Processing technology for improving brewing quality of dark green tea through graphene heating film

Abstract

The invention relates to the technical field of tea leaf processing technologies, in particular to a processing technology for improving the brewing quality of dark green tea through a graphene heating film, the graphene heating film is used for heating the dark green tea, then the dark green tea is brewed, when the heating temperature of the graphene heating film is 75 DEG C, the heating time is 30 min, and the heating time is 30 min; according to the processing technology for improving the brewing quality of the dark green tea through the graphene heating film, the tea aroma property of the dark green tea can be effectively improved, the characteristic inclusions of the dark green tea are regulated and controlled, and the quality of the dark green tea is further improved.

Description

Technical Field

[0001] This invention relates to the field of tea brewing technology, specifically to a processing technology for improving the brewing quality of dark tea using a graphene heating film. Background Technology

[0002] The evaluation system for tea quality encompasses five dimensions: appearance, liquor color, taste, aroma, and infused leaf appearance. Among these, taste and aroma are core indicators, directly determining the quality of the finished tea. Tea aroma originates from complex volatile components, including alcohols (such as linalool and cedrol), esters, aldehydes (such as decanal), ketones (such as ionone), and alkenes (such as limonene). Their types and amounts collectively constitute the unique floral, fruity, and woody characteristics of tea, influencing its richness and persistence. Regarding taste, caffeine and catechins are the main sources of bitterness and astringency. Ester-type catechins contribute strong astringency, while non-ester-type catechins impart a sweet aftertaste. Recent studies have shown that the re-firing process can significantly improve the quality of finished tea: by promoting the formation of aldehydes, ketones, and heterocyclic compounds, it effectively reduces stale flavor and enhances woody, floral, and nutty aromas. Traditional reheating techniques include charcoal reheating and microwave reheating: Charcoal reheating can enhance aroma and reduce bitterness, but its outside-to-inside heating method can easily lead to uneven heating and has problems such as high charcoal consumption, carbon smoke pollution, and health risks; Microwave reheating uses penetrating heating to avoid "burnt on the outside and raw on the inside" and is highly efficient, but long-term exposure to the microwave environment may have potential harm to the human body.

[0003] The market demand for dark tea (represented by raw Pu-erh tea) continues to grow. Research shows that heat treatment can reduce the musty smell of dark tea. Given that raw Pu-erh tea retains its grassy characteristics due to the lack of fermentation, further research is needed on the re-firing process for dark tea to fill technological gaps and better develop the quality of dark tea. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by providing a processing technology for improving the brewing quality of dark tea using a graphene heating film. This processing technology can effectively enhance the aroma properties of dark tea and regulate the characteristic contents of dark tea, thereby further improving the quality of dark tea.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The application of graphene heating films in enhancing the aroma of dark tea includes the following steps: The black tea was heated using a graphene heating film, and then brewed. When the heating temperature of the graphene heating film was 75℃, the heating time was 30 minutes.

[0006] In some embodiments, the aroma includes floral and fruity aromas.

[0007] In some embodiments, the aromatic substances include linalool, trans-β-ionone, and decanal, wherein the trans-β-ionone is a key floral fragrance component.

[0008] In some implementations, the concentration of aroma substances decreases when the graphene is heated to a temperature exceeding 30 minutes.

[0009] In some embodiments, the graphene heating film heats the black tea in a sealed environment.

[0010] It also provides the application of graphene heating film in reducing the content of ester-type catechins. The graphene heating film is used to heat black tea, and then the black tea is brewed. When the heating temperature of the graphene heating film is 75℃, the heating time is 20 minutes.

[0011] In some embodiments, the graphene heating film heats the black tea in a sealed environment.

[0012] It also provides the application of graphene heating film in increasing the content of non-ester catechins. Before brewing black tea, when the heating temperature of the graphene heating film is 65℃, the heating time is 20 minutes.

[0013] In some embodiments, the graphene heating film heats the black tea in a sealed environment.

