A method for reducing starch digestibility by a cactus soluble dietary fiber and its use in low gi food

Abstract

The present application provides a method for reducing starch digestion rate by cactus soluble dietary fiber and its application in low GI food, wherein the cactus soluble dietary fiber is added into starch system, and the addition amount of the cactus soluble dietary fiber in the starch system is 0.5-2 mg·mL ‑1 The present application can reduce the gelatinization degree of potato starch by cactus soluble dietary fiber by changing the hydrogen bond network of water, and form a complex with potato starch; the cactus soluble dietary fiber can reduce the activity of starch glucosidase and the catalytic efficiency; the cactus soluble dietary fiber can inhibit glucose diffusion and reduce the rate of blood sugar rise.

Description

Technical Field

[0001] This invention relates to the field of food technology, and in particular to a method for reducing starch digestibility with cactus soluble dietary fiber and its application in low-GI foods. Background Technology

[0002] Starch, an abundant polysaccharide in the plant kingdom, possesses renewable and biodegradable properties, playing a crucial role in the food industry. During food production and storage, the gelatinization and retrogradation of starch significantly impact the texture, flavor, digestibility, and functional properties of starchy foods. Simultaneously, rapidly digested starchy carbohydrates lead to a rapid spike in postprandial blood glucose levels. Prolonged postprandial hyperglycemia can easily trigger abnormal insulin secretion, thereby inducing chronic diseases such as type 2 diabetes and cardiovascular disease.

[0003] Based on their digestibility, starches can be classified into three categories: rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). RDS refers to starch that is completely digested and absorbed in the small intestine, SDS refers to starch that is completely digested and absorbed in the small intestine within 20–120 minutes, and resistant starch refers to starch that cannot be digested and absorbed by the small intestine even after 120 minutes. Resistant starch plays an important role in regulating blood sugar, lowering blood lipids, promoting mineral absorption, and protecting the intestinal tract. Therefore, reducing starch digestibility to produce more resistant starch is crucial. Currently, there are three main methods for preparing resistant starch: physical modification, chemical modification, and enzymatic modification. Physical and chemical modifications suffer from problems such as numerous byproducts, low production efficiency, and poor safety. Enzymatic reactions require stringent conditions, are costly, and are less efficient than chemical or physical methods. Therefore, a green, safe method that can reduce starch digestibility is still needed to improve the production efficiency of resistant starch.

[0004] Studies have shown that by combining non-starch polysaccharides with starch, and utilizing the natural properties of the non-starch polysaccharides and their interaction with starch, it is possible to reduce starch digestibility. Cacti, due to their unique physiological characteristics and multifunctionality, have important applications in ecology, nutrition, medicine, and industry. However, research on the interaction between cactus soluble dietary fiber (WOPP) and starch, and its impact on starch properties, is rarely reported. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for reducing starch digestibility using cactus soluble dietary fiber and its application in low-GI foods, in order to solve the problems of excessive by-products, low production efficiency, poor safety, harsh enzymatic reaction conditions, high cost and low efficiency in existing chemical or physical preparation methods of resistant starch.

[0006] To achieve the above and other related objectives, this invention provides a method for reducing starch digestibility using cactus soluble dietary fiber, characterized in that cactus soluble dietary fiber is added to a starch system, wherein the amount of cactus soluble dietary fiber added to the starch system is 0.5~2 mg·mL. -1 .

[0007] Preferably, the starch system includes potato starch.

[0008] Preferably, the soluble dietary fiber content of the cactus soluble dietary fiber is 0.5~5 mg·mL. -1 .

[0009] Preferably, the cactus soluble dietary fiber is prepared by a method comprising the following steps:

[0010] (1) Wash, cut, dry, crush, and sieve the cactus leaves to obtain cactus powder;

[0011] (2) Take cactus powder, add water, heat to extract, cool, centrifuge to get the supernatant, filter residue to extract repeatedly, centrifuge and combine the supernatants;

[0012] (3) Add ethanol to the supernatant, mix well, let stand, filter and collect the precipitate, freeze dry and then reconstitute, dialyze, concentrate under reduced pressure, freeze dry, and obtain cactus soluble dietary fiber.

[0013] Preferably, in step (1), the cactus leaf is a six-month-old Opuntia ficus-indica leaf.

[0014] Preferably, in step (1), the sieving is performed through an 800-mesh sieve.

[0015] Preferably, in step (2), the mass-to-volume ratio of the cactus powder to water is (10~15) g: 1 L.

[0016] Preferably, in step (2), the heating extraction temperature is 80~100℃ and the time is 0.5~1.5h.

[0017] Preferably, in step (2), the filter residue is extracted at least twice.

