Fruit tea beverage rich in theaflavin and preparation method thereof

Abstract

The invention relates to the technical field of deep processing of agricultural products, in particular to a fruit tea beverage rich in theaflavin and a preparation method thereof.The preparation method comprises the following steps that green tea leaves are fully smashed and then dissolved in a buffer solution, catechin components are extracted under hot water bath, and green tea leaching liquor is obtained; the method comprises the following steps: dicing pears, adding the diced pears into a buffer solution, adding an antioxidant, homogenizing, refrigerating, filtering and centrifuging to obtain a polyphenol oxidase crude enzyme solution; filtering the green tea extract liquid, adding the polyphenol oxidase crude enzyme liquid, and carrying out enzymatic reaction under stirring to obtain a mixed liquid rich in theaflavin; selecting and adding fruit juice, then adding a sweetening agent, a sour regulator and an antioxidant, filtering, sterilizing and filling to obtain the fruit tea beverage rich in theaflavin. By adopting the steps, the green tea and the fruits which are low in price are used as raw materials, catechin in the green tea is oxidized by polyphenol oxidase of the fruits to synthesize the theaflavin, the concentration of the theaflavin is 160-180mg / L, and the content of the theaflavin is increased without additional addition, so that the cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of deep processing of agricultural products, in particular to a fruit tea beverage rich in theaflavins and a preparation method thereof. Background Art

[0002] Theaflavins are a class of mixtures with benzophenone structures, mainly formed by oxidative polycondensation of catechins and gallocatechins. Theaflavins exist in black tea, with a content of 0.3% to 1.5%. So far, 28 types of theaflavins have been found, among which the focus is on theaflavins 1, theaflavins 3-gallate, theaflavins 3′ gallate and theaflavins 3,3′ digallate. In recent years, with the in-depth study of theaflavins, its biological activity, medicinal value and health care functions have gradually been recognized and developed. It has been found that theaflavins have a variety of physiological effects, such as antioxidant, anti-depressant, anti-inflammatory, anti-cancer, anti-obesity, anti-viral, anti-metabolic syndrome and anti-gout.

[0003] However, the content of theaflavins in black tea and oolong tea beverages is extremely low, and it is difficult to achieve the above physiological effects by drinking black tea beverages. At present, fruit tea beverages rich in theaflavins are mainly prepared by black tea concentrate or instant black tea powder with fruit juice concentrate or fruit essence, and additional food additives such as theaflavins. Fruit juice concentrate will lose some aromatic substances and flavor components during the processing process, reducing its nutritional value. The fruit flavor in the beverage is difficult to blend with the tea aroma, resulting in poor flavor quality and rough taste of the beverage.

[0004] Among the currently reported technologies, the extraction methods of theaflavins are relatively complicated, including hot water extraction and organic solvent extraction. Hot water extraction is simple to operate, but has low efficiency and low purity; organic solvent extraction can obtain high-purity theaflavins, but there are safety hazards, and the solvent removal process is complicated and costly. In vitro synthesis is currently the most environmentally friendly method. Based on the "catechin → quinone → theaflavins" pathway, the mass production of theaflavins is achieved through chemical oxidation or enzymatic synthesis. However, the enzyme source extraction of enzymatic synthesis is complicated, and exogenous enzymes from microorganisms may bring safety hazards. At the same time, there are many by-products, which reduces the synthesis efficiency.

[0005] CN104651426A discloses a method for enzymatically synthesizing theaflavins TF using tea polyphenol oxidase isozyme PPO1. The method uses tea polyphenol oxidase isozyme PPO1 as an enzyme source and catechin EC and EGC components in tea polyphenols as main reaction substrates to enzymatically synthesize a single theaflavins component TF1. However, the method significantly increases the oxidation byproducts of catechins, resulting in a decrease in the synthesis yield of theaflavins compounds. In addition, the extraction and purification process of tea polyphenol oxidase isozyme PPO1 is complex and costly.

[0006] CN102640824B discloses a method for processing a high-theaflavins black tea beverage, which uses green tea and fresh fruit as raw materials, and finally obtains a black tea beverage with a theaflavins content of about 80 mg / L through fermentation, filtration, batching, sterilization, canning and other processes. However, compared with the fruit tea beverage prepared by this method, its theaflavins content is lower, and the conversion efficiency of tea polyphenols in the tea soup is not high.

