A method for constructing a characteristic map of volatile components in hops and a method for identifying hops

Abstract

The application relates to the technical field of volatile substance analysis, in particular to a construction method of a characteristic map of volatile components in hops and a method for identifying hops. The technical scheme of the application comprises the following steps: placing a hop sample in a sealed container, incubating at 80 DEG C, and obtaining volatile components in the hops; and performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the hops, wherein the gas chromatography conditions comprise: (1) the carrier gas is nitrogen; (2) the carrier gas flow rate is 0-2 min, 2 mL / min; 2-5 min, 2-15 mL / min; 5-25 min, 10-150 mL / min; 25-30 min, 100 mL / min; and the ion mobility spectrometry conditions comprise: (1) the drift gas is nitrogen; (2) the drift gas flow rate is 150 mL / min. The technical scheme of the application can efficiently, quickly and comprehensively obtain the chemical information of volatile components in hops, establish a characteristic map of the volatile components, and provide a basis for identifying the types and / or authenticity of hops.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of volatile substance analysis, in particular to a method for constructing a characteristic spectrum of volatile components in hops, and a method for identifying hops, and specifically relates to a method for constructing a characteristic spectrum of volatile components in hops based on gas chromatography-ion mobility spectrometry (GC-IMS) analysis, and a method for identifying adulteration and / or classification of hops based on the analysis. BACKGROUND

[0002] Humulus lupulus.L, also known as Humulus lupulus, Hupu, and yeast flower, is a perennial climbing herb. From the perspective of plant taxonomy, hops belong to the Humulus genus of the Cannabaceae family. In 2003, the APGII classification method classified the Humulus, Cannabaceae and Moraceae families into the Rosales order based on genetic relationships. Hops are dioecious, with female flowers in the form of pine cones and special lupulin glands. The lupulin secreted by the glands has a unique aroma and bitterness, which can impart a unique flavor to beer in beer brewing. Hops are known as the "soul of beer" and can also inhibit bacteria, prevent corrosion, and maintain the stability of beer foam.

[0003] For more than a century, the chemical composition of hops and its brewing effects have been extensively studied. However, the study of flavor components in hops is not systematic enough. Currently, the volatile flavor substances in hops are mainly studied using gas chromatography-mass spectrometry (GC-MS) technology. This technology requires heating the sample to be tested to above 230°C, which causes some heat-labile substances in hops to be destroyed, resulting in a deviation between the detected distribution of volatile substances in hops and the actual situation. In addition, GC-MS requires pretreatment of the sample to enrich the volatile components, which is complex, time-consuming, and greatly limits its application.

[0004] Gas chromatography-ion mobility spectrometry (GC-IMS) analysis is a rapid and reliable analysis method for trace volatile organic gases. It uses gas retention time and ion mobility drift time to identify selected compounds. Specifically, after the sample is injected, the components in the sample are sequentially carried into the ionization reaction zone by the carrier gas. Then, under the action of the ion source, the molecules undergo a series of ionization reactions and ion-molecule reactions with the carrier gas, forming molecular ions. Under the action of the electric field force, these ions enter the drift zone through the periodically opened ion gate, where they collide with the counter-flow neutral drift gas molecules, achieving secondary separation due to differences in molecular weight and molecular structure. Because the mass, charge, collision interface, and spatial configuration of the sample are different, their migration rates in the electric field are different, and the time of arrival at the detector is also different. The detector collects the ion signal and transmits it to the software to form a gas-phase ion mobility spectrum, and the content of flavor substances in the sample is obtained after analysis.

[0005] The GC-IMS analysis method has high sensitivity and has been widely used as a supplementary technical means for detecting food flavor substances. In addition, the GC-IMS system is easy to operate, does not require vacuum, has low requirements for the water content of the sample, has low consumable and post-maintenance costs, and has excellent application prospects.

[0006] Currently, there is no related report on the analysis of hops by using the gas chromatography-ion mobility spectrometry analysis method. SUMMARY

[0007] In view of the above problems, the technical scheme of the present application is proposed. One object of the present application is to provide a method for constructing a characteristic spectrum of volatile components in hops. The construction method is based on the gas chromatography-ion mobility spectrometry analysis method, and can qualitatively and / or quantitatively analyze the volatile components in hops. The method is simple to operate, has a short sample detection time, and does not require complex sample pretreatment. Another object of the present application is to provide a method for identifying the adulteration of hops. The identification method is based on the characteristic spectrum of volatile components in hops, and can effectively identify the adulteration of the hops to be tested by comparison. Another object of the present application is to provide a method for classifying and identifying hops. The method is based on the characteristic peak data obtained by the gas chromatography-ion mobility spectrometry analysis, and can classify different types of hops by including a multivariate statistical analysis method, thereby effectively identifying the type of the test substance.

