Black tea fermentation liquor and preparation method thereof

Abstract

The preparation method comprises the following steps: (1) fresh tea leaves, distilled water, glucose and protein are mixed, the mass content of the glucose is 10%-15%, the content of the protein is 0.5-1.0 g / L, and the pH value of the fermentation liquor is adjusted to 3.5-7.0; (2) after sterilization, inoculating 3%-5% of lactobacillus and 5%-15% of saccharomycetes to obtain a mixed fermentation suspension, and carrying out primary fermentation under a closed condition at the fermentation temperature of 25-30 DEG C; (3) secondary fermentation is carried out, the fermentation temperature is 23-27 DEG C, the secondary fermentation time is 5-10 h, and the oxygen introduction amount is 0.10-0.30 vvm; and (4) carrying out solid-liquid separation to remove insoluble fermentation products and plant residues so as to obtain the black tea fermentation liquor. The fermentation liquor prepared by the preparation method of the black tea fermentation liquor is obviously improved in the aspects of polysaccharide content, tea polyphenol content, amino acid content and the like, and the small molecule polysaccharide content is improved.

Description

Technical Field

[0001] The invention relates to the field of tea fermentation, and in particular to a black tea fermentation liquid and a preparation method thereof. Background Art

[0002] In addition to a large amount of tea polyphenols, tea also contains 20%-30% protein. During the processing of black tea, a chemical reaction centered on the enzymatic oxidation of tea polyphenols occurs. The chemical composition of the fresh leaves changes greatly, with tea polyphenols reduced by more than 90%, and new ingredients such as theaflavins and thearubigins produced. Therefore, the aroma substances are significantly increased compared to fresh leaves, and it has the characteristics of black tea, red soup, red leaves, and sweet and mellow taste.

[0003] In the prior art, fermented black tea is used to improve the umami taste, and the main component of umami taste is amino acid. Although the prior art fermentation increases the content of amino acids, it reduces the content of components such as polysaccharides and polyphenols, resulting in the weakening of the antioxidant, anti-aging, and vasodilation effects of black tea. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a black tea fermentation liquid and a preparation method thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing black tea fermentation liquid, the preparation method comprising the following steps: (1) mixing fresh tea leaves, distilled water, glucose and protein, wherein the mass content of glucose is 10% to 15%, the content of protein is 0.5 to 1.0 g / L, and the pH of the fermentation liquid is adjusted to 3.5 to 7.0;

[0006] (2) after sterilization, inoculating 3% to 5% of lactobacillus and 5% to 15% of yeast to obtain a mixed fermentation suspension, and performing a first fermentation under closed conditions at a fermentation temperature of 25 to 30° C. for a fermentation time of 45 to 75 h;

[0007] (3) performing a second fermentation at a temperature of 23 to 27° C. for 5 to 10 hours, with an oxygen flow rate of 0.10 to 0.30 vvm, and the temperature of the second fermentation being lower than that of the first fermentation;

[0008] (4) Solid-liquid separation to remove insoluble fermentation products and plant residues.

[0009] The method for preparing the black tea fermentation liquid comprises the following steps: mixing fresh tea leaves, distilled water, glucose and protein in proportion, and inoculating lactobacillus and yeast for fermentation at the same time; controlling the content of glucose and protein in the fermentation liquid, and successively performing secondary fermentation, controlling the temperature of the two fermentations, and controlling the oxygen flow rate of the second fermentation chamber to be 0.10-0.30 vvm; and preventing the loss and consumption of polysaccharide and polyphenol components by the mixed fermentation of lactobacillus and yeast in the above process. The fermentation liquid prepared by the method for preparing the black tea fermentation liquid has obvious improvements in polysaccharide content, tea polyphenol content, amino acid content, etc., and also improves the content of small molecule polysaccharides.

