Detection method for improving detection of terpene substances in yeast for making hard liquor

Abstract

The invention provides a detection method for improving detection of terpene substances in yeast for making hard liquor, and relates to the field of flavor analysis of fermented food. The method comprises the following steps: 1) performing crushing pretreatment on a target yeast block to obtain yeast powder; 2) taking absolute ethyl alcohol as a solvent, performing water bath rotary evaporation on the yeast powder at 40-60 DEG C, filtering after rotary evaporation, retaining solid-phase yeast powder, and performing vacuum drying to obtain a dried yeast powder sample; (3) collecting a gas-phase sample with stable components volatilized from the yeast powder sample under the conditions of water bath heating and nitrogen purging; (4) pre-concentrating the gas-phase sample by adopting a multi-stage cold trap principle, wherein the enrichment multiple of the gas-phase sample is not less than 1000 in the pre-concentration; 5) collecting the pre-concentrated gas phase sample, inputting the pre-concentrated gas phase sample into a gas chromatograph-mass spectrometer for gas chromatography-mass spectrometry, and determining the terpene substances in the yeast for making hard liquor through standard gas matching. Compared with the prior art, the method has the advantages that 12 terpene substances can be simply and efficiently detected at a time, and the detection rate of the terpene substances is remarkably increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fermented food flavor analysis, and particularly relates to a detection method for improving detection of terpene substances in Daqu. BACKGROUND

[0002] The liquor-making industry is an important pillar of the light industry and food industry, and is a traditional and advantageous food in China. Daqu, as a traditional saccharifying and fermenting agent for liquor, is an important source of typical aroma characteristics of liquor, contains rich microbial flora, enzyme systems and complex flavor substances, and plays a decisive role in the style and quality of liquor. Rapid and comprehensive evaluation of the flavor of Daqu and its material basis and change rule has important significance for studying the aroma of liquor and improving the quality of base liquor.

[0003] Terpene substances, as important flavor substances in Daqu, mainly play the roles of flavor contribution, microbial metabolism regulation and enzyme activity regulation. Terpenes are important sources of complex aromas such as floral and fruity aromas in liquor, such as β-myrcene and limonene, which are converted into flavor substances in the liquor body through fermentation and distillation. Terpenes with different structures, such as monoterpenes and sesquiterpenes, have significant differences in flavor contribution, such as α-pinene and β-pinene, which impart fresh pine wood aroma, while linalool has floral and sweet aroma. Secondly, it has been reported that terpene substances have antibacterial or pro-bacterial effects, and can be used as metabolic intermediates or signal molecules of microorganisms such as molds and yeasts, to affect the growth and metabolic activity of microorganisms in Daqu, indirectly regulate the activity of enzymes such as amylase and esterifying enzyme, and further regulate the generation of flavor substances.

[0004] The detection of terpenes in Daqu (a type of Chinese liquor) typically faces four main challenges: First, the matrix is ​​complex, with numerous interfering components such as proteins and polysaccharides requiring efficient separation. Second, trace amounts are present, with terpenes present at low concentrations (μg / kg), necessitating highly sensitive instruments. Third, isomer differentiation is challenging, as terpene isomers, such as α-pinene and β-pinene, exhibit similar mass spectra, requiring optimized chromatographic conditions. Fourth, pretreatment losses are significant, as some terpenes, like monoterpenes, are prone to volatilization or degradation during extraction. Currently, techniques for detecting terpenes include gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), electronic noses, and sensor technologies. Sample processing methods primarily include headspace solid-phase microextraction (HS-SPME), solvent extraction, and supercritical fluid extraction (SFE), each with its own distinct advantages and disadvantages. For example, headspace solid-phase microextraction-GC-MS adsorbs volatile components through a fiber head and combines this with GC-MS analysis. Its advantages include the absence of organic solvents, making it suitable for trace terpene detection. Disadvantages include the potential for the selectivity of the fiber coating to affect recovery rates, and susceptibility to matrix interference at high temperatures. Solvent extraction, such as using ether or dichloromethane to extract terpenes from Daqu (a type of Chinese liquor), followed by concentration and analysis, offers high sensitivity and the ability to simultaneously detect multiple terpenes. However, it requires complex pretreatment and suffers from significant sample loss. Supercritical fluid extraction (SFE) uses supercritical CO2 as the extractant, leveraging its high diffusivity and solubility to extract terpenes. Its advantages include low-temperature operation, avoiding degradation of heat-sensitive substances, and environmental friendliness with no solvent residue. However, it suffers from high equipment costs and strict requirements for operating conditions, including pressure and temperature.