[0007] It can be seen that the current cost of synthesizing theaflavins by enzymatic reaction is high and the theaflavins content is low, which limits the widespread promotion and market consumption of theaflavins-rich fruit tea beverages. Summary of the invention

[0008] The purpose of the present invention is to provide a fruit tea beverage rich in theaflavins and a preparation method thereof, which uses cheap green tea and fruit as raw materials, utilizes the polyphenol oxidase of the fruit itself to oxidize catechins in green tea to synthesize theaflavins, and does not increase the theaflavins content by additional addition, thereby greatly reducing costs.

[0009] To achieve the above object, the present invention provides a method for preparing a fruit tea beverage rich in theaflavins, comprising the following steps:

[0010] S1, fully crushing the green tea leaves and dissolving them in a buffer solution, extracting catechin components in a hot water bath to obtain a green tea extract;

[0011] S2, cutting the pear into pieces and adding them into a buffer solution, adding an antioxidant and then homogenizing and refrigerating, filtering and centrifuging to obtain a crude polyphenol oxidase enzyme solution;

[0012] S3, filtering the green tea extract in S1 and adding the crude polyphenol oxidase enzyme solution in S2, stirring to carry out enzymatic reaction to obtain a mixed solution rich in theaflavins;

[0013] S4, adding fruit juice to the mixed solution rich in theaflavins in S3, and then adding sweetener, acidity regulator and antioxidant, filtering, sterilizing and then filling to obtain a fruit tea beverage rich in theaflavins.

[0014] Preferably, in S1, the solid-liquid ratio of green tea leaves to buffer solution is 1 g:40-60 mL, and the extraction is carried out in a hot water bath at 80-90° C. for 15-20 min, with stirring every 5-6 min.

[0015] More preferably, in S1, the solid-liquid ratio of green tea leaves to buffer solution is 1 g:50 mL.

[0016] In S1 of the present invention, the mass volume concentration of catechins in the green tea extract is 1.3-1.6 g / L. The extracted catechins include epicatechin EC, epigallocatechin EGC, epigallocatechin gallate EGCG and epicatechin gallate ECG, and the ratio of the four in the green tea extract is 5-6:2-3:8-9:1.

[0017] Preferably, in S2, the pear is one or more of Fengshui pear and Xueli pear.

[0018] Preferably, in S2, the solid-liquid ratio of pear to buffer solution is 1 g:1-1.5 mL.

[0019] Preferably, in S2, the antioxidant includes one or more of ascorbic acid and ethylenediaminetetraacetic acid.

[0020] Preferably, in S2, the centrifugation speed is 8000-10000 r / min, and the centrifugation time is 20-30 min.

[0021] Preferably, in S2, the filtering is performed using a filter bag with a mesh size of 400 and filtering for 1 to 2 times.

[0022] In S2 of the present invention, air is used as the oxygen source for the enzymatic reaction, and the enzyme activity of the crude polyphenol oxidase solution is 420-460 U / mL.

[0023] Preferably, in S1 and S2, the buffer solution is a phosphate buffer.

[0024] More preferably, the phosphate buffer is a citric acid-disodium hydrogen phosphate buffer.

[0025] Preferably, in S3, the enzymatic reaction is carried out by stirring at 400-600 rpm at 25-45°C for 20-60 min.

[0026] In S3 of the present invention, the mass volume concentration of the remaining catechins in the theaflavins-rich mixed solution is 200 to 400 mg / L.

[0027] Preferably, in S4, the fruit juice includes one or more of apple juice, orange juice, lychee juice, mango juice, grape juice and passion fruit juice.

[0028] In S4 of the present invention, the mass volume concentration of theaflavins in the fruit tea beverage rich in theaflavins is 160-180 mg / L. Theaflavins (TFs) include theaflavins 1 (TF), theaflavins 3-gallate (TF3G), theaflavins 3′gallate (TF3′G), and theaflavins 3,3′digallate (TFDG).

