Note: Descriptions are shown in the official language in which they were submitted.
110~809
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This invention relates to the preparation of
beverages containing gas in solution and is particularly
concerned with the formation, during such preparation, of a
head of froth on the beverage.
According to the present invention there is provided
a method of preparing and serving a beverage having a head of
froth which includes the steps of forming a sealed package
comprising a container selected from a bottle and a can in
which the beverage is sealed from atmosphere and has in
solution therewith nitrogen gas which is present in an amount
of at least 1.5% vols./vol. and preferably in the range 1.5
to 3.5~ vols./vol. and carbon dioxide gas which is present
in the range 0.8 to 1.8 vols./vol; opening the sealed
package and subjecting the beverage to vibration of at least
audio frequency from a source which is external to the
beverage to an extent and for a time sufficient to cause some
of said gas or gases to come out of solution and cause or
contribute to the formation of the head of froth.
By the phrase "sealed package" as used throughout
this Specification (which includes the appended claims) is
meant a container such as a bottle or can in which a
relatively small quantity of the beverage is sealed from
atmosphere (as compared with a bulk quantity container such
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as a beer keg) and by which the beverage may be transported,
shelf stored and dispensed into a drinking vessel by manual
pouring directly from the container,
By the phrase "excitation medium" as used throughout
this Specification ~which includes the appended claims) is
meant at least one of the following:
(a) vibration of at least audio fre~uency;
(b) gas flow through the beverage by injection
of such.gas into the beverage~ the source
of such flow being remote from the sealed
package;
The vibration mentioned at (a~ above is preferably ultrasonic.
The gas as mentioned in ~b) above can be carbon dioxide ox an
inert gas but is conveniently air which is injected under
pressure into the beverage....................................
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preferably applied to the beverage while it is in an open
topped vessel (having been manually poured into such vessel
after opening of the sealed package), it can however be
applied to the beverage while the latter is still in the
package but after such package has been unsealed. The
beverage is conveniently subjected to an excitation surface
while it is being poured from the container to a drinking
glass; for example, the beverage may be poured through a
quantity (typically 10 grams) of shattered polystyrene
granules which have been suitably supported while in the flow
of beverage (an appropriate support may consist of a suitably
constructed gauze cage containing the granules).
The present invention was primarily developed for use in the
preparation of a beverage in the form of a fermented liquor
such as beer, lager, ale or stout - however, the invention
is also applicable to the preparation of non-fermented
beverages having physico-chemical properties that can lead to
the formation of a beer-type head of froth.
It is well known to provide a sealed package in which the
beverage, be it either a fermented liquor or a "soft-drink"
contains gas in solution - the gas being present either as a
result of its injection into the beverage or as a result of
the final stages of fermentation which may be allowed, or be
intended, to take place in the sealed package. Hitherto the
gas in beverages in sealed packages has been wholly or
primarily of carbon dioxide so that upon opening of such a
sealed package and dispensing of its contents, the beverage
effervesces to form the head of froth as the carbon dioxide
comes out of solution. In such a known sealed package it is
usual that upon dispensing of the beverage the carbon dioxide
readily comes out of solution to form the head, usually
without the beverage having to be externally excited or
stimulated, for example by manual shaking of the package;
in accordance with the present invention however release of
the carbon dioxide from the beverage may be expedited by
subjecting the beverage to stimulation by an excitation
medium.
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In comparison with the dispensing of beverages from sealed
packages, the dispensing of a beverage, particularly stout
or beer, in draught form from a bulk container is usually
achieved by the application from an external supply of a
pressurized gas (which is usually carbon dioxide or a
mixture of carbon dioxide and nitrogen) to the bulk beverage.
