CN-122016980-A - In-situ real-time determination method, system and application of fragrance dynamic change in black tea drying process

Abstract

The invention relates to an in-situ real-time determination method, equipment and application of dynamic change of a flavor in a black tea drying process, which are used for obtaining a calibration sample, monitoring VOC (volatile organic compounds) generated by the sample in the drying process on line, screening and obtaining a VOC (volatile organic compound) marker combination related to the flavor, constructing a flavor discriminating model based on the VOC marker combination, obtaining a sample to be tested, drying the sample to be tested, inputting the flavor discriminating model based on the VOC generated by the sample to be tested in real time in the processing process, obtaining a corresponding flavor, and applying the method to different stages of flavor conversion in black tea foot fire drying. The invention has the advantages of high response speed, simple detection process, no need of pretreatment, in-situ, real-time and online detection, etc.

Inventors

• LI JIA
• SHAN XUJIANG
• JIANG YONGWEN
• ZHOU QINGHUA
• CHEN LE
• YUAN HAIBO
• ZHU JIAYI

Assignees

• 中国农业科学院茶叶研究所

Dates

Publication Date

20260512

Application Date

20251228

Claims (10)

1. 1. The method is characterized in that a calibration sample is obtained, VOC generated by the sample in the drying process is monitored on line, and VOC marker combination related to the flavor is obtained through screening; constructing a flavor type discrimination model based on the VOC marker combination; And obtaining a sample to be detected, drying the sample to be detected, and inputting the VOC (volatile organic compounds) generated in real time based on the sample to be detected into the odor type discriminating model in the processing process to obtain the corresponding odor type.
2. 2. A method for in situ real-time determination of a dynamic change in a aroma profile during black tea drying according to claim 1, wherein said VOC marker combination associated with the aroma profile is geranic acid, (E, E) -2, 4-nonadienal, trans-2-hexenal, 1-octanol, phenylacetaldehyde, phenethyl alcohol, beta-linalool, trans-2-nonanal and trans-citral.
3. 3. The method for in-situ real-time measurement of aroma dynamic change in black tea drying process according to claim 1, wherein the calibration sample is a black tea sample treated by rough fire, and the moisture content of the calibration sample is 20% -25%.
4. 4. An in situ real time determination method of flavor dynamic change in black tea drying process as claimed in claim 1, wherein screening and obtaining VOC marker combinations associated with flavor comprises the steps of: s1.1, the calibration sample comprises an analysis group, the calibration sample of the analysis group is dried according to preset experimental heat, and HPPI-TOFMS is applied to online monitor VOC generated in the processing process of the analysis group according to preset frequency f1 and collect an original mass spectrogram in real time; s1.2, performing compound characterization on the VOC detected by HPPI-TOFMS based on a standard substance; S1.3, preprocessing original mass spectrum data, extracting characteristics, and obtaining the mass-to-charge ratio of VOC ions and the corresponding mass spectrum response intensity; S1.4, establishing a mixed screening mechanism, and screening VOC marker combinations corresponding to different aroma types.
5. 5. The method for in-situ real-time measurement of flavor dynamic change in black tea drying process according to claim 4, wherein the calibration sample further comprises a control group, the calibration sample of the control group is dried under a preset experiment fire, VOC generated in the control group treatment process is used as a control sample under a preset frequency f2, expert evaluation data of the control sample are correspondingly obtained, and a mixing screening mechanism is guided, wherein f1> f2.
6. 6. A method for in-situ real-time measurement of aroma type dynamic change in black tea drying process as set forth in claim 4, wherein in S1.4, the mixed screening mechanism performs statistical analysis based on data combination of moisture change rate, aroma attribute and VOC relative intensity information, and obtains VOC marker combinations corresponding to different aroma types according to set threshold value screening.
7. 7. An in situ real time determination method of black tea drying process aroma dynamic variation as set forth in claim 6 wherein said statistical analysis comprises univariate analysis and multivariate analysis, said multivariate analysis comprises unsupervised analysis and supervised analysis, wherein unsupervised analysis combines moisture change rate and aroma attribute to group samples, and supervised analysis is used to screen VOC markers meeting conditions.
8. 8. The method for in-situ real-time measurement of aroma dynamic change in black tea drying process according to claim 1, wherein a random forest model is constructed based on the VOC (volatile organic compound) marker combination associated with aroma obtained by screening as an aroma discriminating model for discriminating aroma transition in black tea drying process.
9. 9. An application of an in-situ real-time determination method for the dynamic change of the aroma type in the black tea drying process according to any one of claims 1 to 8 is characterized by being applied to distinguishing different stages of aroma type conversion in black tea foot fire drying.
10. 10. An in-situ real-time measurement method for the dynamic change of the aroma of black tea in the drying process according to any one of claims 1 to 8, comprising the following steps: A heating and drying device for drying the sample with a preset fire; And the analyzer is loaded with HPPI-TOFMS and is communicated with the heating and drying equipment space through a stainless steel capillary tube.

