Method for rationally regulating and controlling digestibility of corn flour based on hot processing parameters

Abstract

The invention discloses a method for rationally regulating and controlling the digestive performance of corn flour based on hot processing parameters, and belongs to the technical field of food processing. In the preparation process of the corn flour, protein in corn kernels is reserved as much as possible, cellulose influencing the taste and germ parts with high lipid content are removed, and on the basis of a starch digestibility prediction model, different hot processing modes such as steaming, boiling and baking are utilized, so that the corn flour is obtained. The temperature, moisture environment, time and other parameters during treatment of the corn flour in the staple food are reasonably regulated and controlled, the microstructure of starch in the staple food and the binding state of the starch and protein are changed, the digestibility of the starch is further changed, and the corn flour can meet consumers with different health requirements. The method overcomes the defect that starch digestibility is regulated by a chemical method and an enzyme modification method, and the whole preparation process is simple in process, green, efficient and low in cost. In addition, according to the method, different hot processing modes and processing parameters of the corn flour are controlled, so that application in different demand scenes is met. The processing method disclosed by the invention is green and safe, has a good application prospect in the aspects of food production and processing, and has the potential of continuous production.

Description

Technical Field

[0001] The present invention relates to a method for rationally regulating the digestibility of corn flour based on thermal processing parameters, and particularly to a method for changing the starch digestibility by changing the microstructure of whole corn flour through thermal processing, belonging to the field of food processing. Background Art

[0002] According to the release and absorption rate of glucose in the gastrointestinal tract, starch can be divided into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). RDS can be digested and absorbed by the human body within 0 - 20 minutes, and can quickly provide energy for the human body, which is suitable for use in situations where rapid energy supplementation is required. However, it can cause an increase in blood glucose in the human body, leading to chronic diseases such as obesity, diabetes and its complications, and cardiovascular diseases. SDS and RS have benefits such as preventing colon cancer, reducing blood glucose, reducing the formation of gallstones, reducing cholesterol, inhibiting fat accumulation, and increasing mineral absorption. However, they cannot quickly provide energy, which is not applicable to situations where rapid energy supplementation is required, and may affect the taste and texture of food, restricting their application in certain foods.

[0003] Corn is one of the three major food crops in the world. It is rich in starch, protein, lipids, etc., among which starch accounts for about 68% - 75%. Therefore, corn starch is the main raw material in the production and processing of food. However, compared with corn, corn starch has more nutritional losses.

[0004] Corn flour is a kind of flour mainly ground from corn. Its components are almost the same as those of corn kernels. After extraction, traditional thermal processing will change the digestibility of corn flour. With the change of the starch digestibility in corn flour, its nutritional value also changes accordingly.

[0005] Traditional thermal processing methods for making staple foods from corn flour mainly include steaming, baking, extrusion, etc. In these thermal processing methods, different staple foods have different temperatures, moisture environments, times, yeast addition amounts, etc. during thermal processing, which will have different effects on the microstructure and physicochemical properties of corn flour, such as the fine structure of starch and the degree of wrapping and binding of non-starch components, thus affecting its digestibility.

[0006] Therefore, in order to meet the different nutritional needs of different people, such as quickly providing energy, controlling blood glucose, and preventing diet-related diseases, it is urgently necessary to establish a starch digestibility prediction model, and based on this, select different thermal processing conditions to provide staple foods with different digestibilities, which has broad market potential and high economic benefits. Summary of the Invention

[0007] In view of the deficiencies of the prior art, the present invention proposes a method for rationally regulating the digestibility of corn flour in staple foods based on thermal processing parameters. Based on the above starch digestibility prediction model, by changing the temperature, moisture environment, time, and yeast addition amount during processing, it is possible to change the starch microstructure and the degree of wrapping and binding of non-starch components without increasing additional costs and complex processes, effectively regulating the digestibility of starch in corn flour. Specifically, the present invention can, to a certain extent, control the RDS, SDS, and RS contents of corn flour in staple foods, change the starch digestion rate, and provide more suitable healthy corn staple foods for people with different needs. In addition, this method also has the advantages of simple operation and easy large-scale production, and has broad application prospects and market potential.

