Method for detecting oil content in corn by using low-field nuclear magnetic resonance technology

Abstract

The present invention relates to a method for detecting the oil content in corn by using low-field nuclear magnetic resonance technology, comprising the following steps: (1) subjecting the corn sample to freeze-drying treatment; (2) using a low-field nuclear magnetic resonance analyzer to collect signals from the corn sample to be measured; (3) selecting corn oils of different masses as standard samples for oil quantification, collecting nuclear magnetic signals using the same parameters as those for sample detection to obtain a T2 spectrum; performing linear fitting with the abscissa X being the mass of corn oil and the ordinate Y being the peak area to obtain a linear equation for oil mass; (4) substituting the measured peak area of the corn oil in the corn sample into the above linear equation for oil mass to calculate the oil content in the corn sample. The present invention applies low-field nuclear magnetic resonance technology to the detection of corn oil in agricultural products, verifying the feasibility of this method for oil detection applications in the food field and ensuring accurate and rapid detection of the oil content in agricultural products.

Description

Technical Field

[0001] The present invention belongs to the field of food detection, and particularly relates to a method for detecting the oil content of corn. Background Art

[0002] The Soxhlet extraction technique for measuring fat content is a relatively mature method at present, which is a recognized classic method and also the preferred standard method for grain and oil analysis in China. However, this method takes a long time, is cumbersome to operate, and uses chemical reagents such as petroleum ether. With the development of science and technology and the improvement of people's living standards, in daily life, consumers have higher requirements for food quality and safety detection methods, and rapid food safety detection technology urgently needs to be developed. Compared with other detection technologies, the Low-field nuclear magnetic resonance (LF-NMR) technology has the advantages of economy, environmental protection, accurate data, rapid and non-destructive, etc., and is thus widely used in the food field.

[0003] Since 1945, the first discovery of nuclear magnetic resonance phenomenon by American physicists Bloch and Purcell has made the applied research of nuclear magnetic resonance technology more and more extensive. It is mainly that specific atomic nuclei in the sample substance undergo nuclear transitions and generate nuclear magnetic resonance signals under certain actions to reflect some inherent properties of the sample substance. Usually, nuclear magnetic resonance spectrometers can be divided into two types: high-field nuclear magnetic resonance and low-field nuclear magnetic resonance according to the magnetic field strength of the magnet. Low-field nuclear magnetic resonance refers to nuclear magnetic resonance with a magnetic field strength below 0.5T, which is mainly used for the analysis of the physical properties of samples. The main measurement indexes of LF-NMR are relaxation times, and relaxation refers to 1 the process in which the H nucleus changes from a high-energy state to a low-energy state in a non-radiative manner. LF-NMR mainly reflects the motion properties of specific protons ( 1 H) in the sample by measuring the longitudinal relaxation time T1, the transverse relaxation time T2, and the diffusion coefficient D. To obtain information such as the internal physical and chemical environment and the distribution of water flow in the system to analyze the target components in the sample, the relaxation times T1 and T2 of the sample can be analyzed, that is, the interaction between spins, the environment, and spins. This technology can observe the internal structure of the sample without damage, measure various indexes such as oil, water, and protein in the sample. The fat distribution is generally about 100 ms, and it is generally not affected by the size and shape of the sample, and the detection effect and accuracy are good.

[0004] At present, the standard method for measuring fat content is mainly the Soxhlet extraction method. This method has complex sample pretreatment operations, long required time, low accuracy, and requires organic reagents such as petroleum ether in the experiment, which will cause harm to the human body and the environment.

