WO2022156401A1

WO2022156401A1 - Preparation method for slow digestible starch with loose structure

Info

Publication number: WO2022156401A1
Application number: PCT/CN2021/135955
Authority: WO
Inventors: 徐恩波; 刘东红; 冯劲松; 唐君钰; 马硕晗; 秦宇; 朱青青; 姚思羽; 王文骏; 程焕; 田金虎; 吴正宗; 李丹丹; 丁甜; 周建伟; 陈健乐; 叶兴乾
Original assignee: 浙江大学
Priority date: 2021-01-25
Filing date: 2021-12-07
Publication date: 2022-07-28
Also published as: CN112852903A

Abstract

A preparation method for slow digestible starch with a loose structure: implementing co-extrusion treatment of amylase and compound starch; after extrusion, adding glucosidase to implement a transglycosidation reaction, drying the product of the transglycosidation reaction to a moisture content of 30-50 wt%, and then performing temperature-controlled crystallisation to obtain the slow digestible starch with a loose structure; the action site of the amylase is an α-1,4 glycosidic bond or a β-1,4 glycosidic bond; the temperature-controlled crystallisation method comprises: reducing the temperature at a rate of 0.1-4.5°C/min down to a crystallisation temperature, and maintaining the temperature for 2-8 days of regenerative crystallisation, the crystallisation temperature being -20-10℃; the enzymatic activity range of the amylase is 5-55 U/g; the enzymatic activity range of the glucosidase is 10-90 U/g, and the enzymatic activity is defined as the amount of enzymatic activity (U) added per gram of starch dry base.

Description

A kind of preparation method of slow-digestible starch with loose structure

technical field

The invention relates to a preparation method of slow-digesting polysaccharide ingredient products, in particular to a method for processing slow-digesting starch that utilizes natural micro-resistant crystal nuclei and forms a branched-chain crystal cluster loose structure, and belongs to the technical field of starch processing.

Background technique

Slowly digestible starch (SDS) is a new type of dietary fiber formed by structural reorganization after starch gelatinization and melting. It has the functions of slow digestion and absorption, continuous release of energy, and maintenance of blood sugar stability after meals. Among the functional food ingredients eaten by obese people, it has increasingly become a research hotspot in the field of food science and modern nutrition. Factors affecting the formation of SDS structure include amylose chain length, original crystallinity, branched structure of amylopectin, retrogradation characteristics, etc. In recent years, researchers have focused on forming different resistance building blocks by forming starch-ligand complexes and regulating processing conditions. However, due to the lack of effective regulation of the retrogradation behavior of starch chains by the traditional hydrothermal method for preparing SDS, the enzyme resistance is mostly derived from the highly dense crystalline lamellar structure. Therefore, the modified products often have large molecular weight, high hardness and palatability. Sexual limitations, etc. In addition, there is a potential waste of "natural" micro-resistant nuclei resources due to the lack of clarity in the current study of the nucleation structure. Therefore, the construction of starch micro-resistance domains still needs to rationally use regulatory strategies on the existing basis to explore natural advantages. On the premise of avoiding the introduction of chemical reagents with unknown risks, functional starch modified by green and efficient processing methods can be prepared. New product.

Based on this, the present invention utilizes the green processing method of enzymatic extrusion to efficiently modify starch chains, that is, the multi-directional shear force provided by the traditional extrusion cavity or screw configuration and the enzymatic hydrolysis force are reasonably coordinated, and the directional control of starch crystallization The branched-chain structure in the region is changed by slow temperature-controlled crystallization to change its retrogradation kinetics, thereby obtaining the SDS with the loose branched-chain crystalline cluster structure. The preparation method not only improves the palatability of SDS, but also achieves the purpose of effectively controlling the slow degradation of its resistant components in the human body, and can effectively reduce the rising rate of postprandial blood sugar.

SUMMARY OF THE INVENTION

The present invention provides a method for preparing SDS with loose structure by effectively utilizing "natural" micro-resistant crystal nuclei, and utilizing the coupled multi-physics field processing environment in an extrusion cavity to promote the hydrolysis and gelatinization of starch amyloid chains and partial branched chains. Supplemented by transglycosidic reaction, the branched chain side branches are extended to form branched crystalline clusters with high degree of debranch (DB), which are arranged in a loose growth ring structure, that is, the loosely structured SDS is obtained.

