A kind of preparation method of citrus pectin

Abstract

The present application relates to a method for preparing citrus dietary fiber and high-quality pectin, which is characterized in that it comprises the following steps: cutting citrus peel into slices of uniform size; soaking the peel in deionized water at 100°C for 3-5 minutes; soaking the peel in an ethanol solution for 0.2-0.3 minutes; placing the peel in a blast drying device for drying; crushing the dried peel by a grinder to obtain peel powder; preparing an extraction buffer solution, wherein the pH value of the extraction buffer solution is 4.0-6.0; heating the extraction buffer solution to 45-55°C, adding peel powder and cellulase, ultrasonically treating for 60-80 minutes, and then centrifuging to obtain a supernatant; placing the lower layer liquid in a microwave generator for microwave treatment for 3-5 minutes, and then centrifuging to obtain a supernatant; mixing the above two supernatants, adding 95% ethanol solution to the supernatant, stirring until flocs are precipitated, standing and then filtering, washing the filter residue and placing it in a blast drying device to dry to constant weight to obtain a pectin product.

Description

Technical Field

[0001] The present application relates to the field of food processing technology, and in particular to a method for preparing citrus pectin. Background Art

[0002] Pectin is a type of hydrophilic natural macromolecular polysaccharide polymer. It contains a large amount of pectin polysaccharides in plant cell walls and intercellular layers. It is an important component of cell walls and has the functions of growth, development and plant defense. Pectin as we know it is generally composed of protopectin, pectic acid and pectin. Most of the pectin contained in plant cell walls is protopectin, which is not easily soluble in water; the main component of pectin is D-galacturonic acid polymerized with α-1,4 glycosidic bonds, generally with neutral sugars such as fucose, glucose, galactose, and arabinose. The extraction process of pectin can not only solve the problem of subsequent treatment of fruits after processing, but also increase the economic added value of fruits, while alleviating the current situation of the growing demand for pectin in my country.

[0003] At present, the main method for pectin extraction is acid extraction. The acid extraction method uses hot acidic solution to hydrolyze many complex cross-linked networks on the cell wall, thereby destroying the cell wall, promoting acid diffusion and the release of pectin from the plant matrix; although the acid extraction process is simple, the acid extraction method in the existing technology requires a higher temperature, and the acidic environment combined with the higher temperature causes the pectin structure to be destroyed. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a method for preparing citrus pectin, comprising the following steps:

[0005] Cut the citrus peel into slices of uniform size; the slice area is less than 30cm 2 ;

[0006] Soak the peel in deionized water at 100°C for 3-5 minutes;

[0007] Soak the peel in ethanol solution for 0.2-0.3 min;

[0008] The peel is placed in a blast drying device for drying; the dried peel is crushed by a crusher to obtain peel powder;

[0009] Prepare an extraction buffer solution, wherein the pH value of the extraction buffer solution is 4.0-6.0;

[0010] The extraction buffer was heated to 45-55°C, peel powder and cellulase were added, and the supernatant was collected after ultrasonic treatment for 60-80 minutes;

[0011] The lower layer liquid was placed in a microwave generator for microwave treatment for 3-5 minutes, and then centrifuged to obtain the supernatant;

[0012] The two supernatants were mixed, 95% ethanol solution was added to the supernatant, stirred until flocs were precipitated, allowed to stand and then filtered, the filter residue was washed and placed in a forced air drying device to dry to constant weight, to obtain a pectin product.

[0013] Optionally, soaking the peel in deionized water at 100° C. for 3-5 minutes comprises the following steps:

[0014] Soak the peel in deionized water at 100°C for 0.5-1 min; then let it stand at room temperature for 0.2-0.5 min;

[0015] The above steps are repeated for several times; the total soaking time of the peel in deionized water at 100° C. is 3-5 minutes.

[0016] Optionally, the step of placing the peel in a forced air drying device for drying comprises the following steps:

[0017] The peels were placed in a forced air drying device at 40°C for 1 hour; then the temperature was adjusted to 55°C and maintained for 4 hours; finally, the temperature was adjusted to 70°C and maintained for 15 minutes.

[0018] Optionally, the extraction buffer solution is prepared by mixing a citric acid solution and a disodium hydrogen phosphate solution.

[0019] Optionally, the cellulase is xylanase.

