Method for improving starch digestion inhibition effect of protein

Abstract

The invention discloses a method for improving the starch digestion inhibition effect of protein, and belongs to the technical field of food processing. Highland barley starch, highland barley prolamin, highland barley glutelin and highland barley separation are selected as raw materials, and the embedding structure of protein in a natural grain structure on the surface of starch particles is simulated by using a spray drying technology. The preparation method comprises the following steps: dissolving protein in 0.02% NaOH solution, then adding highland barley starch, stirring for 30 minutes, then carrying out spray drying treatment, controlling the addition amount of the protein to be 10% of the total mass of the starch, setting the inlet temperature of a spray dryer to be 170 DEG C, setting the outlet temperature to be 80 DEG C, and controlling the feeding speed of a peristaltic pump to be 35 mL / min, the appearance of the prepared starch sample is similar to the spatial structure in highland barley grains, and the digestibility of the highland barley grains is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to a method for improving the starch digestion inhibiting effect of proteins and belongs to the technical field of food processing. BACKGROUND

[0002] Chronic diseases such as diabetes and cardiovascular diseases have become one of the main threats to human health, and the treatment methods thereof are not only drug treatment but also reasonable dietary control which is an effective auxiliary treatment method. In recent years, low GI food has been widely concerned by nutritionists and medical scientists, and the World Health Organization indicates that low GI diet is an effective dietary pattern suitable for such population. As the main source of energy required by human physiological activities, starch can be divided into resistant starch, slow-digesting starch and fast-digesting starch according to the digestion speed. Among them, slow-digesting starch or resistant starch is a very important ingredient in low GI diet. It is one of the research hotspots in the field of food processing to modify starch by physical, chemical and biological methods or directly modify food raw materials to obtain high content of slow-digesting starch and resistant starch and apply them to the food industry.

[0003] Highland barley is a kind of grain crop, and has a history of more than 3500 years in the world. In recent years, highland barley has been paid more and more attention by the public due to its low glycemic index (less than 55). Studies have found that the lower digestibility of highland barley kernels is related to the structural distribution of endogenous components including starch and protein and other non-starch components. The digestion rate of starch wrapped in the cell wall of highland barley is significantly limited by the rigid cell wall and protein matrix. The endogenous protein in highland barley is wrapped on the surface of starch granules, and the exposed residues interact with the related groups of endosperm starch to form a physical barrier, weaken the accessibility of enzymes, inhibit the gelatinization and degradation of starch, and thus play a role in regulating starch digestion.

[0004] Proteins as the second largest component in food matrix have important influence on the structure and function of food. However, compared with the influence of endogenous proteins in natural grains, the influence of exogenous proteins on starch digestibility is relatively limited. This can be attributed to the spatial arrangement and interaction of endogenous proteins and starch in natural grains. Previously, we explored the digestion mechanism of slowly digestible starch in highland barley. The cage structure formed by the surface proteins of starch granules is the main way for proteins to regulate starch digestion. During the digestion process, this structure gradually disintegrates as the digestion time increases, and the internal starch is gradually released, thereby achieving a long-term functional effect and compensating for the inability of RS3 to provide energy. Existing methods generally use physical blending of proteins and starch, supplemented by conventional wet heat treatment (such as water bath, steaming or simple heating) to construct the composite system. However, during such treatment, the adsorption and coating behavior of proteins on the surface of starch granules lacks controllability and uniformity, making it difficult to form a stable, dense and continuous interfacial barrier layer. This non-specific and irregular protein distribution not only weakens the physical barrier effect of proteins on starch granules during the gelatinization stage, limiting their ability to inhibit starch swelling and disintegration, but also significantly reduces the structural stability of the composite system during heat treatment; more critically, due to the unclear mechanism of protein-starch interfacial interaction and insufficient binding strength, the shielding effect of proteins on the starch enzymatic hydrolysis pathway is unstable, making it difficult to effectively delay or inhibit the hydrolysis rate of starch during digestion, thereby overall restricting the functional performance and application potential of such composite systems in regulating starch digestion characteristics. SUMMARY

[0005] To solve the above problems, the present application aims to regulate starch digestibility by mimicking the structure of natural grains, and proposes a method for simulating the reconstruction of protein-starch cage complexes in grains using spray drying technology to achieve efficient and continuous industrial production. Spray drying (SD) technology is a fast and cost-effective drying technology that can quickly evaporate the solvent in the sample, thereby producing a powder-like treated sample. Without additional processing, the structure formed during the SD process is largely preserved. The present application selects highland barley starch, highland barley prolamin, highland barley glutelin, and highland barley protein isolate as raw materials, uses spray drying technology to simulate the embedding layer of proteins on the surface of highland barley starch granules in the structure of natural grains, significantly reduces the digestibility of highland barley starch, and achieves uniform and controllable spray drying of the protein coating layer on the surface of highland barley starch.

[0006] The present application provides a method for inhibiting starch digestion by proteins, specifically comprising the following steps: (1) Dissolve the protein in a NaOH solution, then add highland barley starch to obtain a material suspension, and then stir; (2) Dry the material suspension by spray drying to obtain a spray-dried powder; (3) adjusting the pH of the spray-dried powder to neutral, drying to obtain a starch sample with higher enzymatic resistance.

