AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant(s): Alex Samoun Invention Title: A TEMPERATURE INDICATOR AND MILK FROTHING JUG The following statement is a full description of this invention, including the best method for performing it known to me/us: - 2 A TEMPERATURE INDICATOR AND MILK FROTHING JUG Field of the invention The present invention relates to a temperature 5 indicator and milk frothing jug incorporating such a temperature indicator. Background 10 Many people drink espresso-based coffee with milk or soy milk. For the purposes of this specification, the term "milk" will be taken to include all forms of milk (regardless of the fat content), and milk substitute products (such as soy, rice or banana milks). 15 For espresso-based coffee, the milk is usually heated so that the drink is served warm. The heating process can involve frothing the milk (which may also be referred to as steaming or foaming the milk), by injecting steam into 20 the milk. As milk is heated, sugars within the milk (including lactose) become more soluble, which increases its perceived sweetness. However, excessive temperature can result in the proteins within the milk denaturing, which makes the milk unpalatable. This is sometimes 25 referred to as "burning" the milk. To achieve optimal sweetness without burning the milk, it is desirable to heat the milk to a temperature that is just below the temperature at which the proteins 30 become unstable. It is known to use a thermometer that can clip on the side of the milk jug. This type of thermometer has a dial 2119902_1 (GHMattm) - 3 gauge and a probe that is partially immersed in the milk. Although effective, this type of thermometer can readily become very unhygienic, and can have health and safety issues if not cared for properly. 5 Summary of the invention The present invention provides a method of frothing milk, the method involving: a) providing a temperature indicator comprising a 10 substrate that is provided with a single thermochromic coating that has a first optical state at temperatures less than a predefined temperature and a second optical state at temperatures greater than or equal to the 15 predefined temperature, the predefined temperature being within the range of 55 0 C to 66 0 C; b) applying the temperature indicator to a milk frothing jug; 20 c) pouring milk into the jug; d) heating the milk by injecting steam; and e) ceasing heating milk when the thermochromic coating changes from from the first optical state to the second optical state. 25 The thermochromic coating may be provided over a portion or the entirety of the temperature indicator. In certain embodiments, the thermochromic coating is 30 configured to be opaque at temperatures less than the predefined temperature, and transparent at temperatures greater than or equal to the predefined temperature. Thus, in these embodiments the thermochromic coating reveals indicia beneath the coating when milk within the 35 jug is greater than or equal to the predefined temperature. The revealed indicia may include a message, symbol or the like.
- 3A The present invention also provides a temperature indicator for use in frothing milk comprising a substrate that is provided with a single thermochromic coating that has a first optical state at temperatures less than a 5 predefined temperature and a second optical state at temperatures greater than or equal to the predefined temperature, the predefined temperature being within the range of 55 0 C to 66 0 C; together with directions to: 10 a) apply the temperature indicator to a milk frothing jug; b) pour milk into the jug; c) heat the milk by injecting steam; and d) cease heating milk when the thermochromic 15 coating changes from from the first optical state to the second optical state. The present invention also provides a milk frothing jug bearing at least one temperature indicator on its outer 20 surface, the temperature indicator comprising a substrate that is provided with a single thermochromic coating that has a first optical state at temperatures less than a predefined temperature and a second optical state at temperatures greater than or equal to the predefined 25 temperature, the predefined temperature being within the range of 55 0 C to 66 0 C, whereby, in use, as milk is heated in the jug the coating indicates when the temperature of milk reaches the predefined temperature.
