WO2025112279A1 - Preparation method for maltodextrin - Google Patents

Abstract

The present invention belongs to the technical field of developing carbohydrate ingredients for foods for special dietary uses. Disclosed is a preparation method for maltodextrin. The present invention utilizes starch as a raw material, and utilizes dry thermal amorphization technology to disaggregate the molecular chain of starch and to improve the solid content of a reaction system, thereby reducing the viscosity of the system; then by means of the combination of polyethylene glycol precipitation fractionation, alcohol complexation fractionation and membrane interception fractionation, narrows the range of molecular weight distribution of maltodextrin; and finally performs batch drying to obtain a maltodextrin product having uniformly distributed degrees of polymerization, wherein the yield of maltodextrin can reach 80% or above. Different fractionated maltodextrin components collected and obtained in the present invention have stable functions and properties, thereby achieving great application prospects in the fields of functional ingredients of foods for special dietary uses, embedding carriers for flavor substances and food additives. In addition, the technical solution of the present invention can improve the production efficiency of maltodextrin, and reduce the drying cost and energy consumption, thus achieving significant advantages in environmental protection.

Description

A kind of preparation method of maltodextrin Technical Field

The invention relates to a preparation method of maltodextrin, and belongs to the technical field of development of special dietary carbohydrate ingredients.

Background Art

Maltodextrin refers to a starch hydrolysate with a degree of hydrolysis (DE) less than 20 obtained by acid or enzyme treatment using starch as raw material. Its main components are dextrin with a degree of polymerization (DP) above 10 and a small amount of oligosaccharides with a degree of polymerization below 10. It has the characteristics of a wide molecular weight distribution and a large dispersity coefficient.

At present, maltodextrin is usually produced by jet liquefaction and hydrothermal gelatinization. Jet liquefaction can achieve gelatinization and enzymatic hydrolysis of starch at the same time, but there are problems in the process such as incomplete gelatinization of some starch granules and insufficient enzymatic hydrolysis, resulting in low starch utilization rate; while the hydrothermal gelatinization process is to enzymatically hydrolyze the completely gelatinized starch to achieve starch liquefaction. The limitations of this method include: first, the solid content of the existing starch milk system is low (5%~10%, w/w), that is, the starch concentration is low, its production capacity is poor, and the product concentration consumes a lot of energy; second, if the starch concentration is increased, the viscosity of the system will increase significantly, which will not only hinder the effective diffusion and liquefaction of saccharifying enzymes, affect the enzymatic reaction rate and product yield, but also greatly increase the difficulty of subsequent dextrin separation.

Maltodextrin products with similar DE values show great differences in molecular weight distribution due to different production processes and raw material sources, thus having completely different properties. Therefore, the DE value is not enough to reflect the true processing quality of the product, and it is necessary to further distinguish maltodextrin products at the molecular level (Chronakis I S. On the molecular characteristics, compositional properties, and structural-functional mechanisms of maltodextrins: A review. DOI: 10.1080/10408699891274327). High molecular weight maltodextrin products (DP>50±5) have physiological functions such as regulating the intestines and delaying postprandial blood sugar, and can be used as special dietary functional ingredients; lower molecular weight maltodextrin (DP 30±5~50±5) has low hygroscopicity, and the appropriate chain length distribution is beneficial for its use in the embedding of flavor components and active substances; low molecular weight maltodextrin (DP 10±5~30±5) has good transparency and solubility, and has good stability as a food additive; while small molecular weight maltodextrin has a high content of reducing sugars such as glucose and maltose, which is easy to absorb moisture and browning reaction, affecting product quality. It can be seen that it is of great significance to grade and separate maltodextrin to obtain maltodextrin components with uniform polymerization distribution.

At present, the separation and purification methods of maltodextrin mainly include chromatography, membrane filtration and phase transition separation. Among them, the chromatography separation method mainly relies on the properties of the filler, with high cost and small processing volume; the phase transition separation method is based on the dependence of the solubility of different molecular weight fractions in the same polymer on the properties of the solvent to achieve precipitation classification of the substance. Its single classification method has problems such as poor classification effect and high solvent consumption. For example: Patent CN113699198A is to enzymatically hydrolyze and liquefy starch slurry with a mass concentration of 10% to 20%, add activated carbon for adsorption, filter, concentrate and dry, and obtain maltodextrin with a DE value of 1 to 2; Patent CN104789616B uses ethanol, polyethylene glycol and salt ions to separate single-component dextrin, and separates dextrin components of different molecular weights by gradually increasing the ethanol concentration; Patent CN111304270A is to prepare non-reducing low-polymerization maltodextrin with uniform polymerization degree by adding cyclodextrin glucosyltransferase (CGTase), cyclodextrin degrading enzyme (CDase) and/or maltooligosaccharide trehalose synthase (MTSase). It can be seen that the existing preparation methods of maltodextrin all have problems such as low starch solid content and no efficient separation of uniform polymerization maltodextrin.

