A method for constructing a cold-brewed coffee fingerprint, the fingerprint and application thereof

Abstract

The present application relates to a kind of cold extraction coffee fingerprint construction method and its fingerprint and application, make cold extraction coffee by headspace solid phase microextraction processing, the extract obtained is carried out gas chromatography-mass spectrometry analysis, obtain the fingerprint of the cold extraction coffee, wherein, when carrying out the gas chromatography-mass spectrometry analysis, split injection mode is used, and the split injection ratio is controlled to be (3-6):1.The obtained fingerprint can describe the quality factor of flavor substance from the whole of finished product, comprehensively reflect the extraction quality of coffee, provide a kind of fast, simple method for the quality judgment of cold extraction coffee, and then guide the production of the coffee beverage with repeatable high quality, high stability of cold extraction coffee.

Description

Technical Field

[0001] This invention belongs to the field of food testing and analysis technology, specifically relating to a method for constructing a fingerprint spectrum of cold brew coffee, the fingerprint spectrum itself, and its application. Background Technology

[0002] Coffee has become one of the most popular beverages worldwide. Based on consumer preferences, the market offers various types of brewed coffee, such as espresso, pour-over coffee, and cold brew coffee. Among these, cold brew coffee, made with water at room temperature or lower, avoids prolonged exposure to heat during the extraction process, emphasizing quality and health. As a new product offering unique flavor and convenient preparation, it is gradually gaining market recognition, experiencing rapid market share growth, and becoming a new growth trend in the entire coffee industry.

[0003] While cold brew coffee offers consumers a new sensory experience and choice, little is known about its key aroma compounds. Currently, there is no readily available fingerprint for cold brew coffee, making it difficult to produce high-quality beverages in a reproducible manner. This results in inconsistent quality of cold brew coffee on the market, impacting consumer acceptance. Summary of the Invention

[0004] Based on the problems existing in the prior art, the purpose of this invention is to provide a method for constructing a fingerprint spectrum of cold brew coffee, as well as the fingerprint spectrum and its application, to comprehensively ensure the quality of cold brew coffee.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first objective of this invention is to provide a method for constructing a fingerprint spectrum of cold brew coffee, wherein cold brew coffee is treated by headspace solid phase microextraction (HS-SPME), and the resulting extract is analyzed by gas chromatography-mass spectrometry (GC-MS) to obtain the fingerprint spectrum of the cold brew coffee, wherein the GC-MS analysis is performed in a split injection mode, and the injection split ratio is controlled to be (3-6):1.

[0007] Preferably, the headspace solid-phase microextraction process is as follows: the cold-brewed coffee mixed in the headspace vial is controlled to be in a gas-liquid equilibrium state, and then the extraction head of the solid-phase microextraction device is used to adsorb at 40-60°C for 20-50 min, and finally the temperature at the injection port of the gas chromatograph is adjusted to 250-260°C for 2-5 min for desorption.

[0008] Furthermore, the adsorption temperature is controlled to be 50–60°C.

[0009] Furthermore, the adsorption time is controlled to be 30–40 min.

[0010] Furthermore, the temperature of the analysis is controlled to be 250–255°C.

[0011] Furthermore, the parsing time is controlled to be 2 to 4 minutes.

[0012] In this invention, heating is used to control the cold brew coffee to a state of gas-liquid equilibrium.

[0013] Furthermore, the cold brew coffee is kept at a temperature of 40–50°C for 2–5 minutes to control it to be in a state of gas-liquid equilibrium.

[0014] Furthermore, the cold brew coffee is kept at a temperature of 45–50°C for 2–3 minutes to control it to be in a state of gas-liquid equilibrium.

[0015] Preferably, when performing the headspace solid-phase microextraction (HSP) process, the extraction head used is selected from CAR / PDMS solid-phase microextraction head or DVB / CAR / PDMS solid-phase microextraction head; preferably, it is a DVB / CAR / PDMS extraction head.

[0016] Preferably, the construction method further includes an aging treatment of the extraction head before performing the headspace solid-phase microextraction process.

[0017] Furthermore, the aging treatment step specifically involves inserting the extraction head into the gas chromatograph injection port and placing it at 270–290°C for 10–20 minutes.

