DE2304073B2 - 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 a high proportion of soluble solids. When the black tea in an instantly soluble (instant) tea powder should be convicted, it should contain a minimum of "tea cream", that is by hot water extractable solids, but which are insoluble in cold water. The present invention refers to a pre-treatment of the unfermented tea, which after the conversion one provides black tea with these desirable properties.

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

so 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: 1, 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 homogenizing 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 kept to any premature fermentation to avoid. Maintaining anaerobic conditions can be accomplished through introduction 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 belong. For example Aspergillus flavus, grown on a medium in which tannic acid is the only one Contains carbon source, tannase supplies in considerable quantities. Two specific strains of these microorganisms, known for producing significant amounts of tannas, Aspergillus oryzae ATCC No. 9362 and Aspergillus niger ATCC No. 16 888. A suitable tannase preparation obtained with a strain of Aspergillus oryzae is commercially available as a powder. The amount of tannase enzyme preparation which added to the slurry is generally from 1 to 16, preferably about 8, enzyme units per gram Dry weight of tea as measured by the Iibuchi et al method, which will be described later. Tannase S has approximately 20,000 enzyme units per gram of powder when measured according to this method.

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

Following the completion of the pre-conversion tannase treatment, the tea conversion procedure is followed caused by adjusting the temperature of the tea leaves, pulp or homogenate about 25 ° C and jetting with air If the level of ventilation is set to about 25% oxygen saturation Maintaining in the pulp will have a satisfactory conversion in about 80 minutes achieved. Hydrogen peroxide can be added to the tea leaf homogenate in controlled amounts to reduce the Shorten conversion time. The hydrogen peroxide usually becomes uniform over a time of added about 20 minutes, beginning about 15 minutes after the start of ventilation. The end of the tea conversion process is displayed when the level of oxygen saturation in the tea leaf pulp suddenly increases. Ventilation is on for about up to 30 minutes after this increase in oxygen saturation, preferably continued for about 10 minutes if hydrogen peroxide is used. The conversion process is then by heating the pulp to about 85 ° C for about 5 minutes by killing the natural tea enzymes terminated.

An alternative method of working uses an aqueous extract of green tea leaves as the starting material. at This way of working, the extract is given a tannase treatment before conversion, and that The tea conversion process is then effected by combining the tannase treated 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 Si I m e et al in "Annual Review of Biochemistry", 1966, Volume 35, pages 873 to 908, in the article "Colloquim on Insolubilized Enzymes", Biochemical Journal, 1968, Volume 107, pages IP to 6P, and by H. Weetal in "Enzymes Immobilized on Inorganic Carriers by Covalent Attachement", Research / Development, 1971, Volume 22, Pages 18 to 22, described in In general, the processes for insolubilizing enzymes require the enzyme to be attached to one 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 a green tea extract, the method of the invention is preferably carried out at a pH within one unit of the natural pH of tea infusions, which is about pH 5.6. The pre-conversion tannase treatment is preferably carried out at a pH of about 5. The tea conversion step is preferably carried out within the pH range 4.8 to 6.0, most preferably about 5.6. The pH which falls as a result of the tannase treatment is preferably adjusted prior to the conversion step, for example with potassium hydroxide.

The product of the conversion process in which a green tea extract is made from the raw material is used is a black tea extract. When a pulp or homogenate of green tea as the starting material can be used, the product of the conversion process into an extract and tea leaf residue by filtration, centrifugation or any other method of operation. The leaf residue can be extracted again with water, if desired, to the amount of that obtained in the extract To enlarge tea solids, and the material so extracted can become the first extract obtained can be added. The black tea extract obtained by one of the above methods can be used concentrated and dried using standard procedures including freeze-drying and spray-drying to give a cold water soluble instant tea powder. The extract will preferably defogged by adding calcium chloride and centrifuged before concentration and Drying. The amount of calcium chloride added is preferably about 3% by weight of the tea solids, and convenient centrifugation conditions are 6900 g at 10 ° 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, which leads to the formation of cold water soluble tea pigments 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 Connections which, as is known, are converted into unconverted Tea leaves are present, which catalyzes in