[0020] Optionally, the added amount of the xylanase is 60 U / g.

[0021] Optionally, the solid-liquid ratio of the peel powder to the extraction buffer is 1:60 (g / ml).

[0022] Optionally, the ultrasonic treatment for 60-80 min comprises the following steps:

[0023] Place in ultrasonic environment for 10 minutes; then leave out of ultrasonic environment and let stand for 1 minute;

[0024] Repeat the above steps; the total time in the ultrasonic environment is 60-80 minutes.

[0025] Optionally, the microwave processing power is 750W.

[0026] The method for preparing citrus pectin provided in the examples of the present application has a higher pectin yield compared to the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments that conform to the present application, and are used together with the specification to explain the principles of the present application. In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can also be obtained based on these drawings without paying creative labor. One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute a proportional limitation.

[0028] Figure 1 A flow chart of a method for preparing citrus pectin provided in one embodiment of the present invention.

[0029] Figure 2 These are the experimental results of the effect of passivation time on pectin yield.

[0030] Figure 3 These are the experimental results of the effect of ultrasonic time on pectin yield.

[0031] Figure 4 These are the experimental results of the effect of microwave treatment on pectin yield. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or settings discussed in itself. In addition, the various specific processes and examples of materials provided by the present application, but those of ordinary skill in the art can appreciate the applicability of other processes and / or the use of other materials.

[0034] For ease of description, spatial relative terms may be used herein to describe the relative positional relationship or movement of one element or feature relative to another element or feature as shown in the figure, such as "inside", "outside", "inner side", "outer side", "below", "below", "above", "above", "front", "back", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure undergoes a position flip or a posture change or a motion state change, then these directional indications also change accordingly, for example: an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented as "above other elements or features" or "above other elements or features". Therefore, the example term "below..." may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions) and the spatial relative descriptors used herein are interpreted accordingly.

[0035] The present application provides a method for preparing citrus pectin, comprising the following steps:

[0036] Cut citrus peels into even-sized slices;

[0037] Soak the peel in deionized water at 100°C for 3-5 minutes;

[0038] Soak the peel in ethanol solution for 0.2-0.3 min;

[0039] The peel is placed in a blast drying device for drying; the dried peel is crushed by a crusher to obtain peel powder;

[0040] Prepare an extraction buffer solution, wherein the pH value of the extraction buffer solution is 4.0-6.0;

[0041] The extraction buffer was heated to 45-55°C, peel powder and cellulase were added, and the supernatant was collected after ultrasonic treatment for 60-80 minutes;

[0042] The lower layer liquid was placed in a microwave generator for microwave treatment for 3-5 minutes, and then centrifuged to obtain the supernatant;

[0043] The two supernatants were mixed, 95% ethanol solution was added to the supernatant, stirred until flocs were precipitated, allowed to stand and then filtered, the filter residue was washed and placed in a forced air drying device to dry to constant weight, to obtain a pectin product.

[0044] In an optional embodiment, the slice area is less than 30 cm2.

[0045] In an optional embodiment, the peel is soaked in deionized water at 100°C for 3-5 minutes; including the following steps: soaking the peel in deionized water at 100°C for 0.5-1 minute; then standing it at room temperature for 0.2-0.5 minutes; repeating the above steps for multiple times; the total soaking time of the peel in deionized water at 100°C is 3-5 minutes. Pectinase is a protein that is sensitive to temperature and will be inactivated when heated for a short time. Most types of pectin segments are more heat-resistant than pectinase, but pectin molecules will also decompose when heated for a relatively long time. In the above method, while the pectinase is passivated, the impact on the pectin molecules is minimized.

[0046] In an optional embodiment, the step of placing the peel in a forced air drying device for drying comprises the following steps:

[0047] The peels were placed in a forced air drying device at 40°C for 1 hour; then the temperature was adjusted to 55°C and maintained for 4 hours; finally, the temperature was adjusted to 70°C and maintained for 15 minutes.

[0048] In an optional embodiment, the extraction buffer solution is a mixture of a citric acid solution and a disodium hydrogen phosphate solution.

[0049] In an alternative embodiment, the cellulase is a xylanase.

[0050] In an optional embodiment, the added amount of the xylanase is 60 U / g.

[0051] In an optional embodiment, the solid-liquid ratio of the peel powder to the extraction buffer is 1:60 (g / ml).

