WO2013160097A1

WO2013160097A1 - A process for producing a tea product

Info

Publication number: WO2013160097A1
Application number: PCT/EP2013/057369
Authority: WO
Inventors: Vadivel Govindaswamy; Amita JACOB; Venkatraj Venkatrao Narayanan; Gurmeet Singh
Original assignee: Unilever N.V.; Unilever Plc; Conopco, Inc., D/B/A Unilever
Priority date: 2012-04-27
Filing date: 2013-04-09
Publication date: 2013-10-31
Also published as: AR090858A1

Abstract

The present invention relates to a process for producing a black tea product. Although there are prior art documents which disclose processes that result in black tea products which have good colour characteristics, still there is need for a black tea product and a process for producing the same which is rich in red colour when constituted into a beverage and also a black tea beverage with improved red color. It is another object of the present invention to provide a black tea product which is significantly rich in red color when constituted into a beverage. The present invertors while working extensively to improve the sensorials of black tea products surprisingly have found that addition of a particular amount of ascorbic acid along with tannase in the fermentation stage produces a tea product which is significantly richer in red color when constituted into a beverage.

Description

A process for producing a Tea product

Technical Field

The present invention relates to a process for producing a tea product, more particularly a black tea product.

Background

Black tea is generally prepared by a process which includes the steps of withering, macerating, fermenting and firing/drying. The characteristic colour, flavour and aroma of black tea are produced during fermentation. The term fermentation is traditionally used in tea processing to refer to enzymatic oxidation. The tea is dried at high temperature after fermentation to arrest enzyme action and to bring down the moisture to a low level. Tea based beverages can be consumed either as a hot beverage or as a cold beverage or as a beverage which is at ambient (-25° C) temperature. Whichever way they are consumed, the sensorials of tea products are of prime concern. Sensorials of black tea products include colour, appearance and aroma. Among these factors, colour is one of the most important. Colour imparts impact to the black tea liquor. It is believed that black tea with a rich red coloured liquor is widely preferred by consumers.

There are tea manufacturing processes for improving sensorial properties of black tea product disclosed in the art.

US2001/0033880 (Unilever, 2001 ) discloses a process for manufacturing a black leaf tea that is infusible in hot or cold water. The process involves macerating freshly plucked tea leaves, allowing them to ferment, firing the leaves to arrest fermentation and then drying them to yield black leaf tea, wherein the tea leaves are treated with a solubilising compound selected from ascorbic acid, dehydroascorbic acid, 1 -scorbamic acid, 5-phenyl-3,4-diketo-gamma- butyrolactone (4-phenyl-2,3-diketo-gamma-butyrolactone) or their salts and mixtures thereof in an amount that is sufficient for the black leaf tea to be soluble in water at 5 to 100°C.

US2001/0048956 (Unilever, 2008) discloses a process for manufacturing black leaf tea that looks and feels like orthodox processed tea but has the liquor characteristics of a fuller fermented CTC processed tea. The process involves withering a first supply of freshly plucked tea leaves, macerating the withered leaves, allowing the macerated withered leaves to ferment to produce macerated dhool, withering a second supply of freshly plucked tea leaves, mixing the macerated dhool obtained from the first supply of leaves with the withered leaves obtained from the second supply of leaves, rolling the mixture, allowing the rolled mixture to ferment, and drying the fermented mixture to yield black leaf tea.

Although there are prior art documents which disclose processes that result in black tea having good colour characteristics, still there is need for a black tea product and a process for producing it which is rich in red colour when constituted into a beverage and also a black tea beverage with improved red colour.

Objects of the invention

It is therefore an object of the present invention to provide a black tea product. It is another object of the present invention to provide a black tea product which is significantly rich in red color when constituted into a beverage.

It is a further object of the present invention to provide a process for producing a black tea product which is significantly rich in red colour when constituted into a cold and as well as a hot tea beverage. It is yet a further object of the present invention to provide a process for producing a black tea product which is significantly rich in red colour when constituted into a cold and as well as a hot tea beverage, by incorporation of some natural material.