[0005] At present, there is no method in the existing technology to accurately detect the oil content in agricultural products by low-field nuclear magnetic resonance technology. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for detecting the oil content in corn using low-field nuclear magnetic resonance technology, comprising the following steps:

[0007] (1) Sample pretreatment:

[0008] Freeze-dry the corn sample for 24 h to remove moisture. Take the dried corn sample, accurately weigh the corn sample into a nuclear magnetic resonance sample bottle, and perform signal acquisition after constant temperature static placement;

[0009] (2) Sample determination

[0010] Use a low-field nuclear magnetic resonance analyzer to collect signals from the corn sample to be measured and obtain two main relaxation peaks after inversion. The second relaxation peak is the oil peak, and the peak area is denoted as Ac;

[0011] (3) Standard curve establishment

[0012] Select different masses of corn oil as standard samples for oil quantification, collect nuclear magnetic resonance signals using the same parameters as sample detection, and obtain a T2 spectrum; perform linear fitting with the mass of corn oil on the abscissa X and the peak area on the ordinate Y, and the obtained linear equation for oil mass is denoted as Y = a f X + b f ;

[0013] (4) Calculation of the oil content in the corn sample

[0014] Calculate the oil content according to the following formula: F = (Ac - b f ) / (a f ) × 100%, where F is the oil content and Ac is the oil peak area of the corn sample to be measured.

[0015] Preferably, in step (1), 1 - 5 g is accurately weighed into a nuclear magnetic resonance sample bottle, and signal acquisition is performed after constant temperature static placement at 32°C. More preferably, in step (1), 1 g, 2 g, 3 g, 4 g, or 5 g is accurately weighed into a nuclear magnetic resonance sample bottle, and signal acquisition is performed after constant temperature static placement at 32°C. Further preferably, in step (1), 2 g is accurately weighed into a nuclear magnetic resonance sample bottle, and signal acquisition is performed after constant temperature static placement at 32°C.

[0016] Preferably, in step (1), the same sample is continuously collected 5 times.

[0017] Preferably, in step (2), the number of echoes (NECH) of the low-field nuclear magnetic resonance analyzer for detecting corn oil is 6000.

[0018] Preferably, the waiting time (TW) for repeated sampling of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 1000 - 4000 ms. More preferably, the waiting time (TW) for repeated sampling of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 1500 - 3000 ms. Further preferably, the waiting time (TW) for repeated sampling of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 2000 ms.

[0019] Preferably, the echo time (TE) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 0.1 - 0.9 ms. More preferably, the echo time (TE) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 0.5 - 0.9 ms. Further preferably, the echo time (TE) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 0.7 - 0.9 ms. Further preferably, the echo time (TE) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 0.7 ms.

[0020] Preferably, the number of repeated scans (NS) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 8 - 32 times. More preferably, the number of repeated scans (NS) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 12 - 24 times. Further preferably, the number of repeated scans (NS) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 12 - 16 times. Further preferably, the number of repeated scans (NS) of the low-field nuclear magnetic resonance analyzer during the detection of corn oil in step (2) is 12 times.

[0021] Preferably, the RSD of the 5 - time detection results of the oil content of the corn sample is less than 5%, more preferably less than 3%; further preferably less than 2%.

[0022] The second aspect of the present invention provides an application of using low-field nuclear magnetic resonance technology to improve the stability of the detection results of the oil content in corn. The low-field nuclear magnetic resonance technology parameters are as follows: the number of echo channels (NECH) is 6000, the waiting time for repeated sampling (TW) is 1500 - 3000 ms, the echo time (TE) is 0.5 - 0.9 ms, and the number of repeated scans (NS) is 12 - 16 times; wherein the RSD of the 5 - time detection results of the corn oil content is less than 5%.

[0023] Preferably, the RSD of the 5 - time detection results of the corn oil content is less than 3%. More preferably, the RSD of the 5 - time detection results of the corn oil content is less than 2%.

[0024] Preferably, the weight of the corn sample is 1-5 g; preferably 1 g, 2 g, 3 g, 4 g or 5 g.

[0025] Preferably, the repeat sampling waiting time (TW) is 2000 ms.

[0026] Preferably, the echo time (TE) is 0.5-0.9 ms. More preferably, the echo time (TE) is 0.7-0.9 ms. Further preferably, the echo time (TE) is 0.7 ms.

