slide 1

Back to the List of the Granted Patents                                                                        Click here to download KE000442 PDF

(21) Application Number: KElP/ 2009/ 000889
       
(22) Filing Date: 14/09/2007
       
(30) Priority data: 06121924.2  06/10/2006  EP
       
(86) PCT data PCTIEP07/05970914/09/2007 wo 2008/040627 10/04/2008

(73) Owner: Unilever PLC of Unilever House, Blackfriars, London,  Greator London, EC4P 4BQ, United Kingdom

(72) Inventor: THIRU, Ambalavanar ofUnilever R & D Colworth, Sharnbrook, Bedford MK44 1LQ, United Kingdom; COLLIVER, Stephen, Peter of Unilever R & D Colworth, Sharnbrook, Bedford Bedfordshire MK44  1LQ, United Kingdom and Peter, Kiprotich ofUnilever Tea Kenya Limited, P.O. Box 20, Kericho, 20200, Kenya.

(74) Agent/address for correspondence: & Stratton Advocates, P.O. Box 40111- 00100, Nairobi

(54)    Title: A LEAF PRODUCT AND A PROCESS FOR THE MANUFACTURE THEREOF.

(57) Abstract: A palatable green leaf tea from Camellia sinensis var. assamica is disclosed. Infusion of 2 g of the leaf tea in 200 ml water for 1.5 minutes at 90 degrees centigrade produces a beverage comprising catechins in an amount of between 0.01 and 0.1% by weight of the beverage. Also disclosed is a process for manufacturing the leaf tea product wherein fresh leaf from var. assamica is macerated using a combination of rotorvane and double-cone processor.

A  GREEN  LEAF  TEA  PRODUcr  AND  A  PROCESS  FOR  THE  MANUFACTURE

THEREOF

Technical  Field of  the  Invention

5    The  present  invention  relates  to  green  leaf  tea.

Backaround of  the  Invention

Green tea is a popular beverage which has been consumed in China and Japan for many hundreds of years. Recently, extensive

10    laboratory research and epidemiologic studies have shown that compounds present in green tea (particularly the flavanols such as catechins) may reduce the risk of a variety of illnesses. These studies, along with the increasing complexity of the consumer's palate have led to increased consumption of green tea,

15    even in markets (such as the USA and Western Europe) where there is no tradition of green tea consumption.

There are two varieties of the tea plant Camellia sinensis, namely var. sinensis and var. ass arnica. The variety Camellia

20    sinensis var. assamica typically has the highest catechin content and is also relatively rich in certain non-flavanol actives, such as the amino acid theanine.


The    flavanols   have   a   large   influence   on   the   bitterness   and

25    astringency of tea infusions. Thus, owing to the high flavanol content of var. assamica, infusions of green tea from this variety are found to be unpalatably bitter. Consequently, var. assamica is considered unsuitable for use in green tea production (see, for example, "Tea: Cultivation to Consumption", K.C.

30    Willson and M.N. Clifford (Eds), lst Edn, 1992, Chapman & Hall (London), Chapter 13, p. 414).

we have recognised that there is a need to provide a green leaf tea that has the enhanced levels of actives typical of var. assamica but which produces a beverage having the palatability of traditional green tea beverages prepared from var. sinensis. We

5    have found that such a need may be met by controlling the amount of catechins delivered by the green leaf tea.

summarv of  the  Drawinqs

Figure 1 shows an elevation of the rotor of a double-cone 10 processor.



Figure 2 shows a vertical section of the barrel of a double-cone processor.



15    Tests  and Definitions

TEA

"Tea" for the purposes of the present invention means material from Camellia sinensis var. sinensis and/ or Camellia sinensis var. assamica.

20

"Leaf tea" for the purposes of this invention means a tea product that contains tea leaves and/or stem in an uninfused form, and that has been dried to a moisture content of less than 30% by weight, and usually has a water content in the range 1 to 10% by

25    weight (i.e. "made tea"). "Green leaf tea" refers to substantially unfermented leaf tea. "Fermentation" refers to the oxidative and hydrolytic process that tea undergoes when certain endogenous enzymes and substrates are brought together, e.g., by

mechanical  disruption  of  the  cells  by  maceration  of  the  leaves.

30    During this process colourless catechins in the leaves are converted to a complex mixture of yellow and orange to dark-brown polyphenolic substances.
"Fresh tea leaves" refers to tea leaves and/or stern that have never been dried to a water content of less than 30% by weight, and usually have a water content in the range 35 to 90%.

5    BEVERAGE

As used herein the tem "beverage" refers to a substantially aqueous drinkable composition suitable for human consumption.