It is yet another object of the present invention to provide a suitable alternative for producing a black tea product with improved red colour. The present invertors while working extensively to improve the sensorials of black tea product surprisingly have found that addition of a particular amount of ascorbic acid along with tannase in the fermentation stage produces a tea product which is significantly richer in red colour when constituted into a beverage. The present inventors also found that this effect of improved red colour generation is possible for both cold and as well as for hot brew when reconstituted into a beverage.

Summary of the invention

In a first aspect of the present invention there is provided a process for preparation of a black leaf tea product comprising the steps of:

a. providing fresh tea leaf,

b. macerating the tea leaf;

c. fermenting the macerated tea leaf ; and

d. drying the fermented tea leaf to a moisture content of less than 10% by dry mass of tea leaf to obtain the tea product, characterized in that during the fermentation step

i. 0.001 to 1 % of tannase by dry mass of tea leaf; and,

ii. ascorbic acid or a soluble salt of it or a derivative thereof or a natural source of ascorbic acid

are added to the tea leaf. These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention. 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. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about". Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated. Detailed description of the invention

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

"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 weight (i.e. "made tea").

"Black tea" refers to substantially fermented 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. 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, buds and/or stem that have never been dried to a water content of less than 30% by weight, and usually have water content in the range 60 to 90%.

Process for preparation of the tea product

The present invention provides a process for preparation of a black leaf tea product comprising the steps of:

a. providing fresh tea leaf,

b. macerating the tea leaf;

c. fermenting the macerated tea leaf ; and

d. drying the fermented tea leaf to a moisture content of less than 10% by dry mass of tea leaf to obtain the tea product, characterized in that during the fermentation step, ;

i. 0.001 to 1 % of tannase by dry mass of tea leaf; and,

ii. ascorbic acid or a soluble salt of it or a derivative thereof or a

natural source of ascorbic acid

are added to the tea leaf. Optionally after plucking the fresh tea leaf it is subjected to a step known as withering. The tea leaf may include leaf, buds, stem and other parts of the tea plant. Withering is a process where plucked tea leaf is allowed to lose moisture over a period of time preferably in a shallow trough where biochemical reactions occur causing formation of many beneficial compounds including aroma compounds. Preferably to speed-up the moisture losing process fresh dry air is passed in a regulated manner through the leaf. Generally withering is carried out for a period of 10 to 18 hours, more preferably for 12 to 16 hours.

Maceration is a process where the tea cellular structure is broken down, which causes further biochemical reactions to occur. This can be done in different ways. Preferably it is done either by CTC or by the orthodox method. The main aim of this process is to damage the leaf to break the cellular structure. In the CTC process it is done by a CTC machine where three actions viz. cutting, tearing and curling are performed on the tea leaf. In the orthodox process it is done by subjecting the tea leaf to a rolling movement under pressure and then twisting the leaf thereby rupturing the cells and releasing the juice.

Maceration is carried out after plucking of the fresh tea leaf; preferably

maceration is carried out after an optional step of withering to obtain the black tea product of the invention.

The macerated leaf is then fermented which is a process in which enzymes in the tea leaf use atmospheric oxygen to oxidize various substrates to produce coloured products. According to the present invention, during the fermentation step

i. 0.001 to 1 % of tannase by dry mass of tea leaf; and,

are added to the tea leaf.

Tannin acyl hydrolase is commonly referred as tannase. Tannase finds application in many industrial sectors which include the pharmaceutical, food, chemical and beverage industries (P.D. Belur and G. Mugeraya, 201 1. Microbial Production of Tannase: State of the Art. Research Journal of Microbiology, volume 6: page: 25-40). Tannase is an acyl hydrolase enzyme which degallates gallated polyphenolic components present in leaf tea. Without wishing to be bound by theory it is believed that tannase degallates epicatechin gallate (ECG) to epicatechin (EC) and epigallocatechin gallate (EGCG) to epigallocatechin (EGC). The subsequent fermentation results in the formation of primarily theaflavins.

