Food or edible material: processes – compositions – and products – Fermentation processes – Of plant or plant derived material
Reexamination Certificate
1999-08-17
2001-07-03
Weier, Anthony J. (Department: 1761)
Food or edible material: processes, compositions, and products
Fermentation processes
Of plant or plant derived material
C426S445000, C426S447000, C426S597000
Reexamination Certificate
active
06254902
ABSTRACT:
The present invention relates to tea processing. More specifically, a method and apparatus for processing whole leaf tea by exploiting the thermodynamic properties of carbon dioxide as a means to initiate the fermentation reactions that occur in black tea manufacture.
BACKGROUND AND PRIOR ART
Leaf tea may be prepared as green leaf tea or black leaf tea. Generally, to prepare black leaf tea fresh green leaves of the plant
Camellia sinensis
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 process. Partial fermentation may be used to produce intermediate-type teas known as “Oolong” tea.
Conventional wisdom dictates that tea must be macerated in some way to liberate the fermentative enzymes and their substrates within the leaves. One can macerate tea in many ways but broadly speaking there are two main mechanised methods for doing this.
The first, called “orthodox manufacture”, involves rolling withered tea leaves as part of a standardised procedure including fermenting, firing and drying steps. So called “orthodox tea” is typically characterised by withered leaf portions that are aesthetically pleasing to many but produce lighter liquors due to less extensive fermentation.
The second method is the most popular of a number of non-orthodox methods that involves using a machine resembling a mangle that cuts, tears and curls tea leaves. The original machine was invented by W. McKercher in 1930 and is commonly referred to as a CTC (cut-tear-curl) machine. The finely cut product is known generically as “CTC tea” and is characterised by a fast infusion rate and strong colour. This method tends to produce tea that is more consistent and uniform in quality and than the orthodox method.
Both orthodox and CTC machines are often used in conjunction with a Rotorvane machine, which minces withered tea leaves. These methods and their history and role in tea manufacture are described in “Tea: Cultivation to Consumption” edited by K. C. Willson and M. N. Clifford, Chapman & Hall, 1992.
Generally speaking consumer preference for either orthodox or CTC tea is a matter of national or regional culture. In some countries the visual appearance and texture of leaf tea are both important indicators of quality, larger leaf particles being associated with higher quality. In Western markets tea is increasingly purchased in filter paper bags and the colour of the infused product tends to be more important.
Some consumers however want the best of both worlds; i.e. a leaf tea that looks and feels like orthodox processed tea but has the liquor characteristics of a fuller fermented CTC processed tea. Unfortunately there is no commercially available tea manufacturing equipment that can deliver such a leaf tea.
In response to those needs, the present inventors have developed a method for fermenting whole tea, a method for manufacturing a leaf tea that resembles orthodox processed tea but infuses like CTC processed tea, and an apparatus for processing leaf tea in accordance with predetermined qualities of visual appearance, texture, infusion rate and, of course, taste. This invention arose from their finding that fermentation can be initiated in whole leaf by impregnating it with liquid carbon dioxide and causing the carbon dioxide to sublime rapidly.
Expanding leaves with carbon dioxide or “CO
2
puffing” is a technique that is used within the tobacco industry to reduce the bulk density of the tobacco in cigarettes. It has also been used to improve the drying and rehydration properties of fruits and vegetables. The puffing process involves the release or expansion of a gas from within a product to either create an internal cell like structure or to expand and rupture an existing structure.
For example, U.S. Pat. No. 1,484,536 (Airco, Inc) discloses a process for puffing tobacco with CO
2
to increase its filling capacity.
U.S. Pat. No. 4,307,733 (Philip Morris) describes a method for expanding dried tobacco and various food products such as prunes, apricots, pears and raising by CO
2
puffing.
Tabeidie Z., Pane F. A. and Cornelius P. L. (1992) “
Puffing Potato Pieces with CO
2
” American Society of Agricultural Engineers, Vol 35 (6), pages 1935-1940 describes a method for increasing the bulk specific volume, volume ratio and rehydration ratio of dehydrated potato pieces by CO
2
puffing.
Saputra D., Pane F. A. and Cornelius P. L. (1991) “
Puffing Dehydrated Green Bell Peppers with Carbon Dioxide
” American Society of Agricultural Engineers, Vol 34 (2), pages 475-480 describes a method for increasing the bulk specific volume and rehydration ratio of green bell peppers by CO
2
puffing.
Stahl E., Rau G. and Carius W. (1986) “
Cracking and Puffing of Plant Material by CO
2
High Pressure Treatment
” Z. Lebensm. Untersuch Forsch, Vol 182, pages 33-35 discloses puffing linseed to increase its swelling index and puffing hibiscus flowers to extract acid and pigments more rapidly and completely.
The present inventors have found that one can initiate fermentation in whole tea leaves by developing a carbon dioxide puffing method.
STATEMENT OF THE INVENTION
In broad terms the present invention relates to a method for processing whole leaf tea comprising the steps of impregnating tea leaves with liquid carbon dioxide within a pressure vessel, depressurising the vessel at a rate that is sufficient to freeze the liquid carbon dioxide, applying sufficient heat to cause the frozen carbon dioxide to sublime and consequently initiate fermentation within the leaves, allowing the tea to ferment for a time that is sufficient to achieve desired liquor properties, and drying the fermented product to yield the whole leaf tea.
The invention also relates to a method for manufacturing a leaf tea that resembles orthodox processed tea but infuses like a CTC processed tea that comprises initiating fermentation of whole tea leaves by carbon dioxide puffing and terminating the fermentation when desired infusion properties have been achieved.
The invention further relates to an apparatus for processing whole leaf tea comprising a pressure vessel for holding whole tea leaves, means for supplying liquid carbon dioxide to the vessel, depressurising means for reducing the pressure within the vessel at a rate that is sufficient to freeze the liquid carbon dioxide, heating means for applying sufficient heat to cause the frozen carbon dioxide to sublime and consequently initiate fermentation within the leaves, and firing means for arresting the fermentation and drying the leaves.
The leaves may be withered, reduced in size or altered in shape at any stage between harvesting the tea leaves and arresting the fermentation.
“Tea” for the purposes of the present invention means leaf material from
Camellia sinensis
or
Camellia 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.
“Whole leaf tea” includes tea leaves that are substantially intact, that is leaves that have not been macerated whether that be comminuted by cutting etc, disrupted by rolling, or by some other means. It could conveniently include single leaves, a cluster of leaves or the traditional two leaves and a bud. Substantial leaf fragments that are otherwise unmacerated may well behave like intact leaves and thus for the purposes of this invention they should be considered as “whole leaf tea” too.
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, especiall
Hodges Rosalind Clare
Mawson Jonathan David
Farrell James J.
Lipton, a division of Conopco, Inc.
Weier Anthony J.
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