Food or edible material: processes – compositions – and products – Processes – Extraction utilizing liquid as extracting medium
Reexamination Certificate
2000-03-29
2001-10-02
Weier, Anthony J. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Extraction utilizing liquid as extracting medium
C426S597000, C426S263000, C426S312000
Reexamination Certificate
active
06296887
ABSTRACT:
This invention relates to a process for the preparing cold water soluble tea concentrates that are suitable for making cold soluble instant tea.
BACKGROUND OF THE INVENTION
There is an increasing demand for ready to drink tea or iced tea and several methods for extracting the tea solids in concentrated form, and such that they are cold water soluble have been investigated.
Several attempts have been made to improve the cold water solubility of instant tea but they have not been fully successful. Cold water soluble instant tea was generally prepared by cooling a hot water extract of leaf tea, and separating the precipitated insoluble portions by filtration or centrifugation. The insoluble material, which is often referred to as the tea cream, is discarded and the clear extract is dried. This process entails a considerable loss in yield.
United States patent specification U.S. Pat. No. 5,827,560 (Nestec S. A.) discloses a continuous process for producing a cold water soluble tea extract. Tea solids are extracted from tea leaves using an extraction liquid to provide a tea extract that contains soluble tea solids and insoluble tannins. The insoluble tannins are separated from the tea extract by cooling the extract to below about 15° C., usually to about 5° C. to 10° C. (i.e. chill decreaming). The insoluble tannins are then oxidised and solubilised under raised temperature and pressure conditions to provide a solubilised tannin liquor. Ground green tea can be added to the tannin liquor prior to oxidation to assist the oxidation reaction. The solubilised tannin liquor is either returned to the extraction liquid during liquid extraction of tea solids or added to the tea extract after separation of the insoluble tannins. A tea extract that contains solubilised tea tannins is collected.
United States patent specification U.S. Pat. No. 3,163,539 (Standard Brands Incorporated, 1964) discloses an improved process for preparing cold soluble tea having acceptable flavour, aroma and colour. The process described involves preparing a water extract of tea leaf and treating the cold water insoluble constituents of the extract with sodium hydroxide, preferably in the presence of oxygen. This treatment may be done either after or without separation of these constituents from the cold water soluble part of the extract. Through this treatment the previously insoluble constituents are rendered cold water soluble. The resulting alkaline liquor is neutralised and the total tea liquor is concentrated by evaporation to produce instant tea. According to this disclosure oxygen plays an important role, along with alkali, in the solubilisation reaction and introducing air or pure oxygen can increase solubilisation.
Though by the process described in U.S. Pat. No. 3,163,539, alkali induced solubilisation is enhanced by introducing air into the extract, this may lead to excessive darkening of the extract. Solubilisation should therefore be achieved rapidly so as to prevent undue darkening of the colour of the extract. Moreover introduction of air or oxygen into the strongly alkaline mixture leads to increased foaming of the extract during solubilisation with alkali.
European patent specification EP 699393 A (Nestlé) discloses a process for recovering tea cream effectively by mixing the insoluble cream separated by chilling with spent black tea leaves or with green tea leaves and concentrating and drying the pooled hot water soluble and cold solubilised extracts. According to this process in order to improve the solubilisation, it is essential to separate the cream by chilling and then treat the same with spent tea leaves or green tea leaves.
It has now been found that it is possible to improve solubilisation of the tea solids without the use of alkali, acids etc. and without the process of cold decreaming. This process may be made more cost effective as it can avoid the process of chilling which involves the use of a refrigeration system. The extract thus produced has good clarity and has high levels of soluble tea solids.
STATEMENT OF THE INVENTION
The present invention relates to a process for preparing a tea concentrate that is suitable for making a cold soluble instant tea comprising the steps of:
(a) preparing an extract of tea leaves that contains insoluble tea solids and at least 5% soluble tea solids;
(b) treating said extract with air or oxygen at a temperature between room temperature and 100° C. for 1 to 120 minutes; while cell wall material from a vegetable source is mixed therein prior to or after said treatment with said air or oxygen; and
(c) filtering and concentrating the solubilised extract to yield the tea concentrate.
The extract is preferably treated with the air or oxygen at a temperature between 70 and 90° C.
The cell wall material is preferably selected from the group of agricultural products consisting of rice husk, sugarcane fiber, bagasse, saw dust, small wood chips, spent tea, and green tea and mixtures thereof.
Further advantages of this invention will be more apparent from the ensuing description. “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.
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 extract can be prepared by extracting tea leaves with water, preferably hot water (60-100° C.). The tea leaf material used may be selected from any of the known tea varieties of black, oolong and green tea, or blends thereof. But the use of black tea is preferred.
The extract will contain soluble tea solids, generally more than 5%, and insoluble tea solids. It can be concentrated if desired using any suitable art known means or process.
One could separate the soluble tea solids in the extract from the insoluble tea solids in the extract by chilling the extract and removing the tea cream that precipitates out but in doing so one would lose a significant amount of tea solids and thus reduce the obtainable yield. Furthermore, chilling requires the use of refrigeration equipment, which can be expensive, particularly when the ambient temperature is high.
The extract is treated with air or oxygen to oxidise it. This typically involves aerating the extract for 1 to 120 minutes, but an aeration time of 20 to 60 minutes is particularly preferred. The choice of aeration time influences the colour of the tea concentrate and beverages made from same. In essence a longer aeration provides darker colours. One can therefore adjust the aeration time in order to obtain the desired colour profile.
The extract should be aerated at or above ambient temperature, and preferably below 100° C. Aerating the extract at a temperature between 70 and 90° C. is particularly preferred. The choice of temperature can also influence the colour of the tea concentrate and beverages made therefrom.
The extract is preferably aerated and at normal atmospheric pressure. But, good results can obtained when aerating the extract at higher pressures of up to about 10 kg/cm
2
.
Cell wall material from a vegetable source is mixed with the extract prior to or preferably after the aeration step in order to induce cold water insolubility in the tea solids. The cell wall material may be selected from a range of agricultural products such as rice husk, sugarcane fiber or bagasse, saw dust, small wood chips, spent tea, green tea or mixtures thereof. These materials are preferably used at a level of 5-30% weight
Mehta Sheetal Sharadkumar
Sukumar Vijay
Virkar Prakash Dattatraya
Farrell James J.
Lipton division of Conopco, Inc.
Weier Anthony J.
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