calcium ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The results are as follows: the extraction rate of mango peel pectin, the content of galacturonic acid and the determination results of the degree of esterification in Examples 1 to 9 of the present invention.

[0029] Figure 2 The infrared spectra of the products obtained in Examples 2 and 10, Comparative Example 1 and Comparative Example 2 of the present invention are shown.

[0030] Figure 3 The present invention provides embodiments 10 to 13, comparative example 2, and comparative example 1, and the yield of low-ester mango peel pectin, the content of galacturonic acid, and the determination results of the degree of esterification.

[0031] Figure 4 These are the results of measuring the pectin molecular weight of Examples 10 to 13, Comparative Example 1, and Comparative Example 2 of the present invention.

[0032] Figure 5 These are the test results of pectin gel strength of Examples 10 to 13 of the present invention, Comparative Example 1, and Comparative Example 2.

[0033] Figure 6 These are the measurement results of the rheological properties of pectin in Examples 10 to 13 of the present invention, Comparative Example 1, and Comparative Example 2.

[0034] Figure 7 These are the rheological property measurement results of pectin after adding calcium to Examples 10 to 13 of the present invention, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific embodiments. Embodiment 1:

[0036] A method for preparing mango peel pectin comprises the following steps: (1) The mango peel is blanched to inactivate enzymes, dried, crushed and sieved to obtain mango peel powder. The mango peel powder is mixed with a hydrochloric acid aqueous solution (1:20) to obtain a mixed solution, the pH value of the mixed solution is adjusted to 2.0, the ultrasonic extraction power is 100 W, and the ultrasonic extraction is performed at 70°C for 2 h to obtain an extract; (2) The extract obtained in step (1) is subjected to solid-liquid separation, and the filtrate is added with 2 times the volume of 95% ethanol for precipitation for 12 hours. The precipitate is filtered, washed repeatedly for 3 times, dried with forced air at 50° C., and crushed to obtain crude mango peel pectin.

[0037] (3) The crude mango peel pectin obtained in step (2) is re-dissolved to prepare a 2% pectin solution, 5% trichloroacetic acid is added, and deproteinization is repeated 3 times. The solution is dialyzed for 3 days to remove impurities. After the dialyzate is concentrated, 2 times the volume of 95% ethanol is added for precipitation. The precipitate is filtered, washed repeatedly 3 times, dried at 50° C., and crushed to obtain primary mango peel pectin. Embodiment 2:

[0038] The ultrasonic extraction power was 200 W, the extraction temperature was 80 °C, and the rest was exactly the same as in Example 1. Embodiment 3:

[0039] The ultrasonic extraction power was 300 W, the extraction temperature was 90 °C, and the rest was exactly the same as in Example 1. Embodiment 4:

[0040] The pH value of the mixed extract was 3.0, the ultrasonic extraction power was 200 W, and the rest was completely consistent with Example 1. Embodiment 5:

[0041] The pH value of the mixed extract was 3.0, the extraction temperature was 80°C, the ultrasonic extraction power was 300 W, and the rest was completely consistent with Example 1. Embodiment 6:

[0042] The pH value of the mixed extract was 3.0, the extraction temperature was 90°C, and the rest was completely consistent with Example 1. Embodiment 7:

[0043] The pH value of the mixed extract was 4.0, the ultrasonic extraction power was 300 W, and the rest was completely consistent with Example 1. Embodiment 8:

[0044] The pH value of the mixed extract was 4.0, the extraction temperature was 80°C, and the rest was completely consistent with Example 1. Embodiment 9:

[0045] The pH value of the mixed extract was 4.0, the extraction temperature was 90°C, the ultrasonic extraction power was 200 W, and the rest was completely consistent with Example 1. Embodiment 10:

[0046] A method for preparing low-ester mango peel pectin comprises the following steps: (1) The mango peel pectin obtained in Example 2 above was dissolved in distilled water to prepare a 1% pectin solution, the pH was adjusted to 10.0 with a 1 M NaOH solution, and the mixture was reacted at 10° C. for 0.5 h to obtain a low-ester mango peel pectin solution; (2) The pH value of the low-ester pectin solution was adjusted to 3.0 with hydrochloric acid, and 2 volumes of 95% ethanol were added for precipitation for 12 h. The precipitate was filtered, washed three times, dried with air at 50°C, and crushed to obtain the low-ester mango peel pectin powder. Embodiment 11:

[0047] The mango peel pectin obtained in Example 2 was dissolved in distilled water to prepare a 2% pectin solution, and the pH was adjusted to 10.5 with 1 M NaOH solution. The reaction temperature was 10° C. and the reaction time was 1 h. The rest was completely consistent with Example 10. Embodiment 12:

[0048] The mango peel pectin obtained in Example 2 was dissolved in distilled water to prepare a 3% pectin solution, and the pH was adjusted to 11.0 with 1 M NaOH solution. The reaction temperature was 20° C. and the reaction time was 1.5 h. The rest was exactly the same as in Example 10. Embodiment 13:

[0049] The mango peel pectin obtained in Example 2 was dissolved in distilled water to prepare a 3% pectin solution. The pH was adjusted to 11.0 with 1 M NaOH solution. The reaction temperature was 20° C. and the reaction time was 2 h. The rest was completely consistent with Example 10. Comparative Example 1:

[0050] The conventional commercial high-ester pectin was compared with the low-calorie and low-ester mango peel pectin prepared by the present invention. Comparative Example 2:

[0051] Low-ester mango peel pectin was prepared by acid method.

