DE2304073C3 - Process for making black tea - Google Patents

Description

The invention relates to a process for the preparation of an instantly soluble powder of black Tea made from green or unfermented tea. Black tea is commonly made by Wilting, rolling fermentation and roasting fresh tea leaves. Catalyze in this process the leaf's natural tea enzymes the fermentation (oxidation) of the polyphenols in the fresh leaf to the polyphenols, which are characteristic of black tea. Black tea extracts can also be made from porridges or extracts of unfermented tea by oxidation in Presence of natural tea enzymes. In this process, the unfermented tea can be made from fresh Tea leaves are made, the enzymes of which catalyze the conversion to black tea, or it can be greener Tea, the enzymes of which have been inactivated by heating, in which case natural tea enzymes for use Catalyze the conversion to black tea. The term black tea is used used here to include both tea leaves and extracts prepared by any of the above processes describe. The term unfermented tea is used here to refer to both fresh tea (whichever can be frozen or dried) with live natural tea enzymes such as green tea, its Enzymes have been inactivated.

The desired properties of a black tea product are attractive taste and color, when prepared as a drink with or without milk, and high in soluble solids. If the black tea should be converted into an instantly soluble (instant) tea powder, it should have a minimum Contain »tea cream«, these are solids that can be extracted with hot water, but which are in cold water Are insoluble in water. The present invention relates to a pretreatment of the unfermented Teas which, after conversion, are black tea with these desirable properties supplies.

The conversion of green tea to black tea either in a slurry or in water Extracts are known, for example, from GB-PS 12 04 585 and GB-PS 12 04 576. None of these patents however, suggests pre-treating tea to make the product more soluble.

Over the years numerous suggestions have been made to avoid the insoluble, as "tea cream" to solubilize designated material. According to the method of GB-PS 12 49 932 should be a certain amount Solubilization can be achieved if the "tea cream" of black tea has the effect of Tannase enzyme is exposed. However, this process is only of limited use and in no way leads to good results.

Surprisingly, however, it has been found according to the invention that if the enzyme treatment before Conversion of green tea into black is made, the then resulting black tea extract has a much lower tendency to form "tea cream" when refrigerated. This surprising one The effect is through comparative tests (see in particular Example 1 and that there according to the method of GB-PS 12 49 932 produced comparative product E) detected.

The inventive method for the preparation of an instantly soluble powder of black tea by Production of an aqueous tea extract in a slurry from crushed green tea leaves in water, converting the tea solids in the extract into black tea while adding natural Tea enzymes either before or after the aqueous tea extract has been separated from the slurry and Drying of the converted tea extract for the production of a tea powder is characterized by that before the conversion of green tea, the aqueous tea extract with tannase at pH values and Temperatures at which this is active is brought into contact.

In a preferred embodiment of the invention, a flowable homogenate or pulp is made from fresh Tea leaves, preferably with a water to leaf ratio of 3: 1 to 10:!, Prepared.

Suitable modes of operation for the preparation of the pulp include, that is, cryogenic milling Grinding the tea leaves while maintaining the frozen state with subsequent frying in Water or homogenize the tea leaves with a desired amount of water in an apparatus, whereby the leaves are crushed and dispersed. The tea leaf pulp is preferably under anaerobic Conditions before and during the tannase

act held to avoid any premature fermentation to avoid. Maintaining anaerobic conditions can be accomplished by introducing them of the homogenate in a closed vessel and jetting with nitrogen gas in order to take away Remove oxygen.

The enzyme tannase is obtained as an elaboration product of the growth of certain molds, which belong to the genus Aspergillus or Penicillium. For example Aspergillus flavus, bred on a medium containing tannic acid as the sole carbon source, tannase provides substantial amounts Amounts. Two specific strains of these microorganisms, known to be producers of significant amounts of tannase, are Aspergillus oryzae ATCC No. 9362 and Aspergillus niger ATCC No. 16 888. A suitable one Tannase preparation obtained with a strain of Aspergillus oryzae is commercially available as a powder. The amount of tannase enzyme preparation that is added to the pulp is generally 1 to 16, preferably about 8 enzyme units per gram of dry weight of the tea, measured by the libuchi et al method, which will be described in the following. Tannase S has about 20,000 enzyme units per gram Powder when measured according to this method.

The temperature at which the tannase treatment is carried out is preferably 25 to 65 ⁰ C and the best results are obtained at a temperature of about 45 ° C. The treatment is preferably carried out for at least 15 minutes.

