GB2035035A - Production of milk powder - Google Patents

Abstract

A process for the preparation of instantised milk powder having a fat content in excess of 10% comprises the steps of wetting an instantisable milk powder having a fat content in excess of 10% to form agglomerates and drying said agglomerates, wherein said agglomerates are treated during their production with lecithin or a lecithin fraction in the form of an aqueous emulsion. The process is particularly applicable to full cream milk powder and results in acceptable, cold water soluble high fat milk powder.

Description

SPECIFICATION Production of milk powder This invention relates to the production of an instantised milk powder. More particularly it relates to the production of a full cream milk powder.

Milk powders which contain a low level of fat, by which we mean less than about 10% can normally be made instant by a procedure in which the powder is made to form into granules by wetting and then drying. The powder agglomerates then have sufficient weight to overcome the surface tension of water or other liquids and so disperse. Milk powders with higher fat contents, by which we mean fat contents in excess of 10%, cannot be made instant in this manner because the fact present acts to prevent solution in water.

It has been proposed to overcome this problem by the use of a wetting agent, such as lecithin, with which the powder agglomerates are coated. Thus according to one proposal, in UK Patent Specification 1,301,796, a process for treating a powdered fat-containing milk product is disclosed wherein powder agglomerates having a particle size of more than 100 y are coated with lecithin, possibly dissolved in a fat.

The use of lecithin as such can lead to viscosity problems and the use of additional fat as carrier for the lecithin may lead to flavour problems.

We have found that if the lecithin is applied as an aqueous emulsion the above mentioned problems are overcome.

The use of lecithin in the form of an aqueous emulsion has not previously been proposed nor indeed suggested. It is not normally considered that lecithin would readily be formed into an aqueous emulsion and indeed according to the invention it is desirable to use a lecithin which has certain characteristics which enable it to be readily emulsified in water. Thus, it is preferred to use a soya bean derived lecithin or lecithin fraction. Preferably the lecithin will contain from 55-65% phosphatides. If a lecithin fraction is used this will preferably contain more than 80% phosphatides. The use of lecithin having a phosphatides percentage in excess of 65% is less preferred because they are very viscous.

According to the invention therefore there is provided a process for the preparation of a high fat instantised milk powder which comprises the steps of wetting an instantisable high fat milk powder to form agglomerates and drying said agglomerates wherein said agglomerates are treated at a convenient stage in their production with lecithin (or a lecithin fraction) in the form of an aqueous emulsion.

The aqueous lecithin emulsion is prepared by emulsifying the lecithin or lecithin fraction in water with a high speed mixer to form a stable emulsion. In general 0.5% to 2.5% by weight of lecithin will be used with water to make the emulsion.

Preferably, the treatment with the aqueous emulsion is effected by spraying the milk powder during the wetting step with the aqueous emulsion of the lecithin. In a particularly convenient embodiment of the invention wetting is effected with the aqueous emulsion of lecithin.

The milk powder which is used as starting material in the process may either be formed on site or produced elsewhere, since it is a commercially available product.

This proposed method is specially suited for use on an apparatus consisting merely of an agglomerator, with a single fluidised bed drier, to which is fed the milk powder. However if the milk powder is produced on site the apparatus used may be one which is generally referred to as a straight-through spray drier/agglomerator in which the powder is produced in the spray drier and passed directly to the agglomerator.

The milk powder which is fed to the agglomerator will be a high fat content product preferably a low heat treatment full cream milk powder with not less than 20% butterfat preferably not less than 26% butterfat. The fat content of the milk powder will be controlled by blending of milk form a number of farms, if necessary, and will be a known parameter. The free fat content of the milk should preferably be less than 2.0% by weight of the milk powder.

The amount of lecithin which is supplied to the powder agglomerates can be quite low.

Thus we find than an amount of lecithin of the 0.1% by weight based on the weight of the powder agglomerates is sufficient to produce an advantageous effect, although somewhat higher levels may be preferred, of 0.2 to 0.4 or even 0.5%. Although levels above 0.5% could be used food regulations presently limit the amount of lecithin which can be supplied to milk powder to not greater than 0.5%. The amount of lecithin can readily be controlled knowing the input of milk powder and the input of aqueous emulsion of lecithin.

Preferably, the temperature at which the aqueous emulsion of the lecithin is applied to the powder agglomerates should not be greater than approximately 70"C because of possible flavour changes at higher temperatures. Apparatus suitable for carrying out the process of the invention is shown diagrammatically in the accompanying drawings. The apparatus can be described as a re-wet agglomeration plant.