[0018] Preferably, in step (3), the volume ratio of the supernatant to ethanol is 1:(3~5).

[0019] Preferably, in step (3), a 3000 Da dialysis bag is used for dialysis.

[0020] Preferably, in step (3), the dialysis time is 48~72 h.

[0021] The present invention also provides a method for improving the physicochemical properties of potato starch by adding cactus soluble dietary fiber to potato starch.

[0022] Preferably, the physicochemical properties include one or more of expansion, gelatinization temperature, and viscosity.

[0023] The present invention also provides a low-digestibility potato starch compound composition comprising potato starch and cactus soluble dietary fiber.

[0024] Preferably, the mass ratio of potato starch to cactus soluble dietary fiber is 10:(1~5).

[0025] The present invention also provides a method for preparing a low-digestibility potato starch compound composition, wherein potato starch and cactus soluble dietary fiber are mixed evenly by a wet method and freeze-dried to obtain the low-digestibility potato starch compound composition.

[0026] Preferably, the freeze-drying temperature is -25 to -15°C, and the freeze-drying time is 12 to 48 hours.

[0027] This invention also provides an application of cactus soluble dietary fiber in the preparation of low-GI foods.

[0028] As described above, the present invention has the following beneficial effects:

[0029] (1) The present invention uses experiments to measure the in vitro digestibility of potato starch with different amounts of cactus soluble dietary fiber, and calculates the changes in starch content and the inhibition rate of cactus soluble dietary fiber on amyloglucosidase activity. It is found that the digestibility of the compound system of cactus soluble dietary fiber and potato starch is reduced and the anti-digestion components are increased. The prepared compound system has low GI and low digestibility characteristics.

[0030] (2) In this invention, the soluble dietary fiber of cactus reduces the gelatinization degree of potato starch by changing the hydrogen bond network of water and forms a complex with potato starch.

[0031] (3) The present invention utilizes the soluble dietary fiber of cactus to reduce the activity of amylase and decrease the catalytic efficiency;

[0032] (4) The present invention inhibits glucose diffusion and reduces the rate of blood sugar rise by using soluble dietary fiber from cactus. Attached Figure Description

[0033] Figure 1 SEM images of potato starch are shown: (a) magnification × 200; (b) magnification × 1000.

[0034] Figure 2 SEM images showing soluble dietary fiber in cactus: (a) magnification × 200; (b) magnification × 1000.

[0035] Figure 3 SEM images of the potato starch compound composition of Example 2 are shown: (a) magnification × 200. (b) magnification × 1000.

[0036] Figure 4 The image shows the gelatinization curves of potato starch containing different concentrations of cactus soluble dietary fiber.

[0037] Figure 5 The effects of WOPP on POS in vitro digestion are shown as follows: (a) starch digestibility; (b) starch content; (c) SDS+RS ratio; (d) area under the starch digestion line (AUC).

[0038] Figure 6 The digestion curves shown as POS (first-order kinetic fit) are: (a) without WOPP; (b)-(f) with WOPP (1-5 mg / mL). -1 ).

[0039] Figure 7 The curves shown are logarithmic fits to the POS digestion slope: (a) without WOPP; (b)-(f) with WOPP (1-5 mg / mL). -1 ).

[0040] Figure 8 The kinetic models of CPS digestion shown for POS are (a) without WOPP addition; (b)-(f) with WOPP (1-5 mg / mL). -1 ).

[0041] Figure 9 Show the biphase separation point (t2start) with and without WOPP.

[0042] Figure 10 The data are shown as the glucose diffusion delay index (a) and glucose adsorption amount (b) during in vitro intestinal digestion of WOPP-Pos.

[0043] Figure 11 The inhibition rates of WOPP and acarbose on ASP are shown in (a) and the Lineweaver-Burk plot of WOPP's inhibition of ASP is shown in (b). Detailed Implementation

[0044] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0045] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

[0046] Currently, there is limited research on the mechanism and effects of the interaction between potato starch and cactus soluble dietary fiber composite systems in the food industry. This invention provides a theoretical basis for the application of starch polysaccharide and non-starch dietary fiber composite systems in the food industry by studying the morphological characteristics, crystal structure, thermodynamic properties and rheological properties of the composite system.

[0047] In the following embodiments of this application, the abbreviations mean: POS stands for potato starch and WOPP stands for cactus soluble dietary fiber.

[0048] The method for preparing soluble dietary fiber from cactus in the following embodiments of this application includes the following steps:

[0049] (1) Wash, cut and dry the leaves of half-year-old Opuntia ficus-indica, crush them in a pulverizer and pass them through an 800-mesh sieve to obtain cactus powder.