[0014] It also provides the application of graphene heating film in improving the color of black tea soup. The graphene heating film is used to heat the black tea, and then the black tea is brewed. When the heating temperature of the graphene heating film is 65℃, the heating time is 10 minutes.

[0015] The beneficial effects of the processing technology of the graphene heating film of this invention on improving the brewing quality of dark tea are as follows: This invention relates to a processing technology for improving the brewing quality of dark tea using a graphene heating film. Graphene is a high-performance nanomaterial with the characteristic of efficiently converting electrical energy into heat energy. Its heating surface is uniform and stable. The graphene heating film uses far-infrared heating, which can release far-infrared light waves of 6μm~14μm, matching the infrared spectrum wavelength of the human body (2μm~25μm). This invention selects a method to heat dark tea leaves with a graphene heating film before brewing. Specifically, when the heating temperature of the graphene heating film is 75℃ and the heating time is 30 minutes, it can enhance the aroma of dark tea; when the heating temperature of the graphene heating film is 75℃ and the heating time is 20 minutes, it can reduce the content of ester-type catechins; and when the heating temperature of the graphene heating film is 65℃ and the heating time is 20 minutes, it can increase the content of non-ester-type catechins. Attached Figure Description

[0016] Figure 1This includes a radar chart of sensory evaluation scores and differences in the dry weight of biochemical components among different combinations. (A2) Sensory evaluation score radar chart of dark tea; (B2) Biochemical component content of dark tea. The letters on the bars represent the significance level, where uppercase letters indicate differences in treatment time within the same grade, and lowercase letters indicate differences between different grades within the same treatment time. Error bars represent Mean ± SD, and the letters (A, B, C, a, b, c) indicate the differences obtained according to the Turkey HSD comparison method (p < 0.05), n = 3.

[0017] Figure 2 This study analyzes the effects of different treatment times and settings of the graphene heating film on the changes in volatile substances in dark tea from different perspectives. (A2) represents the total concentration of volatile substances in oolong and dark tea under different treatments with the graphene heating film; (B2) represents the concentration changes of different categories of volatile substances; (C2) represents the quantity changes of different categories of volatile substances; and (D2) represents the concentration changes of the nine volatile substances with the highest concentrations detected. The letters on the bars represent the significance level, where uppercase letters indicate differences in treatment times at the same setting, and lowercase letters indicate differences between different settings at the same treatment time. Error bars represent Mean ± SD, and the letters (A, B, C, a, b, c) represent the differences obtained according to the Turkey HSD comparison method (p < 0.05), n = 3.

[0018] Figure 3 This is a multivariate statistical analysis of the volatile components of dark tea under different temperature settings and time treatments with a graphene heating film. (D) PLS-DA score plot of volatile components of dark tea; (E) Cross-validation results: The intercept of the Q2 response line of the cross-validation model after 200 comparisons is less than 0, indicating that the PLS-DA discriminant model is not overfitted and the model is relatively reliable; (F) VIP score plot: Pink bars represent volatile compounds with VIP>1; blue bars represent volatile compounds with VIP<1.

[0019] Figure 4 The chart shows: B) Radar plot of aroma and flavor of dark tea under different treatments; D) Concentration of potential key aroma compounds in dark tea under different treatments; F) Heatmap of changes in volatile compound concentrations in dark tea under different treatments. The letters on the bars represent significance levels, with uppercase letters indicating differences between different treatment times within the same treatment level, and lowercase letters indicating differences between different treatment levels within the same treatment time. Error bars represent Mean ± SD, and the letters (A, B, C, a, b, c) indicate differences obtained using the Turkey HSD comparison method (p < 0.05), n = 3. Detailed Implementation

[0020] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0021] Example 1 The dark tea sample used in this experiment was Pu'er tea (2022 Mansong raw Pu'er, Kunming Tianhong Tea Industry, Yunnan Province). Heating was performed on two dark tea samples using a graphene heating film (Shenzhen Zhaojian Technology Co., Ltd.) at medium (65℃, M) and high (75℃, H) power levels. A 0-minute time interval was used as the control, and time gradients of 10, 20, and 30 minutes were established. The corresponding numbers are: control (CK), medium-power treatment for 10 minutes (M10), medium-power treatment for 20 minutes (M20), medium-power treatment for 30 minutes (M30), high-power treatment for 10 minutes (H10), high-power treatment for 20 minutes (H20), and high-power treatment for 30 minutes (H30). Part of the tea was preserved for sensory evaluation, and the rest was ground into tea powder and preserved for the determination of volatile compounds, catechins, and caffeine.

