An object of the invention is to provide a method of coating particulate matter whereby the material produced is free flowing, well encapsulated, and/or has undergone minimal breakdown during the coating process.

According to the invention there is provided a method of coating particulate matter comprising mixing particulate matter and a liquid substance in a mixer and rapidly cooling the mixture.

The particulate matter and liquid substance are preferably mixed in a low shear mixer, most preferably on slow speed. In this respect, a low shear mixer is typically any mixer that does not substantially physically damage the powder. In general, the specific type and speed of the mixer may be selected to suit the strength of the powder being used. Preferably the particulate matter comprises particles with a diameter substantially in the range 0.5 mm to 25 cm. The coating material is typically defined by the liquid substance or liquid fraction which may comprise one or more of the following:- (1) fat, oil and/or wax which is normally liquid at room temperature; (2) fat, oil and/or wax which is normally solid at room temperature; (3) chocolate or chocolate based substance with or without colour and/or flavour additives;

(4) flavour substances, typically oil fractions or emulsions; (5) starch substances or mixtures, which may comprise hydrophillic and/or hydrophobic mixtures; (6) fat, oil and/or wax containing a liquid and/or powder flavour; (7) fat, oil and/or wax containing a liquid and/or powder colour.

Any mixture of one or more of the above may be used.

For any of the above, where the substance is normally solid at room temperature, the liquid substance for use in the method of the invention may be obtained by conventional means such as melting.

Preferably, the liquid substance is added to the mixer in a quantity substantially in the range 0.25% to 60% of the particulate matter added.

The mixture may be rapidly cooled by the direct addition of a cooling agent such as liquid nitrogen and/or chilled air to the mixer. Thus, optionally mixing may continue during such rapid cooling. Alternatively or additionally the mixture may be cooled or further cooled in a fluid bed. The latter may be cooled by injection of a cooling agent such as by chilled air and/or direct liquid nitrogen injection. The fluid bed may be a batch or continuous fluid bed. Thus, the mixture may be transferred from the mixer to a fluid bed for rapid cooling. Alternatively or additionally, the rapid cooling may comprise the direct injection or fluid bed injection

of liquid oxygen, carbon dioxide, mixtures of these and liquid nitrogen or any mixture or combination of the aforementioned cooling agents. Preferably the rapid cooling comprises from substantially 1 to 60 seconds from the time that the liquid phase comes in contact with the cooling agent. Preferably the chilled air comprises air below about 100C.

The invention further provides particulate matter coated according to a method of the invention.

The free flowing properties of the coated particulates is enhanced by the rapid cooling which affects the crystal form where fat/oil/wax is used as all or part of the coating material.

Irregular shapes can be easily coated using the method of the invention and it is possible by carrying out the process a number of times, for example two or three times, to add different coating materials one on top of the other.

The low shear mixer may be of any suitable type such as drum type, tote blenders, slow moving screw or paddle type. The fluid bed may comprise a vessel having an air distribution grate at a lower end thereof. One or more filters may be positioned at an upper end of the vessel to filter out entrained solids. Nozzles for spraying atomised liquids, typically water, may be positioned in, on or adjacent to, the vessel, for example, in the sides or top of the vessel.

The invention will now be described further by way of example only, and with reference to the accompanying drawings in which:-

Fig. 1 is schematic view showing use of a low shear mixer in the method of the invention; and Fig. 2 is a schematic view showing use of a fluidised bed agglomerator in the method of the invention.

Referring to Fig. 1, matter is added as shown schematically by arrow A, in powder form to a low shear mixer 1 comprising an open topped vessel 2 having mixing blades or paddles 4 located therein. The blades are mounted on a driving shaft 6 which is rotated by motor means 8 so that the blades move slowly. It will be appreciated that any suitable low shear mixer may be used and for example, a ribbon or screw mixing means may be used instead of blades 4 and shaft 6.

While or after the powders are added, the liquid substance is added typically while the blades are moving.

This is illustrated by arrow B. As the mixture is mixed, liquid nitrogen or chilled air is added to the mixer as shown at C by suitable means such as nozzles located in the sides of the mixer. The coated powder is output via a suitable outlet 10 on the vessel 2, as shown by arrow D.

Referring to Fig. 2, the mixture 12, for example transferred from a mixer as described with reference to Figure 1 without the coolant C, is added to a fluidised bed comprising an open topped vessel 14. Liquid such as water may be sprayed into the vessel via one or more nozzles 16 located in or on the vessel. Typically the nozzles 16 are designed to atomise the liquid. The base of the vessel 14 comprises a mesh plate 18 and the vessel is connected to a chilled air or liquid nitrogen supply 20 so that, in use, chilled air or liquid nitrogen passes up through the mesh plates, through the mixture and out

through filters located at the top of the vessel 14.

Other rapid cooling supply means 20 may be used as described above.

It will be appreciated that the present invention is not intended to be restricted to the details of the above embodiments which are described by way of example only.