[0050] (2) Take 200 g of the cactus powder obtained in the previous step, add 16 L of water, extract at 80℃ for 1 h, cool to room temperature, centrifuge to collect the supernatant, repeat the extraction twice with the residue, and combine the supernatants after centrifugation. Add 95% ethanol at a supernatant volume ratio of 1:4, mix well, let stand for 24 h, filter to collect the precipitate, freeze dry and reconstitute, dispense into 3000 Da dialysis bags and dialyze for 72 h, concentrate under reduced pressure, and freeze dry to obtain soluble dietary fiber from Opuntia ficus-indica, with a yield of 8.50 ± 0.41%.

[0051] Using glucose as a reference standard, the polysaccharide content in MAP-1 to MAP-6 was determined using the phenol-sulfuric acid method. 0.4 mL of MAP-1 to MAP-6 solutions were transferred to test tubes, and distilled water was added to bring the volume to 0.5 mL. After mixing, 0.3 mL of 6% phenol solution was added to each tube, followed by a rapid addition of 1.5 mL of concentrated sulfuric acid. The mixture was immediately shaken well, then heated in a boiling water bath for 30 min. After cooling naturally to room temperature, the A490 value was measured at a wavelength of 490 nm, and the total sugar content of the *Opuntia ficus-indica* cactus was calculated.

[0052] Protein content was determined using the Coomassie Brilliant Blue method.

[0053] Preparation of reagents: ① Accurately weigh 20 mg of bovine serum albumin (BSA) and dilute to 200 mL of distilled water to obtain 0.1 mg / mL. -1 Bovine serum albumin solution; take 100 mg of Coomassie Brilliant Blue G-250, dissolve it in 50 mL of ethanol (95%), then add 100 mL of phosphate solution (85%), and finally dilute with distilled water to 1000 mL to obtain 0.1 mg / mL. -1 Coomassie Brilliant Blue G-250 solution.

[0054] Plotting the standard curve: Pipette 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL of the prepared BSA solution into colorimetric tubes, and bring the volume up to 1 mL with distilled water. Then add 5 mL of Coomassie brilliant blue solution to each tube, mix well, and let stand at room temperature for 10 min. Measure the absorbance at 595 nm.

[0055] Determination of protein content in samples: Prepare 1 mg / mL solution -1 Take 1 mL of each sample solution and perform the above steps to calculate the protein content in the sample.

[0056] The protein content in WOPP was determined using the Coomassie Brilliant Blue G-250 method with bovine serum albumin as the standard. 1 mL of 0.1 mg / mL protein was used. -1 Add 5 mL of Coomassie Brilliant Blue G-250 solution to the cactus polysaccharide solution in a test tube, let it stand in the dark for 10 min, and immediately measure the A595 value at 595 nm to calculate the protein content in the cactus polysaccharide.

[0057] Determination of uronic acid content

[0058] Using glucuronic acid as a control, the uronic acid content was determined by the carbazole-sulfuric acid method, with slight modifications. Take 200 μL of 0.1 mg / mL... -1A cactus polysaccharide sample solution was prepared by adding 5 mL of sodium tetraborate-sulfuric acid solution to an ice-water bath, vortexing, and then incubating in a boiling water bath for 20 min. After removal, the solution was immediately cooled to room temperature. 0.2 mL of 0.15% carbazole solution was added, and the mixture was shaken well. The reaction was allowed to proceed at room temperature for 2 h, and the A523 value was measured at 523 nm. The content was calculated.

[0059] Determination of total sugar content

[0060] The phenol-sulfuric acid method was used.

[0061] Plotting the standard curve: Prepare a 0.1 mg·mL⁻¹ standard curve. -1 Glucose standard solution (prepared by drying in a 105℃ drying oven for 2 hours to constant weight). Take 0, 0.2, 0.4, 0.6, 0.8, 1 and 1.2 mL of the standard solution and place them into 10 mL colorimetric tubes. Make up the volume of each tube to 2 mL with distilled water. Then add 1 mL of 6% phenol solution and 5 mL of concentrated sulfuric acid to each tube in sequence. Stopper the tubes, let them stand for 10 min, then boil them in a water bath for 30 min. After cooling to room temperature, measure the absorbance of each tube at a wavelength of 490 nm and plot the glucose standard curve.

[0062] Determination of total sugar content in the sample: Prepare 0.1 mg / mL solution. -1 Take 1 mL of WOPP and perform the above steps to test it, then calculate the total sugar content in the sample.

[0063] Table 1 shows the basic components of soluble dietary fiber (WOPP) from cactus:

[0064] Table 1. Basic Components of WOPP .

[0065] The preparation method of the low-digestibility potato starch compound composition in the following embodiments of this application includes the following steps: potato starch and cactus soluble dietary fiber are mixed evenly by water-wetting method, and freeze-dried at -20℃ for 24h to obtain the low-digestibility potato starch compound composition.

