阅读说明：本技术 一种葡萄糖异构化生产糖浆的工艺 (Process for producing syrup by glucose isomerization ) 是由 毛强平 于 2017-11-03 设计创作，主要内容包括：本发明提供一种葡萄糖异构化生产糖浆的工艺,该方法包括下列步骤：淀粉乳液化、糖化、陶瓷膜除杂澄清脱色、纳滤膜脱色脱盐、异构化酶异构化。将脱色和脱盐放在纳滤膜处理过程的同一步中进行,具有步骤简单的优点,纳滤膜脱色液透光度可达99%以上,将葡萄糖浆进行异构化深加工,制备果葡糖浆时,纳滤膜还可以起到脱除钙离子的作用,避免了钙离子对异构化反应的抑制作用。(The invention provides a process for producing syrup by glucose isomerization, which comprises the following steps: liquefying starch milk, saccharifying, removing impurities by a ceramic membrane, clarifying and decoloring, decoloring and desalting by a nanofiltration membrane, and isomerizing by an isomerase. The decolorization and the desalination are carried out in the same step of the nanofiltration membrane treatment process, the method has the advantage of simple steps, the transmittance of the nanofiltration membrane decolorization solution can reach more than 99 percent, the glucose syrup is subjected to isomerization deep processing, and the nanofiltration membrane can also play a role in removing calcium ions when the fructose glucose syrup is prepared, so that the inhibition effect of the calcium ions on the isomerization reaction is avoided.)

1. A process for producing syrup by glucose isomerization is characterized by comprising the following steps: step 1, liquefying and saccharifying starch to obtain saccharified liquid; step 2, filtering the saccharified liquid by using a first separation membrane, and then filtering the filtered liquid by using a first nanofiltration membrane, wherein the permeated liquid is refined glucose syrup; and 3, carrying out isomerization reaction on the refined glucose syrup to obtain isomerized syrup.

2. The process for the isomerization of glucose to produce syrup of claim 1, wherein: the first separation membrane is made of a ceramic material; the average pore diameter of the first separation membrane is in the range of 5 to 500 nm.

3. The process for the isomerization of glucose to produce syrup according to claim 2, wherein: the average pore diameter of the first separation membrane is more preferably in the range of 20 to 200 nm.

4. The process for the isomerization of glucose to produce syrup according to claim 3, wherein: the range of the average pore diameter of the first separation membrane is most preferably 50 nm.

5. The process for the isomerization of glucose to produce syrup of claim 1, wherein: the operating pressure of the first separation membrane in the filtration is 0.1-0.5 MPa.

6. The process for the isomerization of glucose to produce syrup of claim 5, wherein: the operation pressure of the first separation membrane in filtration is more preferably 0.2-0.4 MPa.

7. The process for the isomerization of glucose to produce syrup of claim 6, wherein: the operating pressure in the filtration of the first separation membrane is most preferably 0.3 MPa.

8. The process for the isomerization of glucose to produce syrup of claim 5, wherein: the flow rate of the first separation membrane in the filtration is 1-6 m/s, preferably 2-5 m/s.

9. The process for the isomerization of glucose to produce syrup of claim 1, wherein: the material of the first nanofiltration membrane is selected from cellulose acetate polymer, polyamide, sulfonated polysulfone, polyethersulfone, polysulfone, polyacrylonitrile, polyester, polyimide, vinyl polymer and the like.

10. The process for the isomerization of glucose to produce syrup of claim 1, wherein: the molecular weight cut-off of the first nanofiltration membrane is 150-800 Da, and the filtration pressure of the nanofiltration is 0.5-2.5 MPa.

Technical Field

The invention relates to a process for producing syrup by glucose isomerization, belonging to the technical field of sugar production.

Background

Starch sugars are increasingly used in a variety of fields. The honey bee compound has obvious advantages compared with other sweeteners when being used as bee feed, fermentation carbon source and applied in food industry such as beverage, candy, pastry, beer, chewing gum, soy sauce and the like. With the increasing consumption concept and level, the demand for starch sugar is increasing, and the improvement of the production capacity of starch sugar and the product quality thereof is particularly important.