In addition, patent CN104198668B uses polyethylene glycol to gradually precipitate dextrin components with molecular weights ranging from large to small, thereby obtaining dextrin with a molecular weight range of 5.443×10 ³ ~3.297×10 ⁴ Da; although the components separated from dextrin are uniform by this method, the separation steps are cumbersome and time-consuming, and 24 hours of standing are required after each addition of polyethylene glycol. The amount of polyethylene glycol used is large, and the concentration of dextrin used for separation is only 3.6%, which is not suitable for the separation of dextrin with a high solid content. At the same time, this method has low production intensity and is not conducive to industrial production. Patent CN107574198B is a method for separating spiral dextrin by alcohol. Specifically, 10% starch milk is used as raw material, and ethanol solutions with different volume fractions are used to separate cyclodextrin. The separation using ethanol requires standing at 4°C for 12 hours, and the minimum DP value prepared is only 40. Moreover, the concentration of dextrin separated by this method is low, and it is also not suitable for the separation of dextrin with high solid content. The separation effect is general, and the degree of polymerization of dextrin is relatively large.

Therefore, there is an urgent need to develop a preparation method for maltodextrin that has high starch solids content, high production intensity, high raw material utilization rate and a certain uniformity and is more suitable for industrial production.

Summary of the invention

In view of the problems of low starch solid content, high viscosity, insufficient enzymatic hydrolysis, large separation solvent consumption, low production capacity, etc. in maltodextrin prepared by traditional hydrothermal gelatinization and jet liquefaction, the present invention provides a method for preparing maltodextrin, specifically adopting high-temperature dry heat amorphization, enzymatic hydrolysis liquefaction, polyethylene glycol precipitation classification combined with alcohol complexation classification and membrane interception classification technology, and batch drying is used to achieve large-scale and efficient preparation of maltodextrin products with high yield and uniform degree of polymerization distribution on the basis of processing high solid content starch milk.

The first object of the present invention is to provide a method for preparing a maltodextrin product, comprising the steps of:

(1) Dry heat amorphization: dry heat treatment of starch at 180-200°C for 8-10 min to obtain dry heat treated starch;

(2) Enzymatic liquefaction: The starch after dry heat treatment is mixed with water to form starch milk, wherein the starch accounts for 35% to 40% of the total weight of the starch milk; the starch milk is then enzymatically hydrolyzed and inactivated to obtain an enzymatic hydrolyzate;

(3) Decolorization and impurity removal: decolorizing and impurity removal the enzymatic hydrolyzate obtained in step (2) to obtain a decolorized and impurity-free solution;

(4) Classification: firstly, the decolorized and impurity-free solution obtained in step (3) is mixed with polyethylene glycol 6000, and centrifuged to obtain a classification component 1 and a supernatant 1; wherein the amount of polyethylene glycol 6000 added is 30-40 g/100 mL of the decolorized and impurity-free solution;

The supernatant 1 is then mixed with anhydrous ethanol to obtain a mixed solution, and the mixed solution is centrifuged to obtain a fractionated component 2 and a supernatant 2; wherein the volume fraction of the anhydrous ethanol in the mixed solution is 50% to 60%;

Finally, the supernatant 2 was separated using a 1000-2000 Da hollow fiber membrane to obtain fractionated components 3;

(5) Drying: collecting the fraction 1, fraction 2 and fraction 3 obtained in step (4), and drying them separately to obtain a maltodextrin product.

In one embodiment, the starch described in step (1) is one or more of cereal starch, algae starch, and potato starch; optionally, the starch includes ordinary corn starch, wheat starch, chlorella starch, tapioca starch, potato starch, etc.

In one embodiment, the dry heat amorphization in step (1) is specifically:

The starch is spread on a steel plate with a thickness of 2-3 mm, and then dry-heat treated at 180-200°C for 8-10 min. Alternatively, the starch is spread on a steel plate with a thickness of 2-3 mm, and then dry-heat treated at 200°C for 8 min.

In one embodiment, the modulation in step (2) is carried out at a pH of 5.0-6.0 and a temperature of 65-70° C. for 4-6 min. Optionally, the modulation in step (2) is carried out at a pH of 5.0 and a temperature of 70° C. for 5 min.