Consequently the draught beverage when being dispensed can
contain nitrogen in solution as a mixture with carbon dioxide
(the latter being present at a lower level than is normally
encountered in that beverage when contained in a sealed
packageJ; this is considered to be most advantageous since
it enables a smaller size of bubble to be formed (in com-
parison with such bubble as would be formed by carbon dioxide
alone) without releasing too much gas. By reducing the bubble
size in the froth there becomes a relatively greater surface
area of surface active compounds and a greater density to the
froth so that perceived creaminess and persistance of tha
froth is relatively increased. This latter effect is
considered particularly advantageous for stout where it is
most desirable that the froth should persist and be of a
creamy or foamy nature in comparison with the light froth as
is conventionally provided on light beer or lager. To under-
stand the development of the aforementioned creamy or foamy
froth, it is first realised that a bubble forming part of
that froth can only survive in the stout if its internal
pressure is at least equal to the forces which are tending
to make it collapse - particularly hydrostatic pressure and
surface tension. The latter is inversely proportional to
the radius of the bubble so that the smaller the bubble the
greater must be its internal pressure to prevent it collap-
sing from surface tension. The maximum internal pressure
of the bubble is the sum of the pressures necessary to retain
the concentrations of the dissolved gases in solution -
consequently to decrease the bubble size the pressures of the
~5 dissolved gases must be increased accordingly with the effect
that more gas is dissolved. In the case of carbon dioxide
the amount of gas dissolved quickly rises to a point of
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producing an unmanageable amount of ~roth on the beverage.
For this reason the nitrogen (or other inert gas) is intro-
duced since it has a much lower solubility than carbon
dioxide and it thus becomes possible to obtain a significant
increase in the pressures of the dissolved gas without an
unacceptable increase in the volume of dissolved gases.
During the dispensing of draught beverage as aforementioned
containing nitrogen in solution (or other inert gas in
solution and possihly mixed with carbon dioxide as discussed
in our British Patent Specification No. 876,628) the beverage
is processed in a manner which Is particularly intended to
release the nitrogen and carbon dioxide from solution to
promote the formation of very small bubbles of nitrogen and
carbon dioxide which will form a creamy froth. Such pro-
cessing of the draught beverage to release the nitrogen and
carbon dioxide from solution is necessary to produce the very
small bubbles and assist the evolution of carbon dioxide.
Conventionally the nitrogen and carbon dioxide release and
the formation of very small enduring bubbles is achieved by
the draught beverage being subjected to cavitation as it
suffers a pressure drop in passing through an array of small
orifices in a plate located upstream or downstream of the
dispensing tap.
The presence of a particular gas in solution influences, to
a certain extent, the flavour characteristic of a beverage
when dispensed and the head of froth formed. This is
particularly true of stout where there is a major difference
in quality between stout with a carbon dioxide content above
2.0 vols./vol. of beer as dispensed from a sealed package
such as a can or bottle (where the head is predominantly
formed by release of carbon dioxide~ and similar stout
containing dissolved nitrogen and with a carbon dioxide
content in the range of 0.8 to 1.8 vols./vol. of beer when
dispensed in draught form from a keg pressurised with
nitrogen and carbon dioxide (where the head formation is
assisted by nitrogen release). For the avoidance of doubt
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110()809
the units "vols./vol." as used throughout this specification
are the number of volumes of gas which are dissolved in a
unit volume of the beverage, said volumes of gas being
determined at a pressure of 760 millimetres of mercury and
at a temperature of 15.6C. The aforementioned difference
in quality is particularly noticeable in the case of the
foam. In the latter - draught - case the foam is more
creamy which can be objectively measured by a high foam
density. It may be undesirable that it has not, until now,
been possible to produce from conventional sealed containers
such as bottles or cans a beverage with characteristics of
draught stout. The present invention was therefore developed
in an attempt to alleviate the aforementioned difficulty
whereby a customer purchasing a beverage dispensed from a
sealed package could expect such beverage to have substan-
tially the same flavour and appearance characteristics as if
that beverage had been dispensed in draught form from bulk
containers by carbon dioxide and~or nitrogen or other inert
gas under pressure.
In a preferred form of the present invention therefore stout
in a sealed package is charged with nitrogen (or other inert
gas) so that the nitrogen and carbon dioxide (the carbon
dioxide usually being at a lower level than is-normally encoun-
tered in wholly carbonated bottles or canned beverages and
typically in the range of 0.8 to 1.8 vols/vol. is caused to
come out of solution, at least in part to form or contribute
to the formation of, a head of froth on the stout as a
result of the stout being subjected to stimulation by an
excitation medium.
