SLUSH MAKING METHOD AND APPARATUS

Abstract: A slush-type consumable product is made by dissolving gas such as carbon dioxide in an aqueous liquid so as to pressurise it to a predetermined pressure at which it has a lowered freezing point. The pressurised aqueous liquid is cooled to its lowered freezing point so as to generate a first quantity of ice particles dispersed in the liquid. The product is dispensed through a tap so as to relieve the pressure in the aqueous liquid. This results in the production of a slush-type product having a greater quantity of ice particles substantially uniformly dispersed therein.

Description: SLUSH MAKING METHOD AND APPARATUS The present invention relates to an apparatus for the production of slush- type products, particularly slush-type products for human consumption. Reference herein to a "slush-type product" is to a product which comprises a substantially uniform dispersion of ice particles in water. US 3162323 discloses a system for storing and dispensing cooled carbonated beverages. In this system, water is pressurised, carbonated and cooled and (if required) a beverage flavour syrup is mixed with the water at the dispensing tap. The system can be operated at temperatures below 0°C without formation of ice in the water due to the pressure of C0 . When the pressure is released at the dispensing tap, an ice/water slush is dispensed from the tap. It is an object of the present invention in at least one aspect to provide an improved method for making slush-type products, said method being capable of (i) producing a greater proportion of ice relative to water in the product and/ or (ii) producing a slush-type product having an improved texture. According to a first aspect of the present invention there is provided a method of making a slush-type product, said method comprising the steps of:- (i) pressurising an aqueous liquid to a predetermined pressure; (ii) introducing a water-soluble gas under pressure into the aqueous liquid so as to cause said water-soluble gas to dissolve in the aqueous liquid; (iii) cooling the pressurised aqueous liquid to its lowered freezing point so as to generate a first quantity of ice particles dispersed in the pressurised aqueous liquid; and (iv) relieving the pressure in the aqueous liquid so as to produce a slush-type product having a second quantity of ice particles substantially uniformly dispersed therein, said second quantity being greater than said first quantity. It will be understood that the invention partly relies upon the fact that the freezing point of the pressurised aqueous liquid containing the dissolved gas is lowered relative to the freezing point of the unpressurised non-gas- containing aqueous liquid. References herein to "lowered freezing point" and "normal freezing point" should be construed accordingly. It is a combination of the quantity of dissolved gas and the level of pressurisation which determines by how much the freezing point is lowered. Advantageously, ice particles formed in step (iii) assist in the production of ice particles in step (iv) by acting as seed sites for the dissolved gas to come out of solution during step (iv). Step (i) may be before, during or as a result of step (ii). The water-soluble gas used in step (ii) is preferably selected from carbon dioxide and nitrous oxide. More preferably, step (i) is effected using the same gas as is used in step (ii), said gas most preferably being carbon dioxide. Preferably, at least step (iii) is effected in a flow path which extends between a reservoir from which aqueous liquid to be used in the method is supplied to a dispensing station where step (iv) is effected. Step (i) is preferably effected in the reservoir, but may be effected in the flow path. The aqueous liquid preferably comprises water and one or more components selected from the group consisting of sweeteners, flavouring agents, colouring agents, stabilisers and alcohol. It will be understood that the normal freezing point of the aqueous liquid (and hence to some extent the lowered freezing point) is dependent upon the nature of the aqueous liquid (e.g. alcohol content) and the amount of solid solute (e.g. sugar) dissolved therein. When one or more components are present in the aqueous liquid in addition to water, the ice particles formed in step (iii) are typically "soft" ice particles (i.e. they are smaller than and have a larger surface area to volume ratio than "hard" ice particles which are formed if the aqueous liquid is exclusively water). Advantageously, such soft ice particles result in the formation of further soft ice particles in step (iv). The resultant slush-type product has a soft sorbet-type texture which readily melts with a pleasant mouthfeel when consumed. Preferably, the first quantity of ice particles generated in step (iii) is a predetermined quantity. More preferably, said predetermined quantity is maintained at a substantially constant level before relieving the pressure in step (iv). It will be understood that, when the pressurised aqueous liquid is at its lowered freezing point, it will tend to freeze completely if this temperature is maintained, thereby blocking the flow