PRODUCTION  OF  A BEVERAGE  BY  INFUSION  OF  2  g  LEAF  TEA  IN  200  ml

10    WATER  AT  90°C  FOR  1.5  MINUTES

For  the  purposes  of  this  invention,   the  ability  of  leaf  tea  to

deliver actives such as catechins, caffeine and/or theanine, as well as the ability of the leaf tea to deliver beverages with good colour and/or clarity is detemined using the following

15    standard  infusion  conditions:

1.    The leaf tea is removed from any package and 2 g is placed in a 500 ml container.

2.    1  litre  of  deionised  water  is  then  brought  to  boiling  and  200

20    g  immediately  added  to  the  500  ml  container.

3.    The container is stored at an air temperature of 20°C and the leaf tea is allowed to statically infuse in the water.

4.    After 1. 5 minutes, the infusion is stirred for 5 s by hand using a spoon and the leaf tea is then immediately removed from

25    the infusion by straining the contents of the container through muslin.

CATECHINS

As  used  herein  the  tem  "catechins"  is  used  as  a  generic  term  for

30    catechin, gallocatechin, catechin gallate, gallocatechin gallate, epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, and mixtures thereof.

DETERMINATION  OF  CATECHINS  AND  CAFFEINE  IN  LEAF  TEA

The amounts of catechins and caffeine in leaf tea are determined simultaneously by reverse-phase HPLC as follows:

5    Sanple  Preparation

1.  Grind  leaf  tea  using  a  Cyclotech~ 1093  sample  mill  (FOSS  Ltd,

Warrington, Cheshire, UK) fitted with a 1.0 J.lm screen, until a fine powder is achieved.

2.    Weigh  accurately  approximately  200  mg  of  the  ground  leaf  tea

10    into  an  extraction  tube,  and  record  the  mass.

3.   Warm  at   least  20  ml   of  a  methanol-water  solution   (70%  v/v

methanol  in  distilled  water)  to  70°C.

4. Add 5 ml of the hot methanol-water solution to the extraction tube. Gently mix the methanol-water and leaf tea on a vortex

15    mixer; place in a water bath at 70"C for 5 minutes; mix again and then place in a water bath at 70°C for a further 5 minutes.

5. Gently mix the methanol-water and leaf tea on a vortex mixer again and then allow to cool for 10 minutes at an air temperature

of  20°C.

20    6. Centrifuge the extraction tube at a relative centrifugal force (RCF) of 2900 g for 10 minutes.

7. The  extraction  tube  should  now  contain  a  liquid  supernatant

on top of a plug of tea material. Carefully decant supernatant into a clean graduated test tube.

25    8. Add 5 ml of the hot methanol-water solution to the plug in the extraction tube. Gently mix the methanol-water and tea material on a vortex mixer; place in a water bath at 70°C for 5 minutes; mix again and then place in a water bath at 70°C for a further 5 minutes.

30    9. Gently mix the methanol-water and tea material on a vortex mixer again and then allow to cool for 10 minutes at an air temperature of 20°C.
 
10. Centrifuge the extraction tube at a RCF of 2900 g for 10 minutes.

11. The extraction tube should now contain a liquid supernatant on top of a plug of tea material. Carefully decant supernatant

5    into  the  graduated  test  tube  containing  the  supernatant  from  step

7.   

12.    Make up the pooled supernatants to 10 ml with the methanol-water solution.

13.    Add   1   ml   of   a   solution   of   2.5   mg/ml   EDTA   and   2.5   mg/ml

10    ascorbic  acid  in  distilled  water  to  the  graduated  test  tube.

14.  Dilute  1  part  of  the  pooled  supernatant  mixture  with  4  parts

(by volume) of 10% acetonitrile stabiliser solution (10% v/v acetonitrile, 0.25 mg/ml ascorbic acid and 0.25 mg/ml EDTA in distilled water).

15 15. Decant the diluted pooled supernatant mixture into microcentrifuge tubes and centrifuge in a bench top centrifuge at a RCF of 14000 g for 10 minutes.


HPLC  Analysis  conditions

2 0    Column:    Luna  Phenyl  hexyl  5j.J.,  250  x  4. 60  =

Flow  rate:    1  ml/min

Oven  temperature:    3o•c

Solvents:    A:  2%  acetic  acid  in  acetonitrile

25    B:  2%  acetic  acid  and  0.02  mg/ml  EDTA  in  water


Injection volume:  10  IJ.l
 
Gradient:                               
Time            % Solvent  A    % Solvent B    Step
                                   
0  to    10  min    5        95            Isocratic
10    to    40    min    5    18    95    -  85    Linear  gradient
540    to    50    min    18        82            I socratic
50    to    55  min    50        50            Wash
55    to    75    min    5        95            I socratic

Quantification:    Peak   area   relative   to   a   calibration   curve

10    constructed daily. Calibration curve is constructed from caffeine and the concentration of catechins is calculated using the relative response factors of the individual catechins to caffeine (from the ISO catechin method - ISO/CD 14502-2) . Individual

caffeine standards (Sigma, Poole, Dorset, UK) are used as peak 15 identification markers.