The clarification, filtration and decoloration of the starch sugar are one of the more key steps in the starch sugar production, and the filtration effect directly influences the refining cost and the product quality of the post-process of the starch sugar. The traditional starch sugar manufacturing process comprises the steps of liquefaction, deslagging, saccharification, filtration by a plate-and-frame filter press or a vacuum rotary drum filter, activated carbon decolorization, ion exchange and the like, a large amount of impurity sugar residues containing protein, fat and the like exist in the saccharification process, and the color and the refining difficulty of the saccharification liquid are increased by byproducts and pigments generated by the decomposition effect of the miscellaneous enzymes contained in the enzyme preparation. The treatment effect of the prior art using diatomite and active carbon is not good enough, and the sugar residue contains the impurities, which affects the utilization of the feed. In the old process, ion exchange needs to be carried out twice, calcium and magnesium ions are required to be added in the process, the ion exchange load is increased, and the influence on the quality of sugar is generated. According to the Chinese patent CN102337316A, a floatation cleaner is needed to remove impurities after liquefaction, so that the treatment process is increased, the treatment difficulty is increased, and the efficiency is reduced.

On the other hand, currently, starch sugar is the mainstream of glucose in China, and some problems still exist in the development of products such as high-fructose syrup (HFS). High fructose corn syrup, which is known as HFCS (high-fructose corn syrup) because it is mainly made of corn starch in the United states, is a liquid sugar containing fructose and glucose as main components in different proportions. Fructose and glucose in example (specification) were used as main components of liquid sugar. "high fructose syrup" although referred to as "high", high fructose syrup (HFCS) typically has a fructose content of only about half that of sucrose, and in beverages has a fructose content (55%) slightly more than glucose; meanwhile, starch sugar can also be prepared from other starches such as potato, sweet potato and the like. Chemically, it is the reaction of glucose with an isomerase, resulting from the isomerization (conversion) of glucose. The term "isomerization" means a chemical reaction in which compounds having the same molecular formula are converted into compounds having different intramolecular binding states (glucose and fructose are isomers of each other). In Japan, high fructose syrup is also called isomerized sugar. In the process for preparing high fructose corn syrup, glucose syrup is generally obtained by isomerizing glucose syrup by an isomerase, then performing ion exchange, activated carbon and concentration.

From the view of sugar supply in China, edible starch sugar is rarely produced as an isomerized sugar product for cold drinks besides mainstream glucose. According to the conversion of white sugar, the annual consumption of isomerized sugar is about 8-9 ten thousand tons by the sales amount, and only accounts for 0.08 percent of the total amount of the edible granulated sugar. The production and technical development of isomerized sugar are one of extremely weak projects in China at present, and have a very large development space.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the problems of poor impurity removal effect caused by active carbon decolorization and ion exchange in the production process of the starch syrup, poor color and purity of the syrup and influence on the quality of the high fructose corn syrup are solved, and the preparation method of the high fructose corn syrup is provided.

The technical scheme is as follows:

a preparation method of high fructose corn syrup comprises the following steps:

step 1, liquefying and saccharifying starch to obtain saccharified liquid;

step 2, filtering the saccharified liquid by using a first separation membrane, and then filtering the filtered liquid by using a first nanofiltration membrane, wherein the permeated liquid is refined glucose syrup;

step 3, carrying out isomerization reaction on the refined glucose syrup to obtain isomerized syrup;

step 4, adding a fructose adsorbent into the isomerized syrup for adsorption, filtering the adsorbent by using a second separation membrane, and desorbing the adsorbent to obtain the syrup subjected to adsorption treatment;

and 5, filtering the syrup subjected to adsorption treatment by a third separation membrane, feeding the filtered solution into a second nanofiltration membrane for filtering, and concentrating to obtain the high fructose corn syrup.

The first separation membrane is made of a ceramic material; the average pore diameter of the first separation membrane is in the range of 5 to 500nm, more preferably 20 to 200nm, and most preferably 50 nm.

The operating pressure of the first separation membrane in the filtration is 0.1-0.5 MPa, more preferably 0.2-0.4 MPa, and most preferably 0.3 MPa; the flow rate on the membrane surface is in the range of 1 to 6m/s, and more preferably 2 to 5 m/s.