[0052] In an optional embodiment, the ultrasonic treatment for 60-80 min comprises the following steps:

[0053] Place in ultrasonic environment for 10 minutes; then leave out of ultrasonic environment and let stand for 1 minute;

[0054] Repeat the above steps; the total time in the ultrasonic environment is 60-80 minutes.

[0055] In an optional embodiment, the microwave treatment power is 750W.

[0056] In an optional embodiment, it includes an ultrasonic device for ultrasound and a container for containing extraction buffer; the ultrasonic device includes a receiving tank; a plurality of ultrasonic generating devices are provided on the side wall of the receiving tank; the side wall of the receiving tank is also provided with a heating device for heating the medium in the receiving tank; it includes a lifting device, a clamping member and a driving member of the lifting device, and the clamping member can clamp the container; the driving member drives the clamping member to move between a first position and a second position in a vertical direction, when the clamping member is in the first position, at least 3 / 4 of the volume of the container is located in the receiving tank, and when the clamping member is in the second position, the container is completely separated from the receiving tank.

[0057] The following provides specific embodiments of the present invention: Example

[0058] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2 slices; soak the peel in deionized water at 100°C for 1 minute; then let it stand at room temperature for 0.3 minutes; repeat the above steps 4 times to complete the passivation of pectinase; then soak the peel in ethanol solution for 0.3 minutes; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 4 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0.1 mol / L disodium hydrogen phosphate solution to prepare an extraction buffer solution, the pH value of the extraction buffer solution is 5; heat the extraction buffer to 50°C, add the peel powder and xylan enzyme, the solid-liquid ratio of the peel powder and the extraction buffer is 1:60 (g / mL), and the added amount of the xylanase is 60U / g; the solution is placed in an ultrasonic device for 10 minutes; then it is separated from the ultrasonic environment and allowed to stand for 1 minute; the above steps are repeated 6 times and then the supernatant is obtained by centrifugation; then the lower layer liquid is placed in a microwave generator for microwave treatment for 5 minutes, the microwave treatment power is 750W, and then the supernatant is obtained by centrifugation; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, allowed to stand and then filtered, the filter residue is washed and placed in a forced air drying device, and placed at 40°C for 1 hour; then the temperature is adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product. Example

[0059] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 1 minute; then let it stand at room temperature for 0.3 minutes; repeat the above steps 5 times to complete the passivation of pectinase; then soak the peel in ethanol solution for 0.3 minutes; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 4 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0.1 mol / L disodium hydrogen phosphate solution to prepare an extraction buffer solution, the pH value of the extraction buffer solution is 5; heat the extraction buffer to 50°C, add the peel powder and xylan enzyme, the solid-liquid ratio of the peel powder and the extraction buffer is 1:60 (g / mL), and the added amount of the xylanase is 60U / g; the solution is placed in an ultrasonic device for 10 minutes; then it is separated from the ultrasonic environment and allowed to stand for 1 minute; the above steps are repeated 7 times and then the supernatant is obtained by centrifugation; then the lower layer liquid is placed in a microwave generator for microwave treatment for 4 minutes, the microwave treatment power is 750W, and then the supernatant is obtained by centrifugation; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, allowed to stand and then filtered, the filter residue is washed and placed in a forced air drying device, and placed at 40°C for 1 hour; then the temperature is adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product. Example

[0060] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 1 minute; then let it stand at room temperature for 0.3 minutes; repeat the above steps 5 times to complete the passivation of pectinase; then soak the peel in ethanol solution for 0.3 minutes; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 4 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0.1 mol / L disodium hydrogen phosphate solution to prepare an extraction buffer solution, the pH value of the extraction buffer solution is 5; heat the extraction buffer to 55°C, add the peel powder and xylan enzyme, the solid-liquid ratio of the peel powder and the extraction buffer is 1:50 (g / mL), and the added amount of the xylanase is 50U / g; the solution is placed in an ultrasonic device for 10 minutes; then it is separated from the ultrasonic environment and allowed to stand for 1 minute; the above steps are repeated 7 times and then the supernatant is obtained by centrifugation; then the lower layer liquid is placed in a microwave generator for microwave treatment for 4 minutes, the microwave treatment power is 650W, and then the supernatant is obtained by centrifugation; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, and then filtered after standing, the filter residue is washed and placed in a forced air drying device, and placed at 40°C for 1 hour; then the temperature is adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product.