[0007] In an embodiment of the present application, the protein in step (1) is one or more of the following: highland barley alcohol-soluble protein, highland barley glutelin, highland barley protein isolate.

[0008] In an embodiment of the present application, the stirring parameters in step (1) are set as follows: stirrer speed 750 rpm, stirring time 30 min.

[0009] In an embodiment of the present application, the mass ratio of protein to highland barley starch in step (1) is 1:10.

[0010] In an embodiment of the present application, the concentration of the NaOH solution in step (1) is 0.02%.

[0011] In an embodiment of the present application, the amount of NaOH solution added in step (1) is 4 L per 100 g of highland barley starch on a dry basis.

[0012] In an embodiment of the present application, the spray-drying process in step (2) is performed with the following parameters: inlet temperature 170±5°C and outlet temperature 80±2°C; and the feed rate of the peristaltic pump is controlled at 34-37 mL / min.

[0013] In an embodiment of the present application, the pH of the spray-dried powder in step (3) is adjusted to 6.8-7.0, and the powder is washed with deionized water three times.

[0014] In an embodiment of the present application, the drying in step (3) is performed using a vacuum freeze dryer.

[0015] A second object of the present application is a starch sample with higher enzymatic resistance prepared by the method of the present application.

[0016] A third object of the present application is the use of the method of the present application in the preparation of a starch-based food, medicine or health food with slow digestion rate and low digestibility.

[0017] [Advantages] (1) The method of the present application is simple and easy to prepare. The starch sample prepared by the method has a reduced hydrolysis rate in in vitro simulated digestion, and the effects of whole protein, alcohol-soluble protein, glutelin and alcohol-soluble protein+glutelin in inhibiting in vitro simulated hydrolysis of starch are improved. Among them, glutelin has the lowest hydrolysis rate, and the spray-drying technology has the most significant effect on improving the digestibility of glutelin-inhibited starch.

[0018] (2) The present invention sets the inlet temperature of the spray drying tower at 170℃ and the outlet temperature at 80℃ to obtain the dried sample. The swelling potential of the starch sample decreases, and the effect on the swelling potential of the spray-dried sample with added gluten is the most significant; at the same time, the RVA peak viscosity of the starch sample decreases after the addition of protein; the spray drying treatment can greatly improve the effect of gluten in inhibiting starch swelling and gelatinization. It reduces the DSC enthalpy value and increases the TGA peak temperature of the starch sample with added protein; the thermal stability of the starch sample with different soluble proteins is improved to varying degrees.

[0019] (3) The spray-dried powder prepared by the present invention has an ideal appearance and uniform particle size.

[0020] (4) The method of the present invention is simple, easy to prepare and has a high utilization rate of raw materials, providing a basis for the industrial preparation of slow-digestion starch-based foods. Attached Figure Description

[0021] Figure 1 The in vitro simulated hydrolysis rate curves are for Comparative Examples 1-4 and Examples 1-4.

[0022] Figure 2 The diffusion curves of glucose concentration in dialysate during the 180-minute in vitro starch digestion process of Comparative Examples 1-4 and Examples 1-4 are shown.

[0023] Figure 3 Viscosity curves for Comparative Examples 1-4 and Examples 1-4.

[0024] Figure 4 The TG and DTG curves are for Comparative Examples 1-4 and Examples 1-4. Detailed Implementation

[0025] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0026] Test method: Basic component determination: Total starch and β-glucan content in the samples were determined using K-TASTA and K-BGLU kits, respectively. Moisture, protein, and fat content were determined according to AACC standard methods: 44-01.01, 46-13.01, and 30-20.01, respectively. The conversion factor from nitrogen content to protein content was 5.83.

[0027] In vitro simulated digestibility of starch: The in vitro simulated digestibility of the samples was determined according to the in vitro simulation method reported by Yang, with some improvements. Specifically, 600 mg of sample was placed in a 50 mL screw-cap centrifuge tube, and 10 mL of sodium acetate buffer (0.2 mol / L, pH 5.2) was added. The mixture was then gelled in a boiling water bath for 30 min (mixed thoroughly with a vortex mixer every 10 min). The gelled sample was then placed in a 37°C constant temperature water bath shaker at 200 rpm for 10 min. Next, 10 mL of a pre-prepared 5 mg / L pepsin solution was added to each gelled sample, and the reaction was allowed to proceed for 30 min. After the reaction solution was thoroughly mixed, 500 μL was immediately and accurately pipetted, and 5 mL of anhydrous ethanol was added to inactivate the enzyme (the glucose content in the resulting reaction solution represents the glucose content generated at 0 min of enzyme reaction). Then, 5 mL of a mixed enzyme solution containing trypsin and glucosidase was added to each tube. At 5, 10, 15, 20, 40, 60, 90, 120, 150, and 180 min, the test tubes were thoroughly mixed, and 500 μL of the reaction solution was accurately pipetted. 5 mL of anhydrous ethanol was added to inactivate the enzyme, and the glucose content (Gt) was determined using a GOPOD kit. The pepsin solution was prepared by adding 50 mg of pepsin to 10 mL of 0.05 mol / L HCl and mixing thoroughly, then storing at 4°C. The mixed enzyme solution was prepared by suspending 3 g of pancreatic enzyme powder in 20 mL of distilled water, centrifuging at 4000 rpm for 5 min, collecting 15 mL of the supernatant, mixing thoroughly with 1.1 mL of glucoamylase, and storing at 4°C.

