Method for detecting gelatinization degree of starch

Abstract

The invention belongs to the technical field of analysis and detection, and relates to a method for detecting the gelatinization degree of starch. The invention relates to a starch gelatinization degree detection method, which comprises: 1) adding water to starch, and heating to obtain gelatinized starch; (2) transferring the gelatinized starch obtained in the step (1), adding a solvent to a constant volume, and preparing a series of gelatinized starch standard solutions with different concentrations; (3) respectively measuring response values of the series of standard solutions of the gelatinized starch with different concentrations obtained in the step (2) by adopting an HPLC-CAD detector, and drawing standard curves of the gelatinized starch with different concentrations and the corresponding response values; and 4) substituting the response value of the gelatinized starch to be detected into the standard curve obtained in the step 3) to obtain the concentration of the gelatinized starch to be detected, and then calculating the gelatinization degree of the gelatinized starch to be detected. According to the method, rapid determination can be achieved, the analysis method is about one minute, the starch gelatinization degree can be rapidly determined through a CAD detector (a corresponding standard curve is established), and therefore large-flux rapid sample testing is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis and detection, and relates to a method for detecting the degree of starch gelatinization. Background Art

[0002] The degree of starch gelatinization refers to the degree of maturation of starch during processing, which means that during the processing, the starch absorbs water under the action of high temperature and high pressure, and the starch molecules are transformed from chain-like or even branched micelle structures to network-like hydrocolloids, forming a paste solution, and the water-insoluble starch is transformed into water-soluble gelatinized starch. The higher the gelatinization ratio, the more water is absorbed, which can improve the ability of enzymes to degrade starch, thereby improving the digestibility of starch.

[0003] At present, there are several methods for detecting starch gelatinization degree (including but not limited to):

[0004] Differential scanning calorimetry (DSC), quantitative differential thermal analysis (DTA), rapid viscoanalyzer (RVA), wet method, dynamic rheometer method, enzymatic method, polarized cross disappearance method, but the existing methods have some shortcomings: large amount of material usage, long detection time, complex sample pretreatment, high value of instruments and equipment, not suitable for large-throughput rapid detection, etc.

[0005] Domestic patent CN107631991A uses ultraviolet spectrometer to quickly test starch gelatinization. First, a standard curve of starch gelatinization is made based on the absorbance value at 207nm corresponding to 100% starch gelatinization; secondly, the absorbance value of the starch solution at 207nm is detected; finally, the absorbance value obtained by the detection is substituted into the standard curve formula to calculate the gelatinization degree of the starch solution to be tested.

[0006] For example, using the patented method: A method for rapid trace detection of starch gelatinization (application number CN107631991A), two serious problems were found:

[0007] 1. Poor linearity;

[0008] 2. Poor repeatability;

[0009] The analysis results suggest the following reasons:

[0010] The absorbance test requires the solution to be clear, and the gelatinized starch presents a network of water-containing colloids. Although it is soluble in water, the entire solution is a colloidal suspension. As the degree of gelatinization increases, the suspension state becomes more obvious. This state will seriously lead to poor light transmittance and affect the absorbance detection.

[0011] The patent: A method for detecting the degree of gelatinization of feed starch (application number: CN106770798A) uses amylase to hydrolyze the gelatinized starch into glucose, and uses HPLC for separation and then uses the RI detector to test the glucose content in the sample solution. This method also requires a certain sample pretreatment process, and the RI detector is highly affected by environmental changes. It is limited by the conditions of domestic analytical laboratories, and it is likely that the results obtained at different times will have certain errors. Summary of the invention

[0012] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a method for detecting the degree of starch gelatinization, comprising the following steps:

[0013] 1) Add water to starch and heat to obtain gelatinized starch. The gelatinized starch is used as a 100% starch gelatinization solution and a reference solution.

[0014] 2) taking the gelatinized starch obtained in step 1), adding a solvent to a fixed volume, and preparing a series of gelatinized starch standard solutions with different concentrations;

[0015] 3) using an HPLC-CAD detector to respectively measure the response values ​​of a series of gelatinized starches of different concentrations obtained in step 2), and to draw a standard curve of gelatinized starches of different concentrations and corresponding response values; the HPLC-CAD CAD detector is a universal detector in liquid chromatography, which can detect semi-volatile or non-volatile substances without ultraviolet response.