In order to realize the above-mentioned content of the invention, the technical scheme of the present application is as follows:

A preparation method of SDS with loose structure: the amylase whose action site is α-1,4 glycosidic bond or β-1,4 glycosidic bond is co-extruded with compound starch. After extrusion, transglucosidase was added to carry out the transglycosidase reaction. Subsequently, the transglycosidic reaction product was dried to a moisture content of 30 to 50 wt%, then cooled to a crystallization temperature of -20 to 10 °C at a rate of 0.1 to 4.5 °C/min, and maintained at this temperature for 2 to 8 days of retrogradation. Crystallization to obtain the loosely structured SDS;

Further, the enzymatic activity range of amylase is: 5～55U/g; The enzymatic activity range of the glucosidase is: 10～90U/g, and the enzymatic activity is defined as the enzyme added per gram of starch dry base Liveness (U).

After adding α-1,4-glycosidic bond or β-1,4-glycosidic bond-directed hydrolase liquid to corn starch with high branched chain ratio in fixed ratio, the multi-physics fields such as extrusion synergistic shear field and temperature field are used to The compound material is processed and modified to promote the hydrolysis and gelatinization of starch linear and partially branched chains, thereby exposing more "natural" micro-resistant crystal nuclei. Since the starch crystalline region is mainly formed by the branched single/double helix and the linear-branched double helix, the present invention utilizes glucosidase to orientately regulate the branched structure before the starch chain is recrystallized, which extrudes the product by enzymatic method. The increased α-glucan or β-glucan is branched to the branched side branches of the original crystal nucleus to form a new α-1,6 glycosidic bond, that is, a transglycosidic reaction. During retrogradation, the slow temperature-controlled crystallization at low temperature can slow down the movement speed of starch amyloid chains and endow the branched chains with more time and space for cyclotron crystallization. The orderly arrangement of side branches of amylopectin chains with high DB can support a wider crystal plane structure, form a loose growth ring structure, and form a branched-chain crystal cluster "outsourcing" structure while retaining the original resistant crystal texture type of loosely structured SDS.

Further, the amylase is one or both of α-amylase and β-amylase.

Further, the compound starch contains 2-8 parts by weight of amylopectin and 1 part by weight of amylose.

Further, the compound starch is corn starch.

As a preferred solution, before the extrusion, the moisture content of the mixed material of the composite enzyme and starch is adjusted to be 20-40 wt%.

Further, the co-extrusion treatment adopts a screw extruder, and the temperature zone distribution is 40-60°C, 50-70°C, 60-80°C, 70-90°C and 80-100°C in turn; the screw speed is set to 50-250r /min. The temperature of the warm zone increases sequentially.

Further, the transglycosidic reaction is as follows: constant temperature stirring in acetate buffer (pH 5.2) at 50°C for 12h.

Further, the types of amylase include: one or more of high temperature resistant alpha-amylase, mesophilic alpha-amylase and beta-amylase.

The beneficial technical effects of the invention are as follows: compared with the traditional hydrothermal method for preparing SDS, the present invention utilizes a combined biological enzyme-extrusion processing method, and follows the principle of "local enzymatic hydrolysis of linear chains and gelatinization to destroy the macro-domain" during the gradient heating process. Based on the restrictive sequential modification principle, and supplemented by screw extrusion disordered unchaining, the branched chain is extended after effectively exposing the "natural" microcrystalline nuclei, and a starch modified product with both resistance and high-quality taste is obtained through slow crystallization. On the one hand, the present invention realizes the directional regulation of starch microdomains on the basis of natural texture, and on the other hand, it also improves the bad taste brought by the high-resistance structure of starch for a long time, and further expands the practical application of SDS.

Description of drawings

Fig. 1 is the process flow diagram of the loosely structured SDS prepared by the present invention;

Fig. 2 is the small angle X-ray scattering (SAXS) spectrum of the loosely structured SDS prepared in Examples 1-3 of the present invention, for illustrating the long period L _Lorentz ;

Fig. 3 is the size exclusion chromatography (SEC) spectrum of the loosely structured SDS prepared in Examples 1-3 of the present invention, used to illustrate the degree of branching (DB);

4 is a scanning electron microscope (SEM) microscopic image of the loosely structured SDS prepared in Examples 1-3 of the present invention, which is used to directly prove the loosely structured SDS prepared by the present invention.