Following the completion of the tannase treatment before the conversion, the tea conversion process is effected by adjusting the temperature the tea leaves, pulp or homogenate to about 25 ° C and jetting with air. If the degree of Aeration adjusted to maintain about 25% oxygen saturation in the slurry becomes one Satisfactory conversion achieved in about 80 minutes. Hydrogen peroxide can homogenate the tea leaf be added in regulated amounts in order to shorten the conversion time. The hydrogen peroxide usually becomes uniform over a period of about 20 minutes starting about 15 minutes after Beginning of pouring, added. The end of the tea conversion process will be indicated when the degree of Oxygen saturation in the tea leaf pulp suddenly increases. The ventilation will be on for about up to 30 minutes after this Increase in oxygen saturation, preferably about 10 minutes if hydrogen peroxide used continues. The conversion process is then carried out by heating the pulp to about 85 ° C for about 5 minutes by killing the natural tea enzymes.

An alternative method of working uses an aqueous extract of green tea leaves as the starting material. Elei This way of working, the extract is given a tannase treatment before conversion, and that The tea conversion process is then effected by bringing together the tannase-treated F: extract with a tea enzyme preparation. The applied tannase preparation can be on a solid support such as glass or polymeric material to be immobilized in order to remove it from the system and the Allow reuse of the enzyme. Working methods to accomplish the establishment of the Enzymes on insoluble substrates are disclosed in US Pat. Nos. 35 19 538, 35 36 587 and 35 56 945 and also by US Pat S i I m e η et al in "Annual Review of Biochemistry",

ίο

1966, Volume 35, Pages 873 to 908, in the article "Colloquim on Insolubilized Enzymes", Biochemical Journal, 1968, Volume 107, Pages IP through 6P, and by H. Weetal in “Enzymes Immobilized on Inorganic Carriers by Covalent Attachement, Research / Development, 1971, Volume 22, Pages 18-22. in the In general, the methods of rendering enzymes insoluble require the enzyme to be attached to an enzyme insoluble support due to covalent bonding, absorption or occlusion. The insoluble Made enzymes are expediently provided in finely divided form, e.g. B. Glass beads, which in Columns can be packed for use in continuous processes. The tea enzyme preparation can also be immobilized. An example of a tea enzyme preparation is described by H. Co and G. W. Sanderson in Journal of Food Science, 1970, Volume 35, Pages 160-164.

Whether the unfermented tea used is a pulp of unfermented tea or an extract of green tea, the inventive method is preferably used in a pH within one unit of the natural pH of tea infusions, which is about pH 5.6 is. The pre-conversion tannase treatment is preferably carried out at a pH of about 5. the Tea conversion level is preferably within the pH range 4.8 to 6.0, most preferably around 5.6, executed. The pH which falls as a result of the tannase treatment is preferably set before the conversion step set, for example with potassium hydroxide.

The product of the conversion process, in which a green tea extract is used from the raw material, is a black tea extract. When a pulp or homogenate of green tea is used as the starting material, the product of the conversion process can be broken down into an extract and tea leaf residue by filtration, centrifugation, or any other technique. The leaf residue can be re-extracted with water, if desired, to increase the amount of tea solids recovered in the extract, and the material so extracted can be added to the first extract obtained. The black tea extract obtained by any of the above methods can be concentrated and dried by conventional procedures including freeze drying and spray drying to give a cold water soluble instant tea powder. The extract is preferably defogged by adding calcium chloride and centrifuged before concentration and drying. The amount of added calcium chloride is preferably about 3 wt .-% of tea solids, and appropriate centrifugation conditions are 6900 g at 10 ⁰ C.

It has been found that tannase treatment of black tea extracts produced by fermentation of green tea as a solution or porridge, which does not dissolve the tea cream, which is contained in the extracts is. The method according to the invention, however, prevents the formation of these solids in black tea extract, which cause the tea cream formation. While the exact mechanism by which the invention runs, has certainly not yet been recognized, it is assumed that tannase catalyzes a reaction, ν eiche leads to the formation of cold water soluble tea pigments., a during the tea conversion process. It it is believed that in the treatment before the

Conversion of the tannase is the hydrolysis of the ester bonds between galloyl groups and diverse ones Compounds which are known to be present in unconverted tea leaves are catalyzed. In the The reaction in question will presumably be a deesterification, which is carried out according to the following scheme can run:

