WO2016173810A1

WO2016173810A1 - A process of producing a tea product

Info

Publication number: WO2016173810A1
Application number: PCT/EP2016/057422
Authority: WO
Inventors: Gurmeet Singh; Sreeramu GUTTAPADU; Lokesh Basavaraju; Babu Rakesh Kumar Bandi
Original assignee: Unilever N.V.; Unilever Plc; Conopco, Inc., D/B/A Unilever
Priority date: 2015-04-29
Filing date: 2016-04-05
Publication date: 2016-11-03
Also published as: AR104435A1

Abstract

The present invention discloses a process for producing a leaf tea product comprising the step of treating plucked tea leaf with harpin.

Description

A PROCESS OF PRODUCING A TEA PRODUCT

Technical Field The present invention relates to a tea product and more particularly the present invention relates to a black tea product.

Background of the invention Tea is one of the most extensively consumed beverages in the world. There are different varieties of tea e.g. black tea, green tea, oolong tea, white tea etc. Among different varieties, black tea products are more popular. Black tea is generally prepared by the process which includes the steps of withering, macerating, fermenting and firing/drying. The characteristic colour, flavour and aroma of black tea get generated during fermentation. The term fermentation is traditionally used in the tea processing to refer to enzymatic oxidation. The tea is dried at high temperature after fermentation to arrest the enzyme action and to bring down the moisture to a low level.

In case of black tea beverage, consumers consider sensorials as the prime factor. Sensorials of black tea product mainly include colour, appearance and aroma. Among these factors, colour is one of the most important one to be considered. Colour imparts impact to the black tea liquor. It is believed that black tea with rich red coloured liquor is widely preferred by consumers. There have been efforts to provide black tea products with enhanced red colour. US2008/01 18602 (Unilever) discloses a process for the manufacture of a tea product which is readily infusible and has improved red colour. The process comprises contacting black tea with ascorbic acid and/or its salts, an oxidizing agent and water for a period of at least 5 minutes followed by drying to prepare a tea product that is infusible in water at 5 to 100°C.

We have also found that in whatever way a leaf tea product is brewed, the leaf tea waste produced after brewing the beverage contains a good amount of polyphenols which remain unused and go as waste after the brewing process. Polyphenols are considered to be the major constituents in most of the tea product. It is believed that the polyphenols provide the required taste (astringency, bitterness etc.) for a tea product and also provide various health benefits. Polyphenols are known to be one of the "tea goodies".

There are also been efforts to increase the polyphenols content in a tea product.

WO 2012/133901 (KANNO MINORU et.al.) describes a polyphenol increasing agent for plant leaves that enables an increase in the storage life of plant leaves such as leaf vegetables and tea leaves, a polyphenol and amino acid increasing agent for plant leaves, a resin pellet, a plant leaf storage sheet, and a method for manufacturing a plant leaf storage sheet.

Although prior art discloses process for producing a tea product with enhanced red colour and increase polyphenol, still there is need to provide a tea product with even richer red colour. Furthermore, prior art is silent about how to increase the extractability of the polyphenols from the leaf matrix to utilize the polyphenols that are already there in the leaf and which are otherwise discarded with the used tea leaves as waste after brewing the beverage.

It is therefore an object of the present invention to provide a tea product with enhanced red color.

It is another object of the present invention to provide a process which improves the extractability of the polyphenols from the tea leaf.

It is a further object of the present invention to provide a black leaf tea product with relatively higher polyphenols delivery at the end cup to minimize the wastage of polyphenols.

It is yet a further object of the present invention to provide a tea product with enhanced red colour along with improved extractability of the polyphenols. The present inventors while working extensively to solve these problems have surprisingly found that adding harpin at a particular stage of black tea manufacturing process produces a tea product with enhanced red colour and increased polyphenols content thereby satisfying one or more of the above mentioned objects.

Summary of the invention

In a first aspect the present invention provides process for producing a leaf tea product comprising the steps of withering fresh tea leaf in presence of harpin.

In a second aspect the present invention provides a tea product as obtained and/or obtainable by the process of the first aspect. 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. 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. Especially preferred is material from var. assamica as this has a higher level of tea actives than var. sinensis.

"Leaf tea" for the purposes of this invention means a tea product that contains tea leaves and/or stem in an un-infused 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%.

The present invention provides a process for producing a leaf tea product comprising the step of treating plucked tea leaf with harpin.