The first nanofiltration membrane is made of cellulose acetate polymer, polyamide, sulfonated polysulfone, polyethersulfone, polysulfone, polyacrylonitrile, polyester, polyimide, vinyl polymer and the like; the molecular weight cut-off of the first nanofiltration membrane is 150-800 Da, and the filtration pressure of the nanofiltration is 0.5-2.5 MPa.

The third separation membrane is made of a ceramic material; the average pore diameter of the second separation membrane is 5-500 nm, more preferably 20-200 nm, and most preferably 50 nm; the operating pressure of the third separation membrane in the filtration is 0.1-0.5 MPa, more preferably 0.2-0.4 MPa, and most preferably 0.3 MPa; the flow velocity range of the membrane surface is 1-6 m/s, and more preferably 2-5 m/s; the second nanofiltration membrane is made of cellulose acetate polymer, polyamide, sulfonated polysulfone, polyethersulfone, polysulfone, polyacrylonitrile, polyester, polyimide, vinyl polymer and the like; the molecular weight cut-off of the second nanofiltration membrane is 150-800 Da, and the filtration pressure of the nanofiltration is 0.5-2.5 MPa.

In the 4 th step, the fructose adsorbent is loaded with Ca²⁺The addition amount of the D151 adsorption resin is 5-8 wt% of the weight of the isomerized sugar slurry; the desorption process adopts 0.05mol/L diluted ammonia water for elution; the third separation membrane is a microfiltration membrane with the aperture range of 500-800 mu m.

Advantageous effects

The method does not need to add any filter aid and active carbon, and the sugar residue without the filter aid or the active carbon is obtained; and the step of ion exchange is saved, the integrated membrane extraction treatment process is completely adopted, the automation degree is improved, and the cost is saved.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments. It will be understood by those skilled in the art that the following examples are illustrative of the present invention only and should not be taken as limiting the scope of the invention. The examples do not show the specific techniques or conditions, and the techniques or conditions are described in the literature in the art (for example, refer to inorganic membrane separation techniques and applications, chemical industry publishers, 2003, published by Xunan et al) or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about," is not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Unless context or language indicates otherwise, range limitations may be combined and/or interchanged, and such ranges are identified and include all the sub-ranges included herein. Other than in the operating examples, or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified in all instances by the word "about".

The technological process of the invention comprises the steps of firstly treating feed liquid obtained after starch milk is liquefied and saccharified by a ceramic membrane, removing impurities such as enzymolysis residues, protein, most of pigments and the like, and removing salt, pigment and a large amount of protein from the collected clear liquid by a nanofiltration membrane to obtain the starch glucose syrup. In addition, the starch glucose syrup can be further processed deeply, clear liquid collected from a nanofiltration membrane is subjected to isomerase isomerization and then is treated by a set of ceramic membrane system, visible impurities such as pigment, protein and the like generated in the isomerization process are removed, the clear liquid is collected and enters the nanofiltration membrane again to remove inorganic salt, pigment and micromolecular impurities, feed liquid is purified, and the clear liquid is concentrated to obtain a pulp with high fructose content.

The starting material used in the present invention is starch, and the term "starch" refers to any substance consisting of complex polysaccharide carbohydrates of plants, including those having the general formula (C)₆H₁₀O₅) Amylose and amylopectin of x, wherein x may be any number. Sources of starch include grains and/or plant material comprising granular starch. Plant materialPlants that may be obtained include, but are not limited to, wheat, corn, rye, sorghum (milo), rice, millet, barley, triticale, cassava (manioc), potato, sweet potato, sugar beet, sugar cane, and legumes such as soybean and pea. Plant material useful in the present invention includes corn, barley, wheat, rice, sorghum, and combinations of the foregoing. Plant material may include hybrid varieties and genetically modified varieties (e.g., transgenic corn, barley or soybean containing heterologous genes). Any part of the plant may be used to provide a substrate, including but not limited to plant parts such as leaves, stems, husks, hulls, tubers, cobs, grains, and the like. In some embodiments, substantially whole plants can be used, for example, whole corn stover can be used. In some embodiments, whole grain may be used as a source of granular starch. Whole grains include corn, wheat, rye, barley, sorghum, and combinations thereof. In other embodiments, the granular starch may be obtained from fractionated cereal grains, including fiber, endosperm, and/or germ components. In some embodiments, starches from different sources may be mixed together to obtain the feedstock (e.g., corn and milo or corn and barley) used in the methods of the invention.

