Microcapsule for stabilizing Wuyi rock tea volatile oil

Abstract

The invention provides a microcapsule for stabilizing Wuyi rock tea volatile oil, which is prepared by the following steps: (1) stirring and mixing Wuyi rock tea volatile oil and medium chain triglyceride oil to obtain an oil phase, and (2) dissolving Arabic gum in water to obtain a water phase; and (3) adding the oil phase into the water phase, shearing, adding gelatin, carrying out complex coacervation reaction, cooling in an ice bath, adding tea polyphenol, and carrying out curing cross-linking and phase separation to obtain the Wuyi rock tea volatile oil microcapsule. According to the microencapsulation method for the Wuyi rock tea volatile oil, the loss and damage of heat-sensitive aroma components are reduced to the greatest extent by adopting a relatively low reaction temperature and a vacuum freeze drying technology, and the rock charm characteristic of the Wuyi rock tea is perfectly reserved. The microcapsule prepared by the method disclosed by the invention is high in embedding rate, the product is powder with good fluidity, the microcapsule can be widely applied to solid beverages, cakes, candies, health care product capsules, toothpaste, skin care products and other daily chemical products, and the development path of Wuyi rock tea high-added-value products is expanded.

Description

Technical Field

[0001] This invention belongs to the field of oil preservation technology, specifically relating to a microcapsule for preserving the characteristic aroma volatile oil of Wuyi rock tea. Background Technology

[0002] Wuyi Rock Tea (such as Da Hong Pao, Rou Gui, and Shui Xian) is a unique and high-quality oolong tea in China. Its distinctive "rocky charm" and rich, long-lasting, multi-layered aroma are loved by consumers. This characteristic aroma mainly comes from the volatile oil components in tea leaves, including aldehydes, alcohols, esters, ketones, and nitrogen-containing compounds (HU Tenfei, XIAO Han, XIE He, et al. Analysis of Key Aroma Compounds in Three Varieties of Wuyi Rock Tea Based on GC×GC-TOFMS-O[J]. Modern Food Science & Technology, 2024, 40(06): 221-230.). However, these volatile oil components are highly volatile and sensitive to light, heat, and oxygen. They are easily lost or deteriorated during processing, storage, and transportation, resulting in weakened aroma intensity and deteriorated quality. This severely limits their widespread application in food flavoring, deep processing of tea beverages, and daily chemical fragrances (DUAN Y, GAOX, SHI BL, et al. Characterize the dynamic changes of volatile compounds during the roasting process of Wuyi rock tea (Shuixian) integrating GC-IMS and GC × GC-O-MS combined with machine learning[J]. Food Chemistry, 2025,489:144931.).

[0003] Microencapsulation technology is a technique that encapsulates solid, liquid, or gaseous substances within polymeric wall materials to form tiny particles. This effectively protects the core material from external environmental factors, controls its release rate, and improves stability. Currently, commonly used microencapsulation methods such as spray drying and composite coagulation are applied to the encapsulation of essential oils from citrus fruits and peppermint. However, conventional wall materials (such as maltodextrin alone) are not highly efficient at encapsulating the complex polar and non-polar components in the volatile oils of Wuyi rock tea, easily leading to low encapsulation rates and easy oxidation of the product. Furthermore, the high temperatures during spray drying may damage heat-sensitive aroma components, altering their original aroma profile and causing them to lose their "rocky" characteristics. Therefore, developing a microencapsulation method that can efficiently encapsulate, maximize the preservation of the characteristic aroma of Wuyi rock tea, and possess good storage stability and controllable release has significant industrial value. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to propose a microcapsule for stabilizing the volatile oil of Wuyi rock tea, thereby microencapsulating the volatile oil of Wuyi rock tea. This microencapsulation method has high encapsulation efficiency, effectively protects the characteristic aroma components of Wuyi rock tea volatile oil, and the resulting microcapsule product exhibits good stability.