[0061] Pectin yield experiment

[0062] The citrus peel and the obtained pectin product were weighed, and the pectin yield p was calculated according to the following formula:

[0063]

[0064] Among them, the m 0 is the weight of the citrus peel; 1 is the weight of pectin (g).

[0065] Single factor experiment

[0066] Effect of inactivation time on pectin yield

[0067] 1.1 Group

[0068] Experimental Group 1 Pectin prepared in the manner described in Example 1 was used.

[0069] Experimental Group 2 Pectin prepared in the manner described in Example 2 was used.

[0070] Experimental Group 3 Pectin prepared by the method described in Example 3.

[0071] Control group 1

[0072] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2 slices; soak the peel in deionized water at 100°C for 4 minutes to passivate the pectinase; then soak the peel in an ethanol solution for 0.3 minutes; then dry the peel in a blast drying oven, specifically, at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 4 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0.1 mol / L disodium hydrogen phosphate solution to prepare an extraction buffer solution, the extraction buffer The pH value of the flushing solution is 5; the extraction buffer is heated to 50°C, and peel powder and xylanase are added, the solid-liquid ratio of the peel powder to the extraction buffer is 1:60 (g / mL), and the amount of xylanase added is 60U / g; the solution is placed in an ultrasonic device for 10 minutes; then it is removed from the ultrasonic environment and allowed to stand for 1 minute; the above steps are repeated 6 times and then centrifuged to obtain the supernatant; then the lower layer liquid is placed in a microwave generator for microwave treatment for 5 minutes, the microwave treatment power is 750W, and then the supernatant is centrifuged; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, allowed to stand and then filtered, the filter residue is washed and placed in a forced air drying device, and placed at 40°C for 1 hour; then the temperature is adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product.

[0073] Control group 2

[0074] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 6 minutes to complete the passivation of pectinase; then soak the peel in an ethanol solution for 0.3 minutes; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 4 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0.1 mol / L disodium hydrogen phosphate solution to prepare an extraction buffer solution, the extraction buffer The pH value of the flushing solution is 5; the extraction buffer is heated to 50°C, and peel powder and xylanase are added, the solid-liquid ratio of the peel powder to the extraction buffer is 1:60 (g / mL), and the amount of xylanase added is 60U / g; the solution is placed in an ultrasonic device for 10 minutes; then it is removed from the ultrasonic environment and allowed to stand for 1 minute; the above steps are repeated 6 times and then centrifuged to obtain the supernatant; then the lower layer liquid is placed in a microwave generator for microwave treatment for 5 minutes, the microwave treatment power is 750W, and then the supernatant is centrifuged; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, allowed to stand and then filtered, the filter residue is washed and placed in a forced air drying device, and placed at 40°C for 1 hour; then the temperature is adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product.

[0075] Control group 3

[0076] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 8 minutes to passivate pectinase; then soak the peel in an ethanol solution for 0.3 minutes; then dry the peel in a blast drying oven, specifically, at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 4 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0.1 mol / L disodium hydrogen phosphate solution to prepare an extraction buffer solution, the extraction buffer The pH value of the flushing solution is 5; the extraction buffer is heated to 50°C, and peel powder and xylanase are added, the solid-liquid ratio of the peel powder to the extraction buffer is 1:60 (g / mL), and the amount of xylanase added is 60U / g; the solution is placed in an ultrasonic device for 10 minutes; then it is removed from the ultrasonic environment and allowed to stand for 1 minute; the above steps are repeated 6 times and then centrifuged to obtain the supernatant; then the lower layer liquid is placed in a microwave generator for microwave treatment for 5 minutes, the microwave treatment power is 750W, and then the supernatant is centrifuged; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, allowed to stand and then filtered, the filter residue is washed and placed in a forced air drying device, and placed at 40°C for 1 hour; then the temperature is adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product.

[0077] 1.2 Experimental Results

[0078] The experimental results are shown in Figure 2 As shown, the yields of experimental groups 1 to 3 are higher than those of control groups 1 to 3. The reason is that pectinase is a protein that is highly sensitive to temperature and can be inactivated by short-term exposure to high temperature. However, under continuous high temperature conditions (control group 1 to control group 3), the molecular chains of pectin will break, affecting the pectin yield.

