FORM 2 THE PATENTS ACT,1970 ( 39 of 1970 ) COMPLETE SPECIFICATION SECTION 10 TITLE A METHOD FOR MANUFACTURING COLD WATER INFUSING LEAF TEA" APPLICANT HINDUSTAN LEVER' LIMITED, a Company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166 Backbay Reclamation, Mumbai 400 020, Maharashtra,India The following specification particularly describes the nature of the invention and the manner in which it is to be performed The present invention relates to a method for manufacturing cold water infusing leaf tea- The method involves fermenting tannase pre-treaed dhool (macerated tea leaves) under solid-state conditions in the presence of hydrogen peroxide. The dried leaf product infuses in cold Mater to give good flavour and colour. Background and prior art Black leaf tea is traditionally produced by oxidising and drying freshly plucked green tea leaves. Tea, the beverage, is generally prepar ed in Coaoionwealth countries by brewing these tea leaves in freshly boiled water for a few minutes and adding milk, and perhaps a little sugar. However in some countries, notably the United States (or more accurately, parts thereof) tea is more commonly enjoyed as an iced beverage. Such a beverage cannot be prepared conveniently by infusing traditionally manufactured tea leaves in cold water. Instead, Americans either infuse the leaves in hot water, . remove the leaves and place the infusion in a refrigerator until it is ready to consume or place tea leaves in cold water in sunlight to infuse slowly over a period of hours. The numerous compounds in the leaves that give the beverage its unique organoleptics properties are only spraingly soluble in cold water. A more convenient option that has become available in the 1970's is the use of cold soluble tea—based powders.. There are numerous methods for making cold water soluble tea powders. United States patent specification US 4,051, 264 (Lipton/ Sanderson ) discloses a method for making a cold water soluble leaf tea extract. Tea leaves are pre— treated with tannase under anaerobic conditions to generate a cold—Mater infusing tea with good colour, yield and flavour. United States patent specification US 3,812,266 (Sanderson/Coggon) discloses a method that involves converting green tea to black using tannase and natural tea enzymes. The method also includes a tannase pre—treatment step, but in a slurry system, followed by oxidation by natural tea enzymes to convert green tea into black, and generate tea powders, which are both hot and cold water soluble. In some examples hydrogen peroxide is added, to "shorten the process". The proposed mechanism for enhanced cold—water soluble colour generation resulting from tannase—treatment (elev a ted epitheaflavic acid levels) is now known to be incorrect, and no mechan ism was presented to explain the effect of adding the hydrogen peroxide. European patent specificatin EP 760,213 AL (Unilever) discloses a method of enhancing colour in a tea—based foodstuff. The method involves using a tannase pre—treatment (on leaf or extract) followed by treatment with exogenous peroxidase and hydrogen peroxide to generate cold—soluble colour. International patent publication WO 97/ 40699 (Unilever) concerns tea processing with zeolites to generate colour. There are examples of adding zeolite following tannase treatment to generate cold—water soluble tea. United States patent specification US 4, 639,375 (P&G,Tsai) discloses treating black tea with tannase, together with other cell-wall digesting enzymes, to generate cold-water soluble instant tea powders. Convenient as cold water soluble tea powders can be, for many consumers the quality of the final beverage is not equal to that prepared from hot infused leaves. Other consumers prefer not to use powders as they perceive them to be artificial and there¬fore "unnatural". The present inventors have surprisingly found that it is possible to make a leaf tea that infuses in cold water to give a beverage with good colour and flavour that is as acceptable to consumers as a hot infused black leaf tea that has been refrigerated. Furthermore this product can be made by modifying the traditional black tea manufacturing process. Statement of the Invention In broad terms the present invention relaes to a method for preparing a cold water infusing leaf tea comprising the steps of macerating green tea leaves, treating the macerated leaves with tannase, fermenting the tannase—treated macerate in the presence of an amount of hydrogen peroxide that is sufficient to activate endogenous peroxidases, and drying the fermented leaf material to yield the cald water infusible leaf tea. The invention also relates to a method for generating colour species in a cold water soluble tea product comprising adding hydrogen peroxide to