[0022] The impact of heat treatment on sensory evaluation Regarding the color of the tea liquor, the color of all black teas gradually deepened with increasing heating, and the clarity of the tea liquor decreased with increasing heating time. Among the black teas, M10 scored the highest in liquor color at 89 points, 1.13% higher than the control (CK). The flavor scores of all black teas decreased after heating. It is evident that with increasing heating, the grassy aroma of black tea gradually disappeared, and a woody aroma appeared. The aroma score was highest at H30, at 92 points, 4.5% higher than the control (CK). Figure 1 A2, S Table 1).

[0023] Compared with CK, there were no significant differences in catechins among black teas at the same grade; however, the catechin content of black tea H20 was significantly lower than that of M20.

[0024] At the same time point, the content of ester-type catechins (GCG, EGCG) in dark tea changed significantly after 20 minutes of heating. Compared to M20, the contents of GCG and EGCG decreased by 7.9% and 8.7%, respectively, at H20. At H20, there was no significant difference in the GC and EC contents of dark tea. However, at M20, the GC and EC contents of dark tea were highest, and GC at M20 was significantly higher than at H20. GC and EC increased by 13.3% and 16.5%, respectively, compared to the control (CK). There were no significant differences in EGC and C contents of dark tea at the same heating level or time. Figure 1 B2).

[0025] In summary, the content of ester-type catechins in dark tea decreases at H2O and increases at M2O. Combined with the sensory evaluation results, it can be seen that, at the same level, as the heating time increases, the bitterness and astringency of dark tea intensifies and the aftertaste weakens (Table 1).

[0026] Changes in volatile substances The effect of graphene heating film on the aroma of dark tea samples The volatile substances in black tea processed with graphene heating film were detected using GC-MS. A total of 31 volatile substances were identified in the black tea. Among the identified volatile substances, there were 8 alcohols, 6 esters, 3 aldehydes, 2 alkenes, 5 ketones, and 7 other volatile substances.

[0027] In the identification of volatile substance concentration, H10 showed a slight increase in the total volatile substance concentration in dark tea, but the increase was not significant (12.10%). The other treatments did not increase the total volatile substance concentration in dark tea, but rather showed varying degrees of decrease, with M30 producing the most significant decrease (59.55%). Figure 2 A2).

[0028] The graphene heating film significantly affected the types, quantities, and concentrations of volatile substances in dark tea. The changes in the concentrations of various volatile substances in dark tea after different treatments followed a similar pattern to the changes in the total concentration. In M20, the concentrations of esters and ketones increased by 4.03% and 20.09%, respectively; in H30, the concentrations of alcohols, esters, and ketones increased by 1.76%, 4.81%, and 22.07%, respectively. Under other treatments, the concentrations of all substances in dark tea decreased.

[0029] Qualitatively, compared with the control, more volatile substances were detected in black tea M30, H10, H20, and H30. The number of alcohols and esters increased by one in each of these treatments compared to the control. Figure 2 C2).

[0030] Nine volatile compounds with the highest concentrations in dark tea were selected for further analysis to more intuitively observe their dynamic changes during graphene heating film treatment. In dark tea, only at H30 did the concentrations of Methylsalicylate, trans-Linalool oxide (furanoid), and trans-β-Ionone show a significant increase compared to the control (CK). Other treatments did not significantly increase the concentrations of the selected nine volatile compounds; some even caused a decrease in their concentrations. Overall, for the aroma of dark tea, enhancing the aroma may require H30 or even longer.