[0008] To solve the above technical problems, the first object of the present invention is to provide a method for rationally regulating the digestibility of corn flour in staple foods based on thermal processing parameters:

[0009] Apply degermed corn flour to the staple food system, and the specific processing method is as follows:

[0010] Mix gluten powder with corn flour according to 30% of the dry basis mass of degermed corn flour, add water accounting for 47.52% - 55.44% of the total mass of the mixed powder and 0 - 1.5% of yeast, and knead the dough. After the dough is formed, ferment it for 20 - 60 minutes under the conditions of a temperature of 37°C and a relative humidity of 80%, and then carry out heat treatment processing to obtain a staple food with a rapid digestible starch RDS content of Y;

[0011] The staple food is steamed bread, noodles or bread;

[0012] The conditions of heat treatment processing are predicted through the following model:

[0013] Y = 2.0991*t - 0.0518*t 2 - 0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0014] In the formula: Y represents the content of rapid digestible starch RDS under different heat treatment methods; t is the heat treatment time; T is the temperature during heat treatment; H is the humidity during heat treatment; L represents whether it is immersed in water, 1 if immersed, otherwise 0; A represents the yeast addition amount.

[0015] In one embodiment, the heat treatment of steamed bread is: steaming treatment;

[0016] The heat treatment of noodles is: knead the dough into a sheet, and after pressing it into noodles, cook it;

[0017] The heat treatment of bread is: exhaust air, shape it, and then bake it.

[0018] In one embodiment, the method for preparing degermed corn flour is as follows:

[0019] Place the washed corn kernels in warm water at 20 - 30°C and soak for 12 - 24 h. Break the soaked corn kernels into 10 - 12 pieces, separate the germ to form a coarsely ground suspension, continuously grind at high speed for 10 - 20 min, conduct fine screening through a 40 - 100 mesh centrifugal sieve, remove moisture by centrifugation at 1200 rpm for 5 - 10 min, and dry into powder to obtain degermed corn flour.

[0020] In one embodiment, the method for preparing degermed corn flour is as follows: Place the corn kernels in a soaking tank, inject warm water to soak them, allowing the corn kernels to fully absorb water and swell. Transport the soaked corn kernels to a crusher for preliminary crushing, use a germ separation hydrocyclone to separate the germ to form a coarsely ground suspension, send the corn suspension after removing the germ back to a jet mill for continuous high - speed grinding. After grinding, conduct fine screening through a centrifugal sieve, remove moisture from the corn suspension obtained through fine screening using a centrifugal dewatering machine, and finally dry it into powder through a jet dryer to obtain degermed corn flour;

[0021] The soaking treatment of the corn kernels is carried out by soaking in water at 20 - 30°C for 12 - 24 h;

[0022] The degree of the first - stage crushing is controlled to break the wet corn kernels into 10 - 12 pieces, and the second - stage grinding time is 10 - 20 min;

[0023] The mesh number of the centrifugal sieve is 40 - 100 mesh;

[0024] The conditions of the centrifugal dewatering machine are 1200 rpm for 5 - 10 min.

[0025] In one embodiment of the present invention, the method for making steamed buns is as follows: Mix wheat gluten powder with corn flour at 30% of the dry - basis mass of the corn flour, add water accounting for 55.44% of the total mass of the mixed powder and 1% yeast, and knead the mixed powder in a dough mixer. After the dough is formed, ferment it at a temperature of 37°C and a relative humidity of 80% for 40 - 60 min, and then carry out steaming treatment.

[0026] In one embodiment of the present invention, the method for making noodles is as follows: Mix wheat gluten powder with corn flour at 30% of the dry - basis mass of the corn flour, add water accounting for 47.52% of the total mass of the mixed powder, and knead the mixed powder into noodle flakes in a dough mixer. Ferment it at a temperature of 37°C and a relative humidity of 80% for 20 min, roll the dough into a dough sheet and press it 10 times, then press it into noodles and carry out boiling treatment.

[0027] In one embodiment of the present invention, the method for making bread is as follows: Mix wheat gluten with corn flour at 30% of the dry basis mass of corn flour, add water at 55.44% of the total mass of the mixed flour and 1.5% yeast, and place the mixed flour in a dough mixer to knead the dough. After the dough is formed, ferment it for 40 minutes under the conditions of a temperature of 37 °C and a relative humidity of 80%, then exhaust and shape it, and subsequently perform baking treatment.

