Method for detecting volatile components of mutton based on ITEX-GC-IMS

Abstract

The invention belongs to the technical field of component detection, and particularly relates to a method for detecting volatile components of mutton based on ITEX-GC-IMS. Comprising the following steps: incubating a sample to be detected to obtain a pretreated sample; performing ITEX headspace sampling on the pretreated sample, performing GC-IMS analysis, and establishing a calibration curve of retention time and retention index of a target object; calculating a retention index of the target object through the retention time of the target object, and comparing the retention index with a retention index database and an IMS migration time database to obtain qualitative analysis of the target object; wherein the parameters of the ITEX headspace sample injection are as follows: the sample injection volume is 500L; the hatching rotating speed is 500r / min; the filling material is Tenax TA 80 / 100 mesh; the temperature of a sample injection needle is 130 DEG C; the dynamic frequency is 12; the adsorption temperature is 40 DEG C; and the desorption temperature is 150 DEG C.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of component detection, and particularly relates to a method for detecting volatile components of mutton based on ITEX-GC-IMS. BACKGROUND

[0002] Traditional headspace sampling techniques, such as static headspace sampling, have obvious limitations in detecting volatile components of mutton, resulting in problems such as loss of target component adsorption, low detection rate of trace components, serious matrix interference, and poor detection reproducibility. Mutton is rich in fat and protein, and its complex matrix can easily produce a large amount of interfering volatiles at high temperatures. The traditional method lacks a selective enrichment mechanism, so that the signals of key flavor components such as aldehydes, esters and terpenes are masked by high background noise. Especially for trace sulfides and nitrogen-containing heterocyclic compounds, the enrichment efficiency of the traditional technology is insufficient, making it difficult to achieve effective detection, resulting in an incomplete flavor profile.

[0003] Although existing adsorption extraction techniques have been applied in environmental or wine analysis, their parameter systems have not been optimized for mutton, a complex biological matrix with high fat content, and lack of adsorption kinetics adaptation to characteristic flavor components. There is also no standardized pretreatment scheme that can effectively overcome matrix interference and ensure analysis reproducibility. Therefore, the existing technology generally has problems such as low capture efficiency, weak anti-interference ability, and insufficient method stability in mutton volatile component analysis. SUMMARY

[0004] To solve the above problems, the application provides a method for detecting volatile components of mutton based on ITEX-GC-IMS.

[0005] The technical solution of the application is as follows.

[0006] A method for detecting volatile components of mutton based on ITEX-GC-IMS, comprising the following steps: Incubate the sample to be detected to obtain a pretreated sample; After ITEX headspace sampling of the pretreated sample, perform GC-IMS analysis to establish a calibration curve of the retention time and retention index of the target substance; Calculate the retention index of the target substance by its retention time, and compare it with the retention index database and IMS migration time database to obtain a qualitative analysis of the target substance.

[0007] The volatile components of the pretreated sample; The parameters of ITEX headspace sampling are as follows: Sample volume: 500 µL; Incubation rotation speed: 500 r / min; Filler: Tenax TA 80 / 100 mesh; Injection needle temperature: 130℃; Dynamic times: 12; Adsorption temperature: 40℃; Desorption temperature: 150℃.

[0008] The adsorption temperature in the present application refers to the temperature of the injection needle and the transmission line of the ITEX system when the enriched headspace sample is pumped, which is set to 40℃, so as to effectively prevent the condensation of low-boiling-point flavor substances (such as acetaldehyde with a boiling point of 20.8℃ and ethanol with a boiling point of 78.4℃), and ensure the transmission efficiency. The desorption temperature refers to the temperature at which the adsorbent tube (Tenax TA) is instantaneously heated to release the captured compounds after the enrichment is completed. It is set to 150℃, which can effectively desorb most of the low-boiling-point mutton flavor substances such as aldehydes, ketones, alcohols and sulfides, and at the same time greatly avoids the occurrence of thermal decomposition reaction. By controlling the adsorption temperature and the desorption temperature of the ITEX system, the anti-interference ability to other components is improved, so as to realize the comprehensive analysis of the volatile components of mutton.

[0009] In another preferred embodiment, the conditions of the GC are as follows: Column temperature: 60℃; Carrier gas: nitrogen; Programmed pressure: initial flow rate 2.0 mL / min for 2 min, linearly increased to 10.0 mL / min within 8 min, linearly increased to 100.0 mL / min within 10 min, and then maintained for 10 min to end; Chromatographic running time: 30 min; Injection port temperature: 80℃.

