Low-caffeine high-catechin tea extract microcapsule as well as preparation method and application thereof

Abstract

The invention relates to a low-caffeine high-catechin tea extract microcapsule as well as a preparation method and application thereof. The tea extract microcapsule is formed by encapsulating a low-caffeine and high-catechin tea extract serving as a core material and maltodextrin and / or Arabic gum serving as a wall material; wherein the content of caffeine in the tea extract is not higher than 0.2 wt%, the content of catechin is not lower than 90 wt%, and the load rate of the catechin in the tea extract microcapsule is not lower than 30%. The preparation method comprises the following steps: dissolving maltodextrin and / or Arabic gum in water to obtain a wall material solution; adding a low-caffeine high-catechin tea extract into the wall material solution under a stirring condition; and drying and crushing the mixed solution to obtain the tea extract microcapsule. Compared with the prior art, the low-caffeine and high-catechin tea extract is successfully embedded in the wall material by adopting a microcapsule technology, so that the stability of the tea extract can be remarkably improved, and the bad smell or taste of the tea extract can be covered.

Description

Technical Field

[0001] The invention belongs to the technical field of functional foods, and in particular relates to a low-caffeine and high-catechin tea extract microcapsule and a preparation method and application thereof. Background Art

[0002] Tea is one of the most consumed beverages in the world and is a globally popular healthy drink with a broad consumer market around the world. Tea extract refers to the extract obtained by extracting active ingredients (including catechins, caffeine, aromatic oils, water, minerals, pigments, carbohydrates, proteins, amino acids, vitamins, etc.) from tea leaves through relevant extraction technologies. The green emerging and efficient extraction technology can effectively improve the extraction efficiency, enrich functional ingredients, reduce pollution and improve safety. Tea extract can currently be used in the fields of instant tea, concentrated tea liquid, functional food and health products.

[0003] As the main component of tea extract, catechins mainly include epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), epicatechin (EC) and other components, which have outstanding performance in anti-inflammatory, anti-cancer, antioxidant and other health effects. However, the intake of caffeine in tea extracts can cause adverse effects such as sleep deprivation, palpitations, and anxiety in some people who are intolerant. Therefore, the preparation of tea extracts with low caffeine and high catechins has important application value.

[0004] In addition, catechins, as the main functional components of tea extracts, are easily affected by environmental changes, such as being easily degraded under high temperature conditions, thereby destroying their nutritional effects. In addition, catechins are also the source of bitterness and astringency. EGC, EC, EGCG, and ECG in catechins can all stimulate human bitter receptors, and the astringency of ester catechins is more obvious than that of non-ester catechins.

[0005] Therefore, the technical problem of how to improve the stability of catechin active substances in tea extracts and reduce the bitter taste of catechins needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to improve the stability of catechin active substances in tea extracts and reduce the bitterness and astringency of catechins, and to provide a low-caffeine and high-catechin tea extract microcapsule and its preparation method and application.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The present invention first provides a low-caffeine and high-catechin tea extract microcapsule, wherein the tea extract microcapsule is formed by using the low-caffeine and high-catechin tea extract as a core material and maltodextrin and / or gum arabic as a wall material for encapsulation;

[0009] The content of caffeine in the tea extract is not higher than 0.2 wt %, the content of catechin is not lower than 90 wt %, and the loading rate of catechin in the tea extract microcapsule is not lower than 30 %.

[0010] Furthermore, the particle size of the tea extract microcapsule is 150-350nm.

[0011] Furthermore, the catechins in the tea extract microcapsules have a 30-day retention rate at 4° C. higher than 70%.

[0012] Furthermore, the low-caffeine high-catechin tea extract is prepared by the following method:

[0013] The tea raw materials are crushed and sieved to obtain tea powder;

[0014] Adding a complex enzyme composed of pectinase and cellulase to tea powder for enzymolysis, and drying the enzymolyzed tea soup to obtain a high-catechin tea extract;

[0015] The re-dissolved high-catechin tea extract is adsorbed by a macroporous resin, and then the macroporous resin is eluted. After removing the solvent in the eluent, the low-caffeine high-catechin tea extract can be obtained.

[0016] The present invention also provides a method for preparing tea extract microcapsules, comprising the following steps:

[0017] S1: dissolving maltodextrin and / or gum arabic in water to obtain a wall material solution;

[0018] S2: adding the tea extract with low caffeine and high catechins to the wall material solution of S1 under stirring;

[0019] S3: drying and crushing the mixed solution to obtain the tea extract microcapsules.

[0020] Furthermore, in step S1, the mass ratio of maltodextrin to gum arabic is 1:0 or (0-6):1.

[0021] Furthermore, in step S2, the mass ratio of the tea extract to the wall material is 1:(1-2), preferably 1:2.

[0022] Furthermore, in step S2, the stirring speed is 600-1000 rpm, preferably 800 rpm.

[0023] Furthermore, in step S2, the stirring time is 20-60 min, preferably 30 min.