OH HO I OH

The reaction in question will presumably be a deesterification, which is carried out according to the following scheme can run:

(Tannase + H ₂ O)

C = O O

- »ROH +

C = O

OH

wherein ROH means any of several different compounds found in green tea leaves are present, including epicatechin 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 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 analytically pure tannic acid. 3.0 ml of this solution are placed in a 1 cm cuvette, which is kept at 30 ^° C. in the temperature-controlled sample chamber of a recording Cary Model 14 ultraviolet spectrophotometer. Finally 0.1 ml of 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 the activity which a change of 1 Absorbanseinheit per minute at 310 mm (30 ⁰ C, 1 cm cell) will be using a O, OO4 ° / o tannic acid in 0.02 M acetate buffer (pH 5.0) with an initial absorbance of about 0.7.

Three deliveries of tannic acid were made in this case Exam 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 Testing 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, 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 the tea solution. The tristimulus color determination is based on the measurement of transmitted light. The L value is the lightness factor: a value of 100 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. When analyzing tea solutions at beverage strength, that is 0.35% tea solids in a 5 cm cell, the preferred L value is in the range of 20 to 35, the preferred a value is at least 8 units greater than the L value, and the preferred b value is between about 15 and 25.

example 1

Fresh green tea leaves obtained from a tea plantation in Charleston, South Carolina, were frozen at -40 ⁰ 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 sample of the ground fresh tea leaves, with a total solids content of about 25%, was made into a slurry with 600 ml of water in a reaction vessel and nitrogen gas was bubbled through the system while the temperature was raised to 25 ° C by recirculating it Temperature regulated water was maintained by the mantle.
The Tanr.ass treatment before conversion

was carried out by adding 16 mg of Tannase S Enzyme containing 320 units of activity to the tea leaf homogenate and maintaining the homogenate under anaerobic conditions by means of continuous spraying with nitrogen for 2 hours at 5 25 ° C. At the end of the tannase treatment period, the pH of the green tea leaf homogenate was 4.7 fallen, and therefore it was necessary to bring the pH of the homogenate back to the initial pH of 5.6 using Adjust 2 N KOH. ι ο

The enzymatic conversion of the green tea was then carried out in the following manner Fermentation was started by changing the spray gas from nitrogen to air. The extent the aeration was adjusted to reduce the amount of dissolved oxygen in the homogenate to 25% To keep saturation. The temperature was kept at 25 ° C throughout the following conversion. The constant gas flow rate maintained the amount of dissolved oxygen in the homogenate steadily to 25%. After 15 minutes of aeration, a 2 M hydrogen peroxide solution was added dropwise during added over a period of 20 minutes so that the total volume of added hydrogen peroxide solution Was 16.0 ml. The conversion was continued for about an additional 10 minutes until the solution was resolved Oxygen level began to increase rapidly from 25% to about 40% saturation in the homogenate. the Aeration was continued for an additional 10 minutes, followed by conversion by switching the spray gas was interrupted from air to nitrogen, and the pH was again with 2 N KOH adjusted back to pH 5.6 which is the natural pH of most converted tea infusions is ·

The converted homogenate was heated to 85 ° C. and held at this temperature for 5 minutes. The tea extract was then made from the spent tea leaves by filtering the heated homogenate Separated by Miracloth. Calcium chloride (1% on a tea solids basis) was added to the filtered Tea extract was added and the solution was kept at 25 ° C for 45 minutes. Eventually the The extract was cooled to 4 ° C. and polished by centrifugation at 6900 g for 10 minutes. The polished Extract was then freeze dried in a Stokes P-9 freeze dryer operated at shelf temperature of 95 ° C, a plate temperature of -50 ° C and a vacuum of 25 Torr for 24 Hours to make a cold water soluble instant tea powder. This obtained in high yield Instant tea product, referred to as Product A in Table 1 below, when in a beverage with cold water at the normal solids concentration of about 035% was remarkable tea-like, of excellent color and a milk reaction, as is typical for beverage starch infusions, as usually made from black tea leaves