In one embodiment, the enzymatic hydrolysis in step (2) is performed by adding 10-20 U/g α-amylase at a pH of 5.0-6.0 and 65-70°C for 5-10 min. Optionally, the enzymatic hydrolysis in step (2) is performed by adding 10 U/g α-amylase at a pH of 5.0 and 65°C for 5 min.

In one embodiment, the decolorization and impurity removal in step (3) are carried out using activated carbon and ion exchange resin; wherein, the decolorization using activated carbon is carried out by keeping the temperature at 80-90°C for 15-30 min, and the amount of activated carbon added is 1 g/100 mL of enzymatic hydrolyzate (abbreviated as 1%, w/v).

In one embodiment, the centrifugation in step (4) is performed at 8000-9000 r/min for 8-10 min.

In one embodiment, the molecular weight cut-off of the hollow fiber membrane in step (4) is 1000 or 2000 Da.

In one embodiment, the drying in step (5) includes but is not limited to: heat pump drying, vacuum drying, microwave drying, freeze drying, hot air drying; optionally, the drying is hot air drying, and the drying temperature is 50-70°C.

The second object of the present invention is to provide a maltodextrin product prepared by the above method.

In one embodiment, the degree of polymerization of the maltodextrin product includes: DP>50±5 or DP is between 30±5~50±5 or DP is between 10±5~30±5.

The third object of the present invention is to provide the use of the above-mentioned maltodextrin product in the preparation of special dietary functional ingredients, flavor substances or active molecule embedding carriers, and food additives.

In one embodiment, the application is to use the maltodextrin product with DP>50±5 as a special dietary functional ingredient.

In one embodiment, the application is to use the maltodextrin product with a DP of 30±5~50±5 as a flavor substance or active molecule embedding carrier.

In one embodiment, the application is to use the maltodextrin product with a DP of 10±5 to 30±5 as a food additive.

Beneficial effects of the present invention:

Different from the traditional method of preparing maltodextrin, the present invention uses dry heat amorphization technology to process starch, enzymatically hydrolyzes starch milk with high solid content (35%~40%, w/w), uses activated carbon for decolorization after enzymatic hydrolysis, and uses polyethylene glycol precipitation classification combined with alcohol complexation classification and membrane interception classification technology for separation. After separation, maltodextrin products with different DP ranges are obtained by batch drying. On the basis of achieving the processing of starch milk with high solid content, the present invention ensures large-scale and efficient preparation of maltodextrin products with high yield and uniform distribution of polymerization degree, and the yield of maltodextrin reaches more than 81%. The present invention obtains maltodextrin components with three DP value ranges, corresponding to different applications respectively.

Specific:

(1) The present invention uses dry heat amorphization to treat starch, which reduces the viscosity of starch during gelatinization, promotes starch declustering and gelatinization, and increases the solid content of starch milk, which can reach 35% to 40% (w/w); the method of the present invention increases the production capacity of maltodextrin and is suitable for large-scale production;

(2) The present invention sequentially uses polyethylene glycol precipitation classification, ethanol complexation classification and membrane interception classification technology to separate maltodextrin under the condition of high solid content starch milk, and obtains maltodextrin products with uniform polymerization degree while narrowing the distribution range of maltodextrin polymerization degree; the present invention improves the utilization rate of starch, reaching up to 82.6%;

(3) The present invention can be directly dried in batches after interception and classification, which saves the energy consumption required for the concentration process and the drying cost, has significant environmental advantages, and is more suitable for industrial production;

(4) The maltodextrin products prepared by the present invention have a degree of polymerization of: component 1 DP>50±5, component 2 DP 30±5~50±5, component 3 DP 10±5~30±5; component 1 can be used as a functional ingredient for special diets; component 2 can be used as an embedding carrier for flavor substances and active molecules; and component 3 can be used as a food additive, which has great application potential.

DETAILED DESCRIPTION

The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

Materials and Equipment:

The high-temperature dry-heat amorphization equipment used in the following experiments was a GZX-9146MBE blast drying oven produced by Shanghai Boxun Company; α-amylase was purchased from Sigma Company with an enzyme activity of 50,000 U/mL.

Test method:

1. Determination of starch hydrolysis rate (DE)

Reducing sugars were measured according to the Lane-Eynon method and the results were used to calculate the DE content. Specifically:

Take 0.50 g (dry basis) of anhydrous glucose reference and maltodextrin product respectively, add appropriate amount of distilled water to dissolve and dilute to 250 mL, shake well, as glucose reference solution and sample solution. Measure 25 mL of Fehling's reagent and 10 mL of distilled water, shake well, heat to boiling, and add 2 drops of 1% methylene blue solution. Titrate with glucose reference solution or sample solution until the blue color just disappears, and record the required volume of glucose reference solution or sample solution. The DE value is the percentage of reducing sugar (in terms of glucose) in the dry matter of the syrup, and the calculation formula is as follows:

2. Determination of starch utilization

Starch utilization is the maltodextrin yield, which is expressed as the ratio of the total mass of maltodextrin obtained after drying to the mass of starch used.

