Method for detecting rice aroma substances based on PTR-MS

Abstract

The invention relates to the technical field of food flavor production control, in particular to a method for detecting rice aroma substances based on PTR-MS. The method comprises the following steps: weighing fresh samples in a preset gram weight range for all rice materials to be tested, putting the fresh samples into different headspace bottles, heating at a preset temperature, and keeping the balance for a preset time; after nitrogen is adopted as carrier gas for drying, a sampling system is cleaned; the filtering device and the aroma conveying pipeline are communicated with a headspace bottle filled with a fresh sample in the sample introduction device, and nitrogen at a preset flow rate is introduced; parameters of the PTR-MS instrument are set; the PTR-MS instrument is used for carrying out qualitative analysis on the input carrier gas with the rice aroma substances to obtain the molecular weight and the reaction collision constant K of the qualitative compound 2-AP, and the content of the 2-AP is determined according to the molecular weight and the reaction collision constant K of the qualitative compound 2-AP. According to the scheme, the rice aroma substances can be rapidly detected, and the rice aroma substance detection efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of food flavor production control, and in particular to a method for detecting rice aroma substances based on PTR-MS. Background Art

[0002] 2-Acetyl-1-pyrroline (2-AP), also known as gumorpholine, is a light yellow liquid and a natural aroma substance that is easily soluble in hot water, ethanol and ether. It is also the characteristic compound and main aroma contributor of fragrant rice. 2-AP, as a natural and healthy aroma source in rice, can increase appetite, and the natural nutrition unique to fragrant rice can increase appetite, help digestion, enhance human resistance and improve metabolism.

[0003] The existing method for determining 2-AP mainly uses high performance liquid chromatography (HPLC). However, this method requires the addition of specific derivatization reagents after sample extraction to derivatize 2-AP before detection. The derivatization process requires 24 hours of reaction in a dark room environment. The process is complicated and cumbersome, which seriously affects the efficiency of 2-AP detection. In addition, the sensitivity is also low, and the detection threshold range is small.

[0004] Therefore, a method for detecting rice aroma substances based on PTR-MS is now developed, which can quickly detect rice aroma substances, improve the detection efficiency and detection sensitivity of rice aroma substances, and can detect a wider threshold range. Summary of the invention

[0005] The present invention aims to provide a method for detecting rice aroma substances based on PTR-MS, which can quickly detect rice aroma substances, improve the detection efficiency and detection sensitivity of rice aroma substances, and can detect a wider threshold range.

[0006] The present invention provides the following basic scheme: a method for detecting rice aroma substances based on PTR-MS, comprising the following contents:

[0007] For all the rice materials to be tested, fresh samples within the preset weight range are weighed and placed in different headspace bottles, heated at a preset temperature, and kept in equilibrium for a preset time;

[0008] Nitrogen is used as carrier gas, and after drying, the sampling system is cleaned; wherein the sampling system includes a nitrogen bottle, a filter device, a nitrogen control valve, a sampling device, an aroma delivery pipeline, and a PTR-MS instrument connected in sequence;

[0009] The filtering device and the aroma delivery pipeline are connected to the headspace bottle containing the fresh sample in the sampling device, and nitrogen gas with a preset flow rate is introduced;

[0010] Set the parameters of the PTR-MS instrument;

[0011] The PTR-MS instrument performs qualitative analysis on the input carrier gas carrying rice aroma substances to obtain the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K, and determines the content of 2-AP based on the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K.

[0012] Furthermore, the preset temperature is 80° C., the preset heating equilibrium time is 5-7 minutes, and the preset gram weight range is 0.980-1.020 g.

[0013] Furthermore, when the sample injection system is cleaned, the connected headspace bottle is a headspace bottle that is not filled with fresh sample.

[0014] Furthermore, the flow rate is set to 0.1 mL / min.

[0015] Furthermore, the parameters of the PTR-MS instrument are set as follows: the temperatures of the injection port and the ion source are both 40° C., the temperature in the drift tube is 80° C., the drift tube voltage for measuring volatile aroma substances in fragrant rice grains is 550 V, the drift pressure is 2.30 mbar, the E / N value is 125 Td, and the injection flow rate is 100 sscm.

[0016] Furthermore, the determination of the 2-AP content includes: using a PTR-MS instrument to measure the 2-AP content of a sample of each variety of rice, collecting each sample for 3 minutes, selecting 30 cycles after equilibrium for concentration calculation, and taking the average value as the 2-AP content of the sample variety.