[0005] Therefore, it is of great significance to optimize the detection method, integrate existing instrumental analysis methods and sample processing methods, and develop a detection method suitable for terpenoids in Daqu (a type of Chinese liquor). Summary of the Invention

[0006] The purpose of this invention is to provide a detection method for improving the detection of terpenes in Daqu (a type of Chinese liquor). On the one hand, the method removes components that easily interfere with detection by pre-treating the sample. On the other hand, the method allows the volatile components in the sample to fully volatilize and be enriched for detection under water bath heating and nitrogen purging conditions. Compared with the existing technology, this method greatly improves the detection rate of terpenes, and the detection process is simple and efficient.

[0007] To achieve the above objectives, the present invention proposes the following technical solution: A detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) includes the following steps: 1) The target koji block is pre-treated by crushing to obtain koji powder; 2) Using anhydrous ethanol as a solvent, the koji powder was subjected to rotary evaporation in a water bath at 40-60℃. After rotary evaporation, the solid koji powder was filtered and vacuum dried to obtain the dried koji powder sample. 3) Collect stable gaseous samples of the volatile components from the koji powder sample under water bath heating and nitrogen purging conditions; 4) The gas phase sample is pre-concentrated using the principle of a multi-stage cold trap, wherein the pre-concentration results in an enrichment factor of not less than 1000 for the gas phase sample. 5) Collect the pre-concentrated gas phase sample and input it into a gas chromatography-mass spectrometry system for gas chromatography-mass spectrometry analysis. Determine the terpenoids in Daqu by standard gas matching.

[0008] Furthermore, in step 4), the gas phase sample is pre-concentrated using the three-stage cold trap principle. The operating parameters of the three-stage cold trap principle are as follows: cooling temperature of the first-stage cold trap is -20℃ and desorption temperature is 45℃; cooling temperature of the second-stage cold trap is -55℃ and desorption temperature is 230℃; focusing temperature of the third-stage cold trap is -165℃ and desorption injection pulse temperature is 250℃.

[0009] Furthermore, in step 5), the operating parameters of the gas chromatography-mass spectrometry system are as follows: injection volume 300~1200mL; splitless; column: DB-WAX elastic quartz fiber capillary column 60m x 0.25mm, 0.25μm; temperature program: 40℃ for 5min, increase to 150℃ at a rate of 5℃ / min, hold for 5min, increase to 210℃ at a rate of 8℃ / min, hold for 8min; carrier gas: He, flow rate 1.0mL / min; detector temperature: 250℃, inlet temperature: 250℃.

[0010] Furthermore, in step 5), the operating parameters of the mass spectrometer in the gas chromatography-mass spectrometry system are as follows: EI ionization source, electron energy of 70 eV, electron multiplier voltage of 1610 V, ion source temperature of 200 °C, transfer line temperature of 250 °C, and mass scan range a / z of 35-500 amu.

[0011] Furthermore, in step 3), the temperature of the water bath heating of the koji powder sample is 40-60℃.

[0012] Furthermore, in step 3), the flow rate of nitrogen purging the koji powder sample is 50~100mL / min, and the gas pressure is 0.05~0.2MPa.

[0013] Furthermore, it also includes: After pre-concentration, the gaseous sample is injected into the gas chromatograph-mass spectrometer and then split. One stream of the gaseous sample is injected into the mass spectrometer, and the other stream flows to the olfaction port of the olfaction meter.