[0008] Specifically, the method for constructing the characteristic spectrum comprises the following steps:

[0009] Incubating a hops sample to obtain volatile components therein;

[0010] Performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the hops sample to obtain a characteristic spectrum of volatile components in hops;

[0011] In the gas chromatography-ion mobility spectrometry analysis:

[0012] The conditions of the gas chromatography include the following technical features: (1) the carrier gas is nitrogen; (2) the carrier gas flow program includes: 0 min-2 min, the carrier gas flow is kept at 2 mL / min; 2 min-5 min, the carrier gas flow is increased from 2 mL / min to 15 mL / min; 5 min-25 min, the carrier gas flow is increased from 10 mL / min to 150 mL / min; 25 min-30 min, the carrier gas flow is kept at 100 mL / min;

[0013] The ion mobility spectrometry conditions include the following technical features: (1) the drift gas is nitrogen; (2) the drift gas flow rate is 120 mL / min to 180 mL / min.

[0014] The adulteration identification method includes the following steps:

[0015] The volatile components in the hops standard sample are obtained by incubation;

[0016] The volatile components in the hops standard sample are analyzed by gas chromatography-ion mobility spectrometry to obtain a characteristic spectrum of the volatile components in the hops standard sample;

[0017] The volatile components in the hops standard sample are obtained by incubation;

[0018] The volatile components in the hops standard sample are analyzed by gas chromatography-ion mobility spectrometry to obtain a characteristic spectrum of the volatile components in the hops standard sample;

[0019] The characteristic spectrum of the volatile components in the hops standard sample and the characteristic spectrum of the volatile components in the test sample are compared;

[0020] In the gas chromatography-ion mobility spectrometry analysis,

[0021] The gas chromatography conditions include the following technical features: (1) the carrier gas is nitrogen; (2) the carrier gas flow rate program includes: 0 min to 2 min, the carrier gas flow rate is maintained at 2 mL / min; 2 min to 5 min, the carrier gas flow rate is increased from 2 mL / min to 15 mL / min; 5 min to 25 min, the carrier gas flow rate is increased from 10 mL / min to 150 mL / min; 25 min to 30 min, the carrier gas flow rate is maintained at 100 mL / min;

[0022] The ion mobility spectrometry conditions include the following technical features: (1) the drift gas is nitrogen; (2) the drift gas flow rate is 120 mL / min to 180 mL / min.

[0023] The classification identification method includes the following steps:

[0024] At least two different types of hops standard samples are taken, respectively incubated, and the volatile components therein are obtained;

[0025] The volatile components in the different types of hops standard samples are analyzed by gas chromatography-ion mobility spectrometry, respectively, to obtain characteristic peak value data of the volatile compounds in each type of hops standard sample, and a classification identification model is established by analyzing the characteristic peak value data using a multivariate statistical analysis method;

[0026] The volatile components in the hops standard sample are obtained by incubation;

[0027] performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the to-be-tested substance to obtain characteristic peak data of volatile compounds in the to-be-tested substance, and performing analysis on the to-be-tested substance by using the classification identification model to determine the type of the to-be-tested substance;

[0028] In the gas chromatography-ion mobility spectrometry analysis,

[0029] The conditions of the gas chromatography include the following technical features: (1) the carrier gas is nitrogen; (2) the carrier gas flow program includes: 0 min-2 min, the carrier gas flow is kept at 2 mL / min; 2 min-5 min, the carrier gas flow is increased from 2 mL / min to 15 mL / min; 5 min-25 min, the carrier gas flow is increased from 10 mL / min to 150 mL / min; 25 min-30 min, the carrier gas flow is kept at 100 mL / min;

[0030] The conditions of the ion mobility spectrometry include the following technical features: (1) the drift gas is nitrogen; (2) the drift gas flow rate is 120 mL / min-180 mL / min.

[0031] The construction method of the characteristic spectrum of the present application is based on the gas chromatography-ion mobility chromatography analysis method, which is simple to operate and simple to process samples, does not require solid-phase extraction and other pretreatments for the samples, retains comprehensive sample characteristic information, is more accurate in analysis results, is more rapid and efficient in the analysis process, and is more intuitive in result expression, and has important significance for guaranteeing beer quality and promoting beer product upgrading.

[0032] The identification method of the present application is based on the chemical information of volatile components in hops obtained by the above-mentioned gas chromatography-ion mobility chromatography analysis method, and combines with chemometrics method for quantitative analysis, and can be used for rapidly distinguishing different varieties of hops and identifying the adulteration of hops. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 A comparison chart of the gas chromatography-ion mobility spectrum of the volatile components in the five kinds of hops in Example 1; Figure 1 A is a three-dimensional spectrum, and the coordinates X, Y and Z correspond to ion mobility time (minute), retention time (second) and peak intensity, respectively.Figure 1 Figure 6B is a two-dimensional spectrum plot of the volatile components in the five kinds of hops in Example 1, in which the horizontal axis represents ion mobility time (minute) and the vertical axis represents retention time (second);

[0035] Figure 2 Figure 7 is a comparison chart of the fingerprints of the volatile components in the five kinds of hops in Example 1;

[0036] Figure 3 Figure 8 is a principal component analysis of the volatile components in the five kinds of hops in Example 1; Figure 3 Figure 8A is a principal component score in Example 1, Figure 3 Figure 8B is a loading plot in Example 1;

