JPS6242579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a tea extract having a desirable color tone.

More specifically, the present invention relates to a method for producing a tea extract in which discoloration-causing substances are reduced from the tea extract.

The tea extract processed in the present invention has significantly reduced substances that cause discoloration, and can maintain the state of the tea extract with good color tone for a long time, so it can be used to produce canned black tea, powdered black tea, etc. There are tremendous benefits to the food-related industry.

(Problems to be Solved by the Invention) Generally, aqueous extracts of green tea, roasted tea, semi-fermented tea, or fermented tea are extremely susceptible to deterioration over time. This alteration can include changes in color, aroma, and taste, but the most severe change occurs in color tone. It is thought that the free radical reaction that accompanies this color tone change causes a reduction in aroma and taste. It is widely known from experience that even in daily life, the aqueous extract of green tea or black tea stored in a thermos bottle turns dark brown or brown, resulting in a loss of flavor. Furthermore, when instant tea is made from this extract, the quality of the tea is significantly altered. That is, browning occurs due to air oxidation during the tea leaf extraction process, concentration process, and powder process. Especially in industrial manufacturing, long-term processing due to large-scale processing,
In addition, strong oxidation due to air contact during powderization is unavoidable. In addition, in the production of powdered instant tea, desirable components such as amino acids, theanine, sugars, and aromatic components must be extracted from tea leaves at a high yield in order to increase the yield.
This operation simultaneously extracts a large amount of substances that cause discoloration. Common sense suggests that if extraction is performed at the lowest possible temperature and in a short time, more active ingredients will be extracted.
Although fewer substances that cause discoloration will be extracted,
This method results in a low extraction yield. In addition, as an industrial raw material, it is possible to use crushed tea leaves that are a by-product of the normal tea manufacturing process, that is, an inexpensive raw material that is generally referred to as powdered tea, but powdered tea whose tea leaf structure has been destroyed may Since undesirable components are easily extracted, it is difficult to use it as an industrial raw material.

(Means for Solving the Problems) The present inventor has also conducted research on a method that can extract a large amount of desirable components such as amino acids, sugars, aromatic components, etc. from tea leaves, and extract less undesirable discoloration-causing substances. However, in industrial production methods, the objective cannot be achieved only by improving the extraction method.
It was also learned that there remained economic problems such as a decrease in extraction yield. In the end, it was discovered that the objective could only be achieved by selectively reducing the discoloration-causing substance from an extract containing large amounts of both. We also developed a removal method that selectively adsorbs or coagulates and removes the substances that cause discoloration, without adsorbing or coagulating or precipitating the flavor components such as nitrogen-containing compounds, sugars, and aromatic components in the aqueous extract of tea leaves. carried out a search.

The term "substances that cause discoloration" as used in the present invention refers to a group of substances that are contained in the aqueous tea leaf extract and cause sensually undesirable discoloration due to non-enzymatic oxidation during processing and storage.

The substances tested to remove discoloration-causing substances were inorganic adsorbents, inorganic flocculants, activated carbon,
There were dozens of types, including anion exchange resins, carbohydrate-based flocculants, and protein-based flocculants.

After testing many of these materials, it has been found that only polyamides, polyamine polymers, aluminum oxide, and methylcellulose effectively achieve the objectives of the present invention. Other adsorbents and flocculants either remove desirable components in the tea leaf extract, such as amino acids, or their selective removal of discoloration-causing substances is insufficient, or it is difficult to separate and remove the aggregates formed. , and other unfavorable points were observed. For example, activated carbon and ion exchange resins having quaternary ammonium groups are not preferred because they also adsorb amino acids. Furthermore, inorganic adsorbents such as zeolite, silica gel, acid clay, magnesium oxide, chloridyl, and diatomaceous earth have a weak ability to adsorb substances that cause discoloration, and are therefore not practical. Cellulose derivatives other than methylcellulose, starch derivatives,
Neither seaweed extracts nor plant gums were found to selectively coagulate and precipitate discoloration-causing substances. When a protein solution such as gelatin, milk casein, or soybean protein is added to a tea leaf extract, it becomes somewhat cloudy, but the cohesive force is weak and it is extremely difficult to separate and remove the aggregates, so no practical solutions have been found.

