Claims:1. A process to make a black leaf CTC tea product with higher yield of a desired particle size comprising the steps of:
withering green leaf tea;
reducing the size of the withered green leaf tea;
extrusion of size reduced leaf tea;
granulation in a spheronizer;
fermentation;
drying; and
sorting to give the black tea product, wherein extrusion takes place before granulation and fermentation step.
2. The process as claimed in claim 1, wherein reducing size of the withered green leaf tea is carried in CTC (cut-tear-curl) machine.

3. The process as claimed in claim 1, wherein the extrusion takes place in a twin screw extruder.

4. The process as claimed in claim 1, wherein the extrusion takes place in a co-rotating twin screw extruder.

5. The process as claimed in claim 1, wherein the extrusion in the twin screw extruder is at ambient temperature.

6. The process as claimed in claim, wherein the twin-screw extruder is provided with a dome shaped screen of mesh size in range from 1mm-4mm.

7. The process as claimed in claim 1, wherein the granulation in spheronizer at takes place at 100 rpm to 300 rpm.

8. The process as claimed in claim 1, wherein the extruded pellets are in spheronizer for 2 min. to 3 min.

9. The process as claimed in claim 1, wherein the extrudate is shaped into a substantially spherical shape in a spheronizer.

10. The process as claimed in claim 1, wherein the fermentation step occurs after the extrusion and granulation step.

11. The process as claimed in claim 1, wherein the fermentation takes place for 90 minutes to 120 minutes at room temperature.

12. The process as claimed in claim 1, wherein the drying is done at temperature range 55 °C to 150 °C and for 10 minutes to 20 minutes followed by sorting.

13. A black leaf CTC tea product obtained from the process as claimed in claim 1 to 12, wherein the tea granules are 25% denser.
, Description:FIELD OF THE INVENTION
[0001] The present invention relates to a novel process of manufacture of a black leaf CTC tea product of desired granule size with increased bulk density. More particularly, the invention relates to a modification of the standard method of CTC black tea manufacture that provides a significant improvement in control of final grade/grades of tea with enhanced granulation and reduced fines and dust.

BACKGROUND OF THE INVENTION
[0002] Leaf tea can be prepared in the form of green leaf tea or black leaf tea. To prepare black leaf tea, fresh green young leaves usually 2-3 leaves and a bud are plucked of the plant Camellia sinensis and are subjected to mild drying by blowing air on them (withering stage). The withering process is carried for about 12-24 hours. During the course of withering, the moisture content in the leaf goes down by about 30%, making the leaf look limp and soft enough for rolling. Additionally, the volatile compounds in the leaf, including the level of caffeine and the flavours, begin to intensify. The tea leaves are then macerated (reduction of size) using a Cut-tear-and curl machine (CTC machine). The macerated leaves are processed to reduce the size of the leaf and to disrupt the cell structure (the size reducing stage), fermented (in which process enzymes in the tea leaf use atmospheric oxygen to oxidize various substrates to produce brown-colored products) and then fired (to dry the tea leaves). Depending on the particular process used, particularly at the size reducing stage, different grades of tea are produced. Conventionally, the size reduction of the withered black leaf tea is performed by Googie. Googie is a machine which is like a revolving drum where the process of granulation occurs without much control on the outcome of the size/grades of the tea. This process forms granules of various sizes by default and then graded which is basically sifting the tea into different sizes. Black leaf tea with a larger particle size is considered a premium tea and commands a higher price than the smaller grades (Fannings and Dusts). All the above processes however give significant amounts of smaller grades of tea.
[0003] The standard output of percentile of grades formed after sifting by default are as follows:
Grade Category Mesh Size ( Tea Board Circular) % of Manufacture
BPS (Broken Pekoe Souchone) CTC BROKEN LEAF ABOVE MESH SIZE 10 2%
BOP (Broken Orange Pekoe) CTC BROKEN LEAF ABOVE MESH SIZE 12 10%
BOPSM (Broken Orange Pekoe Small) CTC BROKEN LEAF ABOVE MESH SIZE 14 20 %
BP (Broken Pekoe) CTC BROKEN LEAF ABOVE MESH SIZE 16 20%
OF/PF (Orange Fanning / Pekoe Fanning) CTC FANNING LEAF ABOVE MESH SIZE 28 18%
PD/Dust (Pekoe Dust/ Dust) CTC DUST ABOVE & BELOW 30 18%
Secondary (Fibrous Tea) ALL SIZES ALL THE ABOVE SIZES 12%

