WO2008065675A1

WO2008065675A1 - A process for the preparation of instant tea

Info

Publication number: WO2008065675A1
Application number: PCT/IN2007/000339
Authority: WO
Inventors: Jatish N. Sheth; K. Balasubramanian
Original assignee: Sheth Jatish N; Balasubramanian K
Priority date: 2006-11-27
Filing date: 2007-08-13
Publication date: 2008-06-05

Abstract

The invention concerns a process for the preparation of instant tea which retains the flavour and aroma of freshly brewed tea comprising the steps of: (i) extraction of a mixture of tea leaves filled in a plurality of columns with water to obtain a decoction wherein cyclodextrins are added in the last column, (ii) filtering the decoction, (iii) spray drying the decoction to obtain a powder, and (iv) agglomeration of the powder.

Description

A process for the preparation of instant tea

FIELD OF INVENTION

This invention relates to a process for the preparation of instant tea which retains the flavour and aroma of freshly brewed tea.

PRIOR ART

The existing process of making tea is to first boil some water and then add the tea leaves thereto depending upon individual preferences. The amount of tea leaves added to the boiled water, the extent of boiling/brewing, etc. gives a variation to the flavour, aroma and taste of the cup of tea and the availability of Caffeine, Theoflavins, Thearubigins, antioxidants, etc.

OBJECTS OF THE INVENTION

An object of this invention is to propose a process for the preparation of instant tea, which retains the flavour and aroma of freshly brewed tea.

Another object of this invention is to propose a process for the preparation of instant tea, which can be taken with hot or cold water.

Still object of this invention is to propose a process for the preparation of instant tea, which retains the flavour and aroma of freshly brewed tea, without filtration.

A further object of this invention is to propose a process for the preparation of instant tea, which is convenient to use.

BRIEF DESCRIPTION OF INVENTION

According to this invention there is provided a process for the preparation of

instant tea which retains the flavour and aroma of freshly brewed tea comprising the steps of:

i. extraction in a plurality of columns of a mixture of tea leaves in two immiscible solvents of different polarities to obtain a decoction,

ii. filtering the decoction and then subjecting it to the step of spray drying to obtain a powder,

iii. subjecting the powder to the step of agglomeration.

The process comprises in the step of extracting tea with all the biochemical compounds having their respective characteristics, with specific reference to determine the amount of caffeine in tea and to isolate pure caffeine from the numerous other compounds of which the major components are cellulose in terms of solids which are polymers of glucose, and virtually insoluble in

water, while caffeine is water soluble and during extraction of caffeine and other compounds such as tannins (very large polyphenols) are also extracted. To ideally produce instant tea, the process comprises the use of two mutually immiscible solvents of different polarities such as water and organic solvent. More specifically, the solvents are water and cyclodextrin such as Cavamax (trade name).

The organic solvent may be> an alpha beta and gamma cyclodextrins to isolate the characteristics of the biochemical compounds of specific interest for extraction. The process involves an excess of water to tea leaves, and in the ratio of 1 to 4 to 1:6 and preferably 1.5 of tea leaves to water with heating employed between 5O⁰C to 8O⁰C.

The extraction process of producing instant tea begins with brewing tea leaves. Softened water is passed through for example eight column tea leaves containing either orthodox or CTC graded tea. Preferred temperatures are 50 to 8O⁰C, and preferably are more closer to the higher limit, with

agitation of hot air blown at 50° to 8O⁰C through the column to retain the temperature and to stir the water with lea leaves to obtain a decotion.

The number of columns would vary proportionately when more quantity of tea and water is similar ratios are taken for processing while maintaining the residence time of 8-14 minutes to obtain the final concentrate form with the solids extracted between 40-48 percent. The termpeature of 73 Degree centigrade refers to optimum output with the contents of the extract in desired percentage. The extract column employed would depend more on the volume of extraction of the concentrate, and preferably the ratio of tea leaves to water should be 1 : 5, in a eight column extraction process with a residence time of 8-14 minutes throughout the columns, to extract between 40-48 percent of the solids from the concentrated solution.

Temperature range between 50-80 degree centigrade is set for the extracted components:

COMPONENTS CONCENTRATE G/100G

In wt% of extracted solids

Catechins 3

Theaflavins 5

Thearubigins 12

Flavanols 6

Phenolic acid depsides 8

Amino acids 11

Mehtylxanthines 8

Carbohydrates 9

Proteins 1.2

Mineral water 7

Volatiles 0.05

Caffeine content 3-4

Heating temperature range between 50-80⁰C is suggestive to maintain the aromatic flavours, and miscibility of the volatiles with the concentrate of extraction. If a temperature is maintained below 5O⁰C, the aromatic flavours and the tea cream in the concentrate becomes cloudy, and the final extract dissolution in water forms a haze. Extraction at higher temperatures of more than 8O⁰C the volatiles which are in the range of 0.05g/100g of the extract in component measured terms of wt% of extracted solids are not present and form a compound with phenolic acid which contributes to bitterness, also it results in high extraction of caffeine content which makes the final extracted instant tea more bitter, endangering the briskness of the quality of the instant tea extracted.