[0018] More preferably, the aging treatment step specifically involves inserting the extraction head into the gas chromatograph injection port and placing it at 275–285°C for 13–17 minutes. This aging treatment ensures that the SPME head effectively adsorbs volatile components without affecting subsequent desorption, facilitating the detection of volatile components in cold brew coffee.

[0019] According to some specific and preferred embodiments, the headspace solid-phase microextraction process is as follows: cold brew coffee is transferred into a headspace bottle, mixed, and heated to reach a gas-liquid equilibrium state. Then, the extraction head of the aged solid-phase microextraction device is inserted for adsorption. Finally, the extraction head is analyzed at the injection port of a gas chromatograph.

[0020] According to one embodiment, the chromatographic conditions for performing the gas chromatography-mass spectrometry (GC-MS) analysis include: an injection port temperature of 250–260°C, and a temperature program of starting at 35–40°C and holding for 2–5 min, then increasing the temperature at 3–6°C / min to 240–250°C and holding for 4–6 min.

[0021] Furthermore, the temperature of the injection port is 250–255°C.

[0022] More preferably, the heating program is as follows: starting at 38-40°C and holding for 2-4 minutes, then increasing the temperature to 240-245°C at a rate of 3-4°C / min and holding for 4-5 minutes.

[0023] According to another embodiment, the heating program is as follows: the initial temperature is 35-40°C, held for 2-5 minutes, then increased to 120-140°C at a rate of 3-5°C / min, and then increased to 240-250°C at a rate of 15-20°C / min.

[0024] Furthermore, the heating program is as follows: start at a temperature of 38-40°C and hold for 2-4 minutes, increase the temperature to 130-140°C at a rate of 3-4°C / min, and then increase the temperature to 240-245°C at a rate of 18-20°C / min.

[0025] Preferably, helium is used as the carrier gas for the gas chromatography-mass spectrometry analysis, and the column flow rate is controlled at 0.5 to 1 mL / min.

[0026] Furthermore, the column flow rate was controlled at 0.8–1 mL / min.

[0027] Preferably, the chromatographic column used in the gas chromatography-mass spectrometry analysis is a TG-5ms capillary column.

[0028] Preferably, the mass spectrometry conditions for performing the gas chromatography-mass spectrometry analysis include: using an EI source as the ion source, an electron energy of 70 eV, an interface temperature of 250–260 °C, and a mass scan range of 45–550 m / z.

[0029] Preferably, the method for preparing cold brew coffee is as follows: after mixing pre-wetted coffee powder with water, extraction is carried out using continuous negative pressure to obtain cold brew coffee extract, and then cold brew coffee is obtained by filtration and sterilization.

[0030] Furthermore, the pressure during extraction under continuous negative pressure is controlled to be 0.001–0.1 MPa.

[0031] Furthermore, the extraction time for continuous negative pressure extraction is controlled to be 2 to 8 hours; preferably 4 to 6 hours.

[0032] Furthermore, the mass ratio of coffee powder to water in the pre-wetted coffee powder is 1:(1~1.5). This amount of water can ensure that the coffee powder is fully wetted without water seeping out, which is beneficial for the subsequent extraction steps and for the preservation of aroma substances.

[0033] Furthermore, the pre-wetted coffee powder is prepared using water at a temperature of 0–6°C.

[0034] The coffee powder in this invention is obtained by grinding coffee beans. Further, the proportion of coffee powder with a particle size of 200-1000 μm in the pre-wetted coffee powder is ≥50%; more preferably, the proportion of coffee powder with a particle size of 600-1000 μm is ≥50%.

[0035] Furthermore, the mass ratio of the pre-wetted coffee powder to the water at 0-6°C is controlled to be 1:(6-8).

[0036] Furthermore, the pre-wetted coffee powder is mixed with water by spraying.

[0037] A second objective of this invention is to provide a fingerprint spectrum constructed according to the above-described construction method.

[0038] Preferably, the fingerprint spectrum includes 10 characteristic peaks, and the relative retention times of the 10 characteristic peaks are as follows: peak 1 - 5.94 min, peak 2 - 7.14 min, peak 3 - 9.53 min, peak 4 - 12.75 min, peak 5 - 13.27 min, peak 6 - 14.41 min, peak 7 - 17.10 min, peak 8 - 19.89 min, peak 9 - 21.52 min, and peak 10 - 25.86 min.

