阅读说明：本技术 一种天然茶氨酸粗品的纯化方法 (Method for purifying crude product of natural theanine ) 是由 王奇超 程勇 邵云东 于 2020-06-01 设计创作，主要内容包括：本发明属于茶叶深加工技术领域,具体公开了一种天然茶氨酸粗品的纯化方法,将茶氨酸粗品干粉投入5～6.5倍干粉量的85～95%甲醇水溶液中加热至65～75℃后冷却结晶,抽滤后滤饼用2.5～3.5倍湿固体量的纯甲醇或者无水乙醇在20～25℃下打浆,可将天然茶氨酸含量为10%～30%的粗品精制到含量95%以上的精制品,工艺简单,成本低。本发明相对于现有的通过无水乙醇冷却结晶纯化茶氨酸的技术,得率有所提高,而且还具有除杂效果好、甲醇残留量低、安全性好的优点。(The invention belongs to the technical field of tea deep processing, and particularly discloses a method for purifying a crude product of natural theanine, which comprises the steps of putting dry powder of the crude product of theanine into 85-95% methanol aqueous solution with 5-6.5 times of dry powder, heating to 65-75 ℃, cooling and crystallizing, pulping filter cakes after suction filtration by using pure methanol or absolute ethyl alcohol with 2.5-3.5 times of wet solid at 20-25 ℃, refining the crude product with the natural theanine content of 10-30% to a refined product with the content of more than 95%, and has the advantages of simple process and low cost. Compared with the existing technology for purifying theanine by cooling, crystallizing and purifying absolute ethyl alcohol, the method has the advantages of higher yield, good impurity removal effect, low residual quantity of methanol and good safety.)

1. A method for purifying crude natural theanine is characterized in that: the method comprises the following steps:

s1, putting the theanine crude product dry powder into 85-95% methanol water solution, wherein the mass volume ratio of theanine to 85-95% methanol water solution is 1: (5-6.5), stirring and heating to 65-75 ℃, keeping the temperature for 0.9-1.5 h, and continuously stirring;

s2, after heat preservation is finished, carrying out suction filtration while the solution is hot, discarding filter residues, standing and cooling mother liquor to 20-25 ℃, and standing for 5-10 hours;

s3, carrying out suction filtration on the mother liquor, adding pure methanol or absolute ethyl alcohol into a filter cake, and pulping, wherein the mass-volume ratio of the filter cake to the alcohol liquor is 1: (2.5-3.5), stirring for 2-3 h at 20-25 ℃;

s4, after pulping, carrying out suction filtration, and drying a filter cake for 3-5 hours by hot air at 70-90 ℃ to obtain theanine dry powder.

2. The method for purifying crude natural theanine according to claim 1, wherein: step S1 uses a 90% methanol aqueous solution.

3. The method for purifying crude natural theanine as set forth in claim 2, wherein: step S1, the mass-to-volume ratio of theanine to 90% methanol aqueous solution is 1: 6, the mass-to-volume ratio of the filter cake and the pure methanol or the absolute ethanol in the step S3 is 1: 3.

4. the method for purifying crude natural theanine according to claim 1, wherein: step S1 keeps the process of stirring, heating and keeping warm at reflux.

5. The method for purifying crude natural theanine according to claim 1, wherein: the rotating speed of the stirring in the steps S1 and S3 is 90-120 r/min.

6. The method for purifying crude natural theanine according to claim 1, wherein: and S2, preheating the funnel and the filter paper to 50-60 ℃ before suction filtration while the funnel and the filter paper are hot.

7. The method for purifying crude natural theanine according to claim 1, wherein: and S2, standing and cooling the mother liquor, and simultaneously starting ultrasonic with the ultrasonic frequency of 20-30 KHz.

8. The method for purifying crude natural theanine as claimed in claim 7, wherein: and step S3, adding absolute ethyl alcohol into the filter cake and pulping.

9. The method for purifying crude natural theanine according to claim 1, wherein: and (4) storing the filtrate obtained by suction filtration in the step S3, heating and concentrating the filtrate in the next purification, mixing the filtrate with the mother liquor obtained in the step S2, and cooling and crystallizing the mixture together.

10. The method for purifying crude natural theanine according to claim 1, wherein: and S4, drying for 1-2 h by hot air, crushing the filter cake, spreading the filter cake, and then continuously drying by hot air.

Technical Field

The invention belongs to the technical field of tea deep processing, and particularly relates to a method for purifying a crude product of natural theanine.

Background

Theanine is a special non-protein amino acid in tea and is one of flavor development substances of the tea, and accounts for 50 to 60 percent of the total amount of the amino acid in the tea, and the theanine belongs to amide compounds and is chemically named as: n-ethyl-gamma-glutamine. Modern medical and pharmacological studies show that theanine has the effects of antagonizing nervous system excitation caused by caffeine, relieving emotional stress, lowering blood pressure, protecting nerve cells, enhancing the curative effect of anticancer drugs, inhibiting cancer cell infiltration, losing weight and the like. The physiological activity of theanine attracts the attention at home and abroad, and the theanine is widely applied to the fields of food additives, health care products, medicines and the like at present.

At present, natural theanine in the market is obtained by mainly adsorbing tea leaching liquor by using ion exchange resin, eluting by using ammonia water and removing ammonia, wherein the content of the theanine is about 10-30%, the impurities are more, the taste is seriously influenced, and the safety is difficult to ensure, so that the theanine needs to be purified. The existing theanine purification is that the crude theanine extract is concentrated and then added with absolute ethyl alcohol for crystallization, although the content of theanine can be quickly improved, the impurity removal after concentration is more difficult, the crystallization purification effect can be reduced, the crystallization loss is more than half, and the yield is low. The Chinese patent application with publication number CN101020649A discloses a method for separating and purifying natural theanine, wherein in the purification process, in addition to vacuum concentration and absolute ethyl alcohol crystallization, a step of column chromatography is added between two steps to remove impurities, so that the purification effect is improved, the purity of the obtained natural theanine is more than 95%, but the process is complex, the cost is high, and the theanine loss is large.

