A preparation method of maltose syrup and application thereof

Abstract

The invention belongs to the technical field of maltose, and particularly relates to a preparation method of maltose syrup and application thereof. The preparation method of maltose syrup comprises the following steps: S1, adding water to corn starch to obtain a mixture, and extruding to obtain substance one; S2, adding water to substance one to adjust the mass fraction of substance one to 25%-35%, the pH to 5.5-6.5, adding high temperature resistant α-amylase and anhydrous calcium chloride, liquefying at 90-100°C for 20-30min, cooling to 65-75°C, adding medium temperature α-amylase, continuing liquefaction for 15-20min, and obtaining substance two; S3, sending substance two into a saccharification tank, adjusting the pH to 5.0-5.5, the temperature to 50-60°C, adding modified β-amylase, isoamylase and sodium thiosulfate, saccharifying for 3-6h, heating to 55-65°C, adding pullulanase, saccharifying for 5-10h, and obtaining substance three; S4, treating substance three to inactivate enzymes, filtering and decolorizing for a second time, performing ion exchange, collecting the ion exchange liquid and vacuum concentrating, and obtaining the substance three. The preparation method of the maltose syrup of the invention is simple to operate, and the prepared maltose syrup has high maltose content and good stability.

Description

Technical Field

[0001] The invention belongs to the technical field of maltose, and particularly relates to a preparation method of maltose syrup and application thereof. Background Art

[0002] Maltose has low sweetness (only 30%-40% of sucrose), good antiseptic properties, high thermal stability, and low hygroscopicity, and is widely used in food and medicine. Maltose syrup is a syrup with a high maltose content (≥50%). According to the maltose content, it can be divided into ordinary maltose syrup (maltose content below 60%), high maltose syrup (maltose content of 60%~70%), and ultra-high maltose syrup (maltose content ≥70%). With its colorless and transparent appearance, mild taste with low sweetness, high sugar boiling temperature stability, low hygroscopicity, and excellent anti-crystallization performance, maltose syrup has become an important product leading the renewal of the candy industry. It has been widely used in many food fields such as candy, preserves, and fruit and vegetable juice beverages, bringing a double improvement in taste and quality to these products.

[0003] However, the current method for producing maltose syrup still has problems such as incomplete enzymatic decomposition and high glucose content after starch liquefaction, which will lead to low maltose content in maltose syrup, affecting its quality, and incomplete enzymatic decomposition during the liquefaction and saccharification process, resulting in low syrup yield, affecting economic benefits. Therefore, it is necessary to develop a method for preparing maltose syrup, reduce the glucose content in maltose syrup, increase the maltose content, and have a higher syrup yield, which is suitable for large-scale production and can be widely used in food, medicine and other fields. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing maltose syrup and application thereof, which can reduce the glucose content in maltose syrup, greatly increase the maltose content, improve the purity of maltose syrup, and at the same time has a higher syrup yield, is suitable for large-scale production, and can be widely used in the fields of food, medicine, etc.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The preparation method of the maltose syrup comprises the following steps:

[0007] S1. Add water to corn starch to obtain a mixture, and extrude to obtain substance 1;

[0008] S2, add water to substance 1 to adjust the mass fraction of substance 1 to 25%-35%, the pH to 5.5-6.5, add high temperature resistant α-amylase and anhydrous calcium chloride, liquefy at 90-100°C for 20-30min, cool to 65-75°C, add medium temperature α-amylase, continue liquefaction for 15-20min, and obtain substance 2;

[0009] S3, sending substance 2 into a saccharification tank, adjusting the pH to 5.0-5.5, the temperature to 50-60°C, adding modified β-amylase, isoamylase and sodium thiosulfate, saccharifying for 3-6 hours, raising the temperature to 55-65°C, adding pullulanase, and saccharifying for 5-10 hours to obtain substance 3;

[0010] S4, treating the substance with triple enzyme inactivation, filtering and decolorizing for a second time, and performing ion exchange, collecting the ion exchange liquid and concentrating it under vacuum to obtain the product.

[0011] Preferably, the water content of the mixture is 15% to 25%.

[0012] Preferably, the specific conditions of the extrusion enzymolysis in the extruder are: the screw speed is 150-200 r / min, and the barrel temperature is 50-60°C.

