Sunflower low-ester pectin, coating adhesion liquid and preparation method and application of sunflower low-ester pectin and coating adhesion liquid

Abstract

The invention belongs to the technical field of food processing, and relates to sunflower low-ester pectin, coating adhesion liquid as well as a preparation method and application of the sunflower low-ester pectin. The technical problem that in the prior art, the extraction rate of sunflower low-methoxyl pectin is low is solved. The invention provides a preparation method of sunflower low-ester pectin. Comprising the following steps: taking sunflower discs, and performing microwave treatment and freeze drying to obtain pretreated sunflower discs; after ultrasonic treatment in ethanol, soaking and filtering to obtain a sunflower disc filter cake; adding mixed enzyme, and performing enzymolysis, wherein the mixed enzyme accounts for 1-2% of the mass of the pretreated sunflower plate; the mixed enzyme comprises cellulase and pectinase, and the mass ratio of the cellulase to the pectinase is (2-4): 1; and filtering, collecting filtrate, centrifuging, adding an ethanol solution into the obtained supernate, carrying out alcohol precipitation treatment, standing, and centrifuging to obtain the sunflower low-ester pectin. In order to solve the technical problems of weak adhesive force and low moisture resistance of an adhesive in the food field in the prior art, the invention provides a preparation method and application of the coating adhesive liquid.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and specifically relates to sunflower low-ester pectin, a coating adhesion liquid, and a preparation method and application thereof. Background Art

[0002] The coating technology, as a key process widely used in the food industry, is usually used for fine flavoring of foods such as melon seeds, peanuts, and other various nut foods. The core of this technology lies in the ability to evenly cover a selected flavoring on the surface of the food, significantly enhancing the taste and flavor of the food. The performance of the adhesive is crucial for the uniformity and stability of the coating layer, the shelf life and shelf performance, and the overall quality of the final product and the satisfaction of consumers.

[0003] Currently, the commonly used coating adhesives each have their own characteristics, but all have certain limitations. Starch-based adhesives represented by corn starch and potato starch are widely used in industrial-scale production due to their considerable resource reserves and economy. However, the poor stability of these adhesives limits their application under humid conditions. Modified starches, such as acetylated starch and oxidized starch, enhance their adhesion and water resistance through chemical or physical modification means, but the chemical substances involved in the modification process have raised concerns about food safety. Syrup-based adhesives, such as glucose syrup and malt syrup, are favored for their excellent adhesion and transparency. However, their high sugar content and easy hygroscopicity are disadvantages. Although the existing adhesives mentioned above can meet the requirements of the coating technology to a certain extent, there are still problems such as moisture absorption, high cost, and potential food safety hazards.

[0004] The publication number of the Chinese invention patent application is CN108902868A, the application date is June 29, 2018, and the invention title is "A method for preparing coated nut kernels, coated nut kernels, and coating liquid". It discloses a method for preparing coated nut kernels, which first prepares a coating liquid and then coats and bakes the nut kernels to obtain coated nut kernels. Among them, the coating liquid is obtained by mixing water, sugar, flour, and yeast and fermenting. The coating liquid in this solution is the adhesive, and the fermentation process may cause uneven adhesion of the coating liquid, affecting the uniformity and stability of the coating layer; the sugar solution will absorb moisture after drying, affecting the shelf life of the product. Therefore, finding an adhesive with strong moisture barrier and antioxidant properties, which is safe and environmentally friendly, has become an important topic in the food industry.

[0005] In recent years, low-ester pectin has been widely used in the food industry due to its excellent gelling properties. Most of the low-ester pectin on the market is prepared by chemically treating high-ester pectin. The content of low-ester pectin in sunflower flower disks is very rich. Developing and utilizing the natural low-ester pectin in sunflower flower disks can not only reduce resource waste and environmental pollution, but also enrich the types of pectin and improve the quality. However, there are many problems in the current extraction process of sunflower low-ester pectin: (1) Low extraction efficiency: In traditional extraction methods, sunflower disks need to be dried, which increases energy consumption and costs; (2) Poor product quality: The extracted pectin has poor color and usually needs to be decolorized, resulting in partial degradation of some pectin and affecting product quality; (3) Environmental problems: The acid extraction method generates a large amount of waste liquid, with high treatment costs and a burden on the environment; (4) Complex process: The existing extraction processes are complex and difficult to industrialize.

[0006] In the prior art, the extraction method of sunflower low-ester pectin is mainly acid extraction followed by ethanol precipitation. For example, the Chinese invention patent application publication number is CN109553699A, the application date is January 7, 2019, and the invention name is "A method for extracting low-ester pectin from fresh sunflower trays and stems using acid", which discloses the following extraction steps: Using sunflower green disks or green stems as raw materials, inactivate enzymes in a constant temperature water bath at ≥95°C for 20 min to 30 min, filter, and discard the enzyme-inactivated solution; in the precipitate, add distilled water at a material-liquid ratio of 1:4 to 10, add solid oxalic acid, control the oxalic acid concentration in the reaction system to be 0.2% to 0.6% for extraction, the extraction temperature is 75°C to 80°C, and the extraction time is 20 min to 35 min; after the crude extraction is completed, add hydrochloric acid, the amount of hydrochloric acid added is 6 mL to 12 mL hydrochloric acid per 100 g of raw material, heat up to 85°C to 95°C, and extract for 25 min to 40 min; then filter and collect the filtrate at 75°C to 95°C; the filtrate is concentrated by vacuum distillation at 40°C to 50°C to 0.5 to 0.7 times the original solution volume to obtain a concentrated extraction solution; the concentrated extraction solution is subjected to alcohol precipitation with ethanol, and after standing, filter to obtain white flocculent pectin, dehydrate, sieve, and vacuum dry and pulverize to obtain pectin powder. The use of oxalic acid and hydrochloric acid in this method will cause partial degradation of pectin during the extraction process, affecting the extraction efficiency; at the same time, it will generate a large amount of acidic waste liquid, which is not friendly to the environment, and the treatment cost of the acidic waste liquid is high, increasing the economic burden of the entire extraction process; this process requires multiple steps, with complex operations and high equipment requirements. Therefore, there is an urgent need for a preparation method of sunflower low-ester pectin with high extraction rate, simple process and environmental protection. Summary of the Invention

[0007] 1. Problems to be Solved

[0008] Aiming at the technical problem of low extraction rate of sunflower low-ester pectin in the prior art, the present application provides a preparation method of sunflower low-ester pectin with a high yield. At the same time, sunflower low-ester pectin obtained by this preparation method is provided.