OH
HO i OH

(Tannase + H ₂ O)

OH
HO i OH

V /

ROH +

C = O

wherein ROH means any of several different compounds found in green tea leaves are present, including EpicatecHn and Epigallocatechin. It was found that the effect of this Tannase catalyzed deesterification consists in keeping the natural amount of gallic acid and epicatechin in Increase unconverted green tea leaves. This appears to result in the formation of large amounts of epitheaflamic acid to favor during the tea conversion process. Epitheaflamic acid is as shown was, in unusually large amounts during the tea conversion process according to the invention in Tea leaves are formed, which have undergone a tannase treatment before conversion. Epitheaflamic acid has been shown to have a desirable light, reddish black, tea-like color and is very good Cold water solubility.

The method used to determine the tannase activity of enzyme preparations is one Modification of the method as described by Sakaaki I i b u c h i, Yasuji M i η ο d a and Koichi Y a m a d a in "Agricultural and Biological Chemistry", Volume 31, page 513 (1967), was described. This method determines the amount of tannic acid which, in the presence of a measured amount of the tannase enzyme, falls below a A range of conditions is hydrolyzed by measuring the decrease in the absorbency of the Substrate at a wavelength of 310 mm using a recording ultraviolet spectrophotometer. The solution used for this test is a 0.004 weight percent tannic acid solution in 0.21 M acetate buffer (pH 5.0).

The tannic acid used is an analytically pure tannic acid. 3.0 ml of this solution are placed in a 1 cm cuvette which is maintained at 30 ⁰ C in the chamber of a temperalurgeregeltcn pattern registered Cary Model 14 Ultraviolet Spectrophotometer. Eventually it will be 0.1 m! Enzyme solution is added and the change in absorbance at a wavelength of 310 mm is continuously monitored. The concentration of the enzyme solution is adjusted until a change in absorbance of about 0.10 absorbance units / minute is observed. One unit of tannase enzyme activity, measured by this method, is defined as that activity which will give a change of 1 absorbance unit per minute at 310 mm (30 "C, 1 cm cell) using a 0.004% tannic acid solution in 0, 02 M acetate buffer (pH 5.0) with an initial absorbance of about 0.7.

Three tannic acid deliveries were made at this C = O

OH

Examination tested namely (a) Tannic Acid N.F. - Catalog No. 1750 and (b) Tannic Acid Analysis Reagent - Catalog No. 1764 from Mallinckrodt Chemical Works, St. Louis. Missouri, and (c) Tannic Acid N.F. Catalog No. 1198, Allied Chemical Corporation. Morristown, New Jersey. All three samples of tannic acid gave the same results when in the

2> Test of Tannase S applied according to the method described, namely 20,000 units per Gram.

The following examples explain the process according to the invention. The percentages are by weight

JIi ge, unless otherwise stated.

Values describing the color and haze of instant tea products are given as results, obtained by performing standard tests using a Hunter D-25 colorimeter.

) -> The haze values were determined by reflectance, and the numbers given indicate the amount of light reflected: the lower the haze number. the clearer is the tea solution. The tristimulus color match is based on the measurement of transmitted

4 (i light. The L value is the lightness factor: a value of! 00 indicates no color, while a value of 0 indicates complete darkness. The a value is a measure of the red-blue range of colors, and the b value is a measure of the green-yellow line

• r, beverage strength being analyzed, that is 0.35% tea solids in a 5 cm inch, the preferred L value is in the range of 20 to 35, the preferred a value is at least 8 units greater than the /. Value, and the preferred b value is between about 15 and 25.

At game 1

Fresh green tea leaves obtained from a tea farm near Charleston, South Carolina, were frozen at -40 ° C and cryogenically ground to a uniform particle size of about 0.5 to 1.0 mm ² in a hammer mill. These cryogenically ground tea leaves were used for all of the processing described below.

Product A.