[0024] Furthermore, in step S3, the drying is performed by freeze drying, and the drying time is 12-24 hours.

[0025] The present invention also provides an application of tea extract microcapsules in the preparation of instant tea, concentrated tea liquid, functional food and health food.

[0026] Specifically, tea extract microcapsules improve the stability and bioavailability of catechin active substances through microcapsule technology, and can mask the bitter taste of catechins, enrich the aroma and fragrance, and can produce more palatable and more stable foods and health foods.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention adopts microcapsule technology and uses polymer materials as wall materials to successfully embed low-caffeine and high-catechin tea extracts in the wall materials, which can significantly improve the stability of the tea extracts and mask the unpleasant odor or taste of the tea extracts.

[0029] (2) The tea extract microcapsules of the present invention have good storage stability and thermal stability as demonstrated by potential, retention rate tests, thermogravimetric tests, etc., and are convenient for long-term storage.

[0030] (3) The present invention has good stability in the gastric digestion stage through an in vitro simulated gastrointestinal digestion test. The tea extract after embedding can achieve sustained release in the stomach without affecting the release in the small intestine stage, indicating that it has a good targeted release effect, thereby improving the bioavailability.

[0031] (4) The tea extract microcapsules of the present invention not only retain the original aroma of the tea extract, but also add more floral and sweet aromas to it, which improves the sensory quality of the tea extract and makes it more in line with the taste preferences of consumers.

[0032] (5) During the preparation process of the tea extract microcapsules of the present invention, no additional emulsifier such as Tween 80 is required, and rapid preparation at room temperature can be achieved.

[0033] (6) The tea extract microcapsules of the present invention help improve the stability of low-caffeine high-catechin tea extracts, increase the bioavailability of catechins without changing their flavor characteristics, and are conducive to making related tea functional foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a graph showing the embedding rate and loading rate of the tea extract microcapsules of Examples 1-9 of the present invention.

[0035] Figure 2 Graph showing particle size and distribution of tea extract microcapsules of Examples 1-9 of the present invention.

[0036] Figure 3 Graphs showing PDI and Zeta potential of the tea extract microcapsules of Examples 1-9 of the present invention.

[0037] Figure 4 It is the scanning electron microscope picture of the tea extract and S9 tea extract microcapsule of the present invention.

[0038] Figure 5 It is the Fourier infrared spectra of the tea extract, maltodextrin, gum arabic and S9 tea extract microcapsules of the present invention.

[0039] Figure 6 The XRD patterns of the tea extract, maltodextrin, gum arabic and S9 tea extract microcapsules of the present invention are shown.

[0040] Figure 7 It is the TGA chart of the tea extract, maltodextrin, gum arabic and S9 tea extract microcapsules of the present invention.

[0041] Figure 8 It is the catechin retention rate of the tea extract of the present invention and S9 tea extract microcapsule.

[0042] Fig. 9 It is the retention rate of catechins in the tea extract and S9 tea extract microcapsules of the present invention during simulated gastrointestinal digestion.

[0043] Fig.10 The figure shows the changes of volatile compounds in different stages of the present invention. A shows the changes of quantity, B shows the changes of the proportion of the types and contents, and C shows the Venn diagram of volatile compounds in different stages.

[0044] Fig.11 (A) PCA diagram, (B) HCA diagram and (C) differential metabolite heat map of samples at different stages of the present invention. DETAILED DESCRIPTION

[0045] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0046] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0047] The low-caffeine and high-catechin tea extracts in the following embodiments of the present invention can be obtained from commercial sources or extracted using the following method:

[0048] (1) The green tea raw material (referred to as GT1 in subsequent tests) was crushed by a grinder and passed through a 40-mesh sieve to obtain tea powder.

[0049] (2) Preparation of high-catechin extract: Weigh 10g of tea powder and 10mg of compound enzyme and place them in a 250ml conical flask. The mass ratio of pectinase to cellulase in the compound enzyme is 3:2. Add 150ml of pure water and react in a 60℃ water bath shaker for 30min. After cooling to room temperature, transfer to a centrifuge and centrifuge at 5000rpm for 5min. Filter the supernatant to obtain enzymolysis tea soup. The enzymolysis tea soup is vacuum freeze-dried for 48h to obtain a high-catechin tea extract.

[0050] (3) Preparation of high-catechin low-caffeine tea extract: The tea soup after the high-catechin tea extract is re-dissolved is subjected to column adsorption at a sample flow rate of 1.5-4.5 mL / min. Accurately weigh 20 ml of macroporous resin LX-8 and slowly load it into the chromatography column, with a sample concentration of 30 mg / mL and an adsorption flow rate of 1.5 mL / min. The resin column after adsorption is gradient eluted with 20%-70% ethanol, and the eluate is collected and concentrated by rotary evaporation to obtain a brown-yellow powder of high-catechin low-caffeine tea extract, which is recorded as TE in the following tests. LCHC . According to the detection by liquid chromatography, the catechin content is greater than 90wt%, and the caffeine content is less than 0.1wt%.