[0004] There are different price realizations for the different grades of teas depending on the demand. The existing methods fails to provide any means to control or increase the yield percentage according to the demand.
[0005] SU 526339 discloses a process of making tea which involves the steps of withering, rolling, grading, comminuting, treating with a sugar solution, drying to a moisture content of 35-50%, granulating and drying to give tea granules of about 5 mm diameter.
[0006] US20030113406 discloses a process to make tea with higher yields of a desired size comprising the steps of: (a) withering green leaf tea and optionally other materials; (b) size reduction; (c) fermentation; (d) extrusion of the size reduced or fermented tea leaf mass through holes in a perforated body; (e) cutting the extrudate; (e) drying. The desired size of the tea is preferably Broken Orange Pekoe (BOP), Broken Pekoe (BP) or Broken Orange Pekoe Souchung (BOPS).
[0007] Hence there is a felt need in the industry to be able to have a process in which tea grade changes could be done to realize maximum value.
[0008] The applicants have found that with the instant new process the outcome of the desired tea grades could be maximized up to 70-80 % and significantly minimizing the fines and dusts. By this process the bulk density of the product increases by 25 % and thus the tea is grainier which is desired a quality.

OBJECT OF THE INVENTION
[0009] The main objective of the present invention is to overcome the drawbacks of the prior art.
[0010] It is another objective of the present invention to provide a manufacturing method that provides a significant control over outcome of the grades of tea produced.
[0011] It is yet another objective of the present invention to produce the desired grade of tea as per manufacturer’s market requirement.
[0012] It is yet another objective of the present invention to provide CTC black leaf tea with better harder & grainier granules.

DESCRIPTION OF FIGURES
[0013] Figure 1 is a schematic showing the difference between the conventional process and the process of the present invention.

SUMMARY OF THE INVENTION
[0014] The present invention relates to a process to make a black leaf CTC tea product with higher yields of a desired larger particle size comprising the steps of: withering green leaf tea; reducing the size of the withered green leaf tea in CTC machine; extrusion of size reduced leaf tea; granulation in a spheronizer; fermentation; drying; and sorting to give the black tea product.
[0015] In an embodiment, for the purpose of the present invention the extrusion takes place in a co-rotating twin screw extruder at ambient temperature. The twin-screw extruder is provided with a dome shaped screen of mesh size in range from 1mm-4mm.
[0016] In an embodiment of the present invention, the extruded pellets from co-rotating twin screw extruder are in spheronizer for 2 min. to 3 min. The spheronizer operates from 100 rpm to 300 rpm. In the spheronizer the extrudate is shaped into a substantially spherical shape.
[0017] In another embodiment of the present invention, the fermentation step occurs after the extrusion and granulation step. The fermentation takes place for 90 minutes to 120 minutes at room temperature.
[0018] In a yet another embodiment of the present invention, a black leaf CTC tea product obtained from the process of the present invention gives 25% more denser tea granules.