[0013] The inventors found that, through the extrusion technology under specific conditions, the liquefaction efficiency can be improved while shortening the liquefaction time, so that the starch can be liquefied and hydrolyzed in a short time, providing a substrate that is easier to hydrolyze for the subsequent saccharification process. This may be because through the specific extruder conditions, the corn starch undergoes high temperature and high shear in the extruder, undergoes obvious gelatinization and degradation, increases the content of amylose, and reduces the content of branched starch, thereby facilitating the subsequent α-amylase to decompose the corn starch, and can improve the degree of degradation, not only reducing the viscosity of the starch mixture, which is conducive to the liquefaction process, but also conducive to the subsequent saccharification enzyme to generate maltose, thereby shortening the saccharification time and improving the saccharification efficiency. Moreover, the starch granules after extrusion are uniform in size, irregular in shape and uneven on the surface, which increases the contact area with the amylase and further improves the liquefaction efficiency.

[0014] Preferably, the enzyme activity of the thermostable α-amylase is 100,000-200,000 U / g.

[0015] In some preferred embodiments, the thermostable α-amylase has an enzyme activity of 150,000 U / g and is purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd.

[0016] Preferably, the addition amount of the thermostable α-amylase is 5-15 U / g corn starch.

[0017] Preferably, the amount of anhydrous calcium chloride added is 0.05% to 0.2% of the mass of the substance.

[0018] Preferably, the mesophilic α-amylase has an activity of 8000-15000 U / g.

[0019] In some preferred embodiments, the medium-temperature α-amylase has an enzyme activity of 10,000 U / g and is purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd.

[0020] Preferably, the addition amount of the medium-temperature α-amylase is 15-25 U / g corn starch.

[0021] The inventors have found through a large number of experiments that by first using a high-temperature resistant α-amylase for liquefaction and then adding a medium-temperature α-amylase for secondary liquefaction, the content of maltose in maltose syrup can be increased and the cost can be reduced. This may be because through step-by-step liquefaction, starch can be further hydrolyzed under milder conditions to generate more soluble dextrins and oligosaccharides. The step-by-step liquefaction process not only helps to liquefy starch more thoroughly, reduce the residue of unliquefied starch, and improve the purity of maltose syrup, but also can control the length of starch chains within a reasonable range, thereby reducing the content of glucose and increasing the content of maltose. The cost of high-temperature resistant α-amylase may be high, but through the synergistic effect with medium-temperature α-amylase, its dosage can be reduced, while the liquefaction efficiency can be improved, thereby reducing production costs to a certain extent. In addition, adding a certain amount of anhydrous calcium chloride can not only accelerate the dissolution and hydration of starch granules in substance 1, making starch molecules more easily decomposed by water, thereby accelerating the liquefaction rate, but also adjust the pH value during the starch liquefaction process. A stable pH environment helps amylase maintain its activity, thereby further improving the liquefaction efficiency. However, the temperature should not be too high during the secondary liquefaction. Too high a temperature will cause the corn starch granules to swell rapidly, wrapping the action sites of the enzyme, inhibiting the activity of the enzyme, affecting the liquefaction effect, and the swollen starch is not completely liquefied, affecting the syrup yield.

[0022] The preparation method of the modified β-amylase comprises the following steps: placing the β-amylase and the modifier in buffer A respectively, stirring evenly, mixing at a molar ratio at 55-60° C. for 10 minutes, adding ammonium sulfate with a mass concentration of 70% until a precipitate is completely precipitated, centrifuging at 0-4° C. to obtain the precipitate, dissolving the precipitate in buffer B, removing the ammonium sulfate by an ultrafiltration membrane for 4 hours, separating and purifying by using a protein purifier combined with an anion exchange chromatography column and a gel column, and freeze-drying in a vacuum freeze dryer to obtain the modified β-amylase.

[0023] Preferably, the enzymatic activity of the β-amylase is 600,000-800,000 U / g.

[0024] In some preferred embodiments, the β-amylase has an enzyme activity of 700,000 U / g and is purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd.

[0025] Preferably, the modifier is methyl polyethylene glycol maleimide, and the molecular weight is 1000-5000 Da; more preferably, it is 3400 Da.

