A low-GI kudzu starch, its preparation method and application

Abstract

The present invention belongs to the technical field of the food industry, and particularly relates to a low-GI kudzu starch and a preparation method thereof. The raw materials include: flower tea extract and gelatinized kudzu starch. The present invention uses the flower tea extract and the gelatinized kudzu starch as raw materials, and through the interaction of hydrogen bonds or van der Waals forces, the structure and functional flower tea factors of the gelatinized macromolecular starch are self-assembled and reconstructed, preferably assembled to form a V-type complex, which increases the content of resistant starch, thereby forming low-GI starch. The low-GI kudzu starch provided by the present invention can be used as the main raw material in the development and production of products such as low-GI pasta, pastries, and solid beverages, and can also be used as a functional food or meal replacement food ingredient for obese and diabetic patients, expanding the application scope of kudzu starch.

Description

Technical Field

[0001] The present invention belongs to the technical field of food industry, and particularly relates to a low-GI kudzu starch and a preparation method thereof. Background Art

[0002] Starch is a major food component, a source of blood sugar carbohydrates and an essential energy for human daily life. Kudzu (Pueraria lobata var. thomsonii) is a plant of the genus Pueraria in the legume family. Kudzu is used as medicine with its root, and its Chinese medicine name is Gegen. The starch content of kudzu can reach 98.6%, the amylose content is about 22.2% - 30.3%, and the flavonoid content is 0.18 - 2.28 mg / g. Due to the special food and medicine value of kudzu starch, it is a commonly used healthy food material in China, Japan and other Southeast Asian countries and may become a natural main source of edible starch. However, because the original kudzu starch is digested and absorbed quickly, especially the content of rapidly digestible starch is high, it belongs to high-GI food and is likely to cause too rapid increase in blood sugar, which restricts the development of the kudzu starch industry. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a low-GI kudzu starch, a preparation method and an application thereof. The low-GI kudzu starch is obtained by self-assembling and reconstructing the starch structure through physical action using flower tea extract and gelatinized kudzu starch, and the prepared low-GI kudzu starch can be applied to the preparation of low-GI foods.

[0004] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a low-GI kudzu starch, and the raw materials of the low-GI kudzu starch include: flower tea extract and gelatinized kudzu starch.

[0006] Preferably, the added mass of the flower tea extract is 5% - 20% of the added mass of the original kudzu starch.

[0007] Preferably, the raw materials of the flower tea extract include: one or more of sophora japonica, lonicera confusa, lonicera japonica, golden camellia and momordica grosvenori flower.

[0008] The present invention provides a preparation method of the above low-GI kudzu starch, including the following steps:

[0009] Extract the flower tea raw materials with an organic solution to obtain the flower tea extract;

[0010] Gelatinize the kudzu starch to obtain gelatinized kudzu starch;

[0011] Mix the flower tea extract and the gelatinized kudzu starch to obtain the low-GI kudzu starch.

[0012] Preferably, the number of extractions is not less than 2 times, the extraction time for each extraction is 20 - 40 min, and the temperature is 70 - 90 °C.

[0013] Preferably, the gelatinization time is 0.5 - 2 h, and the temperature is 70 - 90 °C.

[0014] Preferably, the addition rate during mixing is 1.0 - 3.0 mL / min.

[0015] The present invention provides the application of the above-mentioned low - GI kudzu starch or the low - GI kudzu starch prepared by the above - mentioned preparation method in the preparation of low - GI foods.

[0016] Preferably, the types of the foods include ordinary foods, functional foods or meal replacement foods.

[0017] Preferably, the types of the foods include pasta, pastries and solid beverages.

[0018] Beneficial effects: The present invention provides a low - GI kudzu starch, which mainly selects flower tea extract and gelatinized kudzu starch to self - assemble and reconstruct the starch structure through physical action to obtain the low - GI kudzu starch. The GI value of the low - GI kudzu starch of the present invention is 45 - 53, belonging to a low - GI food.