a tannase-treated macerate of green tea in a quantity that is sufficient for the en dogenous peroxidases to oxidise gallic acid liberated by the tannase treatment. "Tea" for the purposes of the present invention means leaf material from Camellia sinensis var. sinensis or Camellia sinensis var. assamica. it also includes rooibos tea obtained from Aspalathus linearis however that is a poor source of endo¬genous fermenting enzymes. "Tea" is also intended to include the product t of blending two or more of any of these teas. "Leaf tea for the purposes of this invention means a tea product that contains one or more tea origins in an uninfused form. "Cold water soluble" for the purposes of this invention means giving good colour, flavous and mouthfeel in a short infusion time i.e. less than 10 minnutes, but preferably less o than 5 minutes at a.temperature at or above 4 C. The macerated leaves are preferably tannase treated under anaerobic conditions. The process is effective without this anaerobic incubation provided sufficient tannase is used. The tannase treated macerate is preferably fermented under standarad conditions to produce elevated levels of theaflavins and gallic acid prior to the addition of hydrogen peroxide. For the avoidance of doubt the word "comprising" is intended to mean including but not necessarily "consisting of" or "composed of". In other words the listed steps or options need not be exhaustive. DETAILED DESCRIPTION OF THE INVENTION Tea manufacture, especially black tea manufacture, traditionally comprises four basic steps: withering, rolling, fermenting and firing. Withering is a process whereby the plucked tea leaves are stored for periods of time (perhaps up to 24 hours),during which they undergo various biochemical and physical changes which often includes a loss of moisture. Maceration follows the withering step, and traditionally the withered leaves are optionally rolled to bruise and crush the leaves i.e. break down the plant tissue structure. This will have the effect of liberating fermentable substrates and fermenting enzymes from within the plant cells and tissue. Modern tea manufacture usually includes this step however the plant cells and tissueis broken down by passing tea, which has usually been withered, through a cutting machine. The next step is commonly called fermentation but that is a misnomer. "Fermentation M is commonly used in the context of brewing alcohol to describe the action of exogenous enzymes. However in the tea world it is used to refer to the oxidative process that tea undergoes when certain endogenous enxymes and substrates are brought together by mechanical disruption of the cells by tearing or cutting the leaves.During this process colourless catechins in the leaves are converted to a complex mixture of yellow and orange to dark—brown . substances and producing a large number of aromatic volatile compounds. The colourful oxidation products include theaflavins and thearubigens. Theaflavins comprise several well—defined catechin condensation products that are characterised by their benzotropo-lone ring. Thearubigens are a group of undefined molecules with a large variance in molecular weight. They have a large variety of colours ranging from yellow to dark red and brown. The fermented product is fired and dried to give a black leaf tea. The firing involves heating and drying the tea to destroy the fermenting enzymes and thereby arrest fermentation. It results in a reduction of moisture content to below 5%, and also leads to further chemical oxidation and changes in tea aroma. This generally- involves exposing the tea to a blast of hot, dry air in a dryer. The present invention relates to method for making cold soluble black leaf tea. The present inventors have found that this can be achieved by modifying some of the steps of the traditional tea manufacturing process just described. A preferred embodiment of the Method of the invention is depicted in Figure 1. In that preferred embodiment freshly plucked green tea leaves are withered in the normal way using any of the art known techniques. Withering is not essential to the invention but it can be a useful means to enhance tea aroma and also to reduce initial moisture content (which is important as moisture will be added with the tannase and peroxide, and drying efficiency can be affected at high moisture contents i.e. greater than (76V,). The leaves are macerated, which could mean being comminuted by a rotorvane and/or by a number of CTC (cut-tear-curl) machines. In a first departure from traditional black tea manufacture the maceraed leaves are treated with tann ase (flavanol gallate esterase) to generate d egallated catechins and gallic acid. This subsequently leads to the generation of theaflavins and