[0028] Hydrolysis rate (%) = Gt × 0.9 / TS × 100% Where Gt is the amount of glucose released at time t (0~180min), and TS is the total starch content in the sample.

[0029] The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) are calculated according to the following formula: RDS(%) = (G20 - FG) × 0.9 / TS × 100% SDS(%)=(G120-G20)×0.9 / TS×100% RS(%)=[TS–(RDS+SDS)]×0.9 / TS×100% Wherein, G20 is the glucose content (mg) generated when the sample is hydrolyzed for 20 min, FG is the free glucose content (mg) in the sample, and G120 is the glucose content (mg) generated when the sample is hydrolyzed for 120 min.

[0030] The starch hydrolysis rate curve can be fitted with a first-order kinetic equation for analyzing the k value and C of the enzymatic hydrolysis reaction. ∞ value: C t =C ∞ (1-e) -kt ) Among them, C t (%) represents the digestibility of the sample at time t (min) during digestion, C ∞ To estimate the starch digestibility at the reaction endpoint, k(min) -1 () is the digestion rate constant.

[0031] Glucose diffusion rate: Glucose release from the sample in the digestive tract was simulated and determined according to the method described by Fabek, Messerschmidt, Brulport, and Goff, with some modifications. Specifically, after gastric digestion as described in the in vitro simulated digestibility of starch, the chyme was transferred to a dialysis bag (YiboBiological, USA) pre-filled with a pancreatic enzyme mixture. The dialysis bag was 34 mm wide and had a molecular weight cutoff of 2000 Da. Five glass bulbs were then placed in the dialysis bag, and the sealed dialysis bag was placed in a beaker containing 450 mL of 0.01 mol / L sodium phosphate buffer and sealed with plastic wrap. Dialysis was performed at 37 °C for 180 min, with shaking every 10 min to ensure thorough mixing. 200 μL of dialysate was collected at 0, 10, 20, 40, 60, 90, 120, 150, and 180 min, and 200 μL of sodium phosphate buffer was added back to the beaker after each collection. The glucose content in the dialysate was collected using the GOPOD kit. Each test was repeated three times.

[0032] Water solubility index and swelling power: Accurately weigh the sample (dry weight denoted as W1, mg), prepare a 10 mL sample suspension (2%, w / w), and heat at 95℃ for 30 min (mixing every 10 min). After heating, rapidly cool the sample in an ice bath, centrifuge at 4000×g for 15 min, dry the supernatant in a 105℃ oven to constant weight, and weigh it (W2, mg). Weigh the precipitate directly (W3, mg). The water solubility and swelling power are calculated as follows: Watersolubility(%)=(W2 / W1)×100

[0033] RVA determination: The viscosity profile of the sample during gelatinization was determined using a rapid viscosity analyzer (RVA). 3g of sample (14% water basis) was suspended in an aluminum bottle containing 25mL of distilled water (corrected for a 14% water basis). The suspension was heated to 50°C and stirred at 960 rpm for 10 s to ensure complete dispersion. At 50°C, the mixture was stirred at 160 rpm for 1 min. Then, it was heated to 95°C for 4 min 42 s. The mixture was stabilized at 95°C for 2.5 min, cooled to 50°C for 11 min, and finally held at 50°C for 2 min.

[0034] DSC determination: The thermal properties of the samples were detected using a differential scanning calorimeter (DSC), with each test repeated three times. The sample (4 mg) was sealed in an aluminum crucible with deionized water at a 1:2 ratio and allowed to equilibrate overnight at room temperature. The sample was then scanned from 25 °C to 95 °C at a rate of 10 °C / min, using an empty aluminum crucible as a reference. The initial temperature (T0) of the sample was analyzed using thermal data analysis software (STARe Default DB V16.00, METTLER, Greifensee, Switzerland). o Peak temperature (T) p ), End temperature (T) c ) and enthalpy change (ΔH).

[0035] TGA determination: The thermal stability of the sample was studied using a thermogravimetric analyzer (TGA). Approximately 2 mg of sample was weighed into a ceramic crucible and sealed. The determination conditions were: N2 flow rate of 50 mL / min, heating from 25 °C to 600 °C at a heating rate of 10 °C / min. The weight loss rate as a function of temperature (TG) and its derivative (DTG) were analyzed.

[0036] Raw materials used in the examples: All raw materials used in the embodiments of this invention are extracted from highland barley flour, which is powder made by grinding highland barley grains with a milling machine. The preparation of highland barley protein isolate, highland barley prolysin, highland barley gluten, and highland barley starch in this invention are based on the research of Yang et al. (Yang Y, Jiao A, Zhao S, et al. Effect of removal of endogenous non-starch components on the structural, physicochemical properties, and in vitro digestibility of highland barley starch[J]. Food Hydrocolloids, 2021, 117:106698.).

[0037] The extraction of barley protein isolate (HBPI) used in this embodiment of the invention is as follows: 250g of barley flour was thoroughly mixed in 1L of 0.2% NaOH solution and left at room temperature for 4 h. Centrifuged at 4000×g for 20 min, the supernatant was transferred to a beaker, and the precipitate was washed twice with NaOH solution. Centrifuged again under the same conditions, and the supernatant obtained from centrifugation was added to the supernatant obtained above. The pH of the supernatant was adjusted to 4.5 using 1M HCl solution, and after standing for 2 h, centrifuged again under the same conditions. The precipitate obtained from centrifugation was washed three times with deionized water. The precipitate was then dried using a vacuum freeze dryer for 36 h to obtain HBPI.