[0028] Beneficial effects:

[0029] During the extraction process of corn flour, proteins in corn kernels are retained as much as possible, the germ with a relatively high content of cellulose and lipids that affect the taste is removed, and based on the starch digestibility prediction model, by different thermal processing methods such as steaming, boiling, and baking, parameters such as temperature, moisture environment, and time during staple food production are adjusted to control the starch digestibility in the product, providing staple food products with different GI values to meet the health needs of different consumers.

[0030] The present invention overcomes the defects of chemical methods and enzyme modification methods for regulating starch digestibility. The entire preparation process is simple, green and efficient, and low-cost.

[0031] In addition, the method of the present invention meets the application requirements in different scenarios by controlling different thermal processing methods of corn flour. The processing method is green and safe, has good application prospects in food production and processing, and has the potential for continuous production. Description of the drawings

[0032] Figure 1 Laser confocal images of staple foods after different thermal processing treatments

[0033] Figure 2 Scanning electron microscope images of staple foods after different thermal processing treatments Detailed implementation manners

[0034] The following will describe the implementation schemes of the present invention in detail in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0035] For those not specified in the examples, perform according to the conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0036] Determination and calculation method for in vitro digestion performance of starch: Accurately weigh 200 mg (dry basis) of the sample into a 50 ml centrifuge tube, add 4 ml of water and mix evenly. Samples without heat treatment need to be pre-gelatinized for 30 min. After the sample and treatment are completed, place them in a water bath shaker at 37 °C and 160 r / min for 10 min; add 4 mL of pepsin / hydrochloric acid solution (5 mg / mL), oscillate and react for 30 min, then add 6 glass beads (diameter 3 - 4 mm) and 2 mL of sodium acetate buffer solution (0.5 mol / L, pH 5.2), stir evenly and keep warm at 37 °C for 30 min; then add 2 mL of the mixed enzyme solution (including pancreatin and amyloglucosidase) for in vitro digestion reaction. At 0, 20, and 120 min during the reaction, take 0.05 mL of the reaction solution respectively, add it to 0.95 mL of ethanol solution (80%, v / v), and centrifuge at 10000 r / min for 5 min. Use the GOPOD kit to measure the glucose content in the supernatant, use an enzyme-labeled instrument to measure the absorbance of the solution to be measured at 520 nm, and calculate the RDS, SDS, and RS contents in the sample. The calculation formulas are as follows:

[0037] G = [(A - A0) × 5.46 × 180 × 20 × 12] / [(A st - A b ) × m]

[0038] RDS (%) = (G 20 - G0) × 0.9 × 100 / TS

[0039] SDS (%) = (G 120 - G 20 ) × 0.9 × 100 / TS

[0040] RS (%) = 1 - RDS - RS

[0041] In the formula: A refers to the absorbance of the solution at 520 nm, A0 refers to the absorbance of the blank solution at 520 nm, 5.46 × 180 refers to the concentration of the standard solution (5.46 mmol / L in this experiment), 12 refers to the total volume of the test solution (mL), 20 refers to the dilution factor, A st refers to the absorbance of the standard solution at 520 nm, A b refers to the absorbance value of water, m refers to the sample mass (mg, calculated on a dry basis); G0 refers to the free glucose content (%), G 20 refers to the glucose content (%) produced during in vitro digestion for 20 min, G 120 refers to the glucose content (%) produced during in vitro digestion for 120 min, and TS refers to the total starch content of the sample (g / 100 g, calculated on a dry basis).

[0042] Confocal laser measurement: Using a confocal laser scanning microscope (CLSM) with a 40× inverted objective lens, observe the fluorescence localization images of starch, protein, and lipid in the sample. FITC (0.25%, w / v dissolved in absolute ethanol) and rhodamine B (0.25%, w / v dissolved in absolute ethanol) prepared in advance are used to localize starch and protein in the sample. Mix them in a 1:1 ratio, shake well, and store at low temperature in the dark. Perform cryosectioning on the dough sample, cut out 20-μm-thick slices using a cryostat, place them on a glass slide, then use a pipette to aspirate 10 μl of the above staining solution and drop it on the sample slice. After standing for 3 minutes, rinse it 3 times with deionized water, wipe off the water stains around the sample, and then cover it with a coverslip. Starch (blue) and protein (green) are observed at excitation wavelengths of 488 nm and 568 nm respectively. All samples are observed at 512×512 frames and a scanning speed of 600, and photographed at 1024×1024 frames and a scanning speed of 200.