The present invention processes an aqueous extract of green tea, roasted tea, semi-fermented tea, or fermented tea with one or more selected from polyamide, polyamine polymer compound, aluminum oxide, and methyl cellulose, and This is a method for producing a tea extract characterized by reducing substances that cause discoloration.

The tea extract with reduced discoloration-causing substances through the treatment of the present invention retains the desired color tone when extracted, and at the same time has very little change in taste or aroma.

Raw material teas to which the present invention can be effectively applied include green tea, bancha, roasted tea (roasted tea), semi-fermented tea, and fermented tea. It is effective for high-grade green tea and fermented tea, which are prone to discoloration and where color tone is important. In particular, the method of the present invention is effective when the raw material is waste by-produced during the tea manufacturing process, that is, powdered tea, which is currently not widely used.

As the aqueous extract of tea leaves, soft water, hard water, water containing inorganic salts, 65% or less ethyl alcohol aqueous solution, etc. are used. Although the extraction method is not limited, a generally known multistage countercurrent extraction method is suitable. When the purpose is to produce instant tea, the higher the concentration of the final extract, the better; for example, if it is 10 degrees Brix or higher, subsequent steps will be easier and less heating will be required, resulting in a high-quality product. The lower the extraction temperature and the shorter the extraction time, the smaller the amount of discoloration-causing substances extracted, but naturally the extraction yield of effective tea leaf components becomes worse. Furthermore, when low-temperature extraction is performed using multistage countercurrent extraction, which is a highly efficient extraction method, the viscosity of the extract increases due to the low temperature, making workability difficult. The extraction temperature varies depending on the type of tea, and is relatively low for high-grade green tea and fermented tea, and higher for bancha, roasted tea, etc., but generally a temperature of about 40°C to 80°C is preferred. Even if the extract is extracted at a relatively high temperature for a long time and contains a large amount of discoloration-causing substances, a final product of good quality can be obtained by the treatment of the present invention.

The extract thus obtained can be treated with one or more selected from polyamide, polyamine polymer compound, aluminum oxide, and methylcellulose to reduce the substances that cause discoloration in the extract.

The polyamide herein refers to a synthetic water-insoluble polymer compound having an amide group as an active group, and is typified by what is commonly called nylon. When polyamide is added to an aqueous tea leaf extract, it selectively adsorbs substances that cause discoloration and does not adsorb any active ingredients. The treatment is carried out in neutral or slightly acidic conditions.

Moreover, the polyamine polymer compound refers to a water-insoluble polymer compound having a first or second amine group repeated every 2 to 6 carbon bonds. Water-soluble products cannot be used because the processing agent will remain on the product. This includes what is generally called a polyamine type chelate resin. For example, the commercially available Diamond Ion CR
-20 etc. Polyamine polymer compounds do not adsorb active ingredients such as amino acids in the aqueous tea leaf extract under neutral or slightly acidic conditions, but they selectively adsorb substances that cause discoloration.

Additionally, aluminum oxide is generally referred to as activated alumina, and _is made by activating _alumina hydrate through heat treatment _.
(n=1 to 3). There are various crystal forms of activated alumina, and commercially available products can be used. We learned that activated alumina does not adsorb monophenolic compounds, but has the interesting property of selectively adsorbing some polyphenol compounds. It is believed that selectively adsorbing ortho-dihydroxy compounds among polyphenol compounds is effective in removing substances that cause discoloration. Activated alumina also has the advantage of being easy to recycle. The treatment is carried out in neutral or slightly acidic conditions.

Methylcellulose is also used as a food additive. This substance becomes colloidal with water, so
The method of use is slightly different from the other substances listed above. When a concentrated solution of methylcellulose, for example, a 2-10% aqueous solution, is added to an aqueous tea leaf extract and stirred, a cloudy agglomerate is formed. If this aggregate is removed by filtration or centrifugation, the discoloration-causing substance can be removed. The treatment is carried out in neutral or slightly acidic conditions.

What the above substances have in common is that they have weakly basic active groups consisting of primary amines, secondary amines, or amide groups, or OH-type hydrogen bond active groups of 0.14~
Since it is a polymeric compound that repeats at intervals of 0.7 nm (nanometers), it is thought that compounds that do not belong to this category do not have the effect of selectively removing substances that cause discoloration in the aqueous tea leaf extract.