[0038] Extraction of barley prolysin (Pro) used in this embodiment of the invention: 5 kg of barley flour was added to 4500 mL of 10% NaCl, and the suspension was extracted in a fume hood for 2 h. The mixture was centrifuged at 4000 r / min for 5 min, and the supernatant was discarded. The precipitate was washed three times with 9000 mL of 10% NaCl, centrifuged at 4000 r / min for 5 min, and the supernatant was discarded. The mixture was then washed three times with distilled water. 4 L of 10% NaCl solution was added to the residue obtained above. Subsequent extraction and centrifugation steps were performed according to the method for extracting HBPI described above. The collected supernatant was placed in a 40°C water bath for 48 h to remove the ethanol solution. The precipitate accumulated at the bottom of the beaker was washed three times with deionized water. The mixture was then dried using a vacuum freeze dryer for 36 h to obtain Pro.

[0039] In this embodiment of the invention, the extraction of barley gluten protein (Glu) was performed as follows: 4 L of 0.2% NaOH solution was added to the precipitate obtained after the above extraction of Pro. The subsequent extraction, centrifugation, acid precipitation and drying steps were carried out in accordance with the above method for extracting HBPI to obtain Glu.

[0040] The extraction of barley starch (HBS) used in this embodiment of the invention is as follows: 320 mL of NaOH solution (0.05 M) was added to 40 g of barley flour, and the mixture was shaken in a water bath at 30°C (200 rpm) for 8 h, followed by centrifugation at 4000×g for 15 min. The supernatant was discarded, and the precipitate was washed twice with distilled water. The uppermost yellow layer was carefully scraped off, and the resulting precipitate was HBS. The precipitate was thoroughly washed with 75% ethanol solution and vacuum filtered. Finally, the precipitate was dried in an oven at 40°C for 24 h to obtain pure HBS.

[0041] Example 1 A method for improving the effect of protein in inhibiting starch digestion includes the following steps: (1) Dissolve 10 g of HBPI in 4 L of 0.02% NaOH solution, then add 100 g of HBS and stir at 750 rpm for 30 min at room temperature to obtain a suspension; (2) Subsequently, the suspension is fed into the drying chamber of the spray dryer by a peristaltic pump at a feed rate of 35 mL / min through a spray drying process. The spray dryer is operated at an inlet temperature of 170°C and an outlet temperature of 80°C to obtain spray-dried powder; (3) The collected spray-dried powder was suspended in 400 mL of 0.01 M HCl solution, and the pH was adjusted to 6.8~7.0 with 1 M HCl solution. The powder was centrifuged at 4000×g for 20 min, and the precipitate was washed three times with deionized water. (4) The precipitate obtained above is dried in a vacuum freeze dryer for 36 h to obtain the sample, named SD-HBPI+HBS, and stored at room temperature for subsequent analysis.

[0042] Example 2 A method for improving the effect of protein in inhibiting starch digestion includes the following steps: (1) Dissolve 10 g of Pro in 4 L of 0.02% NaOH solution, then add 100 g of HBS and stir at 750 rpm for 30 min at room temperature to obtain a suspension; (2) Subsequently, the suspension is fed into the drying chamber of the spray dryer by a peristaltic pump at a feed rate of 35 mL / min through a drying spray treatment. The spray dryer is operated at an inlet temperature of 170°C and an outlet temperature of 80°C to obtain spray-dried powder. (3) The collected spray-dried powder was suspended in 400 mL of 0.01 M HCl solution and the pH was adjusted to 6.8~7.0 with 1 M HCl solution. The mixture was centrifuged at 4000×g for 20 min and the precipitate was washed three times with deionized water.

[0043] (4) The precipitate obtained above is dried in a vacuum freeze dryer for 36 h to obtain the sample, named SD-Pro+HBS, and stored at room temperature for subsequent analysis.

[0044] Example 3 A method for improving the effect of protein in inhibiting starch digestion includes the following steps: (1) Dissolve 10 g of Glu in 4 L of 0.02% NaOH solution, then add 100 g of HBS and stir at 750 rpm for 30 min at room temperature to obtain a suspension; (2) Subsequently, the suspension is fed into the drying chamber of the spray dryer by a peristaltic pump at a feed rate of 35 mL / min through a drying spray treatment. The spray dryer is operated at an inlet temperature of 170°C and an outlet temperature of 80°C to obtain spray-dried powder. (3) The collected spray-dried powder was suspended in 400 mL of 0.01 M HCl solution, and the pH was adjusted to 6.8~7.0 with 1 M HCl solution. The powder was centrifuged at 4000×g for 20 min, and the precipitate was washed three times with deionized water. (4) The precipitate obtained above is dried in a vacuum freeze dryer for 36 h to obtain the sample, named SD-Glu+HBS, and stored at room temperature for subsequent analysis.