[0043] Scanning electron microscopy measurement: Fix the dry powder sample on the sample stage with conductive glue, and then coat a thin layer of gold on it with an ion sputtering instrument for 90 s. Then examine the sample with a scanning electron microscope at 3.0 kV.

[0044] Preparation method of degermed corn flour: Place the corn kernels washed by a cleaning machine in a soaking pool, inject warm water at 20-30 °C, and soak for 12-24 h to make the corn kernels fully absorb water and expand; transport the soaked corn kernels to a degerming mill and continuously crush them into 10-12 pieces to preliminarily crush the corn kernels, and use a germ separation cyclone to separate the germ to form a coarsely ground suspension; send the corn suspension from which the germ has been removed into an impact mill again and continuously grind it at high speed for 10-20 min to make the corn particles finer; after grinding, perform fine screening through a 40-100 mesh centrifugal sieve; remove the water from the corn suspension obtained by fine screening at 1200 rpm for 5-10 min using a centrifugal dehydrator, and finally dry it into powder through an air dryer to obtain degermed corn flour.

[0045] Example 1

[0046] The conditions of thermal processing are predicted through the following model:

[0047] Y = 2.0991*t - 0.0518*t 2 -0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0048] The calculation results are shown in Table 11.

[0049] Based on the results of the prediction model, conduct experimental verification:

[0050] Method for making steamed buns: Mix wheat gluten with corn flour at 30% of the dry basis mass of the dehulled corn flour, add water at 55.44% of the total mass of the mixed flour and 1% yeast, and put the mixed flour into a dough mixer to knead the dough. After the dough is formed, ferment it for 40 - 60 min under the conditions of a temperature of 37°C and a relative humidity of 80%, and then carry out steaming treatment with the conditions of a time of 10 min, a temperature of 100°C, and a humidity of 100% RH.

[0051] Digestibility of corn flour in steamed buns:

[0052] To investigate the in vitro digestibility of corn flour in steamed buns, in this example, the content of rapidly digestible starch, slowly digestible starch, and resistant starch in the corn flour of the steamed buns was measured, and the results are shown in Table 1. As can be seen from Table 1, the content of rapidly digestible starch in the corn flour of the steamed buns is about 61%, the content of slowly digestible starch is about 6%, and the content of resistant starch is about 33%.

[0053] Table 1 Determination of in vitro digestibility of corn flour in steamed buns

[0054]

[0055] Example 2

[0056] The conditions of heat treatment are predicted by the following model:

[0057] Y = 2.0991*t - 0.0518*t 2 - 0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0058] The calculation results are shown in Table 11.

[0059] Based on the results of the prediction model, experimental verification is carried out:

[0060] Adjust the conditions in Example 1 to a time of 15 min, a temperature of 100°C, and a humidity of 100% RH. Other conditions are the same as in Example 1.

[0061] Digestibility of corn flour in steamed buns:

[0062] To investigate the in vitro digestibility of corn flour in steamed buns, in this example, the content of rapidly digestible starch, slowly digestible starch, and resistant starch in the corn flour of the steamed buns was measured, and the results are shown in Table 2. As can be seen from Table 2, the content of rapidly digestible starch in the corn flour of the steamed buns is about 62%, the content of slowly digestible starch is about 3%, and the content of resistant starch is about 35%.

[0063] Table 2 Determination of in vitro digestibility of corn flour in steamed buns

[0064]

[0065] Example 3

[0066] The conditions of the thermal processing are predicted by the following model:

[0067] Y = 2.0991*t - 0.0518*t 2 -0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0068] The calculation results are shown in Table 11.

[0069] Based on the results of the prediction model, experimental verification is carried out:

[0070] Adjust the conditions in Example 1 to: time 20 min; temperature 100 °C; humidity 100% RH. Other conditions are the same as those in Example 1.

[0071] Digestibility of corn flour in steamed buns:

[0072] To investigate the in vitro digestion performance of corn flour in steamed buns, the contents of rapidly digestible starch, slowly digestible starch and resistant starch in the corn flour of the steamed buns were measured in this example. The results are shown in Table 3. It can be seen from Table 3 that the content of rapidly digestible starch in the corn flour of the steamed buns is about 67%, the content of slowly digestible starch is about 3%, and the content of resistant starch is about 30%.