non-gal lated thearubigens during fermentation (which are more soluble than the gallated ones). The general reaction catalysed by tannase is the cleavage of gallate ester linkages, both on gallated catechins and also from other gallated compounds within the leaf. Tannase is also well known to imrove the clarity of tea products since galloyl groups are important in cream formation and tannase has been used extensively for the degallation and solubi1isation of black tea cream. Tannase is known to be useful for treating green tea prior to slurry fermentation. For example the aforementioned US 3,812,266 (Sanderson et al) discloses using tannase to reduce the amount of tea cream in liquors. Improved colours generated by the process were also noted. The present invention however does not require the tea to be suspended and fermented in a slurry. Indeed this would be counter—productive because the components necessary to give good colour and flav our from the leaf would be prematurely extracted into the slurry. Rather the tea is fermented under solid —state conditions. This is an important distinction. The inventors previously thought that extraction of the catechins into a slurry liquor was essential for efficient action of tannase. They were surprised that direct application of annase to the dhool in a solid-state led to efficient ( i.e. almost complete) catechin degallation and high levels of theaflavin generation. They were even more surprised that the leaf product infused in cold water. Tannase treatment degallates the gallated catechins ECG and EGCG to produce the degallated catechins EC and EGC . On subsequent oxidation during fermentation the catechins EC and EGC react to produce theaflavin . The tannase can be applied using a variety of art-known techniques. The present inventors prefer to dissolve tannase in water, spray the solution onto the dhool and leave the mixture to react for a suitable time at a suitable temperature. The tannase is applied to the dhool after an initial maceration ( for example, a first CTC cut) in a fine spray followed by subsequent cutting ( or example, a second or third CTC cut) to ensure adequate mixing. The dhool is preferably incubated under vacuum, or under anaerobic conditions for exmple in an atmosphere or nitrogen. This prevents fermentation occurring. It is preferable that complete degallation takes place before fermentation starts as this results in maximal theaflavin levels in the subsequent fermentation, which in turn leads to optimal colour generation. The present inventors postulated that one might increases the efficiency by which certain exogenous compounds can access certain endogenous compounds of solid state tea by using a vacuum to draw the exogenous molecules into the macerated tea leaves and into contact with the compounds therein. Vacuum infiltration per se is known . However it has been used to force substances between cells rather than into cells. And those subsances have tended to have small molecular weights. The present inventors have however developed a method for bringing certain exogenous compounds into contact with endogenous compounds found in tea that involves vacuum infiltrating macerated tea leaves with thos oxogenous compounds and applied it to modify certain properties of tea and tea based beverates. The extent to which this method allows even large molecules such as enzymes to access endogenous tea compounds and modify certain properties of tea has been truly surprising. For example, an infusion of tannase pre—treated tea has been found to have more than double the total theaflavin conent of a control and a six fold increase in TF1. Vacuum infiltration is a technique that is often used in the preparation of protoplasts from plant tissue, albeit to introduce substances between rather than into cell walls. Cut leaf tissue is incubated in a solution containing tannase. The suspension is then placed under vacuum and air is drawn from the intracellular spaces of the leaf particles, the enzyme solution is drawn in to replace it. The inventors have found that a vacuum less than 100 mbar is suitable for this. The major constraint when applying this method to tea dhoolis achieving access within the cells. Another major problem is that large volumes of water can seriously affect the quality of tea, by reducing oxygen uptake during fermentation. The results described in the Examples indicate that vaccum infiltration is a useful tool for introducing enzymes, for example tannase , into solid state dhool. When fermented, tannase treated dhool gives rise to black tea with high levels of theaflavin and no gallated species. This enables one to produce a range of novel teas. Vacuum assisted tannase treatment is much more effective in removing gallated species