GC-IMS (Gas Chromatography-Insulated Mass Spectrometry)-based method for rapidly identifying difference between vinasse processing time

Abstract

The invention provides a GC-IMS (Gas Chromatography-Insulated Mass Spectrometry)-based method for quickly identifying the vinasse preparation time and aroma difference of fish blocks, which comprises the following steps of: incubating fish meat samples in different vinasse preparation stages in a headspace sampling bottle to obtain an incubated sample, extracting a gas sample from the incubated sample by using a sampling needle, and analyzing the extracted gas sample by using a gas chromatography-mass spectrometry (GC-IMS); the extracted gas sample enters a headspace gas chromatography-ion mobility spectrometry combined instrument through a sample injection needle to be measured; detecting the to-be-detected fish block sample by using the same instrument condition; comparing and analyzing the to-be-detected fish blocks and the fish blocks in different vinasse processing stages in the database to confirm the vinasse processing stages of the fish blocks; according to the method disclosed by the invention, the GC-IMS technology is applied to carry out collection and trace analysis on complex aroma substances in the fish blocks in different vinasse processing stages, relatively comprehensive fingerprint information is provided for quality control of the fish blocks, and the vinasse processing stages of the fish blocks are determined according to corresponding characteristic indexes and difference components of the fish blocks in different vinasse processing stages; and rapid and accurate quality confirmation of the fish blocks in different grain pickling stages is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of analytical detection, and particularly relates to a method for rapidly identifying the pickling time and aroma difference of fish chunks based on GC-IMS. Background Art

[0002] Sour soup is a traditional fermented food in Guizhou region. According to different fermentation raw materials and ingredients, it can be divided into fish chunks, white sour soup, pickled sour soup and other types. Among them, fish chunks have become the most common and widely loved type of sour soup products on the market due to their attractive red-orange color, pleasant aroma, and mellow, sour and sweet taste. Red sour soup not only has an appetizing effect, but also its rich nutritional components are of great significance to human health. There are many ways to make red sour soup. The traditional folk method uses fresh tomatoes and red peppers as the main raw materials. After being mashed, they are put into a fermentation vat and added with white wine, glutinous rice, salt, etc., and fermented for a certain period of time. It is a traditional flavor food of the Miao people and has the characteristics of ethnic minority food culture. Red sour soup not only has a bright red color, fresh, sour and delicious taste, sour and spicy mellow taste, and sweet aftertaste, but also contains a variety of functional substances such as organic acids, lycopene, and capsaicin, and has the effects of antioxidant, cancer prevention, and immune enhancement. Use red sour soup to ferment and season fish chunks, and study the flavor mechanism during the process of pickling fish chunks with red sour soup.

[0003] The formation pathway of the aroma of fish chunks is complex and difficult to control. At present, the gas chromatography-mass spectrometry (GC-MS) technology is mainly used to detect the volatile flavor substances of fish chunks. During the detection, the temperature is usually raised above 200°C, which will damage some thermally unstable substances in the fish chunks. Therefore, the detection results may deviate from the true situation of the distribution of volatile substances in the fish chunks. In addition, before the detection, the sample needs to be pretreated to enrich the volatile components. The extraction process is not only complex and cumbersome but also time-consuming. Usually, it takes dozens of minutes or even several hours of extraction to inject the sample for detection, which is very inconvenient. Summary of the Invention

[0004] In view of the above situation, the main purpose of the present invention is to propose a method for rapidly identifying the pickling time and aroma difference of fish chunks based on GC-IMS to solve the above technical problems.

[0005] The present invention proposes a method for rapidly identifying the pickling time and aroma difference of fish chunks based on GC-IMS, and the method includes the following steps: Step 1: Incubate the fish samples at different marinating stages in a headspace vial to obtain incubated samples. Use a syringe to extract gas samples from the incubated samples. The extracted gas samples enter a gas chromatography-ion mobility spectrometry (GC-IMS) instrument through the syringe for measurement to obtain analysis results. Based on the analysis results, generate the volatile aroma components of the fish blocks at different marinating stages through the supporting software and plug-ins, and establish a database of GC-IMS flavor fingerprint maps. Step 2: Detect the fish block sample to be measured under the same instrument conditions as in Step 1 to obtain the GC-IMS fingerprint map of the volatile aroma components of the fish block to be measured. Step 3: Confirm the marinating stage of the fish block by comparing and analyzing the fish block to be measured and the fish blocks at different marinating stages in the database.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Through the analysis of the full-spectrum information of volatile substances at different marinating stages of fish blocks, the present invention comprehensively explores the information of volatile aromatic substances in fish blocks. On the basis of principal component analysis, the present invention introduces similarity analysis for verification analysis, and double verification ensures the accuracy of the analysis results, and establishes a method for distinguishing different marinating stages of fish blocks based on aroma substance fingerprint maps.