path. Preferably, therefore, the method includes a step of thermodynamically balancing the energy supplied to and extracted from the aqueous liquid, whereby to substantially maintain the predetermined quantity of ice particles. According to a second aspect of the invention, there is provided an apparatus for the manufacture of a slush-type product, said apparatus comprising:- (i) cooling means arranged to cool a pressurised aqueous liquid containing dissolved gas to its freezing point; (ii) control means operably connected to the cooling means and arranged to maintain a thermodynamic balance in the aqueous liquid such that a first quantity of ice particles is produced in the pressurised aqueous liquid; and (iii) pressure-relief means arranged to receive, in use, cooled pressurised aqueous liquid containing dissolved gas and the first quantity of ice particles, and arranged to produce a pressure drop such as to form additional ice particles in the aqueous liquid. Preferably, the aqueous liquid is supplied to the cooling means at a substantially constant sub-ambient temperature (e.g. cellar temperature). The apparatus may include pre-cooling means whereby the aqueous liquid can be pre-cooled to a substantially constant temperature. Preferably, the apparatus includes a flow path along which aqueous liquid may flow from an aqueous liquid reservoir to the pressure-relief means. The aqueous liquid already containing the dissolved gas may be introduced into the flow path. However, the liquid may be introduced into the flow path without the dissolved gas, in which case the apparatus preferably includes means for introducing a water soluble gas into the aqueous liquid upstream of the cooling means. According to a third aspect of the present invention, there is provided an aqueous liquid composition formulated for use in the method of said first aspect or in the apparatus of said second aspect. In a fourth aspect, the present invention also resides in an aqueous liquid composition when used in the method of said first aspect or in the apparatus of said second aspect. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing which is a schematic representation of an apparatus in accordance with the present invention. Referring to Fig 1 , an apparatus comprises pipework 2 defining a flow path for an aqueous liquid having at one end a pressurised container 4 acting as a reservoir for the aqueous liquid and at an opposite end a pressure-relief valve 6 in the form of a bar-top dispensing tap, and intermediate these ends sequentially downstream, a carbonator 8, an aqueous-liquid flow sensor F1 , an aqueous-liquid temperature probe T1 , and a coolant housing 10 around a helical region 2a of the pipework 2. A region 2b of the pipework 2 extends from the helical region 2a of the pipework 2 to the pressure-relief valve 6. A CO2 cylinder 12 fitted with a pressure reducing set 13 is connected to the aqueous liquid container 4 via a pressure regulator 14, and directly to the carbonator 8. The container 4 and carbonator 8 are maintained at a steady sub-ambient temperature. The coolant housing 10 is equipped with a coolant stirrer 16 (other alternative means of agitation may also be used), a coolant heater unit 18 and a first coolant temperature probe T2. A primary coolant circuit P is defined by tubing 19 which extends between a coolant chiller unit 20 incorporating a coolant pump and an inlet 22 of a two-way valve 24. The tubing 19 continues from a first outlet 26 of the valve 24, is connected to an inlet 10a of the coolant housing 10, and extends from an outlet 10b of the coolant housing 10 around the region 2b of the pipework 2 to the pressure-relief valve 6. In the pressure- relief valve 6, the tubing 19 surrounds the aqueous liquid flow path. From the pressure-relief valve 6, the tubing 19 returns to the coolant chiller unit 20. A coolant flow sensor F2 is located downstream of the two-way valve 24 and a second coolant temperature probe T3 is located immediately upstream of the coolant housing inlet 10a. A coolant bypass B extends from a second outlet 28 of the two-way valve 24 and joins the primary cooling circuit P at a point on the tubing 19 immediately upstream of the coolant chiller unit 20. The coolant is a glycol-water mixture, although any coolant liquid having a freezing point lower than that of the lowered freezing point of the aqueous liquid to be dispensed may be used. The aqueous liquid and coolant flow sensors F1 ,F2, the aqueous liquid temperature probe T1 and the first and second coolant temperature probes T2,T3, the coolant heater unit 18 and the two-way valve 24 are all linked to a central control unit 30. A data link D connects the central control unit 30 to a control computer 32 which is capable of processing data received from the control unit 30. The coolant heater unit 18 and the two-way valve 24 are operably controlled by the computer 32 via the central control unit 30. In use, the aqueous liquid is fed into the flow path under CO2 pressure, a constant pressure being maintained in the container 4 by the pressure regulator 14. The aqueous liquid is carbonated by the carbonator 8 and the carbonated aqueous liquid passes