3. Determination of chain length distribution of maltodextrin

The chain length distribution of maltodextrin was determined by HPAEC-PAD. The pulsed amperometric detector model was ICS-5000+, the chromatographic column model was Dionex CarboPAC PA200, the mobile phase was NaOH solution (150 mmol/L), the flow rate was 0.4 mL/min, and the injection volume was 25 μL.

Example 1: Preparation and separation of maltodextrin

The corn starch was first subjected to a 200°C dry-heat amorphization treatment to prepare a 35% (w/w) starch milk, which was then enzymatically hydrolyzed at 70°C and decolorized with activated carbon. The products were then subjected to 40% (w/v) polyethylene glycol 6000 precipitation classification, 60% (v/v) ethanol complexation classification, and membrane interception classification separation, and then dried to obtain maltodextrin products with different degrees of polymerization.

The specific experimental steps are as follows:

(1) Dry heat amorphization: spread corn starch on a steel plate with a thickness of 3 mm and dry heat treat it at 200 °C for 8 min to obtain dry heat treated starch;

(2) Enzymatic liquefaction: Add water to the starch after dry heat treatment, adjust the pH to 5.0, and keep it at 70°C for 5 min to prepare a 35% (w/w, dry starch basis accounts for the total weight of starch milk) starch milk; then add 10 U/g α-amylase to the starch milk and perform enzymatic hydrolysis at pH 5.0 and 70°C for 5 min; adjust the solution pH to 4.5 to inactivate the enzyme, and obtain an enzymatic solution;

(3) Decolorization and impurity removal: 1% (w/v, g/mL) activated carbon was added to the enzymatic hydrolyzate and decolorized at 80°C for 30 min. The metal salts and pigments were then removed by ion exchange resin to obtain a decolorized and impurity-free solution.

(4) Classification: The decolorized and impurity-free solution is sequentially subjected to polyethylene glycol precipitation classification, ethanol complexation classification, and membrane interception classification to obtain maltodextrin components with uniform polymerization degree distribution:

Polyethylene glycol precipitation classification: the decolorized and impurity-free solution was mixed with polyethylene glycol 6000, stirred thoroughly and then allowed to stand for 2 h, and centrifuged at 8000 r/min for 10 min to obtain fraction 1 and supernatant 1; wherein, the amount of polyethylene glycol 6000 added was 40% (w/v, g/mL);

Ethanol complex fractionation: the supernatant 1 was mixed with anhydrous ethanol to obtain a mixed solution, and the volume fraction of anhydrous ethanol in the mixed solution reached 60%, and the mixture was allowed to stand for 30 min, and centrifuged at 8000 r/min for 10 min to obtain fractionated component 2 and supernatant 2;

Membrane fractionation: The supernatant 2 was separated using a 2000 Da hollow fiber membrane to obtain fraction 3;

(5) Drying: The graded component 1, the graded component 2, and the graded component 3 are dried by hot air at 70° C. to obtain three groups of maltodextrin products with uniform degree of polymerization.

Example 2: Preparation and separation of maltodextrin

The corn starch was first subjected to a 180°C dry-heat amorphization treatment to prepare a 35% (w/w) starch milk, which was then enzymatically hydrolyzed at 65°C and decolorized with activated carbon. The products were then subjected to 30% (w/v) polyethylene glycol 6000 precipitation classification, 50% (v/v) ethanol complexation classification, and membrane interception classification. The maltodextrin products with different degrees of polymerization were obtained by drying.

The specific experimental steps are as follows:

(1) Dry heat amorphization: spread corn starch on a steel plate with a thickness of 2 mm and dry heat treat it at 180 °C for 10 min to obtain dry heat treated starch;

(2) Enzymatic liquefaction: Add water to the starch after dry heat treatment, adjust the pH to 6.0, and keep it at 65°C for 5 min to prepare a 35% (w/w, starch dry basis accounts for the total mass of starch milk) starch milk; then add 20 U/g α-amylase to the starch milk and perform enzymatic hydrolysis at pH 5.0 and 65°C for 10 min; adjust the solution pH to 4.5 to inactivate the enzyme, and obtain an enzymatic hydrolyzate;

(3) Decolorization and impurity removal: 1% (w/v, g/mL) activated carbon was added to the enzymatic hydrolyzate and decolorized at 90°C for 30 min. After that, metal salts and pigments were removed by ion exchange resin to obtain a decolorized and impurity-free solution.