[0037] Figure 4 Figure 9 is a partial least squares discriminant analysis chart of the volatile components in the five kinds of hops in Example 1; Figure 4 Figure 9A is a cross-validation plot in Example 1, Figure 4 Figure 9B is a score plot in Example 1, Figure 4 Figure 9C is a permutation test plot in Example 1;

[0038] Figure 5 Figure 10 is a variable projection importance analysis chart of the volatile components in the five kinds of hops in Example 1;

[0039] Figure 6 Figure 11 is a difference comparison chart of the volatile components in the five kinds of hops in Example 1;

[0040] Figure 7 Figure 12 is a comparison chart of the volatile components in the five kinds of hops in Example 1; Figure 7 Figure 12A is a three-dimensional spectrum plot of Qingdao Da Hua hops in China, Figure 7 Figure 12B is a three-dimensional spectrum plot of Saaz hops in Czech;

[0041] Figure 8 Figure 13 is a comparison chart of the volatile components in the five kinds of hops in Example 1; Figure 8 Figure 13A is a two-dimensional spectrum plot of Qingdao Da Hua hops in China, Figure 8 Figure 13B is a two-dimensional spectrum plot of Saaz hops in Czech;

[0042] Figure 9 Figure 14 is a comparison chart of the volatile components in the five kinds of hops in Example 1; Figure 9 Figure 14A is a two-dimensional spectrum plot of Qingdao Da Hua hops in China, Figure 9 Figure 14B is a two-dimensional spectrum plot of Saaz hops in Czech. DETAILED DESCRIPTION

[0043] The application will be further described below with reference to the accompanying drawings and examples. It should be understood that these examples are intended to illustrate the application and not to limit the scope of the application. Furthermore, it should be understood that various modifications can be made to the application by those skilled in the art upon reading the teachings of the present application as set forth herein. Such modifications are intended to fall within the scope of the appended claims.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0045] The term

[0046] Unless otherwise indicated, or unless the context clearly indicates otherwise, the terms or phrases used in this specification have the meanings as set forth below:

[0047] The term "and / or", as used in the context of this specification, should be interpreted as including any one of the items in the list, as well as any combination of the items in the list.

[0048] In this specification, the term "preferably" is used to mean that an embodiment or example is particularly suitable for some applications. This term is not used to limit the scope of the application.

[0049] In this specification, the terms "further", "more", "even more" and "particularly" are used to describe the difference in content, but should not be understood as limiting the scope of the application.

[0050] In this specification, the technical features described in an open-ended manner include both the closed technical solution consisting of the listed features, and the open technical solution containing the listed features.

[0051] In this specification, when referring to a numerical interval (i.e. a numerical range), unless otherwise specified, the optional numerical distribution within the numerical interval is considered to be continuous, and includes both numerical end points (i.e. the minimum value and the maximum value) of the numerical range, and every numerical value between the two numerical end points. Unless otherwise specified, when the numerical interval refers only to integers within the numerical interval, it includes both end point integers of the numerical range, and every integer between the two end point integers. Furthermore, when multiple ranges are provided to describe a feature or a characteristic, these ranges can be combined. In other words, unless otherwise indicated, the ranges disclosed herein are to be understood as including any and all sub-ranges subsumed therein.

[0052] The temperature parameters in the present application, if not particularly limited, allow for constant temperature treatment, and also allow for variation within a certain temperature range. It should be understood that the constant temperature treatment allows for fluctuations within the accuracy range controlled by the instrument. Fluctuations within a range such as ±0.5°C, ±0.4°C, ±0.3°C, ±0.2°C, ±0.1°C are allowed.

[0053] In the present application, the weight can be μg, mg, g, kg, and other mass units known in the chemical field.

[0054] An object of the present application is to provide a method for constructing a characteristic map of volatile components in hops, which is based on a gas chromatography-ion mobility analysis chromatography analysis method, simple to operate, short sample detection time, does not require complex sample pretreatment, can maximize the retention of flavor substances in hops, more accurately reflects the chemical information of volatile components therein, and provides a basis for the identification of the type and adulteration of hops.

[0055] In some embodiments, the method for constructing a characteristic map of volatile components in hops comprises the following steps:

[0056] S100: taking a hop sample for incubation and obtaining volatile components therein;

[0057] S200: performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the hop sample to obtain a characteristic map of volatile components in hops.

[0058] In some embodiments, in step S100, the hop sample is incubated in a sealed container to obtain headspace gas containing volatile components. Further, the mass-to-volume ratio of the hop sample in the sealed container is (0.8-1.2) g / 10 mL.

[0059] In step S100, incubation of the hop sample under suitable incubation conditions can allow the volatile components contained therein to diffuse fully, while not causing the components therein to deteriorate, so that more accurate analysis results can be obtained.

[0060] In some embodiments, the incubation temperature is 40-90°C. Further, it can be 70-90°C, for example, the incubation temperature can be 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, etc.

