Preparation method of cold-brewed tea

Abstract

The invention relates to the technical field of cold-brewed tea, in particular to a preparation method of cold-brewed tea. The invention provides a preparation method of cold-brewed tea, which comprises the following steps: mixing tea leaves with water to obtain a mixed solution of the tea leaves and the water; sequentially performing freeze thawing and ultrahigh pressure treatment on the mixed liquid of the tea leaves and the water to obtain the cold-brewed tea, the time of the preparation method is less than or equal to 6 hours.

Description

Technical Field

[0001] The present invention relates to the technical field of cold-brew tea, in particular to a preparation method of cold-brew tea. Background Art

[0002] Tea is rich in tea polyphenols, polysaccharides, amino acids, proteins, minerals, and various vitamins. It boasts a wealth of nutritional value and boasts health benefits such as lowering blood pressure and lipids, inhibiting bacteria, and boosting immunity, making it a "food and medicine" food. Hot brewing is the primary method for drinking tea. While hot water quickly releases most of the tea's beneficial compounds, high-temperature brewing can destroy some of the tea's nutrients, particularly antioxidants like tea polyphenols, which can be partially lost at high temperatures. Furthermore, due to the high temperature, tea is not suitable for immediate consumption, nor is it suitable for today's fast-paced lifestyle.

[0003] With the modern population's pursuit of health and the prevalence of fast-paced lifestyles, cold-brew tea meets the demand for convenient, healthy beverages. Cold-brew tea generally contains no stimulants and is low in caffeine, making it more suitable for those who prefer caffeine. The low-temperature steeping method minimizes the destruction of polyphenols in the tea leaves, preserving their aroma and flavor.

[0004] The traditional cold-brew tea production process involves soaking tea and water in appropriate proportions at low temperatures, and letting it sit for about 10 to 12 hours. Compared with the traditional hot-brew process, high temperature allows certain components in the tea leaves to be released more fully, while the release rate of cold-brewed tea is slower at low temperatures, resulting in a slower dissolution rate of tea contents such as tea polyphenols, free amino acids, caffeine, and flavonoids. This results in the production time of cold-brewed tea products being too long, making them unsuitable for industrial production. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide a method for preparing cold-brew tea, which solves the problem of long production time of cold-brew tea in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing cold-brewed tea, comprising the following steps:

[0008] Mixing tea leaves and water to obtain a tea leaves and water mixture;

[0009] The mixture of tea leaves and water is subjected to freeze-thaw and ultra-high pressure treatment in sequence to obtain the cold brew tea;

[0010] The preparation method takes ≤6 hours.

[0011] Preferably, the tea leaves include green tea, white tea, yellow tea, oolong tea, black tea or dark tea.

[0012] Preferably, the mass ratio of the tea leaves to water is 1:(100-200);

[0013] The temperature of the water is 4-10°C.

[0014] Preferably, the temperature of the mixture of tea leaves and water is 0-10°C.

[0015] Preferably, the freeze-thaw comprises sequential freezing and thawing;

[0016] The freezing temperature is -10 to -20°C, and the freezing time is 60 to 120 minutes.

[0017] Preferably, the pressure of the ultrahigh pressure treatment is 200-600 MPa.

[0018] Preferably, the ultrahigh pressure treatment time is 5 to 15 minutes.

[0019] Preferably, the pressure of the ultrahigh pressure treatment is 600 MPa and the time is 5 minutes.

[0020] Preferably, the cold brew tea is stored in a refrigerated manner.

[0021] Preferably, the temperature of the refrigeration treatment is 0-4°C.