(4) Classification: The decolorized and impurity-free solution is sequentially subjected to polyethylene glycol precipitation classification, ethanol complexation classification, and membrane interception classification to obtain maltodextrin components with uniform polymerization degree distribution:

Polyethylene glycol precipitation classification: the decolorized and impurity-free solution was mixed with polyethylene glycol 6000, stirred thoroughly and then allowed to stand for 2 h, and centrifuged at 8000 r/min for 10 min to obtain fraction 1 and supernatant 1; wherein the amount of polyethylene glycol 6000 added was 30% (w/v, g/mL);

Ethanol complex fractionation: the supernatant 1 was mixed with anhydrous ethanol to obtain a mixed solution, and the volume fraction of anhydrous ethanol in the mixed solution reached 50%, and the mixture was allowed to stand for 30 min, and centrifuged at 8000 r/min for 10 min to obtain fractionated component 2 and supernatant 2;

Membrane fractionation: The supernatant 2 was separated using a 2000 Da hollow fiber membrane to obtain fraction 3;

(5) Drying: The graded component 1, the graded component 2, and the graded component 3 are dried by hot air at 70° C. to obtain three groups of maltodextrin products with uniform degree of polymerization.

Example 3: Preparation and separation of maltodextrin

The cassava starch was firstly subjected to a 180°C dry-heat amorphization treatment to prepare a 40% (w/w) starch milk, and then enzymatically hydrolyzed at 70°C. After enzymatic hydrolysis, it was decolorized with activated carbon, and then subjected to 30% (w/v) polyethylene glycol precipitation classification, 60% (v/v) ethanol complexation classification, and membrane interception classification separation. Maltodextrin products with different degrees of polymerization were obtained by drying.

The specific experimental steps are as follows:

(1) Dry heat amorphization: Cassava starch was spread on a steel plate with a thickness of 3 mm and dry-heat treated at 180 °C for 10 min to obtain dry heat treated starch;

(2) Enzymatic liquefaction: Add water to the starch after dry heat treatment, adjust the pH to 5.0, and keep it at 70°C for 5 min to prepare a 40% (w/w, dry starch basis accounts for the total mass of starch milk) starch milk; then add 20 U/g α-amylase to the starch milk and perform enzymatic hydrolysis at pH 5.0 and 70°C for 10 min; adjust the solution pH to 4.5 to inactivate the enzyme, and obtain an enzymatic solution;

(3) Decolorization and impurity removal: 1% (w/v, g/mL) activated carbon was added to the enzymatic hydrolyzate and decolorized at 80°C for 30 min. After that, metal salts and pigments were removed by ion exchange resin to obtain a decolorized and impurity-free solution.

(4) Classification: The decolorized and impurity-free solution is sequentially subjected to polyethylene glycol precipitation classification, ethanol complexation classification, and membrane interception classification to obtain maltodextrin components with uniform polymerization degree distribution:

Polyethylene glycol precipitation classification: the decolorized and impurity-free solution was mixed with polyethylene glycol 6000, stirred thoroughly and then allowed to stand for 2 h, and centrifuged at 8000 r/min for 10 min to obtain fraction 1 and supernatant 1; wherein the amount of polyethylene glycol 6000 added was 30% (w/v, g/mL);

Ethanol complex fractionation: the supernatant 1 was mixed with anhydrous ethanol to obtain a mixed solution, and the volume fraction of anhydrous ethanol in the mixed solution reached 60%, and the mixture was allowed to stand for 30 min, and centrifuged at 8000 r/min for 10 min to obtain fractionated component 2 and supernatant 2;

Membrane fractionation: The supernatant 2 was separated using a 1000 Da hollow fiber membrane to obtain fraction 3;

(5) Drying: The graded component 1, the graded component 2, and the graded component 3 are dried by hot air at 70° C. to obtain three groups of maltodextrin products with uniform degree of polymerization.

Comparative Example 1: Preparation of maltodextrin by hydrothermal gelatinization

On the basis of Example 1, step (1) and step (2) were changed as follows: 35% (w/w, dry starch basis accounts for the total mass of starch milk) of starch milk was prepared and gelatinized in a boiling water bath for 30 min. Other conditions were the same as those in Example 1.

Comparative Example 2: Changing the dry heat amorphization temperature to 140°C

On the basis of Example 1, the dry heat amorphization temperature in step (1) was changed to 140° C., and the other conditions were the same as those in Example 1.