[0061] In some embodiments, the incubation time is 15-30 min. Further, it can be 15-20 min, for example, the incubation time can be 15 min, 18 min, 20 min, 22 min, 25 min, 28 min, 30 min, etc.

[0062] In some embodiments, the rotation speed of the incubation is 200 rpm to 600 rpm, further can be 400 rpm to 600 rpm, for example, the rotation speed is 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, etc.

[0063] In step S200, the volatile components in the hops are analyzed by gas chromatography-ion mobility spectrometry. This analysis method combines the high separation ability of gas chromatography (GC) and the high sensitivity of ion mobility spectrometry (IMS), and can more quickly and comprehensively analyze the chemical characteristics of the test substance.

[0064] In some embodiments, the instrument for gas chromatography-ion mobility spectrometry analysis is a flavor analyzer.

[0065] In some embodiments, the conditions of the gas chromatography include the following technical features: (1) the carrier gas is nitrogen; (2) the carrier gas flow program includes: 0 min to 2 min, the carrier gas flow is kept at 2 mL / min; 2 min to 5 min, the carrier gas flow is increased from 2 mL / min to 15 mL / min; 5 min to 25 min, the carrier gas flow is increased from 10 mL / min to 150 mL / min; 25 min to 30 min, the carrier gas flow is kept at 100 mL / min.

[0066] In some embodiments, the conditions of the gas chromatography include one or more of the following technical features: (1) the column temperature is 50°C to 70°C; (2) the injection volume is 100 μL to 300 μL; (3) the injection needle temperature is 80°C to 90°C; (4) the analysis time is 20 min to 40 min; (5) the type of chromatographic column is MXT-WAX; (6) the thickness of the stationary liquid film is 0.8 μm to 1.2 μm.

[0067] In some embodiments, the conditions of the gas chromatography include one or more of the following technical features: (1) the radioactive source is β-ray (tritium, 3H); (2) the ionization mode is positive ion.

[0068] In some embodiments, the conditions of the ion mobility spectrometry include the following technical features: (1) the drift gas is nitrogen; (2) the drift gas flow rate is 120 mL / min to 180 mL / min.

[0069] In some embodiments, the conditions of the ion mobility analysis include one or more of the following technical features: (1) the drift tube length is 95 mm to 100 mm; (2) the in-tube linear voltage is 400 V / cm to 600 V / cm; (3) the drift tube temperature is 40°C to 50°C.

[0070] In some embodiments, the characteristic pattern obtained by gas chromatography-ion mobility spectrometry analysis includes two-dimensional pattern, three-dimensional pattern and fingerprint pattern. Preferably, the characteristic pattern is analyzed by LAV (laboratory analytical viewer) software matched with GC-IMS, specifically including Reporter plug-in, Gallery Plot plug-in and Dynamic PCA plug-in.

[0071] Still another object of the present application is to provide a method for identifying adulteration of hops. The identification method of the present application is based on the characteristic pattern of volatile components in hops constructed by the present application. By comparing the characteristic pattern of volatile components in the test sample with the characteristic pattern of the standard sample, the quality of the test sample, adulteration and the like can be comprehensively identified, thereby providing a reference for comprehensive evaluation of the quality of hops.

[0072] In some embodiments, the method for identifying adulteration of hops comprises the following steps:

[0073] Incubating hops standard sample and obtaining volatile components therein;

[0074] Performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the hops standard sample to obtain a characteristic pattern of the volatile components in the hops standard sample;

[0075] Incubating the test sample and obtaining volatile components therein;

[0076] Performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the test sample to obtain a characteristic pattern of the volatile components in the test sample;

[0077] Comparing the characteristic pattern of the volatile components in the hops standard sample with the characteristic pattern of the volatile components in the test sample;

[0078] Preferably, the conditions for gas chromatography-ion mobility spectrometry analysis are the same as those in the method for constructing the characteristic pattern described above, which can comprehensively, efficiently and accurately obtain chemical information of volatile substances in the sample.

[0079] In some embodiments, the method for identifying adulteration of hops is selected from any of the following groups:

[0080] (1) comparing and analyzing the two-dimensional pattern of the test sample with the two-dimensional pattern of the hops standard sample in the database;

[0081] (2) comparing and analyzing the three-dimensional pattern of the test sample with the three-dimensional pattern of the hops standard sample in the database;

[0082] (3) comparing and analyzing the fingerprint pattern of the test sample with the fingerprint pattern of the hops standard sample in the database.

[0083] Yet another object of the present application is to provide a classification and identification method of hops, which is based on the characteristic peak data obtained by the gas chromatography-ion mobility spectrometry analysis of the present application, and can classify different types of hops by including a multivariate statistical analysis method, thereby effectively identifying the type of the test substance.

[0084] In some embodiments, the multivariate statistical analysis method includes at least one of principal component analysis and partial least squares discriminant analysis.

[0085] In some embodiments, the multivariate statistical analysis includes principal component analysis, partial least squares discriminant analysis. Further, it also includes partial least squares discriminant analysis.

[0086] Preferably, the multivariate statistical analysis is performed using the MetaboAnalyst 5.0 website.