A 171 g swatch of the ground fresh tea leaves with a total solids content of about 25%. was converted into a slurry with 600 ml of water in a reaction vessel and nitrogen gas was passed through the system while the temperature was maintained at 25 ° C. by circulating temperature-controlled water through the jacket.
The tannase treatment before conversion

was carried out by adding 16 mg of Tannase S enzyme containing 320 units of activity the tea leaf homogenate and keeping the homogenate under anaerobic conditions by means of continuous Spraying with nitrogen for 2 hours at> 25 ° C. At the end of the tannase treatment period, that was it pH of the green tea leaf homogenate dropped to 4.7, and therefore it was necessary to adjust the pH of the Adjust the homogenate again to the initial pH of 5.6 with 2 N KOH. κι

The enzymatic conversion of the green tea was then carried out in the following manner. The fermentation was started by switching the spray gas from nitrogen to air. The amount of aeration was adjusted to keep the amount of dissolved oxygen in the homogenate at 25% saturation. The temperature was maintained at 25 ^° C throughout the following conversion. The constant gas flow rate kept the amount of dissolved oxygen in the homogenate steady at 25%. After 15 minutes of aeration, a 2 M hydrogen peroxide solution was added dropwise over a period of 20 minutes so that the total volume of added hydrogen peroxide solution was 16.0 ml. The conversion Wuide for 2 "> about another 10 minutes continued until the dissolved oxygen level began to rise rapidly from 25% to about 40% saturation in the homogenate. Aeration was continued for another 10 minutes, after the conversion by changeover μ development of the spray gas was interrupted from air to nitrogen, and the pH was again adjusted back to pH 5.6 with 2N KOH, which is the natural pH of most converted tea infusions

The converted homogenate was heated to 85 ° C. and held at this temperature for 5 minutes. The tea extract was then separated from the spent tea leaves by filtering the heated homogenate through Miracloth. Calcium chloride (1% on a TeefestStoffbasis m) was added to the filtered tea extract, and the solution was maintained at 25 ° C for 45 minutes. Finally the extract was cooled to 4 ° C. and polished by centrifugation at 6900 g for 10 minutes. The polished 4Ί extract was then freeze-dried operated at a shelf temperature of 95 ° C, a plate temperature of in a Stokes-P-9 freeze dryer, - 50 ⁰ C and a vacuum of 25 Torr for 24 hours to obtain a cold-water soluble instant tea powder ϊο to win. This instant product obtained in high yield, designated as Product A in Table 1 below, when converted into a drink with cold water at the normal solids concentration of about 0.35%, was remarkably tea-like, excellent in color and milk reaction, as typical of beverage starch infusions, such as commonly made from black tea leaves.

Products B ₁ , B ₂ and B ₃

The procedure used to prepare product A was repeated using the same amounts of material except that no hydrogen peroxide was added during fermentation b5. The dissolved oxygen levels remained constant at 25% for about 45 minutes when the expected rapid increase in the level of dissolved oxygen in the extract was observed. All subsequent steps in the preparation de; Product A were followed. The freeze-dried instant tea powder obtained in this way is designated as product B in Table 1 below. The same high yield of tea solids was obtained in making product B \ as was obtained in making product A, but product Bi was considerably lighter in color.

The process described above for the preparation of product B | was repeated with the amendment that in the conversion process, the length of the aeration time after the level of dissolved oxygen increased to over 40% saturation, was increased from 10 to 3C minutes. The freeze-dried instant tea powder, obtained according to this modified procedure, is designated as B2 in the following table 1! and was characterized as being more tea-like than product Bi of darker color and good red coloring.

The procedure was repeated for a further preparation, the extra ventilation time being increased from 20 to 6C minutes. The yield of this instant tea powder, designated as product B ₃ in Table 1 below, was similar to that obtained for products Bi and B ₂ , but product B had a much darker reddish tea color than products B ₁ and B ₂ .

Product C

The procedures used in making Product A were repeated using the equal amounts of material with the following modifications: (a) The tannase treatment before conversion tion was omitted, (b) a quarter of the amount of hydrogen peroxide was in the conversion mixture drive added and (c) Tannase enzyme treatment was added after conversion in the Homogena carried out. The post-conversion tannase treatment was initiated at the end of the day Conversion time by jetting the homogenate with nitrogen gas (in order to create anaerobic conditions fen) and adding 15 mg of Tannase S (a total amount of 300 enzyme units, as defined in Example 1) to the homogenate. Treatment was carried out at 45 ° C under nitrogen for 2 hours, after which the pH of the treated extract aul again the natural value of pH 5.6 was adjusted with 2 N KOH.

The results associated with this product, which is designated as product C, are compiled in Table 1 and show that tannase treatment after conversion leads to considerably lower process yields than tannase treatment before conversion (cf. process yields of product C with those for the products A, Bi, B; or B ₃ in Table 1). Furthermore, product C lacks the good tea-like color of product A, as shown by the higher tristimulus-L value, which indicates a very light coloration, and the lower tristimulus-a value, which indicates a lack of reddish coloration.