[0045] Example 4 A method for improving the effect of protein in inhibiting starch digestion includes the following steps: (1) Dissolve 5 g of Pro and 5 g of Glu in 4 L of 0.02% NaOH solution, then add 100 g of HBS and stir at 750 rpm for 30 min at room temperature to obtain a suspension; (2) Subsequently, the suspension is fed into the drying chamber of the spray dryer via a peristaltic pump at a feed rate of 35 mL / min through a spray drying process. The spray dryer is operated at an inlet temperature of 170°C and an outlet temperature of 80°C to obtain spray-dried powder; (3) The collected spray-dried powder was suspended in 400 mL of 0.01 M HCl solution and the pH was adjusted to 6.8~7.0 with 1 M HCl solution. The mixture was centrifuged at 4000×g for 20 min and the precipitate was washed three times with deionized water.

[0046] (4) The precipitate obtained above is dried in a vacuum freeze dryer for 36 h to obtain the sample, named SD-Pro+Glu+HBS, and stored at room temperature for subsequent analysis.

[0047] Comparative Example 1 Add 10 g of HBPI to 100 g of HBS, mix thoroughly, seal the sample in a self-sealing bag, name it HBPI+ HBS, and store it at room temperature for subsequent analysis.

[0048] Comparative Example 2 Add 10 g of Pro to 100 g of HBS, mix thoroughly, encapsulate the sample in the mixture, name it Pro+HBS, and store it at room temperature for subsequent analysis.

[0049] Comparative Example 3 Add 10 g of Glu to 100 g of HBS, mix thoroughly, encapsulate the sample in the mixture, name it Glu+HBS, and store it at room temperature for subsequent analysis.

[0050] Comparative Example 4 Add 5 g of Pro and 5 g of Glu to 100 g of HBS, mix thoroughly, encapsulate the sample in the mixture, name it Pro+Glu+HBS, and store it at room temperature for subsequent analysis.

[0051] The obtained starch sample underwent basic component analysis, and the test results are as follows: Table 1 lists the basic component contents of samples after adding different soluble barley proteins and after SD treatment. The moisture content of starch samples with added different soluble proteins ranged from 9.21% to 9.50%. After SD treatment, the moisture content of the samples decreased significantly, with SD-Glu+HBS having the lowest moisture content at only 1.97%, and SD-HBPI+HBS having the highest moisture content at 6.80%. Due to the different purity of the extracted proteins, the protein content in the samples varied. HBPI+HBS had the lowest protein content (6.28%), Pro+HBS had the highest (8.48%), and Glu+HBS had the lowest (7.10%). There were no significant differences in β-glucan and lipid contents among the different samples.

[0052] Table 1. Results of basic component determination of samples (g / 100 g, wet basis)

[0053] Note: Results are expressed as the mean ± standard deviation of the three experiments. Different superscript letters in the same column indicate significant differences within the same column. (Ducan's test, P<0.05).

[0054] The obtained starch samples were subjected to in vitro simulated starch digestibility analysis, and the test results are as follows: The in vitro simulated hydrolysis rate curves of all samples are as follows: Figure 1As shown in the figure, the hydrolysis rate curves of HBPI+HBS, Pro+HBS, Glu+HBS, and Pro+Glu+HBS samples exhibit certain differences. HBPI+HBS generally has the highest hydrolysis rate. The hydrolysis rate curve of Glu+HBS is lower than that of Pro+HBS in the first 60 min, while the hydrolysis rate of Pro+HBS is higher than that of Glu+HBS in the 60-180 min period. The hydrolysis rate curve of Pro+Glu+HBS is generally higher than that of Pro+HBS and Glu+HBS, but lower than that of HBPI+HBS. This indicates that adding Pro and Glu to HBS has a greater effect on amylase resistance than HBPI, and Pro's inhibitory effect on starch is weaker than that of Glu in the first 60 min. Furthermore, the hydrolysis rate curves of samples with different soluble proteins changed significantly after SD treatment. The results show that the hydrolysis rate curve of SD-HBPI+HBS is significantly lower than that of HBPI+HBS. The hydrolysis rate curves of HBS with added Pro before and after SD treatment showed little difference within 40 min. However, SD treatment significantly reduced the hydrolysis rate of Pro+HBS within 40–180 min. The hydrolysis rate curve of SD-Glu+HBS was significantly lower than that of Glu+HBS, exhibiting the lowest hydrolysis rate among all samples. Furthermore, the hydrolysis rate curve of SD-Pro+Glu+HBS was significantly lower than that of Pro+Glu+HBS. This indicates that SD treatment improved the inhibitory effect of HBPI, Pro, Glu, and Pro+Glu on starch hydrolysis in vitro, with Glu achieving the lowest hydrolysis rate, demonstrating that SD technology had the most significant effect in enhancing the inhibitory effect of Glu on starch digestibility.

[0055] Table 2. Digestive characteristics parameters of all samples obtained from in vitro digestion kinetics.

[0056] Note: Results are expressed as the mean ± standard deviation of the three experiments. Different superscript letters in the same column indicate significant differences within the same column. (Ducan's test, P<0.05).