DETERMINATION  OF  CATECHINS  AND  CAFFEINE  IN A BEVERAGE

The amounts of catechins and caffeine in a beverage are determined simultaneously by reverse-phase HPLC as follows:

20

sample  Preparation

1. 9 ml of the freshly-brewed beverage are taken and 1.12 ml of acetonitrile added, along with 1.12 ml of a solution of 2.5 mg/ml EDTA and 2.5 mg/ml ascorbic acid in distilled water.

25    2. The resulting solution is then decanted into microcentrifuge tubes and centrifuged at a RCF of 14000 g for 10 minutes.

HPLC  Analysis  conditions

The  HPLC  analysis  conditions  are  identical  to  those  given  above

30    for  the  leaf  tea.

DETERMINATION  OF  THEANINE  IN  A BEVERAGE

The amount of theanine in a beverage is determined by reversed phase HPLC chromatography using fluorimetric detection following post-column derivatisation with o-pthalaldehyde.

5

Sample  Preparation

The freshly-brewed beverage is diluted with de-ionised water (25°C) in a weight ratio of beverage:water of 1:10.

10    HPLC  Analysis  conditions

Column:    Hypersil  HyPURITY  Elitem  C18,  5~, 150mm x  4.6cm
Flow    rate:        1  ml/min
Oven    temperature:    35"c

15    Solvents:   A:  5 mM  pentadecafluorooctanoic  acid  in  water

B:    5 mM  pentadecafluorooctanoic  acid  in  acetonitrile

Gradient:           
Time    (min)    % Solvent  A    % Solvent  B
20    0    85        15
    8    85    15
    10    80    20
    11    10    90
    14    10    90
25    15    85    15
    31    85    15

Quantification: The eluant from the column is fed into a low dead-volume 3-way junction and mixed with the o-Pthalaldehyde

30    reagent in a 1:1 ratio, the o-Pthalaldehyde reagent being pumped at 1 ml/minute by the isocratic pump. (The o-Pthalaldehyde reagent is 1.0 g/1 o-Pthalaldehyde, 5 ml/1 methanol, 2 ml/1 Brij 35 and 3 ml/1 2-mercaptoethanol in pH 10 borate buffer.)

Fluorescence detection is: Excitation = 340 nm and Emission = 425 nm. Peak area relative to a calibration curve constructed daily is used for quantification. The calibration curve is constructed from dilutions of a standard solution of SuntheanineTM (Taiyo

5    KK).

DETERMINATION  OF  HAZE  OF  A BEVERAGE

The  haze  of   a  beverage  is  measured  at  25°C.   Directly  following infusion,   the  freshly-brewed  beverage  is  allowed  to  cool  to  25°C 10     and   then   immediately  analysed  using   a   Hach   2100P   turbidimeter (Hach    Lange    Ltd,    Salford,    UK).    The    2100P    is    a    portable turbidimeter  with   a   tungsten  filament   lamp  as   an  optical   light source.   Sample  volume  is   15  ml.  The   cell  path  length  is   2   em.

Haze  is  reported  as  NTU  (Nephelometric  Turbidity  Units).

15

DETERMINATION  OF  COLOUR  OF  A BEVERAGE

The colour of a beverage is measured at 25°C. Directly following infusion, the freshly-brewed beverage is allowed to cool to 25°C and then immediately analysed using a Minolta CT-310

20    transmittance color meter. The colorspace used is CIELab, the illuminant is C, and the cell path length is 10 mm. The meter is zeroed on distilled water and calibrated using a Yellow 101 filter (available from Lee Filters, Andover, UK) having: L* =

91.    44, a* = -15.92, b* = 102.38, C* = 103.61 and h* = 98.84; 25 wherein L* is light-dark, a* is red-green, b* is yellow-blue, C*
is  chroma  and  h*  is  hue.

PARTICLE  SIZE

For    the   purposes   of   the   present   invention,   particle   size   is

30    characterised  by  sieve  mesh  size  using  the  following  convention:


•    Tyler  mesh  sizes  are  used  throughout.


•    A "+" before the sieve mesh indicates the particles are retained by the sieve.

•    A "-" before the sieve mesh indicates the particles pass through the sieve.