[0079] Effect of ultrasonic time on pectin yield:

[0080] 2.1 Group

[0081] Experimental Group 1 Pectin prepared in the manner described in Example 1 was used.

[0082] Experimental Group 2 Pectin prepared in the manner described in Example 2 was used.

[0083] Experimental Group 3 Pectin prepared by the method described in Example 3.

[0084] Control group 1

[0085] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 1 min; then let it stand at room temperature for 0.3 min; repeat the above steps 5 times to complete the passivation of pectinase; then soak the peel in ethanol solution for 0.3 min; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 h; then adjust the temperature to 55°C and keep it for 4 h; finally adjust the temperature to 70 degrees Celsius and keep it for 15 min; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0 .1mol / L disodium hydrogen phosphate solution is used to prepare an extraction buffer solution, the pH value of which is 5; the extraction buffer solution is heated to 50°C, and peel powder and xylanase are added, the solid-liquid ratio of the peel powder to the extraction buffer solution is 1:60 (g / mL), and the amount of xylanase added is 60U / g; the solution is placed in an ultrasonic device for 60 minutes; the lower layer liquid is then placed in a microwave generator for microwave treatment for 4 minutes, the microwave treatment power is 750W, and then the supernatant is obtained by centrifugation; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, and filtered after standing. The filter residue is washed and placed in a forced air drying device at 40°C for 1 hour; the temperature is then adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product.

[0086] Control group 2

[0087] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 1 min; then let it stand at room temperature for 0.3 min; repeat the above steps 5 times to complete the passivation of pectinase; then soak the peel in ethanol solution for 0.3 min; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 h; then adjust the temperature to 55°C and keep it for 4 h; finally adjust the temperature to 70 degrees Celsius and keep it for 15 min; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0 .1mol / L disodium hydrogen phosphate solution is used to prepare an extraction buffer solution, the pH value of which is 5; the extraction buffer solution is heated to 50°C, and peel powder and xylanase are added, the solid-liquid ratio of the peel powder to the extraction buffer solution is 1:60 (g / mL), and the amount of xylanase added is 60U / g; the solution is placed in an ultrasonic device for 70 minutes; the lower layer liquid is then placed in a microwave generator for microwave treatment for 4 minutes, the microwave treatment power is 750W, and then the supernatant is obtained by centrifugation; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, and filtered after standing. The filter residue is washed and placed in a forced air drying device at 40°C for 1 hour; the temperature is then adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product.

[0088] Control group 3

[0089] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 1 min; then let it stand at room temperature for 0.3 min; repeat the above steps 5 times to complete the passivation of pectinase; then soak the peel in ethanol solution for 0.3 min; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 h; then adjust the temperature to 55°C and keep it for 4 h; finally adjust the temperature to 70 degrees Celsius and keep it for 15 min; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0 .1mol / L disodium hydrogen phosphate solution is used to prepare an extraction buffer solution, the pH value of which is 5; the extraction buffer solution is heated to 50°C, and peel powder and xylanase are added, the solid-liquid ratio of the peel powder to the extraction buffer solution is 1:60 (g / mL), and the amount of xylanase added is 60U / g; the solution is placed in an ultrasonic device for 80 minutes; the lower layer liquid is then placed in a microwave generator for microwave treatment for 4 minutes, the microwave treatment power is 750W, and then the supernatant is obtained by centrifugation; the above two supernatants are mixed, 95% ethanol solution is added to the supernatant, stirred until flocs are precipitated, and the residue is filtered after standing. The residue is washed and placed in a forced air drying device at 40°C for 1 hour; the temperature is then adjusted to 55°C and maintained for 2 hours; finally, the temperature is adjusted to 70 degrees Celsius and maintained for 15 minutes to obtain a pectin product.

[0090] 2.2 Experimental Results

[0091] The experimental results are as follows Figure 3 As shown in the figure, the experimental results show that the pectin yield of experimental groups 1 to 3 exceeds that of control groups 1 to 3. This is because the samples are in an ultrasonic environment for a long time, and the heat accumulation causes the pectin molecular chain to break. Compared with control groups 1 to 3, as time goes by, the pectin molecules decompose more, thereby reducing the pectin yield.

[0092] Effect of microwave treatment on pectin yield

[0093] 3.1 Group

[0094] Experimental Group 1 Pectin prepared in the manner described in Example 1 was used.