along the flow path where its rate of flow and temperature are measured by the flow sensor F1 and temperature probe T1 respectively, before entering the helical region 2a of the pipework 2 within the coolant housing 10. The pressurised aqueous liquid (now containing dissolved CO2) is cooled to its lowered freezing point at which temperature it is maintained in the flow path up to the pressure-relief valve 6. The two-way valve 24 controls the rate of flow of the coolant from the coolant chiller unit 20 through the primary coolant circuit P. This rate of flow of coolant, as well as the coolant temperature entering the coolant housing 10 and the temperature of coolant within the coolant housing 10 is constantly monitored. The coolant stirrer 16 ensures that an even temperature is maintained throughout the coolant housing 10, and provides a steady flow of coolant across the helical region 2a of the pipework 2 within the coolant housing 10. The output from the temperature sensors T1 ,T2,T3 and the flow sensors F1,F2 is fed from the control unit 30 to the control computer 32 via the data link D. The control computer 32 is programmed to process the data and control the coolant heater unit 18 and two-way valve 24 according to the results of the thermal balance calculations. For example, by measuring the flow rate and temperature of the aqueous liquid flowing into the coolant housing 10 and knowing the thermal transfer characteristics of the system (e.g. the specific heat capacity of the aqueous liquid, the latent heat of crystallisation of ice and the thermal properties of the pipework 2), it is possible to add energy to the aqueous liquid via the coolant heater unit 18 while (optionally) reducing the flow of coolant through the coolant housing 10, or to extract energy from the aqueous liquid by increasing the flow of coolant through the coolant housing 10. Thus, an equilibrium of ice/aqueous liquid can be maintained regardless of the flow condition of aqueous liquid in the pipework 2. The control computer 32 may be programmed for aqueous liquids having different characteristics (e.g. different freezing points). Alternatively, the computer 32 and the control unit 30 can be replaced by an integrated circuit which is dedicated to one particular liquid (or liquids having sufficiently similar characteristics). The following Example demonstrates the use of the above described apparatus:- Example A beverage comprising 5.5% ABV alcohol and 11 % sugar and having a freezing point of -2.4°C is pre-cooled to 10°C and pre-pressurised to 1 .5 x 10 5 Pa in the container. CO2 is dissolved in the beverage (14g CO2 / I) in the carbonator in which the head pressure of CO2 gas is 6.9 x 10 5 Pa causing the freezing point of the beverage to be lowered to -2.6 °C. The pressure in the pipework 2 is maintained at 6.9 x 10 5 Pa which is sufficient to maintain the desired level of dissolved CO2 in the beverage. The coolant chiller is set to circulate coolant at -10°C. The control computer 32 is programmed to generate and maintain a dispersion of approximately 10% soft ice in beverage in the pipework 2 from the coolant housing 10 to the dispensing tap. On dispensing, a product having a uniform dispersion of approximately 80% soft ice in the beverage is obtained. In another embodiment (not shown), an alternative control system is used. The control unit 30 and control PC are replaced by an integrated circuit, and a timer is provided. When there is no flow in the system, the heater unit 18 is switched on and the coolant temperature in the coolant housing 10 is ramped at a predetermined rate to a predetermined upper value. When flow commences (as detected by the flow sensor), flow of coolant through the coolant housing 10 is increased so as to decrease the temperature in the coolant housing 10 at a predetermined rate to a predetermined lower temperature. For any given beverage, the upper and lower temperatures and the rates of change between them can be calculated so as to give a satisfactory slush-type product without blockage of the pipework 2. This embodiment may be further modified by omitting the coolant heater unit 18 and stirrer 16, the temperature of the coolant being raised or lowered in the coolant chiller unit 20. Further modifications to the system (not shown) include the provision of means for adding ingredients to the drink, either immediately prior to dispensing (in which case the additional ingredients will become mixed with the drink during dispensing) or after dispensing. In either case, the additional ingredients may be cooled, for example circulating them through the coolant housing so that they are at the same temperature as the drink itself. A metered dosing system may be used to ensure that the correct proportions of additional ingredients are added. Such an arrangement allows a neutral base liquid (e.g. containing only water, sugars and optionally alcohol) to be provided in the container. Flavouring, alcohol and other ingredients may be subsequently added as described above. It will be understood that this allows the apparatus to be used for dispensing more than one type of drink without the necessity of changing the container.