[0019] The present invention provides a preparation method of the above - mentioned low - GI kudzu starch. Using flower tea extract and gelatinized kudzu starch as raw materials, through the interaction of hydrogen bonds or van der Waals forces during mixing, the gelatinized macromolecular starch structure and functional flower tea factors self - assemble and reconstruct to obtain a gelatinized kudzu starch complex, thereby enhancing the anti - digestibility of the gelatinized starch and achieving the purpose of low GI. The preparation method provided by the present invention has a simple process, does not require complex chemical modification, is green and safe, and can significantly reduce the digestibility of starch, thus achieving the purpose of low GI.

[0020] The present invention also provides the application of the above - mentioned low - GI kudzu starch. The low - GI kudzu starch can be used as the main raw material in the development and production of products such as low - GI pasta, pastries, solid beverages, etc., and can also be used as an ingredient in functional foods or meal replacement foods for obese and diabetic patients, expanding the application range of kudzu starch. Description of the Drawings

[0021] Figure 1 It is a comparative diagram of the digestion and hydrolysis curves of the original kudzu starch and the low - GI kudzu starch;

[0022] Figure 2 It is an HPLC diagram of the main chemical components of the low - GI kudzu starch;

[0023] Figure 3 It is the X - ray diffraction of the low - GI kudzu starch;

[0024] Figure 4 It is the Fourier infrared spectroscopy analysis diagram of low-GI kudzu starch. Specific implementation mode

[0025] The present invention provides a low-GI kudzu starch, and the raw materials of the low-GI kudzu starch include: flower tea extract and gelatinized kudzu starch. In the present invention, the preferred added mass of the flower tea extract is 5% - 20% of the added mass of the kudzu starch, and more preferably 10 - 15%. The present invention has no special limitation on the source of the kudzu starch raw material, and conventional commercially available products can be used. The present invention uses flower tea extract and gelatinized kudzu starch as raw materials, and through the interaction of hydrogen bonds or van der Waals forces, the gelatinized macromolecular starch structure and functional flower tea factors are self-assembled and reconstructed. Conventional means mainly use monomer compounds for the composite preparation of RS5-type resistant starch, while the present invention uses flower tea extract and gelatinized kudzu starch for preferred assembly to form a V-type complex. The guest enters the inner cavity of the starch main body through hydrophobic interaction to form a complex, increasing the content of resistant starch, thereby forming low-GI starch. In the specific implementation mode of the present invention, the assembly of flower tea extract and gelatinized kudzu starch to form a V-type complex is verified.

[0026] The raw materials of the flower tea extract in the present invention are preferably flower teas that are both medicine and food, and more preferably include one or more of sophora flower, honeysuckle flower, Lonicera japonica, camellia nitidissima, and momordica grosvenori flower. The present invention has no special limitation on the source of the raw materials, and conventional commercially available products can be used. The extraction solution of the flower tea extract in the present invention is preferably an edible organic solution, and the edible organic solution preferably includes one or more of ethanol, acetic acid, glycerol, or vegetable oil, and more preferably ethanol. The edible organic solvent can efficiently extract the small molecule functional substances in the flower tea. When the extraction solution is an ethanol aqueous solution in the present invention, the volume concentration of the ethanol aqueous solution is preferably 30% - 80%, more preferably 40% - 60%, and most preferably 50%. The mass-volume ratio of the flower tea raw materials and the edible organic solution in the present invention is preferably 1g:5 - 20mL, more preferably 1g:5 - 15mL, and most preferably 1g:10mL. The small molecule functional substances of the flower tea extract in the present invention form an inclusive or non-inclusive complex with the helical structure opened by the amylose after the starch is gelatinized or the loose branched starch through physical action. This complex has an inhibitory effect on the enzymatic hydrolysis of amylase, and thus low-GI kudzu starch is obtained.

[0027] The present invention provides a preparation method of the above low-GI kudzu starch, including the following steps:

[0028] Extract the flower tea raw materials with an organic solution to obtain a flower tea extract;

[0029] Gelatinize the kudzu starch to obtain gelatinized kudzu starch;

[0030] Mix the flower tea extract and gelatinized kudzu starch to obtain low-GI kudzu starch.

