Improvements in the Preparation and Treatment of Extract of Tea.
Year: 1888

page_text: Date of Application, 16th Oct., 1888
Complete Specification Left, 12th July, 1889-Accepted, 17th Aug..
1889
PROVISIONAL SPECIFI
ATION.
Improvements in the Preparation and Treatment of Extract
of Tea.
We, GEORGE CHRISTOPHER, F.C.S., Consulting Chemist, of 6 Barrow Road,
Streatham Common, in the County of Surrey, and RALPH WINNINGTON LEFTWICH, M.D.,
Physician, The Limes, 167 Brixton Road, London, in the County of Surrey, do hereby
declare the nature of this invention to be as follows:-
In carrying out our invention we employ gelatine for the purpose of combining
with and neutralising the tannin, contained in extract of tea, whereby the said
extract is deprived of the well-known prejudicial action, due to tannin, which infusion
of tea exercises on the digestive powers of the human system.
The employment of gelatine in the preparation or treatment of extract of tea
for the purpose of the neutralisation of tannin is the general principle of our inven-
tion, and we have devised the following methods of putting this idea into practice.
In order to bring about the neutralisation of the tannin without removing it, we
take dry pulverised extract of tea, and mix it intimately with dry gelatine reduced
to as fine a state of subdivision as possible, employing such proportions as are found
most suitable for the particular kind of tea-extract taken. These proportions should
be such that on boiling water being poured on the mixture for the purpose of making
a beverage of ordinary strength, the mixture shall dissolve with the production of the
smallest possible quantity of insoluble matter, care being taken at the same time that
the beverage shall not be of a distinctly glutinous nature. In order to secure these
results it is advisable to employ the extract from some kind of tea which-while strong
in other respects-contains as little tannin as possible. With the employment of
extract from good black tea we have found that if we take two parts of extract to
one part of gelatine we have always got a very good result, but owing to the
variable proportion of tannin in tea it is manifest that the relative proportions of
gelatine and extract are subject to wide variation. With a suitable kind of tea-oxtract
on boiling water being poured upon the mixture, with stirring, we obtain a beverage
which is almost perfectly clear, and on standing yields only an insignificant deposit.
The larger the excess of gelatine employed above the quantity required merely to
combine with the tannin, the more perfectly will the tannate of gelatine be redissolved
or kept in solution but the greater the danger of the beverage assuming a glutinous
character, hence the gelatine should be employed in the minimum quantity
It is essential that the solution
sufficient to produce a satisfactory result.
should contain a distinct excess of gelatine, as shown on filtration by its giving a
precipitate with a solution of tannin and none with a solution of gelatine.
In order to secure a mixture of uniform colour, the gelatine may be coloured brown
with some harmless substance such as caramel, but this is not necessary if the gelatine
is ground sufficiently fine.
The mixture obtained as above should be preserved in boxes or bottles closed as air-
tight as practicable.
The mixed powder of tea-
We also prepare a lozenge in the following manner.
extract and gelatine described above is preferably mixed with a suitable quantity of
then subjected to
powdered loaf-sugar to make it palatable, and the whole
pressure, the thin cake thus obtained being stamped, sawn, or cut into lozenges or
tablets of the required shape and size. These are lastly packed in well-closed boxes
or bottles with, for example, powdered loaf-sugar to prevent adhesion. These
lozenges are very useful on occasions on which a feeling of fatigue or drowsiness
has to be resisted, since they possess a powerful stimulating effect on the nervous
system without necessitating the trouble and inconvenience of preparing a strong
infusion of tea, and also without any injurious action on the digestive system.
•

page_text: In order to render the gelatine more soluble and friable, it may be employed
in the form of a combination with fine loaf-sugar, prepared, for example,
in the following manner. The gelatine is dissolved in hot water, the sugar added
and allowed to dissolve, and the whole mixed together. This solution is then
evaporated to dryness, and the solid residue pulverised according to methods well
known to manufacturers of gelatine. The relative proportions of gelatine and sugar
depend upon the precise character and properties which it is desired that the final
mixture with tea-extract shall possess, but we have found that equal parts give a very
suitable compound. Instead of dissolving the gelatine, the aqueous solution formed
in the process of manufacture of this substance may be employed. This combination
of gelatine with sugar is more especially suited for the manufacture of the lozenges,
in consequence of the large amount of sugar which they must almost necessarily
contain; but we also find it very useful for simply mixing with the powdered extract,
owing to its being susceptible of finer grinding than is the case with gelatine itself.