[0005] The technical solution for achieving the above-mentioned objective of this invention is as follows: Microcapsules stabilizing the volatile oil of Wuyi rock tea were prepared by the following steps: (1) The volatile oil of Wuyi rock tea and MCT oil (medium-chain triglyceride oil) were stirred and mixed to obtain the oil phase; (2) Gum arabic dissolves in water to form an aqueous phase; (3) The oil phase was added to the aqueous phase, sheared, gelatin was added and a coagulation reaction was carried out. After cooling in an ice bath, tea polyphenols were added for solidification, crosslinking and phase separation to obtain Wuyi rock tea volatile oil microcapsules.

[0006] Currently, the main industrial methods for extracting volatile oils from tea include steam distillation, supercritical fluid extraction, and simultaneous distillation-extraction. Simultaneous distillation-extraction combines steam distillation and solvent extraction, resulting in an extract that does not contain non-volatile components, thus achieving better separation and making it suitable for extracting volatile oil components.

[0007] The volatile oil of Wuyi rock tea is obtained by simultaneous distillation and extraction, which is a method that combines steam distillation and solvent extraction, and the solvent is dichloromethane.

[0008] Further, the operation of the simultaneous distillation extraction method is as follows: take Wuyi rock tea powder, add it to water, heat to boiling and maintain for 25-40 min; at the same time, heat dichloromethane to boiling, collect the volatile oil with dichloromethane under gaseous conditions, cool to obtain a dichloromethane solution of volatile oil (distillate); evaporate to remove the solvent to obtain Wuyi rock tea volatile oil.

[0009] The dichloromethane solution (distillate) of volatile oil can be dried with anhydrous sodium sulfate first, and then the solvent can be removed by rotary evaporation.

[0010] In this process, 0.1-1% gelatin and 0.1-1% gum arabic solutions are prepared respectively. In step (2), the volatile oil of Wuyi rock tea is dissolved in MCT oil and then added to the gum arabic solution.

[0011] The volume ratio of the gelatin solution to the gum arabic solution is 1:0.8~1.2.

[0012] In step (3), the shearing rate is 5000~15000 rpm and the shearing time is 5~15 min.

[0013] Preferably, in step (3), the re-coagulation reaction after adding the gelatin solution is carried out at pH 4.0~4.5 and temperature 38~40℃, and the phase separation process is carried out at 2~6℃.

[0014] More preferably, the complex coagulation reaction is carried out at pH 4.3. All other steps can be performed at room temperature. The pH can be adjusted using acetic acid, citric acid, phosphoric acid, or other acids known in the art.

[0015] Further, in step (3), after cooling in an ice bath for 30 min, a tea polyphenol solution with a mass concentration of 5-10% is added for curing and crosslinking, and crosslinking is carried out at room temperature for 1-3 h; the volume of the tea polyphenol solution is 5-8% of the volume of the gelatin solution, and the pH of the tea polyphenol solution is adjusted to 4.0-4.5.

[0016] The tea polyphenol solution can be a tea polyphenol solution with pH 4.3 prepared for direct use, or it can be an oxidized tea polyphenol solution obtained by adjusting the pH to 9.0 and oxidizing for 1-12 hours after preparing the tea polyphenol solution; there is no significant difference in the encapsulation rate of microcapsules between tea polyphenols and oxidized tea polyphenols.

[0017] A preferred embodiment of the present invention is that the mass ratio of Wuyi rock tea volatile oil, medium-chain triglyceride oil (MCT oil), gelatin, gum arabic and tea polyphenols is 1:(4~5):(5~6):(5~6):(3~4).

[0018] In step (3), the time for the complex condensation reaction is 10-30 min, and the time for the ice bath cooling is 30-60 min.

[0019] The beneficial effects of this invention are as follows: The microcapsules for stabilizing the volatile oil of Wuyi rock tea proposed in this invention utilize a ternary composite wall material of gelatin, gum arabic, and tea polyphenols. Gelatin and gum arabic possess excellent emulsifying and film-forming properties; simultaneously, the complex coagulation reaction between the two forms the basis of the microcapsule shell, and the tea polyphenols further strengthen the shell by cross-linking with the gelatin-gum arabic complex coagulation layer. The synergistic effect of these three components achieves highly efficient and tightly sealed encapsulation of the volatile oil of Wuyi rock tea.