[0031] In the present invention, the flower tea raw material is extracted with an organic solution, and the supernatant is taken by centrifugation to obtain the flower tea extract. The number of times of extraction in the present invention is preferably not less than 2 times, more preferably 2 - 4 times, and even more preferably 3 times. The time for single extraction is preferably 20 - 40 min, more preferably 25 - 35 min, and even more preferably 30 min. The extraction temperature is preferably 70 - 90 °C, more preferably 75 - 85 °C, and most preferably 80 °C. The extraction method in the present invention is preferably ultrasonic extraction. When ultrasonic extraction is selected, the ultrasonic power is preferably 200 - 500 W, more preferably 300 - 400 W, and most preferably 360 W. Ultrasonic-assisted extraction can improve the extraction efficiency of small molecular substances in the flower tea. In the specific implementation manner of the present invention, HPLC analysis was performed on the identification of the efficacy substances in the flower tea extract and the construction of the low-GI complex.

[0032] In the present invention, the kudzu starch is mixed with water and heated for gelatinization to obtain gelatinized kudzu starch. The time for gelatinization in the present invention is preferably 0.5 - 2 h, more preferably 0.5 - 1.5 h, and most preferably 1 h. The temperature for gelatinization is preferably 70 - 90 °C, more preferably 75 - 85 °C, and most preferably 80 °C. Gelatinization treatment is beneficial to the opening of the helical structure of starch. This was verified in the specific implementation manner of the present invention, and the XRD analysis of the starch structure after gelatinization showed a decrease in the degree of order. The gelatinization method in the present invention is preferably ultrasonic. When ultrasonic is selected, the ultrasonic power is preferably 200 - 500 W, more preferably 300 - 400 W, and most preferably 360 W. Ultrasonic-assisted gelatinization can improve the gelatinization efficiency, and the gelatinized kudzu starch obtained by ultrasonic has a more uniform and stable texture.

[0033] The flower tea extract obtained above and the gelatinized kudzu starch are mixed in the present invention to obtain low-GI kudzu starch. When mixing in the present invention, the addition rate of the flower tea extract is preferably 1.0-3.0 mL / min, more preferably 1.5-2.5 mL / min, and most preferably 2.0 mL / min. The mixing temperature in the present invention is preferably 70-90 °C, more preferably 75-85 °C, and even more preferably 80 °C. When the starch is mixed, the temperature is relatively high, and after cooling and retrogradation, the RS3-type resistant starch structure is formed. RS3 is retrograded and aged starch, which has certain slow digestion characteristics, and its resistance is unstable. In the present invention, the flower tea extract and the gelatinized kudzu starch are mixed, and part of the starch forms the RS5-type starch structure by physical combination of the guest and host molecules. It is mixed with the remaining RS3-type resistant starch structure that has not undergone structural transformation, and the obtained resistant starch forms the characteristics of two types of resistant starches, RS3 and RS5. The obtained low-GI kudzu starch is a self-assembled starch type V complex, making the resistance of the prepared low-GI kudzu starch more stable. The mixing method in the present invention is preferably ultrasonic mixing. When ultrasonic mixing is selected, the ultrasonic power is preferably 100-400 W, more preferably 200-300 W, and most preferably 240 W. Using low-power ultrasonic treatment can make the structure of the starch looser, the mixing more uniform, and the resistance of the obtained low-GI kudzu starch more stable. After mixing in the present invention, it is preferably further included to cool the mixture to room temperature, and then continue to carry out stirring treatment. The stirring time is preferably 0.5-2 h, more preferably 1 h, and the stirring speed is preferably 100-300 r / min, more preferably 100-200 r / min, and most preferably 150 r / min. After stirring in the present invention, it is preferably further included to stand at a low temperature. The temperature of the low-temperature standing is preferably 0-25 °C, more preferably 0-15 °C, further preferably 4-8 °C, and most preferably 4 °C. The standing time is preferably 10-20 h, more preferably 10-15 h, and most preferably 12 h. Standing can make the starch precipitate, which is beneficial for subsequent drying treatment. In the present invention, it is preferably to dry the starch obtained by standing. The drying time is preferably 24-48 h, more preferably 36 h. Drying and dehydrating the low-GI kudzu starch is beneficial for storage. The drying method in the present invention is preferably freeze-drying or hot air drying. When freeze-drying is selected, the temperature of the freeze-drying is preferably -80 °C. When hot air drying is preferably selected, the temperature of the hot air drying is preferably 50 °C.