Products Bi, B ₂ and B ₃

60

The procedure used to prepare Product A was repeated using equal amounts of material except that no hydrogen peroxide was added during the fermentation. 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 of Product A were followed. The freeze-dried instant tea powder obtained in this way is designated as product Bi 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 procedure described above for the preparation of product Bi was repeated with the modification 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 by this modified process is designated as B2 in Table 1 below and was characterized as more tea-like than product Bi before 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 B3 in Table 1 below, was similar to that obtained for Product Bi and B2, but Product B; had a much darker reddish tea color than Produki Bi and B ₂ .

Product C

The procedures used in making Product A were repeated using the same amounts of material with the following modifications: (a) the tannase treatment prior to conversion was omitted, (b) a quarter of the amount of hydrogen peroxide was added in the conversion procedure, and (c) a tannase enzyme treatment was carried out in the homogenate after the conversion as defined in Example 1) to the homogenate The treatment was carried out at 45 ^° C. under nitrogen for 2 hours, after which the pH of the treated extract was adjusted back to the natural value of pH 5.6 with 2 N KOH.

The results pertaining to this product, which is designated as product C, are summarized 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, B2 or B ₃ in Table 1). Furthermore, product C lacks the good tea-like color of product A, as shown by the higher tristimulus Z value, which indicates a very light color, and the lower tristimulus a value, which indicates a lack of reddish color

Products D and E

The procedure as described for product A was followed repeated with the following changes: (a) The pre-conversion tannase treatment was applied to omitted the whole experiment, (b) the hydrogen peroxide was from the conversion process like

ίο

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.A part was further treated, 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 above was treated with tannase in the following manner: the extract was placed in a temperature-controlled water bath kept at 50 ^° C. and 15 mg of Tannase S enzyme were added, which is equivalent to a total of 300 enzyme units, as defined in Example 1, or 40 enzyme units per gram of tea solids extracted. Treatment was continued for 90 minutes, after which the pH of the treated extract was readjusted to the natural pH of 5.6 with 2N KOH. The tannase-treated and pH-adjusted portion of the extract was polished and lyophilized according to the procedure described above for Product A except that the calcium chloride defogging treatment was omitted. The freeze-dried instant tea product thus obtained was called 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, B), 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 Inst an t 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

H ₂ O ₂ added

Tannase treatment before conversion: 36.3 6.4 34.0

no H ₂ O ₂ added

Same as Bj: 20 minutes extra ventilation 37.0 8.2 34.0

Same as B ₁ : 60 minutes of extra ventilation 38.0 10.6 34.0

Post-conversion tannase treatment: 31.5 14.2 27.0

H ₂ O ₂ added ( ¹ A amount)

No tannase treatment: 31.9 18.7 25.9

no H ₂ O ₂ added

Post-extraction tannase treatment: 31.9 14.5 27.3

no H ₂ O ₂ added

23.2 33.0 16.2

42.9 44.2 29.9

34.9 46.7 24.1

18.9 26.6 13.3

50.2 35.1 34.5

37.1 39.6 25.7

35.8 37.9 24.7

Example 2

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

12th

In each case, the tannase treatment was changed by adding 16 mg of tannase S enzyme preparation containing 320 units of enzyme activity to the tea leaf homogenate containing 171 g Tea leaves carried. The reaction mixtures were then each at 25, 35, 45, 55 or 65 ° C for 2 hours held while the homogenate was sprayed with nitrogen gas. After finishing the tannase treatment the temperature of the reaction mixture was adjusted to 25 ° C, and the further processing of the Tea solids were carried out as described for Product A in Example 1. Double check attempts were made carried out at any temperature with no tannase added to the tea leaf homogenate, although the homogenate was kept under constant spray for 2 hours at the specified temperature Nitrogen gas was held.