Harpin is a protein. Harpins were discovered in 1992 by Cornell University & harpin is produced by Gram-negative phytopathogenic bacteria (Erwinia amylovora) and typically elicits hypersensitive response (HR) in non host plants. Harpin Protein triggers a Systemic Acquired Resistance (SAR), a well-known plant defense mechanism that provides resistance to a variety of viral, bacterial, and fungal pathogens. Harpin Proteins triggers signals throughout the plants to activate certain defensive and growth responses. These vigorous responses to the threat of disease help the plants survive the stresses and other threats the diseases present. The Harpin Protein response among plants is so prevalent and extensive that the resulting beneficial activity has been documented across a broad spectrum of crops including Field Crops, Vegetables, Tree Fruit and Vines, Turf and Ornamental and Specialty Crops. According to process of the present invention the amount of harpin added preferably is in the range of 0.001 to 2 % by weight and more preferably is in the range of 0.01 to 1 % by weight of plucked tea leaf. Preferably harpin is added at the step of withering the plucked tea leaf. Withering is a process where plucked tea leaf are 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 loosing process, fresh dry air is passed in a regulated manner through the leaf. The tea leaf may include leaf, buds, stem and other parts of the tea plant. The time of withering is preferably in the range of 4 to 96 hours, more preferably 4 to 72 hours, even more preferably for 4 to 48 hours and most preferably 4 to 40 hours.

Preferably withering is performed under anaerobic conditions.

The term "anaerobic conditions" as used herein means that the gas phase in contact with the leaf has less than 3% oxygen by volume. The amount of oxygen in the gas phase in contact with the leaf is preferably less than 2%, more preferably less than 1 %. It is particularly preferred that the gas phase in contact with the leaf is substantially free of oxygen.

The anaerobic conditions are optionally achieved by:

i. placing the fresh tea leaf in a container, and closing the

container, or

ii. placing the tea leaf in a container, purging a gas other than

oxygen through the container, and closing the container, or placing the leaf in an airtight chamber or under vacuum.

By placing the fresh leaf in a container and closing the container, the oxygen concentration in the gas phase decreases with time and anaerobic conditions are achieved after keeping the container closed for a certain amount of time. The container is closed for a duration of preferably greater than about 3 hours, more preferably greater than 4 hours and most preferably greater than about 6 hours or even greater than about 8 hours.

Alternatively and more preferably, the anaerobic conditions are achieved by placing the leaf in a container, purging a gas other than oxygen through the container and closing the container. The gas other than oxygen is preferably nitrogen or carbon dioxide, more preferably nitrogen.

Once the container is closed in step (i) or (ii) above, there is no particular restriction as to the pressure in the container. The pressure inside the closed container is preferably from 1 -1000 mm Hg absolute, more preferably 10-800 mm Hg absolute and most preferably about 20.

The temperature of withering is preferably in the range 4°C to 60°C, preferably in the range 4 to 55°C, more preferably in the range 10 to 40°C.

Alternately harpin may be added after the withering step.

The withered leaf may preferably be subjected to maceration. This may preferably be carried out by crushing, tearing and curling which is known as CTC. One or more CTC steps may be carried out. In this step the withered leaf breaks up and releases enzymes that exist in the leaf.

Alternately after the withering, the withered tea leaf is rolled in an orthodox roller or comminuted in a rotorvane or combination thereof. During these steps precursors present in the tea leaf become amenable to the enzymes.

The macerated tea leaf preferably undergoes fermentation. Fermentation is preferably carried out by keeping the leaf at a temperature of 15 to 35°C for from 15 minutes to 3 hours. Preferably the temperature of the fermentation is between 25 to 35°C and more preferably around 30 to 35°C. The time for fermentation preferably is from 30 minutes to 3 hours and more preferably 1 to 3 hours. In this stage the leaf undergoes enzymatic reactions which produce the typical black tea characteristics.

The fermented tea leaf may then preferably be dried. During drying step, the incubated tea leaf is dried to moisture content preferably less than 10% by total mass of the tea leaf, more preferably less than 5 % by total mass of the tea leaf, to obtain the green leaf tea.

The drying step is preferably carried out by thermal drying, freeze drying or vacuum drying.

Thermal drying is preferably carried out by contacting the leaf with air; with the temperature of air being preferably 50 to 15°C, more preferably 60 to 130°C, most preferably 80 to 120°C. Thermal drying may be carried out in any conventional dryer. However, a fluidized bed dryer or a tray dryer is particularly preferred for thermal drying.

The leaf can also be dried by vacuum drying. During vacuum drying the tea leaf is subjected to an absolute pressure of preferably from 5 to 500 mm Hg, more preferably from 50 to 300 mm Hg and most preferably from 100 to 200 mm Hg. Vacuum drying is carried out at a temperature in the range of preferably 20 to 70°C, more preferably 25 to 60°C and most preferably 30 to 55°C. Vacuum drying may be carried out in any suitable vacuum drier, preferably in a rotary vacuum drier.

The present invention also provides a tea product obtained by the process of the present invention.

Now the invention will be demonstrated with the help of following non-limiting examples.