5

For example, if the particle size is described as -5 +20 mesh, then the particles will pass through a 5 mesh sieve (particles smaller than 4.0 rnrn) and be retained by a 20 mesh sieve (particles larger than 841 ~).

10

ROTORVANE

A rotorvane is a type of tea leaf conditioner, conventionally used to wound tea leaves prior to processing with a CTC (crush, tear and curl) machine during black tea manufacture. Rotorvanes

15    are widely used in the tea industry and are described, for example, in "Tea: Cultivation to Consumption", K.C. Willson and M.N. Clifford (Eds), 1st Edn, 1992, Chapman & Hall (London), Chapter 14, especially pp. 486-487. Suppliers of rotorvanes

include  Vkrarn  India  Ltd   (Kolkata,   India)   and  Plarnac  (India)   Pvt

20    Ltd  (Kolkata,  India).

DOUBLE-CONE  PROCESSOR

A double-cone  processor  is  a  type  of  continuous  tea  leaf  rolling

machine.    Double-cone  processors  are  available,   for  example,   from

25    Plarnac  (India)  Pvt  Ltd  (Kolkata,  India).

The double-cone processor is similar to the tea processing machine disclosed in UK patent GB 1 175 559 (Peter John Parr),

except  that  the  barrel  and  rotor  shaft  are  modified  as  shown  in

30    Figures 1 and 2, respectively. Specifically, the double-cone processor comprises a stationary barrel (10) having three sets of resistors (11) projecting from the inner wall of the barrel (10), an opening (12) near one end (feed end) of the barrel (10) to

feed fresh tea leaves to be macerated, and a rotor shaft (1) adapted to advance the tea leaves from the feed end to the other end (discharge end) of the barrel (10) by axial rotation therein and simultaneously macerate the leaves. The rotor (1) comprises a

5    helical feed worm (2) for part of its length near the feed end of the barrel (10), a first frusto-conical member (3) extending from the feed worm (2) and extending towards the discharge end of the barrel, and a second frusto-conical member (4) extending from the

first    frusta-conical   member   (3)   to   the   discharge   end   of   the

10    barrel (10). The first frusto-conical member (3) has three sets of vanes (3A) radially projecting thereform, the vanes (3A) being staggered in relation to the resistors (11) of the barrel wall. The second frusta-conical member (4) has its inclined surface

fluted  with  flutes   (4A)  helically  disposed.  The  discharge  end  of

15    barrel (10) is fitted with a pressure sleeve (13) similar to the sleeve disclosed in GB 1 175 559, the sleeve having a plurality of studs (13A) projecting from its inner surface.


Summary of  the  Invention

20    In a first aspect, the present invention provides a green leaf tea from Camellia sinensis var. assamica, wherein infusion of 2 g of the leaf tea in 200 ml water for 1.5 minutes at 90°C produces a beverage comprising catechins in an amount of between 0.01 and 0.1% by weight of the beverage.

25

We have found that such a leaf tea can be used to prepare beverages at least as palatable as green tea beverages prepared from var. sinensis.


30    We have also found that a particularly convenient method of producing green leaf tea from Camellia sinensis var. assamica, which has the desired infusion properties, is by macerating fresh

leaf with the combination of a rotorvane and a double-cone processor.



Thus in a further aspect, the present invention provides a process for manufacturing a green leaf tea comprising the steps of:

(a)    providing fresh tea leaves from the plant Camellia sinensis var. assamica; then

(b)    heat-treating the fresh leaves to arrest enzyme action; then

(c)    macerating the fresh leaves with a rotorvane and a double-cone processor, preferably by passing the fresh

leaves through the rotorvane to produce partially macerated leaves and then passing the partially macerated leaves through the double-cone processor to produce the macerated leaves; then

(d)    drying  the  macerated  leaves;  and  then

(e)    optionally sorting the dried macerated leaves according to particle size.



The present invention also provides green leaf tea obtained and/or obtainable by the process of the invention.


In  a  further  aspect  still,  the  present  invention  relates  to  a  new
 

25    leaf tea having enhanced levels of actives and/or good colour and clarity but having catechin levels typical of traditional green

tea. Thus, the invention provides a green leaf tea from Camellia sinensis var. assamica and/or sinensis wherein infusion of 2 g of the leaf tea in 200 ml water for 1.5 minutes at 90°C produces a

3 0 beverage comprising catechins in an amount of between 0. 01 and 0.1% by weight of the beverage, more preferably between 0.04 and

1.    09% by weight of the beverage, most preferably from 0. 06 to 0.085%.; and wherein the beverage additionally:

-    comprises theanine in an amount of at least 0. 004% by weight of the beverage, preferably from 0.005 to 0.02%,

5    and/or

-    has a haze of less than 20 NTU, preferably from 1 to 15 NTU, and/or


-    has a hue (h*) of between 103 and 115, preferably between 104 and 110, and/or

10    - has a chroma (C*) of between 6 and 15, preferably between B and 10, and/or

- has a lightness (L*) of between 94 and 100, preferably between 96 and 99.