[0051] The present invention focuses on the preparation of high-catechin low-caffeine tea extract microcapsules and the optimization of their performance, aiming to improve the stability and bioavailability of tea extracts and reduce their bitter taste through microcapsule embedding technology, which is specifically described in conjunction with the following examples.

[0052] Embodiment 1:

[0053] This embodiment uses a high-catechin low-caffeine tea extract as a core material and maltodextrin as a wall material to specifically provide a high-catechin low-caffeine tea extract microcapsule, and the preparation method thereof is as follows:

[0054] (1) Weigh 1 g of maltodextrin as the embedding wall material, dissolve it in 10 mL of deionized water, and vortex mix for 5 min until it is completely dissolved.

[0055] (2) Weigh 1 g of high-catechin and low-caffeine tea extract and add it to the wall material solution, and stir it with a magnetic stirrer at 800 rpm for 30 min.

[0056] (3) freeze-drying the mixed solution, and crushing the sample after drying for 24 hours to obtain the high-catechin and low-caffeine tea extract microcapsules.

[0057] Embodiment 2:

[0058] This embodiment uses high-catechin and low-caffeine tea extract as a core material and gum arabic as a wall material to specifically provide a high-catechin and low-caffeine tea extract microcapsule.

[0059] The difference from Example 1 is that the wall material of this example is gum arabic, and the mass ratio of the total mass of the wall material to the tea extract is 1:1. The preparation method is similar to Example 1.

[0060] Embodiment 3:

[0061] This embodiment uses a high-catechin low-caffeine tea extract as a core material, and uses maltodextrin and gum arabic as a wall material, specifically providing a high-catechin low-caffeine tea extract microcapsule.

[0062] The difference from Example 1 is that the wall materials of this example are maltodextrin and gum arabic, the mass ratio of maltodextrin to gum arabic is 1:1, and the mass ratio of the total mass of the wall materials to the mass ratio of the tea extract is 1:1. The preparation method is referred to Example 1.

[0063] Embodiment 4:

[0064] This embodiment uses a high-catechin low-caffeine tea extract as a core material, and uses maltodextrin and gum arabic as a wall material, specifically providing a high-catechin low-caffeine tea extract microcapsule.

[0065] The difference from Example 1 is that the wall materials of this example are maltodextrin and gum arabic, the mass ratio of maltodextrin to gum arabic is 2:1, and the mass ratio of the total mass of the wall materials to the mass ratio of the tea extract is 1:1. The preparation method is similar to Example 1.

[0066] Embodiment 5:

[0067] This embodiment uses a high-catechin low-caffeine tea extract as a core material, and uses maltodextrin and gum arabic as a wall material, specifically providing a high-catechin low-caffeine tea extract microcapsule.

[0068] The difference from Example 1 is that the wall materials of this example are maltodextrin and gum arabic, the mass ratio of maltodextrin to gum arabic is 4:1, and the mass ratio of the total mass of the wall materials to the mass ratio of the tea extract is 1:1. The preparation method is similar to Example 1.

[0069] Embodiment 6:

[0070] This embodiment uses a high-catechin low-caffeine tea extract as a core material, and uses maltodextrin and gum arabic as a wall material, specifically providing a high-catechin low-caffeine tea extract microcapsule.

[0071] The difference from Example 1 is that the wall materials of this example are maltodextrin and gum arabic, the mass ratio of maltodextrin to gum arabic is 6:1, and the mass ratio of the total mass of the wall materials to the mass ratio of the tea extract is 1:1. The preparation method is similar to Example 1.

[0072] Embodiment 7:

[0073] This embodiment uses a high-catechin low-caffeine tea extract as a core material, and uses maltodextrin and gum arabic as a wall material, specifically providing a high-catechin low-caffeine tea extract microcapsule.

[0074] The difference from Example 1 is that the wall materials of this example are maltodextrin and gum arabic, the mass ratio of maltodextrin to gum arabic is 2:1, and the mass ratio of the total mass of the wall materials to the tea extract is 2:1. The preparation method is similar to Example 1.

[0075] Embodiment 8:

[0076] This embodiment uses a high-catechin low-caffeine tea extract as a core material, and uses maltodextrin and gum arabic as a wall material, specifically providing a high-catechin low-caffeine tea extract microcapsule.

[0077] The difference from Example 1 is that the wall materials of this embodiment are maltodextrin and gum arabic, the mass ratio of maltodextrin to gum arabic is 4:1, and the preparation method is similar to that of Example 1.

[0078] Embodiment 9:

[0079] This embodiment uses a high-catechin low-caffeine tea extract as a core material, and uses maltodextrin and gum arabic as a wall material, specifically providing a high-catechin low-caffeine tea extract microcapsule.

[0080] The difference from Example 1 is that the wall materials of this example are maltodextrin and gum arabic, the mass ratio of maltodextrin to gum arabic is 6:1, and the preparation method is similar to that of Example 1.