[0087] In some embodiments, the classification and identification method of hops includes the following steps:

[0088] Taking at least two different types of hop standard samples, respectively incubating and obtaining the volatile components therein;

[0089] Performing gas chromatography-ion mobility spectrometry analysis on the volatile components in different types of hop standard samples, respectively, to obtain characteristic peak value data of volatile compounds in each type of hop standard sample, using a multivariate statistical analysis method to analyze the characteristic peak value data, and establishing a classification and identification model;

[0090] Taking the test substance for incubation and obtaining the volatile components therein;

[0091] Performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the test substance, obtaining characteristic peak value data of volatile compounds in the test substance, and substituting into the classification and identification model for analysis to determine the type of the test substance;

[0092] Preferably, the conditions of gas chromatography-ion mobility spectrometry analysis are the same as those in the above-mentioned method for constructing the characteristic spectrum, which can comprehensively, efficiently and accurately obtain the chemical information of volatile substances in the sample.

[0093] In some embodiments, the hop standard sample is selected from one or more of the following varieties: Chinese Qingdao Da Hua, German Magnum, American Barley West, Czech Saaz, and German Hersbruck.

[0094] The following is a specific description of the gas chromatography-ion mobility spectrometry analysis method in the present application.

[0095] It is understandable that the feature map construction method, adulteration and / or classification identification method of the present application are all based on the gas chromatography-ion mobility spectrometry analysis method of the present application, therefore, it is necessary to briefly describe the specific analysis steps, but the following description is exemplary.

[0096] In some embodiments, the gas chromatography-ion mobility spectrometry analysis includes collecting characteristic peak data of each component in the volatile component, and combining the database to qualitatively and / or quantitatively analyze the volatile component, wherein the characteristic peak data includes but is not limited to retention time, migration time and peak volume.

[0097] The qualitative analysis of gas chromatography-ion mobility spectrometry analysis generally uses n-ketones C4-C9 as external standard.

[0098] The n-ketones C4-C9 in the present application refers to one or a combination of several ketone compounds with carbon atom number of 4-9, as an example, it can be selected from 2-butanone, 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone and 2-nonanone, further, the purity of the ketone compounds is analytical pure.

[0099] In some embodiments, the database at least includes the NIST database and the IMS database built in GCxIMS Library Search.

[0100] In some embodiments, after analysis, the volatile components in hops are selected from one or more of the following: 2-pentanone, 4-methyl-2-pentanone, 2-propanone, ethyl acetate, propyl aldehyde, butyl aldehyde, 2-methyl propyl aldehyde, alpha-pinene, ethyl acrylate, tert-butyl alcohol, methyl propyl aldehyde, propyl propionate, delta-3-carene and 2-hexene acid ethyl ester.

[0101] In some embodiments, after analysis, hops contain 83 volatile components, each component is specifically attributed as follows:

[0102]

[0103]

[0104]

[0105]

[0106] The quantitative analysis of gas chromatography-ion mobility spectrometry analysis is to use the peak volume of each component in the feature map to represent its relative content.

[0107] The following are some specific examples.

[0108] The materials and equipment used in the following examples are as follows:

[0109] Materials:

[0110] 90 type hop pellets samples include Qingdao Da Hua from China, Magnum from Germany, Bells from USA, Saaz from Czech, Hülsbrücke from Germany;

[0111] Equipment: Flavor analyzer; precision balance; hop crusher.

[0112] For the experimental parameters not written in the following specific examples, refer to the guidance given in this application document first, and also refer to the experimental manual in the art or other experimental methods known in the art, or refer to the recommended experimental conditions of the manufacturer.

[0113] For the raw materials and reagents not written in the following specific examples, they can be obtained by market, or can be prepared by known means by those skilled in the art.

[0114] Example 1

[0115] 1. Qualitative and quantitative analysis of five types of hops

[0116] Take the samples of Qingdao Da Hua from China, Magnum from Germany, Bells from USA, Saaz from Czech, Hülsbrücke from Germany for GC-IMS determination and process by three plug-ins (Reporter plug-in, Gallery Plot plug-in, Dynamic PCA plug-in), and perform qualitative and quantitative analysis on the sample data. The specific determination conditions are as follows:

[0117] 1.1. Sample processing

[0118] Weigh 2g of sample powder into a 20mL headspace bottle, incubate at 500rpm, and then inject after incubation at 80℃ for 15min;

[0119] 1.2. Conditions for GC-IMS analysis

[0120] GC: headspace injection 200μL, carrier gas N2, column temperature 60℃, injection needle temperature 85℃, analysis time 30min, chromatographic column MXT-WAX (30m, ID: 0.53mm), stationary liquid film thickness: 1μm, carrier gas flow rate 0-2min, 2mL / min; 2-5min, 2-15mL / min; 5-25min, 10-150mL / min; 25-30min, 100mL / min;

[0121] IMS: drift tube length: 98mm; linear voltage inside the tube: 500V / cm; drift tube temperature: 45℃; drift gas N2; drift gas flow rate: 150mL / min

[0122] The GC-IMS qualitative analysis is performed by comparing the retention time and migration time of the normal ketones C4-C9 as external standards with the NIST database and IMS database in the GCxIMS Library Search, so as to obtain the retention index of the volatile components and perform the qualitative analysis.