- 4 In some embodiments, the predefined temperature is 65 0 C. These embodiments are most suitable for use with cow's milk. 5 In some alternative embodiments, the predefined temperature is 58*C. These embodiments are most suitable for use with soy milk. The thermochromic coating may be any one of a paint, 10 ink or dye. The temperature indicator may include an acrylic solvent based resin to which the thermochromic coating is applied. 15 The present invention may also relate to a milk frothing jug bearing at least one temperature indicator as previously described on its outer surface. 20 The temperature indicator may be provided on a substrate that is adhered to the outer surface of the jug. In some embodiments, the temperature indicator may be in the form of a sticker. 25 The thermochromic coating may be provided over a portion or the entirety of the temperature indicator. 2433051_1 (GHMatters) 7/10/10 - 5 In certain embodiments, the thermochromic coating is configured to be opaque at temperatures less than the predefined temperature, and transparent at temperatures greater than or equal to the predefined temperature. 5 Thus, in these embodiments the thermochromic coating reveals indicia beneath the coating when milk within the jug is greater than or equal to the predefined temperature. The revealed indicia may include a message, symbol or the like. 10 In some embodiments, the predefined temperature is 65*C. These embodiments are most suitable for use with cow's milk. 15 In some alternative embodiments, the predefined temperature is 58 0 C. These embodiments are most suitable for use with soy milk. The thermochromic coating may be any one of a paint, 20 ink or dye. The temperature indicator may include an acrylic solvent based resin to which the thermochromic coating is applied. 25 The jug may include a handle, and a pouring spout diametrically opposite the handle. The temperature indicator may preferably be located between handle and the spout. In some embodiments, the jug has two temperature 30 indicator, one to each side of the handle. The present invention also provides a method of frothing milk, the method involving the steps of: 2119962_1 (GHMatters) - 6 a) providing a milk frothing jug bearing at least one temperature indicator on its outer surface, the temperature indicator as previously described b) pouring milk into the jug; 5 c) heating the milk by injecting steam; and d) ceasing heating the milk when the thermochromic coating changes its optical properties. In certain embodiments, the or each temperature 10 indicator is provided on a substrate that is adhered to the outer surface of the jug, and step (a) involves applying the or each temperature indicator on the outer surface of the jug. 15 Brief description of the drawings In order that the invention may be more easily understood, embodiments will now be described, by way of example only, in which: 20 Figure 1: is a side elevation view of a milk frothing jug with a temperature indicator in accordance with a first embodiment of the present invention; Figure 2: is a partial side elevation view of the 25 milk frothing jug of Figure 1, showing the temperature indicator in a first state; Figure 3: is a partial side elevation view of the milk frothing jug of Figure 1, showing the temperature indicator in a second state; 2433051_1 (GHMatters) 7/10/10 - 7 Figure 4: is a plan view of a temperature indicator in accordance with a .second embodiment of the present invention, showing the temperature indicator in a first state; 5 Figure 5: is a plan view of the temperature indicator of Figure 4, showing the temperature indicator in a second state; and Figure 6: is a flow diagram showing a method of frothing milk in accordance with a third 10 embodiment of the present invention. Detailed description Figures 1 to 3 show a milk frothing jug 10 with a 15 temperature indicator 12 on the outer surface of the jug 10. The temperature indicator 12 including a thermochromic coating that is configured to change optical properties at a predefined temperature within the range of 55 0 C to 66 0 C. Thus, when milk is heated in the jug the 20 coating indicates when the temperature of the milk reaches the predefined temperature. In this embodiment, the thermochromic coating is provided over a portion 14 of the indicator 12. The 25 thermochromic coating is configured to be opaque at temperatures less than the predefined temperature, and transparent at temperatures greater than or equal to the predefined temperature. 30 Figure 2 shows the temperature indicator 12 in a first state, in which contents of the jug are at a temperature that is less than the predefined temperature. The portion 14 is opaque, and in this embodiment is black. 2119962_1 (GHMacers) -8 Figure 3 shows the temperature indicator 12 in a second state, in which contents of the jug are at a temperature that is at least the predefined temperature. 5 The portion 14 is transparent and reveals indicia beneath the coating. In this embodiment, the indicia is a coloured symbol 16. The milk frothing jug 10 with the temperature 10 indicator 12 has several advantages. These include that the indicator 12 is affixed to the outer surface of the jug 10. This provides temperature indication without the indicator being in direct contact with the milk to be heated. Accordingly, the temperature indicator cannot 15 contaminate milk. The jug, including the temperature indicator, can be washed in commercial automatic dishwashers. This reduces the workload for staff in cleaning and preparing for serving. 20 The thermochromic coating changes its optical properties rapidly at the predefined temperature. Furthermore, milk frothing jugs are typically thin-walled vessels that are made of stainless steel. Stainless steel has a relatively high thermal conductivity. The 25 combination of a milk frothing jug with the temperature indicator results in fast and precise indication that milk in the jug has reached the predefined temperature. In contrast, traditional gauge and probe thermometers have a delay in registering the temperature of the milk. This 30 can result in milk being burned while the thermometer indicates that the milk is below the desired temperature. Furthermore, traditional thermometers require calibration. 2119982_1 (GHMatlers) - 9 In the embodiment illustrated in Figures 1 to 3, the temperature indicator.12 has a substrate that is adhered. to the outer surface of the jug 10. Thus, the temperature indicator is a sticker. 