[0057] Table 2 lists the characteristic values ​​of in vitro simulated digestion. Comparing the RDS content of HBPI+HBS, Pro+HBS, Glu+HBS, and Pro+Glu+HBS, the effects of adding Pro, Glu, and Pro+Glu on starch hydrolysis rate were not significantly different; however, Pro+HBS had the highest RDS content. This indicates that when different soluble proteins are directly added, Pro has the most significant effect on RDS in HBS. The SD treatment had different effects on the starch RDS content of different soluble proteins. SD treatment significantly reduced the RDS content of Glu+HBS samples, while the effect on Pro+HBS and Pro+Glu+HBS was not significant. This suggests that SD treatment can be used to construct an effective means of reducing the digestibility of HBS with Glu. Furthermore, the SD treatment technique also depends on the type of protein. Comparing the SDS content of all samples, it was found that the samples with added Pro obtained the highest SDS content before and after SD treatment, while the addition of Glu and HBPI both led to lower SDS contents. Comparing the RS content of HBPI+HBS, Pro+HBS, Glu+HBS, and Pro+Glu+HBS samples, Glu+HBS had the highest SDS content, while HBPI+HBS had the lowest RS content. After SD treatment, the RS content of samples with different soluble proteins increased. Among them, the addition of Glu resulted in the largest increase in starch RS after SD treatment, increasing by 5.31%. Pro+HBS showed the smallest increase after SD treatment, only 1.26%. This indicates that SD treatment can improve the inhibitory effect of proteins on starch digestion, especially Glu. Comparing the C content of all samples... ∞ The values ​​indicate that SD treatment significantly reduces the final digestibility of starch, and different proteins have different effects on starch digestibility, with HBPI showing the highest C value. ∞ RDS, SDS, SDS+RS, and C ∞ Correlation analysis with protein content in the samples showed that RDS content was significantly correlated with protein content, with correlation coefficients of -0.783 (0.05 level). However, SDS, RS, and C... ∞ The content of starch and protein content showed only a weak correlation, with correlation coefficients of 0.523, 0.601, and -0.610, respectively. This indicates that while protein content affects starch digestibility, the type of protein may have a greater impact.

[0058] The starch samples were analyzed for starch-glucose diffusion rate, and the results are as follows: The in vitro simulated glucose diffusion rate curves for all samples are as follows: Figure 2As shown in the figure, comparing the glucose production and hydrolysis rate curves of SD-HBPI+HBS and HBPI+HBS reveals that although the glucose production of SD-HBPI+HBS is higher than that of HBPI+HBS, the hydrolysis rate of SD-HBPI+HBS is significantly higher than that of HBPI+HBS. This indicates that adding HBPI to HBS helps accelerate glucose diffusion. This suggests that SD treatment may not be suitable for constructing slow-digesting starch from barley HBPI and HBS. Comparing the glucose production and diffusion curves of SD-Pro+HBS and Pro+HBS shows that although the hydrolysis rate curve of SD-Pro+HBS is much higher than that of Pro+HBS, the overall glucose diffusion rates of SD-Pro+HBS and Pro+HBS are not significantly different. This indicates that SD technology helps slow down the glucose diffusion rate of Pro and HBS during in vitro simulated digestion. Samples treated with Glu and SD show a glucose diffusion rate curve closer to that of Glu+S, but the glucose production curves of SD-Glu+HBS and Glu+HBS are very similar. Comparing the glucose production and diffusion curves of samples with added Pro and Glu before and after SD treatment, it can be seen that SD treatment can effectively slow down the glucose diffusion rate of Glu within 120 min. The synergistic addition of Pro and Glu showed a glucose diffusion rate between the two.

[0059] The obtained starch samples were subjected to swelling potential analysis, and the test results are as follows: The addition of different soluble proteins and SD treatment had different effects on the swelling potential of HBS. The swelling potential within the range of 55-95℃ is shown in Table 3. With increasing temperature, the swelling potential of all samples increased, showing a sharp increase at 95℃. Comparing the swelling potentials of HBPI+HBS, Pro+HBS, Glu+HBS, and Pro+Glu+HBS within the range of 55-85℃, it can be seen that Pro+HBS had the lowest overall swelling potential, while Glu+HBS had the highest overall. However, Pro+Glu+HBS had the lowest swelling potential at 95℃, while Glu+HBS had the highest. This indicates that the effects of adding different types of proteins on inhibiting starch swelling are different. Pro showed a more significant effect, and the synergistic effect of Pro and Glu was more significant than that of Pro, while Glu showed the weakest effect. The removal of Pro, Pro, and Glu led to the most significant change in the swelling potential of HBS in barley flour. This suggests that the interaction between Pro and Glu and starch in natural barley grains may play a significant role, and adding Glu alone to HBS is insufficient to inhibit starch swelling. After SD treatment, the swelling potential of samples with different types of proteins added was higher than that of untreated samples within the range of 55-85℃, but the swelling potential at 95℃ was lower than that of untreated samples. This indicates that SD treatment helps promote the swelling of starch samples below 85℃, but inhibits the swelling potential at 95℃. At 95℃, the swelling potential of SD-Pro+HBS was the lowest, but compared with the untreated Pro+HBS sample, it only decreased by 1.88% after SD treatment. The swelling potential of SD-Glu+HBS sample decreased significantly by 3.2% at 95℃. The decreases in swelling potential of HBPI+HBS and Pro+Glu+HBS after SD treatment were not significant, only 0.69% and 0.77%, respectively. It can be concluded that SD treatment has the most significant effect on the swelling potential of Glu+HBS, and can greatly improve the effect of Glu in inhibiting starch swelling and gelatinization.

[0060] Table 3. Expansion potential of all samples at 55℃~95℃

[0061] Note: Results are expressed as the mean ± standard deviation of the three experiments. Different superscript letters in the same column indicate significant differences within the same column. (Ducan's test, P<0.05).