[0010] Preferably, in step (1), the material-liquid ratio of the fermentation liquid obtained by mixing fresh tea leaves with distilled water, glucose and protein is 5 to 10:20 (g:mL) calculated on a dry basis.

[0011] The method for preparing the black tea fermentation liquid reduces the consumption and loss of polysaccharide content, tea polyphenol content and amino acid content by controlling the material-liquid ratio of fresh tea leaves to fermentation liquid.

[0012] Preferably, the inoculation ratio of the lactobacillus to the yeast is 1:(1.5-2.5).

[0013] The preparation method of the black tea fermentation liquid and the inoculation ratio of lactobacillus and yeast are conducive to a better fermentation effect of the two strains, and the fermentation liquid has higher polysaccharide content, tea polyphenol content and amino acid content.

[0014] Preferably, the inoculation ratio of the lactobacillus to the yeast is 1:(1.8-2.2).

[0015] Preferably, the protein is whey protein or soy protein.

[0016] Preferably, in step (1), the pH of the fermentation broth is adjusted to 5.0-6.5.

[0017] Preferably, in step (1), the mass content of glucose is 12% to 14%, and the mass content of protein is 0.6 to 0.8 g / L.

[0018] Preferably, in step (3), the oxygen flow rate is 0.15 to 0.25 vvm.

[0019] Preferably, the lactobacillus is Lactobacillus kefir and the yeast is Saccharomyces cerevisiae.

[0020] The yeast is Saccharomyces cerevisiae, which is from Guangdong Culture Collection Center and has a collection number of GDMCC 2.110; the lactobacillus is Lactobacillus kefiri, which is from Guangdong Culture Collection Center and has a collection number of GDMCC 1.378.

[0021] The present invention also provides a black tea fermentation liquid prepared by any of the above-mentioned methods for preparing the black tea fermentation liquid.

[0022] The beneficial effects of the present invention are as follows: the present invention provides a black tea fermentation liquid and a preparation method thereof. The preparation method of the black tea fermentation liquid of the present invention comprises the following steps: mixing fresh tea leaves, distilled water, glucose and protein in proportion, and simultaneously inoculating lactobacillus and yeast for fermentation; controlling the content of glucose and protein in the fermentation liquid, and successively performing secondary fermentation, controlling the temperature of the two fermentations, and controlling the oxygen flow rate of the second fermentation chamber to be 0.10-0.30 vvm; and preventing the loss and consumption of polysaccharide and polyphenol components through the mixed fermentation of lactobacillus and yeast in the above process. The fermentation liquid prepared by the preparation method of the black tea fermentation liquid has obvious improvements in terms of polysaccharide content, tea polyphenol content, amino acid content, etc., and also improves the content of small molecule polysaccharides. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The polysaccharide molecular weight distribution chromatograms of the black tea fermentation liquid prepared by the black tea fermentation liquid and the preparation method thereof of the embodiments and comparative examples of the present invention are shown. DETAILED DESCRIPTION

[0024] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1

[0026] A method for preparing a black tea fermented liquid according to an embodiment of the present invention comprises the following steps:

[0027] (1) fresh tea leaves, distilled water, glucose and protein are mixed, wherein the mass content of glucose is 12.5% ​​and the mass content of protein is 0.75 g / L, and the pH of the fermentation liquid is adjusted to 6.0; the material-liquid ratio of the fermentation liquid obtained by mixing the fresh tea leaves with the distilled water, glucose and protein is 7.5:20 (g:mL) calculated on a dry basis;

[0028] (2) After sterilization, 4% lactobacillus and 8% yeast were inoculated to obtain a mixed fermentation suspension, and the first fermentation was carried out under closed conditions at a fermentation temperature of 27° C. and a fermentation time of 60 h; the yeast was Saccharomyces cerevisiae, which was obtained from Guangdong Culture Collection Center and has a collection number of GDMCC 2.110; the lactobacillus was Lactobacillus kefiri, which was obtained from Guangdong Culture Collection Center and has a collection number of GDMCC 1.378;

[0029] (3) performing a second fermentation at a temperature of 25° C. for 8 h and an oxygen flow rate of 0.20 vvm; the temperature of the second fermentation is lower than that of the first fermentation;

[0030] (4) Solid-liquid separation to remove insoluble fermentation products and plant residues to obtain black tea fermentation liquid.