DESCRIPTION OF THE INVENTION
[0019] The present invention relates to an improved process for the manufacturing of CTC black tea. The improved process of the present invention comprises the steps of: (a) withering green leaf tea and optionally other materials; (b) size reduction; (c) extrusion of the size reduced tea leaf mass through die holes of a twin screw extruder; (d) cutting the extrudate by spheronizer; (e) fermenting; (f) drying and (g) sorting.
[0020] As used herein “Tea” means leaf material from Camellia sinensis var. sinensis or Camellia sinensis var. assamica. “Tea” is also intended to include the product of blending two or more of any of these teas.
[0021] As used herein the term "fresh leaf” includes buds, leaves, or stem of the plant Camellia sinensis.
[0022] As used herein the term “Leaf tea” means a tea product that contains one or more tea origins in an un-infused form.
[0023] As used herein the term "black leaf tea" means a tea produced by promoting the aerobic oxidation of fresh leaf catechins in reactions catalysed by tea polyphenol oxidase.
[0024] As used herein the term "fermentation" is used to refer to aerobic oxidation of fresh leaf tea catechins in reactions catalysed by tea polyphenol oxidase.
[0025] As used herein the term "dust tea" means a black leaf tea having mean particle size in the range 0.1 -1 mm.
[0026] In the process of making black CTC tea a supply of plucked fresh tea leaves is withered. The leaves can be withered in any conventional manner, for example by storing them for a period of time, usually perhaps up to 16 to 24 hours, during which they undergo various biochemical and physical changes and typically lose moisture. Alternatively, withering is carried out by blowing air across a bed of green tea leaves. The leaves must be withered to have a specific leaf moisture content between 70 to 72% preferably greater than 68%. If moisture content is more than 72% too much heat is generated in the CTC machinery, especially at commercial throughputs. This controlled withering is important not only for flavour generation (as conventionally accepted) but also to ensure optimal CTC-like fermentation (where higher moisture content leads to improved oxidation of polyphenols, and to alter the physical properties of the leaf to optimise their interaction with the maceration equipment, and enable the necessary commercial throughputs.
[0027] The withered leaf is then subjected to a size reduction step (often referred as a maceration or comminution step) during which the withered green tea leaf is reduced in size. During size reduction, the cell wall is ruptured allowing the cell contents to react. Size reduction can be carried out by any of the methods known in the art including cut-tear-curl (CTC), rolling (as in the orthodox process), use of a rotorvane or use of a Lawrie tea processor etc. Preferably, the size reduction in the present invention is carried out by CTC method. CTC refers to the Crush, Tear & Curl process where the withered green leaves are passed in-between two rollers rotating in opposite directions. The CTC process of rolling is a comparatively rigorous one for the leaf, where leaf is forced through a machine having two steel cylinders. The cylinders move in inverse direction at a speed of 700 RPM and 70 RPM with marginal clearance between them. The leaf as it passes consecutively through a bank of three to four such machines gets much reduced in size and its cell get ruptured for accelerated as well as intensive fermentation. The whole process leaves the leaf granulated. It gives much better thicker liquor and yields more cups of tea per kg of leaf as compared to the Orthodox type of tea. CTC (crush, tear, curl) differs from orthodox production solely in that, after rolling and before cutting and fermentation, the tea is uniformly shredded with a CTC machine, so shortening the overall production time by approx. 50%. The other advantages of the CTC process over orthodox process are leaf distortion is much greater, fermentation is faster, teas have higher levels of theaflavins and thearubigins and therefore have more colour and are brighter and brisker than orthodox teas. There is complete maceration of the leaves and the resulting powdery material is referred to as “cut dhool”. Enzymatic action is higher in the CTC type of manufacture. The size reduction step can be followed by the fermentation step or by the extrusion and cutting step.
[0028] For the purpose of the present invention, the extrusion step can be suitably carried out after size reduction and before fermentation by using a co-rotating twin screw extruder. In preferred extruders used in the invention, the mass of material to be extruded is fed thorough the extruder by a screw feeder for positive displacement of the mass. The co-rotating twin screw extruder in the present invention is model Lab-20 with maximum speed of about 720 rpm and L/D 32-64. The twin screw extruder of the present invention is fitted with dome shaped screen for desired output of grade required. Dome shaped screen for the purpose of the present invention is a dome shaped mesh with holes of size 1mm-4 mm (as per desired output) which converts crushed tea leaf into pellets of a controlled size and shape ideally suited for spheronization. It aids in low pressure extrusion with negligible heat generation. The extrusion is carried out at ambient temperature. The throughput of the extruder is 5-20 kgs per hour. The manufactures may select the dome shaped screen depending upon the type of tea that needs to be produced. Table 1 represents different output grade depending upon the mesh size of the dome shaped screen of the co-rotating twin screw extruder.