and enhancing additional TF formation than the equivalent treatment under ambient temperature and pressure. The vacuum allows the enzyme to penetrate the tissue and remove gallated species prior to fermen¬tation, they key feature of tannase driv en theaflavin enhancement, compared to simply applying the enzyme onto fermenting dhool and mixing in by hand. If at all possible the conditions should be adjusted to prevent any fermentation prior to or during tannase treatment. This can be achieved by using a stronger vaccum pump, holding the dhool under N sparge, or shortening the tannase 2 treatment. Tannase can be applied to the macerated tea by a simple dosing. However,spraying the tannase in a fine mist is preferably as it aids infiltration. Suitable conditions can be readily determined by experiment. Good results have been obtained with KIKKOMAN's tannase (KIKKOMAN is a trade mark of Kikkotnan- Corporation, Tokyo, Japan) in an amount of 1—100 mg/kg dhool, preferably 10—80 rog/kg dhool but more preferably 40-80 mg/kg dhool. Note: KIKKOMAN'S tannase has 50,000 tannase activity units/gram. Fermentation is preferably carried out at a pH in the range of 4.0 to 5.5. The fermentation temperature is preferably in the o range 15 to 40 C . Fermentation is preferably carried out for a time in the range 30 to 150 minutes, more preferably 105 to 120 minutes. However in a second departure from traditional black tea manufacture hydrogen peroxide is added, after a time that is sufficient to generate gallic acid and theaflavin during the fermentation step, to activate (or at least greatly enhance the activity of)endogenous peroxidase. Tea is known to contain natural peroxidase at high levels. It is also known that natural peroxidase can be activated (or have its activity enhanced) through the addition of hydrogen peroxide in a slurry system. J. Sci.Food Agric. vol. 32, p 920-932 (Dix., 1981) discloses such a system and process. The article mentions that peroxidase can oxidase tea polyphenols to form theaflavins and also thearubigens which may be similar and different to those produced under "normal" fermentations. However it does not offer any detailed understanding as to the chemistry at work. The present inventors have found that the endogenous peroxi¬dases have the potential to oxidise catechins to theaflavins and thearubigens, convert theaflavins to thearubigens and, unlike endogenous polyphenol oxidase, readily oxidise gallic acid. The combination of these reactions generates significant amounts of coloured compounds that are soluble in cold water. The chemistry involved here is represented in Figure 2. The hydrogen peroxide is added in an amount that is sufficient to activate endogenous peroxidases and oxidise gallic acid liberated by the tannase treatment. One skilled in the art can deter mine that by experiment. However the present inventors prefer to use between 100 and 200 ml of 2.0 to 2.5% hydrogen peroxide per kg dhool, but preferably 160 ml of 2.0V. hydrogen peroxide per kg dhool. Under normal conditions of tea manufacture peroxidase is largely inactive, due to the low endogenous levels of hydrogen peroxide and high activities of catalase. Measure¬ments have shown that all added hydrogen peroxide is consumed during the process, with none remaining in the final made tea. In contrast to the findings disclosed in the aforementioned US 4,051,264 the present inventors have found the combination of tannase treatm ent and subsequent activation of peroxide is critical for the manufacture of a product that gives good colour and acceptable taste. Product that was only tannase treated had a "sour" or "metallic" note. As one would expect, the colour and taste profile of a beverage made from the cold water infusing leaf tea of the present invention depends to a large extent on the source and quality, of the raw material, i.e. tea leaves. The present inventors have found that standard raw material, two leaves and a bud delivered to the factory within excess of 1100 shoots per kilogram green leaf tea, can be processed according to the method of the invention to give very good colour and taste. However during efforts to improve the colour and taste ev en further the inventors suprisingly found significant improvement to both can b< achieved by using more mature leaf. Tea is generally harvested as two leaves and a bud on a 17 day cycle to optimise quality and yield. Extending the cycle means the leaves will be more mature and their chemical composition will be a little different. One then needs to pluck larger portions of tea plant to account for the extra growth. Such a harvesting strategy increases the yield per hectare of tea and thus improves productivity but the harvested plant material tends to have Ion ger stems and a