[0081] In the following tests and tables, the tea extract microcapsules of Examples 1-9 are denoted as S1 to S9, respectively, and the mixing ratios of different wall materials are summarized in Table 1.

[0082] Table 1 Summary of the mixing ratios of different wall materials from S1 to S9

[0083] Samples MD:GA(w:w) Wall materials(g) <![CDATA[TE LCHC (g)]]> S1 1:0 1 1 S2 0:1 1 1 S3 1:1 1 1 S4 2:1 1 1 S5 4:1 1 1 S6 6:1 1 1 S7 2:1 2 1 S8 4:1 2 1 S9 6:1 2 1

[0084] The present invention uses the following test tests to evaluate the comprehensive performance of tea extract microcapsules S1 to S9, specifically including:

[0085] (1) Determination of embedding efficiency and loading rate: 100 mg of microcapsule powder was dissolved in 5 mL of anhydrous ethanol and vortexed for 30 seconds to ensure full dispersion. The mixture was then centrifuged at 5000 rpm for 5 minutes and the supernatant was used to determine the catechin content by HPLC. The embedding efficiency and loading rate were calculated as follows:

[0086]

[0087]

[0088] (2) Determination of particle size and potential of microcapsule system: Zeta potential meter was used to measure the TE of the unencapsulated LCHC Zeta potential, particle size, particle size distribution and polymer dispersibility index of S1~S9 tea extract microcapsules in aqueous phase.

[0089] (3) Determination of moisture content of microcapsules: Refer to GB5009.3-2016 for determination of moisture content, and the calculation formula is as follows:

[0090]

[0091] Wherein, M1 is the mass of the weighing dish and the sample (g), M2 is the mass of the weighing dish and the sample after drying (g), and M3 is the mass of the weighing dish (g).

[0092] (4) Determination of water absorption of microcapsules: Weigh appropriate amounts of non-microencapsulated microcapsules and nine kinds of tea extract microcapsules respectively and place them in weighing dishes. Place them in a dark environment with a temperature of 25°C and a humidity of 60% without opening. After absorbing moisture for 12 hours, weigh the sample weight. The calculation formula is as follows:

[0093]

[0094] Where m1 is the mass of the weighing dish (g), m2 is the mass of the weighing dish and the sample before moisture absorption (g), and m3 is the mass of the weighing dish and the sample after moisture absorption (g).

[0095] (5) Determination of microcapsule solubility: Weigh 200 mg of unencapsulated TE LCHCThe tea extract microcapsules of S1 to S9 were placed in a centrifuge tube, 10 mL of deionized water was added, and vortexed at 15000 rpm for 5 min. The solution was centrifuged at 5000 × g for 5 min, 9 mL of the supernatant was transferred to a weighing dish, placed in an oven at 105 ° C and dried for 4 h to obtain a dry powder sample and weighed. Solubility (%) = W1 / W0 × 100, where W1 is the mass of the recovered sample (g), and W0 is the mass of the original sample (g).

[0096] Depend on Figure 1 It can be seen that the present invention successfully prepared tea extract microcapsules S1 to S9 with an embedding rate of >90% and a loading rate of >30%. Among them, the embedding rates of S7, S8, and S9 were significantly higher than those of S1 to S6, and the embedding rates of the three were 98.43±0.04%, 98.12±0.06%, and 98.10±0.08%, respectively. The increase in the concentration of the wall material introduced more hydrophilic and hydrophobic functional groups, increased the electrostatic interaction between the wall material polymer and the active compound, and thus increased the microcapsule embedding rate.

[0097] Depend on Figure 2-3 It can be seen that the particle sizes of the tea extract microcapsules S1 to S9 of the present invention are all less than 330 nm, while the unencapsulated TE LCHC The particle size is 986.03±0.77nm. LCHC In comparison, all tea extract microcapsules showed significantly reduced particle sizes, among which S9 had the smallest particle size of 198.11±5.91nm, and the particle size distribution was the most uniform. This was because the MD content in sample S9 was higher, and the GA content with higher viscosity was relatively lower, which reduced the degree of particle aggregation and resulted in a smaller particle size. Smaller microcapsule particle size is also conducive to passing through the oral administration barrier during oral administration, and then releasing tea extract in the small intestine, improving bioavailability.

[0098] Zeta potential indicates the stability of the inclusion complex at the macroscopic level. When the absolute value of Zeta potential is ≥20mV, the substance is usually considered to have excellent steric stability. Figure 3 It can be seen that there is no significant difference in the Zeta potential of the six samples S4 to S9, and the absolute values ​​are all greater than 20mV, which are 20.4±0.71mV, 20.85±0.78mV, 20.05±1.06mV, 20.5±0.57mV, 21.25±0.35mV, and 21.15±0.78mV, respectively. These six microcapsule samples have good stability. The absolute values ​​of the Zeta potential of the six samples S1 to S3 are all greater than 15mV, and they also have good stability.