[0010] In another preferred embodiment, the parameters of the IMS are as follows: Ionization source: tritium source; Migration tube length: 53 mm; Electric field strength: 500 V / cm; Migration tube temperature: 45℃; Drift gas: nitrogen, flow rate 75.0 mL / min; Positive and negative ion mode: positive ion.

[0011] In another preferred embodiment, the temperature of the incubation is 60℃~ and the time is 15 min~.

[0012] In another preferred embodiment, the incubation process further comprises adding an internal standard reagent; The internal standard reagent is a 100 ppm 2-octanol solution.

[0013] In another preferred embodiment, the sample injection is splitless injection.

[0014] In another preferred embodiment, the retention index database is NIST 2020.

[0015] In another preferred embodiment, the mass to volume ratio of the sample to be detected and the internal standard reagent is 0.1g-2g:20mL.

[0016] Compared with the prior art, the present application has the following beneficial effects: The packing material, i.e. the adsorbent, of the ITEX headspace injection in the present application is Tenax TA 80 / 100 mesh, which can efficiently and stably enrich and release various key flavor compounds such as aldehydes, ketones, alcohols, esters and terpenes with carbon number ranging from C6 to C26, and is the basis for ensuring the accuracy and reliability of the analysis results of ITEX-GC-IMS; the injection needle temperature is set to 130 DEG C, which can ensure that the key flavor substances in mutton, such as aldehydes (specifically hexanal and nonanal), ketones (specifically 2-heptanone and 2,3-octanedione), and alcohols (specifically 1-pentanol and 1-octen-3-ol) will not condense during the transmission process. The dynamic cycle set to 12 times can significantly enrich the target volatile substances, so that the concentration of trace flavor substances is increased by several times or even dozens of times, greatly improving the detection sensitivity. This is very beneficial for detecting substances with very low content in mutton but which are crucial to flavor, such as certain sulfides and branched fatty acids. The present application realizes the detection of volatile components in beef and mutton by precisely controlling the ITEX injection conditions. Compared with the traditional method, the present application increases the number of detected target components by 20%, reduces the detection limit to 5ug / kg, and the relative standard deviation is less than or equal to 5%; adapts to the fat matrix of mutton, effectively enriches trace characteristic flavor components, reduces matrix interference, improves detection efficiency, and shortens the sample pretreatment time by 30%. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a gas chromatography condition diagram.

[0018] Figure 2 It is a GC-IMS two-dimensional spectrum of volatile components in the 002 sample.

[0019] Figure 3 It is a GC-IMS two-dimensional spectrum of volatile components in the 003 sample.

[0020] Figure 4 It is a GC-IMS two-dimensional spectrum of volatile components in the 005 sample.

[0021] Figure 5 It is a GC-IMS difference spectrum of volatile components in the 002 sample.

[0022] Figure 6The GC-IMS differential spectrum of volatile components in sample 003 is shown.

[0023] Figure 7 The GC-IMS differential spectrum of volatile components in sample 005 is shown.

[0024] Figure 8 The fingerprint spectrum of volatile components in all samples.

[0025] Figure 9 This is the fingerprint spectrum of volatile components in sample 002.

[0026] Figure 10 This is the fingerprint spectrum of volatile components in sample 003.

[0027] Figure 11 This is the fingerprint spectrum of volatile components in sample 005.

[0028] Figure 12 This is a PCA score plot of the volatile components in the sample.

[0029] Figure 13 The GC-IMS qualitative spectrum of volatile components in sample 002.

[0030] Figure 14 The volatile component qualitative spectrum of the sample 002 is obtained by ITEX-GC-IMS (sample amount is 0.1g).

[0031] Figure 15 The volatile component qualitative spectrum of the sample 002 is obtained by ITEX-GC-IMS (sample amount is 0.2g).

[0032] Figure 16 The volatile component qualitative spectrum of the sample 002 is obtained by ITEX-GC-IMS (sample amount is 0.5g).

[0033] Figure 17 The ITEX-GC-IMS qualitative spectrum of volatile components in sample 002 (sample size: 1g).

[0034] Figure 18 The ITEX-GC-IMS qualitative spectrum of volatile components in sample 002 (sample size: 2g).

[0035] Figure 19 The GC-IMS qualitative spectrum of volatile components in sample 003.

[0036] Figure 20 The volatile component qualitative spectrum of the sample 003 is obtained by ITEX-GC-IMS (sample amount is 0.1g).

[0037] Figure 21The volatile component qualitative spectrum of the sample 003 is obtained by ITEX-GC-IMS (sample amount is 0.2g).