[0029] Preferably, in S4, the content of fruit juice in the theaflavins-rich fruit tea beverage is greater than 10%.

[0030] The theaflavins-rich fruit tea beverage prepared by the method for preparing the theaflavins-rich fruit tea beverage has a mass volume concentration of theaflavins of 160-180 mg / L.

[0031] Therefore, the present invention adopts the above steps to provide a theaflavins-rich fruit tea beverage and a preparation method thereof, using low-grade green tea and cheap fruits as raw materials, utilizing the polyphenol oxidase of the fruit itself to oxidize the catechins in the green tea to synthesize theaflavins, and then mixing the ingredients according to the concentration ratio required for the fruit tea beverage, sterilizing and canning, so as to obtain a fruit tea beverage with a theaflavins content of 160-180 mg / L.

[0032] The fruit tea beverage provided by the invention fully integrates tea aroma and fruit aroma, has bright red color, pleasant flavor, and significantly better nutritional value and physiological efficacy than ordinary fruit tea beverages. It has a simple process, is green and environmentally friendly, and has low cost, thus providing a good foundation for marketization.

[0033] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a liquid chromatogram of catechins in the green tea extract in Example 1 of the present invention;

[0035] Figure 2 is a liquid chromatogram of theaflavins in the fruit tea beverage rich in theaflavins in Example 1 of the present invention;

[0036] Figure 3 is an enzyme kinetic curve diagram of the crude enzyme solution polyphenol oxidase in Example 1 of the present invention;

[0037] Figure 4 is a curve diagram of theaflavin concentration under different enzyme addition amounts of the present invention;

[0038] Figure 5 is a curve diagram of theaflavin concentrations at different reaction times of the present invention;

[0039] Figure 6 It is a curve diagram of theaflavin concentration at different reaction temperatures of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features or features mentioned in the specific examples mentioned in the present invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0041] Example 1

[0042] A method for preparing a fruit tea beverage rich in theaflavins comprises the following steps:

[0043] S1. Dry the green tea leaves at 40°C and crush them fully. After passing through an 80-mesh sieve, place them in a dry place away from light. Dissolve 5.0 g of green tea powder in 250 mL of citric acid-sodium hydrogen phosphate buffer with a pH of 5.4. Extract the catechin components in a hot water bath at 90°C. Stir once every 5 minutes. After 15 minutes, filter with 400-mesh gauze. Cool the green tea extract to room temperature and set aside. The HPLC chromatogram of catechins (EC, EGC, EGCG and ECG) in the green tea extract is as follows: Figure 1 shown.

[0044] S2. Cut 100 g of Fengshui pear into pieces, add 100 mL of pre-cooled citric acid-disodium hydrogen phosphate buffer with a pH of 5.4, add antioxidants (0.2 g of ascorbic acid and 0.029 g of ethylenediaminetetraacetic acid) and 1 g of cross-linked polyvinyl pyrrolidone, homogenize for 5 minutes (3 minutes + 2 minutes in two times, stopping for 5 minutes in between), then refrigerate and extract at 4°C for 12 hours, filter through four layers of gauze, and centrifuge at 4°C and 8000 r / min for 30 minutes to obtain the supernatant as the crude polyphenol oxidase enzyme solution.

[0045] S3. Add 50 mL of the green tea extract filtered in S1 to 50 mL of the crude polyphenol oxidase solution in S2, and perform enzymatic reaction for 30 min under magnetic stirring at a temperature of 25° C. and a rotation speed of 600 rpm to obtain a mixed solution rich in theaflavins.

[0046] S4, the mixed solution rich in theaflavins in S3 is centrifuged and filtered through a 0.5 μm microfiltration membrane, and then sweeteners (white sugar and fructose syrup), acidity regulators such as citric acid, sodium hydroxymethyl cellulose, sodium hexametaphosphate, edible flavors and antioxidants (ascorbic acid) are added, filtered, sterilized and then bottled to obtain a fruit tea beverage rich in theaflavins, wherein the liquid chromatogram of theaflavins is as follows: Figure 2 shown.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is that the fruit juice added in S4 is orange juice, the orange juice and the mixed solution rich in theaflavins are mixed in a ratio of 1:10, centrifuged and filtered through a 0.5 μm microfiltration membrane, and the rest of the steps are the same as those in embodiment 1.