[0014] Furthermore, the detection method detected 12 terpenoids, including pinene, camphene, β-pinene, γ-terpinene, (-)-limonene, β-phellandrene, geraniolene, p-menth-1,3,8-triene, α-shogaene, (+)-1,7-diepio-α-cedrene, (+)-monoene, and (Z,E)-α-farnesene.

[0015] Furthermore, the conditions for vacuum drying of the solid-phase powder in step 2) are: drying under vacuum conditions at an ambient temperature of 70°C for 2-5 hours.

[0016] Furthermore, the particle size of the koji powder obtained by pulverizing in step 1) is such that it passes through a sieve with a mesh size of 40-100.

[0017] As can be seen from the above technical solutions, the technical solutions of the present invention have achieved the following beneficial effects: This invention discloses a method for improving the detection of terpenes in Daqu (a type of starter culture). The method includes: 1) pre-treating the target Daqu block by crushing to obtain Daqu powder; 2) using anhydrous ethanol as a solvent, performing rotary evaporation of the Daqu powder in a water bath at 40-60℃, filtering after evaporation, retaining the solid phase Daqu powder, and vacuum drying to obtain a dried Daqu powder sample; 3) collecting a stable gas phase sample of the volatilized components of the Daqu powder sample under water bath heating and nitrogen purging conditions; 4) pre-concentrating the gas phase sample using a multi-stage cold trap principle, wherein the pre-concentration enrichment factor of the gas phase sample is not less than 1000; 5) collecting the pre-concentrated gas phase sample and inputting it into a gas chromatography-mass spectrometry (GC-MS) instrument for GC-MS analysis, and determining the terpenes in Daqu through standard gas matching. Compared with the prior art, this invention can simply and efficiently detect 12 kinds of terpenes in one step, significantly improving the detection rate of terpenes.

[0018] Specifically, this invention removes high-concentration interfering substances, mainly low-boiling-point and high-concentration substances such as ethyl acetate, from the sample pretreatment, reducing the occurrence of interfering peaks when analyzing terpenes using gas chromatography-mass spectrometry. Furthermore, by allowing the sample to fully volatilize under water bath heating and nitrogen purging conditions, this invention utilizes a multi-stage cold trap principle to concentrate and enrich terpenes from the volatilized substances, enabling the detection of trace amounts of terpenes and significantly improving the detection rate and accuracy of terpenes.

[0019] Furthermore, this invention achieves the detection of various terpenoids in Daqu (a type of Chinese liquor) by combining water bath rotary evaporation with water bath purging followed by concentration and enrichment. Compared with existing technologies, the sample processing process is simple to operate, produces less pollution, and has high processing efficiency and high detection accuracy.

[0020] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other.

[0021] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0022] The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a flowchart of the detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to the present invention; Figure 2 This is a chromatogram of terpenoids detected in Example 1 of the present invention; Figure 3 This is a comparison chart of the types of terpenoids detected in Example 1 and Comparative Example 1 of the present invention; Figure 4 This is a comparison diagram of the peak area of ​​pinene detected in Example 1 and Comparative Example 1 of the present invention; Figure 5 This is a comparison diagram of the peak areas of (-)-limonene detected in Example 1 and Comparative Example 1 of the present invention; Figure 6 This is a comparison diagram of the peak area of ​​β-phellandrene detected in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0024] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" mean that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0025] Terpenes play a role in Daqu (a type of starter culture) by contributing to flavor, regulating microbial metabolism, and modulating enzyme activity. Analyzing the composition of terpenes in Daqu is of great significance for understanding its flavor. Although existing methods for analyzing terpenes can analyze most types, each method has its limitations. For example, the selectivity of the fiber coating in headspace solid-phase microextraction affects the recovery rate, solvent extraction involves complex pretreatment, and supercritical fluid extraction has high equipment costs. Therefore, there is a need to develop a simple, low-cost, and high-detection-rate method suitable for the detection of terpenes in Daqu.