[0009] Meanwhile, aiming at the technical problems of the adhesives in the food industry field in the prior art, such as limitations, weak adhesion force, and low moisture barrier performance, the present application provides a preparation method of a coating adhesion liquid. By adding sunflower low-ester pectin, the obtained coating adhesion liquid has strong adhesion force and good moisture barrier performance.

[0010] The present application also provides the use of sunflower low-ester pectin, the coating adhesion liquid or the preparation method of the coating adhesion liquid in the preparation of coated melon seeds or coated nut kernels.

[0011] 2. Technical solution

[0012] In order to achieve the above object, the provided technical solution is as follows:

[0013] A preparation method of sunflower low-ester pectin, comprising the following steps:

[0014] Take sunflower flower discs, after microwave treatment and freeze-drying, obtain pretreated flower discs;

[0015] Weigh the pretreated flower discs, place them in an ethanol solution, perform ultrasonic treatment, soak, filter, and obtain flower disc filter cakes;

[0016] Add a mixed enzyme to the flower disc filter cakes, perform enzymatic hydrolysis, and the mixed enzyme accounts for 1% - 2% of the mass of the pretreated flower discs; the mixed enzyme includes: cellulase and pectinase, and calculated by mass ratio, cellulase:pectinase = (2 - 4):1, to obtain the enzymatically hydrolyzed mixture;

[0017] Filter the enzymatically hydrolyzed mixture, collect the filtrate and the filter residue, centrifuge the filtrate, and obtain the supernatant;

[0018] Add an ethanol solution to the obtained supernatant for alcohol precipitation treatment, let it stand, centrifuge, and the obtained precipitate is sunflower low-ester pectin.

[0019] Preferably, the filtration uses four layers of 100-mesh nylon gauze.

[0020] Preferably, filter the enzymatically hydrolyzed mixture, and at the same time collect the filter residue, add the filter residue to the mixed enzyme, repeat the extraction 1 - 2 times under the same enzymatic hydrolysis conditions, filter, combine the filtrates and centrifuge to obtain the supernatant.

[0021] Preferably, for the centrifugation, the rotation speed is 4500 rpm and the time is 10 min.

[0022] Furthermore, during the ultrasonic treatment, the ethanol concentration is 70% - 90%, the ultrasonic power is 150 W - 250 W, and the time is 15 min - 25 min.

[0023] Further, during the microwave treatment, the microwave power is 700W - 800W and the time is 90S - 110S.

[0024] Further, the temperature for enzymatic hydrolysis is 45°C - 55°C and the enzymatic hydrolysis time is 40min - 60min.

[0025] Further, during the alcohol precipitation treatment, the concentration of the ethanol solution is 90% - 95%, and the volume of the ethanol solution is 2.5 - 3.5 times that of the filtrate.

[0026] Sunflower low - ester pectin is prepared by the preparation method of the sunflower low - ester pectin.

[0027] The coating adhesion liquid contains the sunflower low - ester pectin described above.

[0028] The preparation method of the coating adhesion liquid includes the following steps:

[0029] Take the sunflower low - ester pectin and dissolve it in a solution to obtain a pectin adhesion liquid; add locust bean gum to the pectin adhesion liquid in batches, and then add carrageenan, and stir evenly to obtain the coating adhesion liquid.

[0030] Calculated by mass percentage of the solution, the sunflower low - ester pectin is 0.3% - 0.7%, the locust bean gum is 0.1% - 0.4%, and the carrageenan is 0.1% - 0.5%.

[0031] Preferably, the batches are 2 - 3 batches.

[0032] Preferably, the dissolution is by water - bath heating, the temperature is 55°C - 65°C, and the time is 10min - 20min.

[0033] The application of the sunflower low - ester pectin, or the coating adhesion liquid, or the preparation method of the coating adhesion liquid is applied to the preparation of coated melon seeds and / or coated nut kernels.

[0034] Further, applying the coating adhesion liquid to the preparation of coated melon seeds includes the following steps:

[0035] Mix the coating adhesion liquid and cooked melon seeds according to a mass ratio of 5 - 10:1, soak them to obtain wet melon seeds;

[0036] Take out the wet melon seeds and drain them, add seasoning powder and mix and stir evenly to obtain wet coated melon seeds;

[0037] Dry the wet coated melon seeds to obtain the finished coated melon seeds.

[0038] Preferably, a mesh - belt drying equipment is used to achieve zoned gradient temperature - controlled drying, and the parameters of each temperature zone are as follows:

[0039] In Zone 1, the drying temperature is 50°C to 60°C and the time is 30 min to 50 min; in Zone 2, the drying temperature is 80°C to 100°C and the time is 30 min to 50 min; in Zone 3, the drying temperature is 100°C to 110°C and the time is 60 min to 80 min. A temperature ramp process is set between each zone, and the ramp time is 3 min to 4 min.