Claims: CLAIMS 1. A method of making a slush-type product, said method comprising the steps of:- (i) pressurising an aqueous liquid to a predetermined pressure; (ii) introducing a water-soluble gas under pressure into the aqueous liquid so as to cause said water-soluble gas to dissolve in the aqueous liquid; (iii) cooling the pressurised aqueous liquid to its lowered freezing point so as to generate a first quantity of ice particles dispersed in the pressurised aqueous liquid; and (iv) relieving the pressure in the aqueous liquid so as to produce a slush-type product having a second quantity of ice particles substantially uniformly dispersed therein, said second quantity being greater than said first quantity. 2. A method as claimed in claim 1 , wherein the ice particles formed in step (iii) are used to assist in the production of ice particles in step (iv) by acting as seed sites for the dissolved gas to come out of solution during step (iv). 3. A method as claimed in claim 1 or 2, wherein the water-soluble gas used in step (ii) is selected from carbon dioxide and nitrous oxide. 4. A method as claimed in claim 1 , 2 or 3, wherein step (i) is effected using the same gas as is used in step (ii). 5. A method as claimed in any preceding claim, wherein the gas is carbon dioxide 6. A method as claimed in any preceding claim, wherein at least step (iii) is effected in a flow path which extends between a reservoir (4) from which aqueous liquid to be used in the method is supplied to a dispensing station (6) where step (iv) is effected. 7. A method as claimed in claim 6, wherein step (i) is effected in the reservoir 4. 8. A method as claimed in any preceding claim, wherein the aqueous liquid comprises water and one or more components selected from the group consisting of sweeteners, flavouring agents, colouring agents, stabilisers and alcohol. 9. A method as claimed in any preceding claim, wherein the first quantity of ice particles generated in step (iii) is a predetermined quantity. 10. A method as claimed in claim 9, wherein said predetermined quantity is maintained at a substantially constant level before relieving the pressure in step (iv). 1 1. A method as claimed in any preceding claim, further including a step of thermodynamically balancing the energy supplied to and extracted from the aqueous liquid, whereby to substantially maintain the predetermined quantity of ice particles. 12. An apparatus for the manufacture of a slush-type product, said apparatus comprising:- (i) cooling means (10, 19, 20) arranged to cool a pressurised aqueous liquid containing dissolved gas to its freezing point; (ii) control means (F1 , F2, T1 , 12, T3, 18, 24, 30, D, 32) operably connected to the cooling means (10, 19, 20) and arranged to maintain a thermodynamic balance in the aqueous liquid such that a first quantity of ice particles is produced in the pressurised aqueous liquid; and (iii) pressure-relief means (6) arranged to receive, in use, cooled pressurised aqueous liquid containing dissolved gas and the first quantity of ice particles, and arranged to produce a pressure drop such as to form additional ice particles in the aqueous liquid. 13. An apparatus as claimed in claim 12, including pre-cooling means whereby the aqueous liquid can be pre-cooled to a substantially constant temperature. 14. An apparatus as claimed in claim 12 or 13, including a flow path (2) along which aqueous liquid can flow from an aqueous liquid reservoir (4) to the pressure-relief means (6). 15. An aqueous liquid composition formulated for use in the method of any one of claims 1 to 1 1 or in the apparatus of any one of claims 12 to 14. 16. An aqueous liquid composition when used in the method of any one of claims 1 to 1 1 or in the apparatus of any one of claims 12 to 14.

Inventors: JOHNSON AMANDA, PURDEY COLIN ROYSON, WOOD TIM MICHAEL, JOHNSON, AMANDA, PURDEY, COLIN, ROYSON, WOOD, TIM, MICHAEL
Applicants: JOHNSON AMANDA, PURDEY COLIN ROYSON, UNITED DISTILLERS & VINTNERS H, WOOD TIM MICHAEL, JOHNSON, AMANDA, PURDEY, COLIN, ROYSON, UNITED DISTILLERS & VINTNERS (HP) LIMITED, WOOD, TIM, MICHAEL
Application year: 1999
Main classification: A23G9
IPC codes: A23G9