Hot air is blown through the entire column range to maintain a temperature bed of 50-80⁰C to circulate between the columns while recording that the temperature range is maintained between 50-80⁰C from the beginning to the end of the columns. 1% Cyclodextrin is added at the last stage of the column as a preferred aroma protector at the final stage of the column before the concentrate is collected with the desired content of the volatiles in the

concentrate as expressed in the table, which otherwise tend to oxidize, for example glycine to formaldehyde, alanine to aceptaldehyde, valine to isobuyraldehyde, leucine to isovaleraldehyde, Methionine to Methional, Phenolic compound containing phenylalnine to phenylactealdehyde. The use of cyclodextrins is to restrict the oxidation of the volaties.

The decotion is filtered which ideally contains 22% to 34% of the solids and condensates such as copolymers of ethylene oxide and propylene oxide are added along with organic solvent and then spray dried to get the instant tea beverage. During the process to preserve the aroma and flavour oxygen is removed from the tea extract, which is achieved by foaming carbon dioxide and/or nitrogen.

The ratio of tea to water of 1 :5 is a preferred choice, through a ratio of 1 :4 and 1 :6 could be employed. The residence time would vary in the instance of 1 :6 ratio and the residence time would vice a versa reduce with the ratio of 1 :4 of tea leaves to water to obtain optimum concentration of the extractions are explained in the concentration g/100g.

Temperature of the columns are maintained in between 50 to 8O⁰C, so that the optimized temperature prior to extraction is brought down between 65- 75⁰C to obtain the components as desired from the extraction.

The pH in the infusion solution should preferably be in the ratio of 1;5 with an ideal pH in the range of 4.5-5.5. While pH decreased between 3.6-4.4 with lower ratio of water to tea leaves as in the case of 1 :4 where the residence time is opted to be the least in the column so that undesired organic compound present in the tea are not formed in the infusion solution. While working with a ratio of 1 :6 the residence time is the most, and the temperature are maintained between 50-60 degree for most part of the residence time and elevating the temperature to 80 degree C at the last part of the residence so that instant reduction of temperature is achieved in the last three minutes to bring the temperature of about 70-73 degree centigrade before extraction.

The objective of residence time and temperature maintenance in each of the three ratio is to get an ideal out put of the desired concentration of the

component of extraction in the last column stage where cavamax is added so that the cyclodexrins preserve and contain the aromatic volatiles to be achieved from the components of extraction. As explained the earlier method and description of the process.

The tea leaves are maintained of a temperature between 50-80 degree centigrade, with an optimum desired temperature of about 23 degree centigrade, the residence time of about 8-14 minutes is through out the columns.

There is a continued blowing of hot air in the columns so as to maintain the temperature not lower than 50 degrees and not more than 80 degrees. The first initial period of for example six minutes of residence time being maintain a data temperature between 50-60 degrees, and the next 3 minutes to elevate the temperature up to 80 degrees and brought down to 73 degrees before final extraction from the columns which is approximately another 3 minutes.

The liquid tea extract is preferably spray dried. Cooled, clarified liquid concentrate is sprayed through a nozzle at the top of a drying tower. Air that has been heated to about 5O⁰C to 6O⁰C is blown downward through the mist to evaporate the water. The air is diverted out of the tower near the bottom, and it is reintroduced during the agglomeration step. The dry tea powder collects in the bottom of the tower before being discharged for further processing. The resulting powder contains 2% - 4% moisture and consists of free-flowing, non-dusty particles. Spray drying is followed by a step to form the powder into coarser particles that will dissolve more completely in the consumer's cup.

The agglomeration process: Instant tea, basically involves rewetting the surfaces of the tea powder particles and bringing the particles into contact, so that they will adhere to each other and form larger, more granular particles. This is accomplished by exposing the powder to steam or a fine mist, while tumbling it in air at a temperature, and as 8O⁰C.

A flow sheet of the process is shown hereinbelow:

Claims

We Claim;

1. A process for the preparation of instant tea which retains the flavour and aroma of freshly brewed tea comprising the steps of:

(i) extraction in a plurality of columns of a mixture of tea leaves in two immiscible solvents of different polarities to obtain a decoction,

(ii) filtering the decoction and then subjecting it to the step of spray drying to obtain a powder,

(iii) subjecting the powder to the step of agglomeration.

2. A process as claimed in claim 1 wherein the two solvents are water and cyclodextrins such as alpha beta and gamma cyclodextrins, the organic solvent being added in the last column. The ratio of tea leaves to solvent being between 1 :4 to 1:6.

3. A process as claimed in claim 1 wherein the mixture is heated to a temperature in the column is maintained between 50 to 8O⁰C, the

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temperature at the first stage being between 50 to 6O⁰C₅ at the second stage upto 8O⁰C and at the third stage being brought down to between 70 to 75⁰C.

4. A process as claimed in claim 1 wherein the mixture has a pH of 3.6 to 6.5.

5. A process as claimed in claim 1 wherein the period of intraction between 8 to 14 minutes.

6. A process as claimed in claim 1 wherein the extraction of total solids is 22 to 34%.

7. A process as claimed in claim 2 wherein 1% of cyclodextrin is added to the mixture.

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