Examples:

Effect of Harpin on tea bush

Commercial Harpin sourced from Axiom Protein from Rx Green Solution, Netherlands was used for this purpose. 500mg of harpin was dissolved in 50ml_ of Milli-Q water and sprayed uniformly to cover 10 number of tea bushes (South Indian tea plantation). After the spaying the following were performed:

Example A:

Tea leaves were plucked 12 hours after spraying followed by 18 hours of withering. After that the tea leaves were subjected to CTC (cut tear curl) for 4 times to obtain macerated dhool. The macerated dhool was then fermented (exposed to air at 25°C) for 90 minutes followed by drying the fermented dhool at 120°C till the moisture level went down to less than 5% by weight.

Example B:

This example is same as Example A except that the tea leaves were plucked 24 hours after spraying. Example C:

This example is also same as Example A except that the tea leaves were plucked 48 hours after spraying.

Example D:

In this example only Milli-Q water of 50ml_ (without any harpin) was sprayed on 10 tea bushes and the leaves were plucked after 24 hours followed by similar procedure as per Example A.

Tea infusions were then made using the above obtained tea products by following the protocol as described below:

The infusions were prepared by adding 200 ml_ of boiling water to 2g of dried leaf, allowing it to stand for 2 min and stirring once before straining. These infusions were used for measuring the polyphenol content and a^* value by using the protocol as described below: Measurement of polyphenol content:

The polyphenols content was measured by 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 polyphenols content are expressed below by dry weight of tea leaves. Measurement of colour of the infusions: 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 10 mm path length. Tea 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 instructions manual. The L^*a^*b^* values were measured at room temperature (~25°C). Positive a^* is red and negative a^* is green. The higher the a^* value, the redder the infusion is.

The results are summarized below in Table 1 : Table 1

Example Number Polyphenol Content (%) a^* Value

A 5.50 1 1 .51

B 5.40 12.02

C 5.38 1 1 .81

D 5.35 1 1 .85 From the above Table it is clear that treatment of tea leaf with harpin before plucking (on the bush) does not have any effect on the colour of the infusion and also with its polyphenols content. Effect of Harpin on plucked leaf

The experiments were performed as per the following:

Example 1 :

100 mg of harpin dissolve in 50 ml_ of Milli-Q water was sprayed on 1 kg of freshly plucked tea leaf (South Indian tea plantation) followed by 24 hours of withering. After that the tea leaves were subjected to CTC (cut tear curl) for 4 times to obtain macerated dhool. The macerated dhool was then fermented (exposed to air at 25°C) for 90 minutes followed by drying the fermented dhool at 120°C till the moisture level went down to less than 5% by weight.

For Example 2, 3, 4, 5 and 6 the same procedure of Example 1 was followed except the amount of harpin added was 200 mg, 300 mg, 500 mg, 1000 mg and 5000 mg, respectively. For all the examples the respective amount of harpin was dissolve in 50 ml_ of Milli-Q water and sprayed on 1 kg of freshly plucked tea leaf (South Indian tea plantation).

As a control batch (Example E), 50 ml_ of Milli-Q water without any harpin was sprayed on 1 kg of freshly plucked tea leaf followed by withering, maceration, fermentation and drying as described above.

Tea infusions were prepared using the above samples followed by the measurement of polyphenol content and a^* by following the protocol as described in previously in this specification. The results of these experiments are summarized below in Table 2: Table 2

From the above Table 2 it is evident that the examples (Examples 1 to 6) according to the present invention provide an infusion with much redder in colour and also with higher amount of polyphenols. It is interesting to note that the red colour of the infusion is increasing with the enhanced doses of harpin (Examples 1 to 4). Once it reaches the maximum, after that the increase doss of harpin does not have much effect on the red colour.

Effect of withering time with Harpin addition:

In this set of examples the harpin was added to the plucked tea leaves and the withering time was varied to find out the effect of withering time on the colour (a^*) of the infusion and its polyphenol content. For this purpose, 500mg of harpin was dissolved in 50ml Milli-Q water and sprayed uniformly on freshly plucked tea leaves followed by withering for different times as per Table 3. After that the tea leaves were subjected to CTC (cut tear curl) for 4 times to obtain macerated dhool. The macerated dhool was then fermented (exposed to air at 25°C) for 90 minutes followed by drying the fermented dhool at 120°C till the moisture level went down to less than 5% by weight.

For each withering time there was a control set of tea leaves (examples F, G, H and I) in which no harpin was added. Tea infusions were prepared using the above samples followed by the measurement of polyphenol content and a^* by following the protocol as described in previously in this specification. The results of these experiments are summarized below in Table 3.

Table 3

It is evident from the above Table 3 that the examples within the scope of the present invention provides much redder (a^* value) infusion with high polyphenol content when compared with its respective control. It is also evident from the results that the colour and polyphenols are increases progressively till 48 hrs and stay consistent thereon. Effect of Harpin added during fermentation:

For these experiments harpin was added at the time of fermentation in the macerated tea leaves.