[0034] The present invention also provides the application of the above low-GI kudzu starch or the low-GI kudzu starch prepared by the above preparation method in the preparation of low-GI foods. The GI value of the low-GI kudzu starch obtained in the present invention is 45-53, which belongs to a low-GI food and has a certain control effect on postprandial blood glucose and can be used to prepare low-GI foods. The types of foods in the present invention include ordinary foods, functional foods or meal replacement foods. The types of foods in the present invention include pasta, pastries and solid beverages.

[0035] To further illustrate the present invention, a low-GI kudzu starch and its preparation method and application provided by the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1

[0037] A raw material for low-GI kudzu starch is flower tea extract and gelatinized kudzu starch.

[0038] The preparation steps of the low-GI kudzu starch are as follows:

[0039] (1) The raw material of the flower tea extract is sophora japonica. Preparation of the extract: Weigh 10 g of sophora japonica, add it to 100.0 mL of 50% ethanol solution, perform single ultrasonic extraction for 30 min, the ultrasonic temperature is 80 °C, the ultrasonic power is 360 W, after ultrasonic treatment, centrifuge at 4000 r / min for 20 min, collect 100 mL of the supernatant, and repeat the above steps 3 times. Combine the supernatants collected three times above, concentrate at 40 °C, and then freeze-dry to obtain sophora japonica extract powder.

[0040] (2) Weigh 100 g of commercially available kudzu starch (produced in Guangxi), disperse it in 2000 mL of water, stir evenly, and heat it in an ultrasonic boiling water bath for 30 min, the ultrasonic temperature is 80 °C, the ultrasonic power is 360 W, to obtain gelatinized kudzu starch.

[0041] (3) Weigh 20 g of sophora japonica extract powder (accounting for 20% of the original starch mass), dissolve it in 50% ethanol to prepare a 100 mL sophora japonica extract solution with a concentration of 0.2 g / mL. Add 100 mL of the sophora japonica extract solution to the gelatinized kudzu starch, the addition rate is 2.0 ml / min, perform ultrasonic treatment for 50 min, the ultrasonic power is 240, the ultrasonic temperature is 80 °C, and perform self-assembly and reconstruction treatment. Then stir at room temperature for 0.5 h, refrigerate at 4 °C for 24 h, centrifuge at 4000 r / min for 20 min, dry at 60 °C for 36 h, pulverize, and pass through a 100-mesh sieve to obtain low-GI kudzu starch.

[0042] Example 2

[0043] It is carried out in the same manner as in Example 1, except that the raw material of the flower tea extract is lonicera confusa.

[0044] Example 3

[0045] It is carried out in the same manner as in Example 1, except that the raw material of the flower tea extract is lonicera japonica.

[0046] Example 4

[0047] It is carried out in the same manner as in Example 1, except that the raw material of the flower tea extract is camellia nitidissima.

[0048] Example 5

[0049] It is carried out in the same manner as in Example 1, except that the raw material of the flower tea extract is Momordica grosvenori flower.

[0050] Comparative Example 1

[0051] It is carried out in the same manner as in Example 1, except that the flower tea extract is replaced with ethanol.

[0052] Comparative Example 2

[0053] Directly dry the commercially available kudzu starch (produced in Guangxi) at 60 °C for 36 hours and pass through a 100-mesh sieve.

[0054] Comparative Example 3

[0055] It is carried out in the same manner as in Example 1, except that the addition rate in step (3) is 4.0 ml / min.

[0056] Comparative Example 4

[0057] It is carried out in the same manner as in Example 1, except that the ultrasonic temperature in step (3) is 60 °C.

[0058] Comparative Example 5

[0059] It is carried out in the same manner as in Example 2, except that the added mass of the flower tea extract in step (3) is 3% of the added mass of the original kudzu starch.