[0017] Beneficial effects of this scheme: PTR-MS is an online detection technology for trace volatile organic compounds. The principle is a high-sensitivity gas phase analysis technology. It uses proton transfer reaction to generate ions, and analyzes the mass / charge ratio (m / z) of the ions by mass spectrometer to determine the type and concentration of compounds in the sample. In this scheme, for all the rice materials to be tested, fresh samples within a preset gram weight range are weighed in different headspace bottles, heated at a preset temperature in a water bath, and balanced for a preset time to ensure the volatilization of rice aroma substances. At the same time, the sampling system is first cleaned with nitrogen, and then nitrogen is used as a carrier gas and passed into the headspace bottle to carry the rice aroma substances through the aroma delivery pipeline into the PTR-MS instrument. PT R-MS is an online detection technology for trace volatile organic compounds. It uses a PTR-MS instrument to detect rice aroma substances. The PTR-MS instrument conducts qualitative analysis on the input carrier gas with rice aroma substances to obtain the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K. The content of 2-AP is determined based on the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K. There is no need to add specific derivatization reagents after sample extraction. 2-AP can only be detected after derivatization. The derivatization process needs to react in a darkroom environment for 24 hours. It can quickly detect rice aroma substances, improve the detection efficiency and sensitivity of rice aroma substances, and detect a wider threshold range. The detection efficiency of this scheme is more than five times that of existing methods, and it can quickly detect large quantities of samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a method for detecting rice aroma substances based on PTR-MS according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the structural connection of a sampling system in an embodiment of a method for detecting rice aroma substances based on PTR-MS of the present invention. DETAILED DESCRIPTION

[0020] The following is further described in detail through specific implementation methods:

[0021] The reference numerals in the drawings of the specification include: headspace bottle 1, nitrogen bottle 2, filtering device 3, nitrogen control valve 4, sampling device 5, aroma delivery pipeline 6, PTR-MS instrument 7.

[0022] The embodiment is basically as shown in the attached Figure 1 As shown: A method for detecting rice aroma substances based on PTR-MS, comprising the following contents:

[0023] S1. For all the rice materials to be tested, fresh samples within a preset weight range are weighed into a headspace bottle 1, and heated in a water bath at a preset temperature, and the balance is maintained for a preset time. In this embodiment, the preset temperature is 80° C. and the preset heating balance time is 5-7 min; in this embodiment, 1 g (accurate value 0.001) is weighed, and the allowable error range in the actual operation process is 0.980-1.020 g;

[0024] S2. Use nitrogen as carrier gas, dry it, and then clean the injection system;

[0025] Specifically, the headspace sampling method is adopted, and high-purity nitrogen is used as the carrier gas. After the carrier gas is filtered through activated carbon, the nitrogen control valve 4 is opened to clean the pipeline in the sampling system with the filtered and dried nitrogen to ensure that there are no factors that interfere with the test in the pipeline. The sampling system, such as Figure 2 As shown, it includes: a nitrogen bottle 2, a filtering device 3, a nitrogen control valve 4, a sampling device 5, an aroma delivery pipeline 6, and a PTR-MS instrument 7; one end of the filtering device 3 is connected to the nitrogen bottle 2, and the other end is connected to the head space bottle 1 in the sampling device 5, and a nitrogen control valve 4 is provided on the connecting pipeline, and the head space bottle 1 of the sampling device 5 is also connected to the PTR-MS instrument 7 through the aroma delivery pipeline 6; when cleaning, the connected head space bottle 1 is a head space bottle 1 without a fresh sample, and a plurality of head space bottles 1 can be placed in one sampling device 5;

[0026] S3, the filtering device 3 and the aroma delivery pipeline 6 are connected to the headspace bottle 1 containing the fresh sample in the sampling device 5, and nitrogen gas with a preset flow rate is introduced;

[0027] Specifically, two needles at the carrier gas outlet of the filter device 3 and the sample inlet of the aroma delivery pipeline 6 were inserted into the upper end of the headspace bottle 1 containing the fresh sample, and nitrogen was introduced, with the flow rate set to 0.1 mL / min;

[0028] S4, setting parameters of the PTR-MS instrument 7;

[0029] Specifically, the temperatures of the injection port and ion source of the PTR-MS instrument 7 were both 40° C., the temperature in the drift tube was 80° C., the drift tube voltage for measuring the volatile aroma substances of the fragrant rice grains was 550 V, the drift pressure was 2.30 mbar, the E / N value was 125 Td, and the injection flow rate was 100 sscm;