[0040] 3. Beneficial effects

[0041] Adopting the technical solution provided by the present invention, compared with the existing well-known technologies, it has the following beneficial effects:

[0042] (1) In the preparation method of sunflower low-ester pectin of the present invention, microwave treatment and freeze-drying are first performed on sunflower heads, which shortens the extraction time, improves the extraction efficiency and the quality of pectin. Microwave treatment can quickly heat the material, rapidly destroy the cell structure in the sunflower heads, increase the permeability of the cell wall, and thus accelerate the dissolution of pectin; freeze-drying removes the excess water in the sunflower heads. Since it is carried out at low temperature, it can better maintain the molecular structure, content and physicochemical properties of pectin. The pectin after freeze-drying treatment is superior in quality, and key indicators such as the molecular weight and degree of esterification of pectin are better retained. Ultrasonic treatment is used to destroy the plant cell wall of the sunflower head, providing a better basis for enzymatic hydrolysis, and enzymatic hydrolysis further specifically decomposes pectin. The combination of the two can significantly improve the yield of pectin. Specifically, ultrasonic waves can generate high-frequency vibrations, which can break the plant cell wall and make the pectin inside the cell easier to release. And ultrasonic treatment can increase the surface area after the cell wall is broken, enabling the subsequent enzymatic treatment to act more effectively on pectin substances. Enzymatic hydrolysis uses a compound solution of cellulase and pectinase. The synergistic action of the two enzymes can more effectively destroy the structure of the sunflower head cell wall. Cellulase mainly acts on cellulose and decomposes the cellulose component in the plant cell wall, while pectinase acts on pectin and separates it from the cell wall. The combination of the two can more comprehensively degrade the components of the plant cell wall, thus significantly increasing the dissolution rate of pectin and improving the extraction rate. Compared with the traditional acid extraction method, it solves the problems of low extraction efficiency, high energy consumption and serious environmental pollution. This method has high economic and social benefits.

[0043] (2) The extraction rate of the sunflower low-ester pectin of the present invention can reach up to 20.45%, and it has excellent gelling properties, natural environmental protection and health functional properties.

[0044] (3) The coating adhesion liquid of the present invention contains sunflower low-ester pectin, which has strong adhesion, high stability, and excellent moisture barrier performance. Sunflower low-ester pectin is a natural extract with good biocompatibility and safety. This enables it to meet consumers' demands for natural and healthy foods while meeting strict food safety standards when used as a component of the coating adhesion liquid in the food industry.

[0045] (4) The preparation method of the coating adhesion liquid of the present invention is as follows: dissolve sunflower low-ester pectin in a solution, then add locust bean gum in batches, and then add carrageenan, and stir evenly to obtain the coating adhesion liquid. Pectin is mainly composed of galacturonic acid and has a linear or slightly branched structure, which can form a gel in water. Carrageenan has a unique triple helix structure and can form a strong gel at a low concentration. Locust bean gum has a branched structure and can form good synergistic effects with other colloids. When the three are compounded, the different molecular structures can complement each other to form a more compact and stable network structure, thereby improving the viscosity and stability of the adhesion liquid. This preparation method is simple. Adding locust bean gum in batches can ensure that each batch of colloid has enough time to completely dissolve and disperse in the solvent, which can optimize the dissolution, dispersion, interaction, and gelation processes of the colloids, thereby preparing an adhesion liquid with more excellent performance.

[0046] (5) The application of the sunflower low-ester pectin, or the coating adhesion liquid, or the preparation method of the coating adhesion liquid of the present invention in the preparation of coated melon seeds or coated nut kernels can form a uniform and firm coating layer on the surface of the melon seeds or nuts. This characteristic makes the coating layer not easy to fall off, further improves its moisture barrier performance, effectively prevents the penetration of moisture, and the obtained coated melon seeds have greatly reduced powder loss rate and stickiness rate. At the same time, in a high-humidity environment, the melon seeds can also maintain dryness and crispness, reduce the quality decline caused by moisture absorption, and thus extend the shelf life of the coated melon seeds. Detailed Embodiments

[0047] To further understand the content of the present invention, the present invention will be described in detail in combination with the embodiments.

[0048] Example 1

[0049] The preparation method of the sunflower low-ester pectin in this example includes the following steps:

[0050] S1. Select mature sunflower disks without pests and diseases, wash them with pure water to remove impurities such as soil and dust, cut them into small pieces of 2 cm * 2 cm, and perform microwave treatment with a microwave power of 700 W and a time of 90 s. Subsequently, freeze-dry for 24 h to remove moisture to obtain the pretreated sunflower disks;

[0051] S2. Weigh 10 g of the pretreated sunflower disk and place it in 250 mL of 70% ethanol solution for ultrasonic treatment. The ultrasonic power is 150 W, and the ultrasonic treatment time is 15 min. Then, soak it at room temperature for 2 h to remove substances such as pigments and small molecules. Filter it with four layers of 100-mesh nylon gauze, and rinse the sunflower disk with pure water to remove ethanol to obtain a sunflower disk filter cake.

[0052] S3. Transfer the obtained sunflower disk filter cake to a 500 mL beaker, add a mixed enzyme to the sunflower disk filter cake for enzymatic hydrolysis. The mixed enzyme accounts for 1% of the mass of the pretreated sunflower disk. The mixed enzyme includes: cellulase and pectinase. Calculated by mass ratio, cellulase∶pectinase = 4∶1. The temperature of the enzymatic hydrolysis system is 45 °C, and the enzymatic hydrolysis time is 40 min to obtain an enzymatically hydrolyzed mixture.

[0053] S4. Filter the enzymatically hydrolyzed mixture with four layers of 100-mesh nylon gauze, collect the filtrate and the filter residue. The filter residue is repeatedly extracted twice under the same conditions as in step S3. Combine the filtrates extracted three times, and centrifuge the combined filtrate at a speed of 4500 rpm for 10 min to obtain a supernatant.

[0054] S5. Place the supernatant in a 500 mL beaker, add 90% ethanol solution for alcohol precipitation treatment. The volume of the ethanol solution is 2.5 times the volume of the combined filtrate. Let it stand for 24 h, then centrifuge at a speed of 4500 rpm for 10 min to obtain a precipitate at the bottom of the centrifuge tube. After freeze-drying, it is sunflower low-ester pectin.