15    Detai1ed  Description

GREEN  LEAF  TEA

We  have  found  that  green  leaf  tea  from  Camellia  sinensis  var.

assamica  can  be  used  to  produce  palatable  green  tea  beverages.  We have  found  that  if  the  infusion  characteristics  of  the  leaf  tea 2 0    are  controlled  such  that  when  2  g  of  the  leaf  tea  is  infused  in 200   m1   water   for   1. 5  minutes   at   90°C   a   beverage   is   produced comprising  catechins  in  an  amount  of  less  than  0.1%  by  weight  of the   beverage,   then   the   leaf   tea   is   suitable   for   preparing palatable   beverages.   The   bitterness   of   the   beverages   can   be

25    further reduced by decreasing the amount of catechins delivered by the leaf tea such that when 2 g of the leaf tea is infused in 200 m1 water for 1.5 minutes at 90°C a beverage is produced comprising catechins in an amount of less than 0.09% by weight of the beverage, more preferably less than 0.085%.


The leaf tea of the present invention, however, still comprises significant amounts of catechins in order to provide taste and/or health benefits associated with green tea. Thus the infusion characteristics of the leaf tea are controlled such that when 2 g

5    of the leaf tea is infused in 200 ml water for 1.5 minutes at 90°C a beverage is produced comprising catechins in an amount of at least 0.01% by weight of the beverage. In fact, we have found that the amount of catechins delivered by the leaf tea may be as

high  or  even  higher  than  even  the  most  high  quality  conventional

10 teas from Camellia sinensis var. sinensis without becoming unpalatable. Thus the infusion characteristics of the leaf tea are preferably controlled such that when 2 g of the leaf tea is infused in 200 ml water for 1.5 minutes at 90°C a beverage is produced comprising catechins in an amount of at least 0. 04% by

15 weight of the beverage, more preferably at least 0. 05% and most preferably at least 0.06%.



Despite the relatively low levels of catechins delivered by the green leaf tea, we have found that the levels of certain other

20    actives (such as theanine and caffeine) may be delivered at relatively high levels compared with conventional leaf teas. Thus it is preferred that the green leaf tea delivers theanine such that infusion of 2 g of the leaf tea in 200 ml water for 1.5 minutes at 90°C results in a beverage comprising theanine in an

25    amount of at least 0. 004% by weight of the beverage, more preferably from 0.005 to 0.02%, and most preferably from 0.006 to 0.01%.


Alternatively  or  additionally,   the   infusion  characteristics   of

30    the leaf tea are such that when 2 g of the leaf tea is infused in 200 ml water for 1.5 minutes at 90°C a beverage is produced comprising caffeine in an amount of at least 0.008% by weight of

the beverage, more preferably at least 0.01% and most preferably from 0.012 to 0.03%.



The  infusion  characteristics  of  the  green  leaf  tea  are  preferably

5    such that the green leaf tea produces a beverage with high clarity and good colour. In particular it is preferred that the beverage produced by infusion of 2 g of the leaf tea in 200 ml

water for 1.5 minutes at 90°C has a haze of less than 20 NTU, more preferably less than 15 NTU and most preferably from 1 to 10

10    NTU. Alternatively or additionally, the beverage produced by infusion of 2 g of the leaf tea in 200 ml water for 1.5 minutes at 90°C has a hue (h*) of between 103 and 115, more preferably between 104 and 110; a chroma (C*) of between 6 and 15, more

preferably  between  8  and  10;   and/or  a  lightness   (L*)   of  between

15    94  and  100,  more  preferably between  96  and  99.


The infusion characteristics of the leaf tea may be provided in a number of ways including, controlling the particle size of the leaf tea, controlling the catechin content of the leaf tea,

20    and/or controlling the degree of damage to the leaf during processing.



In general, the larger the particle size of the leaf tea, the less efficient is the catechin delivery. Thus it is preferred

25    that at least 90% by weight of the leaf tea has a particle size above 30 mesh (595 J.Un), more preferably above 25 mesh (707 J.lm) and most preferably above 20 mesh (841 J.Un) • If the particle size

is too large, however, the tea may infuse too slowly and/or become difficult to portion and handle. Thus it is preferred that

30    at least 90% by weight of the leaf tea has a particle size below 3 mesh (5.66 mm), more preferably below 4 mesh (4.76 mm) and most preferably below 5 mesh (4.00 mm).