[0039] Furthermore, by identifying and matching the data using the NIST14 database, the 10 characteristic peaks were confirmed to be: peak 1 - 2-methylfuran, peak 2 - 2-methylbutanal, peak 3 - pyridine, peak 4 - methylpyrazine, peak 5 - furfural, peak 6 - 2-furanethanol, peak 7 - 2-acetylfuran, peak 8 - 5-methyl-2-furancarbaldehyde, peak 9 - methyl furan acetate, and peak 10 - 3-ethyl-2,5-dimethylpyrazine.

[0040] Preferably, the fingerprint spectrum is as follows: Figure 1 As shown.

[0041] A third objective of this invention is to provide a method for constructing the above-mentioned cold brew coffee fingerprint spectrum and / or the application of the above-mentioned fingerprint spectrum in the quality evaluation of cold brew coffee.

[0042] The quality evaluation method for cold brew coffee is as follows: the cold brew coffee to be tested is measured according to the above construction method to obtain the total ion current chromatogram of the volatile components of the cold brew coffee to be tested, and then it is determined whether the total ion current chromatogram of the volatile components has the 10 characteristic peaks in the fingerprint spectrum.

[0043] Furthermore, the quality evaluation method also includes judging whether the total ion chromatogram of the volatile components matches that of the volatile components. Figure 1 Does the similarity of the fingerprint patterns shown be greater than 0.900?

[0044] Furthermore, when the total ion chromatogram of the volatile components of the cold brew coffee to be tested has a similarity greater than 0.900 with the fingerprint spectrum, and simultaneously contains the 10 characteristic peaks, the quality of the cold brew coffee sample is determined to meet the production standards.

[0045] Preferably, the cold brew coffee to be tested refers to cold brew coffee obtained by the following preparation method, specifically:

[0046] Coffee beans are ground into coffee powder, with at least 50% having a particle size of 200–1000 μm. The coffee powder is mixed with water (0–6°C) at a mass ratio of 1:1–1.5. This amount of water ensures the coffee powder is adequately wetted without seeping out, which is beneficial for subsequent extraction steps and for preserving aroma compounds. After pre-wetting, water is added via a spray system, with a ratio of pre-wetted coffee powder to spray water of 1:6–8. The coffee solution is extracted using a continuous negative pressure extraction method to obtain a cold brew coffee extract. The water temperature is controlled at 0–6°C, the extraction pressure at 0.001–0.1 MPa, and the extraction time at 2–8 hours. The extract is then filtered through a cloth bag and sterilized using UV or membrane filtration to obtain the cold brew coffee product.

[0047] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0048] 1. This invention utilizes HS-SPME-GC-MS to determine the flavor components of cold brew coffee, thereby establishing a fingerprint spectrum for cold brew coffee. The cold brew coffee fingerprint spectrum can comprehensively describe the flavor compounds of the finished product, fully reflecting the extraction quality of the coffee. This provides a rapid and convenient method for judging the quality of cold brew coffee, and further guides the production of reproducible, high-quality, and highly stable cold brew coffee beverages.

[0049] 2. By comparing the similarity and characteristic peaks of the sample with the HS-SPME-GC-MS fingerprint spectrum of cold brew coffee in this invention, the quality of the cold brew coffee to be tested can be fed back in a timely manner, and a comprehensive and systematic evaluation of the quality of cold brew coffee in production can be made, so as to promote the production of cold brew coffee to be more scientific, stable and standardized.

[0050] 3. This invention is very helpful in identifying and classifying cold brew coffee from different brands, and to a certain extent, it can curb the entry of low-quality or inferior cold brew coffee into the market, which has significant social benefits for creating a healthy and safe cold brew coffee market. Attached Figure Description

[0051] Figure 1 Fingerprint spectrum of cold brew coffee obtained in Example 1.

[0052] Figure 2 Total ion chromatograms of flavor compounds from four batches of cold brew coffee.

[0053] Figure 3 The effect of different extraction fiber heads on the total ion chromatogram of flavor compounds in cold brew coffee in Example 2.

[0054] Figure 4 The effect of split ratio on the total ion chromatogram of flavor compounds in cold brew coffee in Example 3.

