GB2161601A - Determining the head- retaining properties of beer and other beverages - Google Patents

Abstract

In providing a measure of the head-retaining properties of beer or other head-forming beverage, a sample of the beverage is dispensed so that a head is formed on it. Light is directed along a path traversing both the head and the liquid beneath the head. The light falls on a photosensitive device which yields an electrical signal depending on the intensity of the light. When liquid first becomes visible through a gap or gaps in the collapsing head, the value of the signal is noted and constitutes a standard for the beverage. When the head-retaining properties of a further sample of the beverage is to be measured, the sample is dispensed under standard conditions; for example a given volume may be run from a container into a glass with opaque sides. Light is directed through the head and liquid as before, and the duration of the period that elapses before the electrical signal takes the standard value is taken as a measure of the head-retaining properties of the sample. Apparatus has a window 8 above the photosensitive device, and a knob 10 for setting the standard value. A clock is started by a button 13 when the sample is dispensed, and when the detector output and standard value are equal the clock displays the duration of the period on an LCD 14. <IMAGE>

Description

SPECIFICATION A method of and apparatus for determinng the head-retaining properties of beer and other beverages This invention relates to a method of and apparatus for determining the head-retaining properties of beer and other beverages.

It is desirable that when certain kinds of beer and other beverages are dispensed a layer of foam, such as is generally referred to as a head, should form on the beverage and that the head should have certain properties or characteristics that those who buy and drink the beverages find attractive. Among these attractive or desirable properties is a certain foam stability; in particular it has been found desirable for a recognizable head to remain or be retained for several minutes.

The head-retaining properties of any particular beer depend on a number of factors, and there is a requirement in the brewing industry for a reliable method of assessing the head-retaining properties (that is the stability of the foam constituting the head) that can be formed on samples of beers; use of such a method enables the effects of different factors to be assessed.

Various methods have been proposed hitherto but none of them has been particularly satisfactory. One reason for this is that none of those methods has involved procedures resembling the procedues normally used when beer is dispensed into a glass and then allowed to stand. In consequence the results obtained by those methods often fail to correlate well with the subjective impression of head-stability or head-retention gained by someone observing beer that has been dispensed in a normal manner. An aim of the present invention is therefore to provide an improved method. Another aim of the present invention is to provide apparatus for use in carrying out that method.

From a first aspect the present invention consists in a method for providing a measure of the head-retaining properties of beer or other head-forming beverage, in which method a head is formed on a sample of the beverage by following a predetermined procedure, light is directed along a path traversing both the head and liquid beneath the head and is detected by photosensitive means operative to generate a signal dependent on the intensity of light falling on it, and there is determined the duration of the period that occurs before the head has collapsed to an extent sufficient to allow the signal to reach a predetermined value, said duration constituting a measure of head-retaining properties of the beverage.

After the head has been formed it gradually and progressively starts to collapse, and during that process there comes a moment when part of the surface of the liquid beneath the head becomes visible through an opening in the head. In a preferred method said predetermined value of the signal is the value that occurs when a head on that kind of beverage has collapsed to an extent such that part of the surface of the liquid beverage first becomes visible through an opening in the head.

Said predetermined value of the signal may be determined by experiment with a sample of the liquid beverage.

From a second aspect the present invention consists in a method for providing a measure of the head-retaining properties of beer or other head-forming beverage, in which a head is formed on a first sample of the beverage, light is directed along a path both traversing the head and passing through liquid beverage beneath the head and is detected by photosensitive means operative to generate an electrical signal which is a function of the intensity of the light, determining the value of the signal at the instant when it is observed that liquid first becomes visible through a gap or gaps in the collapsing head, which value then constitutes a standard value for that beverage, the value depending on the attenuation of the light by that liquid beverage, and then dispensing at least one additional sample of the beverage under predetermined, standard conditions, so that a head is formed on the additional sample or on each additional sample, directing light along a path both traversing the head and passing through the liquid beneath the head of the additional sample or of each additional sample, as with the first sample, detecting that light, by photosensitive means operative to generate an electrical signal which is a function of the intensity of the light, as with the first sample, and determining the duration of the period that elapses between the time when the additional sample or each additional sample is dispensed and the time when the value of the associated electrical signal is equal to the standard value, the duration of the period being a measure of the head-retaining properties of the additional sample concerned.