[0066] Example 1

[0067] This application also provides a low-digestibility potato starch compound composition comprising 10 parts potato starch and 1 part cactus soluble dietary fiber.

[0068] Example 2

[0069] This application also provides a low-digestibility potato starch compound composition comprising 10 parts potato starch and 2 parts cactus soluble dietary fiber.

[0070] Example 3

[0071] This application also provides a low-digestibility potato starch compound composition comprising 10 parts potato starch and 3 parts cactus soluble dietary fiber.

[0072] Example 4

[0073] This application also provides a low-digestibility potato starch compound composition comprising 10 parts potato starch and 4 parts cactus soluble dietary fiber.

[0074] Example 5

[0075] This application also provides a low-digestibility potato starch compound composition comprising 10 parts potato starch and 5 parts cactus soluble dietary fiber.

[0076] The microstructure of the cogelatinized products of potato starch (POS), cactus soluble dietary fiber (WOPP), and the potato starch compound prepared in Example 2 was characterized by scanning electron microscopy (SEM), as follows:

[0077] Potato starch (POS), cactus soluble dietary fiber (WOPP), and the potato starch compound prepared in Example 2 were freeze-dried and processed into uniform small segments. The cross-sections were then mounted on a sample stage and sputter-coated with gold. The samples were magnified 200x and 1000x at an accelerating voltage of 3.0 kV to observe the microstructure of the sample cross-sections. The results are as follows: Figures 1-3 As shown.

[0078] like Figure 1 As shown, the potato starch gel images exhibit a typical porous and irregular morphology, such as... Figure 2 As shown, cactus soluble dietary fiber WOPP exhibits a fibrous structure, with these fibers interwoven to form a network structure. Figure 3 The image of the potato starch compound system shows that potato starch particles are intertwined with WOPP fibrous structures, indicating that WOPP may form a coating on the surface of potato starch particles. This may affect the digestibility of starch because such a coating may hinder the contact of digestive enzymes.

[0079] Example 6

[0080] This application provides a method for reducing the swelling degree or viscosity of potato starch. The gelatinization viscosity, gelatinization temperature, and final viscosity of the potato starch were measured using a rapid viscosity analyzer (RVA), and the measurement procedure followed the national standard GB / T24853-2010. Concentrations of 5 mg·mL⁻¹ were prepared using ultrapure water. -1The solution was the mother liquor, which was then diluted to concentrations of 0.5, 1, 2, 3, and 4 mg / mL. -1 WOPP solution. Accurately weigh 1.5 g of potato starch into an RVA test aluminum container, add 20 mL of the prepared WOPP solution, stir well, and then perform the test. The blank control is a potato sample with 20 mL of ultrapure water added. The sample is homogenized at 960 rpm. Measurement procedure: The initial temperature is set to 50°C, held for 1 min, then heated to 95°C after 4 min, held at 95°C for 3 min, and then cooled to 50°C within 4 min. The stirrer speed is maintained at 960 rpm. Finally, the gelatinization temperature, peak viscosity, valley viscosity, final viscosity, disintegration value, and retrogradation value of the sample are obtained. The results are as follows. Figure 4 As shown in Table 2:

[0081] Table 2. Gelatinization characteristics of the Pos and WOPP-Pos composite system .

[0082] *The experiment was repeated at least 3 times to obtain the mean ± standard deviation of each value. Different letters in the same column indicate significant differences (p < 0.05).

[0083] from Figure 4 As can be seen from the data, the peak viscosity decreased significantly after the addition of WOPP, and was lower than that of Pos itself. The gelatinization curves were all below those of pure Pos, indicating that the gelatinization viscosity decreased during the gelatinization process. Specific gelatinization parameters are shown in Table 2. Pos itself has a peak viscosity of 4158 cp, which is very high. The addition of WOPP reduced the peak viscosity and significantly increased the initial gelatinization temperature, indicating that WOPP inhibited the swelling of Pos powder particles. (0.5 mg·mL) -1 and 1 mg·mL - 1 WOPP reduced the disintegration and retrogradation values ​​of potato starch, indicating that within this concentration range, WOPP caused some damage to the integrity of potato starch. Adding higher concentrations of WOPP resulted in a viscosity as low as 342.67 cp, significantly leading to incomplete gelatinization. The main reason why increased WOPP content inhibits gelatinization and promotes short-term retrogradation is likely its inhibitory effect on starch granule hydration. This reduces the water required for starch granule gelatinization in the system, resulting in an overall decrease in viscosity.

[0084] Example 7

[0085] This embodiment also provides a method for improving the physicochemical properties of potato starch by adding cactus soluble dietary fiber to potato starch. The in vitro digestibility of the WOPP-potato starch compound powder was also determined.

