Food or edible material: processes – compositions – and products – Processes – Extraction utilizing liquid as extracting medium
Reexamination Certificate
2000-02-15
2002-07-30
Weier, Anthony J. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Extraction utilizing liquid as extracting medium
C426S597000, C426S263000, C426S471000, C426S495000
Reexamination Certificate
active
06426106
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for making tea products, specifically extracts and powders, that are soluble in both hot and cold water.
BACKGROUND OF THE INVENTION
Leaf tea may be prepared as green leaf tea or black leaf tea. The method of preparing such teas is well-known to those skilled in the art. Generally, to prepare black leaf tea, fresh green leaves are withered (subjected to mild drying), comminuted, fermented (in which process enzymes in the tea leaf use atmospheric oxygen to oxidise various substrates to produce brown-coloured products) and then fired (to dry the tea leaves). Green leaf tea is not exposed to the fermentation and firing processes. Partial fermentation may be used to produce intermediate-type teas known as “oolong” tea.
When hot aqueous infusions of black leaf tea are prepared, it is found that the infusion comprises substances which are insoluble in cold water, which substances therefore tend to precipitate as the infusion cools. These cold water insoluble substances comprise tannin complexes (known as tea “cream”) and typically comprise from 15-35% of the total tea solids in the infusion.
Black leaf tea infusions may be used to produce “instant” teas and other products which are preferably soluble in cold water. For this reason, it is known to separate the insoluble tea cream from the “decreamed” fraction (which is the term given to the cold water soluble materials after removal of the cold water insoluble cream). This is typically accomplished by centrifugation of the chilled (3-10° C.) extract. The insoluble cream fraction represents a significant proportion of the tea solids in the infusion. Accordingly, to prevent the cream fraction (which contains desirable flavour components) going to waste, it is known to treat the cream fraction, in one of a number of ways, so as to render it soluble in cold water and then to recombine the solubilised cream with the decreamed fraction. Various treatments of the cream fraction of tea infusions are described, for example, in GB 1,311,255, GB 1,461,726, U.S. Pat. Nos. 3,787,590, 4,156,024 and 5,827,560.
In contrast, less is known about treatment of whole tea infusions, without prior separation of the cream and decreamed fractions. Whole tea infusions differ substantially in terms of chemical composition relative to the separated cream portion.
United States patent specification U.S. Pat. No. 4,680,193 (Nestlé) discloses a process in which a whole black tea infusion, containing cold water insoluble substances, is mixed with catechins in order to solubilise the insoluble material.
European patent specification EP 0,067,351 (Nestlé) describes a process for making a powdered tea extract. The process involves making two aqueous extractions of black tea leaves: one at ambient temperature using an aqueous solution of a carboxylic acid and/or salt thereof; and a second extract using water at elevated temperature. Both extractions are performed at ambient pressure.
However, contrary to the prior art above the present inventors achieve oxidation of the whole tea solids without any pH modification or catalyst addition but solely through a combination of high pressure processing and an optimised oxygen transfer rate. That is significant as the incomplete removal of pH modifying substances and catalysts cause contamination.
It is an object of the present invention to provide a method for making a cold water soluble black tea product from a whole black tea infusion.
SUMMARY OF THE INVENTION
In a first aspect the invention can be said in broad terms to relate to a method for making a cold water soluble black tea extract, the method comprising the steps of (a) extracting tea solids from black tea leaves using an extraction liquid to provide a whole tea extract; (b) oxidising said whole tea extract under superatmospheric pressure and at a temperature above 60° C. to provide a cold water soluble liquor; (c) cooling said cold water soluble liquor to precipitate any residual cold water insoluble material; and (d) separating said residual cold water insoluble material from said cold water soluble liquor to give the cold water soluble black tea extract.
In a second aspect the invention can be said in broad terms to relate to a method for making a cold water soluble black tea powder, the method comprising the steps of (a) extracting tea solids from black tea leaves using an extraction liquid to provide a whole tea extract; (b) oxidising said whole tea extract under superatmospheric pressure and at a temperature above 60° C. to provide a cold water soluble liquor; (c) cooling said cold water soluble liquor to precipitate any residual cold water insoluble material; (d) separating said residual cold water insoluble material from said cold water soluble liquor to give the cold water soluble black tea extract; and (e) drying the cold water soluble black tea extract to form the cold water soluble black tea powder.
Preferably the oxygen transfer rate is between 8 and 50 hr
−1
, more preferably between 15 and 35 hr
−1
. The oxygen can be provided as a component of air.
Beverages made from these tea powders have good clarity and favourable flavour and colour.
“Tea” for the purposes of the present invention means leaf material from
Camellia sinensis
var.
sinensis
or
Camellia sinensis
var.
assamica.
“Tea” is also intended to include the product of blending two or more of any of these teas.
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.
Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts or concentrations of material ought to be understood as modified by the word “about”.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a method for making a cold water soluble black tea extract or powder. The method involves extracting tea solids from black tea leaves using an extraction liquid to provide a whole tea extract and oxidising the whole tea extract, as opposed to solely the insoluble cream fraction or the soluble decreamed fraction, under superatmospheric pressure and at a temperature above 60° C. This gives a cold water soluble liquor. Further method steps involve cooling the cold water soluble liquor to precipitate any residual cold water insoluble material, and separating the residual cold water insoluble material from the cold water soluble liquor to give the cold water soluble black tea extract.
The inventors have found that the temperature and pressure are preferably those at which distilled water would have at equilibrium a maximum capacity for dissolved oxygen of at least 0.5 grams per liter. It is also preferred the oxygen transfer rate is such that the tea solids are oxidised in the absence of a catalyst or any pH modification step.
It will be appreciated by those skilled in the art that, at the temperatures indicated above, the cold water insoluble tea solids will be generally soluble, such that where the method is applied to an aqueous extract prepared from black tea leaves, the aqueous mixture will be substantially a solution. The aqueous mixture will conveniently be an aqueous whole black tea extract, comprising cold water soluble tea materials as well as the insoluble materials.
The maximum obtainable concentration of dissolved oxygen in distilled water under given conditions of temperature and pressure can be readily determined by reference to standard texts. Thus Perry's Chemical Engineering Handbook (Perry & Green 1984, Sixth Edition p.3 103, McGraw Hill) gives the values for maximum solubility of oxygen in water at elevated pressure for temperatures up to 100° C. For temperatures in excess of 100° C., reference may be made to the paper by Pray et al., (1952 Industrial and Engineering Chemistry 44, 1146-1151). The maximum dissolved oxygen concentration obtainable at equilibrium under the same conditions in aqueous mixtures compr
Barrett Matthew John
Black Dominic P.
Leo William Joseph
Noble Ian
Richards Jeffrey Bryn
Lipton division of Conopco, Inc.
Weier Anthony J.
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