In some embodiments, the starch is prepared from plant material by grinding or the like. Suitable particle sizes of the starch are obtained, for example, by grinding (hammer or roller), emulsification techniques, rotary pulsation, fractionation, etc.

Next, it is desirable to prepare a slurry for the starch, with the "dry solids content" being the total solids (expressed as%) in the slurry, calculated on a dry weight basis. In some embodiments, the water and granular starch are intermixed to form a slurry, which may include a dry solids content of about 10% to about 55%, alternatively about 25% to about 45%, alternatively about 30% to about 35%.

After the starch slurry is obtained, the starch slurry needs to be liquefied, the liquefaction has the effect of partially hydrolyzing the starch slurry, exposing more undesirable ends which can be acted on by the saccharifying enzyme, and simultaneously, the viscosity is reduced, the fluidity is enhanced, and favorable conditions are provided for the action of the saccharifying enzyme. The liquefaction method of the starch slurry can be divided into an acid method or an enzyme method according to different hydrolysis power, can be divided into a batch type, a semi-continuous type or a continuous type according to different production processes, and can be divided into a pipe type, a tank type or a jet type according to different liquefaction equipment. In practical application, the type methods have cross phenomena, such as an intermittent heating liquefaction method, a continuous injection liquefaction method and the like.

In the liquefaction process, liquefaction may be facilitated by the action of liquefying enzymes, which may be α -amylases, which may optionally break α -1,4 glycosidic linkages in the starch molecule for viscosity reduction of the starch slurry, partial hydrolysis α -amylases (class E.C. 3.2.1.1) refer to enzymes catalyzing the hydrolysis of α -1,4 glycosidic linkages, which have also been described as those that effect either exo-or endo-hydrolysis of 1,4- α -D-glycosidic linkages in polysaccharides containing 1,4- α -linked D-glucose unitsB. lentus) Bacillus licheniformis (B), (B)B licheniformis) Bacillus coagulans bacterium (A), (B) and (C)B.coagulans) And bacillus amyloliquefaciens.

In some embodiments, the alpha-amylase of the invention may be added to a slurry of a comminuted starch substrate (e.g., a comminuted cereal). In some embodiments, the slurry is maintained at a pH in the range of about 4.0 to about 6.5, also about 4.5 to about 6.0, preferably about 5.0 to about 6.0 (e.g., about 5.4 to about 5.8), and the comminuted granular starch in the slurry may be contacted with the enzyme for a period of time in the range of 2 minutes to 8 hours (e.g., 5 minutes to 6 hours, 5 minutes to 4 hours, and 30 minutes to 4 hours) to obtain a liquefied starch. In some embodiments, the temperature ranges from 40 to 115 ℃. In some embodiments, the temperature ranges from 40 to 110 ℃; but may also be 50 to 60 deg.c. The effective dosage of alpha-amylase for use in the methods of the invention will be readily determined by those skilled in the art. The optimal level of starch liquefaction to use depends on processing parameters such as the type of plant material, viscosity, processing time, pH, temperature and ds. As a general guide, in some embodiments, the amount (dose) of alpha-amylase used in the liquefaction process is in the range of about 0.01 to 10kg/T (ton) dry weight of starch, or 0.05 to 5.0kg/T dry weight of starch, or 0.1 to 4.0kg/T dry weight of starch.

After the liquid starch slurry is obtained, the alpha-amylase in the liquid starch slurry can be subjected to enzyme deactivation treatment in a conventional manner, for example, treatment at a high temperature of 100-150 ℃. After the liquefied starch is obtained, it is further hydrolyzed by adding saccharifying enzymes, and in the present invention, "saccharifying enzymes" and "glucoamylases" refer to enzymes of the amyloglucosidase class (e.c. 3.2.1.3, glucoamylases, alpha-1, 4-D-glucan glucohydrolases). These are exo-acting enzymes that release glucose residues from the non-reducing ends of amylose and amylopectin molecules, and these enzymes also hydrolyze the alpha-1, 6 and alpha-1, 3 linkages at a slower rate. The saccharifying enzyme is generally selected from: fungal amylases, beta-amylases, transglucosidases and the like. The saccharification process can be generally continued for 6 to 120 hours, preferably 12 to 72 hours in the present invention, and the normal saccharification temperature is carried out at a temperature of 30 to 65 ℃ and a pH of 4.0 to 5.0.