[0049] Test Example 1

[0050] a. Polyphenol oxidase activity

[0051] The enzymatic activity of polyphenol oxidase in the crude polyphenol oxidase solution of S2 in Example 1 was tested.

[0052] Take 2.5mL of sodium hydrogen phosphate-citric acid buffer solution with a pH of 5.4 and 0.5mL of 0.01mol / L catechin, put them in a water bath at 25°C and keep the temperature constant. Finally, add 0.5mL of the crude polyphenol oxidase solution of S2 in Example 1, mix them evenly, and measure the change of absorbance at a wavelength of 420nm. Start timing after the crude polyphenol oxidase solution of S2 in Example 1 is added, record the change of absorbance every 30s, and use the straight line part of the activity curve as a time function to measure the size of the enzyme activity. The enzyme activity formula is as follows:

[0053] Enzyme activity (U)=(ΔA*K) / (0.001*v*t)

[0054] Where K is the dilution factor; v is the volume of the reaction enzyme solution in mL; t is the reaction time in min, and ΔA is the change in absorbance during the reaction time.

[0055] The calculated activity of the crude polyphenol oxidase solution of S2 in Example 1 is about 450 U / mL. The activity of the enzyme varies slightly depending on the maturity and origin of the Fengshui pear. The kinetic curve of the crude polyphenol oxidase solution of S2 in Example 1 is shown in FIG. Figure 3 .

[0056] b. Detection of theaflavin content in theaflavin-rich mixture

[0057] Sample pretreatment conditions refer to the detection method in GB / T 8318-2018 Determination of catechins and theaflavins in tea.

[0058] HPLC analysis conditions: the mobile phase was 0.2% acetic acid aqueous solution (A) and acetonitrile (B), linear gradient elution was used, column temperature was 35°C, flow rate was 1 mL / min, 0-12 min 10-13% B, 12-16 min 13-17% B, 16-22 min 17% B, 22-25 min 17-32% B, 25-32 min 32% B, 32-33 min 32-10% B, 33-40 min 10% B.

[0059] The injection volume was 10 μL, the UV detection wavelength was 278 nm, and the chromatographic column was Agilent ZORBAX SB-C18 (4.6×250 mm, 5 μm).

[0060] b1. Different dosage of crude polyphenol oxidase solution

[0061] 50 mL of the filtered green tea extract in Example 1S1 was added to 20 mL, 30 mL, 40 mL, 50 mL and 60 mL of the crude polyphenol oxidase enzyme solution in Example 1S2, respectively, and the enzymatic reaction was carried out for 30 min under magnetic stirring at 25°C and 600 rpm, and then placed in a microwave oven for 30 s to terminate the reaction, and the reaction solution was centrifuged at 12000 rpm for 10 min, and the supernatant was filtered using a 0.4 μm microfiltration membrane to obtain five mixed solutions rich in theaflavins. The five green tea extracts and the five mixed solutions rich in theaflavins were detected by HPLC.

[0062] Figure 4 The results showed that the concentration of theaflavins in green tea extract was 66.41 μg / mL, which increased to 188.25 μg / mL after adding 50 mL of crude polyphenol oxidase solution, increasing the theaflavins content in green tea extract from 0.3% to 1.9%. The total concentration of the four catechins in green tea extract was 1343.93 μg / mL, which decreased to 105.92 μg / mL after adding 60 mL of crude polyphenol oxidase solution, and the conversion rate reached 92.1%.

[0063] b2. Different reaction times

[0064] Measure five 50mL crude polyphenol oxidase enzyme solutions in Example 1 into 250mL triangular flasks, adjust the pH of the green tea extract in Example 1 to 5.4, and then add 50mL of green tea extract to each triangular flask. Place the triangular flask on a 25°C magnetic stirrer for stirring, take 20mL of the reaction solution in each triangular flask at 10min, 20min, 30min, 40min, and 50min of reaction, place it in a microwave oven for 30s to terminate the reaction. Centrifuge the reaction solution at 12000rpm for 10min to obtain a supernatant. Detect by HPLC, with an injection volume of 10μL and a detection wavelength of 278nm.