Products D and E

The procedure as described for product A was repeated with the following changes: (a) Die Tannase treatment prior to conversion was omitted for the entire experiment, (b) the hydrogen peroxide became out of the conversion process like

for product Bi omitted, and (c) after fermentation and separation of the converted tea extract from the tea leaf residue by filtration, the extract was divided into two equal parts of 240 ml, each of which contained 2.8% solids. One part was treated further as described for product A, with the modification that the defogging treatment with calcium chloride was omitted. The freeze-dried instant tea product obtained by this procedure was designated as product D. The second portion of the extract obtained as above was treated with tannase in the following manner: The extract was placed in a temperature-controlled water bath maintained at 50 ° C. and 15 mg of Tannase S enzyme was added, which was equivalent to a total of 300 μl · -, Enzyme Units is as defined in Example 1, or corresponds to 40 enzyme units per gram of tea solids extracted. The treatment was continued for 90 minutes, after which the pH of the treated extract was adjusted back to the natural pH of 5.6 2 »with 2N KOH. The treated with tannase and adjusted to the pH of the extract portion was polished and freeze-dried according to the method as described above for Product A, except that the Entschleierungsbehand- was omitted 2 ^r> lung with calcium chloride. The freeze-dried instant tea product obtained in this way was named product E.

The analytical results for products D and E are compiled in Table 1. These Results show that there is a striking improvement in the yield of instant cold water soluble tea solids is present, that is in the process yield if tannase treatment before conversion green tea leaf homogenate is applied, as can be seen by comparing the results for the Products A, Bi, B2 and B3 with those for that Products C, D and E in Table 1. Neither a tannase treatment after converting green tea leaf homogenates (product C) another tannase treatment after the extraction of extracts (Product E) are effective for increasing the yield of instant cold water soluble tea solids via the non-tannase treatment process (product D).

Besides being obtained in good yield from fresh green tea leaves the products A and B2 (Table 1) excellent instant tea qualities insofar as they have good cold water solubility, good reddish black tea color in solution, good tea taste and good milk reaction exhibited. The other products lacked one or more of these qualities.

Table 1

Effect of tannase treatment on instant tea products obtained from tea conversion system homogenates

product

Extraction Polishing Procedure Tristimulus Color
yield loss yield

Tannase treatment before conversion: 37.2 7.6 34.4

H2O2 added

Tannase treatment before conversion: 36.3 6.4 34.0

no H ₂ O ₂ added

Same as B ₁ : 20 minutes extra aeration 37.0 8.2 34.0

23.2 33.0 16.2

42.9 44.2 29.9

34.9 46.7 24.1

Same as B: 60 minutes extra ventilation 38.0

Post-conversion tannase treatment: 31.5
H ₂ O ₂ added (% amount)

No tannase treatment: 31.9

no H ₂ O ₂ added

Post-extraction tannase treatment: 31.9

no H ₂ O ₂ added

10.6 34.0 18.9 26.6 13.3

14.2 27.0 50.2 35.1 34.5

18.7 25.9 37.1 39.6 25.7

14.5 27.3 35.8 37.9 24.7

Example 2

The tannase treatment before the conversion and the peroxide addition conditions, as for the extraction of Product A described in Example 1 were repeated using different temperatures for the tannase treatment step. All other Conditions and treatment parameters were not

changed. In each case, the tannase treatment was carried out by adding 16 mg of tannase S enzyme preparation containing 320 units of enzyme activity to the tea leaf homogenate containing 171 g of tea leaves. The reaction mixtures would then be held at 25, 35, 45, 55 or 65 ° C. for 2 hours while the homogenate was sprayed with nitrogen gas. After the end of the tannase treatment, the temperature of the reaction mixture was adjusted to 25 ° C., and the further processing of the tea solids was carried out as described for product A in example 1. Double control tests were carried out at each temperature, whereby tannase was not added to the tea leaf homogenate, although the homogenate was kept for 2 hours at the stated temperature with constant spraying with nitrogen gas.

