Food or edible material: processes – compositions – and products – Fermentation processes – Of plant or plant derived material
Reexamination Certificate
2000-02-07
2002-11-19
Weier, Anthony J. (Department: 1761)
Food or edible material: processes, compositions, and products
Fermentation processes
Of plant or plant derived material
C426S262000, C426S597000
Reexamination Certificate
active
06482450
ABSTRACT:
The present invention relates to a method for manufacturing cold water infusing leaf tea. The method involves fermenting tannase pre-treated dhool (macerated tea leaves) under solid-state conditions in the presence of hydrogen peroxide. The dried leaf product infuses in cold water to give good flavour and colour.
BACKGROUND AND PRIOR ART
Black leaf tea is traditionally produced by oxidising and drying freshly plucked green tea leaves. Tea, the beverage, is generally prepared in Commonwealth countries by brewing these tea leaves in freshly boiled water for a few minutes and adding milk, and perhaps a little sugar. However in some countries, notably the United States (or more accurately, parts thereof) tea is more commonly enjoyed as an iced beverage.
Such a beverage cannot be prepared conveniently by infusing traditionally manufactured tea leaves in cold water. Instead, Americans either infuse the leaves in hot water, remove the leaves and place the infusion in a refrigerator until it is ready to consume or place tea leaves in cold water in sunlight to infuse slowly over a period of hours.
The numerous compounds in the leaves that give the beverage its unique organoleptical properties are only sparingly soluble in cold water. A more convenient option that has become available in the 1970's is the use of cold soluble tea-based powders.
There are numerous methods for making cold water soluble tea powders.
U.S. Pat. No. 4,051,264 (Lipton/Sanderson) discloses a method for making a cold water soluble leaf tea extract. Tea leaves are pre-treated with tannase under anaerobic conditions to generate a cold-water infusing tea with good colour, yield and flavour.
U.S. Pat. No. 3,812,266 (Sanderson/Coggon) discloses a method that involves converting green tea to black using tannase and natural tea enzymes. The method also includes a tannase pre-treatment step, but in a slurry system, followed by oxidation by natural tea enzymes to convert green tea into black, and generate tea powders, which are both hot and cold water soluble. In some examples hydrogen peroxide is added, to “shorten the process”. The proposed mechanism for enhanced cold-water soluble colour generation resulting from tannase-treatment (elevated epitheaflavic acid levels) is now known to be incorrect, and no mechanism was presented to explain the effect of adding the hydrogen peroxide.
European patent specification EP 760,213 A1 (Unilever) discloses a method of enhancing colour in a tea-based foodstuff. The method involves using a tannase pre-treatment (on leaf or extract) followed by treatment with exogenous peroxidase and hydrogen peroxide to generate cold-soluble colour.
International patent publication WO 97/40699 (Unilever) concerns tea processing with zeolites to generate colour. There are examples of adding zeolite following tannase treatment to generate cold-water soluble tea.
U.S. Pat. No. 4,639,375 (P&G, Tsai) discloses treating black tea with tannase, together with other cell-wall digesting enzymes, to generate cold-water soluble instant tea powders.
Convenient as cold water soluble tea powders can be, for many consumers the quality of the final beverage is not equal to that prepared from hot infused leaves. Other consumers prefer not to use powders as they perceive them to be artificial and therefore “unnatural”.
The present inventors have surprisingly found that it is possible to make a leaf tea that infuses in cold water to give a beverage with good colour and flavour that is as acceptable to consumers as a hot infused black leaf tea that has been refrigerated. Furthermore this product can be made by modifying the traditional black tea manufacturing process.
STATEMENT OF THE INVENTION
In broad terms the present invention relates to a method for preparing a cold water infusing leaf tea comprising the steps of macerating green tea leaves, treating the macerated leaves with tannase, fermenting the tannase-treated macerate in the presence of an amount of hydrogen peroxide that is sufficient to activate endogenous peroxidases, and drying the fermented leaf material to yield the cold water infusible leaf tea.
The invention also relates to a method for generating colour species in a cold water soluble tea product comprising adding hydrogen peroxide to a tannase-treated macerate of green tea in a quantity that is sufficient for the endogenous peroxidases to oxidise gallic acid liberated by the tannase treatment.
“Tea” for the purposes of the present invention means leaf material from
Camellia sinensis
var.
sinensis
or
Camellia sinensis
var.
assamica
. It also includes rooibos tea obtained from
Aspalathus linearis
however that is a poor source of endogenous fermenting enzymes. “Tea” is also intended to include the product of blending two or more of any of these teas.
“Leaf tea” for the purposes of this invention means a tea product that contains one or more tea origins in an uninfused form.
“Cold water soluble” for the purposes of this invention means giving good colour, flavour and mouthfeel in a short infusion time i.e. less than 10 minutes, but preferably less than 5 minutes at a temperature at or above 4° C.
The macerated leaves are preferably tannase treated under anaerobic conditions. The process is effective without this anaerobic incubation provided sufficient tannase is used. The tannase treated macerate is preferably fermented under standard conditions to produce elevated levels of theaflavins and gallic acid prior to the addition of hydrogen peroxide.
For the avoidance of doubt 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.
DETAILED DESCRIPTION OF THE INVENTION
Tea manufacture, especially black tea manufacture, traditionally comprises four basic steps: withering, rolling, fermenting and firing.
Withering is a process whereby the plucked tea leaves are stored for periods of time (perhaps up to 24 hours), during which they undergo various biochemical and physical changes which often includes a loss of moisture.
Maceration follows the withering step, and traditionally the withered leaves are optionally rolled to bruise and crush the leaves i.e. break down the plant tissue structure. This will have the effect of liberating fermentable substrates and fermenting enzymes from within the plant cells and tissue. Modern tea manufacture usually includes this step however the plant cells and tissue is broken down by passing tea, which has usually been withered, through a cutting machine.
The next step is commonly called fermentation but that is a misnomer. “Fermentation” is commonly used in the context of brewing alcohol to describe the action of exogenous enzymes. However in the tea world it is used to refer to the oxidative process that tea undergoes when certain endogenous enzymes and substrates are brought together by mechanical disruption of the cells by tearing or cutting the leaves. During this process colourless catechins in the leaves are converted to a complex mixture of yellow and orange to dark-brown substances and producing a large number of aromatic volatile compounds.
The colourful oxidation products include theaflavins and thearubigens. Theaflavins comprise several well-defined catechin condensation products that are characterised by their benzotropolone ring. Thearubigens are a group of undefined molecules with a large variance in molecular weight. They have a large variety of colours ranging from yellow to dark red and brown.
The fermented product is fired and dried to give a black leaf tea. The firing involves heating and drying the tea to destroy the fermenting enzymes and thereby arrest fermentation. It results in a reduction of moisture content to below 5%, and also leads to further chemical oxidation and changes in tea aroma. This generally involves exposing the tea to a blast of hot, dry air in a dryer.
The present invention relates to method for making cold soluble black leaf tea. The present inventors have found that this can be achieved by modifying some
Goodsall Christopher William
Jones Timothy Graham
Mitei Joseph Kipsiele
Parry Andrew David
Safford Richard
Lipton division of Conopco, Inc.
Squillante, Jr. Edward A.
Weier Anthony J.
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