[0007] 2. By applying GC-IMS, the aroma components of fish blocks can be measured more comprehensively, quickly, and accurately without sample pretreatment. Through double verification, the marinating stage of fish blocks can be reliably analyzed and distinguished, realizing the rapid and accurate identification and analysis of different marinating stages of fish blocks, which is of great significance for promoting the high-quality production of fish blocks.

[0008] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the embodiments of the present invention. Description of the Drawings

[0009] Figure 1 is a 3D gas chromatography-ion mobility spectrometry diagram of fish blocks at different marinating stages; Figure 2 is the GC-IMS fingerprint map of fish blocks at different marinating stages; Figure 3 is the Gallery Plot diagram of fish blocks at different marinating stages; Figure 4 is the principal component analysis diagram of fish blocks at different marinating stages. Detailed Embodiments

[0010] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where like or similar reference numerals denote like or similar elements or elements having like or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0011] Referring to the following description and the accompanying drawings, these and other aspects of the embodiments of the present invention will be clear. In these descriptions and drawings, some specific embodiments in the embodiments of the present invention are specifically disclosed to represent some ways of implementing the principles of the embodiments of the present invention. However, it should be understood that the scope of the embodiments of the present invention is not limited thereto. Embodiment

[0012] This embodiment provides a method for quickly identifying the marinating time and aroma differences of fish blocks based on GC-IMS. The method is used to obtain a database of GC-IMS flavor fingerprint spectra. The method includes the following steps: Step 1: Take 2 g of fish meat sample into a 20 ml headspace vial, incubate it at 50 °C for 10 min to obtain an incubated sample. Use an injection needle at 80 °C to extract 50 μL of gas sample from the incubated sample. The extracted gas sample enters a gas chromatography-ion mobility spectrometry (GC-IMS) through the injection needle for determination to obtain an analysis result. The analysis result generates volatile aroma components of fish blocks at different marinating stages through VOCal software, Reporter plug-in, Gallery Plot plug-in, and Dynamic PCA plug-in, and establishes a database of GC-IMS flavor fingerprint spectra, denoted as A1; Among them, the specific steps for the extracted gas sample to enter the gas chromatography-ion mobility spectrometry through the injection needle for determination include the following steps: The gas sample enters the gas chromatography-ion mobility spectrometry through the injection needle, passes through an MXT-WAX chromatographic column, and sets a carrier gas program for gradient separation to obtain a retention time; The gas sample enters the gas chromatography-ion mobility spectrometry through the injection needle and migrates through a drift tube to obtain a migration time; Qualitatively and quantitatively analyze the compounds based on the retention time and migration time to obtain an analysis result; Among them, the length of the drift tube is 98 mm, the linear voltage inside the drift tube is 500 V / cm, the temperature of the drift tube is 45 °C, the drift gas is N2, the drift gas flow rate is 150 mL / min, the liquid film thickness of the stationary liquid of the MXT-WAX chromatographic column is 1 μm, the radiation source of the MXT-WAX chromatographic column is β ray (tritium, 3H), the ionization mode of the MXT-WAX chromatographic column is positive ion, the carrier gas is N2, and the carrier gas program is: 0 - 2 min: The carrier gas flow rate is 2 mL / min; 2 - 10 min: The carrier gas flow rate linearly ramps up from 2 mL / min to 10 mL / min; 10 - 20 min: The carrier gas flow rate linearly ramps up from 10 mL / min to 100 mL / min; 20 - 50 min: The carrier gas flow rate remains constant at 100 mL / min until the separation is complete. Example