From a third aspect the present invention consists in apparatus for use in carrying out a method according to either of the first and second aspects of the present invention, which apparatus comprises means for generating light for direction along a path traversing both the head and liquid beneath the head, photosensitive means operative to generate a signal dependent on the intensity of light that has followed said path falling on it, setting means for generating a standard signal of predetermined value, and comparator means for comparing said signals and operative to produce an output signal when the signals have a predetermined relationship.

The apparatus may include timing means which can operate while the head on a sample of the beverage collapses but which is caused by said output signal to yield a value of said duration. The timing means may, for example, be caused to display the value of said duration when the output signal occurs.

The setting means is preferably adjustable by the user and is preferably such that it can be set by the user to provide a standard signal of any desired value within a range of possible values.

An embodiment of the present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic elevation of apparatus for use in dispensing a sample of beverage, Figure 2 is a plan view of part of apparatus for use in detecting the intensity of light passing through a sample, and Figure 3 is a block circuit diagram of the apparatus shown in Figure 2.

Referring first to Figure 1, this shows an opentopped cylindrical vessel 1 with an outlet tube 2 at the bottom. A rotary on/off cock 3 is provided in the outlet tube 2. The vessel 1 is mounted, with its axis vertical, at a predetermined height above a horizontal base surface 4. A glass 5 stands on the surface 4 beneath the vessel. The glass is of standard shape and volume, but the outer surface of its side walls (but not of its base) is rendered opaque, as for example by having adhesive black tape applied to it.

In use a quantity of the beverage to be investigated is gently introduced into the vessel 1 so that substantially no head is formed on it in the vessel and so that decarbonation of the beverage should be kept to a minimum.

Sufficient beverage is introduced into the ves sel 1 to fill the vessel completely. If desired the temperature of the beverage is adjusted to a predetermined value, for example 8"C in the case of beers of the kind that are sold in cans and bottles and are relatively highly carbonated.

Before it is placed in position the glass 5 is thoroughly cleaned and is rinsed first with distilled water and then with the beverage under investigation. When it is in position below the vessel, on the surface 4, the cock 3 is rapidly opened to its maximum extent and a predetermined volume of beverage is allowed to run into the glass. The volume may, for example, be 125 ml. A line on the side of the vessel 1 may indicate the level of liquid remaining in the vessel when the predetermined volume has left the vessel. The cock 3 is rapidly closed when the predetermined volume of beverage has been dispensed into the glass 5. It will be normal for a head to be formed on the liquid in the glass and for successive samples of the same beverage, dispensed in a similar manner, to yield heads of closely similar properties.

After a sample of beverage has been dispensed in the manner described the glass 5 is immediately transferred to the apparatus shown in Figure 2. That apparatus comprises a casing 6 with a flat top 7 incorporating a circular transparent window 8 beneath which is disposed a photosensitive device of which the electrical properties vary with the intensity of the light falling on it. The diameter of the window 8 is the same as that of the base of the glass 5, or it may be slightly less. Also on the top 7 of the casing there are mounted an indicator lamp 8, a rotatable setting knob 10, having a flange 11 carrying a scale which cooperates with a fixed mark 12, a springloaded button 13 and an LCD 14.

Electrical components housed in the casing are shown in the block circuit diagram shown in Figure 3. The photosensitive device beneath the window 8 is indicated at 1 5. The output of the device 1 5 is fed to a comparator 1 6 which also receives a signal from a calibration circuit 1 7. The strength of the signal from the calibration circuit can be varied by rotation of the knob 10. The calibration circuit is also connected to the indicator lamp 9, which may conveniently be constituted by an LED. The output of the comparator 16 is fed to a clock control circuit 1 8 which determines what is displayed by the LCD 14. Contacts controlled by the button 1 3 are connected to the clock control circuit 18.

The apparatus shown in Figures 2 and 3 is first calibrated in the following manner. The casing 6 is disposed with its top 7 horizontal and with the window 8 at a predetermined distance below a lamp of predetermined brightness. For example the lamp may be an incandescent lamp rated at 60 watts, and the distance may be about 35 cm. The glass 5 containing a sample of beverage dispensed in such a manner that a head is formed on it is placed on the window 8. The sample may, if desired, be dispensed in the standard manner described above. The person carrying out the calibration watches the head on the beverage and notes the moment when a patch of liquid beverage first becomes visible through the collapsing head. The knob 10 is immediately rotated to a setting such that the indicator lamp becomes illuminated, but no further.