[0027] Preferably, the number of repeat scans (NS) is 12-24 times. More preferably, the number of repeat scans (NS) is 12-16 times. Further preferably, the number of repeat scans (NS) is 12 times.

[0028] Advantages of the present invention:

[0029] 1. The present invention first applies low-field nuclear magnetic resonance technology to the detection of corn oil in agricultural products, verifying the feasibility of this method for oil detection applications in the food field. At the same time, through condition optimization, the appropriate experimental detection conditions for low-field nuclear magnetic resonance technology are determined. Under these detection conditions, the detection results of agricultural products can show good stability (RSD value less than 5%), ensuring the accurate and rapid detection of the oil content in agricultural products.

[0030] 2. Based on the results of Soxhlet extraction for measuring oil, the present invention develops a rapid nuclear magnetic detection method for the oil content in agricultural products with clear detection conditions and stable results. The detection method of the present invention reduces the sample pretreatment process of the Soxhlet extraction method for measuring oil, avoids the use of chemical reagents, and the RSD value of the measured corn oil content by the low-field nuclear magnetic method is much smaller than that of the Soxhlet extraction method, indicating that the results measured by the low-field nuclear magnetic method are far more accurate than the Soxhlet extraction method and are more suitable for the oil detection of agricultural product corn. Description of the Drawings

[0031] Figure 1 Showing the modulus maximum value of the corn sample under different waiting times;

[0032] Figure 2 Showing the modulus maximum value of pure corn oil under different waiting times;

[0033] Figure 3 Showing the T2 peak area and standard deviation of the corn sample under different echo times;

[0034] Figure 4 Showing the T2 spectrum of the corn sample under different echo times;

[0035] Figure 5 Showing the attenuation degree of the low-field nuclear magnetic signal of the corn sample under different echo times;

[0036] Figure 6 Show the T2 peak area and standard deviation of corn samples under different repeated scan times;

[0037] Figure 7 Show the T2 spectra of corn samples detected under different scan times;

[0038] Figure 8 Show the T2 spectra of corn samples and pure corn oil;

[0039] Figure 9 Show the T2 spectra of pure corn oil standard samples with different masses;

[0040] Figure 10 Show the standard curves of pure corn oil standard samples with different masses;

[0041] Figure 11 Show the linear relationship of corn oil content measured by different methods. Detailed implementation manners

[0042] The embodiments of the present invention will be described in detail below. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0043] Test Example 1: Detection of corn oil content using low-field nuclear magnetic resonance technology

[0044] 1. Test method

[0045] 1.1. Determination of food fat content

[0046] Determine according to GB 5009.6-2016 Determination of fats in foods.

[0047] 1.2. Low-field nuclear magnetic resonance signal acquisition

[0048] 1.2.1. Sample processing method

[0049] Freeze-dry the corn samples in advance for 24 h to remove moisture. Take the dried corn samples, accurately weigh 2.0 g and put them into a nuclear magnetic sample bottle. After constant temperature and static placement in a metal bath at 32 °C, signal acquisition is carried out. The same sample can be continuously collected 5 times.

[0050] 1.2.2. Signal acquisition method

[0051] According to the instrument operation instructions, first use the Free Induction Decay (FID) sequence to calibrate the instrument. Set certain detection parameters under the CPMG sequence and collect the transverse (T2) relaxation signals of the samples. Each sample is taken with three replicates and each sample is scanned five times repeatedly. The relaxation data is expressed as the mean ± standard deviation.