Although the infusion characteristics of the leaf tea may be manipulated by controlling the catechin content of the leaf tea, the processes required to achieve this (e.g. partially fermenting

5    or extracting the leaf) would necessarily alter the taste and/or non-flavanol actives provided by the leaf tea. Accordingly it is

preferred that the leaf tea retains the high catechin level typical of var. assamica. Thus it is preferred that the catechin content of the green leaf tea is at least 11% by dry weight of

10    the leaf tea, more preferably at least 12% and most preferably from 13 to 20%.



The most preferred method of providing the specified infusion characteristics of the leaf tea is by controlling the degree of

15    damage to the leaf during processing, for example by employing the process of the invention.



THE  PROCESS

The  process  of  the  invention  comprises  the  steps  of:

20    (a) providing fresh tea leaves from the plant Camellia sinensis var. assamica; then


(b)    heat-treating the fresh leaves to arrest enzyme action; then


(c)    macerating   the   fresh   leaves   with   a   rotorvane   and   a

25 double-cone processor, preferably by passing the fresh leaves through the rotorvane to produce partially macerated leaves and then passing the partially macerated leaves through the double-cone processor to produce the macerated leaves; then



30    (d)   drying  the  macerated  leaves;  and  then

(e)    optionally sorting the dried macerated leaves according to particle size.



Providing  fresh  leaves

5    In its simplest form, the fresh tea leaves are provided in freshly plucked form, i.e. without any further processing, and have a moisture content of 76 to 80% by weight. The fresh tea

leaves preferably comprise leaf and stem material. Most preferably the fresh tea leaves comprise actively growing buds,

10    e.g. in the form of the first two or three leaves together with the unopened bud (so-called "two-and-a-bud" and/or "three-and-a-bud" material) .



Heat-treatment

15    The heat-treatment of the fresh leaves arrests the enzyme action in the fresh leaves. The heat treatment should be such as to inactivate those endogenous enzymes responsible for fermentation and thus should be sufficient to substantially prevent fermentation during or after maceration (step (c)). Suitable

20    heat-treatnie.nts are well-known to those skilled in the art and include steaming and/or pan-firing (see, for example, "Tea:

cultivation to Consumption", K.C. Willson and M.N. Clifford (Eds), 1st Edn, 1992, Chapman & Hall (London), Chapter 13) . steaming is the preferred mode of heat-treatment as this avoids

25    scorching of the leaf surface which is sometimes encountered in contact-heating such as pan-firing. Scorching of the leaf surface can result in poor infusion characteristics of the made tea,

particularly    in   respect   of   the   colour   and   clarity   of   the

resulting  beverage.

30

We have found that controlling the moisture content of the fresh leaves prior to heat-treatment allows for convenient handling of the leaf in down-stream processing. In particular, it is preferred that the moisture content of the leaves is controlled

5    to be in the range of 74 to 76% by weight. Suitably, this moisture content is achieved by partially drying the leaves.


Maceration

Maceration  serves  two  functions.   Firstly  it  damages  the  leaves

1    0 such that their contents are more or less accessible to water used to make a beverage. Secondly it changes the shape and size

of  the  leaves.


Traditionally,  green  tea  is  macerated  using batch  equipment  known

15    as rollers (see, for example, "Tea: CUltivation to Conslliiption", K.C. Willson and M.N. Clifford (Eds), l 5 t Edn, 1992, Chapman & Hall (London), Chapter 13) or by rolling by hand. Green teas are

also known that are macerated using continuous equipment such as CTC machines. We have found that these known processes have the

20    disadvantage of being unsuitable for continuous manufacture or resulting in too much leaf damage to provide the desirable infusion characteristics of the made tea.



We  have  surprisingly  found  that  maceration  using  a  combination  of

25    rotorvane and double-cone processor provides the required amount of leaf damage to produce assamica green leaf tea that allows for

the provision of palatable green tea beverages. In particular the leaf damage is such as to provide leaf tea that delivers the taste and actives of green tea, whilst not being too severe so as

30    to provide the leaf tea with so high an efficiency of catechin delivery that beverages produced therefrom are unpalatably

bitter. Furthermore, the resulting green leaf tea is found to have a "twisted" appearance similar to that of high quality hand-rolled teas.



5    The preferred arrangement is one wherein the leaves are first passed through the rotorvane and then passed through the double-

cone processor. Thus in a preferred embodiment, following heat-treatment, the fresh leaves are passed through the rotorvane to produce partially macerated leaves and then the partially

10    macerated leaves are passed through the double-cone processor to produce the macerated leaves.