[0031] Analysis of Aroma Types in Dark Tea After Processing with Graphene Heating Film Further classification of the identified volatile substances by aroma type was performed. Based on their aroma, these volatile substances can be broadly categorized into floral, fruity, green, toasty, and woody aromas. The total concentrations of the volatile metabolites in these five clearly defined aroma types were summed to create an aroma-flavor radar chart. Figure 4 B). Dark tea, on the other hand, exhibits more prominent floral and fruity aromas. According to the radar chart, the total concentrations of floral and fruity aromas in dark tea peaked during the H30 treatment. In conclusion, the H30 treatment is crucial for enhancing the overall aroma of dark tea.

[0032] Identification and analysis of characteristic aromas in different types of tea after processing with graphene heating films To further identify and analyze the characteristic volatile components of dark tea processed by graphene heating films, PLS-DA models were constructed based on 31 volatile compounds (in dark tea). PLS-DA analysis of volatile substances in two different types of tea after different treatments with graphene heating films was performed. The models constructed for both types of tea showed appropriate predictability and no overfitting. Figure 3 E). Looking at specific tea types, in dark tea, the 10 volatile components with a VIP > 1 include 3 alcohols, 1 ketone, 3 esters, 1 aldehyde, and 2 other volatile components (…). Figure 3 F).

[0033] The contribution of volatile compounds to the overall aroma is related to their concentration and odor activity value (OAV), which refers to the minimum concentration at which a compound has a perceptible odor. Volatile components that meet the criteria of VIP>1 and OAV≥1 and have been identified as aroma compounds are selected as potential key aroma compounds.

[0034] Similarly, six aroma components were identified in dark tea treated with different temperature settings and processing times using a graphene heating film, including four floral, one fruity, and one grassy aroma. Three of these met the criteria for potential key aroma compounds during the graphene heating film processing: Linalool, trans-beta-Ionone, and Decanal. The results showed that H30 significantly enhanced the floral aroma of dark tea. However, no significant fruity aroma (decanal) was detected in the medium-temperature treatments (M10, M20, and M30).

[0035] Table 1. Six aroma components identified in dark tea

[0036] Changes in characteristic aroma of dark tea during graphene heating film processing Potential key aroma compounds were identified using the above analytical methods, and the changes of these compounds under different settings and time periods of treatment with the graphene heating film were further analyzed. Figure 4 This study demonstrates the concentration changes of key potential aroma compounds in dark tea under different treatments. These trends are generally consistent with the OAV value trends of the aforementioned characteristic aroma compounds.

[0037] After treatments M10 and M30, the concentrations of all characteristic aroma compounds in dark tea decreased; after treatment M20, the concentration of trans-beta-Ionone increased to some extent. In the higher-grade treatments, only H30 significantly increased the concentration of trans-beta-Ionone in dark tea; other treatments (H10, H20) showed a decrease or no significant change in the concentration of characteristic aroma compounds. In conclusion, for dark tea, treatment H30 provides the best overall performance in terms of characteristic aroma compounds. Figure 4 D).

[0038] H30 treatment significantly increased the content of trans-beta-Ionone, a floral compound that is a key potential aroma component in dark tea.

[0039] For dark tea, the concentration of most aroma compounds is increased at H30; a very small number of aroma compounds are increased at M20 or H10; while the remaining treatments actually decrease the concentration of aroma compounds in dark tea. The variation pattern of aroma compound concentration is basically consistent with the aforementioned trend.

[0040] The effects of graphene heating films on different types of tea vary. Their effects on liquor color and flavor intensity are similar: the liquor color deepens and the flavor intensity increases with increasing heating intensity. However, their effects on aroma differ. For dark tea, they primarily eliminate the grassy aroma and enhance the woody fragrance. Biochemical analysis shows no significant difference in caffeine content among dark teas, regardless of heating intensity or time. Except for H2O (dark tea), the total catechin monomer content also shows no significant difference. However, heating promotes changes in the content of ester-type and non-ester-type catechins. Dark tea shows a decrease in ester-type catechin content at H2O and an increase in non-ester-type catechin content at M2O. Based on the sensory evaluation results, it can be seen that, at the same level, as the heating time increases, the bitterness and astringency of the dark tea flavor intensifies and the aftertaste weakens. On the one hand, this may be because heating increases the leaching rate of substances contained in the tea leaves, resulting in an increase in the intensity of the tea soup flavor and an intensification of bitterness and astringency. This may also be the reason why the tea soup becomes cloudy when the heating intensity is high (M30, H10, H20, H30) (Table 1).