[0052] 1.3. Determination of Instrument Parameters

[0053] The parameters detected by the instrument mainly consist of two parts, namely system parameters and sampling parameters. Among them, the system parameters are determined by the instrument characteristics, environment, and corresponding pulse sequences. Under the FID sequence, the instrument will automatically adjust the parameters, including the center frequency, 90° pulse, and 180° pulse. The sampling parameters are determined by the instrument characteristics and research purposes, mainly including: the number of repeated scans (NS), the repetition wait time (TW), the echo time (TE), and the number of echoes (NECH). Among them, TR has no significant influence, and NECH only needs to ensure that the sample signal is completely attenuated. NECH is set to 6000. Therefore, this experiment mainly examines NS, TW, and TE.

[0054] 1.3.1. Wait Time (TW)

[0055] The repetition wait time is the time from the end of the previous sampling to the start of the next sampling. If TW is set too short, the signal amplitude will decrease during the next sampling. Generally, TW can be set to be greater than 5 times T1 to ensure that the sample signal is restored by at least more than 98%. In this experiment, the echo time (TE) is set to 0.7 ms, the number of repeated scans (NS) is set to 12 times, and the wait time (TW) is set to 1000 ms, 1500 ms, 2000 ms, 2500 ms, 3000 ms, 3500 ms, and 4000 ms respectively. Compare the maximum value of the signal modulus and make it relatively stable as the optimal condition.

[0056] 1.3.2. Echo Time (TE)

[0057] After the action of the radio frequency pulse, the time interval from the initial generation of the transverse magnetization intensity to the reception of the signal is called the echo time. Generally, the half echo time is required to be greater than 6 times the set value of the 90° pulse width. In this experiment, the number of repeated scans (NS) is set to 12 times, the wait time (TW) is set to 2000 ms, and the echo time (TE) is set to 0.1, 0.2, 0.3, 0.5, 0.7, and 0.9 ms respectively. Compare the attenuation degree of the curve and the relaxation information. Finally, the attenuation signal amplitude is the average value of the last ten signal amplitudes.

[0058] 1.3.3. Repeat scan times (NS)

[0059] The number of repeated scans is the number of times the instrument performs repeated sampling. The number of NS settings will affect the signal strength and sampling time of the sample, so it should be set according to the actual signal strength of the sample. In this experiment, the waiting time (TW) is set to 2000ms, the echo time (TE) is set to 0.7ms, and the number of repeated scans (NS) is set to 8, 12, 16, 24 and 32 times respectively. After sampling, the relaxation characteristics and signal-to-noise ratio of the T2 spectrum are compared and analyzed. The signal-to-noise ratio is the average of the first point signal / the last point 10 signals.

[0060] 1.4. Concentration determination of corn oil quantitative standard sample

[0061] Weigh different masses (1g, 2g, 3g, 4g, 5g) of pure corn oil respectively, and establish a calibration curve between the peak area of ​​pure corn oil and the mass of corn oil to obtain equation E1 (Y = a f X+b f ). According to the peak area generated when testing samples of different corn qualities, the concentration of the oil content in the corn is calculated by substituting it into E1 to obtain the consistent oil content in the corn and calculate the oil content of the corn.

[0062] 1.5. Drawing of standard curve

[0063] Drawing of corn oil quantitative standard curve: Weigh different masses of corn oil, take mass as horizontal axis, and plot the oil peak area (A 22 ) is the ordinate and a linear equation is established through least squares regression, as follows:

[0064] Y=a f X+b f (E1).

[0065] 1.6 Calculation of corn oil content

[0066] The corn oil content is calculated according to the following formula: F = (Ac-b f ) / (a f )×100%

[0067] Where F is the oil content, and Ac is the oil peak area of ​​the corn sample to be tested.

[0068] 1.7 Data Analysis

[0069] SAS software was used to perform significant variance analysis on the relaxation data under different treatment conditions, and origin software was used to draw the graph. The T2 spectrum was obtained by multi-component inversion using the analysis software provided by the low-field nuclear magnetic resonance instrument, and the data were expressed as mean ± standard deviation.