Disclosure of Invention

In order to solve the problems, the invention provides a method for purifying a crude product of natural theanine, which can purify the crude product of the theanine from 10-30% to more than 95%, has less entrained impurities, improves the yield, has low residual quantity of methanol (less than 50 ppm), and has simple process and low cost.

In order to achieve the purpose, the invention adopts the following specific technical scheme:

a method for purifying crude natural theanine comprises the following steps:

s1, putting the theanine crude product dry powder into 85-95% methanol water solution, wherein the mass volume ratio of theanine to 85-95% methanol water solution is 1: (5-6.5), stirring and heating to 65-75 ℃, keeping the temperature for 0.9-1.5 h, and continuously stirring;

s2, after heat preservation is finished, carrying out suction filtration while the solution is hot, discarding filter residues, standing and cooling mother liquor to 20-25 ℃, and standing for 5-10 hours;

s3, carrying out suction filtration on the mother liquor, adding pure methanol or absolute ethyl alcohol into a filter cake, and pulping, wherein the mass-volume ratio of the filter cake to the alcohol liquor is 1: (2.5-3.5), stirring for 2-3 h at 20-25 ℃;

s4, after pulping, carrying out suction filtration, and drying a filter cake for 3-5 hours by hot air at 70-90 ℃ to obtain theanine dry powder.

Preferably, step S1 uses a 90% methanol aqueous solution.

Preferably, the mass-to-volume ratio of theanine to 90% methanol aqueous solution in step S1 is 1: 6, the mass-to-volume ratio of the filter cake and the pure methanol or the absolute ethanol in the step S3 is 1: 3.

preferably, the stirring temperature rise and heat preservation process of step S1 is kept in reflux.

Preferably, the rotation speed of the stirring in the steps S1 and S3 is 90-120 r/min.

Preferably, in the step S2, the funnel and the filter paper are preheated to 50-60 ℃ before the hot suction filtration.

Preferably, the mother liquor in the step S2 is kept stand and cooled, and simultaneously, the ultrasonic frequency is started to be 20-30 KHz.

Preferably, the filter cake obtained in step S3 is added with absolute ethyl alcohol and beaten.

Preferably, the filtrate obtained by suction filtration in the step S3 is stored, heated and concentrated in the next purification, mixed with the mother liquor in the step S2, cooled and crystallized together.

Preferably, the filter cake is crushed after hot air drying for 1-2 h in the step S4, and the hot air drying is continued after the filter cake is spread flatly.

The invention has the following beneficial effects:

1. the method comprises the steps of cooling and crystallizing crude theanine dry powder by using 85-95% methanol aqueous solution which is 5-6.5 times of the dry powder, pulping filter cakes after suction filtration by using pure methanol or absolute ethanol which is 2.5-3.5 times of wet solid, refining crude products with natural theanine content of 10-30% to refined products with natural theanine content of more than 95%, and being simple in process and low in cost.

2. In order to reduce impurities of a finished product of theanine, the method starts ultrasound in the cooling and crystallization process of 85-95% methanol water solution to strengthen crystal growth, so that precipitated crystals are fine and uniform, meanwhile, the ultrasound and stirring are combined to avoid crystal agglomeration, the crystals are fine and are not easy to agglomerate, so that a large amount of impurities can be effectively prevented from being embedded, and the crystals are washed by pulping to reduce impurity adsorption, so that the method has a good impurity removal effect, the prepared theanine impurities are low in entrainment and high in safety.

3. The method inevitably uses methanol which has certain toxicity and the residue of the methanol in the finished product needs to be reduced, firstly, the method reduces the residual quantity of the methanol by optimizing the drying process, concretely, adopts a hot air drying mode to accelerate the volatilization of the methanol, takes out the filter cake in the middle section of the drying process, crushes and flatly spreads the filter cake and then continues to dry the filter cake, increases the contact surface area and ensures that the removal of the methanol is more sufficient; more optimally, absolute ethyl alcohol is used for pulping, although the purification effect of methanol is better than that of ethanol, the purification effect of cooling crystallization is optimized through ultrasound, so that the purity of the product cannot be influenced even when absolute ethyl alcohol is used for replacing methanol in the pulping process, the ultrasound is carried out in the cooling crystallization process, the embedding of impurities is reduced, the embedding of methanol is also reduced, and the difficulty of subsequent drying is reduced.

4. The invention improves the yield from the following three aspects: firstly, reflux is kept in the stirring, heating and heat preservation stages in the 85-95% aqueous solution cooling and crystallizing process, so that the loss of a solvent is reduced; secondly, filtering the mixture while the mixture is hot after heat preservation to prevent early crystallization from being removed, and preheating a funnel and filter paper before filtering to prevent loss and funnel blockage caused by cold crystallization; the filtrate that suction filtration produced after cooling crystallization of mother liquor recycles, it is specific, the filtrate that produces when purification is used for cooling crystallization jointly after mixing with the mother liquor of purification process next time to filtrate through heating concentration to just appearing the crystal and merge with the mother liquor again, this operation not only can make filtrate and mother liquor crystallize jointly, retrieve theanine in the filtrate, reduce the loss, improve the yield, the concentrated crystal of appearing of filtrate can be regarded as the seed crystal and accelerate cooling crystallization speed simultaneously, shorten crystallization time, raise the efficiency.

Detailed Description

The present invention will be further described with reference to the following specific examples.