[0065] Depend on Figure 5 It can be seen that the concentration of theaflavins in the green tea extract is 66.41 μg / mL, which increases to 159.77 μg / mL after 30 minutes of reaction. The total concentration of the four catechins in the green tea extract is 1473.31 μg / mL, which decreases to 173.58 μg / mL after 30 minutes of reaction, and remains 80.34 μg / mL after 50 minutes of reaction, and the conversion rate reaches 94.5%.

[0066] b3. Different enzymatic reaction temperatures

[0067] Measure five 50 mL crude polyphenol oxidase enzyme solutions in Example 1 into a 250 mL triangular flask, adjust the pH of the green tea extract in Example 1 to 5.4, add 50 mL of green tea extract to the triangular flask respectively, stir and react at 25°C, 30°C, 35°C, 40°C, and 45°C for 40 min, take 20 mL of the reaction solution respectively, place it in a microwave oven for 30 s, terminate the reaction, centrifuge the reaction solution at 12000 rpm for 10 min, and obtain the supernatant. HPLC was used for detection, the injection volume was 10 μL, and the detection wavelength was 278 nm.

[0068] Depend on Figure 6 As shown in the figure, the concentration of theaflavins in the green tea extract was 59.47 μg / mL, which increased to 146.59 μg / mL after 30 min of reaction at 25°C. As the temperature increased, the amount of synthesized theaflavins gradually decreased. The total concentration of the four catechins in the green tea extract was 1329.41 μg / mL, which decreased to 165.4 μg / mL after 30 min of reaction at 25°C, and the conversion rate reached 87.56%.

[0069] Therefore, the present invention adopts the above steps to provide a fruit tea beverage rich in theaflavins and a preparation method thereof, using cheap green tea and fruit as raw materials, utilizing the polyphenol oxidase of the fruit itself to oxidize catechins in green tea to synthesize theaflavins, without increasing the content by additionally adding theaflavins, thereby greatly reducing costs.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a fruit tea beverage rich in theaflavins, characterized in that: The following steps are included: S1, fully crushing the green tea leaves and dissolving them in a buffer solution, extracting catechin components in a hot water bath to obtain a green tea extract; S2, cutting the pear into pieces and adding them into a buffer solution, adding an antioxidant and then homogenizing and refrigerating, filtering and centrifuging to obtain a crude polyphenol oxidase enzyme solution; S3, filtering the green tea extract in S1 and adding the crude polyphenol oxidase enzyme solution in S2, stirring to carry out enzymatic reaction to obtain a mixed solution rich in theaflavins; S4, adding fruit juice to the mixed solution rich in theaflavins in S3, and then adding sweetener, acidity regulator and antioxidant, filtering, sterilizing and then filling to obtain a fruit tea beverage rich in theaflavins.

2. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S1, the solid-liquid ratio of green tea leaves to buffer solution is 1 g:40-60 mL, and the hot water bath is at 80-90° C. for 15-20 min.

3. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S2, the pears include one or more of Fengshui pear and Xueli pear.

4. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S2, the solid-liquid ratio of pear to buffer solution is 1 g:1-1.5 mL.

5. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S2, the antioxidant includes one or more of ascorbic acid and ethylenediaminetetraacetic acid.

6. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S2, the centrifugation speed is 8000-10000 r / min, and the centrifugation time is 20-30 min.

7. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S1 and S2, the buffer solution is phosphate buffer.

8. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S3, the enzymatic reaction is carried out by stirring at 400-600 rpm at 25-45°C for 20-60 min.

9. The method for preparing a theaflavins-rich fruit tea beverage according to claim 1, characterized in that: In S4, the fruit juice includes one or more of apple juice, orange juice, lychee juice, mango juice, grape juice and passion fruit juice.

10. The fruit tea beverage rich in theaflavins prepared by the method for preparing a fruit tea beverage rich in theaflavins according to any one of claims 1 to 9, characterized in that: The mass volume concentration of theaflavins in theaflavin-rich fruit tea beverage is 160-180 mg / L.

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