[0022] The present invention provides a method for preparing cold-brewed tea, comprising the following steps: mixing tea leaves and water to obtain a mixture of tea leaves and water; sequentially subjecting the mixture of tea leaves and water to freeze-thawing and ultrahigh pressure treatment to obtain the cold-brewed tea; the preparation time of the method is ≤6 hours. The freeze-thawing method employed in the present invention can rupture the cell walls of the tea leaves, increasing the permeability of the cell walls, thereby increasing the dissolution rate of the cold-brewed tea contents, shortening the processing time of the cold-brewed tea, saving production costs of the cold-brewed tea, and facilitating industrial production. Furthermore, the ultrahigh pressure treatment allows water molecules to penetrate the interior of the tea leaves more quickly and achieves more uniform extraction, effectively releasing multiple active ingredients in the tea leaves, improving extraction efficiency, shortening the low-temperature soaking time, and improving the product quality of the cold-brewed tea. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing cold-brewed tea, comprising the following steps:

[0024] Mixing tea leaves and water to obtain a tea leaves and water mixture;

[0025] The mixture of tea leaves and water is subjected to freeze-thaw and ultra-high pressure treatment in sequence to obtain the cold brew tea;

[0026] The preparation method takes ≤6 hours.

[0027] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0028] The invention mixes tea leaves and water to obtain a mixed liquid of tea leaves and water.

[0029] In the present invention, the tea preferably includes green tea, white tea, yellow tea, oolong tea, black tea, or dark tea. The present invention does not have any particular limitation on the type of the green tea, white tea, yellow tea, oolong tea, black tea, or dark tea, and any type well known to those skilled in the art can be used. In an embodiment of the present invention, the tea is specifically Longjing (green tea).

[0030] Before the mixing, the present invention preferably pre-treats the tea leaves, and the pre-treatment preferably removes tea leaves that are moldy or discolored.

[0031] In the present invention, the water is preferably mineral water. In an embodiment of the present invention, the mineral water is specifically Wahaha mineral water.

[0032] In the present invention, the mass ratio of the tea leaves to water is preferably 1:(100-200), more preferably 1:100, 1:120, 1:140, 1:160, 1:180 or 1:200. In an embodiment of the present invention, the mass ratio of the tea leaves to water can be 1:200.

[0033] In the present invention, the temperature of the water is preferably 4-10° C., more preferably 4° C., 5° C., 6° C., 7° C., 8° C., 9° C. or 10° C. In an embodiment of the present invention, the temperature of the water may be 4° C.

[0034] The present invention does not have any special limitation on the mixing process, and the mixing process may be carried out using a process well known to those skilled in the art.

[0035] In the present invention, the temperature of the mixture of tea leaves and water is preferably 0-10° C., more preferably 0° C., 1° C., 2° C., 3° C., 4° C., 5° C., 6° C., 7° C., 8° C., 9° C. or 10° C. In an embodiment of the present invention, the temperature of the mixture of tea leaves and water may be 4° C.

[0036] After obtaining the mixture of tea leaves and water, the present invention sequentially performs freeze-thaw and ultra-high pressure treatment on the mixture of tea leaves and water to obtain the cold-brewed tea.

[0037] In the present invention, the freeze-thaw preferably includes sequential freezing and thawing, and the freezing temperature is preferably -10 to -20°C, more preferably -10°C, -11°C, -12°C, -13°C, -14°C, -15°C, -16°C, -17°C, -18°C, -19°C or -20°C. In an embodiment of the present invention, the freezing temperature may be -20°C.

[0038] In the present invention, the freezing time is preferably 60 to 120 minutes, more preferably 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes or 120 minutes. In an embodiment of the present invention, the freezing time can be 2 hours.

[0039] In the present invention, the melting is preferably carried out at room temperature, and the melting time is preferably 120 to 180 minutes, more preferably 120 minutes, 130 minutes, 140 minutes, 150 minutes, 160 minutes, 170 minutes or 180 minutes. In an embodiment of the present invention, the melting time can be 120 minutes.

[0040] In the present invention, the pressure of the ultrahigh pressure treatment is preferably 200-600 MPa, more preferably 200 MPa, 300 MPa, 400 MPa, 500 MPa or 600 MPa. In an embodiment of the present invention, the pressure of the ultrahigh pressure treatment can be 200 MPa, 300 MPa, 400 MPa, 500 MPa or 600 MPa.

[0041] In the present invention, the ultrahigh pressure treatment time is preferably 5 to 15 minutes, more preferably 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes. In an embodiment of the present invention, the ultrahigh pressure treatment time can be 5 minutes.