Tannase is added in an amount from 0.001 to 1 %, preferably from 0.01 to 1 %, more preferably 0.01 to 0.1 % by dry mass of tea leaf. Ascorbic acid or a soluble salt or a derivative thereof or a natural source of ascorbic acid is also added at the fermentation stage.

The natural source of ascorbic acid is preferably a fruit. There are a number of fruits available which have a high amount of ascorbic acid in it e.g. Amla

(Phyllanthus emblica), Kiwifruit green (Actinidia deliciosa), Kiwifruit yellow (Actinidia chinensis), acerola (Maipighia glabra), Blackcurrant (Ribes nigrum), Kakadu Plum (Terminalia ferdinandiana) and many others. The most preferred one is acerola. Acerola is a cherry kind of fruit having scientific name of Maipighia glabra I

Maipighia emarginata. It is also known as Barbados cherry which is native to the West Indies and northern South America. It is also cultivated in many other countries throughout the world which includes India, China etc. It is known to have very high content of ascorbic acid. Acerola extracts (in liquid and also in powder forms) are available in the market throughout the globe and marketed by various companies.

Ascorbic acid or a soluble salt or a derivative thereof or a natural source of ascorbic acid is preferably added in an amount from 1 to 25%, preferably from 2 to 20% and more preferably from 4 to 20% by dry mass of tea leaf. Even mixtures of ascorbic acid with a soluble salt of it with a derivative thereof with a natural source of ascorbic acid may be added. Some examples of ascorbic acid, soluble salts and a derivative include sodium and/or potassium salts of ascorbic acid, de-hydro ascorbic acid, 1 -scorbamic acid etc. Soluble salt herein preferably means water soluble salt of ascorbic acid.

Tannase and ascorbic acid or a soluble salt of it or a derivative thereof or a natural source of ascorbic acid may be added together or separately one after another. There is no particular preference of the order of addition. Preferably tannase and ascorbic acid or a soluble salt of it or a derivative thereof or a natural source of ascorbic acid is added in solution form in water due to better distribution in the solid tea matrix. It is further preferred that the tannase is added at the beginning of fermentation, more preferably just after maceration. The ascorbic acid or soluble salt or derivative thereof or natural source of ascorbic acid may be added any time during the fermentation process provided that it gets sufficient time in contact with the tea leaf. Sufficient time preferably means 20 - 70 minutes, more preferably 30 - 60 minutes.

Fermentation after addition of ascorbic acid or a soluble salt of it or a derivative thereof or a natural source of ascorbic acid is preferably carried out for about 20 to 90 minutes, preferably for 30 to 90 minutes and more preferably form 40 to 90 minutes.

The fermented leaf is then subjected to drying. The tea leaf is dried to a moisture content of less than 10%, preferably less than 5%, more preferably 2-3% by dry mass of the tea leaf. Drying is the process where the tea leaf is contacted with air at a temperature of preferably 50-100°C, during which the leaf loses moisture and the enzyme activities are stopped. A tray drier or fluidized bed drier is preferably used for drying the tea leaf. Tea product of the invention

The colour of the black tea liquor can be charaterized by its L^*, a^* and b^* values. The International Commission on Illumination (CIE) introduced CIE L^*a^*b^* scale of colour measurement, based on the opponent-colours theory, which assumes that the receptors in the human eye perceive colour as the following pairs of opposites:

Light-Dark

Red-Green, and

Yellow-Blue.