[0026] Preferably, methyl polyethylene glycol maleimide, with a molecular weight of 3400 Da, is purchased from Kaixin Biotechnology.

[0027] Preferably, the mass ratio of the β-amylase to the modifier is 1:(3-5).

[0028] In order to increase the content of maltose, α-amylase hydrolyzes starch into molecules of appropriate chain length, and β-amylase is generally used for further saccharification. In the saccharification process, β-amylase is a commonly used active enzyme, but it is easily affected by the environment during the saccharification process and is not suitable for the production of high maltose syrup. The inventors found that by selecting methyl polyethylene glycol maleimide of a specific molecular weight as a modifier and controlling the molar ratio of β-amylase and the modifier, the purity of maltose in maltose syrup can be improved while improving the saccharification efficiency. This may be because the polyethylene glycol and maleimide groups of methyl polyethylene glycol maleimide can not only form a protective layer on the surface of β-amylase, blocking the direct effects of adverse factors in the external environment (such as high temperature, extreme pH value, etc.) on the enzyme molecules, thereby improving the stability and resistance of the enzyme, but also react with β-amylase to form a stable thioether bond. This covalent bonding further enhances the connection strength between PEG and the enzyme molecule, which helps to maintain the structural stability of the enzyme. Therefore, the thermal stability and pH stability of β-amylase are improved, and the activation effect is significant during the saccharification process, which not only improves the saccharification efficiency and reduces the cost, but also increases the maltose content. While methyl polyethylene glycol maleimide of a specific molecular weight can provide better spatial shielding effect and stability enhancement effect, but too large a molecular weight may increase the volume and steric hindrance of the enzyme molecule, affecting the activity of the enzyme. Excessive methyl polyethylene glycol maleimide solution may lead to non-specific binding with non-target amino acid residues in the enzyme molecule, thereby affecting the catalytic activity and stability of the enzyme. However, the modified β-amylase still cannot process the branching points of starch (α-1,6-glycosidic bonds), affecting the maltose content, and will also leave more β-limit dextrin, reducing the maltose content.

[0029] Preferably, the buffer A is a disodium hydrogen phosphate-citric acid buffer with a pH of 5 to 6.

[0030] In some preferred embodiments, the buffer A, sodium dihydrogen phosphate-citrate buffer with a pH of 5.8, is purchased from Shanghai Qiming Biotechnology Co., Ltd.

[0031] Preferably, the buffer solution B is a sodium chloride solution with a concentration of 1 mol / L.

[0032] Preferably, the ultrafiltration membrane can retain a molecular weight of ≤1 kDa.

[0033] In some preferred embodiments, the 1 kDa ultrafiltration membrane is purchased from Shanghai Weixi Biotechnology Co., Ltd.

[0034] Preferably, the added amount of the modified β-amylase is 0.005-0.01 mg / g corn starch.

[0035] Preferably, the enzyme activity of the isoamylase is 8000-15000 U / g.

[0036] In some preferred embodiments, the isoamylase has an enzyme activity of 10,000 U / g and is purchased from Hubei Wei's Chemical Reagent Co., Ltd.

[0037] Preferably, the addition amount of the isoamylase is 30-50 U / g corn starch.

[0038] The inventors found that by using modified β-amylase and isoamylase to saccharify substance 2, the yield of maltose can be greatly improved, while the saccharification process can be accelerated, the saccharification time can be shortened, and the production of excessive glucose and other by-products can be avoided. This may be because isoamylase and modified β-amylase not only have a synergistic effect, but isoamylase will first decompose the side chains of amylopectin to convert it into amylose, so that the modified β-amylase can act more efficiently on these amylose and decompose them into oligosaccharides such as maltose. Moreover, they are also complementary. The modified β-amylase mainly acts on the α-1,4-glycosidic bonds of the starch chain to produce oligosaccharides such as maltose, but cannot directly act on the α-1,6-glycosidic bonds of amylopectin. Isoamylase specifically acts on the α-1,6-glycosidic bonds of amylopectin, decomposing it into amylose, making the starch chain easier to be further hydrolyzed by the modified β-amylase. The two modes of action can not only decompose starch more comprehensively, but also increase the yield of maltose. However, isoamylase mainly removes the larger branches of amylopectin, and has limited effect on the decomposition of smaller branches and the increase of maltose content.