[0099] Moisture content is an important factor affecting powder drying efficiency, fluidity and storage stability. LCHCThe moisture contents of S1 to S9 microcapsule samples are shown in Table 2.

[0100] Table 2 Summary of moisture content, hygroscopicity and solubility

[0101] Samples Moisture content(%) Hygroscopicity (%) Solubility(%) <![CDATA[TE LCHC ]]> <![CDATA[5.88±0.26 a ]]> <![CDATA[8.88±0.29 c ]]> <![CDATA[91.02±0.43 b ]]> S1 <![CDATA[5.02±1.20 abc ]]> <![CDATA[9.47±1.04 abc ]]> <![CDATA[89.53±0.32 c ]]> S2 <![CDATA[5.86±0.31 a ]]> <![CDATA[9.71±0.45 ab ]]> <![CDATA[94.87±1.46 ab ]]> S3 <![CDATA[5.36±0.45 ab ]]> <![CDATA[9.67±0.12 a ]]> <![CDATA[94.54±0.80 ab ]]> S4 <![CDATA[5.62±0.28 a ]]> <![CDATA[9.88±0.50 ab ]]> <![CDATA[92.58±1.65 b ]]> S5 <![CDATA[5.27±0.41 ab ]]> <![CDATA[9.64±0.29 ab ]]> <![CDATA[94.12±0.32 ab ]]> S6 <![CDATA[5.60±0.95 ab ]]> <![CDATA[8.71±0.67 bcd ]]> <![CDATA[94.32±0.33 ab ]]> S7 <![CDATA[4.99±0.16 b ]]> <![CDATA[8.59±0.16 c ]]> <![CDATA[94.89±2.92 ab ]]> S8 <![CDATA[4.44±0.60 bc ]]> <![CDATA[8.43±0.57 cd ]]> <![CDATA[94.67±1.30 ab ]]> S9 <![CDATA[4.08±0.26 c ]]> <![CDATA[8.26±0.12 d ]]> <![CDATA[94.80±0.54 a ]]>

[0102] Note: Different letters in the same column represent significant differences (P<0.05).

[0103] As shown in Table 2, compared with the unencapsulated TE LCHC Compared with TE (water content of 5.88 ± 0.26%), the moisture content of the microcapsule samples with nine different wall material ratios is lower than that of TE LCHC , among which S9 had the lowest moisture content of 4.08 ± 0.26%, indicating that the moisture content of the microcapsules decreased with the increase of maltodextrin concentration.

[0104] Hygroscopicity refers to the ability of a sample to absorb moisture from the environment and also affects the storage stability of the powder. When the hygroscopicity is <20%, the powder is defined as slightly hygroscopic. As shown in Table 2, although TE LCHC Compared with the nine different wall materials, the hygroscopicity of the microcapsule samples is <20%, but the hygroscopicity of S1, S2, S3, S4, and S5 is higher than that of TE LCHC As the concentration of maltodextrin increases, the hygroscopicity gradually decreases, and S9 has the lowest hygroscopicity, which is similar to TE LCHC There is a significant difference, indicating that the addition of wall materials helps to reduce TE LCHC Hygroscopicity and adhesion.

[0105] Solubility refers to the ability of a powder to form a solution or suspension in water and is the most reliable parameter for evaluating powder quality. LCHC (solubility is 91.02±0.43%), the solubility of S1 is significantly lower than that of TE LCHC , while the other eight microcapsule samples were LCHC The solubility of all samples was improved, and there was no significant difference in the solubility of the eight samples, among which S7 had the highest solubility.

[0106] Based on the data results of the embedding rate, loading rate, particle size potential and physicochemical properties of the above nine different wall material combinations of tea extract microcapsules, the S9 sample was selected for structural characterization and subsequent testing. The specific test contents include:

[0107] (1) Scanning electron microscopy (SEM) morphology characterization: The samples were gold-coated for 45 s at 20 mA using a sputtering coater and then analyzed at 5 kV voltage acceleration.

[0108] (2) Fourier transform infrared spectroscopy (FTIR): Weigh 2 mg of MD, GA, and TE respectively. LCHC The tea extract microcapsules were ground evenly with 200 mg KBr in a mortar and then pressed into tablets. The obtained slices were subjected to infrared spectroscopy scanning under the scanning conditions of a scanning range of 400 cm -1 -4000cm -1 , resolution 2cm -1 The number of times was 32. The embedding success was judged by comparing the difference of the absorption peaks in the infrared spectrum of each sample.

[0109] (3) X-ray diffraction (XRD): MD, GA, TE LCHC The tea extract microcapsules were evenly spread on a glass slide, flattened and fixed on a sample stage. Cu and Kα radiation were used, with an accelerating voltage of 40KV, an accelerating current of 100mA, 1KCPS, a temperature of 25°C, an angular velocity of 2° / min, and the X-ray diffractometer was continuously scanned within an angle range of 5°-60°.