[0038] Figure 22 The volatile component qualitative spectrum of the sample 003 is obtained by ITEX-GC-IMS (sample amount is 0.5g).

[0039] Figure 23 The ITEX-GC-IMS qualitative spectrum of volatile components in sample 003 (sample size: 1g).

[0040] Figure 24 The ITEX-GC-IMS qualitative spectrum of volatile components in sample 003 (sample size: 2g).

[0041] Figure 25 The GC-IMS qualitative spectrum of volatile components in sample 005 is shown.

[0042] Figure 26 The volatile component qualitative spectrum of the sample 005 is obtained by ITEX-GC-IMS (sample amount is 0.1g).

[0043] Figure 27 The volatile component qualitative spectrum of the sample 005 is obtained by ITEX-GC-IMS (sample amount is 0.2g).

[0044] Figure 28 The volatile component qualitative spectrum of the sample 005 is obtained by ITEX-GC-IMS (sample amount is 0.5g).

[0045] Figure 29 The ITEX-GC-IMS qualitative spectrum of volatile components in sample 005 (sample size: 1g).

[0046] Figure 30 The ITEX-GC-IMS qualitative spectrum of volatile components in sample 003 (sample size: 2g). Detailed Implementation

[0047] The technical solutions of this invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0048] 1. Reagents and Materials n-Kelvin: 2-Butanone, 2-Pentanone, 2-Hexanone, 2-Heptanone, 2-Octanone, and 2-Nonanone (all analytical grade), Aladdin Corporation; 99.999% nitrogen; 2-Octanol (analytical grade), Shanghai Yuanye Biotechnology Co., Ltd.; 20 mL headspace vials, Shandong Haineng Scientific Instruments Co., Ltd.; MXT-WAX capillary column (15 m × 0.53 mm, 1.0 μm), Restek Inc., USA.

[0049] FlavourSpec® gas phase ion mobility spectrometer, GAS (Germany, Dortmund); CTC-PAL 3 static headspace autosampler, CTC Analytics AG (Switzerland, Zwingen); ITEX dynamic headspace module, CTC Analytics AG (Switzerland, Zwingen); VOCal data processing software (0.4.10), GAS (Germany, Dortmund).

[0050] 2. Method 2.1 Sample preparation To illustrate the advantages of ITEX headspace sampling, direct headspace was selected as a control for the experiment. Three types of mutton samples were named 002, 003, and 005, as follows: Direct headspace: Take 2g of sample and place it in a 20mL headspace vial. Add 20µL of 100ppm 2-octanol solution (internal standard), incubate at 60℃ for 15min, and then inject the sample.

[0051] ITEX headspace: Take 0.1g, 0.2g, 0.5g, 1g and 2g of sample respectively and place them in a 20mL headspace vial. Add 20µL of 100ppm 2-octanol solution (internal standard), incubate at 60℃ for 15min and then inject the sample.

[0052] 2.2 Headspace injection conditions Direct headspace: Incubation temperature: 60℃; Incubation time: 15min; Injection volume: 500µL; Splitless injection; Incubation speed: 500 r / min; Injection needle temperature: 105℃.

[0053] ITEX headspace: Incubation temperature: 60℃; Incubation time: 15 min; Injection volume: 500 µL; Splitless injection; Incubation speed: 500 r / min; Packing material: Tenax TA 80 / 100 mesh; Injection needle temperature: 130℃; Dynamic number: 12; Adsorption temperature: 40℃; Desorption temperature: 150℃.

[0054] 2.3 GC conditions: Column temperature: 60℃; Carrier gas: High-purity nitrogen (purity ≥99.999%); Programmed pressure ramp: Initial flow rate 2.0 mL / min, held for 2 min, linearly increased to 10.0 mL / min within 8 min, linearly increased to 100.0 mL / min within 10 min, held for another 10 min; Chromatographic run time: 30 min; Injector temperature: 80℃. The gas chromatographic strips are as follows: Figure 1 As shown in Table 2, the specific conditions are as follows.

[0055] Table 2 Gas Chromatography Conditions 2.4 IMS Conditions Ionization source: tritium source (3H); migration tube length: 53 mm; electric field strength: 500 V / cm; migration tube temperature: 45℃; drift gas: high-purity nitrogen (purity ≥99.999%), flow rate: 75.0 mL / min; positive and negative ion mode: positive ion.