[0030] S5, the PTR-MS instrument 7 performs a qualitative analysis on the input carrier gas carrying the rice aroma substance, obtains the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K, and determines the content of 2-AP according to the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K;

[0031] Specifically, the PTR-MS instrument 7 determines the 2-AP content of the sample of each variety of rice. PTR-MS is an online detection technology for trace volatile organic compounds. The flow rate of the inlet of the PTR-MS instrument 7 is 100sscm. Each sample is collected for 3 minutes. 30 cycles after equilibrium are selected for concentration calculation, and the average value is taken as the 2-AP content of the variety of the sample; the average is the state in which the test line in the PTR-MS instrument 7 tends to be a straight line, which is equilibrium, 1s is a cycle, and selecting at least 30 cycles is beneficial to reduce errors, and the average value is taken as the 2-AP content of the variety of the sample.

[0032] In the above steps, steps S2-S5 are controlled by high-precision test control software. Specifically, TOF software is used, and the operation process is as follows:

[0033] After opening the TOF software, pressurize (turn on ALL ON) and wait for about 1 minute until all indicators reach the preset value. If the pressure values ​​are all 0, load the TPS setting folder and select the TPS-20220925.iTPS file. This needs to be done when the pressure and water are turned off; the indicators are the parameters of PTR-MS instrument 7;

[0034] Add water (select H2O in Setting), check whether PC and p Drift have reached the preset values, and whether H2O has reached 6 sccm. Set Udrift to 550 (E / N corresponds to 125 or 124);

[0035] Perform three-point peak calibration, check whether peaks 19, 21, and 37 are correct, view in Log y-Scale mode, right-click AutoScaleX and Y to display the peak status, cancel Peak Fit and Single Spec on the right side of the interface to remove interference, making it easier to see the peaks; for sample measurement, adjust to Lin y-Scale mode, check 21.022 (water ion), 19, 57 and 112.11 (02-AP molecular mass is 111.14, plus one H ion) in the proton box on the right. If the required 112 is not in the proton box, it needs to be imported.

[0036] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for detecting rice aroma substances based on PTR-MS, characterized in that: It includes the following: For all the rice materials to be tested, fresh samples within the preset weight range are weighed and placed in different headspace bottles, heated at a preset temperature, and kept in equilibrium for a preset time; Nitrogen is used as carrier gas, and after drying, the sampling system is cleaned; wherein the sampling system includes a nitrogen bottle, a filter device, a nitrogen control valve, a sampling device, an aroma delivery pipeline, and a PTR-MS instrument connected in sequence; The filtering device and the aroma delivery pipeline are connected to the headspace bottle containing the fresh sample in the sampling device, and nitrogen gas with a preset flow rate is introduced; Set the parameters of the PTR-MS instrument; The PTR-MS instrument performs qualitative analysis on the input carrier gas carrying rice aroma substances to obtain the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K, and determines the content of 2-AP based on the molecular weight of the qualitatively determined compound 2-AP and its reaction collision constant K.

2. The method for detecting rice aroma substances based on PTR-MS according to claim 1, characterized in that: The preset temperature is 80° C., the preset heating equilibrium time is 5-7 minutes, and the preset gram weight range is 0.980-1.020 g.

3. The method for detecting rice aroma substances based on PTR-MS according to claim 1, characterized in that: When the sample injection system is cleaned, the connected headspace bottle is a headspace bottle that is not filled with fresh sample.

4. The method for detecting rice aroma substances based on PTR-MS according to claim 1, characterized in that: The flow rate was set to 0.1 mL / min.

5. The method for detecting rice aroma substances based on PTR-MS according to claim 1, characterized in that: The parameters of the PTR-MS instrument are set as follows: the temperatures of the injection port and the ion source are both 40° C., the temperature in the drift tube is 80° C., the drift tube voltage for measuring volatile aroma substances in fragrant rice grains is 550 V, the drift pressure is 2.30 mbar, the E / N value is 125 Td, and the injection flow rate is 100 sscm.

6. The method for detecting rice aroma substances based on PTR-MS according to claim 1, characterized in that: The determination of the 2-AP content includes: using a PTR-MS instrument to measure the 2-AP content of a sample of each variety of rice, collecting each sample for 3 minutes, selecting 30 cycles after equilibrium for concentration calculation, and taking the average value as the 2-AP content of the sample variety.

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