[0042] In the present invention, the cold brew tea is preferably stored in a refrigerated manner, and the temperature of the refrigerated storage is preferably 0-4°C.

[0043] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] Example 1

[0045] The Longjing tea was first coarsely screened to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4° C.) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0046] The mixture of tea leaves and water at 4°C was frozen (-20°C) for 2 hours, taken out, and allowed to melt at room temperature (for 120 minutes). The melted mixture of tea leaves and water was then subjected to ultrahigh pressure treatment (200 MPa, 5 minutes) to obtain a finished cold-brewed tea (stored at 4°C).

[0047] Example 2

[0048] The Longjing tea was first coarsely sieved to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4°C) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0049] The mixture of tea leaves and water at 4°C was frozen (-20°C) for 2 hours, taken out, and allowed to melt at room temperature (for 120 minutes). The melted mixture of tea leaves and water was then subjected to ultrahigh pressure treatment (300 MPa, 5 minutes) to obtain a finished cold-brewed tea (stored at 4°C).

[0050] Example 3

[0051] The Longjing tea was first coarsely screened to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4° C.) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0052] The mixture of tea leaves and water at 4°C was frozen (-20°C) for 2 hours, taken out, and allowed to melt at room temperature (for 120 minutes). The melted mixture of tea leaves and water was then subjected to ultrahigh pressure treatment (400 MPa, 5 minutes) to obtain a finished cold-brewed tea (stored at 4°C).

[0053] Example 4

[0054] The Longjing tea was first coarsely sieved to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4°C) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0055] The mixture of tea leaves and water at 4°C was frozen (-20°C) for 2 hours, taken out, and allowed to melt at room temperature (for 120 minutes). The melted mixture of tea leaves and water was then subjected to ultrahigh pressure treatment (500 MPa, 5 minutes) to obtain a finished cold-brewed tea (stored at 4°C).

[0056] Example 5

[0057] The Longjing tea was first coarsely screened to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4° C.) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0058] The mixture of tea leaves and water at 4°C was frozen (-20°C) for 2 hours, taken out, and allowed to melt at room temperature (for 120 minutes). The melted mixture of tea leaves and water was then subjected to ultrahigh pressure treatment (600 MPa, 5 minutes) to obtain a finished cold-brewed tea (stored at 4°C).

[0059] Comparative Example 1

[0060] The Longjing tea was first coarsely sieved to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4°C) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0061] The mixture of tea leaves and water at 4° C. was allowed to stand for 12 hours to obtain a finished cold-brewed tea (stored in an environment of 4° C.).

[0062] Comparative Example 2

[0063] The Longjing tea was first coarsely screened to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4° C.) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0064] The mixture of tea leaves and water at 4° C. was subjected to ultrahigh pressure treatment (200 MPa, 5 min) to obtain a finished cold-brewed tea product (stored in an environment of 4° C.).

[0065] Comparative Example 3

[0066] The Longjing tea was first coarsely sieved to remove the moldy and discolored Longjing tea, and then mixed with Wahaha mineral water (water temperature was 4°C) at a mass ratio of 1:200 to obtain a mixture of tea leaves and water;

[0067] The mixture of tea leaves and water at 4° C. was frozen (-20° C.) for 2 h, taken out, and allowed to thaw at room temperature (for 120 min) to obtain a finished cold-brewed tea (stored at 4° C.).

[0068] Test Case

[0069] According to the national standard GB / T 8313-2018 for the detection of tea polyphenols and catechins in tea, the tea polyphenols in the finished cold-brewed tea products described in Examples 1 to 5 and Comparative Examples 1 to 3 were tested. The specific process was as follows: first, a standard curve was prepared using gallic acid. Then, 1.0 mL of the test solution (the finished cold-brewed tea products described in Examples 1 to 5 and Comparative Examples 1 to 3) was added with 5.0 mL of a 10% mass concentration of folin phenol reagent, the mixture was shaken and reacted for 3 to 8 minutes, a 7.5% mass concentration of sodium carbonate solution was added, water was added to the volume, the mixture was shaken, and the mixture was allowed to stand at room temperature for 60 minutes. The absorbance was measured using a spectrophotometer at a wavelength of 765 nm using a 10 mm cuvette.