The results of these experiments follow in Table 2. These results show that tannase treatment of Tea homogenates the yield of cold water soluble instant tea solids at all temperatures of the Tannase treatments improved which were applied. Process yield increases of greater than 50% was achieved at the higher tannase treatment temperatures. Furthermore, the tannase treatment performed always to products with a darker tea-like color, indicating that the tannase treatment was effective in creating conditions conducive to obtaining cold water soluble colored In contrast to the sparingly soluble colored substances, the tea ingredients lead to form if the tannase treatment is omitted before conversion. Only at 65 ° C, the highest At the applied temperature, poor conversion of tea solids was observed as was indicated the light color of the final product. This effect was likely a consequence of the significant Inactivation of the tea leaf enzymes, namely polyphenol oxidase and peroxidase, which occur during the tannase treatment before the conversion takes place at the high temperature.

Table 2

Effect of the pre-conversion tannase treatment temperature on the results obtained from Tea Conversion Homogenates

Tannase treatment
before conversion

temperature

Extraction yield

Polishing loss process yield

Tristimulus color
L a

no 25th 32.5 18.9 26.4 34.9 36.7 24.3 Yes 25th 38.4 8.3 35.2 22.6 33.2 15.8 no 35 32.9 16.0 27.6 30.8 36.8 21.3 Yes 35 37.3 5.4 35.3 19.4 29.8 13.8 no 45 31.7 16.0 26.6 N. D. *) N. D. N. D Yes 45 37.0 3.8 35.6 20.7 31.9 14.9 no 55 31.2 16.8 26.0 N. D. N. D. N. D Yes 55 39.9 6.1 37.5 20.3 30.9 14.3 no 65 28.6 16.1 24.0 39.1 30.0 26.9 Yes 65 37.9 4.5 36.2 30.3 34.2 21.0

*) N. D. = Not determined.

example

A 200 g sample of ground green tea leaves was dissolved in 700 ml of water and made into cold water soluble ones Instant tea solids converted following the procedure of Example 1 for Product A. Die Tannase treatment before conversion was carried out using 20 mg of tannase S containing After conversion of 400 units of tannase activity for 2 hours at 45 ° C under nitrogen and extraction was the extract in three portions of 250 ml each with a content of 2.4% The solids were divided and the portions were defogged with calcium chloride as follows: The three servings treated by adding 1, 2 and 3% (on a tea solids basis) calcium chloride. The proportions were then held at 25 ° C for 45 minutes: Finally, the portions were centrifuged at 6900 g cleared for 10 minutes at 4 ° C and the polished extracts were freeze-dried

Analytical results (Table 3) show that the clarity of the cold water-soluble instant tea samples obtained varies when the amount of calcium chloride used is changed. An excellent one Clarity of the product was improved with only a slight loss with 3% calcium chloride treatment Tea solids are preserved as by the very little reduction in that obtained from this treatment Yield is shown

Tabel . 8.5 Procedure from
loot% related
on extraklions
yield of
36.2% Tristimulus color
L a 39.6 b veil effect
obtain 9.7 33.1 27.8 41.8 19.5 45 3 10.1 32.7 30.4 42.0 21.2 25th Example 4 32.5 31.6 Dry weight of
in ιΗΐί »Γ · θΓϊ A rai VorCTl / 21.9 8th green tea leaves
■ »hears ornnlf αηαη f * m ar ¹ ; the calcium chloride defogging treatment of instant tea products,
from a tea conversion homogenate system Calcium chloride polishing
amount of loss
%% 1 3 5

Five 171 g samples of ground green tea leaves containing 25% dry weight were treated as described for product A in Example 1, with the modification that the amount of tannase enzyme used in the tannase treatment prior to conversion was changed, 4 ml of hydrogen peroxide was added during the conversion and 3% calcium chloride was used in all defogging treatments. The amount of tannase used in the tannase treatment before conversion was 32, 16, 8, 2 and 0 mg of tannase S per sample, which is 18, 8, 4, 1 and 0 enzyme units (as defined in Example 1) per sample Gram g
Table 4 and show that using

2 (i tion of 8 units of tannase per gram of dry weight fresh green tea leaves have the highest extraction yields and the lowest polishing losses results. When the tannase used in the pre-conversion treatment is reduced to one unit per gram

2) Tea solids are reduced is the overall process yield low, and the result is comparable to the product as obtained without tannase treatment will. The use of 16 units per gram of tea solids, on the other hand, does not add anything

κι advantage.