If necessary, a little strong syrup may also be added to make the lozenges bind, and
with the same object the gelatine itself, or its combination with sugar, may be
employed in the form of a concentrated solution or jelly, no matter whether the
whole or a part of the gelatine taken is in this condition. The extract of tea also
may be in the form of a concentrated solution of syrupy liquid, but so concentrated
that on being added to the gelatine, or to the combination of gelatine and sugar, the
whole solidifies. In short in the manufacture of the lozenges care is taken so to
regulate the consistency of the ingredients that the final mixture is ultimately a solid,
although at a certain stage of preparation the mass may be more or less plastic in order
to admit of being moulded.
The tea-extract alluded to hereinbefore is prepared by evaporating an infusion of
tea to dryness (or, if rendered advisable by special circumstances, as alluded to
above, not quito to dryness) in a copper vacuum-pan at the lowest practicable
temperature, according to well-known methods. In order to prevent the possibility
of the contamination of the extract with copper, the pan and all its fittings are
heavily coated with tin wherever the infusion can come into contact with them.
The dry extract is ground in a mill constructed essentially like an ordinary corn-
mill, except that the bearings wherever they come into contact with the extract are
made of lignum vitæ or silver, since the extract is affected prejudicially by contact
with iron. For the same reason all mixing machinery and all implements and vessels
used are so made that contact with iron is avoided.
In order to prepare an extract of tea in which the tannin, in addition to being
neutralised by gelatine, is also removed as completely as possible, we proceed for
example in the following manner.
An infusion of tea is treated with gelatine in any suitable state or form in such
quantity as to precipitate the tannin as completely as possible, while neutralising
the whole of it. To attain this object, the gelatine must be added in much smaller
quantity than would be necessary if it were desired to keep the resulting tannate of
gelatine as completely as possible in solution, and we find that the best way of ascer-
taining when we have arrived at the proper point is to take a sample of the mixed
liquid, evaporate it very nearly to dryness over the water-bath, exhaust the residue
with boiling water, and test the filtered liquid with solutions of both tannin and
gelatine. With gelatine the precipitate should be no more than very trifling; with
tannin it should be slight, but quite distinct, and in any case decidedly greater than with
gelatine. We have found that for the treatment of the tannin in this way, one pound
of gelatine is a very suitable quantity for ten pounds of good black tea of average
quality but these proportions will necessarily vary according to the amount of tannin
contained in the tea.
The infusion, containing both the suspended and the dissolved tannate of gelatine is
now evaporated nearly to dryness in a vacuum-pan as hereinbefore described, water
run in, the whole mixed up, and the temperature of the mixture raised to about 135° F.
Under this treatment the tannate of gelatine forms a more or less continuous soft
elastic mass; and must be washed by being well kneaded under the surface of the

page_text: water. The tannate of gelatine and the liquor are now removed from the pan,
separated by filtration or otherwise (the temperature of the liquid being kept
about 135° F.), the taunate of gelatine washed repeatedly in fresh quantities of
warm water, and the washings added to the main portion of liquor. The liquor is
next evaporated in the cleansed vacuum-pan to complete dryness, the residue removed
and treated with water at 135° F., and the solution filtered clear from a little
undissolved tannate of gelatine. The infusion thus obtained is evaporated in the
vacuum-pan to dryness if a solid extract is desired, or more or less completely if the
object in view be to obtain the extract in the liquid form.
In these operations it is advisable not to allow the temperature of the liquor to
fall much below 135° F. or 130° F. since at any materially lower temperature
certain constituents of infusion of tea begin to separate out in the solid form; and
as prolonged exposure of tea-infusion even to so low a temperature as 130° F.
acts prejudicially upon its quality it is advisable to conduct the operations as
expeditiously as possible.
In consequence of the property which, during its formation in the solid state,
tannate of gelatine possesses of taking up colouring matter and probably other sub-
stances also from tea-infusion, the last process is more especially suitable for application
to tea containing a relatively small proportion of tannin.
The extract of tea prepared or treated according to any of the herein before described
methods may be mixed or combined with any suitable substance-such as sugar con-
densed milk &c.-that may be thought fit for the serving of special purposes.
Dated this 16th day of October 1888
W. P. THOMPSON & BOULT,
Agents.
COMPLETE SPECIFICATION.