[0026] The present invention discloses a detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor), such as... Figure 1 As shown, it includes the following steps: Step S102: The target koji block is pre-treated by crushing to obtain koji powder; in actual operation, the target koji block is crushed into powder and then passed through a 40-100 mesh sieve to obtain koji powder. Step S104: Using anhydrous ethanol as a solvent, the koji powder is subjected to rotary evaporation in a water bath at 40-60℃. After rotary evaporation, the solid koji powder is filtered and vacuum dried to obtain the dried koji powder sample. Typically, 500g of koji powder is placed in a flask with 1L of anhydrous ethanol and distilled under reduced pressure in a water bath at 50℃. After impurity removal, the sample in the flask is separated into solid and liquid phases, retaining the solid koji powder sample. The solid koji powder sample is then vacuum dried to remove ethanol, specifically under vacuum conditions at an ambient temperature of 70℃ for 2-5 hours, usually about 4 hours.

[0027] Step S106: Collect stable gaseous samples of volatile components from the koji powder sample under water bath heating and nitrogen purging conditions. The specific steps for water bath heating and nitrogen purging of the koji powder sample are as follows: After impurity removal, the koji powder sample is placed in a wide-mouth bottle. A 40-60℃ water bath is used to heat the koji powder sample in the wide-mouth bottle to 40-60℃. A gas outlet is connected to the outlet of the nitrogen cylinder. The outlet end of the gas outlet passes through the stopper of the wide-mouth bottle and extends into the bottle. Nitrogen gas is output from the outlet end to purge the koji powder sample, causing it to fluidize and allowing the volatile substances in the sample to fully volatilize. In practice, the nitrogen flow rate output from the outlet end is 50-100 mL / min, and the gas pressure is 0.05-0.2 MPa.

[0028] In a specific embodiment, in order to obtain a gaseous sample with stable composition, the gaseous structure of the koji powder sample is usually collected after volatilization for 40-50 minutes under water bath heating and nitrogen purging conditions.

[0029] Step S108: The gas phase sample is pre-concentrated using the multi-stage cold trap principle, wherein the pre-concentration is such that the enrichment factor of the gas phase sample is not less than 1000; in the embodiment, the gas phase sample is pre-concentrated using the three-stage cold trap principle, that is, the sample is enriched using a concentrator based on the three-stage cold trap principle.

[0030] Step S110: Collect the pre-concentrated gas phase sample and input it into a gas chromatography-mass spectrometry system for gas chromatography-mass spectrometry analysis. Determine the terpenoids in Daqu by standard gas matching.

[0031] The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) proposed in this invention will be further described in detail below with reference to specific embodiments.

[0032] Example 1 First, 500g of solid koji blocks were crushed and ground until the powder passed through a 40-mesh sieve to obtain 500g of koji powder. The 500g of koji powder was placed in a 1L flask of anhydrous ethanol and evaporated under reduced pressure in a water bath at 50℃ for 2 hours. After filtration, the sample in the flask was filtered, and the solid phase was retained and dried under vacuum at 70℃ for 4 hours to obtain the purified koji powder sample. 100g of the purified koji powder sample was placed in a 500mL wide-mouth bottle and heated in a water bath at 55℃ with nitrogen bottom blowing at a flow rate of 75mL / min and a gas pressure of 0.1MPa, maintaining the sample in a thermally fluidized state for 45 minutes. Then, sampling was started using a concentrator based on the principle of a three-stage cold trap. After concentration and enrichment, the sample was injected into a gas chromatography-mass spectrometry (GC-MS) instrument for gas chromatography-mass spectrometry analysis. The concentrator collects gas from a wide-mouth bottle through a sample tube. Its operating parameters based on the three-stage cold trap principle are as follows: cooling temperature of the first-stage cold trap is -20℃ and desorption temperature is 45℃; cooling temperature of the second-stage cold trap is -55℃ and desorption temperature is 230℃; focusing temperature of the third-stage cold trap is -165℃ and desorption injection pulse temperature is 250℃. The operating parameters for gas chromatography-mass spectrometry (GC-MS) are as follows: injection volume 600 mL; splitless; column: DB-WAX flexible quartz fiber capillary column 60 m x 0.25 mm, 0.25 μm; temperature program: 40 °C for 5 min, increase to 150 °C at a rate of 5 °C / min, hold for 5 min, increase to 210 °C at a rate of 8 °C / min, hold for 8 min; carrier gas: He, flow rate 1.0 mL / min; detector temperature: 250 °C, inlet temperature: 250 °C.