In addition, other enzymes may optionally be included in the added enzymes during liquefaction and saccharification. Other enzymes may include, but are not limited to: cellulase, hemicellulase, xylanase, protease, phytase, pullulanase, p-amylase, lipase, cutinase, pectinase, D-glucanase, p-glucosidase, galactosidase, esterase and cyclodextrin transglycosyltransferase.

After the saccharified solution is obtained, it is required to perform a filtration treatment using a separation membrane, which functions to remove impurities such as impurities, particulate matters, colloids, and the like in the liquefied solution and the saccharified solution, and in addition, the separation membrane can remove macromolecular proteins, which is advantageous in increasing the yield of the subsequent steps and reducing the operation time. The separation membrane mentioned here may be a microfiltration membrane or a microfiltration membrane, the microfiltration membrane used in the present invention is a membrane having an average pore diameter of 0.01 μm to 5mm, and the ultrafiltration membrane used in the present invention is a membrane having a molecular weight cut-off of 1000 to 200000, and here, since the pore diameter of the ultrafiltration membrane is too small to measure the pore diameter on the membrane surface by an electron microscope or the like, a value called the molecular weight cut-off is used as an index of the pore diameter instead of the average pore diameter. With respect to molecular weight cut-off, as is well known to those skilled in the art: "A curve obtained by plotting the solute molecular weight on the horizontal axis and the rejection on the vertical axis is referred to as a molecular weight cut-off curve. The molecular weight having a rejection of 90% is also referred to as a molecular weight cut-off of the membrane, which is an index representing the membrane performance of the ultrafiltration membrane and is well known to those skilled in the art. The material of the separation membrane is not particularly limited as long as the object of the present invention can be achieved by removing the water-soluble polymer and the colloidal component, and examples thereof include: cellulose, cellulose ester, polysulfone, polyethersulfone, polyvinyl chloride, chloropropylene, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, or other organic materials, or stainless steel or other metals, or ceramics or other inorganic materials. The material of the microfiltration membrane or the ultrafiltration membrane can be properly selected in consideration of the property of hydrolysate or the running cost, and in consideration of the easiness in operation, an inorganic material such as a ceramic membrane is preferred, and the ceramic membrane has good high-temperature resistance. The material of the porous membrane constituting the ceramic separation membrane can be appropriately selected from conventionally known ceramic materials. For example, oxide-based materials such as alumina, zirconia, magnesia, silica, titania, ceria, yttria, and barium titanate; composite oxide materials such as cordierite, mullite, forsterite, steatite, sialon, zircon, ferrite and the like; nitride materials such as silicon nitride and aluminum nitride; carbide-based materials such as silicon carbide; hydroxide materials such as hydroxyapatite; elemental materials such as carbon and silicon; or an inorganic composite material containing two or more of them. Natural minerals (clay, clay minerals, earthenware slag, silica sand, pottery stone, feldspar, white sand) or blast furnace slag, fly ash, etc. may also be used. Among these, 1 or 2 or more kinds selected from alumina, zirconia, titania, magnesia and silica are preferable, and ceramic powder mainly composed of alumina, zirconia or titania is more preferable. Here, the term "mainly" means that 50wt% or more (preferably 75wt% or more, more preferably 80wt% to 100 wt%) of the entire ceramic powder is alumina or silica. For example, among porous materials, alumina is inexpensive and excellent in handling properties. Further, since a porous structure having pore diameters suitable for liquid separation can be easily formed, a ceramic separation membrane having excellent liquid permeability can be easily produced. Among the above aluminas, alpha-alumina is particularly preferably used. Alpha-alumina has the characteristics of being chemically stable and having high melting point and mechanical strength. Therefore, by using α -alumina, a ceramic separation membrane that can be utilized in a wide range of applications (e.g., industrial fields) can be manufactured.

