Tea tree leaf foliar fertilizer with the functions of improving quality, increasing fragrance and enriching selenium

Abstract

The application belongs to the technical field of tea tree cultivation and specifically relates to a tea tree foliar fertilizer with the functions of improving quality, increasing fragrance and enriching selenium, which is prepared by mixing the following components: selenium-rich agent selenomethionine, fragrance enhancer, synergist betaine, chelating stabilizer, nutrient agent, wetting and spreading agent and deionized water; wherein the fragrance enhancer is composed of L-theanine, L-glutamic acid and L-phenylalanine; the tea tree foliar fertilizer uses selenomethionine as an organic selenium source, cooperates with gamma-polyglutamic acid to chelate and stabilize and promotes leaf surface absorption, simultaneously uses betaine as a synergist and L-theanine, L-glutamic acid and L-phenylalanine as complex amino acids to enhance fragrance, thereby realizing tea leaf selenium enrichment, quality improvement and fragrance enhancement.

Description

Technical Field

[0001] This invention belongs to the field of tea tree cultivation technology, specifically relating to a tea tree foliar fertilizer that combines the functions of improving quality and aroma with selenium enrichment. Background Technology

[0002] Tea is an important economic crop, and its freshness and aroma directly determine its commercial value. Selenium is an essential trace element for the human body, and selenium-enriched tea combines nutritional and health benefits with high market economic value. Selenium-enriched tea production has become an important way to increase the added value of tea. Foliar application of selenium is an efficient way to supplement selenium for tea trees, and foliar fertilizers are the most commonly used selenium application carrier.

[0003] There are two main technical routes for existing selenium-enriched tea foliar fertilizers. The first is the inorganic selenium route, which involves directly adding inorganic selenium salts such as sodium selenite. For example, patent CN108299076A discloses a special selenium-enriched foliar nutrient solution for tea leaves to prevent disease and increase yield, along with its preparation method. Inorganic selenium is less expensive, but its bioavailability is low, and improper spraying concentrations can easily burn leaves. Studies have also reported that inorganic selenium can increase caffeine content in tea, thus intensifying bitterness. The second route is the organic selenium route, such as patent CN117105721A, which discloses a mixture of bio-nano organic selenium and polyglutamic acid, utilizing polyglutamic acid to chelate and stabilize organic selenium and promote foliar absorption. Organic selenium (selenomethionine) has high bioavailability and can reduce caffeine levels; however, existing organic selenium foliar fertilizers have a limited functional focus, primarily concentrating on selenium supplementation itself, and there is room for improvement in enhancing quality indicators such as free amino acids, theanine content, and aroma quality in fresh leaves.

[0004] Regarding tea quality improvement, existing technologies have disclosed various foliar application routes. One is the amino acid foliar fertilizer route. For example, patent CN117898139A discloses the exogenous spraying of theanine to improve the yield and quality of yellowed tea, and patent CN106316626A discloses a foliar fertilizer that improves the quality of summer and autumn tea by regulating the redox balance, which can increase the content of free amino acids and reduce the phenol-amino acid ratio. Although this type of solution can improve freshness, it does not significantly improve the effect of selenium enrichment and cannot meet the market demand for selenium-enriched tea. The second is the aroma-inducing route. For example, patent CN122229035A discloses a composite foliar preparation composed of exogenous amino acids, carotenoid precursors, and jasmonic acid esters, which enhances aroma by inducing tea trees to produce volatile substances. However, the role of jasmonic acid ester inducers such as methyl jasmonate in inducing the production of volatiles in tea trees has been extensively studied and publicized. They are highly volatile, easily degraded under light and heat conditions, have a short effective period when directly sprayed, and studies have reported that their induction amount-effect relationship is non-monotonic. Excessive spraying amount is not conducive to the accumulation of target volatiles, making it difficult to stabilize the product.

[0005] Betaine (glycine betaine) is a known osmotic regulator. Existing research indicates that it primarily plays a role in drought resistance and low-temperature protection in tea plants. For example, patent CN120247600A discloses a liquid fertilizer composed of betaine, brassinolide, and potassium dihydrogen phosphate to improve the stress resistance of tea plants and the quality of tea leaves. However, this formulation does not contain selenium or aroma precursors, and brassinolide is a hormone-like substance; its main function is stress resistance and quality improvement, not selenium enrichment.