[0020] The present invention provides a microencapsulation method for the volatile oil of Wuyi rock tea. By employing a lower reaction temperature and vacuum freeze-drying technology, the loss and damage of heat-sensitive aroma components are minimized, thus perfectly preserving the "rocky charm" characteristics of Wuyi rock tea.

[0021] The microcapsules prepared by the method of this invention have a high encapsulation rate and the product is a powder with good flowability. It can be widely used in solid beverages, pastries, candies, health product capsules, as well as daily chemical products such as toothpaste and skin care products, thus expanding the development path of high value-added products of Wuyi rock tea. Attached Figure Description

[0022] Figure 1 The diagram shows the process flow chart for Wuyi Rock Tea volatile oil microcapsules.

[0023] Figure 2 The figure shown illustrates the effect of the ratio of gelatin and gum arabic on the complex coagulation system.

[0024] Figure 3 The effect of pH on complex condensation systems is shown.

[0025] Figure 4 The effect of different curing agents on the encapsulation efficiency of microcapsules. Note: Figure 4 The MCT-NOM, MCT-TPM, and MCT-OPM that appeared in the middle and later represent MCT oil microcapsules prepared without added tea polyphenols, with added tea polyphenols, and with added oxidized tea polyphenols, respectively; E0-NOM, EO-TPM, and EO-OPM represent Wuyi rock tea volatile oil microcapsules prepared without added tea polyphenols, with added tea polyphenols, and with added oxidized tea polyphenols, respectively.

[0026] Figure 5 The effect of different curing agents on microcapsule particle size is shown.

[0027] Figure 6 The structure of cross-linked microcapsules with different curing agents is shown under a scanning electron microscope.

[0028] Figure 7 Thermogravimetric curves of volatile oil from Wuyi rock tea and its microcapsules.

[0029] Note: Figure 7 The EO-MCT mentioned earlier and later represents the volatile oil of Wuyi rock tea dissolved in MCT oil.

[0030] Figure 8 Thermogravimetric differential curves of volatile oil from Wuyi rock tea and its microcapsules.

[0031] Figure 9 Electronic nose radar image of volatile oil and its microcapsules from Wuyi rock tea.

[0032] Note: E0-NOM-100℃, EO-TPM-100℃, and EO-OPM-100℃ appearing in the figure and thereafter represent Wuyi rock tea volatile oil microcapsules prepared after 30 min of pretreatment at 100℃ with no added tea polyphenols, added tea polyphenols, and added oxidized tea polyphenols, respectively.

[0033] Figure 10 Principal component analysis diagram of volatile oil from Wuyi rock tea and its microcapsules via electronic nose.

[0034] Figure 11 This is a device for simultaneous distillation and extraction of volatile oils from Wuyi rock tea. In the diagram, 1 is a flask containing Wuyi rock tea, 2 is a solvent bottle, 3 is a collection bottle, 4 is a condenser, 41 is a condensate outlet, and 42 is a condensate inlet. Detailed Implementation

[0035] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all methods used in this specification are existing techniques in the field.

[0037] In a specific implementation, the method for detecting the microcapsule encapsulation efficiency is as follows: 1) Detection of MCT oil encapsulation rate: The microcapsule powder was completely immersed in petroleum ether, filtered, and the filtrate was collected in a pre-weighed beaker. The petroleum ether in the filtrate was evaporated under a 60°C water bath. Finally, it was dried in an oven at 105°C to constant weight. After cooling, it was weighed to calculate the surface oil content. The microcapsule powder was completely immersed in ammonia, methanol, anhydrous diethyl ether and petroleum ether in sequence and vortexed to mix. The filtrate was filtered and collected in a pre-weighed beaker. The organic reagent in the filtrate was evaporated under a 60°C water bath. Finally, it was dried in an oven at 105°C to constant weight. After cooling, it was weighed to calculate the total oil content. The encapsulation rate was calculated according to formula (1).

