CONTAINER HAVING MEANS FOR FOAM PRODUCTION

Abstract: A container for a beverage, more particularly lager, has means for producing foam when the container is opened. The beverage contains more than 1.3 vols/vol of CO2 (most preferably 1.47 vols/vol) and the pressure in the container is less than 35 psig at 1 DEG C (most preferably 30 psig).

Description: CONTAINER HAVING MEANS FOR FOAM PRODUCTION ****************************************** This invention relates to the production of foam and particularly, but not exclusively, to the production of a head of beer dispensed from bottles, cans and the like. In recent years there have been developed various systems for providing beverages, especially beers, in containers for home consumption which are designed to mimic as closely as possible draught beer dispensed from a cask. These systems generally comprise a container which has a chamber of pressurised gas, often formed in a discrete insert located within it, which communicates with the remaining part of the container via a small orifice. When the container is opened gas is forced through the orifice into the beverage as a jet. This causes gas to be liberated from the beverage as bubbles which create a "head" of foam on top of the beverage. Such a system is described in EP 0227213 in which a discrete insert is provided in the form of a short cylinder having an orifice in its side. Another example is WO 93/25452 where an insert in the form of an elongate tube is provided around the inside of the base of a conventional drinks can. The tube has an orifice about half way up its side and directed towards the middle of the can. During production, first the insert is put in place and then the can is filled with a beverage, such as beer. Filling is usually carried out at a low temperature, typically l-5 β C in order to prevent evolution of dissolved gas from the beverage. A head space is left at the top of the can to provide room for foam when the can is opened. The beverage normally contains carbon dioxide and may also contain nitrogen. It is also known to add liquid nitrogen or solid carbon dioxide (dry ice) to the container in order to increase the gas content. The amount of gas is critical to the taste of the product and affects the production of a "head" of foam. Next, the can is sealed and the pressure inside rises as a result of evolution of gas from the beverage. The increase in pressure forces beverage through the orifice and into the insert where it forms a reservoir at the lowest part and thereby compresses the gas which is trapped in the remainder of insert. Eventually, an equilibrium condition is reached, at which time the reservoir of beverage within the insert covers the orifice. It is possible to arrange for gas as well as beverage to be forced into the insert by inverting the can soon after it is sealed. In this way the orifice, instead of being submerged under the beverage, becomes located in the head space, and therefore gas, rather than beer is forced into the insert at this time. Varying the interval between sealing the can and inverting it changes the amount of beverage which is forced into the insert. When the can is opened in order to consume the beverage, the pressure in the main part of the container drops rapidly to atmospheric pressure. However, the pressure inside the insert is still at an increased pressure, and therefore there is a pressure differential across the orifice. This forces gas out of the insert through the orifice in the form of a jet. The jet causes gas to be evolved from solution, thereby providing a cloudy mass of bubbles which rise up through the beverage. This can be seen if the contents of the can are poured into a glass soon after it is opened and is known as "surge". When the bubbles reach the top of the liquid they form a head of foam. A strong surge of small bubbles producing a creamy head is regarded as a characteristic of a good draught beer and therefore when beer is provided in these known containers, which are intended to provide a draught-type product, consumers expect to find these qualities. Another known system is described in WO 91/07326. Again, a chamber is provided within an insert located within a can, but instead of having a simple orifice, a valve is provided which, when the can is opened, releases gas from the chamber into the beverage. This causes a surge and head in the manner already described. A different method of achieving the same objective is described in GB 2260747 in which a drinks can is provided containing a concertina-folded fibre sheet which traps bubbles and releases them when the can is opened. The systems described above provide a very good surge and head, but the arrangements discussed above are principally suitable for use with beers such as stout and bitter which contain a comparatively low amount of carbon dioxide gas. A major part of the beer market at the present time is for lagers and there is a clear demand for a system which will allow a canned larger to be produced which provides a good surge and head when poured. However, an important quality of a good lager is