[0006] In summary, existing tea foliar fertilizers have the following shortcomings: existing selenium-enriched foliar fertilizers focus on selenium supplementation but have limited effect on improving quality components, while existing quality-enhancing and aroma-enhancing foliar fertilizers have limited effect on selenium enrichment, and it is rare to find one that can simultaneously achieve selenium enrichment and quality / aroma enhancement; in addition, inorganic selenium has low utilization rate and increases caffeine, while organic selenium, although having high utilization rate, has limited aroma-enhancing function when used alone, and the stability of organic selenium in fertilizer solution and leaf absorption depend on chelation systems; secondly, existing aroma-inducing foliar fertilizers rely on hormone-based inducers and do not involve selenium enrichment. Summary of the Invention

[0007] The purpose of this invention is to provide a tea leaf fertilizer that combines the functions of improving quality and aroma and enriching selenium, so as to solve the problems existing in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A tea leaf fertilizer that combines quality enhancement, aroma enhancement, and selenium enrichment functions, comprising, by weight, the following components: 0.05-0.5% selenium enrichment agent selenomethionine, 2-6% aroma enhancer, 5-20% synergist betaine, 1-6% chelating stabilizer, 1-5% nutrient, 0.1-1% wetting and spreading agent, and deionized water to bring the total to 100%; wherein the aroma enhancer is composed of L-theanine, L-glutamic acid, and L-phenylalanine.

[0009] Furthermore, the mass ratio of L-theanine, L-glutamic acid and L-phenylalanine is 1.5:1.5:1.

[0010] Furthermore, the chelating stabilizer is γ-polyglutamic acid.

[0011] Furthermore, the nutrient is potassium dihydrogen phosphate.

[0012] Furthermore, the wetting and spreading agent is Tween-80.

[0013] This invention also provides a method for preparing the tea leaf fertilizer, comprising the following steps: S1. Add γ-polyglutamic acid to deionized water at 50±5℃ and stir at 300-500 rpm for 40-60 min to obtain a polyglutamic acid solution. S2. Add selenomethionine to the polyglutamic acid solution and stir at 350-450 rpm for 20-40 min to chelate γ-polyglutamic acid with selenomethionine. S3. Add L-theanine, L-glutamic acid, L-phenylalanine, betaine and potassium dihydrogen phosphate sequentially to the chelation solution. Stir at 350-450 rpm for 10-15 min after each addition to obtain a mixture. S4. Add Tween-80 to the mixture, stir at 350-450 rpm for 10-15 minutes, adjust the pH to 5.8-6.5, make up to volume with deionized water, filter, and the tea leaf fertilizer is obtained.

[0014] The present invention also provides a method for using the foliar fertilizer for tea leaves, specifically: diluting the foliar fertilizer 50-200 times with deionized water and spraying it evenly on both sides of the tea leaves, with the spraying period being from the spring tea sprouting period to the initial unfolding stage of one bud and one leaf.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The leaf fertilizer for tea leaves of the present invention uses selenomethionine as an organic selenium source, combined with γ-polyglutamic acid to chelate and stabilize and promote leaf absorption, and uses betaine as an synergist and L-theanine, L-glutamic acid and L-phenylalanine complex amino acids as flavor enhancers, thereby achieving selenium enrichment, quality improvement and aroma enhancement of tea leaves.

[0016] (2) After the tea leaves are sprayed with the foliar fertilizer of the present invention, the total selenium content of the dried white tea produced can reach 0.366 mg / kg, and the proportion of selenium-containing amino acids can reach 68.5%, indicating that the organic selenium form plays a decisive role in achieving the selenium enrichment standard. Detailed Implementation

[0017] The technical solution of this invention patent is described clearly and completely below. The raw materials mentioned in the embodiments are all commercially available products: selenomethionine (L-selenomethionine, purity 98%), anhydrous betaine (CAS: 107-43-7, purity 98%), L-theanine (purity 98%), L-glutamic acid (purity 99%), L-phenylalanine (purity 99%), γ-polyglutamic acid (molecular weight 700,000, purity 99%), potassium dihydrogen phosphate (purity 99%), and Tween-80 (food grade).

[0018] 1. Preparation of tea leaf fertilizer The foliar fertilizer formula is shown in Table 1.

[0019] Table 1. Foliar fertilizer formulations with different dosages of L-selenomethionine and anhydrous betaine (unit: kg)

[0020] Table 2 Comparative Foliar Fertilizer Formulas (Unit: kg)

[0021] Note: The dosage of sodium selenite is the same as that of L-selenomethionine (selenium); the dosage of urea is the same as that of the enhancer (nitrogen).