[0055] Figure 5 The effect of chromatographic detection conditions on the total ion chromatogram of flavor compounds in cold brew coffee in Example 4.

[0056] Figure 6 The effect of extraction time on the total ion chromatogram of flavor compounds in cold brew coffee in Example 5.

[0057] Figure 7 The effect of extraction temperature on the total ion chromatogram of flavor compounds in cold brew coffee in Example 6.

[0058] Figure 8 Total ion current chromatogram of random batches of cold brew coffee for quality inspection. Detailed Implementation

[0059] All features disclosed in this invention, or steps in all methods or processes disclosed, may be combined in any way, except for mutually exclusive features or steps.

[0060] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0061] In this invention, cold brew coffee is treated with headspace solid-phase microextraction (HS-SPME) to extract and collect volatile aroma components. The resulting extract is then analyzed by gas chromatography-mass spectrometry (GC-MS). A standard fingerprint spectrum for cold brew coffee is constructed by plotting relative retention time on the x-axis and average peak area on the y-axis. The obtained fingerprint spectrum shows high separation of characteristic peaks, improved peak shapes, and a higher detection rate of volatile substances. This fingerprint spectrum construction method is stable, reliable, reproducible, and precise, and is simple and requires minimal input.

[0062] Furthermore, by optimizing several relevant conditions in the HS-SPME and GC-MS analysis processes, the sensitivity, reproducibility, and stability of the fingerprint spectrum construction method were improved. Through analysis and comparison of fingerprint spectra obtained from multiple batches of cold brew coffee, 10 characteristic peaks with strong response intensity and good separation were identified, with retention times of: peak 1—5.94 min, peak 2—7.14 min, peak 3—9.53 min, peak 4—12.75 min, peak 5—13.27 min, peak 6—14.41 min, peak 7—17.10 min, peak 8—19.89 min, peak 9—21.52 min, and peak 10—25.86 min. These characteristic peaks constitute the fingerprint characteristics of cold brew coffee and can be used as the standard fingerprint spectrum for cold brew coffee. The NIST14 database was used for identification and matching. The 10 characteristic peaks were identified sequentially according to their elution time as follows: Peak 1—2-methylfuran, Peak 2—2-methylbutyraldehyde, Peak 3—pyridine, Peak 4—methylpyrazine, Peak 5—furfural, Peak 6—2-furanethanol, Peak 7—2-acetylfuran, Peak 8—5-methyl-2-furancarbaldehyde, Peak 9—methyl furan acetate, and Peak 10—3-ethyl-2,5-dimethylpyrazine. The constructed fingerprint spectrum can be used for quality identification of various cold brew coffees.

[0063] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0064] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the experimental materials used, unless otherwise specified, were purchased from conventional biochemical reagent manufacturers.

[0065] Example 1

[0066] This embodiment provides a method for constructing a fingerprint spectrum of cold brew coffee, and the specific implementation steps are as follows:

[0067] (1) First, the DVB / CAR / PDMS 50 / 30μm fiber head of the solid phase microextraction device was inserted into the gas chromatograph injection port and placed at 280℃ for 15min for aging treatment, so that the SPME head has a good adsorption effect on volatile components and will not affect the subsequent desorption, which is convenient for the detection of volatile components in cold brew coffee.

[0068] (2) Take 5 mL of the prepared cold brew coffee sample and transfer it into a 15 mL headspace vial. Mix it on a magnetic stirrer and heat it at 50 °C for 2 min to achieve gas-liquid equilibrium. Insert the extraction head of the solid phase microextraction device into the headspace vial and adsorb it at 50 °C for 30 min. Finally, decompose the extraction head at 250 °C for 3 min at the inlet.

[0069] (3) The GC-MS instrument used was a Thermo Fisher Scientific TSQ 8000 gas chromatograph-mass spectrometer; the chromatographic column was a TG-5ms capillary column (30m, 0.25mm, 0.25μm). Chromatographic conditions: injection port temperature 250℃, constant temperature 40℃ for 3 min, then increased to 240℃ at 3℃ / min and held for 5 min; injection mode, 5:1 split injection; helium as carrier gas, column flow rate 1mL / min; mass spectrometry conditions: EI ion source, electron energy 70eV, interface temperature 250℃, mass scan range: 45-550m / z. Identification and matching were performed using the NIST14 database.