In one embodiment of the present invention, the average pore diameter of the separation membrane is preferably 5 to 500nm, more preferably 20 to 200nm, and still more preferably 50 nm. When glucose syrup needs to be isomerized to prepare high fructose content fructose-glucose syrup, in the pore size range, the fructose content of the finally obtained fructose-glucose syrup can be ensured to be in a relatively high range, probably because the pore size is related to the activity of impurity components in the permeate on isomerization enzymes. In addition, the selection of the aperture of the ultrafiltration membrane directly influences the effect of filtering, deslagging and decolorizing of the feed liquid, the filtering precision is lowered due to the overlarge aperture, impurities in the feed liquid permeate through the ceramic membrane, the processing load of a decolorizing membrane (nanofiltration membrane) is increased, and the purity of subsequent products is also influenced; too small pore size results in too large filtration resistance, too low membrane flux, too high investment in ceramic membrane filtration equipment, increased energy consumption, and also retention of part of the active ingredients, resulting in a decrease in the final yield.

In the conventional process, the light transmittance after treatment is generally about 90 percent and impurities are not completely removed by using a plate-frame filtration or vacuum drum filtration system. The microfiltration membrane or ultrafiltration membrane is used for replacing a traditional filtering system, so that the quality of feed liquid can be greatly improved, the yield is improved to about 98 percent, the light transmission can reach more than 97 percent, SS is removed to 0.5ppm, the automation efficiency is improved, and the subsequent treatment pressure is reduced.

In one embodiment of the invention, the separation membrane is operated at a pressure in the range of 0.1 to 0.5MPa, preferably 0.2 to 0.4MPa, most preferably 0.3 MPa. In this pressure range, the fructose content of the high fructose syrup obtained by isomerization to fructose can be increased. In addition, when the operation pressure is too high, the membrane pollution is increased, and the membrane flux is reduced sharply; too low an operating pressure will result in too little driving force for the filtration process, resulting in too low a membrane flux.

In one embodiment of the invention, the membrane surface flow rate of the ceramic membrane filtration is 1-6 m/s, more preferably 2-5 m/s, and most preferably the membrane surface flow rate is 4 m/s. If the flow velocity of the membrane surface in the filtering process is too high, the membrane surface cannot form better filter cake layers, and the filter cake layers can play a role in further intercepting impurities, so that fine impurities can penetrate through the filter membrane; if the flow rate on the membrane surface is too low, the filtration flux is too low, and the concentration factor cannot be further increased, resulting in a low final yield. In the technical scheme of the invention, in the ceramic membrane concentration, the concentration multiple is preferably 8-20 times, the optimal concentration multiple is 15 times, and the light transmittance of the feed liquid subjected to ultrafiltration treatment is more than 96%.

After the saccharified liquid is filtered by the separation membrane, the permeate of the separation membrane is decolorized and desalted by a nanofiltration membrane, so that some salt, pigment and a large amount of protein in the saccharified liquid can be trapped. Nanofiltration membranes are herein defined as "pressure driven membranes that block particles smaller than 2nm and dissolved macromolecules". Effective nanofiltration membranes suitable for use in the present invention are preferably such membranes: the membrane has an electric charge on the surface thereof, and thus exhibits improved separation efficiency by a combination of fine pore separation (particle size separation) and electrostatic separation benefiting from the electric charge on the surface thereof, while being a nanofiltration membrane subjected to a high temperature resistant treatment. Therefore, it is necessary to use a nanofiltration membrane capable of removing a high molecular substance by separation while separating a target separation product from other ions having different charge characteristics by means of electric charge. As a material of the nanofiltration membrane used in the present invention, a high molecular material such as a cellulose acetate polymer, polyamide, sulfonated polysulfone, polyethersulfone, polysulfone, polyacrylonitrile, polyester, polyimide, vinyl polymer, or the like, which has been subjected to a high temperature resistance treatment, can be used. The film is not limited to one composed of only one material, and may be a film containing a plurality of the materials. With respect to the membrane structure, the membrane may be an asymmetric membrane having a dense layer on at least one side of the membrane and having micropores with pore diameters gradually increasing from the dense layer toward the inside of the membrane or the other side; or a composite membrane having a very thin functional layer of another material on the dense layer of the asymmetric membrane. The membrane material is more preferably an organic polymer material with better high-temperature resistance, such as polysulfone, polyether sulfone and the like, and can directly treat feed liquid at high temperature.