[0016] 4) Substitute the response value of the gelatinized starch to be tested into the standard curve obtained in step 3) to obtain the concentration of the gelatinized starch to be tested, and then calculate the gelatinization degree of the starch to be tested.

[0017] Preferably, in step 1), the mass ratio of the starch to the water is 60 mg-300 mg starch to 20 ml-100 ml pure water.

[0018] Preferably, in step 1), the water is ultrapure water, and the resistivity of pure water is 18.2 megohms. Ultrapure water has extremely low content of organic and inorganic impurities, which can avoid the interference of these impurities on the test.

[0019] Preferably, in step 1), the heating temperature is 80° C.-95° C., 80° C.-85° C., 85° C.-90° C., 90° C.-95° C. At this temperature, the gelatinization efficiency is high.

[0020] Preferably, in step 1), the heating method is water bath heating. The water bath heating equipment and operation are convenient and simple and the heating uniformity of the sample is good.

[0021] Preferably, in step 1), the heating time is 35 min-50 min. If the heating time is not enough, 100% gelatinization degree cannot be achieved, and if the heating time is too long, the gelatinized starch will decompose. For example, it can be 35 min-40 min, 40 min-45 min, or 45 min-50 min.

[0022] Preferably, in step 2), cooling is further included before removing, and the cooling is to room temperature, such as 20°C-30°C, for example, 20°C-25°C, 25°C-30°C.

[0023] Preferably, in step 2), the solvent is ultrapure water.

[0024] Preferably, in step 3), an analytical column is further provided in front of the CAD detector, preferably a sugar analytical column, which can be purchased on the market.

[0025] Preferably, in step 3), the detection conditions of the HPLC-CAD detector include any one or more of the following features:

[0026] a) Instrument: Thermo Vanquish-CAD;

[0027] b) Chromatographic column: two-way;

[0028] c) Column temperature: 25-30°C;

[0029] d) Flow rate: 0.8-1.0 ml / min;

[0030] e) Injection volume: 3-5ul;

[0031] f) Isocratic elution: 100% ultrapure water as the mobile phase;

[0032] g) Diluent: ultrapure water;

[0033] e) Sample concentration: 2-3 mg / ml;

[0034] i) Running time: 1-5min.

[0035] Preferably, in step 4), the formula for calculating the gelatinization degree of the starch to be tested is the concentration of the gelatinized starch to be tested / the concentration of the starch before gelatinization, wherein the concentration of the starch before gelatinization refers to the concentration of the starch dissolved in water.

[0036] As described above, the present invention has the following beneficial effects:

[0037] 1) The present invention can be rapidly determined, and the analysis method takes about 1 minute. The HPLC-CAD detector can be used to rapidly determine the degree of starch gelatinization (establish a corresponding standard curve), thereby realizing high-throughput rapid testing of samples;

[0038] 2) The trace amount of starch solution to be tested in the present invention: liquid phase analysis test only requires a small amount of sample pure water to be diluted for testing, meeting the requirements of high-throughput testing;

[0039] 3) The sample pretreatment in the present invention is simple: after the starch gelatinization is completed, it only needs to be placed at room temperature for 5 minutes to allow the ungelatinized starch to precipitate before the supernatant is taken to prepare the sample solution, and the operation time is short;

[0040] 4) If the sample to be tested has interference in the subsequent step of the present invention, an analytical column can be selected for separation to increase the specificity and accuracy of the analytical method;

[0041] 5) The instruments and equipment in the present invention are universal: HPLC-CAD is the most common separation equipment, and CAD detectors are currently available in most laboratories, making detection convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Shown is the standard curve diagram in Example 1 of the present invention.

[0043] Figure 2 Shown is the response value of the sample to be tested in Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention.

[0045] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0046] The reagents and experimental tools used in the following examples are all commonly used reagents and experimental tools, and can be purchased from the market.