[0060] Test Example 1

[0061] Determination method of in vitro digestion and GI of starch:

[0062] Weigh 100 mg of the sample and dissolve it in 10 mL of acetic acid buffer solution with pH = 5.3, mix well for 5 min, place it in a boiling water bath for 30 min, then cool it to 37 °C, add 5 mL of enzyme solution (α-amylase and glucoamylase), and respectively draw 1 mL of the reaction sample solution into a centrifuge tube at 10, 20, 30, 45, 60, 120, and 180 min after enzymatic hydrolysis, and immediately add 9 mL of ethanol solution to inactivate the enzyme. Place the mixed solution in a centrifuge and centrifuge it at 3500 rpm for 20 min. Then take 1 mL of the supernatant into a 10 mL test tube, add 1 mL of DNS reagent, place the test tube in a boiling water bath for color reaction for 6 min, completely cool it, add 9 mL of pure water and mix well, and measure its absorbance value at a wavelength of 540 nm.

[0063] Draw a starch digestion and hydrolysis curve according to the digestion rate at different time points, and the curve can be expressed by C = C ∞ (1–e -kt ) where C refers to the hydrolysis rate of the sample at hydrolysis time t, C∞ refers to the equilibrium concentration at the final hydrolysis time, k refers to the kinetic constant, and t refers to the hydrolysis time.

[0064] Hydrolysis Index (HI) = Area under the digestion hydrolysis curve of the test sample / Area of the control sample (i.e., white bread).

[0065] Finally, according to GI = 8.198 + (0.862 × HI), the GI value is calculated.

[0066] Using the method of Test Example 1, the digestibility of Examples 1 - 5 and Comparative Examples 1 - 2 was used to plot the starch digestion hydrolysis curve, and the results are shown in Figure 1 . It can be seen from the figure that the digestion hydrolysis values of Examples 1 - 5 are significantly lower than those of Comparative Examples 1 - 2.

[0067] The GI values of Examples 1 - 5 and Comparative Examples 1 - 2 were tested, and the results are shown in Table 1.

[0068] Table 1 GI values of Pueraria thomsonii starch prepared by different methods

[0069]

[0070]

[0071] It can be seen from the table that the GI value of the Pueraria thomsonii starch prepared in Example 1 is 44, that in Example 2 is 45, that in Example 3 is 48, that in Example 4 is 48, that in Example 5 is 53, that in Comparative Example 1 is 74, and that in Comparative Example 2 is 88. The Chinese health industry standard stipulates that GI ≤ 55 is a low - GI food, 55 ≤ GI ≤ 70 is a medium - GI food, and GI > 70 is a high - GI food (Reference: WS / T 652 - 2019 Determination method for glycemic index of foods). It can be seen that the Pueraria thomsonii starch prepared in Examples 2 - 6 all belong to low - GI foods, and the Pueraria thomsonii starch prepared in Comparative Examples 1 - 2 all belong to high - GI foods. In Comparative Document 1, the Pueraria thomsonii starch prepared by replacing the flower tea extract with ethanol and omitting the flower tea raw material has a significantly higher GI value. In Comparative Example 2, only the Pueraria thomsonii starch is gelatinized, and the obtained GI value is also high.

[0072] In Comparative Example 3, the addition speed of the flower tea extract was increased. In Comparative Example 4, the temperature of ultrasonic mixing of the flower tea extract and gelatinized Pueraria thomsonii starch was decreased. In Comparative Example 5, the proportion of the added mass of the flower tea extract in the added mass of the original Pueraria thomsonii starch was decreased. The obtained GI values of the mixed starches are all > 55 and do not belong to low - GI value foods.

[0073] It can be seen from this that when the flower tea extract is mixed with gelatinized Pueraria thomsonii starch, the active ingredients in the flower tea extract can slow down the digestion rate of the original Pueraria thomsonii starch and can significantly reduce the GI value of the Pueraria thomsonii starch.