[0070] 2. Test Results

[0071] 2.1 Test Results of Instrument Detection Parameter Optimization

[0072] 2.1.1 Waiting Time

[0073] As Figure 1 shown, the modulus maximum values of corn samples remain stable under different waiting times, with no obvious differences, and the variation ranges of the modulus maximum values in the two consecutive measurements are both less than 1%. This indicates that within the selected waiting times, the samples can all recover to the equilibrium state. The waiting times for different samples are different, which is related to their energy release rates. Considering the differences between corn samples and pure corn oil, Figure 2 shows the modulus maximum values of pure corn oil under different waiting times. It can be found that after setting TW to 2000 ms, the modulus maximum values of corn oil samples remain stable with no obvious differences. Therefore, setting TW to 2000 ms can meet the detection requirements of all agricultural product corn samples.

[0074] 2.1.2 Echo Time

[0075] Figure 3 Shows the T2 peak areas and standard deviations of corn samples under different echo times. As the echo time increases, the peak area gradually decreases. When the echo time is after 0.7 ms, the peak area has no obvious differences and the standard deviation is smaller, and the statistical significance of the data is more accurate.

[0076] Figure 4 Shows the T2 spectra of corn samples under different echo times. It can be clearly observed that the echo time causes the T 21 peak to shift to the right and the peak area to decrease significantly. This is caused by the influence of the self-diffusion effect of the oil. The change in the echo time will affect the molecular self-diffusion and the influence of molecular exchange on the relaxation characteristics. The longer the echo time, the stronger the molecular self-diffusion effect, resulting in the prolongation of the transverse relaxation time T2. After 0.7 ms, the change in the echo time will not have a significant impact on the peak area and relaxation time of corn oil. At the same time, the echo time will affect the attenuation degree of the CPMG curve and the distribution range of the relaxation time.

[0077] Figure 5It is the attenuation degree at different echo times. When the echo time is 0.1 ms, the signal amplitude of the sample decays to 106.1922. As the TE prolongs, the T2 relaxation interval gradually increases, and at the same time, the final signal amplitude of the attenuation curve gradually decreases to 38.71756. After the echo time is 0.7 ms, the final signal attenuation amplitude no longer changes significantly, indicating that the signal has decayed completely at this time, and the stability of the peak area is also good, with the RSD less than 0.5%. Therefore, the echo time of 0.7 ms is selected. It should be noted that when the echo time is 0.1 - 0.3 ms, the RSD is greater than 1%; in contrast, when the echo time is 0.5 - 0.9 ms, the RSD is less than 0.7%, confirming that when the echo time is 0.5 - 0.9 ms, the stability of the sample detection results is better (Table 1).

[0078] Table 1 Oil content of corn and result stability at different echo times (TE)

[0079]

[0080]

[0081] 2.1.3. Number of repeated scans

[0082] The number of repeated scans has a direct impact on the peak area of the sample. The larger the peak area, the more repeated scans are required. In Figure 6 , when the number of repeated scans increases, the peak area also increases, from the initial 621.037 to 9594.72. Of course, the time spent on collecting the signal also increases exponentially. After scanning 16 times, the peak area increases significantly, and the standard deviation becomes larger, affecting the accuracy of the results. Scanning 32 times obviously takes much longer, but reduces the detection efficiency. As can be seen from Figure 7 , the T2 spectra obtained by detecting different scanning times all show two peaks. As the number of repeated scans (NS) increases, the peak area also gradually becomes larger, but the change in the number of repeated scans (NS) does not affect the peak appearance time. Some studies have shown that the increase in the number of repeated scans may cause the magnet to heat up, resulting in a slight change in the sample temperature, which can be reflected by the right shift of the T 22 peak. Therefore, considering comprehensively, it is considered that 12 repeated scans are sufficient. At this time, the relaxation characteristics of the sample all show good stability (RSD less than 0.7%). It should be noted that when the number of repeated scans is 32, the RSD is greater than 1%; in contrast, when the number of repeated scans is 12 - 16, the RSD is less than 0.8%, confirming that when the number of repeated scans is 8 - 24, the stability of the sample detection results is better (Table 2).