[0039] Preferably, the amount of sodium thiosulfate added is 0.03% to 0.1% of the mass of substance 2.

[0040] Preferably, the pullulanase has an enzymatic activity of 1000-3000 U / g.

[0041] In some preferred embodiments, the pullulanase has an enzyme activity of 2000 U / g and is purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd.

[0042] Preferably, the added amount of the pullulanase is 40-80 U / g corn starch.

[0043] The inventor has found through multiple tests that modified beta-amylase, isoamylase and then adding an appropriate amount of pullulanase can further increase the maltose content. This may be because isoamylase mainly removes the larger branches of amylopectin, and pullulanase can further decompose the smaller branched structure, and when both act simultaneously, by removing the branching point of amylopectin, not only starch molecules can be more comprehensively decomposed during saccharification, thereby improving saccharification efficiency and product quality, but also helps to open the branched structure of starch, making it easier for modified beta-amylase to act on starch molecules and produce maltose, and increasing maltose content. In addition, by heating up after saccharification for a period of time and then adding pullulanase, the competitive relationship between enzymes for space utilization can be avoided to a certain extent, which is conducive to the generation and accumulation of maltose.

[0044] Preferably, the enzyme inactivation treatment conditions are: temperature 100° C., insulation time 10 min.

[0045] The specific steps of the secondary filtration and decolorization are: using diatomaceous earth filter aid and activated carbon for decolorization in sequence, and filtering after decolorization to remove impurities and starch residues and other substances.

[0046] Preferably, the median mesh size of the diatomaceous earth filter aid is 400-600 mesh, and the bulk density is ≤0.65 g / cm3.

[0047] In some preferred embodiments, the diatomaceous earth filter aid has a median mesh size of 500 meshes and a bulk density of ≤0.65 g / cm3, and is purchased from Senda Diatomaceous Earth Materials Co., Ltd.

[0048] Preferably, the activated carbon is coal-based activated carbon.

[0049] Preferably, the particle size of the coal-based activated carbon is 8-20 mesh, and the phenol adsorption capacity is ≥160 mg / g.

[0050] In some preferred embodiments, the coal-based activated carbon is purchased from Zhejiang Zhelang Activated Carbon Co., Ltd.

[0051] The specific steps of the ion exchange are: passing the syrup through a strongly acidic cation resin, a strongly basic anion resin, and a strongly acidic cation resin in sequence.

[0052] In some preferred embodiments, the strong acid cationic resin is purchased from Hebei Lanyin Technology Co., Ltd., D001x7 cationic resin.

[0053] In some preferred embodiments, the strong alkaline anion resin is purchased from Jiangsu Linhai Resin Technology Co., Ltd., D202 anion resin.

[0054] The maltose syrup is applied in the food field and can be used to prepare maltose, sweeteners, leavening agents, etc.

[0055] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0056] 1. The present invention provides a method for preparing maltose syrup and its application. The method can reduce the glucose content in maltose syrup, greatly increase the maltose content, improve the purity of maltose syrup, and at the same time has a high syrup yield, is suitable for large-scale production, and can be widely used in the fields of food, medicine, etc.

[0057] 2. The present invention uses extrusion technology under specific conditions to shorten the liquefaction time and improve the liquefaction efficiency, thereby liquefying and hydrolyzing the starch in a short time, providing a substrate that is easier to hydrolyze for the subsequent saccharification process.

[0058] 3. The present invention can increase the content of maltose in maltose syrup and reduce costs by first using high-temperature α-amylase for liquefaction and then adding medium-temperature α-amylase for secondary liquefaction.

[0059] 4. The present invention selects methyl polyethylene glycol maleimide of a specific molecular weight as a modifier and controls the molar ratio of β-amylase and the modifier, thereby improving the saccharification efficiency and the purity of maltose in maltose syrup.

[0060] 5. The present invention can greatly improve the yield of maltose by selecting modified β-amylase and isoamylase to saccharify substance 2, while accelerating the saccharification process, shortening the saccharification time, and avoiding the production of excessive glucose and other by-products.

[0061] 6. The present invention uses modified β-amylase and isoamylase and then adds an appropriate amount of pullulanase to further increase the maltose content. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] The raw materials used in the present invention are all commercially available, specifically:

[0064] Corn starch, starch content 70%, was purchased from Henan Fengwei Biotechnology Co., Ltd.