[0038] (1) In the formula: w represents the MCT oil encapsulation rate, %; m1 represents the surface oil content of the MCT oil microcapsules, %; m2 represents the total oil content of the MCT oil microcapsules, %.

[0039] 2) Determination of the embedding rate of volatile oil in Wuyi rock tea: A solution of volatile oil in Wuyi rock tea and anhydrous ethanol was prepared, and the maximum absorption wavelength (272 nm) was determined by scanning at wavelengths between 200 and 400 nm. A series of concentrations of volatile oil in Wuyi rock tea and anhydrous ethanol solutions were prepared, and the absorbance of all solutions was measured at 272 nm. Plotting absorbance on the ordinate and the concentration of the volatile oil in the solution on the abscissa, the regression equation for the standard curve of the volatile oil solution was obtained as: y = 1.2271x + 0.0821, R0 2 =0.992.

[0040] Accurately weigh different microcapsule powders and add them to anhydrous ethanol. Centrifuge and collect the supernatant. Measure the absorbance at 272 nm. Accurately weigh different microcapsule powders and add them to anhydrous ethanol. Sonicate to completely break them up. Centrifuge and collect the supernatant. Measure the absorbance at 272 nm. Calculate the surface oil and total oil content based on the drawn standard curve of volatile oil-anhydrous ethanol for Wuyi rock tea and the dilution factor. Calculate the encapsulation rate according to formula (2).

[0041] (2)

[0043] In the formula: W represents the encapsulation rate of volatile oil in Wuyi rock tea, %; M1 represents the surface oil content of volatile oil microcapsules of Wuyi rock tea, μL / g; M2 represents the total oil content of volatile oil microcapsules of Wuyi rock tea, μL / g.

[0044] Example 1: Extraction of volatile oil from Wuyi rock tea Meanwhile, the distillation and extraction equipment was assembled in-house by our laboratory; its structure is shown in [see details]. Figure 11 A cooling device 4 is installed in the middle of the pipeline connecting the flask 1 containing Wuyi rock tea and the solvent bottle 2. The cooling device 4 has a condensate outlet 41 and a condensate inlet 42, which ensure that the condensate level is lower than the top. The device must be kept airtight during the extraction process. The interfaces between the two flasks and the upper pipeline, as well as the interface between the collection bottle and the condensate pipeline, must be sealed. Ground glass joints or other sealing methods known in the art can be used.

[0045] The extraction process for volatile oil from Wuyi rock tea is as follows: The flask 1 containing Wuyi rock tea is heated by an electric heating mantle, and the steam carries the volatile oil of the tea upwards; the solvent bottle 2 is also heated at the same time, and the solvent dichloromethane vaporizes and rises. The two vapors mix at the top of the cooling device 4, and the dichloromethane absorbs the volatile oil under gaseous conditions; circulating cooling water is introduced below the top of the cooling device 4 through the condensate outlet 41 and the condensate inlet 42 to cool the steam, so that the volatile oil dichloromethane solution liquefies and enters the collection bottle 3.

[0046] In this embodiment, 100 g of Da Hong Pao Wuyi Rock Tea powder was added to 800 mL of distilled water and heated to a boil. Then, 30 mL of dichloromethane was added to solvent bottle 2, and the mixture was heated in a water bath at 60°C. After the contents of both flasks boiled, the mixture was kept at a constant temperature for 30 minutes to allow the volatile oils to accumulate in the dichloromethane.

[0047] The volatile oil dichloromethane solution was collected, dried with anhydrous sodium sulfate to remove moisture, and then the dichloromethane was removed by rotary evaporation at 45°C. The solution was then concentrated to obtain the volatile oil of Wuyi rock tea.

[0048] Example 2: Complex Coagulation Condition Test Through preliminary research, the inventors determined to use the complex coagulation reaction between gelatin and gum arabic to prepare microcapsules, and first used the microcapsules to encapsulate MCT oil in order to optimize the complex coagulation conditions in the preparation of microcapsules.