[0013] This example provides a method for rapidly identifying the pickling time and aroma differences of fish blocks based on GC-IMS. The method is used to obtain a database of GC-IMS flavor fingerprint spectra. The method includes the following steps: Step 1: Take 3.5 g of fish meat sample into a 20 ml headspace vial, incubate it at 60 °C for 15 min to obtain an incubated sample. Use an 85 °C injection needle to extract 100 μL of gas sample from the incubated sample. The extracted gas sample enters a gas chromatography-ion mobility spectrometry (GC-IMS) through the injection needle for measurement to obtain an analysis result. The analysis result generates the volatile aroma components of fish blocks at different pickling stages through VOCal software, Reporter plugin, Gallery Plot plugin, and Dynamic PCA plugin, and establishes a database of GC-IMS flavor fingerprint spectra, denoted as A2; Among them, the specific steps for the extracted gas sample to enter the gas chromatography-ion mobility spectrometry through the injection needle for measurement are as follows: The gas sample enters the gas chromatography-ion mobility spectrometry through the injection needle, passes through an MXT-WAX chromatographic column, and a carrier gas program is set for gradient separation to obtain the retention time; The gas sample enters the gas chromatography-ion mobility spectrometry through the injection needle and migrates through a drift tube to obtain the migration time; Qualitatively and quantitatively analyze the compounds based on the retention time and migration time to obtain the analysis result; Among them, the drift tube length is 98 mm, the linear voltage inside the drift tube is 500 V / cm, the drift tube temperature is 45 °C, the drift gas is N2, the drift gas flow rate is 150 mL / min, the liquid film thickness of the stationary phase of the MXT-WAX chromatographic column is 1 μm, the radiation source of the MXT-WAX chromatographic column is β ray (tritium, 3H), the ionization mode of the MXT-WAX chromatographic column is positive ion, the carrier gas is N2, and the carrier gas program is: 0 - 2 min: The carrier gas flow rate is 2 mL / min; 2 - 10 min: The carrier gas flow rate linearly ramps up from 2 mL / min to 10 mL / min; 10 - 20 min: The carrier gas flow rate is linearly increased from 10 mL / min to 100 mL / min; 20 - 50 min: The carrier gas flow rate remains constant at 100 mL / min until the separation is completed. Example

[0014] This example provides a method for quickly identifying the pickling time and aroma differences of fish blocks based on GC-IMS. The method is used to obtain a database of GC-IMS flavor fingerprint spectra, and the method includes the following steps: Step 1: Take 5 g of fish meat sample into a 20 ml headspace vial, incubate at 70 °C for 20 min to obtain an incubated sample. Use a 90 °C injection needle to extract 150 μL of gas sample from the incubated sample. The extracted gas sample enters the gas chromatography-ion mobility spectrometry (GC-IMS) through the injection needle for determination to obtain an analysis result. The analysis result generates the volatile aroma components of fish blocks at different pickling stages through VOCal software, Reporter plugin, Gallery Plot plugin, and Dynamic PCA plugin, and establishes a database of GC-IMS flavor fingerprint spectra, denoted as A3; Among them, the specific steps for the extracted gas sample to enter the gas chromatography-ion mobility spectrometry through the injection needle for determination are as follows: The gas sample enters the gas chromatography-ion mobility spectrometry through the injection needle, passes through the MXT-WAX chromatographic column, and sets a carrier gas program for gradient separation to obtain the retention time; The gas sample enters the gas chromatography-ion mobility spectrometry through the injection needle, migrates through the drift tube to obtain the migration time; Qualitatively and quantitatively analyze the compounds based on the retention time and migration time to obtain the analysis result; Among them, the drift tube length is 98 mm, the linear voltage inside the drift tube is 500 V / cm, the drift tube temperature is 45 °C, the drift gas is N2, the drift gas flow rate is 150 mL / min, the liquid film thickness of the stationary phase of the MXT-WAX chromatographic column is 1 μm, the radiation source of the MXT-WAX chromatographic column is β ray (tritium, 3H), the ionization mode of the MXT-WAX chromatographic column is positive ion, the carrier gas is N2, and the carrier gas program is: 0 - 2 min: The carrier gas flow rate is 2 mL / min; 2 - 10 min: The carrier gas flow rate is linearly increased from 2 mL / min to 10 mL / min; 10 - 20 min: The carrier gas flow rate is linearly increased from 10 mL / min to 100 mL / min; 20 - 50 min: The carrier gas flow rate remains constant at 100 mL / min until the separation is completed. Example

[0015] This example provides a method for quickly identifying the marinating time and aroma differences of fish blocks based on GC-IMS. The method is used to confirm the marinating stage of fish blocks and includes the following steps: Step 1: Detect the fish block sample to be tested under the same instrument conditions as in Example 1 to obtain the GC-IMS fingerprint of the volatile aroma components of the fish block to be tested, denoted as B1; Step 2: Compare and analyze the database A1 of the GC-IMS flavor fingerprint with the GC-IMS fingerprint B1 of the volatile aroma components of the fish block to be tested to confirm the marinating stage of the fish block. Example