Improvements in the Preparation and Treatment of Extract
of Tea.
We, GEORGE CHRISTOPHER, F.C.S., Consulting Chemist, of 6 Barrow Road,
Streatham Common, and RALPH WINNINGTON LEFTWICH, M.D., Physician, The
Limes 167 Brixton Road, London, both in the County of Surrey, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
In carrying out our invention we employ gelatine in the preparation or treatment
of extract of tea for the purpose of the neutralisation of tannin and the consequent
prevention of the well-known prejudicial action, due to tannin, which infusion of tea
exercises on the digestive powers of the human system; and we have devised the
following methods of effecting this purpose.
In order to bring about the neutralisation of the tannin without removing it we
take dry pulverised extract of tea and mix it intimately with dry gelatine reduced to
a fine state of subdivision or in such other form as to readily dissolve in hot water,
employing such proportions as are found most suitable for the particular kind of tea
extract taken. These proportions should be such that on nearly boiling water being
poured on the mixture for the purpose of making a beverage of ordinary strength,
the mixture shall dissolve with the production of the smallest possible quantity of
insoluble matter, care being taken at the same time that the beverage shall not be of
a distinctly glutinous nature. In order to secure these results it is advisable to
employ the extract from some kind of tea which-while strong in other respects-
contains as little tannin as possible.. With the employment of extract from good
black tea we have found that if we take two parts of extract to one part of gelatine
we have always got a very good result; but owing to the variable proportion of
tannin in tea it is manifest that the relative proportions of gelatine and extract are
subject to wide variation. With a suitable kind of tea extract on nearly boiling

page_text: water being poured upon the mixture, with stirring, we obtain a beverage which is
almost perfectly clear, and on standing yields only an insignificant deposit. The
larger the excess of gelatine employed above the quantity required merely to combine
with the tannin, the more perfectly will the tannate of gelatine be re-dissolved or
kept in solution, but the greater the danger of the beverage assuming a glutinous
character hence the gelatine should be employed in the minimum quantity sufficient
to produce a satisfactory result. It is essential that the solution should contain a
distinct excess of gelatine, as shown on filtration by its giving a precipitate with a
solution of tannin and none with a solution of gelatine.
In order to secure a mixture of uniform colour the gelatine may be coloured brown
with some harmless substance such as caramel but this is not necessary if the gelatine
is ground sufficiently fine.
The mixture obtained as above should be preserved in boxes or bottles closed as air-
tight as practicable.
Instead of being in the state of powder the mixture of gelatine and extract of tea
may be put up in the form of lozenges in the following manner :-
The mixed powder of tea-extract and gelatine described above is preferably mixed
with a suitable quantity of powdered loaf sugar to make it palatable and the whole is
then subjected to pressure and made up into lozenges according to well known methods.
The lozenges are lastly packed in well closed boxes or bottles with, for example,
powdered loaf sugar to prevent adhesion. These lozenges are very useful on occasions
on which a feeling of fatigue or drowsiness has to be resisted since they possess a
powerful stimulating effect on the nervous system without necessitating the trouble
and inconvenience of preparing a strong infusion of tea, and also without any injurious
action on the digestive system.
In order to render the gelatine more soluble and friable it may be employed in the
form of a combination with fine loaf-sugar prepared, for example, in the following
manner. The gelatine is dissolved in hot water, the sugar added and allowed to
dissolve, and the whole mixed together. This solution is then evaporated to dryness,
and the solid residue pulverised, according to methods well known to manufacturers
of gelatine. The relative proportions of gelatine and sugar depend upon the precise
character and properties which it is desired that the final mixture with tea-extract
shall possess, but we have found that equal parts give a very suitable compound.
Instead of dissolving the gelatine the aqueous solution formed in the process of manu-
facture of this substance may be employed.. This combination of gelatine with sugar
is more especially suited for the manufacture of the lozenges in consequence of the
large amount of sugar which they must almost necessarily contain; but we also find
it very useful for simply mixing with the powdered extract, owing to its being
susceptible of finer grinding than is the case with gelatine itself. If necessary a
little strong syrup may also be added to make the lozenges bind, and with the same
object the gelatine itself or its combination with sugar may be employed in the form
of a concentrated solution or jelly, no matter whether the whole or a part of the
gelatine taken is in this condition. The extract of tea also may be in the form of a
concentrated solution or syrupy liquid, but so concentrated that on being added to
the gelatine or to the combination of gelatine and sugar the whole solidifies.
short, in the manufacture of the lozenges care is taken so to regulate the con-
sistency of the ingredients that the final mixture is ultimately a solid, although at
a certain stage of preparation the mass may be more or less plastic in order to admit
of being moulded.