The amount of adsorbent or flocculant used is determined by the type and quality of the raw tea, the extraction method, the concentration of components in the aqueous extract, the type and adsorption activity of the adsorbent or flocculant, and so on. For example, substances that cause discoloration are usually found in higher quality teas and less in lower quality teas such as bancha and roasted tea, so the amount of adsorbent used should be determined depending on each type of tea. Furthermore, even among tea leaves of the same strain, the extraction of discoloration-causing substances is low if the leaf tissue is relatively intact, and increases when the raw material is powdered tea whose tissue has been strongly destroyed.

Furthermore, when the extraction temperature is high or the extract is concentrated, a large amount of adsorbent or flocculant is required.

In addition, adsorbents of the same type have different adsorption characteristics and adsorption capacities depending on the state of recovery and regeneration.

Therefore, the amount of adsorbent and flocculant used, processing time,
Processing temperature, etc. are determined through preliminary tests. In the preliminary test, a certain amount of adsorbent or flocculant was added to the tea leaf extract, the reaction was allowed to occur under certain conditions, and the reactants were removed.The liquid was then air oxidized under certain conditions to see the degree of discoloration after oxidation. It is done by hand. An example of a simple method is as follows. The treatment conditions can be determined by soaking a certain volume of the treated liquid onto a filter paper, storing it under certain conditions for oxidation, and then comparing the color tone of the filter paper piece with a standard color comparison table prepared in advance.

The pH during treatment with an adsorbent or flocculant is preferably between 4.0 and 7.5. If the pH is acidic, below 4.0, the adsorption capacity will decrease, and if the pH is above 7.5, the substances that cause discoloration will change, which is not good. Preferably, the pH is between 5.0 and 6.5. There are two main methods for using adsorbents: the batch method and the column method. Since the column method requires time for the liquid to pass through, the conventional batch method is used.
When using methylcellulose, methylcellulose may be added in advance to the aqueous liquid from which tea leaves are extracted, or it may be added to the extract afterwards. The former method has the advantage of simplifying the process. The adsorbent and flocculant are separated and removed by known methods such as filtration and centrifugation.

The treated tea extract was placed in a can and sterilized and then stored at room temperature for 6 months, and it had excellent color and flavor. This was true for any tea, including green tea and fermented tea.

If instant tea is produced using the tea extract treated in the present invention, instant tea with excellent color, aroma, and taste can be obtained. When producing instant tea,
The aqueous tea leaf extract subjected to the above treatment is concentrated by a known method, or is directly powdered. In the extraction step, it is preferable to extract at a concentration of 10 degrees Brix or higher, and then proceed to the powdering step without the subsequent concentration step, in order to prevent flavor substances from escaping. A known method can be used for powdering, but freeze-drying, spray-drying, reduced-pressure drying, etc. are preferable. If necessary, shape preservatives such as polysaccharides, acidity regulators, taste substances such as amino acids, and flavoring agents such as lemon essence and diasmine can be added at any step. When powdered instant tea made by the above method is dissolved in hot, hot, or cold water and drunk, it has a good color and excellent flavor, and when stored as a powder, there is no change in color or flavor. few.

Example 1 Extract 1 kg of Ceylon black tea with 85℃ hot water at 60°C for 4 minutes to remove the residue, add 1M citric acid/sodium citrate buffer to adjust the pH to 5.5, and extract activated alumina (Sumitomo Metal Industries, Ltd.) at about 40℃. ) Add 4g and mix loosely.
After stirring for 10 minutes and filtering, a beautiful bright red black tea extract was obtained. Add 9w/w sugar to this liquid
% and then packed into beverage cans and sterilized under pressure at 115°C for 15 minutes to produce canned tea beverages (processed products).

A beverage made in the same manner as above except for the activated alumina treatment was used as an untreated beverage. When both were stored at room temperature, the untreated product had already turned black immediately after production (immediately after sterilization), and after 3 weeks, obvious discoloration was observed and the flavor had deteriorated.
In contrast, the treated product remained bright red even after 6 months and had a drinkable flavor.

Example 2 Crushed green tea, so-called powdered tea (commercial product) 7
1 kg each is packed into seven cylinders maintained at 60°C using a jacket method, and each cylinder is heated to 60°C from the bottom of each cylinder.
of hot water is injected under pressure, and a multi-stage countercurrent extraction method is used to extract approximately
A green tea water extract of 16 degrees Brix was obtained. After adjusting the pH of this extract to 5.6, 65 g of activated alumina (manufactured by Merck) was added to the extract, stirred gently at room temperature for about 15 minutes, and then centrifuged to remove the precipitate. An excellent green tea beverage was obtained.