Referring to the drawings milk powder is fed into a re-wet chamber 1. Positioned in the top of the chamber is a spinning disc atomiser 2 through which the aqueous emlusion of lecithin may be introduced a fine spray. The re-wet powder ih the form of powder agglomerates then passes to a fluid bed indicated at 3 where it is dried and passes to classifier 4.

The final product leaves at 5. An exhaust cyclone 6 is connected to the fluid bed chamber 3. Air is introduced to maintain the fluid bed at inlets 7.

Instead of the spinning disc atomiser 2 there may be provided a series of nozzles in the re-wet chamber for introduction of the aqueous emulsion of lecithin. Also instead of the atomiser or the nozzles in the re-wet chamber there may be provided nozzles in the first part of fluid bed drier for the introduction of the said aqueous emulsion. One or more of the measures recited above may be used for the introduction of the aqueous emulsion.

The following Examples illustrate the inven tion :- Example 1 An apparatus as shown in the drawing and described above was used. The whole milk powder which was treated had a butterfat content of 26%, a free fat content of 0.61% and had been produced by spray drying with a low heat treatment. The powder entered the chamber through the inlet at the top of chamber 1 and the lecithin emulsion was sprayed on it through the disc atomiser 2.

Temperatures in chamber 1 (50"C) and in the fluidised bed 3 were kept to a minimum to reduce heat damage, whilst maintaining the moisture content of the final product below 4%.

The amount of lecithin in the final product was 0.3%. An antioxidant was also incorporated in the aqueous feed, along with the lecithin.

The resultant product was found to have a wettability of the order of 20 seconds in warm water (60-70") and 1 minute in cold water (20 ).

The product formed a clean solution rather than a suspension and there were no unsightly floaters.

Example 2 A similar full cream milk powder as specified in Example 1 was taken and treated with a lecithin-water emulsion of the type described in Example 1. The lecithin-water emulsion was this time sprayed via atomiser nozzles onto the agglomerates as they moved on the fluidised bed 3. The particles received an even coating with 0.5% lecithin.

The resultant product gave a clear solution when stirred into water at between 20 and 40"C and dispersed in approximately 40 sec.

with a minimum number of floaters visible.

Claims (14)

1. A process for the preparation of a high fat (as herein defined) instantised milk powder which comprises the steps of wetting an instantisable high fat (as herein defined) milk powder to form agglomerates and drying said agglomerates wherein said agglomerates are treated during their production with lecithin or a lecithin fraction in the form of an aqueous emulsion.

2. A process as claimed in claim 1 wherein the aqueous emulsion contains from 0.5% to 2.5% by weight of lecithin.

3. A process as claimed in claim 1 or claim 2 wherein the agglomerates are treated with from 0. 1% to 0.5% by weight of lecithin based on the weight of the agglomerates.

4. A process as claimed in claim 3 wherein the agglomerates are treated with from 0.2% to 0.4% by weight of lecithin.

5. A process as claimed in any of claims 1 to 4 wherein the agglomerates are treated with the aqueous emulsion at a temperature of not greater than approximately 70"C.

6. A process as claimed in any of claims 1 to 5 wherein the instantisable high fat milk powder is a low heat treatment full cream milk powder with not less than 20% butterfat.

7. A process as claimed in claim 6 wherein the low heat treatment full cream milk powder has not less than 26% butterfat.

8. A process as claimed in any of claims 1 to to 7 wherein the instantisable high fat milk powder has a free fat content of less than 2.0% by weight.

9. A process as claimed in any of claims 1 to 8 wherein the lecithin or lecithin faction is derived from soya beans.

1 0. A process as claimed in any of claims 1 to 9 wherein the lecithin contains from 55 to 65% phosphatides.

11. A process as claimed in any of claims 1 to 9 wherein the lecithin fraction contains more than 80% phosphatides.

1 2. A process as claimed in any of claims 1 to 11 wherein the treatment with the aqueous emulsion is effected by spraying the milk powders during the wetting step.

1 3. A process as claimed in any of claims 1 to 11 wherein the wetting step is effected with the aqueous emulsion.

14. A process for the preparation of a light fat (as herein defined) instantised milk powder substantially as herein described with reference to the Examples and/or the accompanying drawing.

1 5. A high fat (as herein defined) instantised milk powder whenever prepared by a process as claimed in any of claims 1 to 14.