[0062] The obtained starch samples were subjected to RVA analysis, and the test results are as follows: The RVA curves for all samples are as follows: Figure 3As shown in the figure, the viscosity curves of HBS samples with added HBPI, Glu, and Pro+Glu after SD treatment are all higher than those without SD treatment. However, the RVA curve of the HBS sample with added Pro gradually decreases with increasing temperature, becoming lower than that without SD treatment. This indicates that SD treatment has different effects on the gelatinization properties of HBS samples with different added proteins.

[0063] Table 4 lists the characteristic values ​​during the gelatinization process. Comparing the peak viscosities of HBPI+HBS, Pro+HBS, Glu+HBS, and Pro+Glu+HBS, it can be seen that the addition of different types of protein has different effects on the peak viscosity of the HBS samples. Compared to the peak viscosity of the original HBS (3610 cP) reported by Yang et al., the peak viscosity decreased after adding protein. This may be attributed to the inhibition of starch gelatinization by the addition of protein, but it is also related to the decrease in starch concentration (Yang Y, Jiao A, Zhao S, et al. Effect of removal of endogenous non-starch components on the structural, physicochemical properties, and in vitro digestibility of highland barley starch[J]. Food Hydrocolloids, 2021, 117: 106698.). Among them, Pro caused the greatest decrease in the peak viscosity of HBS, with a peak viscosity of only 2497.50 cP, while the viscosity decrease caused by Pro and Glu was not significantly different. After SD treatment, the effect of different protein additions on peak viscosity changed significantly. Specifically, the peak viscosity of SD-Pro+HBS was significantly lower than that of untreated HBS, while the peak viscosity caused by other protein types was significantly higher than that of untreated HBS. However, research by Santos et al. showed that the viscosity of cassava starch and Peruvian carrot starch after SD treatment was significantly lower than that of untreated HBS. However, the peak viscosity of starches with added protein showed the opposite change, indicating that protein is the main factor causing this phenomenon. However, the effect of protein on the gelatinization properties of HBS after SD treatment could not be determined, because SD treatment leads to a decrease in peak viscosity, while protein addition leads to an increase in peak viscosity, except for Pro. After SD treatment, peak-valley viscosity, disintegration value, retrogradation value, and final viscosity all showed similar trends.

[0064] Table 4. RVA characteristics of all samples

[0065] Note: Results are expressed as the mean ± standard deviation of the three experiments. Different superscript letters in the same column indicate significant differences within the same column. (Ducan's test, P<0.05).

[0066] The obtained starch sample was analyzed by DSC, and the test results are as follows: The DSC characteristic values ​​of all samples are shown in Table 5. As can be seen from the table, the effects of adding different types of proteins on the To, Tp, Tc, ΔH, and Tc-To of HBS varied. There was no significant difference in the To value of different types of proteins, but the Pro+HBS sample had the highest To value. The addition of HBPI resulted in the most significant Tp value for starch compared to other proteins, reaching 59.90℃. There was no significant difference in the Tp values ​​of starch between Pro+HBS and Glu+HBS. The Tc value of Pro+HBS was significantly the highest, while there was no significant difference between HBPI+HBS and Glu+HBS. The ΔH value results showed that Pro+Glu+HBS had the highest value at 6.38 J / g, followed by HBPI+HBS. This indicates that the addition of HBPI and Pro+Glu is more helpful in improving the thermal stability of HBS. The trend of Tc-To values ​​was consistent with that of ΔH. After SD treatment, the To, Tp, Tc, and ΔH values ​​of all samples decreased. The Tc-To values ​​decreased with the addition of HBPI+HBS, Pro+HBS, and Pro+Glu+HBS, while they increased with Glu+HBS. Changes in ΔH value generally represent changes in sample thermal stability; however, ΔH value is dependent on starch concentration, while changes in Tc-To are often a better indicator of sample thermal stability. Therefore, the thermal stability of Glu+HBS may have increased after SD treatment.

[0067] Table 5. DSC characteristics of all samples

[0068] Note: Results are expressed as the mean ± standard deviation of the three experiments. Different superscript letters in the same column indicate significant differences within the same column. (Ducan's test, P<0.05).

[0069] The obtained starch sample was analyzed by TGA, and the test results are as follows: The TG (weight loss curve) and DTG (first derivative of TG) curves of the sample are as follows: Figure 4As shown in the figure, the HBS samples with added HBPI exhibited two weight loss steps before and after SD treatment: water evaporation (50~150℃) and thermal degradation of protein or starch (150~450℃). The HBS samples with added Pro showed a third weight loss step (400~600℃) before and after SD treatment. The HBS samples with added Glu also showed a third thermal weight loss step (400~600℃) before SD treatment. However, the HBS samples with added Pro+Glu showed a third thermal weight loss step (400~600℃) after SD treatment. The occurrence of the third weight loss in the Pro-added HBS samples may be related to the properties of Pro itself, leading to a decrease in the thermal stability of the sample at 400~600℃. The third weight loss step disappeared in the Glu+HBS samples after SD treatment, indicating that SD treatment increased the thermal stability of Glu and HBS at 400~600℃. Comparing the DTG curves of all samples before and after SD treatment, it can be seen that after SD treatment, except for the second thermogravimetric peak of HBS with added Pro+Glu remaining basically unchanged, the thermogravimetric peaks of HBS with added HBPI, Pro, and Glu all shifted to the right. This indicates that SD treatment helps improve the thermal stability of HBS with added HBPI, Pro, and Glu.