[0070] Analysis results as follows Figure 1 And as shown in Table 1. Among them... Figure 1 The fingerprint spectrum of cold brew coffee is shown in Table 1, which is a table of peak area normalized content corresponding to flavor compounds in cold brew coffee.

[0071] This embodiment also provides a fingerprint spectrum. Using the above construction method, four batches of cold brew coffee were analyzed to construct fingerprint spectra, and the results are as follows: Figure 2 As shown. Figure 2 Total ion chromatograms for flavor compounds analysis of four batches of cold brew coffee.

[0072] A fingerprint spectrum was developed by analyzing and comparing fingerprint spectra established using the aforementioned method on four batches of coffee samples. Ten characteristic peaks with high response intensity and good separation were identified, with retention times as follows: Peak 1—5.94 min, Peak 2—7.14 min, Peak 3—9.53 min, Peak 4—12.75 min, Peak 5—13.27 min, Peak 6—14.41 min, Peak 7—17.10 min, Peak 8—19.89 min, Peak 9—21.52 min, and Peak 10—25.86 min. These characteristic peaks constitute the fingerprint characteristics of cold brew coffee and can be used as a standard fingerprint spectrum for cold brew coffee.

[0073] The 10 characteristic peaks were identified in order of their elution time as follows: Peak 1 – 2-methylfuran, Peak 2 – 2-methylbutanal, Peak 3 – pyridine, Peak 4 – methylpyrazine, Peak 5 – furfural, Peak 6 – 2-furanethanol, Peak 7 – 2-acetylfuran, Peak 8 – 5-methyl-2-furancarbaldehyde, Peak 9 – methyl furan acetate, and Peak 10 – 3-ethyl-2,5-dimethylpyrazine.

[0074] Table 1. Normalized peak area content of flavor compounds in cold brew coffee

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084] Example 2

[0085] This embodiment provides a method for constructing HS-SPME-GC-MS fingerprints of cold brew coffee. The specific implementation steps are as follows:

[0086] (1) First, the three fiber heads of the solid phase microextraction device, namely single-phase PDMS-100μm, dual-phase CAR / PDMS-75μm, and three-phase DVB / CAR / PDMS-50 / 30μm, were inserted into the gas chromatograph injection port and placed at 280℃ for 15min for aging treatment. This ensured that the SPME head had a good adsorption effect on volatile components and would not affect the subsequent desorption, which facilitated the detection of volatile components in cold brew coffee.

[0087] (2) Take 5 mL of the prepared cold brew coffee sample and transfer it into a 15 mL headspace vial. Mix it on a magnetic stirrer and heat it at 50 °C for 2 min to achieve gas-liquid equilibrium. Insert the extraction head of the solid phase microextraction device into the headspace vial and adsorb it at 30 °C for 30 min. Finally, decompose the extraction head at 250 °C for 3 min at the inlet.

[0088] (3) The GC-MS instrument used was a Thermo Fisher Scientific TSQ 8000 gas chromatograph-mass spectrometer; the column was a TG-5ms capillary column (30m, 0.25mm, 0.25μm). Chromatographic conditions were: TG-5ms capillary column (30m, 0.25mm, 0.25μm), injection port temperature 250℃, initial temperature 40℃ held for 3 min, increased to 140℃ at 4℃ / min, then increased to 240℃ at 20℃ / min; injection mode: splitless injection, helium as carrier gas, column flow rate 1mL / min; mass spectrometry conditions: EI ion source, electron energy 70eV, interface temperature 250℃, mass scan range: 45-550m / z. NIST14 database was used for identification and matching.

[0089] A comparative analysis was conducted on the adsorption effect of the extraction fiber head on volatile substances in cold brew coffee. The test results are as follows: Figure 3 As shown.

[0090] Depend on Figure 3 It was found that the types of volatile substances adsorbed by different fiber heads varied significantly. The three-phase fiber head (DVB / CAR / PDMS) showed the best adsorption effect, identifying 185 aroma components; followed by CAR / PDMS, identifying 162 aroma components; PDMS showed the worst adsorption effect, identifying only 137 aroma components. This indicates that using a DVB / CAR / PDMS fiber head is more conducive to the accurate and comprehensive detection of volatile components in cold brew coffee.