[0055] The yield of the sunflower low-ester pectin (hereinafter referred to as sunflower disk pectin) prepared in this example is 19.28%.

[0056] Example 2

[0057] The preparation method of the sunflower low-ester pectin in this example includes the following steps:

[0058] S1. Select mature sunflower disks without pests and diseases, wash them with pure water to remove impurities such as soil and dust, cut them into small pieces of 2 cm * 2 cm, and perform microwave treatment. The microwave power is 800 W, and the time is 110 S. Then, freeze-dry for 24 h to remove moisture to obtain a pretreated sunflower disk.

[0059] S2. Weigh 20 g of the pretreated sunflower disk and place it in 250 mL of 90% ethanol solution for ultrasonic treatment. The ultrasonic power is 250 W, and the ultrasonic treatment time is 25 min. Then, soak it at room temperature for 3 h to remove substances such as pigments and small molecules. Filter it with four layers of 100-mesh nylon gauze, and rinse the sunflower disk with pure water to remove ethanol to obtain a sunflower disk filter cake.

[0060] S3. Transfer the obtained sunflower disk filter cake to a 500 mL beaker, add a mixed enzyme to the sunflower disk filter cake for enzymatic hydrolysis. The mixed enzyme accounts for 2% of the mass of the pretreated sunflower disk. The mixed enzyme includes cellulase and pectinase. Calculated by mass ratio, cellulase:pectinase = 3:1. The temperature of the enzymatic hydrolysis system is 55 °C, and the enzymatic hydrolysis time is 60 min to obtain the enzymatically hydrolyzed mixture.

[0061] S4. Filter the enzymatically hydrolyzed mixture through four layers of 100-mesh nylon gauze, collect the filtrate and the filter residue. The filter residue is extracted twice under the same conditions as in step S3, and the filtrates obtained from the three extractions are combined. The combined filtrate is centrifuged at a speed of 4500 rpm for 10 min to obtain the supernatant.

[0062] S5. Place the supernatant in a 500 mL beaker, add a 90% ethanol solution for alcohol precipitation treatment. The volume of the ethanol solution is 3.5 times the volume of the combined filtrate. Let it stand for 24 h, then centrifuge at a speed of 4500 rpm for 10 min to obtain the precipitate at the bottom of the centrifuge tube. After freeze-drying, it is sunflower low-ester pectin.

[0063] The yield of sunflower disk pectin prepared in this example is 19.73%.

[0064] Example 3

[0065] The preparation method of sunflower low-ester pectin in this example includes the following steps:

[0066] S1. Select mature sunflower disks without diseases and pests, wash them with pure water to remove impurities such as soil and dust, cut them into small pieces of 2 cm * 2 cm, and perform microwave treatment with a microwave power of 750 W for 100 s. Then, freeze-dry for 24 h to remove moisture to obtain the pretreated sunflower disks.

[0067] S2. Weigh 15 g of the pretreated sunflower disks and place them in a 250 mL 80% ethanol solution for ultrasonic treatment with an ultrasonic power of 200 W and an ultrasonic treatment time of 20 min. Then, soak at room temperature for 2.5 h to remove substances such as pigments and small molecules. Filter with four layers of 100-mesh nylon gauze and rinse the sunflower disks with pure water to remove ethanol to obtain the sunflower disk filter cake.

[0068] S3. Transfer the obtained sunflower disk filter cake to a 500 mL beaker, add a mixed enzyme to the sunflower disk filter cake for enzymatic hydrolysis. The mixed enzyme accounts for 1.5% of the mass of the pretreated sunflower disk. The mixed enzyme includes cellulase and pectinase. Calculated by mass ratio, cellulase:pectinase = 3.5:1. The temperature of the enzymatic hydrolysis system is 50 °C, and the enzymatic hydrolysis time is 50 min to obtain the enzymatically hydrolyzed mixture.

[0069] S4. Filter the mixture after enzymatic hydrolysis through four layers of 100-mesh nylon gauze, collect the filtrate and the residue. Repeat the extraction of the residue twice under the same above conditions. Combine the filtrates from the three extractions, and centrifuge the combined filtrate at a speed of 4500 rpm for 10 min to obtain the supernatant.

[0070] S5. Place the supernatant in a 500 mL beaker, add 90% ethanol solution for alcohol precipitation. The volume of the ethanol solution is 3 times the volume of the combined filtrate. Let it stand for 24 h, then centrifuge at a speed of 4500 rpm for 10 min to obtain the precipitate at the bottom of the centrifuge tube. After freeze-drying, it is sunflower low-ester pectin.

[0071] The yield of sunflower disk pectin obtained in this example is 19.73%.

[0072] Comparative Example 1

[0073] The preparation method of sunflower low-ester pectin in this comparative example is basically the same as that in Example 3, except that: ultrasonic treatment is not carried out in step S2.

[0074] The yield of sunflower disk pectin obtained in this comparative example is 11.84%, which is 42.10% lower than that in Example 3.

[0075] This is because the energy brought by ultrasonic treatment can change the conformation of cellulase, increase the chance of the combination of cellulose in the sunflower disk and the active center of cellulase, and accelerate the enzymatic reaction process.

[0076] Comparative Example 2

[0077] The preparation method of sunflower low-ester pectin in this comparative example is basically the same as that in Example 3, except that: only pectinase is added in step S3, and the pectinase accounts for 1.5% of the mass of the pretreated sunflower disk.

[0078] The yield of sunflower disk pectin obtained in this comparative example is 12.13%, which is 40.7% lower than that in Example 3.

[0079] When only pectinase is added during enzymatic hydrolysis and cellulase is not added, the yield of sunflower disk pectin decreases. This is because cellulase can hydrolyze the cellulose in the sunflower disk cell wall, which helps to release sunflower disk pectin.

[0080] Comparative Example 3

[0081] The preparation method of sunflower low-ester pectin in this comparative example is basically the same as that in Example 3, except that: only cellulase is added in step S3, and the cellulase accounts for 1.5% of the mass of the pretreated sunflower disk.