[0070] The final residue levels of all samples at 600℃ were: SD-HBPI+HBS = 7.73%, SD-Pro+HBS = 0.95%, SD-Glu+HBS = 11.87%, SD-Pro+Glu+HBS = 17.66%, HBPI+HBS = 17.03%, Pro+HBS = 1.78%, Glu+HBS = 3.97%, and Pro+Glu+HBS = 21.35%. Comparing the maximum residue levels of HBPI+HBS, Pro+HBS, Glu+HBS, and Pro+Glu+HBS, it was found that Pro had the lowest final residue level, while Pro+Glu had the highest. After SD treatment, the influence of different protein types on the final residue level of HBS showed the same trend as before, but significantly reduced the final residue level of the samples. The DTG curves show that the peak temperatures of all samples are as follows: SD-HBPI+HBS = 320.000℃, SD-Pro+HBS = 312.500℃, SD-Glu+HBS = 315.333℃, SD-Pro+Glu+HBS = 312.500℃, HBPI+HBS = 317.000℃, Pro+HBS = 303.833℃, Glu+HBS = 308.000℃, and Pro+Glu+HBS = 312.167℃. Comparing the peak temperatures of HBPI+HBS, Pro+HBS, Glu+HBS, and Pro+Glu+HBS, HBPI+HBS has the highest peak temperature, followed by Pro+Glu+HBS, and Pro+HBS has the lowest. This is consistent with the trend of Tc-To in the DSC above. This indicates that the thermal stability of HBS with added HBPI and Pro+Glu is higher than that with added Pro and Glu. After SD treatment, the peak temperatures of all samples increased, with the HBS containing HBPI showing the highest peak temperature, followed by the HBS containing Glu. This indicates that SD treatment helps improve the thermal stability of all samples, with SD-HBPI+HBS exhibiting the highest thermal stability. The maximum loss rates for different samples are as follows: SD-HBPI+HBS = 0.310%, SD-Pro+HBS = 0.312%, SD-Glu+HBS = 0.259%, SD-Pro+Glu+HBS = 0.348%, HBPI+HBS = 0.323%, Pro+HBS = 0.260%, Glu+HBS = 0.322%, Pro+Glu+HBS = 0.287%. The maximum loss rates of HBS with different protein additions varied, arranged from highest to lowest as follows: HBPI+HBS > Glu+HBS > Pro+Glu+HBS > Pro+HBS.After SD treatment, the maximum loss rates of SD-HBPI+HBS and HBPI+HBS were very similar, while the maximum loss rate of SD-Pro+HBS was significantly higher than that of Pro+HBS. The maximum loss rate of SD-Glu+HBS was significantly lower than that of Glu+HBS, and the maximum loss rate of SD-Pro+Glu+HBS was significantly higher than that of Pro+Glu+HBS. This indicates that SD treatment has different effects on the maximum loss rate of HBS with different types of added proteins.

[0071] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for improving the effect of protein in inhibiting starch digestion, characterized in that, Using highland barley starch, highland barley prolysin, highland barley gluten, and highland barley protein isolate as raw materials, and employing spray drying technology, the process simulates the protein encapsulation layer on the surface of highland barley starch granules in the natural grain structure. The specific steps include: (1) Dissolve the protein in NaOH solution, then add barley starch to obtain a material suspension, and then stir; (2) The material suspension is subjected to a drying spray treatment to obtain spray-dried powder; (3) Adjust the pH of the spray-dried powder to neutral and dry it to obtain a starch sample with higher resistance to enzymatic hydrolysis.

2. The method for improving the effect of protein in inhibiting starch digestion according to claim 1, characterized in that, The protein mentioned in step (1) is one or more of barley prolysin, barley glutelin, and barley isolate.

3. The method for improving the effect of protein in inhibiting starch digestion according to claim 1, characterized in that, In step (1), the mass ratio of protein to barley starch is 1:

10.

4. The method for improving the effect of protein in inhibiting starch digestion according to claim 1, characterized in that, The concentration of the NaOH solution mentioned in step (1) is 0.02%.

5. The method for improving the effect of protein in inhibiting starch digestion according to claim 1, characterized in that, Step (1) The amount of NaOH solution added is 4L / 100g based on the dry basis of barley starch.

6. The method for improving the effect of protein in inhibiting starch digestion according to claim 1, characterized in that, The spray drying process described in step (2) has the following specific parameters: inlet temperature of 170±5℃ and outlet temperature of 80±2℃; the feed rate of the peristaltic pump is controlled at 34~37mL / min.

7. The method for improving the effect of protein in inhibiting starch digestion according to claim 1, characterized in that, Step (3) Adjust the pH of the spray-dried powder to 6.8~7.0 and wash it with deionized water.

8. The method for improving the effect of protein in inhibiting starch digestion according to claim 1, characterized in that, The drying process in step (3) is performed using a vacuum freeze dryer.

9. A starch sample with higher resistance to enzymatic hydrolysis prepared by any of the methods described in claims 1-8.

10. The use of the method according to any one of claims 1-8 in the preparation of starch-based foods, pharmaceuticals or health foods with slow digestion rate and low digestibility.

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