[0056] 2.5 Data Processing A mixed standard of six ketones was tested, and calibration curves for retention time and retention index were established. Then, the retention index of the target substance was calculated based on its retention time. The target substance was qualitatively analyzed by searching and comparing the GC retention index database (NIST 2020) and the IMS migration time database built into the VOCal software.

[0057] The VOCal data processing software was used to generate three-dimensional spectra, two-dimensional spectra, difference spectra, fingerprint spectra, and PCA plots of volatile components, which were used to compare volatile organic compounds between samples.

[0058] 3. Results 3.1 Comparative Analysis of Volatile Components in Samples 3.1.1 Comparative Analysis of Volatile Component Spectra in Samples The results are as follows Figures 2-4 As shown, the entire graph has a blue background. The red vertical line at the horizontal axis (1.0) represents the RIP peak, which is the normalized reaction ion peak. The vertical axis represents the gas chromatography retention time (s), and the horizontal axis represents the normalized relative migration time. Each point on either side of the RIP peak represents a volatile organic compound. The color represents the peak intensity, ranging from blue to red, with darker colors indicating greater peak intensity. It can be seen that the types and concentrations of components detected by ITEX headspace sampling are higher than those detected by direct headspace sampling. The types and concentrations of components detected by ITEX headspace sampling gradually increase with increasing sample size, but even with a minimum sample size of 0.1 g, the types and concentrations of components detected are still higher than those detected by direct headspace sampling.

[0059] To further visually compare the differences in volatile components of lamb sampled directly from headspace sampling and via ITEX headspace sampling, spectra from direct headspace sampling (002, 003, 005) were selected as references. Spectra from other samples were subtracted from the references to obtain a comparison chart of the differences between the different samples, as shown below. Figures 5-7 As shown. If the volatile organic compound (VOC) content in the target sample and the reference is the same, the background after subtraction is white. Red indicates that the concentration of the substance in the target sample is higher than that in the reference, and blue indicates that the concentration of the substance in the target sample is lower than that in the reference. Similarly, it can be seen that the types and contents of components detected by ITEX headspace sampling are higher than those detected by direct headspace sampling. The types and contents of components detected by ITEX headspace sampling gradually increase with the increase of the sample size, but the types and contents of components detected by the minimum sample size of 0.1g are still higher than those detected by direct headspace sampling.

[0060] fingerprint spectrum as follows Figures 8-11 As shown, it can be found that 2-methylpropionic acid and (E)-2-methyl-2-butenal were detected only under direct headspace sampling conditions, while the content of acetaldehyde was higher under direct headspace sampling conditions than under ITEX headspace sampling conditions.

[0061] 3.2 Statistical analysis of volatile components Figure 12 It is a PCA score plot of volatile components in the sample. Through the PCA plot, we can roughly understand the overall statistical differences between the samples in each group and the level of parallelism between samples within the group.

[0062] To investigate the differences in volatile aroma components of lamb sampled directly from headspace and sampled via ITEX headspace, PCA was used to reduce the peak height of all detected VOC signals. The results showed that as the sample size increased, the sample sampled via ITEX headspace became further away from the sample sampled directly from headspace.

[0063] 3.2 Qualitative analysis of volatile component spectra in the sample The volatile components of mutton were determined using GC-IMS technology, and the qualitative spectral results are shown below. Figures 13-30 As shown, a total of 41 volatile components were determined in the three samples. 35 volatile substances were determined by direct headspace analysis, and 39 volatile substances were determined by ITEX headspace analysis. A detailed list of volatile components is shown in Table 3.

[0064] Table 3. Detailed list of volatile components in the samples. Note: 1. The suffixes M or D in a substance refer to the monomer and dimer of the same substance, respectively.

[0065] A total of 41 volatile components were determined from the three mutton samples using direct headspace analysis and ITEX headspace analysis. Direct headspace analysis identified 35 volatile substances, while ITEX headspace analysis identified 39 volatile substances.

[0066] 2-Methylpropionic acid and (E)-2-methyl-2-butenal were detected only under direct headspace sampling conditions, while acetaldehyde was detected at higher levels under direct headspace sampling conditions than under ITEX headspace sampling conditions.