The setting is in fact principally dependent on the opacity and colour of the beverage. At this setting the signal from the photosensitive device 1 5 is equal to the signal from the calibration circuit 1 7.

Once the apparatus has been calibrated in this manner it can be used in determining the head-forming properties of other samples of the same beverage or of other beverages having the same opacity and colour. To this end a sample of the beverage under test is dispensed into a glass in the standard manner and is quickly placed on the window 8. At the same time the button 1 3 is depressed. This resets the LCD to zero and causes operation of the clock control circuit 1 8 to start. The head on the beverage then starts to collapse.At some moment the photosensitive device 1 5 will produce a signal equal to the signal from the calibration circuit 1 7. When this occurs the clock control circuit 1 8 stops operating and the LCD displays the time that has elapsed since the button 1 3 was depressed.

This time is then taken as a measure of the stability of the head or head-retaining property of the head.

The setting of the knob 10 may be noted so as to enable the knob to be turned to the same setting at some future time when other samples of the same beverage are to be tested. There is then no need to recalibrate the device.

It has been found by experiment that this method is able to produce reliable, reproducible results and that the head-stability or headretention measured by the method correlates well with personal, subjective assessments of head quality.

Claims (10)

1. A method for providing a measure of the head-retaining properties of beer or other head-forming beverage, in which method a head is formed on a sample of the beverage by following a predetermined procedure, light is directed along a path traversing both the head and liquid beneath the head and is detected by photosensitive means operative to generate a signal dependent on the intensity of light falling on it, and there is determined the duration of the period that occurs before the head has collapsed to an extent sufficient to allow the signal to reach a predetermined value, said duration constituting a measure of head-retaining properties of the beverage.

2. A method according to claim 1 in which said predetermined value of the signal is the value that occurs when a head on that kind of beverage has collapsed to an extent such that part of the surface of the liquid beverage first becomes visible through an opening in the head.

3. A method for providing a measure of the head-retaining properties of beer or other head-forming beverage, in which a head is formed on a first sample of the beverage, light is directed along a path both traversing the head and passing through liquid beverage beneath the head and is detected by photosensitive means operative to generate an electrical signal which is a function of the intensity of the light, determining the value of the signal at the instant when it is observed that liquid first becomes visible through a gap or gaps in the collapsing head, which value then constitutes a standard value for that beverage, the value depending on the attenuation of the light by that liquid beverage, and then dispensing at least one additional sample of the beverage under predetermined, standard conditions, so that a head is formed on the additional sample or on each additional sample, directing light along a path both traversing the head and passing through the liquid beneath the head of the additional sample or of each additional sample, as with the first sample, detecting that light, by photosensitive means operative to generate an electrical signal which is a function of the intensity of the light, as with the first sample, and determining the duration of the period that elapses between the time when the additional sample or each additional sample is dispensed and the time when the value of the associated electrical signal is equal to the standard value, the duration of the period being a measure of the headretaining properties of the additional sample concerned.

4. A method according to claim 3 in which the formation of said head on said first sample of the beverage is effected by dispensing the sample under said predetermined, standard conditions.

5. A method according to any one of the preceding claims in which light, in traversing the head and the liquid beneath the head, travels in a direction such that it passes through the head before it passes through the liquid.

6. A method for providing a measure of the quality of the head that can be formed on beer or other head-forming beverage, substantially as hereinbefore described with reference to the accompanying drawings.

7. Apparatus for use in carrying out a method according to any one of the preceding claims, comprising means for generating light for direction along a path traversing both the head and liquid beneath the head, photosensitive means operative to generate a signal dependent on the intensity of light that has followed said path falling on it, setting means for generating a standard signal of predetermined value, and comparator means for comparing said signals and operative to produce an output signal when the signals have a predetermined relationship.

8. Apparatus according to claim 7 which includes timing means which can operate while the head on a sample of the beverage collapses but which is caused by said output signal to yield a value of said duration.

9. Apparatus according to either of claims 7 and 8 in which the setting means can be set by the user to provide a standard signal of any desired value within a range of possible values.

10. Apparatus for use in carrying out a method according to any of claims 1 to 6, substantially as hereinbefore described with reference to the accompanying drawings.