Table 4

Effect of the amount of tanna applied in the pre-conversion treatment on instant tea products, obtained from tea conversion homogenate

Units of extraction, polishing

Tannase per gram of yield loss

green tea leaves "," /

Procedure Tristimulus color a yield L. 32.9 22.7 47.6 34.1 28.0 45.2 40.3 31.0 34.1 43.9 33.1 31.2 44.9 33.2 36.7

28.9 21.6 34.8 19.5 35.0 11.5 37.0 10.6 35.8 7.3 Example 5

Fin. 171-CT-MlICtPr!, Oi-rrmVilonor rrriinor TW> l-ilättf.r with

about 25% total solids was converted to an instant tea product using of the procedure for product A in example 1 with the following modifications: The tannase treatment before the conversion was followed exactly with the modification that a temperature of 45 ° C was used throughout was adhered to. The conversion procedure was modified to use a quarter of the Hydrogen peroxide addition, d. i. 4 ml of a 2 M solution. The defogging treatment was changed by using 3% (total tea solids basis) calcium chloride. According to this way of working instant tea product obtained has been recognized by skilled tea tasters as being remarkable in all respects found to be similar to a black tea leaf infusion.

32.8
31.1
23.6
21.7
25.4

A second experiment was carried out following the above process conditions mi ', der Modification so that the pH of the homogeneity is not! return was adjusted to pH 5.6 with 2N KOH after the tannase treatment. The conversion process was therefore initiated at the unusually low pH 4.7, which results from the tannase treatment before the conversion revealed. Very little color change was noticed during the conversion process in this case using with the result that the final product was light in color and had none of the red color which was desirable for black tea is characteristic. This is also reflected in the analytical values (Table 5) for these two Products displayed where a normal tristimulus-a Color value is found for the product with adjusted pH, but an unusually low value is obtained when the conversion process is in a homogenate with a pH as low as 4.7 is carried out. The difference was the eerineen

Enzyme activity attributed to natural tea enzymes, caused by the low pH 4.7 resulting from the tannase treatment resulting in a poor conversion of green tea solids leads to black tea. Thus, the second attempt revealed a slightly better process yield than the first

Attempt, presumably because of a lower conversion had taken place. However, the product obtained in the experiment was found to be unacceptable because of its found bad color. In fact, this product resembles an unconverted, tannase-treated one green tea extract

Table 5

Effect of pH on the green tea conversion process

Attempt no.

For the conversion process
used pH

Extraction yield

Polishing loss process yield

Tristimulus color L a

5.6

4.7

37.0
38.7

10.6 7.0 33.1
36.0

31.2
34.3

43.9 19.9

21.7 22.9

Example 6

Five 171-g samples of cryogenically ground Green tea leaves (26% dry weight) were prepared in the manner described in Example 1 for product A. treated with the modification that the duration of the tannase treatment changes before the conversion 4.0 ml of 2 M hydrogen peroxide was added during the tea conversion process and 3% calcium was applied for the defogging treatment. The anaerobic tannase treatment was at 25 ° C for 0, 15, 30, 60 and 120 minutes performed using 8 enzyme units per gram dry weight of green tea leaves, the pH being maintained at 5.6 by the addition of small amounts of 2N potassium hydroxide. At the At the end of this pre-conversion tannase treatment, aeration and conversion was started was vented and maintained 25% oxygen saturation in the reaction mixture at 25 ° C and a pH of 5.6. The pH was carried out to 5.6 during the conversion process Add small amounts of 2N potassium hydroxyc to maintain. Extraction, polishing and freezing Drying of the instant tea products was carried out as described for product A in example 1. Tue « Tannase treatment of 120 minutes before conversion was repeated, but without the addition of tannase; as a control.

The results obtained for the six products prepared as described above are shown in table ( compiled. All of these tannase treatments prior to conversion resulted in the production of good egg Black tea-like products, except that the 0-minute tannase treatment resulted in a product wel ches was lighter in color than the others. omission the tannase treatment resulted in an overall poor yield of cold water soluble tea solids which were too light in color to be considered satisfactory for a black tea product.

Table 6 Extraction Polishing Conversion to the Results, obtained from a b yield loss % % Procedure Tristimulus color 32.9 32.8 Effect of the duration of the tannase treatment before the 28.9 21.6 yield L. Tea conversion humogenate % 42.0 25.8 Tannase treatment 33.3 9.1 22.7 47.6 41.3 22.8 Time 34.9 11.1 41.6 22.5 (Min.) 35.1 12.4 30.3 37.3 42.2 23.0 control 37.6 14.4 31.0 32.9 41.5 22.4 (no tannase) 36.7 13.3 30.7 32.5 0 32.2 33.2 15th 31.8 32.2 30th 60 120