[0049] Prepare solutions of gelatin and gum arabic with a mass concentration of 0.1%, adjust the pH to 4.0 with 10% acetic acid solution, and mix them in mass ratios of 8:1, 6:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:6, and 1:8. Measure the absorbance at 600 nm. Prepare 0.1% solutions of gelatin and gum arabic, respectively. Add the gum arabic solution to the gelatin solution at a certain ratio, adjust the pH at 0.1 intervals, and take samples. Measure the absorbance at 600 nm.

[0050] The relationship between the coagulation reaction of gelatin and gum arabic and their ratio and pH is as follows: Figure 2 As shown, the coagulation reaction is most vigorous when the ratio of gelatin to gum arabic is 1:1. (See also...) Figure 3 As the mixing ratio of gelatin and gum arabic increased from 1:2 to 2:1, the highest turbidity shifted towards a higher pH value. This is because the complex coagulation reaction mainly relies on the neutralization of the positive charge of gelatin and the negative charge of gum arabic. With an increased proportion of gelatin, more H+ ions are needed to protonate the gelatin, reducing its positive charge density, thus increasing the pH at which the highest turbidity occurs. Therefore, pH 4.3 was determined to be the suitable pH value. Under suitable gelatin ratios and pH conditions, the emulsion particles change their charged state, undergoing a charge neutralization reaction to form aggregates.

[0051] Example 3: Preparation of microcapsules encapsulating MCT oil Prepare solutions of 1% gelatin and 1% gum arabic by mass, respectively, and stir magnetically until completely dissolved to obtain wall material solutions.

[0052] The volatile oil and medium-chain triglyceride oil of Wuyi rock tea were mixed at a volume ratio of 1:4 to obtain the oil phase. The oil phase was then added to the gum arabic solution and gelatin solution, stirred evenly at room temperature, and sheared at 10,000 r / min for 10 min to obtain a homogeneous emulsion.

[0053] The pH of the solution was adjusted to 4.3 with 10% acetic acid solution, reacted at 40℃ for 30 min, cooled in an ice bath for 30 min, and then crosslinked at room temperature for 1 h.

[0054] The cross-linked solution was placed in a 4°C refrigerator and allowed to stand for 1 hour to separate the phases. The precipitate was taken as MCT oil microcapsules, which were then freeze-dried under vacuum to obtain microcapsule powder.

[0055] The inventors first experimented with mixing gum arabic solution and gelatin solution before adding MCT. Adding the gum arabic solution and gelatin solution together resulted in microcapsules with poor shape. Another experiment involved adding the gum arabic solution and the gelatin solution separately; since the emulsion depends on the emulsifying properties of gum arabic, the gelatin was added later. The resulting microcapsules were essentially spherical.

[0056] Example 4: Preparation of microcapsules encapsulating volatile oils from Wuyi rock tea (1) Dissolve the volatile oil of Wuyi rock tea in MCT oil and stir to obtain the oil phase; the volume ratio of the two is 1:4; Prepare solutions of 1% gelatin, 1% gum arabic, and 10% tea polyphenols by mass, respectively, and stir magnetically until completely dissolved to obtain wall material solutions.

[0057] (2) Take 1 mL of oil phase and add it to 100 mL of gum arabic solution. Stir evenly at room temperature and shear at 10000 r / min for 10 min to obtain a uniform emulsion.

[0058] (3) Add 100 mL of gelatin solution to the emulsion obtained in step (2), adjust the pH of the solution to 4.3, react at 40℃ for 30 min, cool in an ice bath for 30 min, and then crosslink at room temperature for 1 h.

[0059] The cross-linked solution was placed in a 4°C refrigerator and allowed to stand for 1 hour for phase separation. The precipitate was taken as Wuyi rock tea volatile oil microcapsules, which were then vacuum freeze-dried and stored to obtain a reddish-brown microcapsule powder with a tea aroma.