Example 1 1 :

1 kg of freshly plucked tea leaf (South Indian tea plantation) was plucked followed by 24 hours of withering. After that the tea leaves were subjected to CTC (cut tear curl) for 4 times to obtain macerated dhool. After that, 1500mg of harpin was dissolved in 50ml_ of Milli-Q water and sprayed uniformly on dhool macerated dhool and allowed for 90min fermentation (exposed to air at 25°C). Then, the fermented leaves were dried at 120°C till the moisture level went down to less than 5% by weight.

5 Example J:

This is a control example. All procedure is same as Example 1 1 except no harpin was added at the time of fermentation. Instead of harpin only 50 ml_ of Milli-Q water was added. 0 Tea infusions were prepared using the above samples followed by the measurement of polyphenol content and a^* by following the protocol as described in previously in this specification.

The results of these experiments are summarized below in Table 4:

5

Table 4

From the above Table 4 it is evident that addition of harpin at the time of fermentation o produces a tea product with higher a^* value.

Effect of anaerobic incubation on Harpin treatment

For this purpose three sets of samples have been prepared. These are described as5 Example K, 12 and 13.

Example K:

Freshly plucked tea leaves were obtained from South Indian tea plantation followed by 24 hours of withering. After that, the tea leaves were subjected to CTC (cut tear curl) for 4 times to obtain macerated dhool. The macerated dhool was then fermented (exposed to air at 25°C) for 90 minutes followed by drying the fermented dhool at 120°C till the moisture level went down to less than 5% by weight. This is the regular process of producing black leaf tea product.

Example 12:

For this example, 500 mg of harpin dissolve in 50 ml_ of Milli-Q water was sprayed on 1 kg of freshly plucked tea leaf (South Indian tea plantation) followed by 24 hours of withering. After that the tea leaves were subjected to CTC (cut tear curl) for 4 times to obtain macerated dhool. The macerated dhool was then fermented (exposed to air at 25°C) for 90 minutes followed by drying the fermented dhool at 120°C till the moisture level went down to less than 5% by weight. This is actually repetition of Example 4 with different sets of tea leaves. Example 13:

For this example, 500 mg of harpin dissolve in 50 ml_ of Milli-Q water was sprayed on 1 kg of freshly plucked tea leaf (South Indian tea plantation) and placed in an air-tight aseptic plastic bag, sealed and incubated for 24 hours at ~25°C. After that the tea leaves were subjected to CTC (cut tear curl) for 4 times to obtain macerated dhool. The macerated dhool was then fermented (exposed to air at 25°C) for 90 minutes followed by drying the fermented dhool at 120°C till the moisture level went down to less than 5% by weight.

Tea infusions were prepared using the above samples followed by the measurement of polyphenol content and a^* by following the protocol as described in previously in this specification.

The results of these experiments are summarized below in Table 5: Table 5

From the above Table 5 it is evident that addition step of anaerobic incubation in presence of harpin leads to dramatic and much significant increase of polyphenol content and a^* value of the end tea product.

Claims

Claims:

1 ) A process for producing a leaf tea product comprising the step of treating plucked tea leaf with harpin.

2) A process as claimed in claim 1 wherein the amount of harpin added is in the range of 0.001 to 2 % by weight of plucked tea leaf.

3) A process as claimed in claim 2 wherein the amount of harpin added is in the range of 0.01 to 1 % by weight.

4) A process as claimed in any one of the preceding claims 1 to 3 wherein harpin is added at the time of withering the plucked tea leaf.

5) A process as claimed in claim 4 wherein withering is performed under anaerobic conditions.

6) A process as claimed in claim 5 wherein the anaerobic conditions are achieved by:

(i) placing the fresh tea leaf in a container, and closing the container, or;

(ii) placing the tea leaf in a container, purging a gas other than oxygen through the container, and closing the container, or placing the leaf in an airtight chamber or under vacuum.

7) A process as claimed in any one of the preceding claims 4 to 6 wherein the time of withering is in the range of 4 to 96 hours.

8) A process as claimed in claim 7 wherein the time of withering is in the range of 4 to 40 hours.

9) A process as claimed in any one of the preceding claims 4 to 8 wherein the temperature during withering is in the range of 4°C to 60°C. 10) A process as claimed in any one of claims 4 to 9 wherein the plucked tea leaf is macerated after withering.

1 1 ) A process as claimed in claim 10 wherein the macerated tea leaf undergoes fermentation.

12) A process as claimed in claim 1 1 wherein the fermented tea leaf undergoes drying.

13) A tea product obtained and/or obtainable by a process as claimed in any one of the preceding claims 1 to 12.