In
The tea-extract alluded to herein-before is prepared by evaporating an infusion of
tea to dryness (or, if rendered advisable by special circumstances, as alluded to above,
not quite to dryness) in a copper vacuum-pan at the lowest practicable temperature,
according to well-known methods. In order to prevent the possibility of the con-
tamination of the extract with copper, the pan and all its fittings are heavily coated
with tin wherever the infusion can come into contact with them.
The dry extract is ground in a mill constructed essentially like an ordinary corn-
mill, except that the bearings, wherever they come into contact with the extract, are

page_text: made of lignum vitæ or silver, since the extract is affected prejudicially by contact
with iron. For the same reason all mixing machinery and all implements and
vessels used are so made that contact with iron or steel is avoided or where this is
impracticable care is taken to keep the surfaces of the metal clean and bright.
In order to prepare an extract of tea in which the tannin in addition to being
neutralised by gelatine, is also removed as completely as possible we proceed, for
example, in the following manner. An infusion of tea at a temperature of about 150° F.
is treated with a solution of gelatine at the same temperature in such quantity as
to precipitate the tannin as completely as possible while neutralising the whole of
it. To attain this object, the gelatine must be added in much smaller quantity
than would be necessary if it were desired to keep the resulting tannate of
gelatine as completely as possible in solution, and we find that the best way of
ascertaining when we have arrived at the proper point is to take a sample of the
mixed liquid, evaporate it very nearly to dryness over the water-bath, exhaust the
residue with boiling water, and test the filtered liquid with solutions of both
tannin and gelatine. With gelatine there should either be no change at all or
merely a slight turbidity; with tannin there should be a slight, but quite distinct,
precipitate. We have found that for the treatment of the tannin in this way, one
pound of gelatine is a very suitable quantity for ten pounds of good black tea of average
quality; but these proportions will necessarily vary according to the amount of
tannin contained in the tea.
The infusion, containing both the suspended and the dissolved tannate of gelatine,
is now evaporated nearly to dryness in a vacuum-pan as herein before described, water
run in, the whole mixed up, and the temperature of the mixture raised to about 135° F.
Under this treatment the tannate of gelatine forms a more or less continuous, soft,
elastic mass, and must be washed by being well kneaded under the surface of the water.
The tannate of gelatine and the liquor are now removed from the pan, separated by
filtration or otherwise (the temperature of the liquid being kept at about 135° F.)
the tannate of gelatine washed repeatedly in fresh quantities of warm water, and the
washings added to the main portion of. liquor. The liquor is next evaporated in the
cleansed vacuum-pan to complete dryness, the residue removed and treated with
water at 135° F., and the solution filtered clear from a little undissolved tannate of
gelatine. The object of the repeated evaporation and treatment with water is as com-
pletely as possible to convert into the insoluble form and remove the tannate of gelatine
originally in the state of solution in the mixed infusion. The solution thus obtained
is evaporated in the vacuum-pan to dryness if a solid extract is desired, or more
or less completely if the object in view be to obtain the extract in the liquid
form.
Instead of being in solution the gelatine may be employed in the solid state in
the following manner. The requisite quantity of gelatine (varying according to cir-
cumstances, as herein before explained) is taken in some finely divided condition,
preferably in the state of powder, mixed with about ten times its weight of cold
water (we have found the temperature of 50° F. very suitable) and left for 24 hours
with occasional stirring. From the absorption of water the particles swell up con-
siderably but preserve their individuality. A sufficient quantity of cold water is
now added to enable the mixture to be stirred freely. In the meantime an infusion of
tea is prepared and allowed to cool. This is now mixed with the gelatine mixture and
left with frequent stirring for about 48 hours or for as long a period as is safe in view
of the liability of tea-infusion to become sour in warm weather. Under these cir-
cumstances the particles of gelatine take up the whole or nearly the whole of the
tannin in the infusion and much of the colouring matter, but remain individually
distinct. The infusion is now decanted or filtered off, and heated to about 145° F.