[0016] This example provides a method for quickly identifying the marinating time and aroma differences of fish blocks based on GC-IMS. The method is used to confirm the marinating stage of fish blocks and includes the following steps: Step 1: Detect the fish block sample to be tested under the same instrument conditions as in Example 1 to obtain the GC-IMS fingerprint of the volatile aroma components of the fish block to be tested, denoted as B2; Step 2: Compare and analyze the ion peak map in the GC-IMS fingerprint B2 of the volatile aroma components of the fish block to be tested and the ion peak map in the database A1 of the GC-IMS flavor fingerprint of the fish meat samples at different marinating stages by jointly plotting the GalleryPlot graph to confirm the marinating stage of the fish block. Example

[0017] This example provides a method for quickly identifying the marinating time and aroma differences of fish blocks based on GC-IMS. The method is used to confirm the marinating stage of fish blocks and includes the following steps: Step 1: Detect the fish block sample to be tested under the same instrument conditions as in Example 1 to obtain the GC-IMS fingerprint of the volatile aroma components of the fish block to be tested, denoted as B3; Step 2: Perform principal component analysis on the relative contents of the volatile aroma substances in the GC-IMS fingerprint B3 of the volatile aroma components of the fish block to be tested and the relative contents of the volatile aroma substances in the database A1 of the GC-IMS flavor fingerprint of the fish meat samples at different marinating stages, and jointly plot a scatter diagram based on the principal component scores of the fish blocks for comparison to confirm the marinating stage of the fish block.

[0018] To verify the effectiveness of the present invention, the volatile aroma components of fish blocks at different marinating stages were detected, and the 3D gas chromatography-ion mobility spectrometry diagram of the volatile aroma components of fish blocks at different marinating stages is as Figure 1 shown. Figure 3The abscissa is the drift time (Dt), and the ordinate is the gas-phase retention time (Rt). A vertical line on the left side of the spectrum is the reactant ion peak (RIP). Each point on both sides of the RIP peak represents a volatile organic compound. The color represents the concentration of the substance, white indicates a lower concentration, red indicates a higher concentration, and the darker the color, the greater the concentration. The entire spectrum represents the headspace components of the sample, and qualitative analysis of the substances can be carried out according to the NIST database and IMS database built into the application software.

[0019] The main aroma substances in fish pieces at different marinating stages are shown in Table 1 below; Table 1: Main aroma substances in fish pieces at different marinating stages

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027] In Table 1, M represents monomer, D represents dimer, T1 represents trimer, T2 represents tetramer; the numbers 1-8 represent unidentified compounds.

[0028] The GC-IMS fingerprint spectra of fish pieces at different marinating stages are as Figure 2 shown; by Figure 2It can be seen that fish pieces at different marinating stages can be well distinguished, and the content and quantity of volatile components in fish pieces gradually increase with the prolongation of marinating time. Ethanol M, n-pentanol M, n-pentanol D, iso-pentanol D, cis-3-hexenol M, cis-3-hexenol T2, n-heptanal D, trans-2-pentenal D, n-hexanal D, terpinene D, n-heptanal M, 2-nonanone D, trans-2-pentenal M, beta-pinene D, allyl isothiocyanate D, 2,3-dimethylpyrazine, terpinolene D, p-cymene D, dipentene T1, methyl isovalerate, etc. are the main substances on the 1st day of fermentation. Among them, alcohols are particularly prominent. Alcohol substances are mainly metabolites produced by the action of yeasts, having certain floral and fruity aromas. At the initial stage of fermentation, starch sugar is converted into alcohol substances, providing precursor substances for the formation of organic acids and ester substances, and promoting the formation of flavor. For example, ethanol provides the wine aroma and fruity flavor of fish pieces, and can also promote its dissolution with other volatile flavor substances. n-pentanol and iso-pentanol provide nutty flavors. Iso-pentanol, acetic acid M, acetic acid D, myrcene, n-hexanol M, eucalyptol D, isoamyl acetate D, 4-hydroxy-4-methyl-2-pentanone M, p-xylene, o-xylene, isopropylidene acetone M, anisole, n-hexanol D, 4-methylthiazole, ethyl trans-2-hexenoate M, p-cymene M, terpinene M, isoamyl acetate M, methyl hexanoate M, methyl hexanoate D, isopropylidene acetone D, etc. gradually form after 4 days of fermentation. Heterofermentative lactic acid bacteria mainly carry out carbohydrate metabolism through the 6-phosphogluconic acid / phosphoketolase (6-PG / PK) pathway, converting sugars into volatile products such as lactic acid, ethanol, acetic acid and CO2.