higher stem to a leaf ratio. Black tea made from mature tea leaf material tends to be less coloured and thinner after infusion than black tea made from tea portions of two leaves and a bud that are harvested on a 17 day cycle. However, the present inventors surprisingly found that when mature leaf tea, i.e. tea leaves harvested on a 30 to 50 day cycle in portions of 3 to 5, but prefer-ably 4 leaves and a bud, is used there is a sufficient increase in cold water infusion performance and thus an improvement in colour and taste. While not wanting to be bound by theory, it is thought that mature leaf material (including stalk) contains higher levels of. peroxidase than standard leaf and this peroxidase provides an important role in the maturation cascade. This means more peroxidase is av ailable when hydrogen peroxide is added when carrying out the method of the invention. Consequently more colour is generated by an enhanced peroxide/peroxidase oxidation system. The method of the invention will now be described with reference to the following examples and the accompanying drawings. In the drawings: Figure 1 is a diagram that shows a preferred process layout of the invention. Figure 2 is a diagram that represents that chemical reactions that tannase and endogenous peroxidase catalyse to give highly coloured thearubigens. I Figure 3 is a formulation profile of tannase-perpxide treated partially fermented dhool (Example 1). Figure 4 is a histogram comparing the colour characteristics of tannase—peroxide treated and untreated tea infusions (Example 3). Figures 5 and 6 represent the fermentation profiles for the experiments described in Example 4a. Figures 7 and 8 show the composition of tannase-peroxide processed black teas obtained using various tannase dosages (Example 5) . Figures 9a to 9e are infusion profiles of untreated and o o o o tannase-peroxided treated teas at 4 C, 15 C, 25 C,55 C o and 70 C respectively (Example 6). EXAMPLE 1 Lab scale process (a) Process steps 60 mg tannase dissolved in 24 ml water was sprayed onto 100 g of frozen dhool. The dhool was then thawed under N and once 2 o it had reached 20 Cit was placed under vacuum (50 mbar) for 60 o minutes. The dhool was then fermented for 60 minutes at 25 C , 100% RH. Afer fermentation the dhool was sprayed with 12.5 ml 2'/. hydrogen peroxide solution, placed under vacuum for 15 minutes and then dried by a fluid bed drier (conventional FBD). One can increase the level of theaflavins by pre-treating the dhool with tannase. Peroxide is added to activate the endogenous tea peroxidase. This enzy me oxidises theaflavins and the gallic acid released by tannase to give dark, cold water soluble pigments. The fermentation profile is represented in Figure 3. (b) Taste testing A cold water infusion made from tea prepared by the process just described was ta ste tested by an experienced tea taster. The infusion was made in 200 ml of carbon filtered water for 5 o minutes at 15 C. The treated sample was described as having a. "fruity note, good mouthfeel, astringent, lots of body, low aromatics, good colour, good ice tea product, stands up to ice" whilst the control, standard black tea, was described as "bland". The results of colour, haze and solids analyses are given in Table 1 below where L is a measure of luminosity and a is a measure of red/green colour as determined using a MINOLTA (TM ) colorimeter. EXAMPLE 2 Colour.comparison with other products Table 1: Lab scale process product Dhool was treated in treated in accordance with the basic lab scale process described above (60 mg tannase, dried immediately afer peroxide addition). The colour of the liquor obtained from this product was compared with that obtained from a commercially available product (SHOOTHBLEND /J1 aliquot was then added to 800 1 antioxidant solvent and then analysed by reverse phase HPLC using diode array detection . Dry weight measurement The dry weight of dhool samples were determined by mass o difference fallowing drying at 100 C overnight. Results are expressed on a dry weight basis because moisture changes during N sparge, and following tannase addition make a fresh weight 2 basis unreliable. Preparation of tea infusions Infusions were prepared at 1% (w/v) tea solids, 5 minutes infusion time. EXAMPLE 4a Effectiveness of tannase against solid state dhool In the first experiment, after thawing under N * 2 , 8 g dhool was held under vacuum (using bench top vacuum tape) and 1 ml tannase solution was pipetted on to the dhool (5 mg/ml tannase, 31. 