[0031] Example 2

[0032] As a method for preparing a black tea fermentation liquid according to an embodiment of the present invention, the only difference between this embodiment and embodiment 1 is that after sterilization, 4% lactobacillus and 5% yeast are inoculated.

[0033] Example 3

[0034] As a method for preparing a black tea fermentation liquid according to an embodiment of the present invention, the only difference between this embodiment and embodiment 1 is that after sterilization, 3% of lactobacillus and 10% of yeast are inoculated.

[0035] Example 4

[0036] As a method for preparing a black tea fermentation broth according to an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the material-liquid ratio of the fermentation broth obtained by mixing fresh tea leaves with distilled water, glucose and protein calculated on a dry basis is 10:20 (g:mL).

[0037] Example 5

[0038] As a method for preparing a black tea fermentation broth according to an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the material-liquid ratio of the fermentation broth obtained by mixing fresh tea leaves with distilled water, glucose and protein calculated on a dry basis is 5:20 (g:mL).

[0039] Comparative Example 1

[0040] A method for preparing a black tea fermentation liquid as a comparative example of the present invention comprises the following steps:

[0041] (1) fresh tea leaves, distilled water, glucose and protein are mixed, wherein the mass content of glucose is 12.5% ​​and the mass content of protein is 0.75 g / L, and the pH of the fermentation liquid is adjusted to 6.0; the material-liquid ratio of the fermentation liquid obtained by mixing the fresh tea leaves with the distilled water, glucose and protein is 7.5:20 (g:mL) calculated on a dry basis;

[0042] (2) After sterilization, 4% lactobacillus and 8% yeast were inoculated to obtain a mixed fermentation suspension, and a fermentation was performed under closed conditions at a temperature of 27° C. for 68 h; the yeast was Saccharomyces cerevisiae, which was obtained from Guangdong Culture Collection Center and has a collection number of GDMCC 2.110; the lactobacillus was Lactobacillus kefiri, which was obtained from Guangdong Culture Collection Center and has a collection number of GDMCC 1.378;

[0043] (3) Solid-liquid separation to remove insoluble fermentation products and plant residues to obtain black tea fermentation liquid.

[0044] Comparative Example 2

[0045] A method for preparing a black tea fermentation liquid as a comparative example of the present invention comprises the following steps:

[0046] (1) fresh tea leaves, distilled water, glucose and protein are mixed, wherein the mass content of glucose is 12.5% ​​and the mass content of protein is 0.75 g / L, and the pH of the fermentation liquid is adjusted to 6.0; the material-liquid ratio of the fermentation liquid obtained by mixing the fresh tea leaves with the distilled water, glucose and protein is 7.5:20 (g:mL) calculated on a dry basis;

[0047] (2) After sterilization, 4% lactobacillus and 8% yeast were inoculated to obtain a mixed fermentation suspension, and a fermentation was performed under closed conditions at a temperature of 25° C., a fermentation time of 68 h, an oxygen flow rate of 0.20 vvm, the yeast was Saccharomyces cerevisiae, obtained from Guangdong Culture Collection Center, with a deposit number of GDMCC 2.110; the lactobacillus was Lactobacillus kefiri, obtained from Guangdong Culture Collection Center, with a deposit number of GDMCC 1.378;

[0048] (3) Solid-liquid separation to remove insoluble fermentation products and plant residues to obtain black tea fermentation liquid.