[0110] (4) Thermogravimetric analysis (TGA): Weigh MD, GA, and TE LCHC And 8 mg of tea extract microcapsules, the N2 flow rate was controlled to be 20 mL / min, the heating rate was 10°C / min, the temperature was raised from 30°C to 700°C, and the thermogravimetric curve was measured by a thermogravimetric analyzer.

[0111] (5) Storage stability: The unencapsulated TE LCHC The microcapsules of S10 and S20 were stored at 40°C and 4°C for 30 days, respectively. Samples were taken at 0, 2, 5, 8, 15 and 30 days, and the stability of the products was determined by measuring the changes in their catechin contents.

[0112] (6) In vitro simulated gastrointestinal digestion: In vitro simulated gastrointestinal digestion is divided into gastric digestion stage and intestinal digestion stage. The electrolyte solution (Simulated gastric fluid, SGF) in the gastric digestion stage contains: KCl 6.9mmol / L, KH2PO4 0.9mmol / L, NaHCO3 25mmol / L, NaCl 47.2mmol / L, MgCl2(H2O) 60.1mmol / L, (NH4)2CO3 0.5mmol / L.

[0113] The original electrolyte solution of the intestinal digestion stage (Simulated intestinal fluid, SIF) contains: KCl 6.8mmol / L, KH2PO4 0.8mmol / L, NaHCO3 85mmol / L, NaCl 38.4mmol / L, MgCl2 (H2O) 60.33mmol / L.

[0114] Gastric digestion stage: Take 25 mL of tea extract reconstituted solution (15 mg / mL) and mix it with 20 mL of gastric digestion stage electrolyte solution, then add 3.333 g of pepsin and 12.5 μL of CaCl2 (0.3 M) to mix, then add HCl to adjust the pH to 3.0, and finally add deionized water to make the gastric digestion solution 25 mL, and place it in a 37°C water bath and shake for 2 hours.

[0115] Intestinal digestion stage: 20 mL of gastric digestion fluid was mixed with 16 mL of intestinal digestion electrolyte solution, followed by 16 mg of trypsin, 2.5 mL of fresh bile (160 mM), and 40 μL of CaCl2 (0.3 M), and then NaOH was added to adjust the pH to 7.0. Finally, deionized water was added to adjust the volume of the intestinal digestion fluid to 20 mL, and the mixture was placed in a 37°C water bath for 2 hours. During the simulated gastrointestinal digestion, samples were taken every 30 minutes, and the enzymes were inactivated in a 100°C water bath for 2 minutes. After centrifugation at 5000×g for 5 minutes, the supernatant was taken to determine the catechin content.

[0116] (7) Aroma analysis of tea extract microcapsules: 0.5 g of green tea leaves, TE LCHC , S9 microcapsules were placed in a 20 mL sample bottle, 5 mL of boiling ultrapure water was added, and an internal standard (20 μL of ethyl decanoate, 0.01 mg / mL) was added. The sample bottle was then placed in a heated oscillator and equilibrated at 60°C for 10 min. The SPME fiber extraction head was inserted into the headspace bottle and headspaced at 60°C for 50 min. Finally, the SPME fiber head was introduced into the injector and kept for 5 min to allow thermal desorption of volatile compounds.

[0117] GC conditions: The injector temperature was maintained at 250°C. Helium (purity>99.99%) was used as the carrier gas at a linear velocity of 1.0 mL / min. The initial column temperature was maintained at 40°C for 2 min, then increased to 85°C at a rate of 3°C / min and maintained for 2 min. Subsequently, the temperature was continuously increased to 110°C at a rate of 2°C / min and maintained for 2 min. Finally, the temperature was further increased to 220°C at a rate of 5°C / min and maintained for 5 min.

[0118] MS conditions: electron bombardment ion source, ion source temperature 230 ° C, electron energy 70 eV, scan range 50amu-650amu. The quadrupole mass detector, ion source and transfer line temperatures were set to 150 ° C, 230 ° C and 280 ° C, respectively. The mass spectrometer scan range was 30m / z-350m / z.

[0119] Data analysis: Compare with the information in the mass spectrometry database to determine the chemical structure, name, CAS number, etc. of the volatile substances. Volatile substance content (ng / g) = (internal standard substance content × volatile substance peak area) / internal standard substance peak area.

[0120] Depend on Figure 4 From the SEM image, we can see that due to TE LCHC Both S9 and S9 present irregular amorphous broken glass or flake particles of varying sizes. Figure 4 As shown in A and B, TE LCHC The surface of the flake particles is smooth and flat, and the edges are clear and smooth. Figure 4 As shown in C and D, the surface of the flaky particles of S9 is rough, showing a series of reticular structures, and the edges of the particles are curved and uneven. This proves that the structure of S9 has changed due to microencapsulation, and the surface reticular structure is caused by the attachment of the wall material and the wrapping of the flaky particles, proving that the wall material of the present invention is successfully wrapped on the surface of the core material.

