阅读说明：本技术 高纯度高得率的天然咖啡因及其制备方法和应用 (High-purity high-yield natural caffeine and preparation method and application thereof ) 是由 王洪新 叶心 蔡昌华 王力 丁小玉 魏新林 邵佳佳 于 2020-04-30 设计创作，主要内容包括：本发明公开了高纯度高得率的天然咖啡因及其制备方法和应用,所述方法包括以下步骤：S1、原料液获取,S2、碱化原料液,S3、蒸干水分,S4、升华结晶。本发明所述方法选用廉价易得的水代替有机溶剂,可以降低成本,并且能避免在蒸发水分及升华过程中由于有机溶剂的存在而产生的安全问题；选用碳酸钠碱化原料液,碳酸钠与原料液中的单宁或单宁水解生成的没食子酸反应使咖啡因从其盐中游离出来,相比于传统的氧化钙、氢氧化钙和醋酸钠,可以较大地提高得率,增加纯度,同时减少了添加量；具有价廉、食品安全性好的优点。在较高温度下快速升华减少了升华所需时间和长时间加热的能耗,提高了升华效率；所得天然咖啡因质量高,适用于食品、医药等领域。(The invention discloses natural caffeine with high purity and high yield, a preparation method and application thereof, wherein the method comprises the following steps: s1, obtaining a raw material solution, S2, alkalifying the raw material solution, S3, evaporating water, and S4, sublimating and crystallizing. The method of the invention adopts water which is cheap and easy to obtain to replace organic solvent, thus reducing the cost and avoiding the safety problem caused by the existence of organic solvent in the processes of water evaporation and sublimation; the method selects sodium carbonate to alkalize the raw material liquid, and the sodium carbonate reacts with tannin in the raw material liquid or gallic acid generated by tannin hydrolysis to enable caffeine to be dissociated from salt of the raw material liquid, so that compared with the traditional calcium oxide, calcium hydroxide and sodium acetate, the method can greatly improve the yield, increase the purity and reduce the addition amount; has the advantages of low cost and good food safety. The rapid sublimation at a higher temperature reduces the time required for sublimation and the energy consumption of long-time heating, and improves the sublimation efficiency; the obtained natural caffeine has high quality, and is suitable for food and medicine fields.)

1. A method for preparing natural caffeine with high purity and high yield, the method comprising the steps of:

s1 obtaining raw material liquid

Commercially available tea leaves or coffee beans are used as raw materials, and a raw material solution is obtained according to the following method: pulverizing dried tea or coffee bean, sieving with 40-80 mesh sieve, reflux-extracting in hot water at 85-95 deg.C for 3 times (1-1.5 hr for each time), filtering after each extraction, continuously extracting the residue, collecting the three filtrates, and concentrating to obtain raw material solution;

s2 alkalizing raw material liquid

Adding sodium carbonate into the raw material liquid obtained in the step S1, and stirring until the sodium carbonate is completely dissolved, wherein the adding amount of the sodium carbonate is 6-15 times of the mass of the gallic acid in the raw material liquid;

s3, evaporating the water content of the raw material liquid after the reaction of S2 to dryness, and completely removing the water content to form powdery or blocky solid;

s4, heating and sublimating the solid obtained in the S3, and condensing the sublimed gas to obtain crystals, namely the caffeine.

2. The method of claim 1, wherein the S1 is extracted with 3 times of hot water, and the ratio m: v of the powder mass of tea leaves or coffee beans to the volume of water is 1:15, 1:10, and 1:10, respectively.

3. The method of claim 1, wherein the raw material liquid of S1 has a solid content of 5-10%.

4. The method of claim 1, wherein the raw material liquid obtained in step S1 is used for extracting tea polyphenols, theanine or tea protein, and then sodium carbonate is added for alkalization to extract caffeine.

5. The method of preparing natural caffeine according to claim 1, wherein the temperature of the S3 when the water is evaporated is 90 to 100 ℃.

6. The method as claimed in claim 1, wherein the sublimation temperature in S4 is 120-220 ℃ and the sublimation time is 15-60 min.

7. The method as claimed in claim 6, wherein the sublimation temperature in S4 is 190-220 ℃ and the sublimation time is 15-30 min.

8. High purity and high yield natural caffeine obtainable by the process according to any one of claims 1 to 7.

9. The high purity high yield natural caffeine according to claim 8, wherein the natural caffeine has a yield of 60.68% or more and a purity of 98.74% or more.

10. Use of the high purity high yield natural caffeine according to claim 8 as an additive in food and medicine.

Technical Field

The invention belongs to the technical field of functional foods, and relates to a deep processing method of tea or coffee beans, in particular to natural caffeine with high purity and high yield, and a preparation method and application thereof.

