CONTAINER HAVING MEANS FOR FOAM PRODUCTION

Abstract: A drinks can containing a carbonated beverage such as beer having an insert (1) which is arranged to force a jet of gas through orifice (5) into the beverage when the can is opened in order to form a head of foam on the beverage. The beverage contains carbon dioxide at less than 0.85 vols/vol, and preferably about 0.65 vols/vol. The total pressure within the can is greater than 25 psig and preferably about 40 psig. These pressures and carbon dioxide contents provide a good head across a wide range of beverage temperatures.

Description: CONTAINER HAVING MEANS FOR FOAM PRODUCTION ---A************************************** 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 lubricated 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 they suffer from certain drawbacks. In particular, the temperature at which the beer is served has a dramatic effect on foam production. Beer packaged as described above is usually intended for consumption at around 4 β C, ie. directly from a domestic refrigerator. In order to achieve the ideal surge and head it has been found that a carbon dioxide content of around 1.0 vols/vol is necessary. Provided the beer has been kept in the refrigerator for a sufficient time to allow its temperature to drop to about 4 β C, an excellent surge and head are produced. However, if the beer is opened at a significantly higher temperature, eg. at room temperature (about 20 β C) excessive foam production results and foam may spray out of the container. To date, this drawback has been accepted and instructions are generally provided that the beer should be chilled before consumption. This is rather unsatisfactory because many beer drinkers, especially consumers of traditional draught ales (which is the type of beer most commonly packaged in this manner) prefer to drink their beer at a higher temperature. Of course, the need to refrigerate the beer before consumption may also prove to be inconvenient to those who have no strong preference regarding temperature, especially if the beer is to be consumed away from home. According to the invention there is provided 3. container holding a beverage and having means for promoting the production of foam, when the container is opened, wherein the beverage contains less than 0.85 vols/vol of carbon dioxide and the pressure in the container is greater than 25 psig at l β C. Thus, a container is provided in which the content of carbon dioxide gas is significantly lower than in the known systems. It has been found that such a container when filled with beer in the known manner provides satisfactory performance in terms of head and surge at temperatures varying from 4*C to 25°C. Thus, an adequate surge and head occur at the bottom of the temperature range, whilst excessive foam production does not occur at the higher temperatures. 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 lower carbon dioxide concentrations-provide better results still, and therefore preferably the carbon dioxide content is less than 0.80 vols/vol. Further improved results are found with a carbon dioxide content of less than 0.75 vols/vol, but less good, although still satisfactory results are found with a content of about 0.55 vols/vol, and therefore it is preferred to use a higher carbon dioxide content than this. It is believed that the ideal value lies within the range of 0.6 - 0.7 vols/vol and is ideally around 0.65 vols/vol. The total pressure inside the can also has an effect on the efficacy of the system and 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 surge and head are obtained if the total pressure within the container is increased to 30 psig and this is improved still further at 35 psig. However, if the overall pressure is too high, then there will be excessive foam production. Preferably, therefore, the pressure is less than 50 psig, and more preferably less than 45 psig at l β C. It is thought that the most effective value is around 40 psig (all pressures measured at 1*C) , which is the typical pressure within the known type of container, although in such an embodiment the carbon dioxide content is significantly lower than in the prior art. 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 40 psig (at l β C) and the carbon dioxide content is 0.65 to 0.7 vols/vol. It has been found that such a combination provides very good form and surge from 4 β C to 20 β C without excessive foam production at higher temperatures. 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 l 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 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 contents are provided such that the final total can pressure is 40 psig at l β C and the carbon dioxide content is 0.65 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 l-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 may then flow from the headspace into the insert 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 β 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 within the insert to be objected 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 differing gas contents. Table 1 gives the results: WARM POUR Pouring performance Pressure in can C0 2 4' 'C 20 β C psig at l β C (vols/vol) Foam Surge Foam Surge 34 0.5 fair very good fair very good 36 0.65 good very good good very good 40 0.71 very good very good very good very good 39 0.84 very good very good some overflow *40 1.00 very good very good overflow 45 0.96 very good very good much overflow 37 1.18 very good very good much overflow 54 0.67 very good very good overflow 55 0.84 very good very good much overflow The table illustrates the effect of carbon dioxide content and total pressure on the surge and head of the 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 performance of the containers is measured in terms of surge and head, rated from "fair", through "good" to "very good", and in the case of the 20 β C measurements the excessive foam produced is described as "some overflow", "overflow" or "much overflow" . It will be noted from this table that the best results are obtained for 0.71 vols/vol of carbon dioxide and a total pressure of 40 psig at l β C. However, other experiments have suggested that 0.65 vols/vol provides the best overall results. The typical prior art values are 40 psig and 1 vols/vol of carbon dioxide (marked by an asterisk in the table). It will be noted from the table that whilst this provides very good foam and surge at 4 β C, at 20 β C excessive foam is produced which leads to overflow. Higher values of total pressure or the carbon dioxide content still give good performance at 4 β C but lead to either overflow or much overflow at 20 β C. Overflow can be avoided using lower total pressure and carbon dioxide contents but it should be noted that at 0.65 vols/vol of carbon dioxide the foam produced at 4 β C and 20 β C is only good and at 0.5 vols/vol the foam quality has dropped to fair. Thus, the values employed in the above described embodiments provide the best performance so that a can produced in this manner produces very good foam and surge at 4 β C and 20 β C (and at intermediate temperatures) , without excessive foam at the higher temperatures. Thus, the contents of the can may be consumed direct from the refrigerator or at room temperature.

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 less than 0.85 vols/vol of carbon dioxide and the pressure in the container is greater than 25 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 is in permanent communication with the rest of the container. 4. A container as claimed in claim 1, 2 or 3, wherein the carbon dioxide content is less than 0.80 vols/vol. 5. A container as claimed in claim 4, wherein the carbon dioxide content is less than 0.75 vols/vol 6. A container as claimed in any preceding claim wherein the carbon dioxide content is greater than 0.55 vols/vol. 7. A container as claimed in claim 6, wherein the carbon dioxide content lies within the range of 0.6-0.7 vols/vol. 8. A container as claimed in any preceding claim wherein the total pressure is less than 50 psig. 9. A container as claimed in claim 8 wherein the total pressure is less than 45 psig. 10. A container as claimed in claim 9 wherein the total pressure is less than 40 psig. 11. A container as claimed in any preceding claim wherein the container of beverage is a can of beer.

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