[0082] The yield of sunflower disk pectin obtained in this comparative example is 9.85%.

[0083] The extraction efficiency of sunflower disk pectin using only cellulase is relatively low. This is because the sunflower disk cell wall contains not only cellulose, but also various components such as lignin and pectin. Using cellulase alone can only partially degrade cellulose and cannot completely break down other components, resulting in insufficient release of pectin. At the same time, pectin may bind to metal ions in the cell wall to form stable complexes, hindering the dissolution and extraction of pectin. Using cellulase alone cannot relieve the blocking effect of these ions on pectin.

[0084] Comparative Example 4

[0085] The preparation method of low-ester pectin from sunflower in this comparative example is basically the same as that in Example 3, except that: the mixed enzymes added in step S3 include: 0.15 g of cellulase, 0.05 g of pectinase, 0.05 g of β-glucanase, and 0.05 g of neutral protease.

[0086] The yield of sunflower disk pectin obtained in this comparative example is 10.36%.

[0087] The extraction effect of using four enzymes, namely cellulase, pectinase, β-glucanase, and neutral protease, is worse than that of using two enzymes, cellulase and pectinase. This is because cellulase and pectinase mainly act on cellulose and pectin in the plant cell wall, while β-glucanase and neutral protease act on β-glucan and protein. Neutral protease will decompose the protein in the cell wall, and these proteins play a certain structural support role in the extraction process. After decomposition, it affects the extraction efficiency of pectin.

[0088] Comparative Example 5

[0089] The preparation method of low-ester pectin from sunflower in this comparative example is basically the same as that in Example 3, except that: in step S3, the ratio of cellulase to pectinase is 5:1.

[0090] The yield of sunflower disk pectin obtained in this comparative example is 9.04%.

[0091] When pectinase and cellulase are used together, a synergistic effect can be produced, significantly improving the extraction efficiency of sunflower disk pectin. However, when the proportion of cellulose is too high, it will over-decompose the cellulose in the cell wall, but the decomposition effect on pectin is insufficient, thus destroying the synergistic effect between the two enzymes.

[0092] Comparative Example 6

[0093] The preparation method of low-ester pectin from sunflower in this comparative example is basically the same as that in Example 3, except that: in step S3, the ratio of cellulase to pectinase is 0.5:1

[0094] The yield of sunflower disk pectin obtained in this comparative example is 8.47%.

[0095] Pectin mainly exists in the plant cell wall. Pectinase can effectively decompose pectin, making the cell wall become loose, thus making it easier to release pectin. When the proportion of cellulase is too low, the cellulose in the cell wall cannot be fully decomposed, and the release efficiency of pectin will be affected, resulting in a decrease in the extraction rate.

[0096] Comparative Example 7

[0097] The preparation method of sunflower low-ester pectin in this comparative example is basically the same as that in Example 3, except that: in step S3, the mixed enzyme accounts for 0.5% of the mass of the pretreated sunflower disk.

[0098] The yield of sunflower disk pectin obtained in this comparative example is 8.02%.

[0099] This is mainly because when the concentration of the compound enzyme solution is low, the number of enzyme molecules is insufficient and cannot fully act on the sunflower disk plant cell wall, resulting in incomplete decomposition and release of pectin, thus reducing the extraction of pectin.

[0100] Comparative Example 8

[0101] The preparation method of sunflower low-ester pectin in this comparative example is basically the same as that in Example 3, except that: in step S3, the mixed enzyme accounts for 3% of the mass of the pretreated sunflower disk.

[0102] The yield of sunflower disk pectin obtained in this comparative example is 10.90%.

[0103] This is mainly because too high an enzyme concentration may cause the pectin molecular structure to be excessively degraded, especially damaging the main chain and side chain structures of pectin, thus affecting the extraction rate and quality of sunflower disk pectin.

[0104] Comparative Example 9

[0105] The preparation method of sunflower low-ester pectin in this comparative example is basically the same as that in Example 3, except that:

[0106] Replace steps S2 and S3 with: Transfer the sunflower disk blocks obtained in step S1 to a 500 mL beaker, add 200 mL of pure water and 0.4% (m / V) oxalic acid solution, heat in a 70 °C water bath for 1 h, and take it out and let it stand at room temperature for 20 h.

[0107] The yield of sunflower disk pectin obtained in this comparative example is 12.79%. Compared with Example 3, the yield of sunflower disk pectin decreased by 37.5%. Although oxalic acid, as a chelating agent, can combine with Ca 2+ in pectic acid to convert insoluble calcium pectate into soluble pectin. However, compared with ultrasonic treatment plus enzymatic hydrolysis reaction, the addition of oxalic acid will, to a certain extent, reduce the pH value of the constructed extraction liquid system, resulting in acid hydrolysis of pectin. Therefore, the yield of sunflower disk pectin prepared by the oxalic acid hydrolysis method is lower than that of ultrasonic treatment plus enzymatic hydrolysis reaction.

[0108] Table 1 Summary Table of Extraction Rate of Sunflower Low-Ester Pectin

[0109]

[0110] Extraction rate of sunflower low-ester pectin (%) = (weight of sunflower disk pectin obtained after freeze-drying / weight of sunflower disk after freeze-drying) * 100%; The extraction rate of sunflower low-ester pectin is the pectin yield rate.

[0111] Example 4

[0112] The preparation method of the coated melon seeds in this example includes the following steps:

[0113] (1) Preparation of the coating adhesion liquid:

[0114] Accurately weigh 1 g of the sunflower disk pectin prepared in Example 3 and mix it with 300 mL of pure water, place it in a water bath at 55 °C and heat for 10 min to obtain a pectin adhesion liquid. Add 0.5 g of locust bean gum (0.25 g per batch on average) and 0.5 g of carrageenan to the pectin adhesion liquid in 2 batches, stir evenly and then cool to room temperature to obtain the coating adhesion liquid.