[0022] The preparation method is as follows: First, add γ-polyglutamic acid to 60 kg of deionized water, heat in a water bath to 50 ± 5 °C, and stir at 350 rpm until completely dissolved to obtain a polyglutamic acid solution; add selenomethionine to it, and stir at 400 rpm for 30 min to chelate γ-polyglutamic acid with selenomethionine to obtain a chelate solution; add L-theanine, L-glutamic acid, L-phenylalanine, anhydrous betaine and potassium dihydrogen phosphate to the chelate solution in sequence, stirring at 400 rpm for 20 min after each addition to obtain a mixed solution; continue to add Tween-80, and stir at 350 rpm for 15 min; add 10% potassium hydroxide solution to adjust the pH to 5.8-6.5, and make up to 100 kg with deionized water, and filter through a 200-mesh sieve to obtain tea leaf fertilizer.

[0023] 2. Test Methods The experiment was conducted in a tea garden in Baise City, Guangxi Zhuang Autonomous Region (Lingyun Baihao variety, 8 years old, slope tea garden, medium fertility). Conventional water and fertilizer management was used; no other foliar fertilizers were applied besides those listed in Tables 1-2 during the experiment. The plot area was 30m². 2 Guard rows are set between blocks, and each treatment is repeated 3 times, with randomized blocks.

[0024] Table 1-2 shows that all treatments were diluted 100 times and sprayed for the first time during the spring bud sprouting period and the second time when the leaves were just beginning to unfold (one bud and one leaf). The spraying was applied until both sides of the leaves were evenly moistened without dripping. A control group was also included, sprayed with an equal amount of water. Sampling was conducted 7 days after the last spraying: new shoots were harvested according to the one bud and two leaves standard. Five sampling points were taken from each plot, and 20 new shoots were collected from each point as one sample.

[0025] Fresh samples were processed into finished samples according to the white tea processing technology: Fresh leaves were thinly spread on a water sieve for withering (naturally withering indoors until the moisture content was about 20%, the leaves showed ripples and the grassy smell disappeared), and then withered again on a sieve until the moisture content was about 13%. They were first dried in a 100℃ dryer for 20 minutes and then cooled for 15 minutes. They were then dried again in an 80℃ dryer for 20 minutes until the moisture content was about 6.5%. They were then cooled to room temperature to make finished white tea samples. The samples were then ground and passed through a 40-mesh sieve and stored in an airtight container away from light.

[0026] The total selenium content of the finished tea was determined by fluorescence spectrophotometry according to GB 5009.93-2017; the content of selenoamino acids (selenite, selenate, selenocysteine, L-selenomethylselenocysteine, and selenomethionine) was determined according to GH / T1429-2023, and the ratio of the content of the three selenoamino acids to the total selenium was calculated as the selenoamino acid ratio; tea polyphenols were determined according to GB / T8313-2008; the total free amino acids were determined according to GB / T 8314-2013, and the phenol-amino acid ratio was calculated based on the proportion of tea polyphenols to the total free amino acids; caffeine was determined according to GB / T 8312-2013; and theanine was determined according to GB / T 23193-2017. Determination of aroma components in finished tea (refer to CN117898139A): Weigh 2g of ground dry tea powder into a 20mL headspace vial, add 5μL of ethyl caprylate (200ng / mL) as an internal standard, and seal immediately; place the headspace vial in a 65℃ water bath for 50min, during which time an SPME extraction needle (50 / 30μm DVB / CAR / PDMS) is inserted into the headspace vial to adsorb aroma volatiles; after extraction, insert the extraction needle into the injection port of a gas chromatography-mass spectrometry (GC-MS) instrument for analysis and detection. Calculate the content (μg / g) of each characteristic aroma component.

[0027] 3. Results The results are shown in Tables 3 and 4.

[0028] Table 3. Effects of different factors on selenium content and quality of tea.

[0029] Note: Comparative Example 5, Comparative Example 7 and the blank control were not sprayed with selenium source, and the total selenium in the dry tea was far below the lower limit of the selenium enrichment standard of GH / T 1135—2024. The proportion of selenium-substituted amino acids has no significance for selenium enrichment determination, so it is not calculated.

[0030] As shown in Table 3, regarding the selenium enrichment effect, as the dosage of selenomethionine increased from 0.05% to 0.50%, the total selenium content of the dried tea increased from 0.148 mg / kg to 0.612 mg / kg. Among them, Example 3 had a total selenium content of 0.366 mg / kg and a selenomethionine content of 68.5%, which was the optimal treatment. In Comparative Example 1, after removing γ-polyglutamic acid, the selenomethionine content decreased to 59.6%, indicating that γ-polyglutamic acid chelation has the effect of stabilizing and promoting the leaf absorption of selenomethionine, thereby ensuring the selenium enrichment effect. In Comparative Example 2, after replacing it with isoselenium inorganic selenium (sodium selenite), although the total selenium reached 0.330 mg / kg, the selenomethionine content was only 46.3%, indicating that the organic selenium form has a significant advantage over the inorganic selenium form.