In the meantime the residual particles, consisting of tannate of gelatine together
with unchanged gelatine, are treated with water at such a temperature that the tem-
perature of the Dixture is about 145° F. This mixture is then added to the heated
infusion, and the whole well agitated. The unchanged gelatine dissolves, and

page_text: thoroughly saturates any tannin that may be left in the infusion. To ascertain
whether a sufficiency of gelatine has been employed a small portion of the infusion
is tested for tannin and gelatine in the manner already described. If enough has not
been used more must now be added in the form of a solution. Under the treatment
here specified the particles alluded to loose nearly the whole of the colouring matter
which they had taken up from the infusion in addition to the excess of gelatine which
they should contain, but individually remain quite distinct. They are filtered
off and the infusion is evaporated in the vacuum-pan in the manner herein-
before specified, the dissolved tannate of gelatine being removed in the manner
described.
The finely divided gelatine may also be added to the cold infusion of tea without
having been previously soaked but we prefer to soak the gelatine, since this accelerates
its action on the tannin in the infusion.
In all these operations in which a warm infusion of tea is dealt with it is advisable
not to allow the temperature of the liquor to fall much below 135° or 130° F., since
at any materially lower temperature certain constituents of infusion of tea begin to
separate out in the solid form; and, as prolonged exposure of tea-infusion even to so
low a temperature as 130° F. acts prejudicially upon its quality, it is advisable to con-
duct the operations as expeditiously as possible.
The extract of tea thus prepared practically free from tannin may be put up in the
form of lozenges according to methods generally similar to those described in con-
nection with the mixture of gelatine and ordinary extract of tea.
In consequence of the property which, during its formation in the solid state,
tannate of gelatine possesses of taking up colouring matter and probably other
substances also from tea-infusion, the last named processes are more especially suited
for application to tea containing a relatively small proportion of tannin.
An infusion of tea may also be treated with gelatine according to any of the herein-
before described methods, but in quantity not quite sufficient to neutralize the
whole of the tannin. The tannate of gelatine may then be separated more or less
completely by simple filtration, or by evaporating the liquid, treating the residue with
warm water, and then filtering substantially according to the methods described in
connection with the last named processes. Much less difficulty is experienced in
dealing with tannate of gelatine when it is in presence of a little free tannin than
when it is in contact with an excess of gelatine; but if this condition be observed
throughout, the tannin thus left untouched must either be allowed to remain
unchanged in the liquor and subsequently contaminate the extract obtained, or it
must be dealt with by means of some other agent than gelatine.
In any process involving the drying of the extract the extract may preferably instead
of being dried completely in the vacuum-pan be removed in a syrupy condition, trans-
ferred to a drying-room and dried according to well known methods.
The extract of tea prepared or treated in the manner set forth in this specification
may be mixed or combined with any suitable substance-such as sugar, condensed
milk, &c. that may be thought fit for the serving of special purposes.
In this specification and in the claims appended it should be understood that
by the word "extract" we mean a dry extract or a concentrated liquid extract,
from which by the addition of hot water a solution to serve as a beverage can
be made, and not the ordinary infusion produced by pouring hot water upon tea-leaves.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
:-
1. The employment of gelatine either alone or in combination with sugar or some
other substance in the preparation or treatment of extract of tea for the purpose of
the neutralisation of tannin.
2. The addition of dry gelatine in any form either alone or in combination with
some other substance to dry extract of tea for the purpose of neutralising the tannin
contained therein substantially as specified.

page_text: 3. The addition of gelatine either alone or in combination with some other substance
and either entirely in the solid state or entirely or partially in the liquid state to
extract of tea either entirely solid or entirely or partially liquid for the purpose of
producing a solid compound extract and neutralising the tannin present. substantially
as specified.
4. The neutralisation and more or less complete removal of the tannin naturally
present in tea extract by adding gelatine to an infusion of tea removing the tannate
of gelatine as completely as possible, and obtaining finally a solid or liquid extract
substantially as specified.
5. The partial neutralisation and partial removal of the taunin naturally present in
tea-extract by adding gelatine to an infusion of tea in insufficient quantity to
neutralise the whole of the tannin, removing the tannate of gelatine more or less com-
pletely and obtaining finally an infusion containing comparatively little tannin, and
ready for further treatment in any desired manner in order to obtain therefrom a
solid or liquid extract substantially as specified.
Dated this 11th day of July, 1900
GEORGE
CHRISTOPHER.
RALPH WINNINGTON LEFTWICH.
W. P. Thompson & Boult,
Agents for the Applicants.