5 In this embodiment, the thermochromic coating is provided over the portion 14 the temperature indicator 12. As illustrated in Figures 4 and 5, the indicator includes a permanently displayed portion 18 (that is free of the 10 thermochromic coating), and the portion 14. The portion 18 contains information that desirably is always visible. This information may include product type (such as full cream milk, low fat milk, soy milk, etc.) to 15 assist minimizing confusion of the jug contents. Alternatively or additionally, the information in portion 18 may include brand information, such as trade marks etc. As described previously, when the contents of the jug 20 are at a temperature that is at least the predefined temperature, the thermochromic coating on portion 14 is transparent and reveals the coloured symbol 16. Where the milk to be heated in the jug is cow's milk, 25 the desired temperature to achieve maximum sweetness without burning the milk is 65*C. Thus, for cow's milk the predefined temperature at which the thermochromic coating changes its optical properties is 65*C. It will be appreciated that there is a gradual change in optical 30 properties over a short range of temperatures. Thus, the thermochromic coating may commence changing its optical properties at approximately 640C. 2119962_1 (GHMalters) - 10 Similarly.-where the milk to be heated. -i-n the jug is soy milk, the desired temperature to achieve maximum sweetness without burning the milk is 58*C. Thus, for soy 5 milk the predefined temperature at which the thermochromic coating changes its optical properties is 58 0 C. The thermochromic coating may be any one of a paint, ink or dye. The temperature indicator may include an 10 acrylic solvent based resin printed on the substrate, with the thermochromic coating applied onto the resin. As shown in Figure 1, the jug 10 includes a handle H, and a pouring spout S that is diametrically opposite the 15 handle H. In this embodiment, the temperature indicator 12 is located midway between handle H and the spout S. In addition, the temperature indicator is immediately adjacent the base of the jug 10. This has the advantage that the volume of milk within the jug 10 can be much less 20 than the total jug volume, and the temperature indicator 12 can still perform its required function. It will be appreciated that in some alternative embodiments, milk frothing jugs may be provided with two 25 temperature indicators, one to each side of the handle. This has the advantage of one of the two indicators being orientated towards the barista, regardless of whether they are a left-handed or right-handed operator. 30 Figures 4 and 5 show the front surface of a temperature indicator 212 in accordance with a second embodiment of the present invention. The temperature indicator 212 is specifically intended for use in 2119982_1 (GHMatters) - 11 connection with a milk frothing jug as described previously in connection with Figures: 1 to 3. The indi-cator has a substrate that, in use, is to be affixed to the outer surface of the jug. 5 A portion 214 of the indicator is provided with a thermochromic coating that is configured to change optical properties at a predefined temperature within the range of 55 0 C to 66 0 C. In Figures 4 and 5, the outer periphery of 10 the portion 214 is indicated by broken white lines. The thermochromic coating of portion 214 is configured to change optical properties at a predefined temperature within the range of 55 0 C to 66 0 C. Thus, when 15 milk is heated in a jug (to which the indicator 212 is affixed) the coating indicates when the temperature of the milk reaches the predefined temperature. In this embodiment, the thermochromic coating is 20 configured to be opaque at temperatures less than the predefined temperature, and transparent at temperatures greater than or equal to the predefined temperature. Figure 5 shows the temperature indicator 212 in a 25 second state that corresponds with contents of the jug being at a temperature that is at least the predefined temperature. The portion 214 is transparent and reveals indicia beneath the coating. In this embodiment, the indicia is a coloured symbol 216. 30 Figure 4 shows the temperature indicator 212 in a first state that corresponds with contents of the jug being at a temperature that is less than the predefined 2119962_1 (GHMatlers) - 12 temperature. The portion 214 is opaque and conceals the flouredd symbol 216. The indicator 212 includes a permanently displayed 5 portion 218 that is free of the thermochromic coating. The portion 218 contains information that desirably is always visible, as previously described in connection with Figures 1 to 3. In this particular embodiment, the information in portion 218 includes brand information, 10 such as trade marks etc. The rear surface (not shown) of the indicator 212 is provided with an adhesive for affixing the indicator 212 to a milk frothing jug. 15 When the indicator 212 is affixed to a jug, the jug together with the indicator, can be used on a commercial basis that involves high volume production and very regular washing in commercial dishwashers (including in 20 commercial caf6s and restaurants). The adhesive used on the indicator 212, once affixed to the jug, can withstand this treatment for a period of approximately 3 to 6 months without losing adhesion to the jug. Furthermore, the materials (such as inks, etc) used for the information 25 displayed on the indicator 212 (including the thermochromic coating in portion 214) can also withstand this treatment for a period of approximately 3 to 6 months without these materials breaking down. 30 The temperature indicator 212 may include an acrylic solvent based resin to which the thermochromic coating is applied. 2119962_1 (GHMatters) - 13 Figure 6 is a flow chart of a method of frothing milk in accordance with a third embodiment. The method 100 involves the steps of: * providing a milk frothing jug bearing at least one 5 temperature indicator on its outer surface. The temperature indicator includes a thermochromic coating that is configured to change optical properties at a predefined temperature within the range of 55 0 C to 66 0 C - step 102; 10 e pouring milk into the jug - step 104; e heating the milk by injecting steam - step 106; and * ceasing heating the milk when the thermochromic coating changes its optical properties - step 108. 15 In step 108, the barista will usually shut off the steam from the frothing wand. In embodiments in which the temperature indicator 12 is in the form of a sticker, step 102 can involve applying 20 the or each temperature indicator on the outer surface of the jug. It will be understood to persons skilled in the art of the invention that many modifications may be made 25 without departing from the spirit and scope of the invention. For example, in some embodiments, the thermochromic coating may change colours at the predetermined 30 temperature. In some other embodiments, the thermochromic coating may change from transparent to opaque at the predetermined temperature. 2119962_1 (GHMatters) - 14 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary 5 implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 2119962_1 (GHMatters)