[0049] Comparative Example 3

[0050] As a method for preparing a black tea fermentation broth as a comparative example of the present invention, the only difference between this comparative example and Example 1 is that the material-liquid ratio of the fermentation broth obtained by mixing fresh tea leaves with distilled water, glucose and protein calculated on a dry basis is 2:20 (g:mL).

[0051] Comparative Example 4

[0052] As a method for preparing a black tea fermentation broth as a comparative example of the present invention, the only difference between this comparative example and Example 1 is that the material-liquid ratio of the fermentation broth obtained by mixing fresh tea leaves with distilled water, glucose and protein calculated on a dry basis is 20:20 (g:mL).

[0053] Experimental methods

[0054] 1. Sample to be tested.

[0055] The black tea fermentation liquid was prepared according to the preparation methods of the black tea fermentation liquid of Examples 1-5 and Comparative Examples 1-4, respectively.

[0056] The black tea fermentation liquid obtained in step (4) of Examples 1-5 and Comparative Examples 3-4 was used as a sample for detection.

[0057] 2. Polysaccharide content detection method

[0058] Use a pipette to accurately draw a certain volume of the sample to be tested, add water to make up to 2 ml, and at the same time accurately measure 2 ml of water into another stoppered test tube as a blank control. Add 1 ml of 5% phenol solution (freshly prepared) and shake well, quickly add 5.0 ml of concentrated sulfuric acid, shake well immediately, and place in a 40°C water bath for 30 minutes, take out and place in an ice water bath for 5 minutes. Use the blank prepared with the above 2.0 ml of water as a reference, measure the absorbance at a wavelength of 489 nm, establish a standard curve, and obtain the polysaccharide content.

[0059] 3. Tea polyphenols content detection

[0060] Ultraviolet (tea polyphenols and ferrous ions produce purple-blue complexes), ferrous tartrate colorimetric method - using the phenol oxygen anions of tea polyphenols to complex with metal ions to develop color and measure the tea polyphenol content.

[0061] Reagents:

[0062] (1) Ferric tartrate solution: 1 g of ferrous sulfate (FeSO4·7H2O) + 5 g of potassium sodium tartrate (KNaC4H4O6·4H2O), dilute with water to 1 L.

[0063] (2) pH-7.5 phosphate buffer

[0064] Method steps: (wavelength 540nm, reagent blank as reference)

[0065] Standard solution: weigh 0.25g of pure tea polyphenols, dilute to 250mL with water, concentration 1mg / mL

[0066] Draw a calibration curve: transfer 0.0mL; 0.5mL; 1.0mL; 1.5mL; 2.0mL respectively into a 25mL brown volumetric flask, add water to 5mL each, then add 5mL of ferric tartarate solution and dilute to the scale with pH-7.5 phosphate buffer.

[0067] 1 mL of sample, add 4 mL of water, then add 5 mL of ferric tartrate solution, and dilute to scale with pH-7.5 phosphate buffer. Detect absorbance at a wavelength of 540 nm.

[0068] 4. Amino acid content detection

[0069] Ninhydrin colorimetry / spectrophotometry, in accordance with GB / T 8314-2013 “Determination of total free amino acids in tea”.

[0070] The experimental results of the contents of polysaccharides, tea polyphenols and amino acids in black tea fermentation broth are shown in Table 1.

[0071] Table 1 Contents of polysaccharides, tea polyphenols and amino acids in black tea fermentation broth

[0072] sample Polysaccharide % (w / w) <![CDATA[Tea polyphenols 10 -3 (w / w)]]> Amino Acid % (w / w) Example 1 2.96 3.94 1.65 Example 2 2.61 3.50 1.51 Example 3 2.59 3.45 1.46 Example 4 2.83 3.765 1.59 Example 5 2.74 3.60 1.57 Comparative Example 1 1.86 3.16 1.05 Comparative Example 2 1.78 2.38 1.23 Comparative Example 3 2.24 2.94 1.25 Comparative Example 4 2.38 3.16 1.35

[0073] As can be seen from Table 1, the polysaccharide content, tea polyphenol content, amino acid content, etc. of the fermentation liquid prepared by the above-mentioned method for preparing black tea fermentation liquid are significantly improved.