[0052] The mango peel pectin obtained in Example 2 was dissolved in distilled water to prepare a 3% pectin solution, and the pH was adjusted to 1.0 with a concentrated nitric acid solution, and the mixture was reacted at a water bath temperature of 60°C for 24 h. The pH of the mixed solution was adjusted to 3.0 with ammonia water, and 2 times the volume of 95% ethanol was added for precipitation for 12 h. The precipitate was filtered, washed repeatedly for 3 times, dried with air at 50°C, and crushed to obtain low-ester mango peel pectin powder. Product property determination:

[0053] The galacturonic acid content in pectin samples was determined by carbazole sulfate colorimetry; the esterification degree of pectin samples was determined by NaOH titration; the functional groups of pectin samples were analyzed by Fourier transform infrared spectroscopy; and the molecular weight of pectin was determined by high performance gel permeation chromatography (HPGPC). Determination of gel strength:

[0054] Preparation method of high-ester pectin gel: Take 1 g of commercial high-ester pectin and dissolve it in 100 mL of distilled water to prepare a 1% pectin solution, adjust the pH to 3.0 with 0.1 M HCl solution, add 60 g of sucrose, heat in a 90°C constant temperature water bath for 30 minutes, and stir magnetically to mix it thoroughly. Replenish the evaporated water with 90°C deionized water, and finally let it cool and stand at room temperature for use.

[0055] Preparation method of low pectin gel: 1 g of the prepared low-ester pectin was dissolved in 100 mL of distilled water to prepare a 1% pectin solution, the pH was adjusted to 3.0 with 0.1 M HCl solution, 20 g of sucrose was added, and the solution was heated in a constant temperature water bath at 90 °C for 30 min. 2+ / low-ester pectin) in a ratio of CaCl2 solution, followed by magnetic stirring to mix thoroughly, and the evaporated water was supplemented with deionized water at 90°C. Finally, it was allowed to cool and stand at room temperature for use.

[0056] The gel sample to be tested is placed on the texture analyzer, with the probe P 0.5R, the speed before measurement 1 mm / s, the speed during measurement 0.2 mm / s, the maximum compression amount 25%, and the maximum stress on the probe during the compression process is the gel strength. Determination of rheological properties:

[0057] Rheological measurements of pectin solutions were performed using a HAAKE™ MARS 60 rotational rheometer. A 2% pectin solution was prepared and approximately 3 mL of the pectin solution was placed on a plate. The rheological measurements were performed at 25 ± 1 °C with a shear rate ranging from 0.01 to 100 s ~1 . Determine the change curve of shear rate and apparent viscosity.

[0058] Prepare a 2% pectin solution at 50 mg / g (Ca 2+ The CaCl2 solution was added in a ratio of 1:1 to 2:1 and then stirred magnetically to mix thoroughly. About 3 mL of the mixed solution was placed on a plate and measured at 25 ± 1 °C with a shear rate ranging from 0.01 to 100 s ~1 . Determine the change curve of shear rate and apparent viscosity.

[0059] Depend on Figure 1 It can be seen that a relatively high pectin yield can be obtained in Examples 1 to 9, among which Example 2 has the highest yield, which indicates that when the ultrasound-assisted acid extraction method with a pH value of 2.0, an ultrasonic extraction power of 200 W, and an extraction temperature of 80°C is used to extract pectin, it can play a synergistic role, promote pectin release, and improve the pectin extraction rate. The mango peel pectin extracted in Examples 1 to 9 has an esterification degree of 80% to 90% and a galacturonic acid content of 65% to 75%, which is a high-ester pectin that meets commercial grade.

[0060] Depend on Figure 2 It can be seen that the comparative example 1, the embodiment 2, and the comparative example 2 have the ~1 The absorption peak at 1630cm ~1 The absorption peak at 1747 cm ~1 The absorption peak at 1630 cm ~1 The absorption peak at is stronger, which is low-ester pectin.

[0061] Depend on Figure 3 It can be seen that the yields of low-ester pectins in Examples 10-13 are all relatively high, among which the low-ester pectin in Example 13 has the highest yield, a lower degree of esterification, and a higher content of galacturonic acid, which indicates that low-ester mango peel pectin of good quality can be obtained by appropriately increasing the concentration of reactants, pH of the reaction system, temperature, and reaction time. In Comparative Example 2, the degree of esterification of mango peel pectin obtained by the acid method is still relatively high.