Comparative Example 3: Preparation of maltodextrin by jet liquefaction

On the basis of Example 1, the dry heat amorphization operation of step (1) was omitted, and step (2) was changed to gelatinize the starch by jet liquefaction, that is, 10 U/g α-amylase was added to the starch milk and a liquefied liquid was obtained by jet liquefaction. The pressure of the jet liquefied material was set to 0.35 MPa, the steam pressure was 0.1 MPa, the temperature was 90°C, the time was 8 min, and then the temperature was kept at 70°C for 5 min. The other conditions were the same as in Example 1.

Comparative Example 4: Preparation of maltodextrin without classification

Based on Example 1, step (4) classification was omitted, and other conditions were the same as those in Example 1. The prepared maltodextrin was detected, and its DP distribution was 1-70, and the molecular weight distribution was uneven, which was a mixture of glucose, maltose, oligosaccharides and polysaccharides.

Comparative Example 5: Preparation of maltodextrin, single use of polyethylene glycol precipitation and classification

Based on Example 1, the classification step in step (4) is changed to:

The decolorized and impurity-free solution was mixed with polyethylene glycol 6000 at a concentration of 40% (w/v, g/mL), stirred thoroughly and allowed to stand for 2 h, and centrifuged at 8000 r/min for 10 min to obtain fractionated component 1 and supernatant 1;

Polyethylene glycol 6000 was further added to the supernatant 1 until the amount of polyethylene glycol 6000 added reached 50% (w/v, g/mL). After being fully stirred, the mixture was allowed to stand for 2 h and centrifuged at 8000 r/min for 10 min to obtain component 2. Other conditions were the same as those in Example 1.

Comparative Example 6: Preparation of maltodextrin using only alcohol complexation and classification technology

Based on Example 1, the classification step in step (4) is changed to:

The decolorized and impurity-free solution was mixed with anhydrous ethanol to obtain a mixed solution, and the volume fraction of anhydrous ethanol in the mixed solution reached 30%, and the mixture was allowed to stand for 30 minutes, and centrifuged at 8000 r/min for 10 minutes, and the obtained precipitate was maltodextrin fraction 1 and supernatant 1;

Anhydrous ethanol was further added to the supernatant 1 to make the volume fraction of anhydrous ethanol reach 60%, and the mixture was allowed to stand for 30 min and centrifuged at 8000 r/min for 10 min. The resulting precipitate was maltodextrin fraction 2 and supernatant 2.

Anhydrous ethanol was further added to the supernatant 2 to make the volume fraction of anhydrous ethanol reach 80%, and the mixture was allowed to stand for 30 min and centrifuged at 8000 r/min for 10 min. The resulting precipitate was maltodextrin fraction 3. Other conditions were the same as those in Example 1.

Comparative Example 7: Preparation of maltodextrin using only membrane interception and classification technology

Based on Example 1, the classification step in step (4) is changed to:

Hollow fiber membranes with molecular weight cutoffs of 10000, 5000 and 2000 Da were used to separate the decolorized and impurity-removed solutions, respectively, to obtain maltodextrin fractionation components 1, 2 and 3, and other conditions were the same as those in Example 1.

Comparative Example 8: Preparation of maltodextrin, changing the order of fractionation

Based on Example 1, the order of the classification steps in step (4) is changed to:

Ethanol complexation fractionation: the decolorized and impurity-removed solution was mixed with anhydrous ethanol to make the volume fraction of anhydrous ethanol reach 60%, and the mixture was allowed to stand for 30 min and centrifuged at 8000 r/min for 10 min. The resulting precipitate was maltodextrin fraction 1 and supernatant 1.

Polyethylene glycol precipitation fractionation: Supernatant 1 was mixed with polyethylene glycol 6000 at a concentration of 40% (w/v, g/mL), stirred thoroughly and allowed to stand for 2 h, and centrifuged at 8000 r/min for 10 min. The resulting precipitate was maltodextrin fraction 2 and supernatant 2.

Membrane fractionation: The membrane separation was carried out by using a hollow fiber membrane with a molecular weight cutoff of 2000 Da to separate the supernatant obtained by ethanol complex fractionation to obtain maltodextrin fraction 3. Other conditions were the same as those in Example 1.

The polymerization degree and yield of the maltodextrin products prepared in Examples 1 to 3 and Comparative Examples 1 to 8 were tested, and the results are shown in Tables 1 and 2.

Table 1 Chain length distribution of maltodextrin

Note: DP stands for degree of polymerization; “-” stands for the absence of this fraction; the content of the final separated product represents the percentage of maltodextrin in the three fractions to the total maltodextrin weight, and the sum of the three components is 100%.