[0060] See Figure 4Encapsulation efficiency testing showed that microcapsules prepared using the complex coagulation reaction between gelatin and gum arabic could be used for encapsulating MCT oil, achieving an encapsulation efficiency of 85.73% without the need for additional curing agents. Furthermore, the stability of MCT oil allows it to be used to construct stable transport carriers for unstable substances. However, the encapsulation efficiency of Wuyi rock tea volatile oil microcapsules constructed using MCT oil as a carrier was only 43.14%. Therefore, further investigation was conducted to solidify the shell of the complex coagulated microcapsules using the cross-linking effect of tea polyphenols.

[0061] Example 5: Preparation of microcapsules encapsulating volatile oils from Wuyi rock tea Microcapsules were tested with no tea polyphenols, with tea polyphenol solution (prepared as a 10% tea polyphenol solution, adjusted to pH 4.3), and with oxidized tea polyphenol solution (prepared as a 10% tea polyphenol solution, completely dissolved, adjusted to pH 9.0, oxidized at room temperature with aeration and stirring for 12 hours, and then adjusted to pH 4.3 with 10% acetic acid solution). The basic operation is the same as in Example 4, except that step (3) is: (3) Add 100 mL of gelatin solution to the emulsion obtained in step (2), adjust the pH of the solution to 4.3, add the oil phase, react at 40℃ for 30 min, cool in an ice bath for 30 min, add 6 mL of 10% tea polyphenol solution or oxidized tea polyphenol solution, and crosslink at room temperature for 1 h.

[0062] The cross-linked solution was placed in a 4°C refrigerator for phase separation for 1 h. The precipitate was taken as Wuyi rock tea volatile oil microcapsules, which were then vacuum freeze-dried and stored to obtain reddish-brown microcapsule powder with a tea aroma.

[0063] See results Figure 4 Only after solidification with tea polyphenols can volatile oils be effectively encapsulated within the microcapsules, maintaining a high total oil content. The addition of tea polyphenols and the oxidation of tea polyphenols did not produce a significant difference in encapsulation efficiency. This indicates that the oxidation of tea polyphenols does not affect the encapsulation effect of the microcapsules, providing a basis for the storage stability of these microcapsules.

[0064] Physicochemical testing: 1) Particle size The particle size distribution of MCT oil and volatile oil microcapsules is as follows: Figure 5 As shown in the table below, the average particle sizes of MCT oil and volatile oil microcapsules without added tea polyphenols were 46.27 μm and 20.10 μm, respectively. However, the average particle sizes increased to some extent after adding tea polyphenols. This may be because the tea polyphenols and the gelatin on the surface of the microcapsules cross-linked, making the shell of the microcapsules thicker.

[0065] Table 1 Effects of different curing agents on microcapsule D 10 D 50 and D 90 Impact

[0066] In the table, MCT-NOM, MCT-TPM, and MCT-OPM represent MCT oil microcapsules prepared with no added tea polyphenols, with added tea polyphenols, and with added oxidized tea polyphenols, respectively; E0-NOM, EO-TPM, and EO-OPM represent Wuyi rock tea volatile oil microcapsules prepared with no added tea polyphenols, with added tea polyphenols, and with added oxidized tea polyphenols, respectively.

[0067] 2) Micromorphology See Figure 6 Under SEM, it can be seen that the microcapsules without added tea polyphenols are severely adhered to each other. This is because the coagulation reaction occurs between gelatin and gum arabic, which is difficult to control in the whole reaction system. The addition of tea polyphenols causes the gelatin and tea polyphenols on the surface of the microcapsules to react, which breaks the weak crosslinks that were originally formed between the microcapsules by the coagulation reaction, thus allowing the microcapsule particles to be in a dispersed state.