[0029] Table 1
MESH SIZE OUTPUT GRADE
1mm PF
2mm BP
3mm BOP
4mm BOPL / BPS
[0030] The extruded mass in shape of pellets comprising the tea leaf material is then shaped to a suitable size by spheronizer. It is preferred that the cutting take place immediately after extrusion. A spheronizer is a device consisting of a vertical hollow cylinder with a horizontal rotating disk (friction plate) located inside. Extrudates are charged onto the rotating plate and broken into short segments by contact with friction plate, collisions between particles and collisions with the wall. Mechanical energy introduced by the spinning friction plate is transmitted into kinetic energy in the form of mechanically fluidized bed. Further processing will cause the extrudate to deform gradually into a spherical shape. The friction plate has a grooved surface to increase the frictional forces.
[0031] Spheronization is the process where extrudates (the output from an extruder) are shaped into small rounded or spherical granules. In practice the extrudates usually vary in size from 1 mm to about 4 mm. Spheronization provides an efficient method of producing uniform discrete granules of various sizes and of higher bulk density. The spheronization takes place at room temperature, and at 100 rpm to 300 rpm. The pellets from extruder are passed through spheronizer in batches of 100 to 150 grams for 2 to 3 minutes. Size of granules can be controlled, according to manufacturer needs. The spheronizer used in the present invention is Sunsai SPH 75.
[0032] The term fermentation when applied to tea is something of a misnomer, as the term actually refers to how much a tea is allowed to undergo enzymatic oxidation by allowing the freshly picked tea leaves to dry. This enzymatic oxidation process may be stopped by either pan frying or steaming the leaves before they are completely dried out. The fermentation is an oxidation and tanning process of the cell fluids, which have been released during the rolling. Fermentation is the oxidative process that tea undergoes when certain endogenous enzymes and substrates are brought together by mechanical disruption of the cells for example 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 benzotropolone 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. Fermentation is suitably carried out by contacting the leaf tea material with air or an oxygen enriched gaseous mixture. It is also possible to carry out size reduction, followed by partial fermentation, followed by further reduction and complete fermentation. For the fermentation, the leaves are spread out on tables in layers of 10 cm. The "tea maker" needs to constantly monitor the degree of oxidation, particularly with respect to the scent of the wet leaves. The quality of the finished tea is very much dependent on the correct fermentation.
[0033] As a final step, the fermented mixture is fired, dried and sorted to yield 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%, preferably 2.5-3%, and also leads to further chemical/biochemical oxidation and changes in tea aroma. Drying methods include tray drying, fluidized bed drying, vibratory fluidized bed drying etc. In a preferred aspect the tea leaf material is dried by vibratory fluidized bed drying. In vibratory fluidized bed drying the desirable inlet temperature ranges from 140° to 150°C. Firing at this temperature resulted in improved leaf appearance and better bloom. The exhaust temperature has to be maintained at 70 °C to 75 °C in the third section. In some driers, exhaust temperature is measured at the centre of the drying zone along the length, and kept at 55 °C-60°C. The tea is dried for approximately 10 minutes to 20 minutes which makes the cell fluid stick to the leaves and gives it its dark brown to black colour.
[0034] The dried leaf tea may be sorted into its various grades using any sorting and grading means known to those skilled in the art. The tea of required size prepared by the process of the invention is obtained in a higher yield. The process of the present invention helps in increasing the yield of desired grade by up to 70 to 80% and significantly minimizing the fines and dusts. The amount of secondary grade teas in the dried tea is significantly lower than that obtained by the conventional process. The process of the present invention also increases the bulk density of the product by 25 % and thus the tea is grainier, which is a desired quality.
[0035] Other optional materials can be added at any stage during the process of the invention. These include secondary teas, dust tea, enzymes, flavors, encapsulated flavors, other leaf/flower material like jasmine, mint and/or basil, starches, carbohydrates, etc. The optional materials may also be added to the teas or tea blends prepared by the process of the invention.
[0036] In order to further illustrate the working and effectiveness of the invention the following non-limiting example is given.
[0037] Example 1
[0038] Process of making black CTC tea
[0039] Green tea leaves are plucked (approximately 1-2 kgs) and is withered at ambient conditions. The withered leaf is then subjected to size reduction on the Cut-Tear-Curl (CTC) machine. The size reduced leaves are passed through extrusion process in a co-rotating twin screw extruder. The processing in twin screw extruder is at ambient temperature at around 720 rpm. The extruder is fitted with dome shaped screen of diameter 1 to 4 mm depending upon the requirement. The diameter of extruding pellets from extruder is 1 mm to 4 mm depending the mesh size of dome shaped screen. The extruded pellets passes through spheronizer in batches of 100 to 150 grams for 2 to 3 minutes. The spheronizer operates at an rpm of 250. The granules obtained from spheronizer are kept for fermentation for 90 minutes to 120 minutes at room temperature. The fermented material obtained is then fired in a drier at a temperature range from 55 °C to 150 °C. The material so obtained was sieved. It was observed that the yield of the desired tea grade is in range from 80 to 90% depending on the dome shaped screen used in twin screw extruder. The size of tea granules obtained is in range from 1mm to 4mm depending on the dome shaped screen used in twin screw extruder.
[0040] Example 2
[0041] Comparison of process of present invention with conventional process
[0042] The CTC black leaf tea obtained from Example 1 is compared with CTC black tea obtained from conventional process. The conventional process comprises the step of withering of plucked green leaves, size reduction in CTC machine (maceration), granulating in googie machine, fermentation, drying followed by sorting.
[0043] Table 3 illustrates the effectiveness of the process of the present invention in increasing the yield of desired tea grades and in producing more dense granules.