[0121] Depend on Figure 5 From the FITR spectrum, we can see that TE LCHC and S9 at 3327cm -1 The broad band at 2919 cm is caused by the stretching vibration of -OH. -1 and 1696cm -1 are the stretching vibrations of CH and C=O, respectively, proving that TE LCHC and S9 both have carbonyl groups, 1238 cm -1 The stretching vibration of CO is at 1604cm -1 and 1443cm -1 The main absorption peaks of MD and GA are 3327cm -1 The -OH absorption band at 2919 cm -1 The characteristic peaks of the infrared spectra of S9 and wall materials (MD and GA) are not much different, and its spectrum is not the same as that of wall materials and TE LCHC The simple superposition of wall material and TE LCHC There is interaction, and TE is not present in S9 LCHC The characteristic absorption peak of the nanostructured carbon foam proves that it is completely embedded in the wall material.

[0122] Depend on Figure 6 From the XRD spectrum, we can see that TE LCHC A large package peak appears at 23.4°, and there is no characteristic peak of crystal diffraction and fine spectral peak structure. It can be inferred that there is no crystal structure, so it is in an amorphous state. The two wall materials and microcapsule sample S9 also have no characteristic peaks, which can be judged that microencapsulation has not changed TE LCHCstructure.

[0123] Depend on Figure 7 From the TGA diagram, we can see that TE LCHC The weight loss of S9 and wall materials can be divided into two stages. The first stage is 30-100℃, with slow weight loss. The weight loss in this stage is mainly caused by the evaporation of water in the sample. LCHC The second stage of weight loss is 166-700℃, the second stage of weight loss of S9 is 207-700℃, and the second stage of weight loss of wall material occurs at about 300℃. The weight loss in this stage is caused by the degradation of sample components and the destruction of structure. The temperature at which S9 begins to degrade is higher than TE LCHC This is because the wall material wraps the sample structure to a certain extent, proving that the thermal stability of S9 is better than that of TE LCHC .

[0124] Depend on Figure 8 It can be seen that at different storage temperatures (40℃ and 4℃), TE LCHC The retention rate of catechins in S9 was 75.06%, which was higher than that in TE. LCHC The retention rate of TE was 72.6% at 40°C, which proved that microencapsulation can effectively improve the storage stability of tea extract. At 40°C, catechins were rapidly oxidized and degraded in the first five days, and the retention rate decreased significantly. At 4°C, TE LCHC The retention rates of S9 and S10 are higher than those at 40° C. Therefore, the tea extract microcapsules prepared in the present invention have better storage stability under a low temperature environment of 4° C.

[0125] Depend on Fig. 9 It can be seen that the retention rate of total catechins and five different catechins in the simulated gastric digestion stage is about 70% on average. In the simulated gastric digestion stage, the retention rate of catechins in S9 is as high as about 90%, proving that microencapsulation can stabilize the structure of catechins, prevent catechins from rapid degradation in the gastric environment, and play a role in sustained release. In the simulated intestinal digestion stage, the content of total catechins and five different catechins decreased significantly, and the retention rate was only about 5%. This is because the ions, pancreatic enzymes and bile salts present in the simulated intestinal fluid will affect the stability of the embedding system and catechins. The wall material is rapidly degraded under the action of the simulated intestinal fluid, resulting in rapid metabolism of microencapsulated tea extract and catechins in the tea extract. Therefore, the tea extract after embedding can achieve sustained release in the stomach without affecting the release in the small intestine stage, so the microencapsulation technology can improve the stability of the tea extract while making it have a targeted effect, thereby improving the bioavailability.

[0126] Depend on Fig.10It can be seen that HS-SPME-GC-MS identified a total of 63 volatile substances, including 8 alcohols, 7 ketones, 11 aldehydes, 6 alkanes, 5 alkenes, 6 esters, 3 phenols, 8 acids, and 9 other compounds. GT1 contains 43 volatile substances, TE LCHC Contains 32 volatile substances, S9 contains 28 volatile substances, and microencapsulation reduces the types of volatile substances to a certain extent. Fig.10 AIt can be seen that during the preparation of tea extract, the amounts of alcohols, ketones, aldehydes, alkenes, acids and other compounds showed a downward trend, while the amounts of alkanes, esters and phenols increased. Fig.10 B shows that during the preparation of tea extract, the contents of alcohols, ketones, and aldehydes decreased significantly, olefins gradually disappeared, and the content of esters increased significantly. Fig.10 C It can be seen that there are 13 components detected in all three stages, namely phenylethanol, phenol, tea ketone, 2,4-condienal, benzaldehyde, butyric acid, 3-ethyl-4-methyl-maleimide, n-tetradecane, dihydroactinol, propionic acid, acetic acid, hexanoic acid, and dimethyl sulfoxide.

[0127] according to Fig.11 PCA analysis of A shows that there is a clear distinction between samples at different stages. LCHC The distance between them is relatively close, indicating that the aroma difference between the two is small, but they can be clearly distinguished. Microencapsulated tea extract sample S9 and tea raw materials GT1 and TE LCHC The distance between them is far, indicating that microencapsulation has a certain degree of influence on the aroma of the sample. Fig.11 B shows that the results of the HCA graph are consistent with those of the PCA graph.