[0083] Table 2 Oil content of corn and result stability at different numbers of repeated scans (NS)

[0084]

[0085] 2.2. Optimization test comparison of instrument detection parameters

[0086] Since TR has no significant effect on the results, and NECH only needs to ensure that the sample signal is completely attenuated, so NECH is set to 6000. Through the above experiments, NS, TW and TE are optimized. The conditions for measuring corn oil by low-field nuclear magnetic technology are as follows: the number of repeated scans (NS) is 12, the repeated sampling waiting time (TW) is 2000 ms, and the echo time (TE) is 0.7 ms. Figure 8 The T2 spectra of corn samples and pure corn oil are shown. Table 3 is the comparison of the peak shapes of corn samples and pure corn oil. It can be found that the peak emergence time and end time of the two are similar, and there is no obvious difference in the peak top time (p < 0.05), indicating that the optimization results of the low-field nuclear magnetic detection condition parameters can be used for the detection of corn oil.

[0087] Table 3 Comparison of the results of the instrument detection parameter optimization test

[0088]

[0089] Note: The values in the table are expressed as mean ± standard deviation. The same letter "A" indicates no significant difference between different detection objects in each column, and different letters "A" and "B" indicate significant differences between different detection objects in each column (P < 0.05).

[0090] 2.3. Drawing of the standard curve

[0091] Figure 9 The results are obtained by signal acquisition of standard samples prepared from different masses of pure corn oil. Among them, the T 22 peak is the fat peak. As the mass of corn oil increases, the T 22 peak also continuously increases. It can be directly seen from Figure 10 that in the range of the mass of corn oil from 0.05 to 0.4 g, A 22 increases linearly with the increase of mass. The fitted regression equation is Y = 16760X - 16.918, and the correlation coefficient R 2 is 0.9999, indicating a very significant correlation between the two. According to the peak area reading, the corresponding oil mass in the sample can be calculated, and thus the oil content of corn can be calculated.

[0092] 2.4. Quantitative detection test of oil in corn

[0093] The method of the present invention was compared with the national standard method for the determination of food fat (Determination of fat in foods, GB 5009.6-2016). Maize with different masses (1 g, 2 g, 3 g, 4 g, 5 g) was taken respectively for the determination of oil content (n = 5). Among them Figure 11 Figure 11 is the linear relationship of the fat content determined by different methods. There is a good linear correlation between the two methods, and the correlation coefficient is 0.99813, indicating that using pure maize oil as the standard sample to establish the calibration curve can quantify the oil content of agricultural product maize.

[0094] Table 4 shows the maize oil content measured by comparing the traditional Soxhlet extraction method and the low-field nuclear magnetic resonance method. Through significant analysis, it is found that there is no obvious difference in the oil content of maize measured by the low-field nuclear magnetic resonance method compared with the traditional Soxhlet extraction method, indicating that this method can achieve the effect of determining agricultural product maize. The RSD results show that the RSD value of the oil content of maize measured by the low-field nuclear magnetic resonance method is much smaller than that of the Soxhlet extraction method, indicating that the result measured by the low-field nuclear magnetic resonance method is much more accurate than the Soxhlet extraction method and is more suitable for the oil detection of agricultural product maize. And compared with the traditional determination method, the low-field nuclear magnetic resonance method has certain advantages, and the pretreatment operation is simple and fast, which is very suitable as a rapid detection technical means.

[0095] Table 4 Comparison of maize oil measured by low-field nuclear magnetic resonance method and Soxhlet extraction method

[0096]

[0097] Note: The values in the table are expressed as mean ± standard deviation. The same letter "A" indicates no significant difference between different detection methods for maize samples with the same mass in each row (P > 0.05).

