Method and Apparatus for Partially Freezing an Aqueous Mixture

Abstract

A method for partially freezing an aqueous mixture comprising simultaneously or in either order the steps of: placing said aqueous mixture in contact with at least part of a freezing surface; cooling the freezing surface to below the freezing point of the aqueous mixture; so that ice forms at the freezing surface; and oscillating the freezing surface relative to the aqueous mixture in a direction that is not perpendicular to at least part of the freezing surface; characterised in that the oscillation is linear with a frequency of between 20 and 200 Hz.

1 . A method for partially freezing an aqueous mixture simultaneously or in either order the steps of: 
 placing said aqueous mixtures in contact with at least part of a freezing surface;    cooling said freezing surface to below the freezing point of said aqueous mixture; so that ice forms at the freezing surface; and    oscillating said freezing surface relative to said aqueous mixture in a direction that is not perpendicular to at least part of the freezing surface; characterized in that the oscillation is linear with a frequency of between 20 and 200 Hz.    
   
   
       2 . A method according to  claim 1  wherein the frequency of the oscillation is between 40 and 100 Hz.  
   
   
       3 . A method according to  claim 1  wherein the amplitude of the oscillation is between 0.2 mm and 20 mm.  
   
   
       4 . A method according to  claim 1  wherein the amplitude of the oscillation is between 4 mm and 10 mm.  
   
   
       5 . A method according to  claim 1  wherein the angle between the direction of oscillation and the majority of the freezing surface is less than 45°.  
   
   
       6 . A method according to  claim 1  wherein the freezing surface is the surface of a cylinder with its axis parallel to the direction of oscillation.  
   
   
       7 . A method according to  claim 6  wherein the freezing surface is the surface of a vertical cylinder the lower end of which comprises a hemispherical protrusion.  
   
   
       8 . A method according to  claim 1  wherein the freezing surface comprises the inner and outer surfaces of a cylindrical tube with its axis parallel to the direction of oscillation.  
   
   
       9 . A method according to  claim 1  wherein the freezing surface comprises the surfaces of a plurality of members which are rigidly mounted onto a single base.  
   
   
       10 . A method according to  claim 9  wherein the members are cylinders or cylindrical tubes with their axes parallel to the direction of oscillation.  
   
   
       11 . A method according to  claim 1  in which the temperature of the freezing surface is between −1° C. and −20° C.  
   
   
       12 . A method according to  claim 1  in which the temperature-of the freezing surface is cycled from a temperature between 5° C. and 25° C. below the freezing point of the aqueous mixtures to a temperature more than 0° C. and less than 5° C. below the freezing point of the aqueous mixture.  
   
   
       13 . A method according to  claim 1  wherein the aqueous mixture comprises an aqueous solution and/or suspension of edible ingredients selected from the group consisting of sugars, food acids, colours, flavours, proteins, fats emulsifiers and stabilizers.  
   
   
       14 . A method according to  claim 13  in which the aqueous mixture is a milk shake, water ice mix or an ice cream mix.  
   
   
       15 . An apparatus for partially freezing an aqueous mixtures comprising: 
 a freezing surface;    a cooling means capable of cooling said freezing surface to below −1° C. and    an oscillation means which is coupled to said freezing surface    characterized in that said oscillating means is capable of linearly oscillating said freezing surface in a direction that is not perpendicular to at least part of the freezing surface with a frequency of between 20 and 200 Hz.    
   
   
       16 . An apparatus according to  claim 15  wherein the oscillation means is capable of oscillating said freezing surface with an amplitude of between 1 mm and 20 mm.  
   
   
       17 . An apparatus according to  claim 15  wherein the oscillation means is selected from the group consisting of a loud speaker, a magnetic coil, an electrodynamic shaker and a reciprocating electric motor.  
   
   
       18 . An apparatus according to  claim 15  wherein the oscillation means is coupled to the freezing surface by a coupling means selected from the group consisting of direct coupling, a resilient member, and a cantilever beam.  
   
   
       19 . An apparatus according to  claim 15  wherein the freezing surface comprises the surfaces of a plurality of members rigidly mounted onto a single base and which are capable of being oscillated by a single oscillation means.