The CIE L^*a^*b^* colour scale is an approximately uniform colour scale. In a uniform colour scale, the differences between points plotted in the colour space correspond to visual differences between the colours plotted. The CIE L^*a^*b^* colour space is organized in a cube form. The L^* axis runs from top to bottom. The maximum value for L^* is 100, which represents a perfect reflecting diffuser. The minimum is L^*=0, which represents black. The a^* and b^* axes have no specific numerical limits. Positive a^* is red and negative a^* is green. Similarly, positive b^* is yellow and negative b^* is blue. CIE L^*a^*b^* values are preferably measured using a color measuring instrument e.g. spectrophotometer. A Hunterlab color measuring instrument is preferably used for this purpose. The colour measurements are preferably carried out under D65 illuminant. D65 is a standard illuminant defined by the CIE. The D65 illuminant is intended to represent average daylight throughout the visible spectrum.

Redness values of infusions of the black tea product of the invention brewed in room temperature (~25°C) water or hot water were measured. The black leaf tea product of the present invention is generally infusible in an amount of 2 parts of tea leaf in 100 parts of water for 2 minutes at 25°C to provide an infusion having a redness value (a^*) as measured on CIE L^*a^*b^* scale using D65 illuminant at 25°C of greater than 9, preferably greater than 10, more preferably greater than 12 and most preferably greater than 16.

The black leaf tea product of the present invention is generally infusible in an amount of 2 parts of tea leaf in 100 parts of water for 2 minutes at 100°C to provide an infusion having a redness value (a^*) as measured on CIE L^*a^*b^* scale using D65 illuminant at 25°C of greater than 36, preferably greater than 37, more preferably greater than 40.

Although there is no particular upper limit for the value of a^*, it may well be up to 70, preferably up to 60, more preferably up to 50.

Now the invention will be demonstrated with the help of examples. The examples are for the purpose of illustration of the invention and in no way limit the scope of the invention. Examples

Process of preparation of black tea product of the invention

Fresh tea leaves sourced from the southern part of India were withered to 70% moisture content, and then subjected to a maceration process of 4 passes through a CTC machine. The dhool obtained was treated with various

concentrations of tannase as mentioned in Table 1 and 2. After that the tannase- treated dhool was left for fermentation (air oxidation) for 45 minutes at 25°C. After -45 minutes the required concentration (as per Table 1 and 2) of ascorbic acid or acerola fruit extract solution (dissolved in Dl water) was added to the dhool and mixed well. It was then allowed to undergo fermentation for about 45 minutes. Then the dhool was dried in a laboratory scale mini fluidized bed dryer (Sherwood Scientific, Model No: HST/EQ/30) with the inlet air temperate set at 120°C and then the dhool was fluidized for about 25 minutes. The final moisture content of the dried tea was ~4 %. This process was used to make the tea products of examples 1 to 10.

Process of preparation of control black tea products

There were four sets of control examples. In the first set the dhool was treated with ascorbic acid only. In the second set the ascorbic acid was replaced by acerola fruit extract and in the third set the dhool was treated with tannase only. The fourth set did not have anything added (i.e. conventional black tea

production).

For the first and second sets, fresh tea leaves sourced from the southern part of India were withered to 70% moisture content, and then subjected to a maceration process 4 passes through a CTC machine. The dhool obtained was then left for fermentation (air oxidation) for 45 minutes at 25°C. After 45 minutes various amounts of ascorbic acid or acerola fruit extract solution (dissolved in Dl water) were added to the dhool and mixed well. It was then allowed to undergo fermentation for about 45 minutes. Then the dhool was dried in a laboratory scale mini fluidized bed dryer (Sherwood Scientific, Model No: HST/EQ/30) with the inlet air temperate set at 120°C and then the dhool was fluidized for about 25 minutes. The final moisture content of the dried tea was ~4 %. This process was used to make the tea products of examples D, E, F, G, K, L, M and N.