Background

Caffeine belongs to methylxanthine alkaloids, is the most common central nerve stimulant in the world, and is widely applied to industries such as food, medicine and the like due to the unique excitability effect on a nervous system. The caffeine in the current market is mainly synthetic caffeine, and is obtained by taking urea, sodium cyanide and dimethyl sulfate as initial raw materials, performing a series of refining after various types of chemical reactions are carried out to obtain caffeine crude products, the whole production process is complicated and tedious, a large amount of chemical reagents such as sulfuric acid, sodium hydroxide and dimethyl sulfate are used in the production process, the chemical reagents can be remained in the final finished product synthetic caffeine to cause harm to human bodies, and natural caffeine extracted from natural plants such as tea leaves and coffee beans has no similar harm. Among caffeine-containing plants, tea leaves (about 2 to 5%) and coffee beans (about 1 to 3%) contain a large amount of caffeine and are inexpensive and readily available, and thus are often used as raw materials for industrially producing natural caffeine.

The existing method for extracting natural caffeine from tea and coffee beans is mainly to crush dry tea or coffee beans into powder with a certain mesh number, extract the powder with hot water or an organic solvent, dissolve caffeine in the powder, and separate and purify the powder by a solvent extraction method, a sublimation method, a supercritical extraction method, an adsorption separation method and the like. The solvent extraction method usually adopts chloroform with relatively high toxicity as an extracting agent, so that the caffeine yield is high, but the solvent extraction method has great harm to the health of production personnel and is easy to bring secondary pollution; the supercritical extraction method has high extraction efficiency and less environmental pollution, but has high equipment cost and can not carry out large-scale industrial production; the adsorption separation method is green and safe, but the treatment capacity is small, and the solvent consumption is large; the sublimation method is simple to operate, the obtained caffeine has high purity, generally does not need further refining, but has low yield.

The sublimation method mainly utilizes the property that caffeine volatilizes crystal water at a temperature of more than 100 ℃ and starts to sublimate, and the caffeine can be quickly sublimated when the temperature reaches about 178 ℃, but the tea and coffee beans contain acidic substances such as tannin (tannic acid or tannic acid) and the like besides the caffeine, and gallic acid generated by hydrolysis of the tannin or tannin is easy to generate salt with the caffeine to hinder the sublimation of the caffeine. In the prior related invention patents, calcium oxide (quicklime) or calcium hydroxide (hydrated lime) or sodium acetate is generally added before sublimation operation to enable caffeine to be dissociated from salts thereof and then heated for sublimation, but the defects of low caffeine yield, large addition amount of substances such as calcium oxide and the like exist, and the cost for extracting caffeine is increased; in addition, in the related prior invention patents, the temperature set during sublimation is low and the time required for sublimation is long, which greatly reduces the processing efficiency.

Disclosure of Invention

The technical problem to be solved is as follows: in order to overcome the defects of the prior art and ensure the yield and purity of caffeine while ensuring that the caffeine sublimates after being dissociated from the salt of the caffeine, the invention provides high-purity high-yield natural caffeine and a preparation method and application thereof.

The technical scheme is as follows: a process for the preparation of high purity high yield natural caffeine, the process comprising the steps of:

s1 obtaining raw material liquid

Commercially available tea leaves or coffee beans are used as raw materials, and a raw material solution is obtained according to the following method: pulverizing dried tea or coffee bean, sieving with 40-80 mesh sieve, reflux-extracting in hot water at 85-95 deg.C for 3 times (1-1.5 hr for each time), filtering after each extraction, continuously extracting the residue, collecting the filtrates, and concentrating to obtain raw material solution; the tea leaves are crushed to the fineness of 40-80 meshes, so that the contact area of the tea leaves and water is increased, active substances such as caffeine in the tea leaves can be separated to the maximum extent, the caffeine can be well leached at the temperature of 85-95 ℃, meanwhile, tea polyphenol can be prevented from being damaged at high temperature, and more than 97% of caffeine in the tea leaves can be dissolved in the water by three times of hot water leaching.

S2 alkalizing raw material liquid

Adding sodium carbonate into the raw material liquid obtained in the step S1, and stirring until the sodium carbonate is completely dissolved, wherein the adding amount of the sodium carbonate is 6-15 times of the mass of the gallic acid in the raw material liquid;

s3, evaporating the water content of the raw material liquid after the reaction of S2 to dryness, and completely removing the water content to form powdery or blocky solid;

s4, heating and sublimating the solid obtained in the S3, and condensing the sublimed gas to obtain crystals, namely the caffeine.