25 ug (dhool)) and left for 60 minuts. Catechin composition was determined before and after this treatment. The results are given in Table 4 below : TABLE 4: Effect of tannase addition under vacuum on catechin composition of BBK35 dhool Degallation was almost entirely complete with only 5 /j mol/g (DW) residual E6CG after 60 minutes. The d ecrease in EGCG and ECG (total - 198 μ mol/g (DW) was exactly mirrored by the increase in gallic acid (+200 μ m mol/g (DW) . However there was also evidence that some fermentation had taken place during the process ; 13/Jmol/g (DW) TF had formed and the increases in EGC and EC were not as high as predicted from the decreases in EGCG and EC were not as high as predicted from the decreases in EGCG and ECG. There were no gallated theaflavins present. The increase in TF accounts for the missing EC/ ECG but not the ECG/ EGCG which suggests that some thearubigins were formed- as well. These results indicate that some fermentation was occurring during the tannase treatment and that perhaps small amounts of gallated theaflavins were being formed and then degallated. Although it was surprising that there was a degree of fermentation under vacuum, it may be that the vaccum was not sufficiently strong to prevent it or that the apparatus used was not absolutely air tight. Nonetheless this proves that vacuum infiltration of tannase is very effective in degallating gallated catechins. In the next experiment, the process was scaled up so that samples could be taken during the fermentation ( to follow the profile of catechin oxidation) in solicd state dhool following tannase treatment. Dhool (25 g) was thawed under NJI_ and treated with 15 mg tannase dissolved in 6 ml water and then held under vacuum for 60 minutes. At the end of this treatment the dhool was transferred to a controlled environment cabinet and fermented at o 25 C , 100*/. RH (relative humidity), for 2 hours. Samples were taken at 30 minute intervals to follow the fermentation profile. The results are given in Table 5 below. TABLE 5. Changes in catechins during Tannase treatment prior to fermentation Once again degallation was almost complete with on 9 mols of EGCG remaining after 60 minutes in tannase treatment. It would seem the increases in gallic acid accounted for the combined decrease in EG CG/EC6 . However the increases in EGC and EC did not account for the decreases in EGCG and ECG, which indicated that again some fermentation had taken place during the tannase treatment and indeed some theaflavin had formed. # The fermentation profile for this experiment is shown in Figure 5 (see the drawings) . EGC and EC were completely oxidized by 90 minutes, and theaflavin levels peak at over Aa^mol/g DW (ie dry weight). The enhancement in theaflavin following tannase pre-treated fermentation of solid state dhool, is compared to a standard tea prepared from the same batch of dhool in Figure 6 ( see the drawings). In any case these experiments demonstrate the vacuum infil¬tration enhances the ability of tannase to degallate catechin gallates and provides a raw material suitable for the formation of high levels of theaflavin during fermentation. However, some fermentation is occurring during the tannase treatment. EXAMPLE 4b Preparation of black tea with enhanced theaflavin level level Having produced fermented dhool with enhanced theaflavin levels the next was to use this method to produce a tannase treaed black tea so that the properties of the infusion could be assessed. The process was further scaled up to 100 g of dhool so that the maerial could be fluid bed dried after fermentation. The dhool (100 g) was thawed under N2 and 24 ml H20 containing 60 mg tannase added. The dhool was then placed under vacuum, using an EDWARDS (TM) vacuum pump for 60 minutes. Afer this time the dhool was placed in a controlled environment chamber and o fermented at 25 C, 100% RH for 120 minutes. After this the dhool was fluid bed dried. A replicate batch of tea was also prepared but without any tannase addition. Catechin levels before and after tannase treatment and after fermentation are shown in Table 6 below. As one can see. degalation of EGCG was only 75/C complete, but there was good agreement between the reductions in EGCG and ECG and the increases in EGC and EC. Moreover there was no theaflavin formation during the tannase treatment, this indicated that under stronger vacuum provided by the pump no fermentation was taking place. Overall there is a 10 fold increase in TF1 and a 4.3 fold increase in total TF was observed in the fermented dhool (determined by solvent extraction). EXAMPLE 5 Process optimisation (a) Optimisation of tannase dosage Varying tannase dosage. A range of samples were prepared with increasing tannase dosage, between 5 and 320 mg tannase/kg. The ■ * " * results are given in Table 7 below where L , a* and b are as before. TABLE 7: Colour analysis of tannase/peroxide processed black teas These results show the teas darkened (lower L-value) and increased in colour