[0029] Among them, acetic acid has a sour taste and fruity aroma, myrcene has an oily aroma, n-hexanol has floral and grassy aromas, and eucalyptol has herbal and camphor flavors, endowing fish pieces with unique flavors during the fermentation process. Moreover, aldehydes such as 4-hydroxy-4-methyl-2-pentanone M and isopropylidene acetone D can combine or condense with substances such as alcohols, methanethiol, and ammonia to produce aromas different from themselves, complicating the flavor of fermented fish sauce. When fermented to the 8th day, flavor substances such as ethyl hexanoate D, ethyl hexanoate M, 2,3-dimethylpyrazine, and tetrahydrothiophene begin to stand out. For example, pyrazine has strong aroma and volatility. Esters such as methyl hexanoate D, allyl isothiocyanate M, ethyl trans-2-hexenoate M, ethyl trans-2-hexenoate D, isoamyl acetate M, methyl hexanoate M, ethyl acetate D, ethyl acetate M, etc. and enones such as 4-hydroxy-4-methyl-2-pentanone-D, terpinene M, and isopropylidene acetone D have relatively high contents on the 30th day of fermentation. Most acids, alcohols, and aldehydes basically promote the formation of ester aroma substances through esterification reactions in the early and middle stages of fermentation, complicating the flavor of the final product of marinated fish pieces.

[0030] Gallery Plot analysis of the volatile components of fish pieces at different marinating stages is as Figure 3As shown. The Gallery Plot plugin based on the LAV software can intuitively and quantitatively compare the differences in volatile organic compounds between different samples according to the fingerprint spectrum comparison; for example Figure 3 As shown, the proportions of aroma substances in fish blocks at different marinating stages vary with the marinating stage, and the overall content of volatile organic compounds increases with the prolongation of marinating time.

[0031] The principal component analysis of fish blocks at different marinating stages is as Figure 4 shown.

[0032] PCA analysis (principal component analysis) was performed on 81 volatile components of fish blocks at different marinating stages, and a scatter plot was drawn through the principal component scores of different marinating stages. As Figure 3 can be seen, the discrimination of fish blocks at different marinating stages is relatively high, and it can be well distinguished between 0 day and 2 days, 4 days, 8 days and 12 days.

[0033] The present invention takes fish blocks at different marinating stages as raw materials, and analyzes the differences in aroma substances between fish blocks at different marinating stages based on HS-GC-IMS. It can be seen from the fingerprint spectrum, Gallery Plot diagram, and PCA analysis that HS-GC-IMS can accurately identify the marinating stages of fish blocks through the differences in characteristic components in the fingerprint spectrum, and establish a method for distinguishing fish blocks at different marinating stages based on aroma fingerprint information, providing a theoretical basis and data support for the big data screening of fish blocks at different marinating stages and the clarification of marinating stages.

[0034] Through the detailed introduction of an example of a method for quickly identifying the marinating stage and aroma differences of fish blocks based on GC-IMS above, it is found that there are obvious differences in the volatile flavor components of fish blocks at different marinating stages. Therefore, this method has good performance for quickly distinguishing different marinating stages of fish blocks, and has good effects on product control and quality evaluation.

[0035] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0036] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

Claims

1. A method for quickly identifying the marinating time and aroma differences of fish blocks based on GC-IMS, which is used to confirm the marinating stage of fish blocks, is characterized in that, The method includes the following steps: Step 1: Incubate fish meat samples at different marinating stages in a headspace vial to obtain incubated samples. Use a syringe needle to extract gas samples from the incubated samples. The extracted gas samples enter a gas chromatograph-ion mobility spectrometer through the syringe needle for determination to obtain analysis results. Based on the analysis results, generate volatile aroma components of fish blocks at different marinating stages through the supporting software and plug-ins, and establish a database of GC-IMS flavor fingerprint maps; Step 2: Detect the fish block sample to be measured under the same instrument conditions as in Step 1 to obtain the GC-IMS fingerprint map of the volatile aroma components of the fish block to be measured; Step 3: Confirm the marinating stage of the fish block by comparing and analyzing the fish block to be measured and the fish blocks at different marinating stages in the database.

2. The method for rapidly identifying the marinating time and aroma difference of fish blocks based on GC-IMS according to claim 1, characterized in that, During the process of extracting gas samples from the incubated samples, the mass of the fish meat sample is 2 - 5 g, the capacity of the headspace vial is 20 ml, the incubation temperature is 50 - 70 °C, the incubation time is 10 - 20 min, the volume of the extracted gas sample is 50 - 150 μL, and the temperature of the syringe needle is 80 - 90 °C.