Detailed ways

The present invention is further illustrated by the following examples, which are used for the purpose of illustration and not for limiting the scope of the present invention.

Example 1

A preparation method of SDS with loose structure, the steps are as follows:

(1) Enzyme extrusion: prepare corn starch with high branched chain ratio: 8:1 (w/w), and adjust its moisture content to 20wt%. The high temperature resistant α-amylase solution (5U/g) was co-extruded with a gradient temperature rise with the compounded corn starch: the temperature zone distribution was 60°C, 70°C, 80°C, 90°C and 100°C in sequence, and the screw speed was set is 250r/min;

(2) Transglycosidase reaction: add 90U/g glucosidase to the amyloid obtained in step (1), stir at a constant temperature in acetate buffer (pH 5.2) at 50°C for 12h, and post-bake dry to a moisture content of 30wt%;

(3) Temperature-controlled crystallization: The dried amyloid was lowered to 10°C at a cooling rate of 0.1°C/min, and stored at this temperature for 8 days for regeneration. Grind after freeze-drying and pass through a 100-mesh sieve to obtain the loosely structured SDS;

(4) Detection of crystal long period: The small angle X-ray scattering (SAXS) system was used to detect the lamellar structure of starch crystals.

The processed data are collected within the scattering vector (Q) range of . Using the obtained one-dimensional scattering function to draw a graph: θ ² I(θ)～θ, and analyze the starch structure, calculate the long-period L _Lorentz after structural reorganization according to the Bragg formula:

2L _Lorentz sinθ=λ

where 2θ is the scattering angle (°) and λ is the X-ray wavelength (nm).

(5) Simulated digestion in vitro: The sample was timed digested at 37°C with mixed enzyme solution. The enzyme activity ratio of the mixed enzyme solution is: trypsin (500U/ml): glucosidase (700U/ml): invertase (400U/ml). . Glucose oxidase detection kit (GOPOD-FORMAT) was used to detect free-sugar glucose (FSG), glucose of 20 (G20) after 20min digestion, glucose (glucose of 120, G120) and total sugar after 120min digestion (total glucose, TG), and calculate the yield (%) of SDS, the formula is as follows:

SDS(%)=(G120-G20)×0.9/TS×100

Among them, the conversion coefficient of 0.9 was used to convert glucose into starch values of different digestive components, and TS was the total starch mass (g).

(6) DB detection: use size exclusion chromatography to detect the weight distribution N _de (X) of starch chains, and calculate DB (%) accordingly, the formula is as follows:

DB(%)=1/N _de (X)×100

The L _Lorentz of the SDS prepared in this example is 18.39 nm, which is significantly longer than the 9-10 nm growth cycle of native starch, and the SDS content in the starch is 48.63% and the DB is 16.53%. It can be seen that this SDS has a loose structure and is a starch modification product with both resistance and good taste.

Example 2

A preparation method of SDS with loose structure, the steps are as follows:

(1) Enzyme extrusion: prepare corn starch with high branched chain ratio: 5:1 (w/w), and adjust its moisture content to 30wt%. The medium-temperature α-amylase solution (25U/g) and the compounded corn starch were subjected to gradient heating and co-extrusion: the temperature zone distribution was 50°C, 60°C, 70°C, 80°C, and 90°C, and the screw speed was set to 150r/min;

(2) Transglycosidase reaction: add 50U/g glucosidase to the amyloid obtained in step (1), stir at a constant temperature in acetate buffer (pH 5.2) at 50°C for 12h, and post-bake dry to a moisture content of 40wt%;

(3) Temperature-controlled crystallization: The dried amyloid was lowered to 0°C at a cooling rate of 2.5°C/min, and stored at this temperature for 5 days for regeneration. Grind after freeze-drying and pass through a 100-mesh sieve to obtain the loosely structured SDS;

(4) Detection of crystal long period: SAXS was used to detect the lamellar structure of starch crystals, and

2L _Lorentz sinθ=λ

where 2θ is the scattering angle (°) and λ is the X-ray wavelength (nm).