the "tingle" effect produced on the tongue when it is consumed. This is caused by dissolved carbon dioxide and in order to provide a good tingle it is necessary to provide a much higher level of this gas than is found in the systems used for stout and bitter. Unfortunately, simply using these systems to package beers such as lager is not successful because the high carbon dioxide content leads to excessive foaming. This may be so severe that foam overflows from the container when it is opened. One solution to this problem which has been proposed is to use an insert which has a substantially reduced internal volume compared to the known inserts. However, the need to use different types of insert for different beers will lead to higher production and handling costs than would be the case if a standard design of insert could be used. According to the invention there is provided a container holding a beverage and having means for promoting the production of foam when the container is opened, wherein the beverage contains more than 1.3 vols/vol of carbon dioxide and the pressure in the container is less than 35 psig at 1°C. Thus, a container is provided in which the content of carbon dioxide gas is significantly higher than is usual in the bitter and stout systems where a hollow insert is provided. This gives the beverage (eg. lager) the desired tingle. However, by reducing the overall pressure in the container from the typical 40 psig it has been found that the problems of excessive foam production are avoided even if a normal sized insert of the known type is employed. Thus, a system is provided by which lager can be packaged using known apparatus, so that when it is poured a good surge and head are produced, whilst preserving the distinctive tingle which the consumer expects from such a product. Although the invention may be employed in any container having means for promoting foam production it is most effective in those where a chamber is provided within the container from which gas flows when the container is opened. Although the chamber may be provided with a valve to provide communication between the chamber and the remainder of the container only when the container is opened, it is preferred that the chamber be in permanent communication, eg. via a small orifice. It has been found that even higher carbon dioxide concentrations provide better results, and therefore preferably the carbon dioxide content is more than 1.35 vols/vol. A further improved tingle is produced with a carbon dioxide content of more than 1.4 vols/vol and it is believed that the ideal value lies between 1.45 and 1.50 vols/vol, eg. 1.47 vols/vol. Whilst satisfactory results may be obtained with up to 1.55 or 1.6 vols/vol, carbon dioxide contents significantly higher than this are likely to lead to excessive foam production. The total pressure inside the can is important in order to produce a good pouring performance without excessive foam. It may be varied independently of carbon dioxide content by providing another gas such as nitrogen, as is known in the prior art. Thus, nitrogen may be dissolved in the beverage before filling the container or it may be added in liquid form. Other gases may be used, provided that they do not impair the flavour of the beverage. Improved results are obtained if the total pressure within the container is decreased to about 30 psig and it is believed that acceptable results are obtainable at pressures down to 20 psig. However, lower pressures, eg. 10 psig give poor pouring performance even if high carbon dioxide concentrations are used. However, it has been found that the most effective value is between 25 and 30 psig (all pressures measured at l β C) . Effective containers can be produced using any of these total pressures in combination with the various carbon dioxide contents, but in the most preferred embodiment of the invention the pressure in the container is 30 psig (at 1"C) and the carbon dioxide content is 1.47 psig. It has been found that such a combination provides very good foam and surge at typical lager drinking temperatures of around 4°C. It is thought that these carbon dioxide contents and pressures are applicable to all systems in which a chamber of gas is provided, whether as a discrete insert or integrally with the container. However, preferably the container is a drinks can holding beer and the chamber is in the form of a discrete insert. Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- Figure 1 is a side view of an insert, joined at either end to other inserts,* Figure 2 is a detailed section of the insert, showing the position of an orifice made at a later stage,* Figure 3 is a diagrammatic view of apparatus used to make inserts,* Figure 4 is a diagrammatic view of apparatus for preparing an insert for placing in a can; Figures 5a and 5b show later stages in preparing the insert,* Figure 6 shows the insert being positioned in a can,* Figure 7 shows the insert positioned at the bottom of the can; Figure 8 is a plan view of a sleeve for retaining the insert,* Figure 9 is a section through the sleeve; Figure 10 shows the sleeve in position over the insert,* Figure 11 shows an alternative embodiment; and Figure 12 shows a complete can with an insert in place,* in this figure the sleeve is omitted for reasons of clarity. The insert 1 shown in Figures 1 and 2 is in the form of an extruded tube of food grade HDPP. It has sealed regions 2 at either end where it is joined to other inserts, a plain middle region 3, and corrugated portions 4. The middle region 3 will be provided with an orifice 5 at a later stage, in its side. The insert is run in the form of an elongate, hollow, resilient tube which, once separated from the other inserts, can be bent to a desired configuration. As shown in Figure 3, the inserts are made by an extrusion technique. Plastics material 6 flows from an extruder over a mandrel to form a continuous tube. This passes into a chain of moving semi-cylindrical mould blocks 8. The top and bottom blocks co-operate to define a corrugated tube 9 which will form the inserts. The blocks are configured to provide the central region 3 for each insert, and a region 10 which will form the end regions 2 of the inserts. The blocks are moved along by a conveying system 11. A source of nitrogen is connected to a tube 12 which passes through the mandrel 7 into the tube 9. This pumps nitrogen at about atmospheric pressure through an orifice 13 to push the tube into the mould blocks 8. Suction may be provided also. The blocks pass through a cooling sleeve 14, to solidify the tube properly. After leaving the moulding phase, the tube passes to a sealing station where punches 15 - which may be heated - act upon the region 10 to define the end 2 of an insert and seal it. There are thus provided a series of sealed inserts, joined to each other and containing nitrogen. This series may be wound up on a drum for future use. The inserts are to be placed in a can of beer just prior to the can being filled. Figure 4 shows one stage in the preparation for this. An insert 1 is presented to a station where there is a receiving sleeve 16 and a cutter 17. The cutter severs the sealed region joining the insert 1 to the next insert, so that the insert is now free but is still fully sealed. A plunger 18 then pushes the insert laterally through an aperture 19 into the sleeve 16. The plunger 18 has a piercing point 20 which forms the orifice 5 as this is being done. The orifice 5 is about half way up the insert. Figure 5a shows the insert 1 within the sleeve 16. It will be noted that the ends 2 are projecting, which would make insertion in a can difficult. Accordingly, disposed around sleeve 16 for relative rotation is a sleeve 21. Rotation of this wipes the ends of the insert round, as shown in Figure 5b. At this point, the insert is ready to be placed in the can. This is shown in Figure 6, which illustrates a stage of insertion into a can 22. The insert 1 is within sleeves 16 and 21, and a piston 23 is also provided. When the assembly reached the bottom of can 22, the sleeves and piston are activated in an appropriate order to leave the insert at the bottom of the can. This is shown in Figure 7. The sleeves hold the insert in a compressed condition. The arrangement is such that the sleeves containing the insert may pass through a restricted opening into the can. As shown, the sleeves fit closely within the can. In some arrangements where the opening diameter is much smaller than the main can diameter, the sleeves will be spaced a greater distance from the can wall. The insert 1 springs out under its own resilience to engage the wall of the can 22, extending around the wall. It lies on the base of the can and has the form of a part annulus whose centre line is curved around the longitudinal axis of the can. The plane of the annulus is perpendicular to the axis of the can. The orifice 5 is directed inwardly to the centre of the can. Depending upon the length of the insert, it may form almost a complete annulus or may form e.g. a horseshoe shape. Figures 8 and 9 show a retaining sleeve 24 to assist in keeping the insert down at the base of the can. The sleeve is in the form of a resilient ring of food grade HDPP. It has castellations 25 around its top and bottom, and a plurality of inwardly projecting tabs 26 around the inside. The ring 24 can be squeezed into e.g. an oval to assist placing in the can. As shown in Figure 10, when the ring 24 is in position at the bottom of the can, the castellations 25 engage the wall of the can so as to resist dislodgement. The ring 24 keeps the insert 1 firmly in place. Figure 11 shows an alternative method for locating the insert. In this, a can 27 is provided with an inwardly directed circumferential ridge 28 under which the insert 1 is retained. The location of the insert 1 and locking ring 24 are performed quickly after the insert is pierced. Beer is then added quickly to the can to cover the insert and prevent excessive air (containing oxygen) getting into the insert. The beer contains carbon dioxide and may have been nitrogenated. Additionally, a portion of liquid nitrogen is added to the beer, once in the can in order to achieve the desired