Embodiments of the present invention will now be described,
by way of example only, with reference to the accompanying
illustrative drawings, in which:-
Figure 1 shows how the beverage can be subjected to stimulationby ultrasonic vibration to form a head of froth;
Figure 2 is a cross section through an injector device by
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llOC~809
which a supersaturated liquid can be injected into the
beverage to provide the necessary stimulation for froth
formation;
Figure 3 illustrates the manner in which the device of
Figure 2 can be used;
Figure 4 shows use of a syringe device for achieving
stimulation of the beverage to provide froth formation.
Figure 5 shows an arrangement by which the beverage can be
subjected to an excitation surface to provide the necessary
stimulation for froth formation and,
Figure 6 illustrates a dispensing device for attachment to a
bottle so that during pouring of beverage therefrom the
beverage is subjected to an excitation surface.
Each of the examples discussed hereinafter for putting the
present invention into effect will be considered in relation
to the preparation and serving of stout from a sealed bottle
or can, such stout in the bottle or can having in solution
therewith a mixture of nitrogen and carbon dioxide, the former
being present typically in the range 1.5~ to 3.5~ vols./vol.
and the carbon dioxide being present at a considerably lower
level than the amount of carbon dioxide which would normally
be present in conventionally bottled or canned stout and
typically in the range of n . 8 to 1.8 vols./vol.
Referring to Figure 1, after opening of the bottle 1 (or can~
the stout is poured manually into a drinking glass 2 which is
preferably of the thin-walled type. The glass 2 and its
contents are located on a tray or platform 3 which forms part
of an ultrasonic transducer unit 4 which may be of conven-
tional form. Whilst on the tray 3 the glass and its contents
are subjected to ultrasonic vibration to an extent and for atime
sufficient to cause some of the nitrogen and carbon dioxide
to come out of solution from the stout to form a head of
creamy froth thereon (or to contribute to the formation of
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the head bearing in mind that a relativeIy small amount of
head may already be present on the stout created by the
carbon dioxide release or as a result of slight aeration
which may occur in the stout while it is being poured from
the bottle or can into the glass). A switch 5 is provided
on the unit 4 for controlling the ultrasonic vibration and
when the required head has been formed by the ultrasonic
vibration the stout is ready for consumption. To provide
efficient ultrasonic coupling between the glass 2 and the
tray 3, the tray may contain water within which the glass
stands.
As an alternative to subjecting the stout to ultrasonic
vibration on the tray 3 as above mentioned, by a further
method an ultrasonic probe (not shown) may be inserted into
the stout as poured into the glass 2 and energised therein
to cause the required head to form.
The injection device shown in Figure 2 comprises a cylindrical
tube 6 within which is axially slidable a piston 7. Attached
to the piston 7 is a piston rod 8 which slidably extends
through a cap 9 at the upper end of the tube. The piston 7
is biased downwardly towards a nozzle 10 at the lower end of
the tube by a helical spring 11 which reacts against the end
cap 9. The piston 7 can be axially withdrawn manually
against the biasing of spring 11 by a handle 12 on the piston
rod until the rod 8 engages a catch mechanism 13 which
retains the device in a "cocked" condition. In this latter
condition the piston 7 clears an aperture 14 which is located
in the tube 6 between the piston (when cocked) and the nozzle
10. The nozzle 10 has an outlet orifice 15 within which is
normally seated a ball valve member 16, furthermore the
periphery of the orifice 15 is provided with a circumferen-
tially spaced array of small grooves (not shown) so that when
the ball is seated in the orifice 15 small "cavitation"
channels are formed between the grooves and the surface of
the ball 16 and which channels communicate between the lower
inner chamber of the injection device and the outside of the
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nozzle.
To cause the head to form on the stout (as poured into the
glass 2) by the device shown in Fig. 2, the nozzle end and
part length of the tube 6 is inserted into the stout (while
the device is in a cocked condition) so that the aperture 14
remains clear of the stout (see Figure 3). The ball member
16 is lifted slightly from the orifice 15 (by static pressure
of the stout) and the lower chamber of the device partly
fills with the stout (which is regarded as a supersaturated
liquid). The catch mechanism 13 is released when the stout
levels in the tube 6 and in the glass 2 have equalised so
causing the piston 7 to be driven downwardly (as indicated
at 7' ln Figure 2) by the pressure of spring 11; consequently
the increased pressure on the stout in the injection device
urges the ball 16 on to its seating and displaces the stout
from the ejector device into the stout in the glass by way
of the cavitation channels. In passing through the cavitation
channels the stout is subjected to cavitation and gas therein
comes out of solution and this acts to initiate and encourage
evolution of the dissolved gases from the stout in the glass
by "seeding" the formation of further fine bubbles in the
stout (as discussed in British Patent Specification
No. 1,266,351~ to form the head.