[0091] Example 3

[0092] This embodiment provides a method for constructing a cold brew coffee HS-SPME-GC-MS fingerprint spectrum, which is basically the same as that in embodiment 2, except that in step (3), the injection modes are splitless and split ratio 5:1.

[0093] A comparative analysis of the effect of split ratio on the separation of volatile substances in cold brew coffee was conducted, and the results are as follows: Figure 4 As shown.

[0094] Depend on Figure 4 It can be seen that without split injection, the sample is overloaded, resulting in poor sample resolution. When a split ratio of 5:1 is used, the sample resolution is significantly improved, and the peak shape of the chromatogram is significantly improved. The split ratio is a very important parameter in the injection conditions. If the sample injection volume is too high, the solvent volume expands severely, causing the inlet liner to overload, resulting in sample loss due to the sample flowing out of the purge outlet. It will also cause contamination of the carrier gas input line.

[0095] Example 4

[0096] This embodiment provides a method for constructing HS-SPME-GC-MS fingerprints of cold brew coffee, which is basically the same as that in Embodiment 2, except that the chromatographic conditions and injection mode are changed in step (3). Specifically:

[0097] Chromatographic conditions 1: Injector temperature 250℃, constant temperature 40℃ for 3 min, then increase to 240℃ at 3℃ / min and hold for 5 min; injection mode, 5:1 split injection; helium as carrier gas, column flow rate 1 mL / min.

[0098] Chromatographic conditions 2: Injector temperature 250℃, constant temperature 40℃ for 3 min, then increase to 240℃ at 6℃ / min and hold for 5 min; injection mode, 5:1 split injection; helium as carrier gas, column flow rate 1 mL / min.

[0099] Chromatographic conditions 3: Injector temperature 250℃, constant temperature 40℃ for 3 min, temperature increased to 140℃ at 4℃ / min, and then increased to 240℃ at 20℃ / min; injection mode, 5:1 split injection; helium as carrier gas, column flow rate 1mL / min.

[0100] The effects of chromatographic conditions and split ratio on the separation of volatile substances in cold brew coffee were compared and analyzed. The results are as follows: Figure 5 As shown.

[0101] Depend on Figure 5 It can be seen that there is no significant difference in the detection results under the three chromatographic conditions. However, when using chromatographic condition 1 for GC-MS detection, more volatile substances were detected, therefore chromatographic condition 1 was selected.

[0102] Example 5

[0103] This embodiment provides a method for constructing HS-SPME-GC-MS fingerprints of cold brew coffee, which is basically the same as that in Embodiment 2, except that the extraction time in step (2) and the chromatographic conditions and injection mode in step (3) are changed. Specifically:

[0104] In step (2), the extraction times for headspace solid-phase microextraction are 20 min, 30 min, 40 min, 50 min, and 60 min, respectively. In step (3), the chromatographic conditions are: injection port temperature 250℃, constant temperature 40℃ for 3 min, temperature increased to 240℃ at 3℃ / min, and held for 5 min; injection mode, 5:1 split injection; helium as carrier gas, column flow rate 1 mL / min.

[0105] A comparative analysis of the effects of extraction time on the volatile substances in cold brew coffee was conducted, and the results are as follows: Figure 6 As shown.

[0106] Depend on Figure 6It is known that an extraction time of 30–40 min yields the best extraction effect, identifying a greater number of volatile substances. Shorter or longer extraction times are detrimental to the extraction of volatile substances. Solid-phase microextraction (SPE) adsorption is a process of enrichment equilibrium between the analyte and the fiber head coating. Once equilibrium is reached, the concentration of the analyte between the two phases becomes constant. However, if the extraction time is too long, it will reduce the adsorption capacity of the fiber head for the analyte, resulting in a decrease in the adsorption amount.

[0107] Example 6

[0108] This embodiment provides a method for constructing HS-SPME-GC-MS fingerprints of cold brew coffee, which is basically the same as that in Embodiment 1, except that the extraction temperatures of headspace solid-phase microextraction are 20℃, 30℃, 40℃, 50℃, and 60℃.

[0109] A comparative analysis of the effect of extraction temperature on the volatile substances in cold brew coffee was conducted, and the results are as follows: Figure 7 As shown.