[0062] Depend on Figure 4 It can be seen that the molecular weight of the low-ester mango peel pectin obtained in Examples 10 to 13 is 300 to 600 KDa, which is not much different from the molecular weight of the commercial high-ester pectin in Comparative Example 1.

[0063] Depend on Figure 5 It can be seen that the strength of the low-ester, low-sugar gels prepared in Examples 10 to 13 is comparable to that of the high-ester gel prepared in Comparative Example 1, and is significantly higher than that of the gel prepared in Comparative Example 2. Therefore, the gel prepared with the low-ester pectin obtained in the present invention has a stronger hardness and lower calories.

[0064] Depend on Figure 6-Figure 7It can be seen that the apparent viscosity of the low-ester mango peel pectin prepared in Examples 10 to 13 is slightly lower than the viscosity of the commercial high-ester pectin in Comparative Example 1, and significantly higher than the viscosity of the mango peel pectin prepared by the acid method in Comparative Example 2. After adding calcium chloride, the apparent viscosity of the low-ester mango peel pectin prepared in Examples 10 to 13 is significantly increased, which is significantly higher than Comparative Examples 1 and 2. Therefore, the low-ester mango peel pectin obtained by the present invention can be used as a thickener in low-calorie foods.

[0065] The above content is a further detailed description of the present invention in combination with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope determined by the claims submitted for the present invention.

Claims

1. A method for preparing low-ester mango peel pectin, characterized in that: The method comprises the following steps: (1) mixing mango peel powder with an acidic solution to obtain a mixed solution, adjusting the pH value of the mixed solution to 2.0-4.0, and performing ultrasonic extraction at 70-90° C. to obtain an extract; (2) subjecting the extract obtained in step (1) to solid-liquid separation, adding ethanol to the filtrate for precipitation, filtering, washing, drying and crushing the precipitate to obtain crude mango peel pectin; (3) re-dissolving the crude mango peel pectin obtained in step (2), adding a protein removal agent, removing the protein, dialyzing to remove impurities, concentrating the dialyzate, adding ethanol to precipitate, filtering, washing, drying, and crushing the precipitate to obtain primary mango peel pectin; (4) The primary mango peel pectin obtained in step (3) is redissolved, an alkaline solution is added at low temperature, the pH value is adjusted to 10.0-11.0, and a deesterification reaction is carried out for 0.5-2 h. An acid is then added to adjust the pH value to 3.0 to terminate the deesterification reaction, and ethanol is added for precipitation. The precipitate is filtered, washed, dried, and crushed to obtain low-calorie, low-ester mango peel pectin.

2. The method according to claim 1, characterized in that The acidic solution in step (1) is hydrochloric acid; the solid-liquid mass ratio of the mango peel powder and the hydrochloric acid aqueous solution in step (1) is 1:(10-30); the ultrasonic extraction power is 100-400 W, and the extraction time is 1-2 h.

3. The method according to claim 1, characterized in that: In the step (1), the mango peel powder is prepared by blanching the mango peel to inactivate enzymes, drying, crushing and sieving.

4. The method according to claim 1, characterized in that The volume concentration of the ethanol solution in step (2), step (3) and step (4) is ≥95%, the volume ratio of the filtrate to the ethanol solution is 1:(1-3), the precipitation time is 12 h, and the number of washings is 1-3 times; the drying in step (2), step (3) and step (4) is forced air drying, the drying temperature is 40-60° C.; and the drying time is 1-4 h.

5. The method according to claim 1, characterized in that The protein removal reagent in step (3) is trichloroacetic acid; the mass concentration of the crude mango peel pectin solution after re-dissolution is 1% to 3%, the trichloroacetic acid concentration is 5% to 10%, the deproteinization is repeated 1 to 3 times, the dialysis time is 2 to 4 days, and the dialysate is concentrated to 1 / 2 to 1 / 4 of the original volume.

6. The method according to claim 1, characterized in that The mass concentration of the primary mango peel pectin solution after redissolution in step (4) is 1% to 3%, the low temperature is 10 to 20° C., the alkaline solution used is NaOH, the acid used is HCl, and the concentration of the NaOH and HCl solutions is 1 M.

7. Low-ester mango peel pectin prepared according to any one of claims 1 to 6.

8. The low-ester mango peel pectin according to claim 7, characterized in that The prepared low-ester mango peel pectin has an esterification degree of 30%-45%, a galacturonic acid content of 70%-80%, and a molecular weight of 300-600 KDa.

9. Use of the low-ester mango peel pectin prepared according to any one of claims 1 to 5 in the preparation of foods, health foods and medicines.

10. The use according to claim 8, characterized in that: The food is low-calorie beverage, yogurt, jam or gel.

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