[0073] Table 3 Determination of in vitro digestion performance of corn flour in steamed buns

[0074]

[0075] Example 4

[0076] The conditions of the thermal processing are predicted by the following model:

[0077] Y = 2.0991*t - 0.0518*t 2 -0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0078] The calculation results are shown in Table 11.

[0079] Based on the results of the prediction model, experimental verification is carried out:

[0080] Noodle making, characterized in that:

[0081] Mix wheat gluten with corn flour at 30% of the dry basis mass of the degermed corn flour, add water at 47.52% of the total mass of the mixed flour, and put the mixed flour into a dough mixer to form dough flakes. Ferment for 20 min under the conditions of a temperature of 37 °C and a relative humidity of 80%. After kneading into a dough, roll it 10 times. After rolling into noodles, conduct cooking treatment. The conditions are as follows: time 3 min; temperature 100 °C; humidity 100% RH.

[0082] Digestibility of corn flour in noodles:

[0083] To investigate the in vitro digestion performance of corn flour in noodles, in this example, the content of rapidly digestible starch, slowly digestible starch, and resistant starch in the corn flour of the noodles was measured. The results are shown in Table 4. As can be seen from Table 4, the content of rapidly digestible starch in the corn flour of the noodles is approximately 65%, the content of slowly digestible starch is approximately 3%, and the content of resistant starch is approximately 31%.

[0084] Table 4 Determination of in vitro digestion performance of corn flour in noodles

[0085]

[0086] Example 5

[0087] The conditions of the thermal processing treatment are predicted by the following model:

[0088] Y = 2.0991*t - 0.0518*t 2 -0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0089] The calculation results are shown in Table 11.

[0090] Based on the results of the prediction model, conduct experimental verification:

[0091] Adjust the conditions in Example 4 to: time 5 min; temperature 100 °C; humidity 100% RH. Other conditions are the same as those in Example 4.

[0092] Digestibility of corn flour in noodles:

[0093] To investigate the in vitro digestion performance of corn flour in noodles, in this example, the content of rapidly digestible starch, slowly digestible starch, and resistant starch in the corn flour of the noodles was measured. The results are shown in Table 5. As can be seen from Table 5, the content of rapidly digestible starch in the corn flour of the noodles is approximately 67%, the content of slowly digestible starch is approximately 3%, and the content of resistant starch is approximately 29%.

[0094] Table 5 Determination of in vitro digestion performance of corn flour in noodles

[0095]

[0096] Example 6

[0097] The conditions of the thermal processing are predicted by the following model:

[0098] Y = 2.0991*t - 0.0518*t 2 -0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0099] The calculation results are shown in Table 11.

[0100] Based on the results of the prediction model, experimental verification is carried out:

[0101] Adjust the conditions in Example 4 to: time 7 min; temperature 100 °C; humidity 100% RH. Other conditions are the same as in Example 4.

[0102] Digestibility of corn flour in noodles:

[0103] To investigate the in vitro digestion performance of corn flour in noodles, the contents of rapidly digestible starch, slowly digestible starch and resistant starch in the corn flour of the noodles were measured in this example. The results are shown in Table 6. It can be seen from Table 6 that the content of rapidly digestible starch in the corn flour of the noodles is about 72%, the content of slowly digestible starch is about 1%, and the content of resistant starch is about 27%.

[0104] Table 6 Determination of in vitro digestion performance of corn flour in noodles

[0105]

[0106] Example 7

[0107] The conditions of the thermal processing are predicted by the following model:

[0108] Y = 2.0991*t - 0.0518*t 2 -0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0109] The calculation results are shown in Table 11.

[0110] Based on the results of the prediction model, experimental verification is carried out:

[0111] Bread making, characterized in that:

[0112] Mix wheat gluten with corn flour at 30% of the dry basis mass of the degermed corn flour, add water at 55.44% of the total mass of the mixed flour and yeast at 1.5%, and put the mixed flour into a dough mixer to knead the dough. After the dough is formed, ferment it for 40 min under the conditions of a temperature of 37 °C and a relative humidity of 80%, then exhaust and shape it, and then carry out baking treatment. The conditions are as follows: the yeast addition amount is 1.5%; the time is 20 min; the temperature is 180 °C; the humidity is 40% RH.