[0110] Depend on Figure 7 It can be seen that the more types of samples are adsorbed, the higher the temperature. The adsorption effect is better when the extraction temperature reaches 50℃, and then the adsorption effect reaches equilibrium. When the extraction temperature reaches 60℃, there is no significant change in the types of samples adsorbed.

[0111] Performance testing

[0112] 1. Precision experiment: Take the same batch of cold brew coffee solution, and inject it 5 times consecutively according to the method of constructing the cold brew coffee fingerprint spectrum in Example 1. Compare the relative retention time and relative peak area of ​​each common peak, and calculate the relative standard deviation of each peak.

[0113] The results showed that the relative retention times of the common peaks were basically consistent, and the RSD values ​​were all less than 0.82%; the RSD values ​​of the relative peak areas of the common peaks were all less than 3.24%, indicating that the fingerprint analysis of cold brew coffee met the requirements of precision testing.

[0114] 2. Reproducibility test: Take 5 portions of the same batch of cold brew coffee solution, prepare parallel sample solutions, and analyze them according to the method for constructing the cold brew coffee fingerprint spectrum in Example 1. Compare the relative retention time and relative peak area of ​​each common peak, and calculate the relative standard deviation of each peak.

[0115] The results showed that the relative retention times of the common peaks were basically consistent, and the RSD values ​​were all less than 0.94%; the RSD values ​​of the relative peak areas of the common peaks were all less than 4.15%, indicating that the fingerprint analysis of cold brew coffee met the requirements of reproducibility experiments.

[0116] 3. Stability test: Take the same batch of cold brew coffee solution and place it for 0, 4, 8, 12, 16, 20 and 24 hours respectively. Then, according to the method of constructing the cold brew coffee fingerprint spectrum in Example 1, inject the sample for analysis, compare the relative retention time and relative peak area of ​​each common peak, and calculate the relative standard deviation of each peak.

[0117] The results showed that the relative retention times of the common peaks were basically consistent, and the RSD values ​​were all less than 1.22%; the RSD values ​​of the relative peak areas of the common peaks were all less than 6.19%, indicating that the fingerprint analysis of cold brew coffee met the requirements of the stability experiment.

[0118] The above experimental results show that the fingerprint spectrum determination method is precise, stable, and reliable.

[0119] 4. Cold Brew Coffee Quality Identification: Take one sample from each of the three batches of cold brew coffee liquid to be tested, and obtain the total ion current chromatogram of the sample according to the method for constructing the fingerprint spectrum of cold brew coffee in Example 1; and compare it with the constructed fingerprint spectrum of cold brew coffee (in Example 1) according to the evaluation method in the "Similarity Evaluation System for Fingerprint Spectrum of Traditional Chinese Medicine (2012 Edition)". Figure 1 Feature peak matching and similarity detection were performed, and the results are shown in [link to results]. Figure 8 .

[0120] The identification criteria are as follows: if the total ion chromatogram of the volatile components of the sample to be tested has a similarity of more than 0.900 with the constructed GC / MS fingerprint template, and simultaneously contains 10 characteristic peaks in the constructed GC / MS fingerprint, then the batch of cold brew coffee samples is judged to meet the production standards.

[0121] Figure 8 The results show that the total ion chromatograms of volatile components in these three batches of cold brew coffee are similar to the fingerprint chromatograms of cold brew coffee already constructed (in Example 1). Figure 1 The similarities were 0.982, 0.995, and 0.986, respectively, all greater than 0.900. Furthermore, the total ion chromatograms of volatile components in these three batches of cold brew coffee all contained 10 characteristic peaks, ordered as follows: Peak 1 – 2-methylfuran, Peak 2 – 2-methylbutyraldehyde, Peak 3 – pyridine, Peak 4 – methylpyrazine, Peak 5 – furfural, Peak 6 – 2-furanethanol, Peak 7 – 2-acetylfuran, Peak 8 – 5-methyl-2-furancarbaldehyde, Peak 9 – methyl furan acetate, Peak 10 – 3-ethyl-2,5-dimethylpyrazine. Therefore, it was determined that the quality of these three batches of cold brew coffee met the production standards.