For the third set, fresh tea leaves sourced from the southern part of India were withered to 70% moisture content, and then subjected to a maceration process of 4 passes through a CTC machine. The dhool obtained was treated with various concentrations of tannase and left for fermentation (air oxidation) for 90 minutes at 25°C. Then the dhool was dried in a laboratory scale mini fluidized bed dryer (Sherwood Scientific, Model No: HST/EQ/30) with the inlet air temperate set at 120°C and then the dhool was fluidized for about 25 minutes. The final moisture content of the dried tea was ~4 %.This process was used to make the tea products of examples B, C, I and J.

For the fourth set, fresh tea leaves sourced from the southern part of India were withered to 70% moisture content, and then subjected to a maceration process of 4 passes through a CTC machine. The dhool was left for fermentation (air oxidation) for 90 minutes at 25°C. Then the dhool was dried in a laboratory scale mini fluidized bed dryer (Sherwood Scientific, Model No: HST/EQ/30) with the inlet air temperate set at 120°C and then the dhool was fluidized for about 25 minutes. The final moisture content of the dried tea was ~4 %. This process was used to make the tea products of examples A and H. Process of preparation of the tea infusions from the tea products

Room temperature infusion: 2 g of tea leaf product was taken in a 100 ml_ ceramic cup, and then 100ml_ of room temperature water (25°C) was added and infused for 2 minutes with stirring. Then the liquor was filtered using a tea strainer.

Hot water infusion: 2 g of tea leaf product was taken in 100 ml_ ceramic cup, and then 100ml of hot water (~100°C) was added and infused for 2 minutes with stirring. Then the liquor was filtered using a tea strainer. Colour measurement:

Colour (CIE L^*a^*b^* values) was measured using a Hunter lab Ultrascan XE (Model-USXE/UNI version 3.4, Hunterlab Associates Laboratories Inc. Virginia). A halogen cycle lamp was used as the light source. The illuminant used was D65 and the measurements were made at 10°-Observer angle. Measurements were made using a quartz cuvette of 10mm path length. The infusion was filled up to the brim in the cuvette and placed in the instrument for color measurement. The instrument was calibrated using a standard white tile (Hunterlab Duffuse/8°, mode-RSEX, Port-1 " and area- large) in accordance with the instructions provided in the instruction manual. The a^* values were measured at room temperature (~25°C).

Comparison of red colour (a^*) value of the black tea infusions

For the colour measurement the tea infusions were prepared for the various samples as tabulated in the following Table 1. Examples A - J are outside the scope of the present invention whereas Examples 1 - 1 1 are according to the present invention. Then the a^* value of the infusion was measured using the method as described herein above. The results are summarized in the following Table 1 (for room temperature brew) and Table 2 (hot water brew). Table 1

Example Ascorbic acid Acerola fruit Tannase a^* value

Number (Wt %) extract (Wt %) (Wt %)

A - - - -3.4

B - - 0.01 -2.22

C - - 0.1 1.48

D 1 - - 4.32

1 1 - 0.01 16.18

2 1 - 0.1 19.78

E - 5 - 8.28

3 - 5 0.01 9.50

4 5 0.1 9.82

F 4 - - 26.55

5 4 - 0.01 27.51 G - 20 - 29.91

6 - 20 0.01 30.79

From Table 1 it is evident that the examples which are inside the scope of the present invention provide higher a^* values than the control examples, i.e.

Examples 1 to 6 provide a tea infusions with improved red colour compared to Example A (no treatment), B and C (only tannase), D and F (only ascorbic acid) and E and G (only acerola) for room temperature infusion.

Table 2

From Table 2 it is clear that the examples which are inside scope of the present invention provide higher a^* values than the control examples, i.e. Examples 7 to 10 provide tea infusions with improved red colour when compared to Examples H (no treatment), I and J (only tannase), K and M (only ascorbic acid) and L and N (only acerola) in hot infusion. Measurement of Total Polyphenols and Theaflavins

Samples for theaflavin and total polyphenol measurements were prepared by taking 2 g of each of the leaf tea products of Examples A, B, G and 6 in a 100 mL ceramic cup, and then 10OmL of room temperature water (25°C) was added and infused for 2 minutes with stirring. Then the liquor was filtered using a tea strainer. This liquor was used for the analysis.