In the traditional sugar manufacturing process, activated carbon is required to be used for decolorization and adsorption treatment, and desalination is carried out by means of ion exchange resin, but the method is complicated in operation and long in working procedure. The nanofiltration membrane is adopted to carry out decoloring and desalting treatment on the ultrafiltration membrane penetrating fluid, which is obviously superior to the traditional effects of activated carbon, ion exchange desalting and decoloring; because the decoloration liquid does not need to be decolored by active carbon, the problems of large consumption of active carbon, low product yield caused by the adsorption of the active carbon on products, low product purity caused by the extremely easy carbon leakage in the decoloration process of the active carbon, high cost of the active carbon, environmental pollution and the like caused by the use of the active carbon are avoided, and the decoloration and the desalination are carried out in the same step, so that the method has the advantage of simple steps. The transmittance of the nanofiltration membrane decolorant can reach more than 99 percent. Particularly, when the glucose syrup needs to be subjected to isomerization deep processing to prepare the fructose-glucose syrup, the nanofiltration membrane can also play a role in removing calcium ions, so that the inhibition effect of the calcium ions on the isomerization reaction is avoided.

The molecular weight cut-off of the membrane is 150-800 Da, more preferably 300Da, the membrane filtration pressure is 0.5-2.5 MPa, more preferably 1.5MPa, and the filtration temperature is 60-80 ℃; with this type of nanofiltration, the sugars are maximally permeated and inorganic salts and other impurities are trapped.

When the glucose syrup needs to be isomerized to prepare high fructose content fructose-glucose syrup, the adopted isomerase can be common glucose isomerase Streptomyces rubiginosus or Streptomyces murinus enzyme), and the isomerase can be immobilized on a carrier, for example, immobilized glucose isomerase prepared by adsorbing glucose isomerase onto ion exchange resin or embedding glucose isomerase in gelatin. The pH and temperature of the isomerization reaction can be carried out by conventional means without particular limitation, and preferably ranges from pH7.0 to 9.0 and the temperature is between 60 and 90 ℃.

After the isomerized syrup is obtained, a fructose adsorbent (loaded with Ca) is added into the isomerized syrup²⁺The D151 adsorption resin) with the addition amount being 5-8 wt% of the weight of the isomerized sugar slurry, filtering the adsorbent with a microfiltration membrane of 500-800 mu m after adsorption saturation, eluting with 0.05mol/L dilute ammonia water, and sending the eluent to subsequent membrane filtration treatment. Because the fructose adsorbent has difference in adsorption rate to protein and fructose, when the fructose adsorbent is dispersed in isomerized syrup, fructose can be preferentially adsorbed on the adsorbent, the fructose/protein component ratio in eluent can be obviously improved after elution, and during ultrafiltration, on one hand, the problem of high fructose retention rate caused by protein gelation is avoided, and on the other hand, membrane pollution is avoided.

The desorption liquid needs to be filtered through a separation membrane, the separation membrane is similar to the separation membrane for treating the saccharification liquid, an ultrafiltration membrane is preferably adopted, the material is a ceramic material, the aim of the separation membrane is to remove impurities such as pigments, proteins and most of salts generated in the isomerization process, the transmittance and the clarity of the feed liquid are improved, the impurities brought in the isomerization step are removed, the pressure of a subsequent nanofiltration membrane is reduced, and the treatment efficiency of the subsequent nanofiltration membrane is improved. The average pore diameter of the micro-filtration membrane or the ultrafiltration membrane is 5-20 nm, and preferably, the pore diameter of the ceramic membrane is 20 nm. The operating pressure of the ceramic membrane is 0.1-0.5 MPa, and preferably 0.3 MPa. In the technical scheme of the invention, the flow rate of the membrane surface filtered by the ceramic membrane is 2-5 m/s, and preferably the flow rate of the membrane surface filtered by the ceramic membrane is 4 m/s. In the ceramic membrane concentration, the concentration multiple is preferably 15-30 times, and the optimal concentration multiple is 25 times, and the step can improve the light transmission of the feed liquid to more than 98%.