(5) Simulated digestion in vitro: The sample was timed digested at 37°C with mixed enzyme solution. The enzyme activity ratio of the mixed enzyme solution is: trypsin (500U/ml): glucosidase (700U/ml): invertase (400U/ml). Use the glucose oxidase detection kit (GOPOD-FORMAT) to detect the absorbance at FSG, G20, G120 and TG, and calculate the yield (%) of SDS, the formula is as follows:

SDS(%)=(G120-G20)×0.9/TS×100

DB(%)=1/N _de (X)×100

The SDS prepared in this example has a crystal long period of 17.65 nm, which is significantly longer than the growth ring long period of 9-10 nm of native starch, and the SDS content in the starch is 44.72%, and the DB is 14.19%. It can be seen that this SDS has a loose structure and is a starch modification product with both resistance and good taste.

Example 3

A preparation method of SDS with loose structure, the steps are as follows:

(1) Enzyme extrusion: prepare corn starch with high branched chain ratio: 2:1 (w/w), and adjust its moisture content to 40wt%. The β-amylase solution (55U/g) was co-extruded with gradient heating with the compounded corn starch: the temperature zone distribution was 40°C, 50°C, 60°C, 70°C and 80°C in turn, and the screw speed was set to 50r /min;

(2) Transglycosidase reaction: add 10U/g glucosidase to the amyloid obtained in step (1), stir at a constant temperature in acetate buffer (pH 5.2) at 50°C for 12h, and post-bake dry to a moisture content of 50wt%;

(3) Temperature-controlled crystallization: The dried amyloid was lowered to -20°C at a cooling rate of 4.5°C/min, and stored at this temperature for 2 days for regeneration. Grind after freeze-drying and pass through a 100-mesh sieve to obtain the loosely structured SDS;

2L _Lorentz sinθ=λ

where 2θ is the scattering angle (°) and λ is the X-ray wavelength (nm).

SDS(%)=(G120-G20)×0.9/TS×100

DB(%)=1/N _de (X)×100

The SDS prepared in this example has a crystal long period of 16.97 nm, which is significantly longer than the growth ring long period of 9-10 nm of native starch, and the SDS content in the starch is 41.52%, and the DB is 11.27%. It can be seen that this SDS has a loose structure and is a starch modification product with both resistance and good taste.

Claims

A preparation method of slow-digested starch with loose structure, characterized in that:

The amylase is co-extruded with the compound starch. After extruding, adding glucosidase to carry out the transglycosidase reaction, then drying the transglycosidase reaction product to a moisture content of 30-50 wt%, and then performing temperature-controlled crystallization to obtain the slowly digested starch with loose structure;

The action site of the amylase is α-1,4 glycosidic bond or β-1,4 glycosidic bond;

The temperature-controlled crystallization method is as follows: cooling down to the crystallization temperature at a rate of 0.1-4.5°C/min, and maintaining this temperature for 2-8 days of retrogradation crystallization, and the crystallization temperature is -20-10°C;

The enzymatic activity range of the amylase is: 5～55U/g; the enzymatic activity range of the glucosidase is: 10～90U/g, and the enzymatic activity is defined as the enzymatic activity added per gram of starch dry base volume (U).
The preparation method according to claim 1, wherein the amylase is one or both of α-amylase and β-amylase.
The preparation method according to claim 1, wherein the compound starch comprises 2-8 parts by weight of amylopectin and 1 part by weight of amylose.
The preparation method according to claim 1, wherein the compound starch is corn starch.
The preparation method according to claim 1, characterized in that, before the extrusion, the moisture content of the mixture of amylase and compound starch is adjusted to be 20-40 wt%.
The preparation method according to claim 1, wherein the co-extrusion process adopts a screw extruder, and the temperature zone distribution is 40-60°C, 50-70°C, 60-80°C, and 70-90°C in sequence. and 80 to 100 °C; the screw speed is set to 50 to 250 r/min. The temperature of the warm zone increases sequentially.
The preparation method according to claim 1, characterized in that, the transglycosidic reaction is as follows: constant temperature stirring in acetate buffer (pH 5.2) at 50°C for 12h.
The preparation method according to claim 1, wherein the types of the amylase are: one or more of high temperature resistant α-amylase, medium temperature α-amylase and β-amylase.