The maceration is particularly effective if the maceration is performed on fresh leaves having not too high a moisture content.

15    Thus it is preferred that the fresh leaves are partially dried to a moisture content of from 65 to 70% by weight prior to maceration.



Maceration    is  also  most  effective  if  the   leaves  are  at  a   low

20    temperature. Thus it is preferred that the fresh leaves are cooled to a temperature of from 5 to 40°C prior to maceration.


Drying

Following  maceration  the  leaves  are  dried.  To  allow  for  long-term

25    storage stability, it is preferred that the leaves are dried to a moisture content of less than 30%, more preferably from 1 to 10% by weight of the leaves.



Suitable drying processes are known in the art and include tray 30 drying. However, in a most preferred embodiment the drying step

comprises drying the macerated leaves in a fluid bed dryer as this allows for more uniform heating and prevents the evolution of off-flavours and aromas due to burning. Drying with a fluid bed dryer also avoids scorching of the leaf surface. Scorching

5    can result in poor infusion characteristics of the made tea, particularly in respect of the colour and clarity of the resulting beverage.



Sorting

10    The dried macerated leaves are preferably sorted according to particle size. In particular it is preferred that the leaves are sorted to recover those particles with a size larger than 30 mesh

(595 Jl.ffi), more preferably above 25 mesh (707 Jl.ID) and most preferably above 20 mesh (841 Jl.ffi). Sorting may also involve

15    recovering those particles with a particle size below 3 mesh (5. 66 mm) , more preferably below 4 mesh ( 4. 7 6 rnm) and most

preferably below 5 mesh (4.00 mm). Suitably the step of sorting the leaves comprises sieving the dried macerated leaves.


20    Exaiiiples

The present invention will be further described with reference to the following examples.

EXAMPLE  1

25    Fresh tea leaf (two leaves and a bud) from Camellia sinensis var. assamica was harvested from fields in Kenya. The fresh leaf has a moisture content of 76-80% by weight. The fresh leaf was then air-dried to a leaf moisture content of 75 (±1)%. The leaf was

then steamed for 60 seconds at a temperature of 96°C to 30 inactivate any endogenous enzymes and thus prevent fermentation.

The moisture content of the steamed leaves was then reduced to 67 (±1)% by passing the leaf through two hot air drum driers in series followed by a vibratory bed hot air drier.


5    Leaf at the end of the vibratory bed was cooled to room temperature (-25°C) and then fed to a rotorvane operating at 1500 kg I hour and with the iris opening set at 5.0 em. Macerated leaf from the rotorvane was then split into two portions and each portion fed through a double-cone processor operating at 750 kg I

10    hour. After the double-cone processing, the macerated leaf was dried in a fluid bed drier to a moisture content of below 3%.

Fibres    and  the  secondaries  were  then  removed  from  the  tea  leaf

and  the  leaf  sieved.  The  resulting  sorted  green  leaf  tea  (sample

15    A) had a size range of -5 +20 mesh and a content of catechins of 13.4% by weight.



The properties of the leaf tea were compared with a second leaf tea (sample B) prepared in an identical manner except that the

20    macerated leaf from the rotorvane was passed through two CTC machines instead of the double-cone processor. The properties were also compared with those of a high quality commercial green leaf tea (sample C). The results are shown in Table 1.


25                    TABLE  1               
                                       
    Sanpl.e    Variety        Catechins  (wt  %)  in            Properties  of  Beverage*   
                    Beverage*               
                                   
    A    Assamica            0.072        Pleasant  taste,  clear  liquor
                                       
    B    Assamica        0.123        Bitter  taste,  hazy  liquor
                                   
    c    Sinensis        0.055            Pleasant  taste,  clear  liquor
                                       
* Made  by 1nfus1ng 2 g of  sample  1n 200  ml  water  for  2 m1ns  at  90°C.

EXAMPLE  2

A green leaf tea (sample D) was prepared from var. assamica using the method given for sample A detailed in Example 1. The properties of this leaf tea were compared with those of a

5    commercial Japanese green tea (sample E). The results are shown in Tables 2 and 3.



TABLE  2

Sample    Variety    catechi.ns  (wt  %)    Ccmpositi.on  of   Beverage*  (wt%}

                            i.n    I.eaf               
                                                   
                                                   
                                    catechi.ns    Caffeine        Theani.ne   
                                                   
    D            Assamica    14.4        0.078    0.017        0.0088   
                                           
    E            Sinensis    11.4    0.077    0.017        0.0032   

* Made  by  lnfuslng  2  g  of  sample  ln  200  ml  water  for  1.5  ffilns  at  90°C.