After the permeate of the ultrafiltration membrane is obtained, the permeate can be filtered by a nanofiltration membrane, divalent salt, residual pigment and some small molecular protein impurities introduced in the isomerization step are removed, the quality of feed liquid is improved, and the material and the operating parameters of the nanofiltration membrane are similar to those of the nanofiltration process of the glucose syrup. The original process of the step is to add ion exchange to the activated carbon for treatment, and replace the activated carbon with a nanofiltration membrane, so that the treatment efficiency is improved, the quality of feed liquid is improved, and the production cost is reduced. The preferable molecular weight cut-off of the nanofiltration membrane adopted in the step is 150Da to 800Da, the membrane material can be organic polymer materials such as polysulfone and polyether sulfone which are subjected to high temperature resistance treatment, the operation pressure is 1.5 to 2.5MPa, and the circulation flow is 2.0 to 3.0m for carrying out the cultivation/h. In one embodiment of the invention, when the isomerization liquid is filtered, 1-5 per mill of active carbon powder is preferably added into the liquid to be filtered, the active carbon powder has the function of adsorbing some impurities, the concentration multiple of the nanofiltration membrane can be improved, and the yield of the high fructose corn syrup is further improved. The term "concentration factor" in the present invention means the ratio of the volume of the feed liquid to be filtered to the system of the concentrated liquid after the end of the concentration filtration.

After nanofiltration permeate is obtained, triple-effect evaporation concentration is preferably adopted during concentration, extraction concentration equipment is adopted, the shell and tube circulating external heating working principle is adopted, the physical heating time is short, the evaporation speed is high, the concentration ratio is large, the original effect of materials is effectively maintained, the energy-saving effect is obvious, the evaporation capacity is saved by about 70% compared with a single-effect evaporator, and the sugar concentration is improved to about 70% by triple-effect evaporation.

Since a certain amount of sugar still exists in the concentrated solution or the filter cake after the ceramic membrane filtration, in order to improve the yield, according to an improved embodiment of the invention, water is added into the concentrated solution for dialysis to obtain a dialyzate, so that more effective substances in the filter cake can be eluted, and the yield of fructose and glucose can be improved more, preferably, the water addition amount is 5-30% of the original liquid amount, and more preferably, 10% of the original liquid amount.

In the invention, the content of glucose and fructose in the syrup is measured by an HPLC method.

The preparation process of the starch emulsifying and saccharifying liquid adopted in the following examples is as follows: preparing starch slurry by adopting corn starch (the content is about 68wt percent) and water with the weight being 4 times of that of the corn starch, adding alpha-amylase with the weight being 0.2 percent of the weight of the corn starch, carrying out liquefaction reaction for 3 hours at 60 ℃ to obtain liquefied slurry, heating, boiling and inactivating the enzyme, adding beta-amylase with the weight being 0.2 percent of the weight of the corn starch into the feed liquid, adjusting the pH of the feed liquid to be 6.0-6.2, carrying out saccharification reaction for 72 hours at 60 ℃, heating to 110 ℃ and inactivating the enzyme to obtain saccharified liquid.

Comparative example 1

Removing impurities and filtering 100Kg of starch saccharification liquid through a ceramic membrane, wherein the temperature of the material liquid is 60 ℃, the material of the ceramic membrane is zirconia, the average pore diameter is 20nm, the filtering pressure is 0.3MPa, the flow rate of the membrane surface is 2m/s, the material liquid is concentrated by 15 times to obtain ceramic membrane penetrating liquid, dialyzing by adding dialysis water with 5 percent of the amount of the material liquid, the light transmittance of the material liquid is 98 percent, adding 5Kg of active carbon into the ceramic membrane penetrating liquid, uniformly stirring, heating to 70 ℃, keeping for 1 hour for decolorization, cooling the decolorized liquid, conveying the cooled decolorized liquid into a 732 cation exchange resin column for desalination, and concentrating and drying to obtain 8.2 Kg of starch sugar.