[0033] The operating parameters of the mass spectrometer in the gas chromatography-mass spectrometry system are as follows: EI ionization source, electron energy of 70 eV, electron multiplier voltage of 1610 V, ion source temperature of 200 ℃, transfer line temperature of 250 ℃, and mass scan range of a / z of 35-500 amu.

[0034] The test results are as follows: Figure 2 As shown in Table 1, the detection method of the present invention can detect 12 substances, specifically pinene, camphene, β-pinene, γ-terpinene, (-)-limonene, β-phellandrene, geraniolene, p-menth-1,3,8-triene, α-shogaene, (+)-1,7-diepio-α-cedrene, (+)-ciperene, and (Z, E)-α-farnesene.

[0035] Table 1 shows the data of terpenoids detected by the detection method of the present invention in Example 1.

[0036] Example 2 The difference between Example 2 and Example 1 is that, in this detection method, after the pre-concentrated gas phase sample is injected into the gas chromatograph-mass spectrometer, it is split. One gas phase sample is injected into the mass spectrometer, and the other gas phase sample flows to the olfaction port of the odor meter. The results are shown in Table 2 below. Corresponding to the peak time, the olfaction port can identify the unique odor characteristics of the terpene, such as pinene having a distinct pine smell, (-)-limonene having a fresh lemon smell, and (+)-1,7-diepim-α-cedrene having a balsam-like woody note.

[0037] Table 2 shows the flavor characteristics of each terpene substance detected in Example 2 of the detection method of the present invention, corresponding to that in Example 1.

[0038] Comparative Example 1 For the koji powder sample obtained in Example 1, terpenoids were detected and analyzed using a conventional headspace solid-phase microextraction (HSP) device combined with GC-MS. Conventional HSP used a 20 mL headspace vial, typically taking 2 g of koji powder sample, and extracted in a 50°C water bath for 45 min before GC-MS analysis. Compared to Comparative Example 1, the detection method disclosed in this invention allows for a larger sample loading, and utilizes the three-stage cold trap principle for concentration and enrichment, resulting in higher sample detection levels and more accurate results. A comparison of the detection results of Comparative Example 1 and Example 1 is provided below. Figure 3 As shown in Table 3, the specific test results are compared.

[0039] Table 3 Comparison of the detection of terpenoids in Example 1 and Comparative Example 1 of the present invention

[0040] Combining Tables 1 and 3, it is clear that the detection method disclosed in this invention, through sample pretreatment, can significantly reduce the content of high-content interfering substances before the retention time of 900 s, such as the main component ethyl acetate. Even under the premise of multi-stage cold trap concentration, the peaks of interfering substances are significantly lower than those of conventional headspace solid-phase microextraction, indicating that the detection method of this invention has higher anti-interference ability. Simultaneously, the detection method disclosed in this invention significantly increases the content of terpenes in the gas phase sample after pretreatment of the koji powder, making pinene, with a retention time RT of 900 s, the most abundant flavor compound, thus making the detection of substances more accurate. Figures 4-6 Among the three terpenoids detected in both Example 1 and Comparative Example 1, the peak areas of pinene, (-)-limonene, and β-phellandrene detected by the method of this invention are 124, 32, and 33 times higher than those of conventional headspace solid-phase microextraction, respectively. This fully demonstrates that the detection method disclosed in this invention has higher detection accuracy for terpenoids. Furthermore, the detection method disclosed in this invention can detect 12 terpenoids, while the conventional headspace solid-phase microextraction in Comparative Example 1 only detects 4. This means that the detection method of this invention has a higher detection rate for terpenoids and is more effective in detecting trace amounts of terpenoids in Daqu (a type of Chinese liquor).