[0065] Thermostable α-amylase, with an enzyme activity of 150,000 U / g; mesophilic α-amylase, with an enzyme activity of 10,000 U / g; and β-amylase, with an enzyme activity of 700,000 U / g were all purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd.

[0066] Methyl polyethylene glycol maleimide, molecular weight 3400Da, was purchased from Kaixin Biotechnology.

[0067] Buffer A, sodium dihydrogen phosphate-citrate buffer, pH 5.8, was purchased from Shanghai Qiming Biotechnology Co., Ltd.

[0068] Buffer B is a 1 mol / L sodium chloride solution.

[0069] 1 kDa ultrafiltration membrane was purchased from Shanghai Weixi Biotechnology Co., Ltd.

[0070] Isoamylase, with an enzyme activity of 10000 U / g, was purchased from Hubei Weishi Chemical Reagent Co., Ltd.

[0071] Pullulanase, with an enzyme activity of 2000 U / g, was purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd.

[0072] The diatomite filter aid has a median mesh size of 500 meshes and a bulk density of ≤0.65 g / cm3, and is purchased from Senda Diatomite Materials Co., Ltd.

[0073] The particle size of coal-based activated carbon was 8-20 mesh, and the phenol adsorption capacity was ≥160 mg / g, which was purchased from Zhejiang Zhelang Activated Carbon Co., Ltd.

[0074] Strong acid cationic resin was purchased from Hebei Lanyin Technology Co., Ltd., D001x7 cationic resin.

[0075] Strong alkaline anion resin was purchased from Jiangsu Linhai Resin Technology Co., Ltd., D202 anion resin.

[0076] Example 1

[0077] This embodiment provides a method for preparing maltose syrup and application thereof, the steps are:

[0078] S1. Add water to corn starch to obtain a mixture, and extrude to obtain substance 1;

[0079] S2, add water to substance 1 to adjust the mass fraction of substance 1 to 30%, adjust the pH to 6.0, add high temperature resistant α-amylase and anhydrous calcium chloride, liquefy at 95°C for 25 minutes, cool to 70°C, add medium temperature α-amylase, and continue liquefaction for 18 minutes to obtain substance 2;

[0080] S3, sending substance 2 into a saccharification tank, adjusting the pH to 5.5, the temperature to 55°C, adding modified β-amylase, isoamylase and sodium thiosulfate, saccharifying for 5 hours, raising the temperature to 60°C, adding pullulanase, and saccharifying for 8 hours to obtain substance 3;

[0081] S4, treating the substance with triple enzyme inactivation, filtering and decolorizing for a second time, and performing ion exchange, collecting the ion exchange liquid and concentrating it under vacuum to obtain the product.

[0082] The water content of the mixture is 20%.

[0083] The specific conditions of the extrusion enzymolysis in the extruder are: the screw speed is 180r / min, and the barrel temperature is 55°C.

[0084] The addition amount of the thermostable α-amylase is 10 U / g corn starch.

[0085] The amount of anhydrous calcium chloride added is 0.1% of the mass of the substance.

[0086] The addition amount of the medium-temperature α-amylase is 20 U / g corn starch.

[0087] The preparation method of the modified β-amylase comprises the following steps: placing the β-amylase and the modifier in buffer A respectively, stirring evenly, mixing at a molar ratio at 58° C. for 10 minutes, adding ammonium sulfate with a mass concentration of 70% until a precipitate is completely precipitated, centrifuging at 4° C. to obtain the precipitate, dissolving the precipitate in buffer B, removing the ammonium sulfate by an ultrafiltration membrane for 4 hours, separating and purifying by using a protein separator combined with an anion exchange chromatography column and a gel column, and freeze-drying in a vacuum freeze dryer to obtain the modified β-amylase.

[0088] The modifier is methyl polyethylene glycol maleimide.

[0089] The mass ratio of the β-amylase to the modifier is 1:4.

[0090] The added amount of the modified β-amylase is 0.008 mg / g corn starch.