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

10

15 tannase treatment improved which were applied. Process yield increases of greater than 50% were achieved at the higher tannase treatment temperatures. Furthermore, the tannase treatment always resulted in products having a darker tea-like color, indicating that the tannase treatment was effective in creating conditions which resulted in the recovery of cold water-soluble colored tea ingredients as opposed to the sparingly soluble colored substances which form when the tannase treatment is omitted before conversion. Only at 65 ° C, the highest temperature used, was poor tea solids conversion observed, as indicated by the light color of the final product. This effect was probably a consequence of the considerable inactivation of the tea leaf enzymes, namely polyphenol oxidase and peroxidase, which takes place during the tannase treatment before the conversion at the high temperature.

Table 2

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

Tannase Treatment Temperature Extraction Polishing Process

before the conversion yield loss yield

tation o _{r 0 /} ",",

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

*) RD. = Not determined

Example 3

A 200g sample of ground green tea leaves was dissolved in 700 ml of water and converted to cold water soluble instant tea solids according to the following the procedure of Example 1 for product A. The tannase treatment before conversion was under Using 20mg of TannaseS with a content 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 were 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 clarified by centrifugation at 6900 g 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

Table 3

Effect of calcium chloride defogging treatment on instant tea products, obtained from a tea conversion homogenate system

Calcium chloride Polishing Procedure from Tristimulus color a b veil lot loss loot% related L. 0 / on extraction A. / 0 yield of 36.2% 39.6 19.5 45 1 8.5 33.1 27.8 41.8 21.2 25th 3 9.7 32.7 30.4 42.0 21.9 8th 5 10.1 32.5 31.6

Example 4

Five 171g samples of ground green tea leaves with a content of 25% dry weight were treated in the same way as for product A in example 1 is described with the modification that the amount of the in the tannase treatment before the conversion The tannase enzyme used was changed, 4 ml of hydrogen peroxide were added during the conversion and 3% calcium chloride was used in all defogging treatments. the 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 gram

Table 4

The dry weight of the green tea leaves corresponds to the results obtained in these three experiments are in Table 4 compiled and show that use 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 Tea solids is reduced, the overall process yield is low and the result is comparable to the product as obtained without tannase treatment. The use of 16 units per gram Tea solids, on the other hand, gives no additional benefit.

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

Units Extraction Polishing Procedure A
miner Tristimulus color O O Tannase per g yield loss yield / 32.9 32.8 green tea leaves % % % L 34.1 31.1 0 28.9 21.6 22.7 47.6 40.3 23.6 1 34.8 19.5 28.0 45.2 43.9 21.7 4th 35.0 11.5 31.0 34.1 44.9 25.4 8th 37.0 10.6 33.1 31.2 executed
rKa / iinminiT under befol 16 35.8 7.3 33.2 36.7 Example 5 second attempt was
H Pr r \\ yi tr & rt decay ro-n

A 171 gram swatch of ground green tea leaves with a total solids content of about 25% became an instant tea product using the procedure for Product A in Example 1 with the the following changes: The tannase treatment before conversion was followed exactly with the Modification that a temperature of 45 ° C was maintained throughout. The conversion process was modified by using a quarter of the hydrogen peroxide additive, d. i. 4 ml of a 2 M solution. The defogging treatment was modified to use 3% (total tea solids basis) Calcium chloride. The instant tea product obtained according to this procedure has been known by those skilled in the art Tea tastes as being remarkably similar in all respects to a black tea leaf infusion found.

Modification so that the pH of the homogenate does not return to pH 5.6 with 2N KOH after the tannase treatment was discontinued. The conversion process was therefore initiated at the unusually low pH 4.7, what resulted from the tannase treatment prior to conversion. Very little color change was seen during the Conversion process in this case noticed that the final product was light in color and had none of the red color characteristic of black tea. This is also used in the analytical widths (Table 5) for these two products are shown where a normal tristimulus-a color value is found for the pH adjusted product, 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 minor one

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

Attempt, presumably because of a lower conversion However, the product obtained in Experiment 2 was found to be unacceptable because of its found bad color. In fact, this product resembles an unconverted one. tannase-treated green tea extract.

Table 5

Effect of pH on the green tea conversion process

Attempt no.

For the conversion process
used pH

Extraction yield

V.