[0098] Although the specific implementation of the present invention has been described, those skilled in the art should recognize that various changes and modifications can be made to the present invention without departing from the scope or spirit of the present invention. Therefore, the present invention is intended to cover all such changes and modifications that fall within the scope of the appended claims and their equivalents.

Claims

1. A method for detecting the oil content in corn by using low-field nuclear magnetic resonance technology, characterized in that The method includes the following steps: (1) Sample pretreatment: Freeze-dry the corn sample for 24 h to remove moisture. Take the dried corn sample, accurately weigh the corn sample into a nuclear magnetic resonance sample bottle, and perform signal acquisition after constant temperature standing. (2) Sample determination: After using a low-field nuclear magnetic resonance analyzer to collect signals from the corn sample to be tested, two main relaxation peaks are obtained through inversion. The second relaxation peak is the oil peak, and the peak area is denoted as Ac. (3) Standard curve establishment: Select different masses of corn oil as the standard samples for oil quantification, collect nuclear magnetic resonance signals using the same parameters as those for sample detection, and obtain the T2 spectrum; perform linear fitting with the mass of corn oil as the abscissa X and the peak area as the ordinate Y, and record the obtained linear equation for oil mass as Y = a f X + b f ; (4) Calculation of the oil content in the corn sample Calculate the oil content according to the following formula: F = (Ac - b f ) / (a f ) × 100%, where F is the oil content and Ac is the peak area of the oil in the corn sample to be measured; In step (2), the number of echoes of the low-field nuclear magnetic resonance analyzer for detecting corn oil is 6000; the repeat sampling waiting time of the low-field nuclear magnetic resonance analyzer for detecting corn oil in step (2) is 1500 - 3000 ms; the echo time of the low-field nuclear magnetic resonance analyzer for detecting corn oil in step (2) is 0.7 - 0.9 ms; the number of repeat scans of the low-field nuclear magnetic resonance analyzer for detecting corn oil in step (2) is 12 - 16 times.

2. The method according to claim 1, characterized in that, In step (1), accurately weigh 1 - 5 g into a nuclear magnetic resonance sample bottle, and perform signal acquisition after standing at a constant temperature of 32°C.

3. The method according to claim 1, wherein In step (1), the same sample is continuously collected 5 times.

4. The method according to claim 1, characterized in that In step (2), the repeat sampling waiting time of the low-field nuclear magnetic resonance analyzer for detecting corn oil is 2000 ms.

5. The method according to claim 1, characterized in that, In step (2), the echo time of the low-field nuclear magnetic resonance analyzer for detecting corn oil is 0.7 ms.

6. The method according to claim 1, wherein In step (2), the number of repeat scans of the low-field nuclear magnetic resonance analyzer for detecting corn oil is 12 times.

7. Application of low-field nuclear magnetic resonance technology in improving the stability of detection results of oil content in corn, characterized in that, A method for detecting the oil content in corn by using the low-field nuclear magnetic resonance technology according to any one of claims 1 - 6, wherein the low-field nuclear magnetic resonance technology parameters are as follows: the number of echoes is 6000, the repeat sampling waiting time is 1500 - 3000 ms, the echo time is 0.7 - 0.9 ms, and the number of repeat scans is 12 - 16 times; wherein the RSD of the 5 detection results of the corn oil content is less than 5%.

8. The application according to claim 7, wherein wherein the RSD of the 5 detection results of the corn oil content is less than 3%.

9. The application according to claim 8, wherein wherein the RSD of the 5 detection results of the corn oil content is less than 2%.

10. The application according to claim 7, wherein The weight of the corn sample is 1 - 5 g.

11. The application according to claim 10, wherein The weight of the corn sample is 1 g, 2 g, 3 g, 4 g or 5 g.

12. The application according to claim 7, wherein The low-field nuclear magnetic resonance technology parameters are as follows: the number of echoes is 6000, the repeat sampling waiting time is 2000 ms, the echo time is 0.7 ms, and the number of repeat scans is 12 times.

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