[0095] Experimental Group 2 Pectin prepared in the manner described in Example 2 was used.

[0096] Experimental Group 3 Pectin prepared by the method described in Example 3.

[0097] Control group 1

[0098] Take fresh citrus peels and cut them into 25cm pieces. 2 -30cm 2slices; soak the peel in deionized water at 100°C for 4 minutes to complete the passivation of pectinase; then soak the peel in ethanol solution for 0.3 minutes; then place the peel in a blast drying oven to dry, specifically, at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 4 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes; then place the dried peel in a grinder to crush it to obtain peel powder; use 0.1 mol / L citric acid solution and 0.1 mol / L disodium hydrogen phosphate solution to prepare an extraction buffer solution, the pH value of which is 5; heat the extraction buffer to 50°C, add peel powder and xylanase, the solid-liquid ratio of the peel powder to the extraction buffer is 1:60 (g / mL), and the amount of xylanase added is 60U / g; place the solution in an ultrasonic device for 10 minutes; then leave it out of the ultrasonic environment and let it stand for 1 minute; repeat the above steps 6 times and centrifuge to obtain the supernatant; then centrifuge to obtain the supernatant; add 95 % ethanol solution, stir until flocs are precipitated, let it stand and then filter it with suction, wash the filter residue and place it in a forced air drying equipment at 40°C for 1 hour; then adjust the temperature to 55°C and keep it for 2 hours; finally adjust the temperature to 70 degrees Celsius and keep it for 15 minutes to obtain the pectin product.

[0099] 3.1 Experimental Results

[0100] The experimental results are as follows Figure 4 As shown in the figure, the experimental results show that the pectin yield of control group 1 is lower than that of experimental groups 1 to 3. The reason is that the use of microwave secondary extraction can make the extraction more complete. In addition, secondary extraction does not need to consider the effect of temperature on pectin to a certain extent, thus avoiding the disadvantages of microwave extraction.

[0101] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing citrus pectin, characterized in that: The following steps are involved: Cut citrus peels into even-sized slices; Soak the peel in deionized water at 100°C for 3-5 minutes; Soak the peel in ethanol solution for 0.2-0.3 min; The peel is placed in a blast drying device for drying; the dried peel is crushed by a crusher to obtain peel powder; Prepare an extraction buffer, wherein the pH value of the extraction buffer is 4.0-6.0; The extraction buffer was heated to 45-55°C, peel powder and xylanase were added, and the supernatant was collected after ultrasonic treatment for 60-80 minutes; The lower layer liquid obtained by centrifugation is placed in a microwave generator for microwave treatment for 3-5 minutes, and then centrifuged to obtain the supernatant; The two supernatants are mixed, 95% ethanol solution is added to the mixed supernatant, stirred until flocs are precipitated, filtered after standing, the filter residue is washed and placed in a forced air drying device to dry to constant weight, and a pectin product is obtained; the peel is soaked in deionized water at 100°C for 3-5 minutes; comprising the following steps: Soak the peel in deionized water at 100°C for 0.5-1 min; then let it stand at room temperature for 0.2-0.5 min; Repeat the above steps for several times; the total soaking time of the peel in deionized water at 100° C. is 3-5 minutes; The ultrasonic treatment for 60-80 min comprises the following steps: Place in ultrasonic environment for 10 minutes; then leave out of ultrasonic environment and let stand for 1 minute; Repeat the above steps; the total time in the ultrasonic environment is 60-80 minutes.

2. The preparation method according to claim 1, characterized in that: The step of placing the peel in a blast drying device for drying comprises the following steps: The peels were placed in a forced air drying device at 40°C for 1 hour; then the temperature was adjusted to 55°C and maintained for 4 hours; finally, the temperature was adjusted to 70°C and maintained for 15 minutes.

3. The preparation method according to claim 1, characterized in that: The extraction buffer is prepared by mixing a citric acid solution and a disodium hydrogen phosphate solution.

4. The preparation method according to claim 1, characterized in that: The added amount of the xylanase is 60 U / g.

5. The preparation method according to claim 1, characterized in that: The solid-liquid ratio of the peel powder to the extraction buffer is 1g:60ml.

6. The preparation method according to claim 1, characterized in that: The microwave processing power was 750W.

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