Processing method for increasing content of methylated catechin in white tea

Abstract

The invention discloses a processing method for increasing the content of methylated catechin in white tea. The processing method sequentially comprises the following steps: 1) picking fresh tea leaves; (2) properly withering the fresh leaves; according to the processing method, the content of methylated catechin in the white tea is effectively increased, so that the content of methylated catechin in the white tea is remarkably increased by 1.5-5 times, and the processing method has the advantages of being easy and convenient to operate, low in cost and the like and has wide application prospects in the field of white tea processing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tea processing, and particularly relates to a processing method for increasing the content of methylated catechins in white tea. BACKGROUND

[0002] White tea is one of the six traditional tea types in China, belongs to a slightly fermented tea, was created in Fujian, China, and is mainly produced in Fuding, Songxi, Zhenghe and Jianyang. The tea tree varieties used for white tea processing mainly include Fuding Dabaicha, Fu'an Dabaicha and Fuding Dahuo tea. White tea has various pharmacological effects, is cold in nature and is commonly used as a folk medicine for reducing fire. Modern scientific research shows that white tea has the effects of reducing fire and inflammation, resisting oxidation, resisting radiation, resisting mutation, regulating blood lipids, regulating immune function and preventing cardiovascular and cerebrovascular diseases.

[0003] Methylated catechins are a series of derivatives formed by methylation modification of catechins, and have significantly higher stability and bioavailability than conventional catechins. Literature reports that methylated catechins have significant physiological effects such as anti-allergy, blood pressure reduction and intestinal flora regulation. The main methylated catechins found in tea leaves are (-)-epigallocatechin gallate 3-O-(3-O-methyl) gallate (EGCG3"Me), (-)-epigallocatechin gallate 3-O-(4-O-methyl) gallate (EGCG4"Me), (-)-epicatechin gallate 3-O-(3-O-methyl) gallate (ECG3"Me) and (-)-epicatechin gallate 3-O-(4-O-methyl) gallate (ECG4"Me), among which EGCG3"Me and ECG3"Me have the highest content. The content of methylated catechins in white tea produced by conventional processing technology is relatively low, about 0% to 0.8%.

[0004] Therefore, the present application aims to develop a tea processing method that can significantly increase the content of methylated catechins in white tea, thereby further improving the health effects of white tea. SUMMARY

[0005] In view of the problems in the prior art, the present application aims to provide a processing method for increasing the content of methylated catechins in white tea, which has the advantages of simple operation, low cost and significant effect, and is realized by the following technical scheme: The processing method for increasing the content of methylated catechins in white tea comprises the following steps in sequence: 1) picking tea fresh leaves; 2) moderately withering fresh leaves; 3) freeze-drying; 4) storage treatment; and 5) aroma extraction treatment.

[0006] Further, the tea fresh leaves in step 1) are summer and autumn tea tree fresh leaves, and the variety is Fu'an Dabaicha, and the picking standard is one bud and two leaves or one bud and three leaves.

[0007] Further, the fresh leaf moderate wilting temperature in step 2) is room temperature, and the wilting is to 20-35% of the tea fresh leaf moisture content.

[0008] Further, the freeze-drying in step 3) refers to the low-temperature vacuum freeze-drying of the wilted tea fresh leaf, the cold trap temperature is set to-30 to-60℃, the vacuum degree is 0-300mTorr, the freeze-drying is to 4.0-7.5% of the tea leaf moisture content, and the freeze-dried white tea is obtained.

[0009] Further, the storage treatment in step 4) is to seal and store the above freeze-dried white tea at room temperature in the dark, and the storage time is 1-4 years.

[0010] Further, the aroma extraction treatment in step 5) is to extract the aroma of the stored white tea by using a tea aroma extraction machine, the aroma extraction temperature is 80-110℃, and the aroma extraction time is 5-30min.