Preferably, in S1, 3 hot water extractions are used, wherein the ratio m: v of the powder mass of tea leaves or coffee beans to the water volume is 1:15, 1:10 and 1:10, respectively. Or may be commercially available extract of tea leaves or coffee beans.

Preferably, the raw material liquid in S1 has a solid content of 5-10%.

Preferably, the raw material liquid obtained in S1 can be used for extracting active substances such as tea polyphenol, theanine or tea protein, and then added with sodium carbonate for alkalization to extract caffeine.

Preferably, the temperature at which the water is evaporated in S3 is 90-100 ℃.

Preferably, the sublimation temperature in S4 is 120-220 ℃, and the sublimation time is 15-60 minutes.

Preferably, the sublimation temperature in S4 is 190-220 ℃, and the sublimation time is 15-30 minutes.

The natural caffeine prepared by any one of the above methods has high purity and high yield.

Preferably, the yield of the natural caffeine is 60.68% or more, and the purity is 98.74% or more.

The natural caffeine with high purity and high yield is used as an additive in food and medicine.

The principle of caffeine acquisition described in the present invention is: the N atom connected with double bond in caffeine molecule has high activity, and can be easily combined with gallate ion in raw material liquid to form gallate of caffeine (formula 1) to inhibit sublimation of caffeine, after adding sodium carbonate into raw material liquid, sodium carbonate reacts with gallate of caffeine to make caffeine dissociate from its gallate (formula 2), after drying water, heating to sublimate caffeine into gas state, and gaseous caffeine can be desublimated to form caffeine crystal when encountering cold.

At present, the present application differs from the prior art in that: 1. the raw material liquid is alkalized by adopting sodium carbonate, the sodium carbonate is commonly named as baking soda, is a common food additive, is safer and cheaper than calcium oxide, calcium hydroxide and sodium acetate, and is easier to react with gallate ions than calcium ions, the calcium ions can react only when contacting two gallate ions simultaneously (formula 3), and the sodium ions can react only when contacting the gallate ions. In addition, sodium gallate generated by the reaction of sodium ions and gallate ions is soluble salt, calcium ions and gallate ions generate insoluble calcium salt, and calcium salt is easy to carbonize at high temperature to inhibit the sublimation of caffeine and reduce the purity of caffeine. When the raw material liquid is alkalized by sodium acetate, acetate ions generated by sodium acetate hydrolysis are stronger in acidity than carbonate ions and are easy to combine with caffeine to form salt, so that caffeine is prevented from being dissociated from the salt, meanwhile, the acetate ions can react with other substances in the raw material liquid to generate new substances, the purity of caffeine is influenced, and carbon dioxide and water are generated after the carbonate ions react. 2. Sublimation temperature and time's change, adopt the sublimation method to heat under the lower temperature in order to prevent that carbonization influences the purity of caffeine often when extracting caffeine among the prior art, the sublimation speed of caffeine is slow, in order to improve the yield of caffeine, can only prolong sublimation time, the massive thing that this application used behind sodium carbonate alkalization feed solution evaporation to dryness moisture to obtain is difficult for carbonizing under the high temperature, can sublime fast under the higher temperature and reduce the energy consumption that sublimes required time and long-time heating, improve sublimation efficiency.

Formula 1 salt-forming reaction formula of caffeine and gallic acid

Formula 2 reaction of sodium carbonate with caffeine gallate

Formula 3 reaction of calcium hydroxide with caffeine gallate

Has the advantages that: (1) the method of the invention adopts water which is cheap and easy to obtain to replace organic solvent, thus reducing the cost and avoiding the problems of carbonization or scorching caused by the existence of organic solvent in the processes of water evaporation and sublimation; (2) the sodium carbonate is selected to react with tannic acid in the raw material liquid or gallic acid generated by hydrolysis to enable caffeine to be dissociated from the salt, compared with the traditional calcium oxide, calcium hydroxide and sodium acetate, the yield can be greatly improved, the purity is increased, the addition amount is reduced, the market price of the sodium carbonate is lower than that of substances such as calcium oxide, and the like, so that the cost is saved, the economic benefit is increased, and the edible or medicinal safety of the product is improved; (3) the rapid sublimation at a higher temperature reduces the time required for sublimation and the energy consumption of long-time heating, and improves the sublimation efficiency; the method has the advantages of simple operation, low cost, suitability for industrial mass production, higher quality of the obtained caffeine, no chemical raw material residue, and suitability for industries of food, medicine, cosmetics and the like.

Detailed Description

The following examples further illustrate the present invention but are not to be construed as limiting the invention. Modifications and substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit and substance of the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.