The stout as poured into the glass 2 can be subjected to the
necessary excitation medium by use of a syringe device 17
shown in Figure 4. By one method of using the device 17, the
plunger 17a of the syringe is withdrawn with the nozzle 17_
in water so that the chamber of the device is filled with
water 18 and thereafter air is drawn into the chamber to
form an air bubble in the head space 19. The amount of
water involved will be negligible CsaY about 3 millilitres)
in comparison with the quantity of the stout in the glass.
The nozzle 17b is now inserted into the stout in the glass
and the water and air rapidly injected below the surface of
the stout. It is beIieved that the water has little or no
function in initiating the head formation on the stout and
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it is pressurised entry of the air into the stout which
seeds the formation of the fine bubbles to form the head
previously described; the water, however, conveniently
serves as a "plug" in the syringe which allows the air
bubble in the syringe to be compressed prior to its injection.
sy a further method of using the syringe device 17 the chamber
of the device is wholly filled with water and such water is
jetted under pressure onto the surface of the stout in the
glass 2 (that is with the nozzle 17_ above the surface of the
stout); the jet of water entrains air which is subsequently
injected along with the water jet, into the stout and the
injected air is sufficient to "seed" the formation of fine
bubbles to form the head as previously discussed.
By a still further method of using the syringe device 17,
the nozzle 17_ is dipped into the stout in the glass 2 and
stout is drawn under vacuum in to the syringe chamber - this
has the effect of subjecting the stout to cavitation as it
enters the syringe chamber through the nozzle and consequently
the stout in the chamber foams in t~e headspace of the syringe
chamber. The stout and foam are now injected from the syringe
back into the glass (while the nozzle 17_ is submerged in the
stout~ and the injection of such foam initiates and encourages
evolution of the dissolved gases by seeding to form the head
as previously discussed.
In each of the aforementioned examples of putting/the invention
into effect, the stout is subjected to the excitation medium
after it has been poured into and while it is in, the drinking
glass 2. If required each such method may be modified by
subjecting the stout to the excitation medium while it is still
in the bottle 1 or can (but after opening of such bottle or
can) so that the bottle or can along with its contents can be
subjected to ultrasonic vibration on a tray, an ultrasonic
probe can be inserted into the stout while it is still in the
bottle or can or the desired gas/foam/liquid can be injected
into the stout in the bottle or can to cause the aforementioned
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"seeding" effect on the stout. It is of course desirable
that sufficient headspace is provided in the can or bottle
to allow the creamy froth to begin to develop immediately
prior to pouring the beverage into the drinking glass.
By the present invention a head of creamy froth can be formed
on the stout derived from the bottle 1 by pouring such stout
over a surface which has nucleation sites capable of inducing
foaming and in the embodiment shown in Figure 5 the stout is
poured from the bottle over polystyrene granules 20 (which
are retained in a simple gauze container of strainer 21) and
into the glass 2. The granules 2Q are conveniently formed
by shattering a block of polystyrene in a mill and it is
believed to be the flow of stout over the nucleation sites
provided by the sharp peaks on the surface of such granules
which causes evolution of the gases in the stout to promote
the head formation. Figure 6 illustrates a dispensing
device 22 having a stopper portion 23 which engages within
the mouth of the bottle 1 of stout. Extending through the
body of the device 22 and into the bottle 1 are two tubes
24 and 25 of which tube 24 is for the admission of air into
the bottle during pouring of stout from the bottle through
tube 25. It will be noted that tube 24 enters deeper into
the bottle than tube 25 so the liquid pressure differential
will ensure the stout flows through the tube 25 rather than
through the tube 24.
Housed within the tube 25 are polystyrene granules 20 which
are retained in the tube by gauze caps 26 on the ends of the
tube; consequently as the stout is poured into the glass
through tube 25 it flows over the surface of granules 20 which
causes evolution of the gases in the stout and formation of
the head foam.
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