[0067] 2-Octanone, methyl acetate, 3-pentanol, butyraldehyde, 2-methylpropanol, 2-pentylfuran, 2-methyl-1-propanol-D, heptanol-D, 1-hexanol-D, 4-heptanone-D, and 2-heptanone-D were detected only under IITEX headspace sampling conditions. In addition, cyclopentanone, 3-methyl-2-butenol, benzaldehyde, 1-nonanol, (E)-2-heptenol, 2-ethylhexanol, 2-propanol, 2-butanol, 3-methyl-3-buten-1-ol, (Z)-2-penten-1-ol, and heptanol were detected only under IITEX headspace sampling conditions. The levels of 1-pentanol, pentanal, 2-pentanone, propionaldehyde, butyraldehyde, tetrahydrofuran, 1-penten-3-ol, 1-octanal, 1-hydroxy-2-propanone, dimethyl sulfide, 1-octen-3-ol, 2-methyl-2-hepten-6-one, butanol, 2-pentanol, 2-butanone, 3-methyl-1-butanol, 3-hydroxy-2-butanone, and acetone were higher under ITEX headspace sampling conditions than under direct headspace sampling conditions, and the levels of most of these substances were higher when the sample size was 1 g or 2 g.

[0068] The levels of most substances detected under sampling conditions of 0.1g and 0.2g were higher than those detected under direct headspace sampling, such as 2-octanone, 2-ethylhexanol, ethanol, pentanol, 1-nonanal, hexanol, 2-butanol, butanol, (E)-2-heptenal, 3-methyl-3-buten-1-ol, 3-pentanol, 2-methyl-1-propanol, (Z)-2-penten-1-ol, and 2-butanone.

[0069] As can be seen from the above results, when the sample amount is small, the method of the present invention can be used to test with a sample amount of 0.1g. When the sample amount is large, considering that too small a sample amount may result in uneven sampling, a sample amount of 0.5g can be used for testing.

[0070] This invention enables the efficient and stable enrichment and release of various key flavor compounds, such as aldehydes, ketones, alcohols, esters, and terpenes, with carbon numbers ranging from C6 to C26, through precise control of the parameters of ITEX headspace sampling. This allows for the detection of volatile components in beef and mutton. Compared with traditional methods, the method of this invention increases the number of target components detected by 20%, reduces the detection limit to 5 μg / kg, and achieves a relative standard deviation of ≤5%.

[0071] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting volatile components of mutton based on ITEX headspace injection, characterized by, The method comprises the following steps: After incubating the sample to be detected, a pretreated sample is obtained; After ITEX headspace sampling of the pretreated sample, GC-IMS analysis is performed to establish a calibration curve of the retention time and retention index of the target substance; The retention index of the target substance is calculated by the retention time of the target substance, and is compared with a retention index database and an IMS migration time database to obtain qualitative analysis of the target substance; The volatile components of the pretreated sample; The parameters of ITEX headspace sampling are as follows: Sample volume: 500 µL; Incubation rotation speed: 500 r / min; Filler: Tenax TA 80 / 100 mesh; Sample needle temperature: 130℃; Dynamic times: 12; Adsorption temperature: 40℃; Desorption temperature: 150℃.

2. The method for detecting volatile components of mutton based on ITEX headspace sampling according to claim 1, characterized in that, The conditions of the GC are as follows: Chromatographic column temperature: 60℃; Carrier gas: nitrogen; Programmed pressure: initial flow rate 2.0 mL / min for 2 min, linearly increased to 10.0 mL / min within 8 min, linearly increased to 100.0 mL / min within 10 min, and then maintained for 10 min to end; Chromatographic running time: 30 min; Injection port temperature: 80℃.

3. The method for detecting volatile components of mutton based on ITEX headspace injection as claimed in claim 1, wherein, The parameters of the IMS are as follows: Ionization source: tritium source; Migration tube length: 53 mm; Electric field intensity: 500 V / cm; Migration tube temperature: 45℃; Drift gas: nitrogen, flow rate 75.0 mL / min; Positive and negative ion mode: positive ion.

4. The method for detecting volatile components of mutton based on ITEX headspace injection according to claim 1, characterized in that, The incubation temperature is 60℃, and the time is 15 min.

5. The method for detecting volatile components of mutton based on ITEX headspace injection according to claim 4, characterized in that, The incubation process also includes adding an internal standard reagent; The internal standard reagent is a 100 ppm 2-octanol solution.

6. The method for detecting volatile components of mutton based on ITEX headspace injection as claimed in claim 1, wherein, The sampling is splitless sampling.

7. The method for detecting volatile components of mutton based on ITEX headspace injection as claimed in claim 1, wherein, The retention index database is NIST 2020.

8. The method for detecting volatile components of mutton based on ITEX headspace injection according to claim 5, characterized in that, The mass-volume ratio of the sample to be detected to the internal standard reagent is 0.1 g-2 g: 20 mL.

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