[0074] 5. Determination of molecular weight distribution of polysaccharides.

[0075] (1) Preparation of Reference Solution Weigh 40 mg of dextran reference substances of different molecular weights and add distilled water to prepare a standard solution with a dextran concentration of 8 g / L. Filter the solution using a 0.22 μm microporous filter membrane for later use.

[0076] (2) Chromatographic conditions

[0077] Chromatographic column: TSK-gel G3000 PWXL (300mm×7.8mm, 7μm) and TSK-gel G5000PWXL (300mm×7.8mm, 10μm) high-efficiency gel permeation chromatography columns connected in series; same-type guard column; mobile phase: pure water, flow rate of 0.5mL / min; column temperature of 35℃, evaporative light scattering detector gain value of 6, injection volume of 50μL.

[0078] The samples of Example 1, Comparative Example 1 and Comparative Example 2 were tested for polysaccharide molecular weight distribution. The experimental results are as follows: Figure 1 As shown. Figure 1 It can be seen that Figure 1a is the black tea fermentation liquid of Example 1, Figure 1 b is the black tea fermentation liquid of Comparative Example 1, Figure 1 c is the black tea fermentation liquid of comparative example 2. The method for preparing the black tea fermentation liquid of the present invention comprises mixing fresh tea leaves, distilled water, glucose and protein in proportion, and simultaneously inoculating lactobacillus and yeast for fermentation, controlling the content of glucose and protein in the fermentation liquid, and successively performing secondary fermentation, controlling the temperature of the two fermentations, and controlling the oxygen flow rate of the second fermentation chamber to be 0.10-0.30 vvm, and increasing the content of small molecule polysaccharides through the mixed fermentation of lactobacillus and yeast in the above process.

[0079] 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 the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing black tea fermentation liquid, characterized in that: The preparation method comprises the following steps: (1) fresh tea leaves, distilled water, glucose and protein are mixed, wherein the mass content of glucose is 10% to 15%, the mass content of protein is 0.5 to 1.0 g / L, and the pH of the fermentation liquid is adjusted to 3.5 to 7.0; (2) after sterilization, inoculating 3% to 5% of lactobacillus and 5% to 15% of yeast to obtain a mixed fermentation suspension, and performing a first fermentation under closed conditions at a fermentation temperature of 25 to 30° C. for a fermentation time of 45 to 75 h; (3) performing a second fermentation at a temperature of 23 to 27° C. for 5 to 10 hours, with an oxygen flow rate of 0.10 to 0.30 vvm, and the temperature of the second fermentation being lower than that of the first fermentation; (4) Solid-liquid separation to remove insoluble fermentation products and plant residues.

2. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: In step (1), the material-liquid ratio of the fermentation liquid obtained by mixing fresh tea leaves with distilled water, glucose and protein is 5 to 10:20 (g:mL) calculated on a dry basis.

3. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: The inoculation ratio of the lactobacillus to the yeast is 1:(1.5-2.5).

4. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: The inoculation ratio of the lactobacillus to the yeast is 1:(1.8-2.2).

5. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: The protein is whey protein or soy protein.

6. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: In step (1), the pH of the fermentation liquid is adjusted to 5.0-6.

5.

7. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: In step (1), the mass content of glucose is 12% to 14%, and the mass content of protein is 0.6 to 0.8 g / L.

8. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: In step (3), the oxygen flow rate is 0.15 to 0.25 vvm.

9. The method for preparing black tea fermentation liquid according to claim 1, characterized in that: The lactobacillus is Lactobacillus kefir and the yeast is Saccharomyces cerevisiae.

10. The black tea fermented liquid prepared by the method for preparing black tea fermented liquid according to any one of claims 1 to 9.

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