[0041] For volatile substances in tea, graphene heating film treatment has a significant impact on aroma compounds. After heating with a graphene heating film, the variety of aroma compounds in tea increases, and the relative content of some major aroma compounds is also significantly improved. For dark tea, the effect of graphene heating film on the aroma of tea samples is relatively subtle, with a significant improvement only observed at H30.

[0042] Under the same heating time, there was no significant difference in the effects of medium and high heating on the biochemical components of black tea, such as caffeine and catechins. However, under the same heating level, different heating times showed more or less significant differences in the effects on the biochemical components of tea. Figure 1 (B2). In the sensory evaluation results, under the same heating time but different heating levels, the aroma scores of tea were similar, while under the same heating level but different heating times, the aroma of tea generally showed an upward trend (Table 1). Therefore, it can be inferred that the heating level of this graphene heating film has less impact on the taste and aroma of black tea than the heating time.

[0043] In conclusion, to enhance the aroma of tea, applying a high-grade treatment to dark tea for 30 minutes can increase the content of potential key aroma compounds, particularly enhancing the floral compounds Linalool and trans-β-Ionone. The results of non-volatile substance testing and sensory evaluation suggest that the graphene heating film improves the extraction rate of tea leaves. The volatile substance testing results indicate that the graphene heating film helps enhance the aroma of tea. Based on these conclusions, it can be inferred that applying the graphene heating film to some milder teas such as green tea and white tea may yield even better results, enhancing both aroma and the strength of the tea liquor, thereby improving the overall quality of the tea.

[0044] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of graphene heating film in improving the aroma of dark tea, characterized in that, The method comprises the following steps: The black tea is heated by the graphene heating film, and then the black tea is brewed, wherein the heating temperature of the graphene heating film is 75 DEG C, and the heating time is 30 min.

2. The use of graphene heating film in enhancing the aroma of black tea according to claim 1, characterized in that, The aroma includes flower aroma and fruit aroma.

3. The use of graphene heating film in enhancing the aroma of black tea according to claim 2, characterized in that, The aroma substance includes linalool, trans-beta-ionone and decanal, wherein the trans-beta-ionone is a flower aroma key substance.

4. The use of the graphene heating film according to claim 1 in improving the aroma of black tea, characterized in that, When the graphene heating time is more than 30 min, the aroma substance concentration decreases.

5. The use of the graphene heating film according to claim 1 in improving the aroma of black tea, characterized in that, The graphene heating film heats the black tea in a sealed environment.

6. Use of a graphene heating film for reducing the content of ester-type catechins, characterized in that, The black tea is heated by the graphene heating film, and then the black tea is brewed, wherein the heating temperature of the graphene heating film is 75 DEG C, and the heating time is 20 min.

7. Use of a graphene heating film according to claim 7 to reduce ester-type catechin content, characterized by, The graphene heating film heats the black tea in a sealed environment.

8. Use of graphene heating film for increasing the content of non-ester catechins, characterized by, The black tea is heated by the graphene heating film, and then the black tea is brewed, wherein the heating temperature of the graphene heating film is 65 DEG C, and the heating time is 20 min before the black tea leaves are brewed.

9. Use of a graphene heating film according to claim 8 to increase the non-ester catechin content, characterized in that, The graphene heating film heats the black tea in a sealed environment.

10. Use of graphene heating film in improving the color of black tea soup, characterized in that, The black tea is heated by the graphene heating film, and then the black tea is brewed, wherein the heating temperature of the graphene heating film is 65 DEG C, and the heating time is 10 min.

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