[0123] The GC-IMS quantitative analysis is performed by taking the volume peak of the three-dimensional spectrum as the relative content.

[0124] 2. Principal component analysis, partial least squares discriminant analysis and variable importance projection analysis

[0125] The qualitative and quantitative data of the five kinds of hops are subjected to principal component analysis, partial least squares discriminant analysis and variable importance projection analysis by using the MetaboAnalyst 5.0 website, and the analysis results are used to compare the differences between different varieties of hops.

[0126] 3. Construction of characteristic spectrum

[0127] Obtaining the characteristic spectrum of the control: based on the data obtained by GC-IMS analysis, the two-dimensional spectrum, three-dimensional spectrum and fingerprint spectrum are obtained by using the GC-IMS plug-in;

[0128] Obtaining the characteristic spectrum of the test substance: the same instrument conditions as in step 1 are used to detect the test adulterated hop sample, and the corresponding two-dimensional spectrum, three-dimensional spectrum and fingerprint spectrum are obtained by using the plug-in;

[0129] Comparing the characteristic spectrum of the control with the characteristic spectrum of the test substance.

[0130] 4. Results and analysis

[0131] Figure 1 The three-dimensional comparison chart and two-dimensional comparison chart of the volatile components of different varieties of hops by gas chromatography-ion mobility chromatography. Figure 1 A is a three-dimensional chart, in which the Y axis is the retention time, the X axis is the migration time, the Z axis is the signal peak value intensity, the vertical line at the horizontal coordinate 8.0 is the reaction ion peak (RIP peak), each signal point on both sides of the RIP peak represents a volatile component, the color represents the concentration of the substance, white represents small concentration, red represents large concentration, and the deeper the color, the larger the concentration; along the X axis from left to right are the three-dimensional charts of Qingdao Dahua in China, Magnusen in Germany, Barbary in the United States, Saaz in the Czech Republic and Hülsbrook in Germany, respectively. It can be seen that the peak degrees of the three-dimensional charts of different varieties of hops are quite different, indicating that the volatile components of different varieties of hops are quite different.

[0132] Figure 1Figure B is a two-dimensional top view obtained by projecting a three-dimensional image. The volatile components in each sample are mainly located in the marked area in the figure, and it can be found that there are significant differences between different varieties of hops standards.

[0133] Figure 2 Fingerprint spectra of volatile components of different hop varieties as standards, based on Figure 2 It can be observed that hops are rich in volatile components. Figure 2 The information at point (e) indicates that the contents of substances such as 2-pentanone, 4-methyl-2-pentanone, 2-propanone, ethyl acetate, propionaldehyde, butyraldehyde, 2-methylpropionaldehyde, α-pinene, ethyl acrylate, tert-butanol, methacrolein, propyl propionate, δ-3-carene, and ethyl 2-hexenoate are all relatively high in the five types of hops, indicating that there are certain commonalities among different hop products.

[0134] American basil hops contribute rich aromas to beer, including spicy, citrus, and fruity notes. Figure 2 As can be seen, the volatile components of American basil are the most abundant. Figure 2 As can be seen in section (a), propylene glycol, hexanol, 2,3-butanediol, ethyl octanoate, isobutyl butyrate, hex-2-en-1-yl acetate, and hexyl butyrate are the dominant volatile components of Balasis in the United States.

[0135] Magnum hops, originating in Germany, are a high-acidity, bittersweet variety that has received consistent praise from brewers abroad. Figure 2 As can be seen in (f), α-thujone and the other 5 unidentified compounds are volatile components unique to Magnumen. These components are present in extremely small amounts in the remaining hops and can be used as marker components of Magnumen.

[0136] Figure 2 In section (b), it can also be seen that the German Magnum hops and the American Balestier hops have high contents of compounds such as isobutyl acetate, (Z)-3-hexenylvalerate, hexyl propionate-D, 3-methylbutyl-2-methylbutyrate-D isopentyl isopentyl ester, and 2-octanone-D, indicating that the German Magnum hops and the American Balestier hops have a high degree of similarity.

[0137] Czech Saaz hops have a balanced composition of various oils and are rich in polyphenols, while German Hersbruck hops are low in alpha-acids and humulene. Both are aroma-type hops with similar volatile components. Figure 2 As can be seen from section (d), 1-penten-3-ol, 3-methyl-2-pentanone, 3-methyl-2-butenal, 3-pentanone, pentanal, and 1-penten-3-one are present in greater quantities in Sáz and Hersbruck, Czech Republic, while other hops are present in smaller quantities.

[0138] Qingdao hops from China are the most widely used bitter hops in domestic hop production. Figure 2 As can be seen in section (c), compounds such as 1-octen-3-ol and 3-isobutyl-2-methoxypyrazine are volatile components unique to Qingdao hops in China. These components are present in extremely small amounts in other hops and can be used as marker components of Qingdao hops in China.