[0115] (2) Coating

[0116] Mix the coating adhesion liquid and the cooked melon seeds according to a mass ratio of 5:1, soak them at room temperature for 20 min to obtain wet melon seeds;

[0117] Take out the wet melon seeds and drain them until there are no linear water droplets, add seasoning powder and mix and stir evenly. Calculated according to the mass ratio, cooked melon seeds: seasoning powder = 7:1 to obtain coated wet melon seeds.

[0118] (3) Drying

[0119] Dry the coated wet melon seeds until the moisture content is 1.8% to obtain the finished coated melon seeds.

[0120] Specifically, a mesh belt drying equipment is used to achieve zone gradient temperature control drying. The parameters of each temperature zone are as follows:

[0121] Temperature zone 1, drying temperature is 50 °C, time is 30 min; Temperature zone 2, drying temperature is 80 °C, time is 30 min; Temperature zone 3, drying temperature is 100 °C, time is 60 min. A temperature ramp process is set between each temperature zone, and the ramp time is 3 min. The moisture content of the melon seeds after leaving the drying line is 1.8%. After the melon seeds are naturally cooled to room temperature, the finished coated melon seeds are obtained.

[0122] The coated melon seeds prepared in this example have a powder loss rate of 3.26%, a sticky hand rate A of 1.20%, and a sticky hand rate B of 3.62%.

[0123] Example 5

[0124] The preparation method of the coated melon seeds in this embodiment includes the following steps:

[0125] (1) Preparation of the coating adhesion liquid:

[0126] Accurately weigh 2 g of the sunflower disk pectin prepared in Example 3 and mix it with 300 mL of pure water, place it in a water bath at 65 °C and heat for 10 min to obtain a pectin adhesion liquid. To the pectin adhesion liquid, add 1 g of locust bean gum (0.33 g per batch on average) and 1.5 g of carrageenan in 3 batches, stir evenly and then cool to room temperature to obtain the coating adhesion liquid.

[0127] (2) Coating

[0128] Mix the coating adhesion liquid and the cooked melon seeds in a mass ratio of 10:1, soak at room temperature for 30 min to obtain wet melon seeds;

[0129] Take out the wet melon seeds and drain until there are no linear water droplets, add seasoning powder and mix and stir evenly. Calculated by mass ratio, cooked melon seeds: seasoning powder = 5:1 to obtain coated wet melon seeds.

[0130] (3) Drying

[0131] Dry the coated wet melon seeds until the moisture content is 1.8% to obtain the finished product of coated melon seeds.

[0132] Specifically, a mesh belt drying equipment is used to achieve zone gradient temperature-controlled drying. The parameters of each temperature zone are as follows:

[0133] In the first temperature zone, the drying temperature is 60 °C and the time is 50 min; in the second temperature zone, the drying temperature is 100 °C and the time is 50 min; in the third temperature zone, the drying temperature is 110 °C and the time is 80 min. A temperature ramp process is set between each temperature zone, and the ramp time is 4 min. The moisture content of the melon seeds after leaving the drying line is 1.8%. After the melon seeds are naturally cooled to room temperature, the finished product of coated melon seeds is obtained.

[0134] For the coated melon seeds prepared in this embodiment, the powder loss rate is 3.93%, the stickiness rate A is 1.37%, and the stickiness rate B is 3.86%.

[0135] Example 6

[0136] The preparation method of the coated melon seeds in this embodiment includes the following steps:

[0137] (1) Preparation of the coating adhesion liquid:

[0138] Accurately weigh 1.5 g of the sunflower disk pectin prepared in Example 3, mix it with 300 mL of pure water, place it in a water bath at 60 °C and heat for 15 min to obtain a pectin adhesion solution. To the pectin adhesion solution, add 0.75 g of locust bean gum (an average of 0.375 g per batch) and 1 g of carrageenan in 2 batches. After stirring evenly, cool to room temperature to obtain a coating adhesion solution.

[0139] (2) Coating

[0140] Mix the coating adhesion solution and the cooked melon seeds in a mass ratio of 7.5∶1, soak at room temperature for 25 min to obtain wet melon seeds;

[0141] Take out the wet melon seeds and drain them until there are no linear water droplets, add seasoning powder and mix and stir evenly. Calculated by mass ratio, cooked melon seeds∶seasoning powder = 6∶1 to obtain coated wet melon seeds.

[0142] (3) Drying

[0143] Dry the coated wet melon seeds until the moisture content is 1.8% to obtain the finished coated melon seeds.

[0144] Specifically, a mesh belt drying equipment is used to achieve zone gradient temperature control drying. The parameters of each temperature zone are as follows:

[0145] In the first temperature zone, the drying temperature is 55 °C and the time is 40 min; in the second temperature zone, the drying temperature is 90 °C and the time is 40 min; in the third temperature zone, the drying temperature is 105 °C and the time is 70 min. A temperature ramp process is set between each temperature zone, and the ramp time is 4 min. The moisture content of the melon seeds after leaving the drying line is 1.8%. After the melon seeds are naturally cooled to room temperature, the finished coated melon seeds are obtained.

[0146] The coated melon seeds prepared in this example have a powder loss rate of 3.12%, a stickiness rate A of 1.14%, and a stickiness rate B of 2.53%.

[0147] Comparative Example 10

[0148] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0149] Preparation of the coating adhesion solution: Accurately weigh 3.25 g of locust bean gum, mix it with 300 mL of pure water, place it in a water bath at 60 °C and heat for 15 min, stir evenly and then cool to room temperature to obtain the coating adhesion solution.

[0150] The powder loss rate of the coated melon seeds prepared in this comparative example is 8.76%, the stickiness rate A is 8.51%, and the stickiness rate B is 34.36%. Compared with Example 6, they are increased by about 2.8 times, 7.5 times, and 13.6 times respectively.