total pressure. As discussed previously, the quantity of carbon dioxide and nitrogen have an important effect on the performance of the container. The gas content is provided such that the final total can pressure is 30 psig at l β C and the carbon dioxide content of the beer is 1.47 vols/vol. The can is then sealed and the position is as shown in Figure 12 (where the retaining ring has been omitted) . A headspace of gas is provided above the beer. Filling takes place at a low temperature, say 1- 5 β C. Soon after the can has been sealed it is inverted and then heated. Inversion may take place after any convenient period following sealing. Gas will then flow into the insert from the headspace via the orifice 5 thereby increasing the pressure within the insert. Whilst in this inverted state the can is subjected to pasteurisation. It is heated to above 60 β C, say 63°C, and then allowed to cool to about 23 β C. It takes about 20 minutes for this process, after which the can is turned the right way up. When the can is eventually opened, e.g. by means of a ring pull 31, the main part of the can rapidly depressurises. However, the insert only communicates with the rest of the can via the orifice and therefore there is now a pressure differential across the orifice. This causes the compressed gas to be eject through the orifice 5. It is this which initiates significant bubble formation. The bubbles rise up through the beer as a surge and then form a creamy head on the surface of the beer. Experiments have been carried out to compare the embodiment just described with containers having different gas contents. Table 1 gives the results: Table 1 Pressure in C0 2 Pouring performance at Taste can psig at 4 β C I lβc Foam Surge ,0 1.45 poor poor good 24 1.45 very good good good 30 1.47 very good very good good 40 1.43 overflow good 40 1.01 very good very good too soft The table illustrates the effect of carbon dioxide content and total pressure on the taste, surge and head of lager-type beer when it is poured. The difference between the partial pressure produced by the carbon dioxide and the total pressure is made up by the presence of nitrogen. The can pressures quoted are measured at l β C when the can has reached equilibrium. The pouring performance of the containers is measured in terms of surge and head, rated from "poor", through "fair" and "good" to "very good", and excessive foam is "overflow". Taste of the beer is measured in terms of the tingle produced and is described as "good" or "too soft" . The last row on the table illustrates the result of using a container of the known type designed for use with bitter or stout in conjunction with lager and in which therefore uses typical gas contents for those beers. The foam and surge produced at 4 β C (a typical lager drinking temperature) are both very good, but the taste is too soft, ie. insufficient tingle. If a higher carbon dioxide pressure is used, eg. 1.43 vols/vol, in order to achieve a taste having a good tingle, whilst maintaining the total pressure at 40 psig, the result is an overflow of foam. Improved results are achieved by using a higher than normal carbon dioxide content whilst reducing the nitrogen content to give a lower total pressure. However, excessive reductions in total pressure (eg. to 10 psig) lead to poor pouring performance. Thus, the best results are achieved with 1.47 vols/vol of carbon dioxide and a total pressure of 30 psig. A can produced in this manner produces very good foam and surge without overflow whilst delivering a lager type beer with the desirable tingle taste.

Claims: Claims 1. A container holding a beverage and having means for promoting the production of foam when the container is opened, wherein the beverage contains more than 1.3 vols/vol of carbon dioxide and the pressure in the container is less than 35 psig at l β C. 2. A container as claimed in claim 1 wherein a chamber is provided within the container from which gas flows when the container is opened. 3. A container as claimed in claim 2 wherein the chamber and the remainder of the container are in permanent communication with each other. 4. A container as claimed in any preceding claim wherein the carbon dioxide content is more than 1.35 vols/vol. 5. A container as claimed in claim 4 having a carbon dioxide content of more than 1.4 vols/vol. 6. A container as claimed in claim 5 having a carbon dioxide content of between 1.45 and 1.50 vols/vol. 7. A container as claimed in claim 6 having a carbon dioxide content of 1.47 vols/vol. 8. A container as claimed in any preceding claim wherein the total pressure within the container is 30 psig. 9. A container as claimed in any of claims 1 to 6 wherein the total pressure in the container is between 20 and 30 psig. 10. A container as claimed in claim 8 wherein the total pressure is between 25 and 30 psig.

Inventors: ANDERSON RAYMOND GALE, ANDERSON, RAYMOND, GALE
Applicants: ANDERSON RAYMOND GALE, CARLSBERG TETLEY BREWING LTD, ANDERSON, RAYMOND, GALE, CARLSBERG-TETLEY BREWING LIMITED
Application year: 1995
Main classification: B65D79
IPC codes: B65D79, B65D85