[0139] Figure 3 Principal component analysis diagrams of volatile components in standard samples of different hop varieties. Figure 3 In sample A, principal component 1 (PC1) represents 58.3% of the variance, and principal component 2 (PC2) represents 20.8% of the variance. The total variance contribution (TVE) of the two principal components is 79.1%. Figure 3 As can be seen from Figure A, in the PC1 direction, the American guava and the German magnum are close to each other, indicating that they are highly similar; the Czech Saz and Helsbrook are also close to each other, indicating that they are relatively similar. In the PC2 direction, the Chinese Qingdao dahua is at the lower end of the y-axis, while the German magnum, the American guava, the Czech Saz, and the German Helsbrook are all at the upper end of the y-axis, indicating that the domestic varieties and imported varieties are highly dispersed, and different imported varieties show good clustering. Figure 3 Figure B indicates that, in the PC1 direction, compounds such as 6-methyl-hept-5-en-2-one, 3-pentanone, 1-octen-3-ol, 2-methyl-2-butenal, propyl propionate, 2-heptenal, and pentanal contribute significantly, while in the PC2 direction, compounds such as hexyl butyrate, 1,2-propanediol, butyric acid, 3-hydroxy-2-butanone, and 3-isobutyl-2-methoxypyrazine contribute significantly.

[0140] Partial least squares discriminant analysis of volatile components in different hop varieties, as follows: Figure 4 As shown. Figure 4 As shown, this study established PLS-DA models for five hop species, and obtained model evaluation parameters through cross-validation, including R... 2 =0.96137, Q 2 =0.91433, both values ​​are close to 1 ( Figure 4 A) indicates that the model's predictive ability is feasible. For example... Figure 4 As shown in Figure B, the PLS-DA analysis demonstrated a significant effect in distinguishing the sample groups. To prevent overfitting, a 100-order test was used to examine the model quality, and the results are as follows. Figure 4 In C, we can see that p < 0.01, indicating that the model did not exhibit overfitting.

[0141] Variable projection importance analysis of volatile components in different hop varieties, as follows: Figure 5 As shown. Figure 5As shown in FIG. A, there are 20 metabolites in the PLS-DA model with VIP > 1, including 8 esters, 3 acids, 2 aldehydes, 2 ketones, 2 pyrazines, 2 alkenes, 1 alcohol. The right spectrum represents the concentration of different volatile organic compounds. Red represents high concentration of the substance, the darker the color, the higher the concentration, and blue is the opposite.

[0142] The difference map of the two-dimensional spectrum of volatile components in different varieties of hops is as shown in Figure 6 , in which the United States Barbexi is taken as a reference, and the spectrum of other samples is deducted from the reference. The red area indicates that the sample component has a higher concentration than the reference sample component. The darker the color, the higher the concentration, and the blue area is the opposite. If the concentrations of two volatile components are consistent, the background after deduction is white. From Figure 6 it can be seen that compared with the United States Barbexi, the other hops have more blue, indicating that the United States Barbexi has the most volatile components; the white part of the German Magnusmen is the most compared with the United States Barbexi, indicating that the two are highly similar; the Czech Saaz and German Hesbrouck have darker blue parts compared with the United States Barbexi, but there are also many red parts, indicating that the two have large differences in volatile components with the United States Barbexi and contain their own marker components.

[0143] The three-dimensional map of volatile aroma components of the standard sample and the adulterated sample of Chinese Qingdao Dahua and Czech Saaz hops is as shown in Figure 7 , in which Figure 7 the difference between the adulterated sample and the standard sample has been marked. The standard sample and its adulterated sample can be seen to have a large difference in volatile aroma components, indicating that this method is feasible for identifying hop adulteration.

[0144] The two-dimensional spectrum of volatile aroma components of the standard sample and the adulterated sample of Chinese Qingdao Dahua and Czech Saaz hops is as shown in Figure 8 , in which Figure 8 the difference between the adulterated sample and the standard sample has been marked. The standard sample and its adulterated sample can be seen to have a large difference in volatile aroma components, indicating that this method is feasible for identifying hop adulteration.

[0145] The difference map of the two-dimensional spectrum of volatile aroma components of the standard sample and the adulterated sample of Chinese Qingdao Dahua and Czech Saaz hops is as shown in Figure 9 , in which the standard sample is taken as a reference, and the spectrum of the adulterated sample is deducted from the reference. In Figure 9 , the difference between the adulterated sample and the standard sample has been marked. The standard sample and its adulterated sample can be seen to have a large difference in volatile aroma components, indicating that this method is feasible for identifying hop adulteration.

[0146] The application takes different varieties of hops as raw materials, and analyzes the differences in aroma substances between different types of hops based on GC-IMS. From the fingerprint spectrum, two-dimensional spectrum, three-dimensional spectrum, principal component analysis, partial least squares discriminant analysis and the like, it can be seen that the GC-IMS (gas chromatography-ion mobility spectrometry) can accurately distinguish different varieties of hops through the differences in characteristic components in the fingerprint spectrum, and establish a difference discrimination method for different varieties of hops based on aroma fingerprint information. It can also identify whether it is adulterated, and provide theoretical basis and data support for the big data identification of different types of hops and the research and development of new beer products.

