The present invention relates to a container suitable for containing a food or beverage that is provided with a thermochromic ink which indicates when the contents of the container is at an acceptable temperature for consumption.

Food and beverage products are commonly stored in containers such as metal cans to prevent or at least significantly restrict microbial spoilage prior to consumption. These generally contain baked beans, chicken soup, peaches or the like which are heat treated, canned, and stored for some months before being removed form the canned, cooked and consumed. Metal cans are also used to store soft drinks. They are best chilled before consuming.

Like soft drinks, some food and beverages are purchased by people "on the go" at railway stations, garage forecourts, airports or offices corridors. The decision is often one of impulse to satisfy an immediate need or desire. These products are often ambient stable for convenient storing and vending. However some products need to be stored or served at a particular temperature to be acceptable or indeed safe for consumption.

Thermochromic inks or paints are known. They have been applied to or incorporated within wrist watches (U.S. 5,430,692), fish lures (U.S. 5,222,320) and toys (U.S. 4,917,643). The colour change that occurs can be permanent or reversible.

U.S. patent specification 5,114,112 discloses a food service system wherein individual portions of pre-cooked food are supported on trays within moveable carts. Each cart contains a number of food trays that support a food dish which can be covered by an insulated dome that has a thermosensitive knob. The colour of the member indicates whether the food on the dish is still at a safe heating temperature.

U.S. patent specification 4,805,188 discloses a time-temperature indicator for closed vessels, such as pressure cookers and sterilizers, which has ready visibility around a 360° angle and can function as a lifting knob.

The present inventors have been faced with the problem of conveniently and cost effectively providing a container for a food or beverage which needs to be cooled or heated to a certain temperature for consumption with means which indicates to a potential consumer that the contents of the container is ready to be consumed.

They have solved that problem by applying a thermochromic ink to the container which reversibly indicates when the contents of the container has reached and still retains an acceptable temperature for consumption.

Metal cans that contain food or beverages can be too hot to handle comfortably. While insulating sleeves of foam and rubber are well known they can be bulky and unattractive. The present inventors have found that expanded polystyrene can provide excellent insulation even when only 100 microns in thickness.

The present invention relates to a container suitable for containing a food or beverage to which a thermochromic ink has been applied that indicates when the contents of the container has reached an acceptable temperature for consumption.

Preferably the ink undergoes a reversible colour change over a range of acceptable temperatures.

Preferably the container is insulated to enable a customer to handle it comfortably when the contents has reached a temperature within the acceptable temperature range.

The invention also relates to the use of a thermochromic ink to indicate that the contents of a container is at a temperature that is suitable for consumption, and the use of an expanded polystyrene as an insulating material for a food or beverage container.

The container of the present invention is one that is suitable for containing a food or beverage, particularly one that needs to be cooled or heated to a certain temperature for consumption. Aluminium cans such as those used to contain soft drinks are readily available at relatively low cost but one skilled in the art will appreciate that any number of container shapes, sizes or materials (eg steel or a mixture of steel and aluminium to name but a few) could be used. For present purposes the container will merely be described as a can.

The container could contain a wide variety of food and beverage products. Foods such as soups and sauces and beverages such as tea, coffee and chocolate are particularly suitable. The word "tea" is intended to include black, green, oolong, rooibos and mate tea. Naturally herbal and other plant and vegetable matter infusions could also be used. Both coffee and chocolate are available in various forms. Like tea, any coffee or chocolate beverage compositions could include sugar or some other sweetener, milk or some other whitener, cream or some other creamer, flavour, nutritional supplement etc.

The can is provided with a thermochromic ink which indicates when the contents of the container is at an acceptable temperature for consumption. Thermochromic inks are known and are commercially available.

The ink can be applied directly to the can by any art known means, for example by a flexographic or gravure printing process, or on to a sticker, label or other covering that extends over at least part of the external surface of the can.

The thermochromic ink could be applied to the entire outer surface of the can but is more cost effective and convenient to restrict the application to discrete areas. One skilled in the art would appreciate that the number and size of these areas could vary greatly but achieve essentially the same result. One might even incorporate the inked area or areas in a logo. The present inventors however prefer to apply the ink to small predetermined regions on an insulating material that covers at least the sides of the can.

The containers of the present invention may be stored in a heating or cooling cabinet at the point of sale. Some of the cans displayed may not be sold on a given day so they may be allowed to return to ambient temperature and reheated or cooled the following day. It is therefore an important (but not necessarily an essential) aspect of the present invention that the thermochromic colour change is reliably reversible or at least otherwise repeatable. The thermochromic ink must be formulated accordingly. The present inventors have found that THERMELION brand inks are suitable for this purpose, especially MSC 41229.

One could if desired apply two differently formulated thermochromic inks to a container such that one can undergo a reversible colour change while the only can only undergo a permanent colour change. In that way there will be a record as to whether a particular container has already been heated or cooled to a certain temperature.

In the preferred embodiment described above the thermochromic ink is capable of reversibly indicating that the contents of the can is at a temperature of between 45°C and 55°C and thus suitable for immediate consumption. The colour of the ink changes from blue at 45°C (or below) to red at 55°C (or higher). The cabinet is thermostatically controlled so that the contents of the can will not exceed the required heating temperature ie about 55°C.

In a first preferred embodiment of the present invention the container is an aluminium can that contains a tea, coffee or chocolate drink that is intended to be heated to and consumed at about 55°C. It can be uncomfortable for some people to handle a can having its contents at such a temperature. The present inventors have therefore provided an insulating sleeve. A number of insulating materials are commercially available but they are often too thick, unsightly or expensive to be suitable for the purpose. After much experimentation the present inventors found that expanded polystyrene is surprisingly suitable. The thickness of the material should be between 100 and 500 microns. Any less and the can may be too hot for some people, any more and the insulating effect is such that the thermochromic ink may need to be reformulated to give a true indication of the temperature of the contents of the can. The expanded polystyrene should preferably be between 150 and 300 microns thick, 160 microns being particularly preferred. One skilled in the art could determine suitable thicknesses where the contents of the can should be consumed at a higher or lower temperature.

In a second preferred embodiment a container of the present invention is intended to contain a food or beverage that is should be consumed when cold. More specially the contents of the container should be between 1°C and 5°C prior to consumption. The container is provided with a thermochromic ink that is capable of reversibly indicating when the contents of the container is between those temperatures. Such a container can be provided with insulation means as described above to minimise temperature gain and/or ensure that the can is comfortable not too cold to hold.

The invention will be now be described with reference to the following examples.

Containers of the present invention in the form of metal (aluminium) can were filled with a chocolate milk beverage. The beverage is a hot chocolate which can be stored at ambient temperature but is intended to be consumed at a temperature of about 55°C. The entire external surface of each can was sealed with expanded polystyrene for insulation. A thermochromic ink was applied to small regions of the sides of the cans. The ink is a THERMELION brand ink (specifically MSC 41229).

The cans were then placed in a heating cabinet. The colour of the ink changed from blue at about 45°C to red at about 55°C. When the cabinet was turned off the inks became blue again. The cycle was repeated to ensure the colour change was fully reversible.

Cans such as those used in Example 1 were heated to temperatures ranging from 40°C to 80°C and gripped tightly in the palm of the testers hand. The calliper of 160 microns was found to provide the desired insulation at 45°C to 55°C.