[0011] The processing method has the following beneficial effects: 1) The processing method effectively improves the content of methylated catechin components in white tea, has innovation and great market potential; 2) The tea processing method improves the content of methylated catechin in white tea by selecting suitable fresh leaf raw materials (Fuan large white tea variety, summer and autumn tea fresh leaves), moderate wilting (wilting to 20-35% of the tea fresh leaf moisture content), moderate storage (1-4 years), and reduces the loss of methylated catechin by selecting low-temperature vacuum freeze-drying method, thereby significantly improving the content of methylated catechin in white tea, and the improvement multiple can reach 1.5-5 times; 3) The processing method has the advantages of simple operation and low cost, and has broad application prospect in the field of white tea processing. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is the chemical structural formula of two representative methylated catechins (EGCG3"Me and ECG3"Me); Figure 2 is the appearance and tea soup appearance diagram of white peony white tea prepared by the processing method of example 1 of the present application; Figure 3 is the appearance and tea soup appearance diagram of Shoumei white tea prepared by the processing method of example 2 of the present application. DETAILED DESCRIPTION

[0013] The present application will be further described in combination with specific examples, so as to better understand the technical solutions.

[0014] Example 1

[0015] 1) Pick 2kg of autumn Fuan large white tea variety tea tree fresh leaves, and the picking standard is one bud and two leaves; 2) The fresh leaves are withered at room temperature until the moisture content of the tea leaves reaches 25%; 3) The above-mentioned fresh tea leaves were subjected to low-temperature vacuum freeze-drying. The cold trap temperature was set to -50℃ and the vacuum degree was 40mTorr. The freeze-drying was carried out until the moisture content of the tea leaves was 5.5%, thus obtaining freeze-dried White Peony White Tea. 4) The above-mentioned freeze-dried white peony tea shall be stored in a sealed, light-proof container at room temperature for 3 years; 5) The stored White Peony white tea is subjected to aroma enhancement treatment at a temperature of 85℃ for 30 minutes.

[0016] The appearance of the white peony white tea and the appearance of the tea liquor prepared in this embodiment are as follows: Figure 2 As shown.

[0017] Two representative methylated catechins (EGCG3"Me and ECG3"Me) in tea were quantitatively analyzed using liquid chromatography-high resolution mass spectrometry. Their chemical structural formulas are shown below. Figure 1 As shown in the figure, the contents of EGCG3"Me and ECG3"Me in the white peony white tea prepared by this invention are 8.9 mg / g and 4.6 mg / g, respectively, which are 2.1 times and 2.4 times that of methylated catechins in freeze-dried fresh tea leaves, and 1.7 times and 2.1 times that of methylated catechins in white tea prepared by conventional processes (referring to the national standard GB / T 32743-2016 Technical Specification for White Tea Processing) (Table 1).

[0018] The specific method for detection using liquid chromatography-high resolution mass spectrometry (HPLC-QExactive-MS) is as follows: UPLC-QExactive-MS was used for detection. UPLC conditions: T3 column (100 mm × 2.1 mm, 1.7 μm); binary mobile phase elution, flow rate 0.4 mL / min, injection volume 3 μL, column temperature 40 ℃. Mobile phase A was 0.1% formic acid solution (v / v); mobile phase B was 0.1% formic acid-acetonitrile solution. Mobile phase gradient elution program: 0–0.5 min, 98% A, 2% B; 0.5–10 min, 98%–85% A, 2%–15% B; 10–18 min, 85%–60% A, 15%–40% B; 18–20 min, 60%–10% A, 40%–90% B; 20–20.9 min, 10% A, 90% B; 20.9–21 min, 10%–98% A, 90%–2% B; 21–25 min, 98% A, 2% B. MS conditions: Electrospray ionization source; detection mode: positive ion mode scan; capillary voltage 3.5 kV, capillary temperature 300 ℃; auxiliary gas temperature 350 ℃, flow rate 10 L / min; mass scan range. m / z100–1000. The chromatographic retention time of EGCG3”Me was 10.964 min. m / z The value was 473.1078; the chromatographic retention time of ECG3”Me was 12.506 min. m / z The value is 457.1129.

[0019] Table 1: Effect of this invention on increasing the content of methylated catechins in white peony tea. Compound White tea of the present invention Fresh tea leaf White tea of conventional process Control process (withering to 18% moisture content of fresh leaf in step 2, and the rest is the same as the present invention) Control process (drying method is drying in step 3, and the rest is the same as the present invention) Control process (the tea sample is not stored in step 4, and the rest is the same as the present invention) Ratio (white tea of the present invention / fresh tea leaf) Ratio (white tea of the present invention / white tea of conventional process) EGCG 3"Me content (mg / g) 8.9 4.2 5.3 6.7 6.0 8.1 2.1 1.7 ECG 3"Me content (mg / g) 4.6 1.9 2.2 3.6 2.9 3.9 2.4 2.1 Total amount of EGCG 3"Me+ECG 3"Me (mg / g) 13.5 6.1 7.5 10.3 8.9 12.0 2.2 1.8 Note: *Drying conditions are 110℃ for 30 minutes, followed by cooling and then drying at 90℃ for another 30 minutes.