[0068] 3) Thermal stability Figure 7 and Figure 8 The thermogravimetric (TGA) curves and thermogravimetric differential (TGC) curves of Wuyi Rock Tea volatile oil, a mixture of Wuyi Rock Tea volatile oil and MCT oil, and microcapsules of Wuyi Rock Tea volatile oil with no added tea polyphenols, added tea polyphenols, and added oxidized tea polyphenols are shown. The figures reveal that Wuyi Rock Tea volatile oil begins to volatilize at room temperature, rapidly decreases in mass between 35 and 300°C, and exhibits the fastest rate of heat loss at 40°C. Mixing with MCT oil inhibits its volatilization at room temperature and, to some extent, slows down the rapid mass loss to the 250–350°C range. Microencapsulation of Wuyi Rock Tea volatile oil further delays its heat loss, and the addition of tea polyphenols results in microcapsules retaining a higher mass fraction throughout the heating process, indicating further improvement in its thermal stability.

[0069] 4) Volatility stability Using the PEN3 electronic nose (AIRSENSE, Germany), 10 mg of sample was added to a 40 mL sample vial, sealed, and kept in an oven at room temperature / 100℃ for 30 min before measurement was performed using the electronic nose. The types of sensitive substances corresponding to the sensors are shown in Table 2.

[0070] The electronic nose analysis results of Wuyi Rock Tea volatile oil and Wuyi Rock Tea volatile oil microcapsules are as follows: Figure 9 and Figure 10As shown in the figure. The results show that the odor radar maps of the microcapsules before and after heating are highly similar to those of the volatile oil, and the response values ​​of the microcapsules to each sensor are relatively lower, indicating that the microcapsules can effectively inhibit the volatilization of various substances in the volatile oil and endow it with a certain degree of thermal stability. Principal component analysis was performed on Wuyi rock tea volatile oil and Wuyi rock tea volatile oil microcapsules based on electronic nose data to comprehensively compare the odor differences before and after encapsulation and before and after heat processing. The contribution rate of PC1 was 92.9%, and the contribution rate of PC2 was 4.7%. The cumulative contribution rate of the first two principal components was 97.6%. The contribution rate of principal component PC1 was significantly greater than that of principal component PC2, indicating that the information collected by the electronic nose can almost represent the information of most of its volatile components. As can be seen from the figure, the microcapsule sample points after encapsulation and heat treatment are far away from the volatile oil. Compared with the microcapsules that have not undergone heat treatment, the sample points of the heat-treated microcapsules are closer to the volatile oil sample points. This indicates that the microcapsules encapsulate the volatile oil inside, and after heat treatment, some of the volatile oil is released from the inside of the microcapsules.

[0071] Table 2. Sensor-related Sensitive Substance Types serial number Sensor Name Types of sensitive substances R1 W1C Aromatic components: benzene R2 W5S Sensitive to nitrogen oxides R3 W3C Ammonia compounds are sensitive to aromatic components. R4 W6S It is mainly selective for hydrides. R5 W5C Short-chain alkane aromatic components R6 W1S Sensitive to methyl compounds R7 W1W Sensitive to inorganic sulfides R8 W2S Sensitive to alcohols, aldehydes and ketones R9 W2W Aromatic components, sensitive to organosulfur compounds R10 W3S Sensitive to long-chain alkanes Example 6: Preparation of microcapsules encapsulating volatile oils from Wuyi rock tea See process Figure 1 Take 100g of Wuyi Rock Tea (Da Hong Pao) powder, extract it for 30min using a simultaneous distillation extraction device, collect the distillate with dichloromethane, dry it with anhydrous sodium sulfate, remove the solvent by rotary evaporation, and obtain cinnamon tea volatile oil, which is stored at -20℃.

[0072] Prepare solutions of 1% gelatin, 1% gum arabic, and 10% tea polyphenols, respectively, and stir magnetically until completely dissolved to obtain wall material solutions.

[0073] Dissolve the volatile oil of Wuyi rock tea in MCT oil, add 1 mL to 100 mL of gum arabic solution, stir evenly at room temperature, and shear at 10000 r / min for 10 min to obtain a uniform emulsion.

[0074] Add 100 mL of gelatin solution to the emulsion, adjust the pH of the solution to 4.3, react at 40℃ for 30 min, cool in an ice bath for 30 min, add 6 mL of 10% tea polyphenol solution, and crosslink at room temperature for 1 h.