Example 3 Pack 7 kg of bancha into seven pressure-resistant cylinders, each weighing 1 kg.
Hot water at about 90°C was injected under pressure and a multi-stage countercurrent extraction method was used to obtain a bancha water extract with a temperature of about 11°C. After adjusting this extract to pH5.8, 55g per 1
Add nylon 66 powder (Asahi Kasei) to the extract and
After gently stirring at 40°C for 15 minutes, the adsorbent was removed by filtration to obtain a bancha liquid with excellent flavor.

Example 4 Roasted tea (roasted tea) was extracted under the same conditions as in Example 3 at 90°C to obtain an extract having a concentration of approximately 10°C.
50g of Diaion CR-20 per 1 extract
(synthetic resin in which polyamine is introduced into styrene and divinylbenzene copolymer), and at the same time the pH
After adjusting the temperature to 5.5, the mixture was gently stirred at room temperature for 15 minutes and filtered to remove resin particles, yielding hojicha with a good flavor.

Example 5 7 kg of semi-fermented tea (oolong tea) was extracted at 70° C. according to the method of Example 2 to obtain an extract of approximately 11 degrees Brix. After adjusting this extract to pH6.0,
13 g of methylcellulose was added to the extract as a 3% aqueous solution, stirred gently at room temperature for 10 minutes, and aggregates were removed by centrifugation to obtain oolong tea with good color.

Example 6 Seven bottles of 7 kg of black tea were heated at 60°C according to the method of Example 2.
Filled with methyl cellulose in a cylinder held by
Multi-stage countercurrent extraction was performed using hot water at 50°C containing 0.005% to obtain an extract with a thickness of approximately 10°C. Next, the extract was adjusted to pH 5.3 with 1M citric acid/sodium citrate buffer, and then centrifuged to remove suspended matter to obtain black tea liquid with excellent color.

Reference example 1 Dextrin per green tea drink obtained in Example 2
150 g was added, and the rest was freeze-dried in a conventional manner. The resulting product was an instant green tea powder that was easily soluble in cold water, had a desirable color tone, and had an excellent flavor. In addition, PH adjustment is 1M
was carried out in citric acid/sodium citrate buffer.

Reference Example 2 The bancha liquid obtained in Example 3 was concentrated under reduced pressure to about 40 degrees Brix, and dextrin was added to this liquid 1.
200g, glycine 30g, monosodium glutamate
10 g and 5 g of common salt were added, and the mixture was dried and powdered using a vacuum tray drying method. The resulting product dissolved in hot water was a bancha liquid with a beautiful golden color and good flavor.

Reference example 3 The hojicha obtained in Example 4 was concentrated under reduced pressure to 40 degrees Brix, and dextrin was added to 1 part of the concentrate.
200 g, 40 g of glycine, and 10 g of salt were added, and the rest was spray-dried in a conventional manner to obtain powdered hojicha.

Reference Example 4 The oolong tea obtained in Example 5 was concentrated under reduced pressure to about 37 degrees Brix, and 200 g of dextrin, 40 g of alanine, and 10 g of sodium glutamate were added to 1 part of the concentrate, and the rest was spray-dried using a conventional method to form a powder. Obtained. When this product is dissolved in hot water,
The liquid had a more beautiful golden color than the liquid obtained by extracting half-fermented tea with boiling water using the usual method.

Reference Example 5 The black tea liquid obtained in Example 6 was concentrated under reduced pressure to about 30 degrees Brix. Sugar was added to this concentrate 1 to make it 58 degrees, and flavoring was added to prepare a black tea syrup liquid.

Claims (1)

[Scope of Claims] 1. An aqueous extract of green tea, roasted tea, semi-fermented tea, or fermented tea is treated with one or more selected from polyamide, polyamine polymer compound, aluminum oxide, and methylcellulose to obtain an extract. A method for producing a tea extract characterized by reducing the substances that cause discoloration in the tea extract. 2. The method for producing a tea extract according to claim 1, wherein the green tea, roasted tea, semi-fermented tea, or fermented tea is powdered tea.