[0113] Digestibility of corn flour in bread:

[0114] To investigate the in vitro digestibility of corn flour in bread, in this example, the content of rapidly digestible starch, slowly digestible starch and resistant starch in the corn flour of the bread was measured, and the results are shown in Table 7. It can be seen from Table 7 that the content of rapidly digestible starch in the corn flour of the bread is about 61%, the content of slowly digestible starch is about 3%, and the content of resistant starch is about 36%.

[0115] Table 7 Determination of in vitro digestibility of corn flour in bread

[0116]

[0117] Example 8

[0118] The conditions of the thermal processing treatment are predicted by the following model:

[0119] Y = 2.0991*t - 0.0518*t 2 -0.0635*T - 6.2535*LN(100H + 1) + 4.1197*L - 1137.22*A + 90.1704

[0120] The calculation results are shown in Table 11.

[0121] Based on the results of the prediction model, experimental verification is carried out:

[0122] Adjust the conditions in Example 7 to: the yeast addition amount is 1.5%; the time is 25 min; the temperature is 180 °C; the humidity is 40% RH. Other conditions are the same as those in Example 7.

[0123] Digestibility of corn flour in bread:

[0124] To investigate the in vitro digestibility of corn flour in bread, in this example, the content of rapidly digestible starch, slowly digestible starch and resistant starch in the corn flour of the bread was measured, and the results are shown in Table 8. It can be seen from Table 8 that the content of rapidly digestible starch in the corn flour of the bread is about 57%, the content of slowly digestible starch is about 4%, and the content of resistant starch is about 39%.

[0125] Table 8 Determination of in vitro digestibility of corn flour in bread

[0126]

[0127] Example 9

[0128] The conditions of the thermal processing are predicted by the following model:

[0129] Y = 2.0991*t - 0.0518*t 2 - 0.0635*T - 6.2535*LN(100H + 1)+4.1197*L - 1137.22*A + 90.1704

[0130] The calculation results are shown in Table 11.

[0131] Based on the results of the prediction model, experimental verification is carried out:

[0132] Adjust the conditions in Example 7 to: yeast addition amount 1.5%; time 30 min; temperature 180 °C; humidity 40% RH. Other conditions are the same as those in Example 7.

[0133] Digestibility of corn flour in bread:

[0134] To investigate the in vitro digestion performance of corn flour in bread, the rapidly digestible starch content, slowly digestible starch content and resistant starch content of corn flour in bread were measured in this example. The results are shown in Table 9. It can be seen from Table 9 that the rapidly digestible starch content of corn flour in the bread is about 54%, the slowly digestible starch content is about 8%, and the resistant starch content is about 38%.

[0135] Table 9 Measurement of in vitro digestion performance of corn flour in bread

[0136]

[0137] Table 11 Thermal processing parameters and RDS content

[0138]

[0139]

[0140] After inspection, the digestibility of starch in the above staple foods is relatively in line with the thermal processing condition prediction model "Y = 2.0991*t - 0.0518*t2 - 0.0635*T - 6.2535*LN(100H + 1)+4.1197*L - 1137.22*A + 90.1704".

[0141] Comparative Example 1

[0142] The corn flour was pre-gelatinized for 30 min.

[0143] The contents of rapidly digestible starch, slowly digestible starch and resistant starch in corn flour are shown in Table 10.

[0144] Table 10 Determination of in vitro digestibility of corn flour

[0145]

[0146] To further illustrate the regulatory effects of different thermal processing methods and their parameters on the digestibility of corn flour in staple foods, the present invention conducted microstructure analysis on Examples 1-9 and Comparative Example 1 to observe the microstructure of starch and the wrapping and binding state of non-starch components therein. The results are as Figure 1 and Figure 2 shown.