Table 2 Maltodextrin yield

It can be seen from Table 1 and Table 2 that the maltodextrin yield (starch utilization rate) of the method in Example 1 can reach 82.1%, and the chain lengths of the maltodextrin fractions 1, 2, and 3 are distributed in DP>50, DP 30-50, and DP 10-30, respectively; the maltodextrin yield of the method in Example 2 can reach 81.7%, and the chain lengths of the maltodextrin fractions 1, 2, and 3 are distributed in DP>55, DP 35-55, and DP 10-35, respectively; the maltodextrin yield of the method in Example 3 can reach 82.6%, and the chain lengths of the maltodextrin fractions 1, 2, and 3 are distributed in DP>55, DP 25-55, and DP 5-25, respectively.

Comparing Example 1 with Comparative Example 4, it can be seen that the polymerization degree of the maltodextrin product after fractionation is uniform, and the maltodextrin product after fractionation is three groups of DP>50, DP 30~50 and DP 10~30; while Comparative Example 4 is maltodextrin that has not been separated, and its DP is between 1 and 70. The prepared maltodextrin is a mixture of glucose, maltose, oligosaccharides and polysaccharides, and the uniformity is poor. Glucose and maltose have high reducing properties, and they are prone to Maillard reaction when they coexist with amino acids or proteins, thereby reducing the product quality of maltodextrin.

In addition, the three groups of maltodextrin components obtained after graded separation in Example 1 have improved uniformity of polymerization degree, and the product can be quickly dried by hot air drying technology. Compared with the concentration and spray drying technology required for unfractionated maltodextrin, it saves drying costs and is beneficial to improving the stability of maltodextrin in industrial preparation.

By comparing Examples 1 to 3 with Comparative Examples 1 to 3, it can be seen that the use of dry heat amorphization to treat starch can increase the maltodextrin yield to more than 80%; by comparing Example 1 with Comparative Example 2, it can be seen that the temperature of dry heat amorphization is a key factor affecting the maltodextrin yield, and the maltodextrin yield prepared by dry heat treating starch at a lower temperature is lower.

It can be seen that the viscosity of starch milk is high under hydrothermal gelatinization conditions, which hinders the diffusion and contact of enzyme and substrate in the subsequent enzymatic hydrolysis reaction, reduces the reaction rate and incomplete enzymatic hydrolysis, resulting in a low maltodextrin yield; while lowering the dry heat amorphization temperature will reduce the degree of starch chain declustering, increase the viscosity of starch paste, weaken the fluidity, lead to incomplete enzymatic hydrolysis, and further increase the loss of classification; during the jet liquefaction process, starch gelatinization and enzymatic hydrolysis start at the same time, starch gelatinization is not complete, resulting in a decrease in maltodextrin yield, and jet liquefaction also increases the energy consumption and economic cost of maltodextrin production.

By comparing Example 1 with Comparative Examples 6 and 7, it can be seen that the maltodextrin yield using polyethylene glycol precipitation classification, ethanol complexation classification and membrane interception classification in sequence is higher than that using only one of the separation methods; by comparing Example 1 with Comparative Examples 5 and 8, it can be seen that only under a specific order of classification steps, the separation effect of maltodextrin components with different DP values is good and a high yield is maintained.

Comparative Example 5 can only obtain two groups of maltodextrin components with a degree of polymerization of DP>50 and DP of 1-50. Although the yield of maltodextrin is high, the separation effect is poor. Among them, the maltodextrin component with a DP of 1-50 is not only poor for the embedding effect of flavor components and active substances, but also does not have good transparency and solubility. Moreover, because it contains small molecular reducing sugars, it is easy to absorb moisture and browning reaction. The reason for the poor separation effect of Comparative Example 5 is that when the addition amount of polyethylene glycol 6000 reaches 40% (w/v, g/mL) for classification, the maltodextrin component with DP>50 precipitates, and the remaining maltodextrin component in the supernatant has a DP<50. When polyethylene glycol is continued to be added, the reaction system will be too viscous to reduce the distribution range of the degree of polymerization of the product by centrifugation.

The yield of maltodextrin prepared in Comparative Example 6 was 65.5%. This was because the volume of the maltodextrin solution increased significantly and the concentration decreased during the addition of anhydrous ethanol, resulting in increased separation loss.

The yield of maltodextrin prepared in Comparative Example 7 was reduced to 58.4%. This is because the high substrate concentration maltodextrin solution is difficult to intercept when using membrane separation, resulting in a reduced yield of maltodextrin. At the same time, the amount of hollow fiber membrane used in the separation process is large, the loss of maltodextrin increases, and the cost of the hollow fiber membrane increases.