[0128] According to P<0.05 and VIP>1, 8 different volatiles were screened out, namely phenylethanol, phenol, tea ketone, benzaldehyde, butyric acid, 2,4-heptadienal, n-tetradecane, and dimethyl sulfoxide. Among them, alcohols, ketones, and aldehydes are the main volatile aroma substances in tea. Benzaldehyde and 2,4-heptadienal have a great contribution to the fruity and floral aroma of green tea, and dimethyl sulfoxide brings a fresh aroma to green tea. Fig.11 C shows that the three substances in the sample after embedding all show a downward trend, indicating that the addition of wall materials has a certain degree of masking on the floral and fruity aroma and umami taste of the tea extract. Phenylethanol provides floral and sweet aromas for green tea, and tea ketones show floral aromas. Microencapsulation increases the content of these two substances, providing more floral and sweet aromas for the tea extract. The present invention not only retains the original aroma of the tea extract through microencapsulation technology, but also adds more floral and sweet aromas to it, which improves the sensory quality of the tea extract and makes it more in line with the taste preferences of consumers.

[0129] In summary, the present invention focuses on the preparation of tea extract microcapsules and their performance optimization, aiming to improve the stability and bioavailability of tea extracts and reduce bitterness through microcapsule embedding technology. The present invention screened a variety of different wall material combinations and different proportions of maltodextrin and gum arabic as wall materials for testing, and determined the optimal wall material combination by comprehensively evaluating the embedding rate, loading rate, particle size, potential and physicochemical properties. The potential, particle size and distribution of the microcapsules were accurately measured using a Zeta potential meter, and the structure of the microcapsules was characterized in detail by means of scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis, verifying that the wall material successfully encapsulated the tea extract and the structure was stable. Finally, an in vitro simulated gastrointestinal digestion experiment proved that the microencapsulation technology can significantly improve the stability of catechins in the gastric digestion stage, and HS-SPME-GC-MS was used to conduct an in-depth analysis of the aroma components at each stage in the preparation process of tea extracts. It was found that the microencapsulation technology not only retained the original aroma of the tea extract, but also added more floral and sweet aromas, significantly improving the sensory quality of the tea extract. It can be seen that the present invention uses a specific ratio of maltodextrin and gum arabic as wall materials, which can significantly improve the embedding effect of tea extract and prepare microcapsules with good thermal stability and long-term storage stability.

[0130] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A low-caffeine and high-catechin tea extract microcapsule, characterized in that: The tea extract microcapsules are formed by using low-caffeine and high-catechin tea extract as the core material and maltodextrin and / or gum arabic as the wall material for encapsulation; The content of caffeine in the tea extract is not higher than 0.2 wt %, the content of catechin is not lower than 90 wt %, and the loading rate of catechin in the tea extract microcapsule is not lower than 30 %.

2. The low-caffeine and high-catechin tea extract microcapsules according to claim 1, characterized in that: The particle size of the tea extract microcapsule is 150-350nm.

3. The low-caffeine and high-catechin tea extract microcapsules according to claim 1, characterized in that: The catechin retention rate in the tea extract microcapsules at 4° C. for 30 days is higher than 70%.

4. The low-caffeine and high-catechin tea extract microcapsules according to claim 1, characterized in that: The low-caffeine high-catechin tea extract is prepared by the following method: The tea raw materials are crushed and sieved to obtain tea powder; Adding a complex enzyme composed of pectinase and cellulase to tea powder for enzymolysis, and drying the enzymolyzed tea soup to obtain a high-catechin tea extract; The re-dissolved high-catechin tea extract is adsorbed by a macroporous resin, and then the macroporous resin is eluted. After removing the solvent in the eluent, the low-caffeine high-catechin tea extract can be obtained.

5. A method for preparing the tea extract microcapsules according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: dissolving maltodextrin and / or gum arabic in water to obtain a wall material solution; S2: adding the tea extract with low caffeine and high catechins to the wall material solution of S1 under stirring; S3: drying and crushing the mixed solution to obtain the tea extract microcapsules.

6. The method for preparing tea extract microcapsules according to claim 5, characterized in that: In step S1, the mass ratio of maltodextrin to gum arabic is 1:0 or (0-6):

1.

7. The method for preparing tea extract microcapsules according to claim 5, characterized in that: In step S2, the mass ratio of the tea extract to the wall material is 1:(1-2).

8. The method for preparing tea extract microcapsules according to claim 5, characterized in that: In step S2, the stirring speed is 600-1000 rpm, and the stirring time is 20-60 min.

9. The method for preparing tea extract microcapsules according to claim 5, characterized in that: In step S3, the drying is performed by freeze drying, and the drying time is 12-24 hours.

10. Use of the tea extract microcapsule according to any one of claims 1 to 4 in the preparation of instant tea, concentrated tea liquid, functional food and health food.

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