[0147] It can be seen from Figure 1 that for Control Example 1 (unthermally processed corn flour), the starch granules are unevenly distributed and relatively dispersed, and most of the protein and lipid are distributed on the surface of the starch granules, and a very small part is distributed around the starch granules; for Examples 1-9 (thermally processed), the starch granules are more evenly distributed and relatively concentrated. Among them, for Examples 1-3, with the same yeast addition amount, humidity and without being immersed in water, the protein and lipid are also relatively evenly distributed, forming a certain protein network that wraps the starch granules. At the same time, with the extension of time and higher moisture, the gap between the starch granules becomes larger and the structure becomes looser, so it is beneficial for amylase to contact and utilize starch, resulting in its easy digestion; for Examples 4-6, with the same yeast addition amount, humidity and being immersed in water, the distribution of starch granules is relatively uneven. Especially for the samples boiled for 3 minutes, the protein does not form a protein network and cannot play a wrapping role. At the same time, with the extension of time and the environment of being immersed in water during thermal processing, the structure becomes looser and the voids between the starch granules are larger, making it easy to digest; for Examples 7-9, with the same yeast addition amount and without being immersed in water, a protein network is also formed between the starch granules, and the binding with the starch granules is relatively tighter. At the same time, with the extension of time, the increase in temperature and the lower humidity environment, the particle structure becomes tighter, making it difficult for amylase to contact the starch granules and relatively difficult to digest.

[0148] It can be seen from Figure 2It can be seen that there is a small amount of protein adhering to the surface of the starch granules in Comparative Example 1. The starch granules in Examples 1 to 9 are all wrapped in the protein network, and most of the starch granules have been gelatinized, changing from the original spherical shape to an irregular shape, and there is a small amount of starch that has not been gelatinized. For Examples 1 to 9, compared with the untreated corn flour, due to the continuous action of high moisture and high temperature, the aggregation of starch granules is obvious, aggregating into clusters, while the protein is deformed, swelling and adhering to the surface of the starch granules. As time goes by, the degree of gelatinization continues to deepen, the structure of the starch granules is damaged, and cross-linking and fusion phenomena occur. Among them, for Examples 7 to 9, due to the action of the lower humidity environment and high temperature, the attachments on the surface are more tightly combined with the starch granules, which makes it difficult for digestive enzymes to contact the starch granules and affects their digestibility. In addition, due to the environment immersed in water, there are a large number of pores in the samples of Examples 4 to 6. Similarly, due to the high humidity environment, the samples of Examples 1 to 3 are the second, and there is a positive correlation trend with time; the samples of Examples 7 to 9 are the least, and there is a negative correlation trend with time. This may be due to the action of the high moisture existing during the thermal processing of Examples 4 to 6 and Examples 1 to 3. The moisture fills these pores, and after the moisture is removed, pores are left. This is consistent with the results of laser confocal analysis.

[0149] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A method for rationally regulating the digestibility of corn flour in staple foods based on thermal processing parameters, characterized in that: The degerminated corn flour is applied to the staple food system, and the specific processing method is as follows: Mix gluten powder with corn flour at 30% of the dry basis mass of the degerminated corn flour, add water accounting for 47.52% - 55.44% of the total mass of the mixed flour and 0 - 1.5% of yeast, and knead the dough. After the dough is formed, ferment it for 20 - 60 min under the conditions of a temperature of 37°C and a relative humidity of 80%, and then carry out heat treatment processing to obtain a staple food with a rapidly digestible starch (RDS) content of Y; The staple food is steamed bread, noodles or bread; The conditions of the heat treatment are predicted through the following model: Y = 2.0991*t - 0.0518*t 2 - 0.0635*T - 6.2535*LN(100H + 1)+4.1197*L - 1137.22*A + 90.1704 In the formula: Y represents the content of rapidly digestible starch (RDS) under different heat treatment methods; t is the heat treatment time; T is the temperature during heat treatment; H is the humidity during heat treatment; L represents whether it is immersed in water, 1 if immersed, otherwise 0; A represents the yeast addition amount.

2. The method for rationally regulating the digestibility of corn flour in staple foods based on thermal processing parameters according to claim 1, characterized in that: The heat treatment of steamed bread is: steaming treatment; The heat treatment of noodles is: knead the dough into a sheet, roll it into noodles, and then cook it; The heat treatment of bread is: exhaust air, shape it, and then bake it.

3. A method for rationally regulating the digestibility of corn flour in staple foods based on hot processing parameters according to claim 1, characterized in that: The preparation method of the degerminated corn flour is: Place the washed corn kernels in warm water at 20 - 30°C, soak them for 12 - 24 h, break the soaked corn kernels into 10 - 12 pieces, separate the germ to form a coarse grinding suspension, continuously grind at high speed for 10 - 20 min, carry out fine screening through a 40 - 100 - mesh centrifugal sieve, remove moisture by centrifugation at 1200 rpm for 5 - 10 min, and dry it into powder to obtain degerminated corn flour.

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