3. The method for rapidly identifying the marinating time and aroma difference of fish blocks based on GC-IMS according to claim 1, wherein The process of the gas sample entering the gas chromatograph-ion mobility spectrometer through the syringe needle for determination specifically includes the following steps: The gas sample enters the gas chromatograph-ion mobility spectrometer through the syringe needle and passes through an MXT-WAX chromatographic column, and a carrier gas program is set for gradient separation to obtain the retention time; The gas sample enters the gas chromatograph-ion mobility spectrometer through the syringe needle and migrates through a drift tube to obtain the migration time; Qualitatively and quantitatively analyze the compounds based on the retention time and migration time to obtain the analysis results.

4. The method for rapidly identifying the pickling time and aroma difference of fish blocks based on GC-IMS according to claim 3, wherein, During the retention time obtained, the liquid film thickness of the stationary phase of the MXT-WAX column is 1 μm, and the radiation source of the MXT-WAX column is β rays (tritium, 3H). The ionization mode of the MXT-WAX column is positive ion, the carrier gas is N2, and the carrier gas program is as follows: 0 - 2 min: The carrier gas flow rate is 2 mL / min; 2 - 10 min: The carrier gas flow rate linearly increases from 2 mL / min to 10 mL / min; 10 - 20 min: The carrier gas flow rate linearly increases from 10 mL / min to 100 mL / min; 20 - 50 min: The carrier gas flow rate remains constant at 100 mL / min until the separation ends.

5. The method for rapidly identifying the marinating time and aroma difference of fish blocks based on GC-IMS according to claim 3, wherein, During the process of obtaining the migration time, the length of the drift tube is 98 mm, the linear voltage inside the drift tube is 500 V / cm, the temperature of the drift tube is 45 °C, the drift gas is N2, and the drift gas flow rate is 150 mL / min.

6. The method for rapidly identifying the pickling time and aroma difference of fish blocks based on GC-IMS according to claim 1, characterized in that, The supporting software and plug-ins include VOCal software and three plug-ins. The three plug-ins include the Reporter plug-in, the Gallery Plot plug-in, and the Dynamic PCA plug-in.

7. The method for quickly identifying the marinating time and aroma difference of fish blocks based on GC-IMS according to claim 1, characterized in that Confirming the marinating stage of the fish block includes at least one of the following three methods to confirm the marinating stage of the fish block; Among them, Method 1: Extract the GC-IMS fingerprint map of the fish block to be measured and compare and analyze it with the database of GC-IMS flavor fingerprint maps of fish meat samples at different marinating stages in the database to confirm the marinating stage of the fish block; Among them, Method 2: Extract the ion peak map in the GC-IMS fingerprint of the volatile aroma components of the fish block to be tested, and the ion peak map in the database of the GC-IMS flavor fingerprints of the fish meat samples at different marinating stages, and conduct comparative analysis by jointly plotting the GalleryPlot graph to confirm the marinating stage of the fish block; Among them, Method 3: Conduct principal component analysis on the relative contents of the volatile aroma substances in the GC-IMS fingerprint of the volatile aroma components of the fish block to be tested and the relative contents of the volatile aroma substances in the database of the GC-IMS flavor fingerprints of the fish meat samples at different marinating stages, and jointly plot a scatter diagram based on the principal component scores of the fish block for comparison to confirm the marinating stage of the fish block.

8. The method for rapidly identifying the marinating time and aroma difference of fish blocks based on GC-IMS according to claim 1, characterized in that The volatile aroma substances in Step 1 include at least one of the following categories: Terpinene, cis-3-hexenol, terpinolene, dipentene, beta-pinene, myrcene, 2-nonanone, isopropylidene acetone, 4-hydroxy-4-methyl-2-pentanone, ethanol, n-pentanol, n-butanol, n-propanol, isoamyl alcohol, n-hexanol, n-hexanal, trans-2-pentenal, n-heptanal, isopentenal, acetic acid, n-heptanoic acid, p-cymene, o-xylene, p-xylene, anisole, 4-methylthiazole, 2,3-dimethylpyrazine, eucalyptol, 2,5-dimethylpyrazine, tetrahydrothiophene, allyl isothiocyanate, methyl isovalerate, ethyl trans-2-hexenoate, hexyl acetate, ethyl acetate, isoamyl acetate, methyl hexanoate.

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