[0086] Prepare phosphate buffer

[0087] Accurately weigh 1.7320 g of anhydrous disodium hydrogen phosphate (Na₂HPO₄) and 1.2168 g of sodium dihydrogen phosphate dihydrate (NaH₂PO₄·2H₂O), and dissolve them in an appropriate amount of ultrapure water. Stir thoroughly with a magnetic stirrer for at least 2 hours until completely dissolved, then measure the pH of the solution to 7.0. Finally, dilute to 1 L with ultrapure water to obtain a concentration of 20 mmol·L⁻¹. -1 PBS buffer.

[0088] Preparation of enzyme solution

[0089] Accurately pipette 1 mL of amylase (50 U / mL) -1 The volume was adjusted to 50 mL with PBS buffer, and the mixture was thoroughly mixed to obtain a concentration of 1 U / mL. -1 Amyloglucosidase solution.

[0090] 0.200 g porcine pancreatic α-amylase was dissolved in 4 mL of PBS, brought to a final volume of 5 mL, aliquoted, and centrifuged at 8000 rpm (4℃) for 20 min. The supernatant was then collected, and the protein concentration (6.382 mg / mL) was determined using the Coomassie Brilliant Blue method. -1 ).

[0091] Accurately weigh 0.250 g of pepsin and dissolve it in 0.01 mol·L⁻¹ solution. -1 Dilute the HCl to a final volume of 25 mL to prepare a 10 mg / mL solution. -1 Pepsin: All enzyme solutions should be stored at 4°C and prepared fresh before use.

[0092] Sample preparation

[0093] Accurately weigh a certain amount of cactus soluble dietary fiber and dissolve it in PBS buffer. Stir overnight to ensure complete dissolution, then dilute to a 25 mL volumetric flask. The final concentration of cactus soluble dietary fiber is 1 mg / mL. -1 2 mg·mL -1 3 mg·mL -1 4 mg·mL -1 5 mg·mL -1 .

[0094] In vitro digestion experiment

[0095] Weigh 0.1 g of potato starch into a black-capped bottle, add 10 mL of PBS buffer and the prepared cactus soluble dietary fiber solution, set the water bath temperature to 100 ℃ and the stirring speed to 300 rpm, and gelatinize the mixture in a boiling water bath for 15 min, then cool to 37 ℃ to obtain cogelatinized starch. Dilute the gelatinized starch solution by half and keep it at 37 ℃ with stirring for 30 min.

[0096] Place the prepared black-capped bottle containing the sample into a 37 ℃ constant temperature shaking water bath (300 rpm), and add 2 mL of simulated gastric fluid (10 mg·mL⁻¹). -1 Pepsin was used to simulate gastric digestion by shaking in a 37°C water bath for 1 h. The pH of the digest was then adjusted to 7.0, and 1 mL of a mixed enzyme solution of porcine pancreatic α-amylase and amyloglucosidase was added to each sample. The digest was then shaken in a 37°C water bath to simulate intestinal digestion for 3 h. At 0, 5, 10, 15, 20, 30, 60, 90, 120, and 180 min of intestinal digestion, individual digestion tubes were removed, and 0.1 mL of the liquid was placed in 0.9 mL of anhydrous ethanol for enzyme inactivation. The mixture was then vortexed, centrifuged at 8000 rpm, and the reducing sugar content was determined using a glucose assay kit.

[0097] Calculations and Results

[0098] Rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) were calculated. Simultaneously, a nonlinear first-order rate equation was used to fit the digestion kinetics, and the area under the starch digestion curve (AUC) was calculated using the integral method. Hydrolysis parameters and predicted glycemic index were also calculated.

[0099] Calculate the contents of rapidly digestible starch, slowly digestible starch, and resistant starch in each sample according to the following formula.

[0100]

[0101] Where: RDS—rapidly digestible starch; SDS—slowly digestible starch; RS—resistant starch; G0, G 20 and G 120 The values ​​represent the glucose content produced by starch hydrolysis at 0, 20, and 120 min, respectively.

[0102] Experimental results: such as Figure 5 As shown in (a), with the increase of WOPP concentration in the complex system, the digestion of Pos was gradually inhibited, with the highest inhibition rate reaching 23%. Furthermore, WOPP also had a certain impact on the digestible fragments of Pos: such as... Figure 5 (a) and Figure 5As shown in (c), the addition of WOPP increased the proportion of slowly digestible starch (SDS) and resistant starch (RS). Specifically, compared to the Control group, 5 mg / mL... -1 The RDS of the WOPP group decreased by 8.41%, while the RS increased by 15.81%. This shows that the addition of WOPP helps to delay the digestion of potato starch and significantly increases the proportion of resistant starch.