[0151] The above results indicate that the colloidal film prepared by adding only locust bean gum has poor viscosity and cannot completely adhere the seasoning powder to the surface. At the same time, the moisture barrier property of the coated melon seeds is also poor.

[0152] Comparative Example 11

[0153] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0154] Preparation of the coating adhesion liquid: Accurately weigh 3.25 g of sunflower disk pectin prepared in Example 3, mix it with 300 mL of pure water, place it in a water bath at 60 °C and heat for 15 min, stir evenly and then cool to room temperature to obtain the coating adhesion liquid.

[0155] The powder dropping rate of the coated melon seeds prepared in this comparative example is 6.04%, the sticky hand rate A is 6.34%, and the sticky hand rate B is 31.41%.

[0156] The reason why the effect of the three-component compound is better than that of adding only sunflower disk pectin is as follows: Pectin is mainly composed of galacturonic acid and has a linear or slightly branched structure, which can form a gel in water. Carrageenan has a unique triple helix structure and can form a strong gel at a low concentration. Locust bean gum has a branched structure and can form a good synergistic effect with other colloids. In summary, when the three are compounded, different molecular structures can complement each other to form a more compact and stable network structure, thereby improving the viscosity and stability of the adhesion liquid. Using sunflower disk pectin alone cannot form a stable network structure, and the effect of the prepared adhesion liquid will also be poor.

[0157] Comparative Example 12

[0158] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0159] Preparation of the coating adhesion liquid: Accurately weigh 3.25 g of carrageenan, mix it with 300 mL of pure water, place it in a water bath at 60 °C and heat for 15 min, stir evenly and then cool to room temperature to obtain the coating adhesion liquid.

[0160] The powder dropping rate of the coated melon seeds prepared in this comparative example is 20.37%, the sticky hand rate A is 3.08%, and the sticky hand rate B is 30.20%.

[0161] The coating adhesion liquid prepared by adding only carrageenan has poor adhesion to the seasoning powder, a high powder dropping rate of the melon seeds, and a high sticky hand rate. This is because when carrageenan is used alone, its gel is brittle, has little elasticity, and is prone to syneresis. However, when carrageenan is used in combination with sunflower disk pectin and locust bean gum, the above disadvantages can be improved through the mutual synergistic effect between different polysaccharide molecules, making the gel have better properties.

[0162] Comparative Example 13

[0163] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0164] Carrageenan was not added in the preparation of the coating adhesion liquid.

[0165] The powder shedding rate of the coated melon seeds prepared in this comparative example is 7.81%, the stickiness rate A is 4.77%, and the stickiness rate B is 38.74%.

[0166] The reasons for the poor performance of the adhesion liquid with only sunflower disc pectin and locust bean gum added are as follows: In the complex system of the three colloids, the carrageenan molecules can crosslink with the mannan backbone of locust bean gum, which can increase the density of the network structure of the adhesion liquid to a certain extent.

[0167] Comparative Example 14

[0168] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0169] Preparation of the coating adhesion liquid: Accurately weigh 1.5 g of the sunflower disc pectin prepared in Example 3 and mix it with 300 mL of pure water, place it in a water bath at 60 °C and heat for 15 min to obtain the pectin adhesion liquid. Add 0.75 g of carrageenan to the pectin adhesion liquid, stir evenly and then cool to room temperature to obtain the coating adhesion liquid.

[0170] The powder shedding rate of the coated melon seeds prepared in this comparative example is 8.34%, the stickiness rate A is 4.61%, and the stickiness rate B is 43.85%.

[0171] The effect of adding only sunflower disc pectin and carrageenan in the adhesion liquid is not good, mainly because the synergistic effect of locust bean gum is lacking. The compounding of sunflower disc pectin, carrageenan and locust bean gum can significantly improve the strength, elasticity and water retention of the gel, thereby improving the performance of the adhesion liquid.

[0172] Comparative Example 15

[0173] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0174] 0.75 g of locust bean gum and 0.75 g of carrageenan were added in the preparation of the coating adhesion liquid.

[0175] The powder shedding rate of the coated melon seeds prepared in this comparative example is 10.55%, the stickiness rate A is 3.93%, and the stickiness rate B is 43.56%.

[0176] The effect of adding only locust bean gum and carrageenan in the adhesion liquid is not good, mainly because sunflower disc pectin has good gel-forming ability, while the gel performance of carrageenan and locust bean gum alone is weak and unstable.

[0177] Comparative Example 16

[0178] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0179] During the preparation of the coating adhesion liquid, 1 g of locust bean gum is directly added without batches.

[0180] The powder loss rate of the coated melon seeds prepared in this comparative example is 10.21%, the stickiness rate A is 7.19%, and the stickiness rate B is 36.87%. Compared with Example 6, the powder loss rate, the stickiness rate A, and the stickiness rate B are increased by 3.3 times, 6.3 times, and 14.6 times respectively.

[0181] When locust bean gum is added without batches, the uniformity of the prepared adhesive system is poor and caking occurs. Adding locust bean gum in batches can ensure that each batch of colloid has enough time to completely dissolve and disperse in the solvent, avoiding the problem that some colloids may not be fully dissolved or unevenly dispersed caused by adding all at once; and adding in batches allows each batch of locust bean gum to interact with other colloids or solvent molecules after addition. This step-by-step interaction helps to form a tighter and more ordered colloid network. Therefore, adding in batches can optimize the processes of colloid dissolution, dispersion, interaction, and gelation, thereby preparing an adhesion liquid with more excellent performance.

[0182] Comparative Example 17

[0183] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0184] During the preparation of the coating adhesion liquid, sunflower disk pectin is replaced with an equal mass of citrus pectin.

[0185] The powder loss rate of the coated melon seeds prepared in this comparative example is 12.23%, the stickiness rate A is 8.40%, and the stickiness rate B is 45.38%.