10

                    TABLE    3   
                   
                   
Saupl.e    Variety    Col.our of  Beverage*    Baze  of  Beverage
                            (NTU}
                           
        L*    a*    b*    C*    h*
D    Assamica    97.29   -2.43   8.84 9.16 105.3 8.94

E    Sinensis    90.89   -4.07   18.48   18.92   102.3 52.6

*    Made  by  infuslllg  2  g  of  sample  ln  200  ml  water  for  1.5  mins  at  90°C.

1.    A green leaf tea from Camellia sinensis var. assamica, wherein infusion of 2 g of the leaf tea in 200 ml water for 1.5 minutes at 90°C produces a beverage comprising catechins

5    in an amount of between 0. 01 and 0.1% by weight of the beverage.



2. A green leaf tea according to claim 1 wherein at least 90% by weight of the green leaf tea has a particle size above 30

10    mesh.

3. A green leaf tea according to claim 1 or claim 2 wherein at least 90% by weight of the green leaf tea has a particle size below 3 mesh.

15

4.    A green leaf tea according to any one of the preceding claims wherein at least 90% by weight of the green leaf tea has a particle size of -5 +20 mesh.


20    5. A green leaf tea according to any one of the preceding claims wherein the catechin content of the green leaf tea is at least 11% by dry weight.


6.    A  green   leaf   tea   according   to   any   one   of   the   preceding 25           claims,  wherein  the  beverage  produced  by  infusion  of  2  g  of the   leaf   tea   in   200   ml   water   for   1.5   minutes   at   90°C comprises  catechins  in  an  amount  of  between  0. 04  and  0. 0 9%

by  weight  of  the  beverage,  preferably  from  0.06  to  0.085%.

3 o 7. A green leaf tea according to any one of the preceding claims, wherein the beverage produced by infusion of 2 g of the leaf tea in 200 ml water for 1.5 minutes at 90°C


comprises theanine in an amount of at least 0.004% by weight of the beverage, preferably from 0.005 to 0.02%.

8.    A  green   leaf   tea   according   to   any   one   of   the  preceding 5           claims,  wherein  the  beverage  produced  by  infusion  of  2  g  of the  leaf  tea  in  200  ml  water  for  1. 5  minutes  at  90°C  has  a
haze  of  less  than  20  NTU,  preferably  from  1  to  15  NTO.

9.    A   green   leaf   tea   according   to   any   one   of   the   preceding 10           claims,  wherein  the  beverage  produced  by  infusion  of  2  g  of the  leaf  tea  in  200  rnl  water  for  1. 5  minutes  at  90°C  has  a hue   (h*)   of  between  103  and  115,  preferably  between  104  and

110.

15    10. A green leaf tea according to any one of the preceding claims, wherein the beverage produced by infusion of 2 g of the leaf tea in 200 ml water for 1. 5 minutes at 90°C has a chroma (C*) of between 6 and 15, preferably between 8 and

10.

20

11.    A green leaf tea according to any one of the preceding claims, wherein the beverage produced by infusion of 2 g of the leaf tea in 200 rnl water for 1. 5 minutes at 90°C has a lightness (L*) of between 94 and 100, preferably between 96

25    and  99.

12.    A green leaf tea according to any one of the preceding claims obtainable by a process comprising the steps of:

(a)    providing  fresh  tea  leaves  from  the  plant  Camellia
30    sinensis  var.  assamica;  then

(b)    heat-treating the fresh leaves to arrest enzyme action; then


(c)    macerating the fresh leaves with a rotorvane and a double-cone processor, preferably by passing the fresh leaves through the rotorvane to produce

partially macerated leaves and then passing the partially macerated leaves through the double-cone processor to produce the macerated leaves; then

(d)    drying  the  macerated  leaves;  and  then

(e)    optionally sorting the dried macerated leaves according to particle size.



13.    A process for manufacturing a green leaf tea comprising the steps of:

(a)    providing  fresh  tea  leaves   from  the  plant  Camellia

sinensis  var.  assamica;  then

(b)    heat-treating the fresh leaves to arrest enzyme action; then


(c)    macerating the fresh leaves with a rotorvane and a double-cone processor, preferably by passing the

fresh leaves through the rotorvane to produce partially macerated leaves and then passing the partially macerated leaves through the double-cone processor to produce the macerated leaves; then

(d)    drying  the  macerated  leaves;  and  then

(e)    optionally sorting the dried macerated leaves according to particle size.

Newsletter

Join our newsletter for CIPIT news through subscriptions!

SEND

Social Media

    

Contact Us

TEL : (254) 703 034 612