Description

In-situ real-time determination method, system and application of fragrance dynamic change in black tea drying process Technical Field The invention relates to the technical field of testing or analyzing materials by means of measuring chemical or physical properties of the materials, in particular to an in-situ real-time measuring method, system and application of the dynamic change of the aroma of black tea in the drying process. Background Tea is taken as one of three beverages in the world and is favored by people around the world. According to different manufacturing processes, the teas can be divided into six different categories, namely green tea, black tea, oolong tea, yellow tea, black tea and white tea. The black tea is full-fermented tea, is the tea with the largest global consumption, has wide influence on the international market, and has continuously increased attention and demand in the market in recent years. Aroma and taste are the most critical attributes in tea quality evaluation, where aroma accounts for about 25% of the total sensory evaluation score, and the proportion in crushed black tea can even be as high as 30%. Tea aroma has various quality characteristics, and common aroma comprises sweet aroma, flower and fruit aroma, caramel aroma and the like by taking black tea as an example. The formation of aroma is greatly affected by the processing technology, and in many processing links, drying is critical to the formation of tea aroma. In the high-temperature drying process of black tea, the volatile matters of the tea are deeply and rapidly converted, are continuously formed and converted through thermochemical reaction, and are dynamically changed along with release, enhancement, attenuation and the like. In the process, the fragrance rapidly evolves, the grass gas gradually disappears, the sweet fragrance, the flower and fruit fragrance, the caramel fragrance and the like gradually appear, and finally, under the combined action of fragrance active substances, the high-quality fragrance quality of the finished tea is molded. Different drying modes, temperatures, time durations and the like can have obvious influence on the change of aroma substances in the tea, for example, unpleasant high fire smell is easily caused by too high drying temperature and too long drying time. At present, moderate judgment of black tea drying and aroma formation mainly depends on smelling of tea makers and on manual experience. Therefore, the method realizes real-time and accurate identification of the flavor transition in the black tea drying process through the modern analysis technology, and has important value for properly and accurately controlling the black tea drying and directionally shaping the flavor quality. In the prior art, the detection of aroma substances of tea leaves mainly depends on gas chromatography-mass spectrometry (GC-MS), and the method has wide application in volatile component analysis, and utilizes means such as solid-phase microextraction or solvent-assisted evaporation to enrich aroma molecules, and then analyzes the aroma molecules through a thermal desorption injection chromatographic system. Although the GC-MS technology is mature and has higher accuracy, the pretreatment process of the sample is more complicated, the detection period is longer, and the analysis result is easily influenced by the pretreatment method of the sample. Particularly in the drying process, the high temperature conditions present a great challenge to sample collection by GC-MS and also present difficulties in accurate assessment of the dynamic conversion of aroma. More importantly, the technology cannot realize real-time, online and in-situ detection at present, the aroma of the tea leaves changes rapidly in the drying stage, the GC-MS cannot realize process synchronous monitoring, and corresponding dynamic spectrogram information cannot be obtained in real time. Disclosure of Invention The invention solves the problems existing in the prior art, and provides an in-situ real-time determination method, a system and application of the dynamic change of the aroma of the black tea in the drying process, which mainly apply HPPI-TOFMS technology, do not need any sample pretreatment, can realize real-time and on-line analysis and detection of various aroma substances in the drying process of the black tea, and realize accurate discrimination of the dynamic change of the aroma. In recent years, online mass spectrometry technology based on soft ionization has been rapidly developed. The high-pressure photoionization-time-of-flight mass spectrometry (HPPI-TOF/MS) can realize in-situ, real-time and on-line monitoring of volatile matters in the tea drying process by virtue of the advantages of high resolution, rapid detection, wide coverage, no need of sample pretreatment and the like. Meanwhile, the soft ionization technology mainly generates molecular ions or excimer ions, is convenient for qualitative an