5.6
4.7

37.0
38.7

Polieningsvertust process yield

10.6 7.0 33.1
36.0

Tristimulus color
L a

3 U
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 carried out at 25 ° C for 0, 15, 30, 60 and 120 minutes using 8 enzyme units per gram dry weight of green tea leaves, the pH being reduced to 5.6 by adding small amounts was maintained on 2 N potassium hydroxide. At the end of this tannase treatment before conversion aeration was started and the conversion was carried out with aeration and maintenance of 25% Oxygen saturation in the reaction mixture was carried out at 25 ° C and a pH of 5.6. The pH was raised to 5.6 during the conversion process by adding small amounts of 2N potassium hydroxide maintain. Extraction, polishing and freeze drying of the instant tea products were carried out as described for product A in example 1. The tannase treatment of 120 minutes before the conversion was repeated, but without the addition of tannase as a control.

jo The results obtained for the six products Prepared as described above, all of these tannase treatments are summarized in Table 6 of conversion resulted in the production of good black tea-like products, except that the O-minute tannase treatment gave a product which was lighter in color than the others. Omission of the tannase treatment resulted in an overall poor yield of cold water soluble tea solids which were too light colored to be satisfactory for to be considered a black tea product.

Table 6

Effect of duration of tannase treatment before conversion on the results obtained from Conversion homogenate

Tannase treatment time

(Min.)

Extraction yield

Loss of polishing

Process yield

Tristimulus color

L a

control 28.9 21.6 22.7 47.6 32.9 32.8 (no tannase) 0 33.3 9.1 30.3 37.3 42.0 25.8 15th 34.9 11.1 31.0 32.9 41.3 22.8 30th 35.1 12.4 30.7 32.5 41.6 22.5 60 37.6 14.4 32.2 33.2 42.2 23.0 120 36.7 13.3 31.8 32.2 41.5 22.4

Example 7

A tea enzyme preparation is made from fresh tea leaves according to the procedure described by H. C o and G. W. Sanderson in "Journal of Food Science", 1971, volume 35, pages 160-164. The tea F-n / vm / ureitiinp is used at the below tea conversion process described is used. 1000 g of fresh green tea leaves are put on one Fitzmühle marry. The ground leaves are then mixed with hot water enough to make a 10: 1 ratio of water to leaf mass, and using the 3-cell countercurrent extraction system, described by Se'tzer et al in US-PS

909 513/156

29 27 860, extracted The extract is extracted from the insoluble tea leaf residue by centrifugation separated to obtain an extract which is about Weighs 10 kg and contains approximately 3.7% solids

The extract. is subjected to a tannase treatment before conversion by adding 0.5 g Tannase enzyme with a specific activity of 15,000 units / g. The extract is then stored at 25 ° C held for 60 minutes with gentle stirring. After finishing the tannase treatment before Conversion, the pH of the extract is adjusted to around 5.6 A soluble tea enzyme preparation which obtained from about 100 g of tea leaves according to the Co and Sanderson method as described above and which is contained in about 10 ml of the solution, is then added to the extract for the tea conversion process bring about. The extract is brought to around 25 ° C during the conversion process held. The extract is then aerated by spraying with air in a ratio sufficient to achieve the keep dissolved oxygen content at 25% saturation until primary fermentation is complete, as indicated by a rapid increase in dissolved oxygen levels 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 de-veiled and polished by adding 3.0% (based on total tea solids) calcium chloride to the extract, cooling of the extract at 10 ° 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. The 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 To bind type, as it is 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 ⁰ C. The suspension is stirred for 120 minutes under constant nitrogen spray in order to ensure anaerobic conditions.

The suspension treated with tannase will

decanted and the pH to about 5.6 by adding

2> Potassium hydroxide set. Glass beads on which the 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 ratio for about 30 minutes

j-) 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 one

4 ^r > 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 flakes 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 for the production of a tea powder, thereby 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 that when separating the aqueous tea extract from the slurry of crushed green tea leaves prior to treatment with tannase a tannase immobilized on a solid support is used.