[0103] It is generally believed that SDS is associated with low digestibility, but the addition of WOPP reduces the content of SDS and increases the content of RS. This may be because WOPP promotes the short-term retrogradation of Pos, and the original SDS forms a dense crystalline structure, which is partially converted into RS that is difficult to be digested by enzymes.

[0104] The AUC value reflects the cumulative amount of reducing sugars produced by the hydrolysis of starch by amylase during simulated digestion in vitro. Figure 5 (d) shows the changes in AUC with and without WOPP. The AUC decreased significantly after adding WOPP, which corresponds to a decrease in the proportion of digestible starch (rapidly digestible starch RDS + slowly digestible starch SDS) and an increase in the proportion of resistant starch (RS), ultimately leading to a decrease in the total amount of hydrolysate generated during the digestion cycle.

[0105] Example 8

[0106] This embodiment provides a method for establishing a starch digestion kinetics model, including the following steps:

[0107] The first-order kinetics formula for potato starch digestion is as follows:

[0108] ;

[0109] In the formula, C t This refers to the percentage of starch hydrolyzed during digestion (t min), i.e., the starch hydrolysis rate; C ∞ The k value refers to the percentage of starch hydrolysis at hydrolysis equilibrium; the k value represents the first-order rate coefficient of starch hydrolysis (min). -1 ); t is the digestion time (min). The logarithmic slope equation (LOS) describes the linear relationship between the logarithm of the digestion rate and the digestion time. The LOS equation is obtained through transformation as follows:

[0110] ;

[0111] Introducing the CPS dynamics model:

[0112] ;

[0113] Assuming the potato starch-WOPP complex system contains two parts with different digestion processes, and the digestion process of each part can be fitted by a nonlinear first-order kinetic formula, then the digestion parameter of the first part is C. 1∞ If the second part begins to be digested at time t2start, then the digestion parameter for the second part is C. 2∞ The division of k2 and t2start is based on the discontinuities of the fitted straight line in the LOS plot.

[0114] The curve obtained by fitting the starch digestibility obtained in the previous section with first-order kinetics is shown in the figure below. Figure 6 The fitting results show that R 2 The LOS fitting results are good within the range of 0.8917 to 0.9348. Figure 7 The results showed that the in vitro digestion process of Pos in all groups exhibited a clear biphasic nature, meaning that the digestion rates (slope k) of the two starch components were completely different, with the digestion rate of the first component being significantly greater than that of the second. Furthermore, as the digestion time increased, the starch hydrolysis rate gradually reached an equilibrium state. Based on this, the intestinal segment digestion process of starch gel was simulated using a CPS model, and the fitting results are shown in [Figure number missing]. Figure 8 It can be seen that the "two-phase separation point" (t) of all systems 2start ) Around 15-20 minutes, t 2start This is the time when the amorphous starch (RDS), which is easily hydrolyzed by amylase, is almost completely consumed. After this time, the amylase targets the more dense crystalline starch (SDS), which has greater resistance to enzymatic digestion. This is roughly the same as the commonly accepted distinction time between rapidly digestible starch (RDS) and slowly digestible starch (SDS), which is 20 minutes.

[0115] Figure 9 When t is displayed as present or absent in WOPP 2start The change, the addition of WOPP, makes Pos digest t 2start Faster, i.e., t 2start The decrease in the value means that the rapid digestion phase of the first phase ends earlier after the addition of WOPP, and the second phase of slow digestion begins earlier. This phenomenon corresponds to the increase in RS and SDS content in previous studies.

[0116] Example 9

[0117] This embodiment provides a method for calculating a simulated glycemic index (eGI), including:

[0118] The area under the starch digestion curve (AUC) is calculated using the integral method. The formula for calculating eGI is as follows:

[0119] ;

[0120] AUC s It is the area under the starch digestion curve in the sample group; AUC w 1 is the area under the digestion curve of white bread, HI is the starch hydrolysis index, and eGI is the predicted glycemic index.

[0121] Generally, white bread has been used as a reference in in vitro studies of GI values ​​(GI value of white bread = 100). Low, medium, and high GI foods are defined as GI values ​​≤ 55, GI values ​​between 56 and 69, and GI values ​​≥ 70, respectively. A GI value below 70 is generally considered more beneficial to human health. Therefore, using white bread hydrolysis as a benchmark, the changes in the eGI value of the WOPP-Pos complex system were compared. The results are shown in Table 3.

[0122] Table 3. Parameters and glycemic index of the WOPP-POS digestive model .

[0123] *The experiment was repeated at least 3 times to obtain the mean ± standard deviation of each value. Different letters in the same column indicate significant differences (p < 0.05).