[0020] Example 2

[0021] 1) Harvest 2kg of fresh leaves from the Fu'an Dabai variety tea trees in summer, with the harvesting standard being one bud and three leaves; 2) The fresh leaves are withered at room temperature until the moisture content of the tea leaves reaches 22%; 3) The above-mentioned fresh tea leaves were subjected to low-temperature vacuum freeze-drying. The cold trap temperature was set to -50℃ and the vacuum degree was 40mTorr. The freeze-drying was carried out until the moisture content of the tea leaves was 5.3%, thus obtaining freeze-dried Shoumei white tea. 4) The above-mentioned freeze-dried Shoumei white tea shall be stored in a sealed, light-proof container at room temperature for 2 years; 5) The stored Shoumei white tea is subjected to aroma enhancement treatment at a temperature of 90℃ for 20 minutes.

[0022] The appearance of the Shoumei white tea and the appearance of the tea soup prepared in this embodiment are as follows: Figure 3 As shown.

[0023] Two representative methylated catechins (EGCG3”Me and ECG3”Me) in tea were quantitatively analyzed using liquid chromatography-high resolution mass spectrometry. The contents of EGCG3”Me and ECG3”Me in Shoumei white tea prepared by this invention were 7.6 mg / g and 3.6 mg / g, respectively, which are 2.4 times and 2.6 times that of methylated catechins in freeze-dried fresh tea leaves, and 2.5 times and 2.8 times that of methylated catechins in white tea prepared by conventional processes (referencing national standard GB / T32743-2016 Technical Specification for White Tea Processing) (Table 2).

[0024] Table 2: Effect of this invention on increasing the content of methylated catechins in Shoumei white tea. Compound White tea of the present invention Fresh tea leaf White tea of conventional process Ratio (white tea of the present invention / fresh tea leaf) Ratio (white tea of the present invention / white tea of conventional process) EGCG 3"Me content (mg / g) 7.6 3.2 3.1 2.4 2.5 ECG 3"Me content (mg / g) 3.6 1.4 1.3 2.6 2.8 Total amount of EGCG 3"Me+ECG 3"Me (mg / g) 11.2 4.6 4.4 2.4 2.5 .

Claims

1. A processing method for increasing the content of methylated catechins in white tea, characterized in that, The processing method includes the following steps in sequence: 1) picking fresh tea leaves; 2) withering the fresh leaves to a suitable level; 3) freeze-drying; 4) storage treatment; 5) aroma enhancement treatment. The suitable withering temperature of the fresh leaves is room temperature, and the withering is carried out until the moisture content of the fresh tea leaves is 20-35%.

2. The processing method for increasing the content of methylated catechins in white tea as described in claim 1, characterized in that, Step 1) The fresh tea leaves are those from tea trees in summer and autumn. The variety is Fu'an Da Bai Cha, and the picking standard is one bud and two leaves or one bud and three leaves.

3. The processing method for increasing the content of methylated catechins in white tea as described in claim 1, characterized in that, In step 3), freeze drying refers to the low-temperature vacuum freeze drying of withered tea leaves. The cold trap temperature is set to -30 to -60℃, the vacuum degree is 0-300mTorr, and the tea leaves are freeze dried until the moisture content is 4.0-7.5%, thus obtaining freeze-dried white tea.

4. The processing method for increasing the content of methylated catechins in white tea as described in claim 1, characterized in that, Step 4) involves storing the freeze-dried white tea in a sealed, light-proof container at room temperature for 1-4 years.

5. The processing method for increasing the content of methylated catechins in white tea as described in claim 1, characterized in that, In step 5), the aroma enhancement process involves using a tea aroma enhancement machine to enhance the aroma of the stored white tea. The aroma enhancement temperature is 80-110℃, and the aroma enhancement time is 5-30 minutes.

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