[0186] After replacing sunflower disk pectin with citrus pectin, the powder loss rate, the stickiness rate A, and the stickiness rate B all increase because pectins from different sources have differences in molecular structure and degree of esterification, and these differences affect the interaction between pectin and other colloids and gel properties. The physical and chemical properties and structure of sunflower disk pectin are more suitable for forming a stable gel network with locust bean gum and carrageenan.

[0187] Comparative Example 18

[0188] The preparation method of the coated melon seeds in this comparative example is basically the same as that in Example 6, except that:

[0189] During the preparation of the coating adhesion liquid, carrageenan is replaced with an equal mass of gelatin.

[0190] The powder loss rate of the coated melon seeds prepared in this comparative example is 10.19%, the stickiness rate A is 7.14%, and the stickiness rate B is 40.95%.

[0191] After replacing carrageenan with gelatin, the powder loss rate, the stickiness rate A, and the stickiness rate B all increase. Because the gelation time of gelatin is longer, the gel strength is weak, and the concentration required to form a gel is higher. The compound of carrageenan, locust bean gum, and sunflower disc pectin in this application can produce a synergistic effect. In contrast, the compound of gelatin with locust bean gum and pectin lacks this synergistic effect, resulting in a gel effect inferior to the compound system of this application (i.e., the coating adhesion liquid of this application).

[0192] Comparative Example 19

[0193] The preparation method of the coated melon seeds in this comparative example is basically the same as that of Example 6, except that:

[0194] In the preparation of the coating adhesion liquid, locust bean gum is replaced with an equal mass of guar gum.

[0195] The powder loss rate of the coated melon seeds prepared in this comparative example is 12.47%, the stickiness rate A is 6.29%, and the stickiness rate B is 48.07%.

[0196] After replacing locust bean gum with guar gum, the powder loss rate, the stickiness rate A, and the stickiness rate B all increase. This is mainly because guar gum is a kind of high molecular polysaccharide with good thickening and gelling properties, but its gel strength and elasticity are inferior to those of locust bean gum. Therefore, the synergistic effect of guar gum on the compound system is poor.

[0197] Table 2 Summary table of detection indexes of coated melon seeds

[0198]

[0199] Powder loss rate (%) = [(weight of seasoning powder + weight of melon seeds - weight of melon seeds after coating) / (weight of seasoning powder + weight of melon seeds)] * 100%;

[0200] Stickiness rate (%) = (number of sticky melon seed grains / total number of melon seed grains) * 100%;

[0201] Among them, the sample for measuring the stickiness rate A is the dried coated melon seeds, and the stickiness rate B is the sample of the above dried coated melon seeds after standing in a constant temperature and humidity box (humidity 90%, temperature 50°C) for 2 h.

[0202] The above-described embodiments merely represent the preferred embodiments of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several variations, improvements, and substitutions can be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

Claims

1. Preparation method of sunflower low-ester pectin, characterized in that: It includes the following steps: Orient the sunflower disk, and after microwave treatment and freeze-drying, obtain a pretreated sunflower disk; Weigh the pretreated sunflower disk, place it in an ethanol solution, perform ultrasonic treatment, soak it, filter it, and obtain a sunflower disk filter cake; Add a mixed enzyme to the sunflower disk filter cake for enzymatic hydrolysis. The mixed enzyme accounts for 1% - 2% of the mass of the pretreated sunflower disk. The mixed enzyme includes: cellulase and pectinase. Calculated by mass ratio, cellulase∶pectinase = (2 - 4)∶1, and obtain a hydrolyzed mixture; Filter the hydrolyzed mixture, collect the filtrate, and centrifuge the filtrate to obtain a supernatant; Add an ethanol solution to the obtained supernatant for alcohol precipitation treatment, let it stand, and centrifuge to obtain the sunflower low-ester pectin.

2. The preparation method of sunflower low-ester pectin according to claim 1, characterized in that: During the ultrasonic treatment, the ethanol concentration is 70% - 90%, the ultrasonic power is 150W - 250W, and the time is 15min - 25min.

3. The preparation method of sunflower low-ester pectin according to claim 2, characterized in that: During the microwave treatment, the microwave power is 700W - 800W, and the time is 90S - 110S.

4. The preparation method of low-ester pectin from sunflower according to claim 3, characterized in that: The temperature of the enzymatic hydrolysis is 45°C - 55°C, and the enzymatic hydrolysis time is 40min - 60min.

5. The preparation method of sunflower low-ester pectin according to claim 4, characterized in that: During the alcohol precipitation treatment, the ethanol solution concentration is 90% - 95%, and the volume of the ethanol solution is 2.5 - 3.5 times the volume of the filtrate.

6. Sunflower low-ester pectin, characterized in that: Prepared by the method according to any one of claims 1 - 5.

7. Wrapping clothing adhesion liquid, characterized in that: Containing the sunflower low-ester pectin described in claim 6.

8. The preparation method of the coating adhesion liquid according to claim 7, characterized in that: It includes the following steps: Dissolve the sunflower low-ester pectin in a solution to obtain a pectin adhesion solution; Add locust bean gum to the pectin adhesion solution in batches, and then add carrageenan, and stir evenly to obtain a coating adhesion solution. Calculated by mass percentage of the solution, the sunflower low-ester pectin is 0.3% - 0.7%, locust bean gum is 0.1% - 0.4%, and carrageenan is 0.1% - 0.5%.

9. Use of the sunflower low-ester pectin according to claim 6, or the coating adhesion liquid according to claim 7, or the preparation method of the coating adhesion liquid according to claim 8, characterized in that: Applied to the preparation of coated melon seeds and / or coated nut kernels.

10. The application according to claim 9, characterized in that: Applying the coating adhesion solution to the preparation of coated melon seeds includes the following steps: Mix the coating adhesion solution and melon seeds according to a mass ratio of 5 - 10∶1, soak them to obtain wet melon seeds; Take out the wet melon seeds and drain them, add seasoning powder, mix and stir evenly to obtain coated wet melon seeds with powder; Dry the coated wet melon seeds with powder to obtain the finished product of coated melon seeds.

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