Example 7

A tea enzyme preparation is made from fresh tea leaves according to the procedure described by H. Co and G.W. Sanderson in "Journal of Food Science", 1971, Volume 35, Pages 160-164. The tea enzyme preparation is used in the tea conversion process described below. 1000 g of fresh green tea leaves are ground on a Fitzmühle. The leaves are ground then with enough hot water to make a 10: 1 ratio of water to leaf mass, and using the 3-cell countercurrent extraction system, described by Seltzer et al in US-PS

909 646/177

29 27 860, extracted. The extract is separated from the insoluble tea leaf residue by centrifugation separated to obtain an extract weighing about 10 kg and containing about 3.7% solids

Before the conversion, the extract is subjected to a tannase treatment by adding 04 g of tannase enzyme with a specific activity of 15,000 units / g. The extract is then kept at 25 ° C. for 60 minutes with gentle stirring. After completion of the tannase treatment before the conversion, the pH of the extract is adjusted to about 5.6. A soluble tea enzyme preparation, which is obtained from about 100 g of tea leaves according to the Co and Sanderson method as described above and which is in about 10 ml of solution is then added to the extract to bring about the tea conversion process. The extract is held at about 25 ° C during the conversion process. The extract is then aerated by jetting with air in a ratio sufficient to maintain the dissolved oxygen level at 25% saturation until the primary fermentation is complete, as indicated by a rapid increase in the dissolved oxygen level. The conversion is completed by continuing aeration of the extract in the same ratio for about 30 minutes after the end of the first fermentation period. The converted tea extract is unveiled and polished by adding 3.0% (based on the total tea solids) calcium chloride to the extract, cooling the extract to 10 ⁰ C, holding the extract at 10 ° C for 30 minutes and then clarifying the Extract by centrifugation. The polished extract is then concentrated to 20% solids and freeze dried.

The instant tea product, which is soluble in cold water, has a high yield of solids, and its color, taste and milk reaction are similar to those of freshly brewed black tea.

Example 8

Example 7 is repeated with only one major change in the procedure. The enzyme preparations, both natural tea enzymes and tannase, are immobilized and used in this form. Immobilization of both tannase S and the natural tea enzymes from fresh green tea leaves is effected by the diazo coupling process described in US Pat. No. 3,519,538. The process consists in attaching the corresponding enzyme to glass beads by means of a chemical coupling agent of the type bind, as described in the PS as an enzyme-azo-silane glass bead
Before using the immobilized

ίο Enzyme preparation preconditioned by stirring with Servings of Tea Extract Two consecutive preconditioning treatments including stirring of the extract and enzyme for 5 minutes at 50 ° C are preferred

The extract from fresh tea leaves is prepared according to the method of Example 7. 10 kg of the extract with a content of 3.7% solids are ^{treated with the immobilized Tannase S by adding glass beads with the enzyme to the extract at 50 °} C. The suspension is stirred for 120 minutes under constant nitrogen spray to ensure anaerobic conditions.

The suspension treated with tannase will

decanted and the pH adjusted to about 5.6 by adding potassium hydroxide Preparation of enzymes fixed from fresh tea leaves are added. The temperature of the suspension is kept at 25 ° C. Oxygen is passed through the suspension to maintain 25% saturation, until the primary fermentation is complete, as indicated by a rapid increase in the content dissolved oxygen is displayed. The conversion is completed by continuing to ventilate the Extract in the same proportion for about 30 minutes after the end of the primary fermentation period.

The converted tea extract is decanted and de-creamed, following the conditions as in Example 1 given. The de-creamed extract is then freeze-dried following the conditions as they are also given in Example 1. The freeze-dried powder when in cold spring water dissolved, shows good solubility in cold water, a light reddish tea-like color with a pleasant taste of good, freshly brewed black tea and a light pink color when milk is added.

Claims (2)

Patent claims: 1. A method of making an instantly soluble black tea powder by making a aqueous tea extract in a slurry of crushed green tea leaves in water, conversion the tea solids in the extract in black tea with the addition of natural tea enzymes either before or after separating the aqueous tea extract from the slurry and Drying of the converted tea extract to produce a tea powder, thereby g e - indicates that the aqueous tea extract with tannase prior to the transformation of green tea is brought into contact at pH values and temperatures at which it is active. 2. The method according to claim 1, characterized in that when separating the aqueous tea extract from the slurry of crushed green tea leaves before treatment with tannase a tannase immobilized on a solid support is used.