[0075] The cross-linked solution was placed in a 4°C refrigerator for phase separation for 1 h. The precipitate was taken as Wuyi rock tea volatile oil microcapsules, which were then vacuum freeze-dried and stored to obtain reddish-brown microcapsule powder with a tea aroma.

[0076] The encapsulation rate of the microcapsules in this embodiment was determined to be 87.99%.

[0077] Although the present invention has been described above through embodiments, those skilled in the art should understand that any improvements and modifications made to the present invention without departing from its spirit and essence should fall within the protection scope of the present invention.

Claims

1. A microcapsule for stabilizing the volatile oil of Wuyi rock tea, characterized in that, It is prepared by the following steps: (1) The volatile oil of Wuyi rock tea and medium-chain triglyceride oil were stirred and mixed to obtain the oil phase, and the volume ratio of the two was 1:3~5; (2) Gum arabic dissolves in water to form an aqueous phase; (3) The oil phase was added to the aqueous phase, sheared, gelatin was added and a re-coagulation reaction was carried out. After cooling in an ice bath, tea polyphenols were added for solidification and cross-linking, and the static phase was separated to obtain Wuyi rock tea volatile oil microcapsules.

2. The microcapsules for stabilizing Wuyi rock tea volatile oil according to claim 1, characterized in that, The volatile oil from Wuyi rock tea is obtained by simultaneous distillation and extraction, which combines steam distillation and solvent extraction processes, with dichloromethane as the solvent.

3. The microcapsules for stabilizing Wuyi rock tea volatile oil according to claim 2, characterized in that, The simultaneous distillation and extraction method is as follows: Wuyi rock tea powder is added to water, heated to boiling and maintained for 25-40 minutes; simultaneously, dichloromethane is heated to boiling, and the volatile oil is collected in gaseous condition using dichloromethane, cooled to obtain a dichloromethane solution of volatile oil; the solvent is removed by evaporation to obtain Wuyi rock tea volatile oil.

4. The microcapsules for stabilizing Wuyi rock tea volatile oil according to claim 1, characterized in that, Prepare solutions of gelatin and gum arabic with a mass concentration of 0.1-1% respectively. In step (2), dissolve the volatile oil of Wuyi rock tea in MCT oil and then add it to the gum arabic solution.

5. The microcapsules for stabilizing Wuyi rock tea volatile oil according to claim 1, characterized in that, The volume ratio of the gelatin solution to the gum arabic solution is 1:0.8~1.

2.

6. The microcapsules for stabilizing Wuyi rock tea volatile oil according to claim 1, characterized in that, In step (3), the shearing rate is 5000~15000 rpm and the shearing time is 5~15 min.

7. The microcapsules for stabilizing Wuyi rock tea volatile oil according to claim 1, characterized in that, In step (3), the re-coagulation reaction after adding gelatin solution is carried out at pH 4.0~4.5 and temperature 38~40℃, and the phase separation process is carried out at 2~6℃.

8. The microcapsules of stabilized Wuyi rock tea volatile oil according to any one of claims 1 to 7, characterized in that, In step (3), after cooling in an ice bath for 30 min, a tea polyphenol solution with a mass concentration of 5-10% is added for curing and crosslinking, and crosslinking is carried out at room temperature for 1-3 h; the volume of the tea polyphenol solution is 5-8% of the volume of the gelatin solution, and the pH of the tea polyphenol solution is adjusted to 4.0-4.

5.

9. The microcapsules for stabilizing Wuyi rock tea volatile oil according to claims 1-7, characterized in that, The mass ratio of volatile oil, medium-chain triglyceride oil, gelatin, gum arabic, and tea polyphenols in Wuyi rock tea is 1:4~5:5~6:5~6:3~4.

10. The microcapsules of stabilized Wuyi rock tea volatile oil according to any one of claims 1 to 7, characterized in that, In step (3), the time for the complex condensation reaction is 10-30 min, and the time for the ice bath cooling is 30-60 min.

Images