[0074] Test Example 2

[0075] The kudzu starch samples prepared in Examples 1-5 and Comparative Examples 1-2 were analyzed by HPLC. The components in the low-GI self-assembled kudzu starch obtained by mixing the efficacy substances of flower tea and gelatinized kudzu starch were analyzed. The results are shown in Figure 2 .

[0076] As can be seen from the figure, rutin, quercetin, rhamnetin, chlorogenic acid, isochlorogenic acid, quercitrin, etc. are the main components of the efficacy substances of flower tea entering the starch.

[0077] Test Example 3

[0078] The structural characterization analysis of Fourier transform infrared spectroscopy and X-ray diffraction was carried out on the kudzu starch samples prepared in Examples 1-5 and Comparative Examples 1-2. The results are shown in Figure 3 and Figure 4 .

[0079] As can be seen from the figure, no new functional groups appeared in the Fourier transform infrared spectroscopy, indicating that the binding of the efficacy small molecules of the flower tea extract to the starch is a non-covalent physical interaction. At the same time, the starch samples had obvious diffraction peaks at 15.0°, 17.0°, 18.0° and 23.0°, which were of A-type crystal structure. The composite had an obvious diffraction peak at 20.6°, which was of V-type crystal structure. It can be seen that X-ray diffraction showed that the low-GI kudzu starch was transformed from A-type structure to V-type structure.

[0080] It can be seen from this that the present invention uses the flower tea extract to allow the gelatinized kudzu starch to be preferably assembled according to its own structural characteristics to form a V-type composite. From the digestion characteristics results, it can be seen that low-GI starch is formed. The present invention selects the flower tea extract and gelatinized kudzu starch to self-assemble and reconstruct the starch structure through physical action to obtain low-GI kudzu starch. The GI value of the low-GI kudzu starch described in the present invention is 45-53, which belongs to a low-GI food and can significantly reduce the digestibility of starch, so as to achieve the purpose of low GI and can be applied to the preparation of low-GI foods.

[0081] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments according to these embodiments without creative efforts, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A low-GI kudzu starch, characterized in that, The raw materials of the low-GI kudzu starch include: flower tea extract and gelatinized kudzu starch; Extract the flower tea raw materials with an organic solution to obtain the flower tea extract; mix the flower tea extract and the gelatinized kudzu starch to obtain the low-GI kudzu starch; The temperature of the mixing is 70-90 °C; the addition rate of the flower tea extract during mixing is 1.0-3.0 mL / min; The added mass of the flower tea extract is 5%-20% of the added mass of the original kudzu starch; The raw materials of the flower tea extract include one or more of sophora japonica, lonicera confusa, lonicera japonica, camellia nitidissima, and momordica grosvenori flower; The organic solution is an ethanol aqueous solution with a volume concentration of 30%-80%.

2. The low-GI kudzu starch according to claim 1, characterized in that, The main components of the flower tea extract entering the starch are rutin, quercetin, rhamnetin, chlorogenic acid, isochlorogenic acid, and quercitrin.

3. The preparation method of the low-GI kudzu starch according to claim 1 or 2, characterized in that, It includes the following steps: Extract the flower tea raw materials with an organic solution to obtain the flower tea extract; the number of extractions is 2-4 times, and the single extraction time is 20-40 min; Gelatinize the kudzu starch to obtain gelatinized kudzu starch; Mix the flower tea extract and the gelatinized kudzu starch to obtain the low-GI kudzu starch; The temperature of the mixing is 70-90 °C; the addition rate of the flower tea extract during mixing is 1.0-3.0 mL / min.

4. The preparation method according to claim 3, wherein The temperature of the extraction is 70-90 °C.

5. The preparation method according to claim 3, characterized in that, The gelatinization time is 0.5-2 h, and the temperature is 70-90 °C.

6. The application of the low-GI kudzu starch according to claim 1 or 2 or the low-GI kudzu starch prepared by the preparation method according to any one of claims 3-5 in the preparation of low-GI foods.

7. The application according to claim 6, characterized in that, The types of the foods include ordinary foods, functional foods, or meal replacement foods.

8. The application according to claim 6, characterized in that, The types of the foods include pasta, pastries, and solid beverages.

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