[0047] Example 1

[0048] 1) Weigh 150 mg of starch accurately and place it in a 150 mL beaker. Add ultrapure water to the starch and heat it in a 95° C. water bath for 40 min to fully gelatinize the starch to obtain gelatinized starch. The gelatinized starch is used as a 100% gelatinization degree starch solution.

[0049] 2) After cooling to room temperature, a certain amount of gelatinized starch obtained in step 1) is respectively transferred into corresponding volumetric flasks, and ultrapure water is added to the scale to prepare a linear solution, thereby preparing a series of gelatinized starch standard solutions with different concentrations;

[0050] 3) Using HPLC-CAD detector, respectively measure the response values ​​of a series of gelatinized starch standard solutions of different concentrations obtained in step 2), and draw standard curves of gelatinized starch of different concentrations and corresponding response values. The specific parameters of HPLC-CAD detector are shown in Table 1, the configuration of gelatinized starch of different concentrations is shown in Table 2, the gelatinized starch of different concentrations and CAD response values ​​are shown in Table 3, and the standard curve is shown in Table 4. Figure 1 , Table 1 Specific parameters of HPLC-CAD detector

[0051]

[0052] Table 2 Configuration of gelatinized starch at different concentrations

[0053]

[0054] Table 3 Gelatinized starch at different concentrations and CAD response values

[0055]

[0056] 4) Dissolve 20g of starch solution in 20ml of water to obtain a gelatinized starch solution with a concentration of 1g / ml. After gelatinization of the gelatinized starch solution with a concentration of 1g / ml, obtain the gelatinized starch solution to be tested. Then, after standing for 5min, take the supernatant, and use HPLC-CAD detector to measure the response value of the sample to be tested, which is 6.7670. Substitute the response value of the gelatinized starch to be tested into the standard curve y=-0.0808x obtained in step 3). 2 +2.2129x+0.8362, the concentration of the gelatinized starch to be tested is obtained to be 0.526 g / ml, and the gelatinization degree of the starch to be tested is obtained according to the concentration of the gelatinized starch to be tested / the concentration of starch before gelatinization to be 52.6%.

[0057] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for detecting starch gelatinization degree, characterized in that: The following steps are involved: 1) adding water to starch and heating to obtain gelatinized starch; 2) taking the gelatinized starch obtained in step 1), adding a solvent to a fixed volume, and preparing a series of gelatinized starch standard solutions with different concentrations; 3) using an HPLC-CAD detector to respectively measure the response values ​​of a series of gelatinized starches of different concentrations obtained in step 2), and drawing a standard curve of gelatinized starches of different concentrations and corresponding response values; 4) Substitute the response value of the gelatinized starch to be tested into the standard curve obtained in step 3) to obtain the concentration of the gelatinized starch to be tested, and then calculate the gelatinization degree of the starch to be tested.

2. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 1), the mass volume ratio of the starch to the water is (60 mg-300 mg): (20 ml-100 ml).

3. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 1), the water is ultrapure water.

4. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 1), the heating temperature is 70°C-95°C.

5. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 1), the heating method is water bath heating.

6. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 1), the heating time is 35 min-50 min.

7. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: Include at least one of the following technical features: In step 2), cooling is also included before removing; In step 2), the solvent is ultrapure water.

8. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 3), an analytical column is also included in front of the CAD detector.

9. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 3), the detection conditions of the HPLC-CAD detector include any one or more of the following characteristics: a) Instrument: Thermo Vanquish-CAD; b) Chromatographic column: two-way; c) Column temperature: 25-30°C; d) Flow rate: 0.8-1.0 ml / min; e) Injection volume: 3-5ul; f) Isocratic elution: 100% ultrapure water as the mobile phase; g) Diluent: ultrapure water; e) Sample concentration: 2-3 mg / ml; i) Running time: 1-5min.

10. The method for detecting the degree of starch gelatinization according to claim 1, characterized in that: In step 4), the formula for calculating the gelatinization degree of the starch to be tested is the concentration of the gelatinized starch to be tested / the concentration of the starch before gelatinization, wherein the concentration of the starch before gelatinization refers to the concentration of the starch dissolved in water.

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