[0124] As shown in Table 3, k and C in the Control group ∞ The values ​​were 0.0761 min. -1 The eGI value was 73.56%, while it was significantly reduced after the addition of WOPP, and this reduction was concentration-dependent. The eGI value dropped from a low of 89.94 to a minimum of 81.08, indicating that WOPP can alleviate the rise in blood sugar to some extent.

[0125] Example 10 Glucose diffusion delay index

[0126] The digestate from the stomach was transferred to a dialysis bag (molecular weight cutoff of 3000 Da), the pH was adjusted to 7.0, and intestinal digestion fluid was added. The dialysis bag was then sealed, mixed thoroughly, and placed in 330 mL of phosphate buffer (20 mmol·L⁻¹). -1 In a dialysis bath at pH 7.0, the dialysis bag was stirred at 37°C to simulate intestinal peristalsis and digestion. The bag was inverted every 15 minutes to prevent uneven diffusion. 50 µL of dialysate was collected at 0, 10, 20, 60, 90, 120, and 180 minutes for glucose determination, and an equal volume of PBS was added. The formula for the glucose diffusion delay index (GDRI%) is as follows:

[0127] ;

[0128] In the formula: Glu s Glu cThe total glucose levels in the WOPP group and the control group are represented respectively.

[0129] Determination of glucose adsorption capacity: Prepare 5 mg / mL PBS buffer. -1 WOPP solutions contained 0, 5, 50, 100, 150, and 200 mmol·L⁻¹, respectively. -1 Glucose was collected and kept in a 37°C water bath for 3 h, then centrifuged at 4000 rpm for 20 min. The glucose content in the supernatant was determined using the DNS method, with a concentration of 5 mg / mL. -1 Guar gum was used as a positive control, and no sample was added as a blank control. The calculation formula is as follows:

[0130] ;

[0131] In the formula: A0 represents the glucose content (mmol) of the supernatant of the blank group, A1 represents the glucose content (mmol) of the supernatant of the sample group; m represents the total mass of the sample in the solution (g).

[0132] like Figure 10 As shown in (a), the glucose diffusion delay index (GDRI%) exhibits a concentration-dependent trend with WOPP. Throughout the entire in vitro simulated intestinal digestion process, high concentrations of WOPP demonstrated a strong inhibitory effect on glucose diffusion. In the early stages of digestion, the GDRI was higher, possibly because the starch granule structure was protected by the physical barrier of WOPP, delaying starch digestion. In previous studies on the rheological properties of WOPP, low concentrations showed a dilute solution, while high concentrations exhibited an entangled network structure, tending to form a weak gel. This explains why a certain GDRI was maintained even after starch was largely digested; it is likely because WOPP increases the viscosity of the digestive fluid, and high concentrations of WOPP possess an entangled network structure, thereby delaying the diffusion of starch products.

[0133] Furthermore, glucose adsorption capacity can, to some extent, reflect the body's ability to absorb and transport glucose; the stronger the adsorption capacity of a sample, the stronger its ability to control blood glucose fluctuations. For example... Figure 10 As shown in (b), the glucose adsorption capacity of WOPP at different concentrations was evaluated using four initial glucose concentrations. The adsorption capacity of WOPP was proportional to the glucose concentration, and the adsorption capacity increased with the increase of WOPP concentration, but the adsorption capacity was lower than that of the positive control guar gum. Therefore, WOPP has a limited glucose binding capacity, but its main mechanism for regulating starch digestion may not be through the adsorption of large amounts of glucose.

[0134] Example 11 Changes in digestive enzyme activity in a mixed system

[0135] Determination of amylase activity

[0136] 0.2 g of potato starch was dispersed in 20 mL of 20 mM PBS (pH 7.0), heated continuously at 100 °C for 20 min with stirring, then cooled to 37 °C and brought to a final volume to prepare a 10 mg / mL solution. -1 A starch solution. Amyloglucosidase (ASP) was dissolved in PBS to prepare an enzyme buffer solution (1 U / mL). -1 Amyloglucosidase was mixed thoroughly with PBS and WOPP of different concentrations and incubated at 37°C for 30 min. 500 µL of the incubated amyloglucosidase solution was mixed with an equal proportion of starch solution, and then 500 µL of gelatinized potato starch solution was added. The mixture was reacted in a 37°C water bath for 10 min. Afterward, 500 µL of DNS was added, and the mixture was immediately placed in a boiling water bath for 3 min to stop the reaction. The mixture was cooled to room temperature under running water and stored in the dark. The absorbance at 540 nm was measured using an automated microplate reader, with acarbose used as a positive control. The inhibition rate of the sample was calculated using the following formula.