[0091] The specific steps of separation and purification are: introducing the solution from which ammonium sulfate has been removed into a protein separator to generate a large number of bubbles, which rise in the solution and adsorb enzyme molecules to form foam, which gradually gathers on the water surface, collecting the foam and passing it through a GE MonoQ anion exchange chromatography column, eluting and collecting the enzyme molecules on the chromatography column, and then continuing to pass it through a Superdex 75 gel column to elute and collect the enzyme molecules on the gel column.

[0092] The addition amount of the isoamylase is 40 U / g corn starch.

[0093] The amount of sodium thiosulfate added is 0.05% of the mass of substance 2.

[0094] The added amount of the pullulanase is 60 U / g corn starch.

[0095] The enzyme inactivation treatment conditions are: temperature 100° C., insulation time 10 min.

[0096] The specific steps of the secondary filtration and decolorization are: using diatomaceous earth filter aid and activated carbon for decolorization in sequence, and filtering after decolorization to remove impurities and starch residues and other substances.

[0097] The specific steps of the ion exchange are: passing the syrup through a strongly acidic cation resin, a strongly basic anion resin, and a strongly acidic cation resin in sequence.

[0098] Example 2

[0099] The difference between this embodiment and embodiment 1 is: S2, water is added to substance one to adjust the mass fraction of substance one to 30%, the pH is adjusted to 6.0, high temperature resistant α-amylase and anhydrous calcium chloride are added, and after liquefaction at 95°C for 25 minutes, the temperature is lowered to 75°C, medium temperature α-amylase is added, and liquefaction is continued for 15 minutes to obtain substance two.

[0100] Example 3

[0101] The difference between this embodiment and embodiment 1 is: S3, sending substance 2 into a saccharification tank, adjusting the pH to 5.0, the temperature to 50°C, adding modified β-amylase, isoamylase and sodium thiosulfate, saccharifying for 5 hours, raising the temperature to 65°C, adding pullulanase, and saccharifying for 5 hours to obtain substance 3.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that the corn starch is not subjected to extrusion treatment.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 1 is: S2, water is added to substance one to adjust the mass fraction of substance one to 30%, the pH is adjusted to 6.0, high temperature resistant α-amylase is added, and after liquefaction at 95°C for 25 minutes, the temperature is lowered to 70°C, medium temperature α-amylase is added, and liquefaction is continued for 18 minutes to obtain substance two.

[0106] Comparative Example 3

[0107] The difference between this comparative example and Example 1 is: S2, water is added to substance one to adjust the mass fraction of substance one to 30%, the pH is adjusted to 6.0, high temperature resistant α-amylase and anhydrous calcium chloride are added, and after liquefaction at 95°C for 25 minutes, medium temperature α-amylase is added, and liquefaction is continued for 18 minutes to obtain substance two.

[0108] Comparative Example 4

[0109] The difference between this comparative example and Example 1 is: S3, sending substance 2 into a saccharification tank, adjusting the pH to 5.5, the temperature to 55°C, adding β-amylase, isoamylase and sodium thiosulfate, saccharifying for 5 hours, raising the temperature to 60°C, adding pullulanase, and saccharifying for 8 hours to obtain substance 3.

[0110] The added amount of the β-amylase is 90 U / g corn starch.

[0111] Comparative Example 5

[0112] The difference between this comparative example and Example 1 is that the methyl polyethylene glycol maleimide has a molecular weight of 10,000 and is purchased from Kaixin Biotechnology.

[0113] Comparative Example 6

[0114] The difference between this comparative example and Example 1 is that the mass ratio of the β-amylase to the modifier is 1:7.

[0115] Comparative Example 7

[0116] The difference between this comparative example and Example 1 is: S3, sending substance 2 into a saccharification tank, adjusting the pH to 5.5, the temperature to 55°C, adding modified β-amylase, isoamylase, pullulanase and sodium thiosulfate, and after saccharification for 13 hours, obtaining substance 3.

[0117] Comparative Example 8

[0118] The difference between this comparative example and Example 1 is: S3, sending substance 2 into a saccharification tank, adjusting the pH to 5.5, the temperature to 55°C, adding modified β-amylase, isoamylase and sodium thiosulfate, and after saccharification for 13 hours, obtaining substance 3.