In comparative example 8, only two groups of maltodextrin components with chain lengths distributed in DP>30 and DP 10~30 can be obtained. Adjusting the order of the classification steps results in the inability to narrow the distribution range of the degree of polymerization of maltodextrin with DP>30, and the maltodextrin components with DP>50 and DP 30~50 cannot be separated. This is because it is difficult for polyethylene glycol to precipitate maltodextrin components with smaller molecular weights, and the first use of ethanol complexation classification will cause the components with smaller DP values and the components with larger DP to precipitate together, resulting in the separated maltodextrin components with DP>30. At this time, polyethylene glycol is used to precipitate the maltodextrin components with DP<30 in the supernatant 1, and there is no significant separation effect. Among the components separated in this order, only the maltodextrin components with DP of 10~30 can be used for the embedding of flavor components and active substances, and the components with DP>30 cannot be separated to obtain components with DP>50 and DP 30~50, so they are poorly used as special dietary functional ingredients, and the embedding efficiency of flavor components, active substances, etc. is low.

In summary, polyethylene glycol has a good classification effect on macromolecular maltodextrin, and can effectively precipitate maltodextrin components with DP>50; ethanol complexation technology can effectively separate maltodextrin components with DP>30, but cannot separate maltodextrin components with DP<15; in order to save solvent consumption and drying costs, membrane separation and filtration of maltodextrin components with DP<10 are selected. The combination of the three can obtain three groups of maltodextrin components with chain lengths distributed in DP>50±5, DP 30±5~50±5, and DP 10±5~30±5, and each component has a corresponding range of use.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

A method for preparing maltodextrin, characterized in that it comprises the following steps: (1) Dry heat amorphization: dry heat treatment of starch at 180-200°C for 8-10 min to obtain dry heat treated starch; (2) Enzymatic hydrolysis and liquefaction: The starch after dry heat treatment is mixed with water to form starch milk, wherein the starch accounts for 35% to 40% of the total mass of the starch milk; the starch milk is then enzymatically hydrolyzed and inactivated to obtain an enzymatic hydrolyzate; (3) Decolorization and impurity removal: decolorizing and impurity removal the enzymatic hydrolyzate obtained in step (2) to obtain a decolorized and impurity-free solution; (4) Classification: firstly, the decolorized and impurity-free solution obtained in step (3) is mixed with polyethylene glycol 6000, and centrifuged to obtain a classification component 1 and a supernatant 1; wherein the amount of polyethylene glycol 6000 added is 30-40 g/100 mL of the decolorized and impurity-free solution; The supernatant 1 is then mixed with anhydrous ethanol to obtain a mixed solution, and the mixed solution is centrifuged to obtain a fractionated component 2 and a supernatant 2; wherein the volume fraction of the anhydrous ethanol in the mixed solution is 50% to 60%; Finally, the supernatant 2 was separated using a 1000-2000 Da hollow fiber membrane to obtain fractionated components 3; (5) Drying: collecting the fraction 1, fraction 2 and fraction 3 obtained in step (4), and drying them separately to obtain maltodextrin products. The method according to claim 1 is characterized in that the starch in step (1) includes but is not limited to cereal starch, algae starch, and potato starch. The method according to claim 1 is characterized in that the modulation in step (2) is carried out at a pH of 5.0~6.0 and a temperature of 65~70°C for 4~6 min. The method according to claim 1 is characterized in that the enzymatic hydrolysis in step (2) is performed by adding 10~20 U/g α-amylase at a pH of 5.0~6.0 and 65~70°C for 5~10 min. The method according to claim 1 is characterized in that the decolorization and impurity removal in step (3) uses activated carbon and ion exchange resin; wherein the activated carbon is used for decolorization by keeping the temperature at 80-90°C for 15-30 min, and the amount of activated carbon added is 1 g/100 mL of enzymatic hydrolyzate. The maltodextrin product can be prepared by any method described in claims 1 to 5. The maltodextrin product according to claim 6 is characterized in that the degree of polymerization of the maltodextrin product includes: DP>50±5 or DP is between 30±5~50±5 or DP is between 10±5~30±5. The use of the maltodextrin product described in claim 6 or 7 in the preparation of special dietary functional ingredients, flavor substances or active molecule embedding carriers, and food additives. The application according to claim 8 is characterized in that the application is to use maltodextrin products with DP>50±5 as special dietary functional ingredients; to use maltodextrin products with DP between 30±5~50±5 as flavor substances or active molecule encapsulation carriers; to use maltodextrin products with DP between 10±5~30±5 as food additives.