[0041] The present invention discloses a method for improving the detection of terpenes in Daqu (a type of Chinese liquor). First, the sample is pretreated to remove interfering substances such as ethyl acetate, which are low-boiling-point and highly concentrated. Then, the sample is allowed to fully volatilize under water bath heating and nitrogen purging conditions. The terpenes in the volatilized substances are then concentrated and enriched using a three-stage cold trap principle, followed by GC-MS detection. Results show that the detection method of the present invention has a higher detection rate and accuracy for trace amounts of terpenes in Daqu compared to existing technologies. Furthermore, the method is convenient to operate, with simple and efficient sample pretreatment, and the overall detection process is highly practical and widely applicable.

[0042] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor), characterized in that, Includes the following steps: 1) The target koji block is pre-treated by crushing to obtain koji powder; 2) Using anhydrous ethanol as a solvent, the koji powder was subjected to rotary evaporation in a water bath at 40-60℃. After rotary evaporation, the solid koji powder was filtered and vacuum dried to obtain the dried koji powder sample. 3) Collect stable gaseous samples of the volatile components from the koji powder sample under water bath heating and nitrogen purging conditions; 4) The gas phase sample is pre-concentrated using the principle of a multi-stage cold trap, wherein the pre-concentration results in an enrichment factor of not less than 1000 for the gas phase sample. 5) Collect the pre-concentrated gas phase sample and input it into a gas chromatography-mass spectrometry system for gas chromatography-mass spectrometry analysis. Determine the terpenoids in Daqu by standard gas matching.

2. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, Step 4) uses the three-stage cold trap principle to pre-concentrate the gas phase sample. The operating parameters of the three-stage cold trap principle are: cooling temperature of the first-stage cold trap -20℃ and desorption temperature of 45℃; cooling temperature of the second-stage cold trap -55℃ and desorption temperature of 230℃; focusing temperature of the third-stage cold trap -165℃ and desorption injection pulse temperature of 250℃.

3. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, In step 5), the operating parameters of the gas chromatography-mass spectrometry system are as follows: injection volume 300~1200mL; splitless; column: DB-WAX flexible quartz fiber capillary column 60m x 0.25 mm, 0.25μm; temperature program: 40℃ for 5min, increase to 150℃ at a rate of 5℃ / min, hold for 5min, increase to 210℃ at a rate of 8℃ / min, hold for 8min; carrier gas: He, flow rate 1.0mL / min; detector temperature: 250℃, inlet temperature: 250℃.

4. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 3, characterized in that, In step 5), the operating parameters of the mass spectrometer in the gas chromatography-mass spectrometry system are as follows: EI ionization source, electron energy of 70 eV, electron multiplier voltage of 1610 V, ion source temperature of 200 °C, transfer line temperature of 250 °C, and mass scan range a / z of 35-500 amu.

5. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, In step 3), the temperature for heating the koji powder sample in a water bath is 40-60℃.

6. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, In step 3), the flow rate of nitrogen purging the koji powder sample is 50~100mL / min, and the gas pressure is 0.05~0.2MPa.

7. The detection method for enhancing the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, Also includes: After pre-concentration, the gaseous sample is injected into the gas chromatograph-mass spectrometer and then split. One stream of the gaseous sample is injected into the mass spectrometer, and the other stream flows to the olfaction port of the olfaction meter.

8. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, The detection method identified 12 terpenoids, including pinene, camphene, β-pinene, γ-terpinene, (-)-limonene, β-phellandrene, geraniolene, p-menth-1,3,8-triene, α-shogaene, (+)-1,7-diepio-α-cedrene, (+)-monoene, and (Z,E)-α-farnesene.

9. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, The conditions for vacuum drying of the solid-phase powder in step 2) are: drying for 2-5 hours under vacuum conditions at an ambient temperature of 70℃.

10. The detection method for improving the detection of terpenoids in Daqu (a type of Chinese liquor) according to claim 1, characterized in that, The particle size of the koji powder obtained by crushing in step 1) is 40-100 mesh.

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