The theaflavin (TF) content was measured by the following protocol. Samples were analysed by HPLC (Shimadzu LC-10A HPLC) using an octadecylsilica (C18) column (Nova-pak ex. Waters, 3.9 mm i.d. * 150 mm) with detection at a wavelength of 380 nm, column temperature of 40°C, injection volume of 20 micro L and flow rate of 1 mL/min. The mobile phases for the theaflavin analysis were 2% (v/v) acetic acid in water (as mobile phase A) and acetonitirile (as mobile phase B). A linear gradient from 8% B to 69% B over 50 min was used to separate the theaflavins, following which the column was equilibrated with 8% of buffer A for 5 min. Pure theaflavins (Sigma Aldrich, > 90%, HPLC grade) were used as the standard for quantification. The total polyphenol (TPP) content was measured using the ISO method for the determination of content of total polyphenols in tea - Colorimetric method using Folin-Cicalteu reagent (ISO 14502-1 :2005(E)).

The results of the measurements are shown in Table 3.

Table 3

Example Number Total Polyphenols (ppm) Theaflavins (ppm)

A 164.5 0

G 268.9 0 B 334 13.8

6 814.3 22.68

From Table 3 it is evident that example 6 (according to the present invention) provides a tea infusion with a much higher amount of polyphenols and theaflavins than the control examples (Examples A, G and B).

It is therefore possible by way of the present invention to invention to provide a black tea product which is significantly rich in red color when constituted into a beverage. The present invention also provides a suitable alternative process for producing a black tea product with improved red colour.

Claims

Claim:

1. A process for preparation of black leaf tea product comprising the

steps of:

a. providing fresh tea leaf,

b. macerating the tea leaf;

c. fermenting the macerated tea leaf ; and

d. drying the fermented tea leaf to a moisture content of less than 10% by dry mass of tea leaf to obtain the tea product, characterized in that said fermentation step includes the addition of; i. 0.001 to 1 % of tannase by dry mass of tea leaf; and, ii. ascorbic acid or a soluble salt of it or a derivative thereof or a natural source of ascorbic acid.

2. A process as claim in claim 1 wherein there is an additional step of withering the fresh tea leaf in between step (a) and step (b).

3. A process as claimed in any one of the preceding claims wherein the amount of tannase added in the fermentation process is in the range of 0.01 to 0.1 % by dry mass of tea leaf.

4. A process as claimed in any one of the preceding claims wherein the amount of ascorbic acid or a soluble salt or a derivative thereof or a natural source of ascorbic acid added in the fermentation step is in the range of 1 to 25% by dry mass of tea leaf.

5. A process as claimed in claim 4 wherein the amount of ascorbic acid or a soluble salt or a derivative thereof or a natural source of ascorbic acid added in the fermentation step is in the range of 2 to 20% by dry mass of tea leaf.

6. A process as claimed in any one of the preceding claims wherein the natural source of ascorbic acid is a fruit.

7. A process as claimed in claim 6 wherein the fruit is Malpighia

emarginata.

8. A black leaf tea product obtainable by the process as claimed in any one of the preceding claims.

9. The black leaf tea product as claimed in claim 8 which is infusible in an amount of 2 parts of tea leaf in 100 parts of water for 2 minutes at 25°C to provide an infusion having a redness value (a^*) as measured on CIE L^*a^*b^* scale using D65 illuminant at 25°C of higher than 9.

10. The black leaf tea product as claimed in claim 8 which is infusible in an amount of 2 parts of tea leaf in 100 parts of water for 2 minutes at 100°C to provide an infusion having a redness value (a^*) as measured on CIE L^*a^*b^* scale using D65 illuminant at 25°C of higher than 36.