[0137] ;

[0138] In the formula, A1 is the absorbance obtained by reacting amylase with substrate and WOPP; A2 is the absorbance measured after mixing WOPP of the corresponding concentration with substrate; A3 is the absorbance obtained by reacting amylase with substrate and PBS only; and A4 is the absorbance measured after mixing PBS with substrate.

[0139] Determination of amylase inhibitor type: The inhibitory kinetics of WOPP on amylase was evaluated using the Lineweaver-Burk double reciprocal equation, and the inhibitor type was analyzed by kinetic analysis. In short, with a fixed amylase concentration, different concentrations (2, 3, 4 mg / mL) were obtained according to the enzyme inhibition assay method described above. -1 WOPP and potato starch (4, 6, 8, 10 mg / mL) -1 The initial reaction rate (V) was calculated. The inhibition parameter (K) was calculated via nonlinear regression using the following equation, with the reciprocal of the substrate concentration (1 / [S]) as the x-axis and the reciprocal of the reaction rate (1 / V) as the y-axis. m and V max The formula is as follows:

[0140] ;

[0141] In the formula, ν represents the initial rate of the enzymatic reaction, [S] represents the concentration of the substrate (potato starch solution), and V max K represents the maximum reaction rate. m This represents the Michaelis constant. The results are shown in Table 4 and... Figure 11 As shown:

[0142] Table 4. Inhibitory activity of WOPP against amylase (V max and Michaelis-Menten constant (K m )) .

[0143] like Figure 11 As shown in (a), at 1–5 mg·mL -1 Within the specified range, WOPP exhibits inhibitory activity against ASP, with a half-inhibitory concentration of 5.28 mg·mL⁻¹. -1 Although its inhibitory effect is not as good as acarbose, its blood sugar lowering potential makes it possible to develop it into a blood sugar lowering product.

[0144] To further investigate the type of inhibitory effect of WOPP on ASP, the inhibitory kinetics of WOPP on amylase were analyzed using Lineweaver-Burk plots. Figure 11 (b) It is evident that the Lineweaver-Burk lines for WOPP and starch at different concentrations exhibit different slopes and intercepts, and both Vmax and Km decrease with increasing concentration. This demonstrates characteristics of a mixed-type inhibitor, where the inhibitor binds to the enzyme-substrate complex (ES) with a stronger affinity than to the free enzyme (E). This means that WOPP binds to the enzyme-substrate complex and prevents product formation, while simultaneously reducing the enzyme's catalytic activity. This type of inhibition typically occurs in multi-substrate enzymatic reactions in the presence of the inhibitor.

[0145] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A method for reducing starch digestibility using soluble dietary fiber from cactus, characterized in that, Add cactus soluble dietary fiber to a starch system, wherein the amount of cactus soluble dietary fiber added to the starch system is 0.5~2 mg·mL. -1 .

2. The method according to claim 1, characterized in that: The starch system includes potato starch.

3. The method according to claim 1, characterized in that: The soluble dietary fiber content of the cactus soluble dietary fiber is 0.5 ~ 5 mg·mL. -1 .

4. The method according to claim 1, characterized in that: The cactus soluble dietary fiber is prepared by a method comprising the following steps: (1) Wash, cut, dry, crush, and sieve the cactus leaves to obtain cactus powder; (2) Take cactus powder, add water, heat to extract, cool, centrifuge to get the supernatant, filter residue to extract repeatedly, centrifuge and combine the supernatants; (3) Add ethanol to the supernatant, mix well, let stand, filter and collect the precipitate, freeze dry and then reconstitute, dialyze, concentrate under reduced pressure, freeze dry, and obtain cactus soluble dietary fiber.

5. The method according to claim 4, characterized in that: In step (1), the sieving is done through an 800-mesh sieve; In step (2), the mass-to-volume ratio of the cactus micropowder to water is (10~15) g:1 L; the extraction temperature is 80~100℃ and the time is 0.5~1.5 h; in step (3), the volume ratio of the supernatant to ethanol is 1:(3~5); dialysis is performed using a 3000 Da dialysis bag; the dialysis time is 48~72 h.

6. A method for improving the physicochemical properties of potato starch, characterized in that: Add cactus soluble dietary fiber to potato starch.

7. The method according to claim 6, characterized in that: The physicochemical properties include one or more of the following: expansion, gelatinization temperature, and viscosity.

8. A low-digestibility potato starch compound composition, characterized in that, It includes potato starch and cactus soluble dietary fiber.

9. The low-digestibility potato starch compound composition according to claim 8, characterized in that: The mass ratio of potato starch to cactus soluble dietary fiber is 10:(1~5).

10. The application of cactus soluble dietary fiber in the preparation of low-GI foods.

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