[0070] The caffeine test method in the finished cold-brew tea products described in Examples 1 to 5 and Comparative Examples 1 to 3 was as follows: Chromatographic conditions: Chromatographic column: C18 chromatographic column (2.1 mm × 100 mm, 2.2 μm); Mobile phase: A: methanol, B: water; Gradient elution program: 0.0 min, 30% A, 3.0 min, 25% A, program linearly decreasing, 25% A maintained until 5.0 min, A restored to 30% at 6.0 min, program linearly increasing, 30% A maintained until 8.0 min; Flow rate: 0.20 mL min -1 ; Injection volume: 2μL; Detection wavelength: 270nm; Accurately aspirate 2μL of test solution, inject it into the high performance liquid chromatograph, and use the caffeine standard solution to prepare a standard curve for chromatographic determination.

[0071] The free amino acids in the finished cold-brewed teas described in Examples 1-5 and Comparative Examples 1-3 were tested according to the method for determining the total free amino acids in tea (GB / T 8314-87): a standard curve was prepared using glutamic acid. 1.0 mL of the test solution was then injected into a 25 mL volumetric flask. 0.5 mL of pH 8.0 buffer and 0.5 mL of 2% ninhydrin solution were added. The solution was heated in a boiling water bath for 15 minutes. After cooling, the volume was adjusted to 25 mL. After 10 minutes, the absorbance was measured at 570 nm using a 5 mm cuvette.

[0072] The test results are shown in Table 1:

[0073] Table 1 Concentrations of tea polyphenols, free amino acids and caffeine in the finished cold-brewed teas of Examples 1 to 5 and Comparative Examples 1 to 3

[0074] sample Tea polyphenols concentration (mg / mL) Free amino acid concentration (%) Caffeine concentration (mg / mL) Experimental Example 1 1.01 1.12 1.31 Experimental Example 2 1.09 1.36 1.44 Experimental Example 3 1.17 1.54 1.51 Experimental Example 4 1.23 1.72 1.73 Experimental Example 5 1.35 2.03 1.89 Comparative Example 1 0.79 0.78 0.91 Comparative Example 2 0.87 0.98 1.02 Comparative Example 3 0.83 0.92 1.06

[0075] As can be seen from Table 1, as the pressure increases during the ultrahigh pressure treatment, the dissolution rate of the cold-brewed tea contents increases. Compared with the comparative example, the freeze-thaw treatment accelerates the dissolution of the cold-brewed tea contents. The dissolution rate of the cold-brewed tea contents without freeze-thaw treatment and ultrahigh pressure treatment is slower.

[0076] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing cold brew tea, characterized in that: The following steps are involved: Mixing tea leaves and water to obtain a tea leaves and water mixture; The mixture of tea leaves and water is subjected to freeze-thaw and ultra-high pressure treatment in sequence to obtain the cold brew tea; The preparation time is ≤6h.

2. The preparation method according to claim 1, wherein The tea leaves include green tea, white tea, yellow tea, oolong tea, black tea or dark tea.

3. The preparation method according to claim 1, wherein The mass ratio of the tea leaves to water is 1:(100-200); The temperature of the water is 4-10°C.

4. The preparation method according to claim 1, wherein The temperature of the mixed liquid of tea leaves and water is 0-10°C.

5. The preparation method according to claim 1, wherein The freeze-thaw process includes freezing and thawing performed sequentially; The freezing temperature is -10 to -20°C, and the freezing time is 60 to 120 minutes.

6. The preparation method according to claim 1, wherein The pressure of the ultra-high pressure treatment is 200-600 MPa.

7. The preparation method according to claim 1 or 6, wherein The ultrahigh pressure treatment time is 5 to 15 minutes.

8. The preparation method according to claim 7, wherein The ultrahigh pressure treatment was performed at a pressure of 600 MPa and for a time of 5 minutes.

9. The preparation method according to claim 1 or 8, wherein The cold brew tea is stored in a refrigerated manner.

10. The preparation method according to claim 9, characterized in that The temperature of the refrigeration treatment is 0-4°C.