[0044] Table 3
Present Invention (Extrusion and Spheronization) Conventional Process
Yield of tea granule 80-90 % 10-20%
Volume of tea granule 150-180 cc (for 100 grams) 200-270 cc (for 100 grams)

[0045] Example 3 Sensory evaluation
[0046] The CTC black tea obtained from Example 1 is evaluated for visual appearance.
[0047] Sensory protocol: The visual evaluation was carried out by group of 10 panellists. The panellists assessed samples of tea granules obtained from the present invention and conventional process. In all cases, the panellists were instructed to evaluate the samples on the following attributes: colour of granules, evenness in size of granule and make of granules. The panellists gave their scores on 5 point scale. The observations of panellists are shown in Table 4.
[0048] Table 4 Sensory evaluation
Attributes Sample from present process Sample from old (conventional) process
Score SD ± Score SD ±
Colour of granules 4.5 0.5 4.0 0.5
Evenness in size 4.5 0.5 3.5 0.5
Make of granules 4.5 0.5 3.5 0.5
Overall liking 4.5 0.5 3.5 0.5
*Scores (average) on 5 point scale; 1- Worst, 2 – Bad, 3-Okay, 4-Good, 5-Best
**SD± : Standard Deviation shown by various panellists (on the same parameter and same sample)

[0049] In the specification, there have been disclosed typical preferred embodiments of the invention. Although specific terms are employed, they are used in generic and descriptive sense only and not for purposes of limitation. The scope of the invention is set forth in the claims. Obviously many modifications and variations of the invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practices than as specifically described.