[0119] Performance Testing

[0120] The content of maltose in maltose syrup was tested according to the method in GB / T 20883-2017 Maltose; syrup yield = (mass of maltose syrup × mass fraction of solids) / (mass of corn starch × mass fraction of starch in corn starch) × 100%, where the mass fraction of solids was tested according to the method in GB / T 20883-2017 Maltose. The results are shown in Table 1.

[0121] Table 1 Measurement results

[0122]

[0123] According to statistics, the maltose syrup prepared by Examples 1 to 3 of the present invention has a high maltose content and syrup yield. Comparative Example 1 does not perform extrusion enzymolysis, Comparative Example 2 does not add anhydrous calcium chloride, Comparative Example 3 has a too high liquefaction temperature, Comparative Example 4 β-amylase is not modified, Comparative Example 5 methyl polyethylene glycol maleimide molecular weight is too high, Comparative Example 6 modifier addition is too high, Comparative Example 7 is not saccharified in steps, Comparative Example 8 does not add pullulanase, and the prepared maltose syrup has a low maltose content and a low syrup yield. Therefore, the maltose content in the maltose syrup prepared by the method described in this application is high, and the slurry yield is suitable for large-scale production, and can be widely used in food, medicine and other fields.

[0124] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing maltose syrup, characterized in that: The following steps are involved: S1. Add water to corn starch to obtain a mixture, and extrude to obtain substance 1; S2, add water to substance 1 to adjust the mass fraction of substance 1 to 25%-35%, adjust the pH to 5.5-6.5, add high temperature resistant α-amylase and anhydrous calcium chloride, liquefy at 90-100°C for 20-30min, cool to 65-75°C, add medium temperature α-amylase, continue liquefaction for 15-20min, and obtain substance 2; S3, sending substance 2 into a saccharification tank, adjusting the pH to 5.0-5.5, the temperature to 50-60°C, adding modified β-amylase, isoamylase and sodium thiosulfate, saccharifying for 3-6 hours, raising the temperature to 55-65°C, adding pullulanase, and saccharifying for 5-10 hours to obtain substance 3; S4, treating the substance with triple enzyme inactivation, filtering and decolorizing for a second time, and performing ion exchange, collecting the ion exchange liquid and concentrating it under vacuum to obtain; The addition amount of the thermostable α-amylase is 5-15 U / g corn starch; The amount of anhydrous calcium chloride added is 0.05% to 0.2% of the mass of the substance; The addition amount of the medium temperature α-amylase is 15-25U / g corn starch; The preparation method of the modified β-amylase comprises the following steps: placing the β-amylase and the modifier in buffer A respectively, stirring evenly, mixing at a molar ratio at 55-60° C. for 10 minutes, adding ammonium sulfate with a mass concentration of 70% until a precipitate is completely precipitated, centrifuging at 0-4° C. to obtain the precipitate, dissolving the precipitate in buffer B, removing the ammonium sulfate by an ultrafiltration membrane for 4 hours, separating and purifying by using a protein purifier combined with an anion exchange chromatography column and a gel column, and freeze-drying in a vacuum freeze dryer to obtain the modified β-amylase; The buffer A is a sodium hydrogen phosphate-citrate buffer with a pH of 5.8, and the buffer B is a sodium chloride solution with a concentration of 1 mol / L; The modifier is methyl polyethylene glycol maleimide, and the molecular weight is 1000-5000Da.

2. The method for preparing maltose syrup according to claim 1, characterized in that: The enzymatic activity of the β-amylase is 600,000-800,000 U / g.

3. The method for preparing maltose syrup according to claim 1, characterized in that: The mass ratio of the β-amylase to the modifier is 1:(3-5).

4. The method for preparing maltose syrup according to claim 1, characterized in that: The added amount of the modified β-amylase is 0.005-0.01 mg / g corn starch.

5. The method for preparing maltose syrup according to claim 4, characterized in that: The addition amount of the isoamylase is 30-50 U / g corn starch.

6. The method for preparing maltose syrup according to claim 5, characterized in that: The added amount of the pullulanase is 40-80 U / g corn starch.

7. The method for preparing maltose syrup according to claim 6, characterized in that: The specific steps of the secondary filtration and decolorization are: using diatomaceous earth filter aid and activated carbon for decolorization in sequence, and filtering after decolorization to remove impurities and starch residues.

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