[0031] Regarding the quality improvement effect, the free amino acid content and theanine content in Example 3 were the highest among all treatments, significantly higher than the blank control, while the phenol-amino acid ratio of 6.31 was the lowest among all treatments. However, the quality improvement indicators of high-dose Examples 4 and 5 were lower than those of Example 3, indicating that 0.20% of selenomethionine was the optimal dosage for quality improvement. In Comparative Example 3, after replacing the compound amino acids with isonitrogenous urea, the free amino acid content was only 3.50% and theanine was 11.8 mg / g, which was close to the blank control, indicating that the contribution of compound amino acids to quality improvement and aroma enhancement came from the amino acid form itself rather than simple nitrogen supplementation.

[0032] Table 4. Effects of different methods on the aroma enhancement of tea (unit: μg / g)

[0033] As shown in Tables 3 and 4, in terms of aroma enhancement, the aroma components phenethyl alcohol (54.8 μg / g), benzaldehyde (17.5 μg / g), phenylacetaldehyde (13.7 μg / g), and β-ionone (8.5 μg / g) of the carotenoid pathway aroma component in Example 3 were the highest among all treatments. The main aroma components of white tea, linalool (173.7 μg / g), geraniol (81.6 μg / g), and methyl salicylate (30.4 μg / g), were simultaneously increased. In Comparative Example 6, after removing the compound amino acid synergist, the phenethyl alcohol content decreased to 27.9 μg / g (close to the blank control's 28.4 μg / g). In Comparative Example 5, after removing selenomethionine, the β-ionone content decreased to 5.3 μg / g (close to the blank control's 5.1 μg / g), which may be due to the driving effect of selenomethionine on the aroma of the carotenoid pathway.

[0034] In addition, based on the increase in phenylethanol, Example 3 showed a 93.0% increase compared to the blank control, while Comparative Examples 4, 5, and 7 showed only 19.0%, 7.4%, and 1.8% increases, respectively; this indicates that selenomethionine and betaine have a synergistic effect in improving quality and flavor.

[0035] In summary, Example 3 is the optimal example, achieving the effects of selenium enrichment, quality improvement, and aroma enhancement simultaneously.

[0036] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A leaf fertilizer for tea trees that combines quality enhancement, aroma enrichment, and selenium enrichment, characterized in that, The tea leaf fertilizer is composed of the following components by weight: 0.05-0.5% selenium-enriching agent selenomethionine, 2-6% flavor enhancer, 5-20% betaine synergist, 1-6% chelating stabilizer, 1-5% nutrient, 0.1-1% wetting and spreading agent, and deionized water to make up to 100%; wherein the flavor enhancer is composed of L-theanine, L-glutamic acid and L-phenylalanine.

2. The tea leaf fertilizer according to claim 1, characterized in that, The mass ratio of L-theanine, L-glutamic acid and L-phenylalanine is 1.5:1.5:

1.

3. The tea leaf fertilizer according to claim 1, characterized in that, The chelating stabilizer is γ-polyglutamic acid.

4. The tea leaf fertilizer according to claim 1, characterized in that, The nutrient is potassium dihydrogen phosphate.

5. The tea leaf fertilizer according to claim 1, characterized in that, The wetting and spreading agent is Tween-80.

6. A method for preparing tea leaf fertilizer according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add γ-polyglutamic acid to deionized water at 50±5℃ and stir at 300-500 rpm for 40-60 min to obtain a polyglutamic acid solution. S2. Add selenomethionine to the polyglutamic acid solution and stir at 350-450 rpm for 20-40 min to chelate γ-polyglutamic acid with selenomethionine. S3. Add L-theanine, L-glutamic acid, L-phenylalanine, betaine and potassium dihydrogen phosphate sequentially to the chelation solution. Stir at 350-450 rpm for 10-15 min after each addition to obtain a mixture. S4. Add Tween-80 to the mixture, stir at 350-450 rpm for 10-15 minutes, adjust the pH to 5.8-6.5, make up to volume with deionized water, filter, and the tea leaf fertilizer is obtained.

7. A method of using the tea leaf fertilizer according to any one of claims 1-5, characterized in that, Specifically, the foliar fertilizer is diluted 50-200 times with deionized water and then sprayed evenly on both sides of the tea leaves. The spraying period is from the spring tea sprouting period to the initial unfolding stage of one bud and one leaf.

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