[0147] The above examples introduce in detail the construction method of the characteristic spectrum of volatile components in hops and the identification method of hops. The results of the examples show that the volatile flavor components of different types of hops have obvious differences, and the adulteration can be effectively identified. Therefore, this method has good performance for quickly distinguishing different types of hops, and has good effect on product control and quality evaluation.

[0148] All the documents mentioned in the present application are incorporated by reference in the present application, as if each document is individually incorporated by reference. Unless and to the extent that the documents cited in the present application conflict with the purpose and / or technical solutions of the present application, the documents cited in the present application are incorporated by reference in their entirety. When the present application refers to the cited documents, the definitions of the related technical features, terms, nouns, phrases and the like in the cited documents are also incorporated by reference. When the present application refers to the cited documents, the examples and preferred modes of the related technical features cited are also incorporated by reference into the present application, but are limited to the implementation of the present application. It should be understood that when the cited content conflicts with the description in the present application, the present application is used as the reference or is modified according to the description in the present application.

[0149] The technical features of the above-described embodiments and examples can be combined in any suitable manner. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments and examples are described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered within the scope of the present description.

[0150] The above embodiments only express several implementation ways of the present application, but cannot be understood as limitation to the patent scope. It should be pointed out that, for ordinary skilled in the art, several variations and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. In addition, it should be understood that, after reading the above teaching of the present application, the skilled in the art can make various changes or modifications to the present application, and the equivalent forms also fall within the protection scope of the present application. It should also be understood that, the skilled in the art can obtain the technical solutions on the basis of the technical solutions provided by the present application through logical analysis, reasoning or limited test, which all fall within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A method for constructing a profile of volatile components in hops, characterized by, The method comprises the following steps: incubating a hops sample to obtain volatile components in the hops sample; the hops sample is a Chinese Qingdao Da Hua, German Magnum, American Berrwick, Czech Saaz or German Hersbruck hops sample; the temperature of the incubation is 40-90℃, and the time is 15-30 minutes; performing gas chromatography-ion mobility spectrometry analysis on the volatile components in the hops sample to obtain a characteristic spectrum of the volatile components in the hops sample; the volatile components in each of the hops samples include 2-pentanone, 4-methyl-2-pentanone, 2-propanone, ethyl acetate, propyl aldehyde, butyl aldehyde, 2-methyl propyl aldehyde, alpha-pinene, ethyl propenoate, tertiary butyl alcohol, methyl propyl aldehyde, propyl propionate, delta-3-carene and ethyl 2-hexenoate; the volatile components in the Chinese Qingdao Da Hua hops sample further include 1-octene-3-alcohol and 3-isobutyl-2-methoxypyrazine; the volatile components in the American Berrwick hops sample further include propylene glycol, hexyl alcohol, 2,3-butanediol, ethyl octanoate, isobutyl butyrate, hex-2-en-1-yl acetate and hexyl butyrate; the volatile components in the German Magnum hops sample further include alpha-thujaene; the volatile components in the German Magnum and American Berrwick hops samples further include isobutyl acetate, (Z)-3-hexenyl valerate, hexyl propionate-D, 3-methylbutyl-2-methylbutyrate-D, isoamyl isovalerate and 2-octanone-D; the volatile components in the Czech Saaz and German Hersbruck hops samples further include 1-penten-3-alcohol, 3-methyl-2-pentanone, 3-methyl-2-butenal, 3-pentanone, pentyl aldehyde and 1-penten-3-one; In the gas chromatography-ion mobility spectrometry analysis: the conditions of the gas chromatography include the following technical features: (1) the carrier gas is nitrogen; (2) the carrier gas flow program includes: 0-2 min, the carrier gas flow is kept at 2 mL / min; 2-5 min, the carrier gas flow is increased from 2 mL / min to 15 mL / min; 5-25 min, the carrier gas flow is increased from 10 mL / min to 150 mL / min; 25-30 min, the carrier gas flow is kept at 100 mL / min; (3) the column temperature is 50-70℃; (4) the type of the chromatographic column is MXT-WAX; the conditions of the ion mobility spectrometry include the following technical features: (1) the drift gas is nitrogen; (2) the drift gas flow rate is 120-180 mL / min.

2. The method of constructing a feature map according to claim 1, wherein, The conditions of the gas analysis include one or more of the following technical features: (1) the injection volume is 100-300 μL; (2) the injection needle temperature is 80-90℃; (3) the fixed liquid-liquid film thickness is 0.8-1.2 μm.

3. The method of claim 1, wherein the feature map is constructed by: The conditions of the ion mobility analysis include one or more of the following technical features: (1) the drift tube length is 95-100 mm; (2) the tube internal linear voltage is 400-600 V / cm; (3) the drift tube temperature is 40-50℃.

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