[0122] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for evaluating the quality of cold brew coffee, characterized in that, Includes the following steps: (1) Cold brew coffee is subjected to headspace solid-phase microextraction, and the resulting extract is analyzed by gas chromatography-mass spectrometry to obtain the fingerprint spectrum of the cold brew coffee, wherein, The headspace solid-phase microextraction process is as follows: the cold brew coffee mixed in the headspace bottle is controlled to be in a gas-liquid equilibrium state, and then the extraction head of the solid-phase microextraction device is used to adsorb at 50°C for 30 min. Finally, the temperature at the injection port of the gas chromatograph is adjusted to 250°C for 3 min for desorption. When performing the headspace solid-phase microextraction process, the extraction head used is selected from the DVB / CAR / PDMS-50 / 30μm solid-phase microextraction head; When performing the gas chromatography-mass spectrometry analysis, a split injection mode was used, and the injection split ratio was controlled at 5:

1. The chromatographic conditions for the gas chromatography-mass spectrometry (GC-MS) analysis included: an injection port temperature of 250°C; a temperature program of starting at 40°C and holding for 3 min, then increasing to 240°C at a rate of 3°C / min and holding for 5 min; helium was used as the carrier gas, and the column flow rate was controlled at 1 mL / min. The mass spectrometry conditions included: an EI source as the ion source; an electron energy of 70 eV; an interface temperature of 250°C; a mass scan range of 45–550 m / z; and a TG-5 ms capillary column. The fingerprint spectrum includes 10 characteristic peaks, which are: peak 1—2-methylfuran, peak 2—2-methylbutanal, peak 3—pyridine, peak 4—methylpyrazine, peak 5—furfural, peak 6—2-furanethanol, peak 7—2-acetylfuran, peak 8—5-methyl-2-furancarbaldehyde, peak 9—methyl furan acetate, and peak 10—3-ethyl-2,5-dimethylpyrazine. The relative retention times of the 10 characteristic peaks are: peak 1—5.94 min, peak 2—7.14 min, peak 3—9.53 min, peak 4—12.75 min, peak 5—13.27 min, peak 6—14.41 min, peak 7—17.10 min, peak 8—19.89 min, peak 9—21.52 min, and peak 10—25.86 min. (2) The cold brew coffee to be tested is analyzed by headspace solid phase microextraction and gas chromatography-mass spectrometry as described in step (1) to obtain the total ion chromatogram of the volatile components of the cold brew coffee to be tested; (3) Determine whether the total ion chromatogram of the volatile components of the cold brew coffee to be tested simultaneously has the 10 characteristic peaks in the fingerprint spectrum of step (1), and calculate the similarity between the total ion chromatogram of the volatile components and the fingerprint spectrum; when the total ion chromatogram of the volatile components of the cold brew coffee to be tested simultaneously has the 10 characteristic peaks, and the similarity with the fingerprint spectrum is greater than 0.900, it is determined that the quality of the cold brew coffee sample meets the standard.

2. The method for evaluating the quality of cold brew coffee according to claim 1, characterized in that: Step (1) further includes an aging process for the extraction head before performing the headspace solid-phase microextraction treatment. The aging process specifically involves inserting the extraction head into the gas chromatograph inlet and placing it at 270–290°C for 10–20 minutes.

3. The method for evaluating the quality of cold brew coffee according to claim 1, characterized in that: The method for preparing cold brew coffee is as follows: after mixing pre-wetted coffee powder with water, extraction is carried out using continuous negative pressure to obtain cold brew coffee extract, which is then filtered and sterilized to obtain cold brew coffee.

4. The method for evaluating the quality of cold brew coffee according to claim 3, characterized in that: The water temperature during continuous negative pressure extraction is controlled to be 0–6°C; and / or, the pressure during continuous negative pressure extraction is controlled to be 0.001–0.1 MPa; and / or, the extraction time during continuous negative pressure extraction is controlled to be 2–8 h; and / or, the mass ratio of coffee powder to water in the pre-wetted coffee powder is 1:(1–1.5); and / or, the pre-wetted coffee powder is prepared using water at a temperature of 0–6°C; and / or, the proportion of coffee powder with a particle size of 200–1000 μm in the pre-wetted coffee powder is ≥50%; and / or, the mass ratio of the pre-wetted coffee powder to water is controlled to be 1:(6–8); and / or, the water is added by spraying when the pre-wetted coffee powder is mixed with water.

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