GB2177283A - Milk powder - Google Patents

Abstract

A milk powder obtained by spray drying and suitable as a starting material for the manufacture of milk chocolate, wherein the weight average particle size of the milk powder is less than 80 mu m and the porosity of less than 5 ml/100 g powder.

Description

SPECIFICATION Milk powder a process for the manufacture thereof a process for manufacturing milk chocolate.

The present invention relates to a milk powder suitable as a starting material for milk chocolate and further to a process for manufacturing such a milk powder by spray-drying and a process for the manufacture of milk chocolate.

In the manufacture of milk chocolate products particles of cocoa, sugar and milk powder are ground in a fatty phase in which the following three process steps can be distinguished: 1. comminution of the particles, 2. taste refinement, 3. shaping.

During comminution the solid constituents cocoa, sugar and milk powder are processed together, that is to say, exposed to a grinding action with the purpose of comminuting all the particles to the extent that they are no longer organoleptically perceptible in the final product. This means that the maximum particle size is reduced to approx. 30-50 ltm.

During shaping the practically ready milk chocolate must of course satisfy a number of criteria. One of them is that the viscosity must be low enough to allow the shaping process to proceed well. It is conventional that the desired viscosity is obtained by adding extra cocoa butter to the mass before shaping.

Since cocoa butter is the most expensive (main) constituent of chocolate, it is always tried to attain such processes that a minimum quantity of cocoa butter is required for this final viscosity reduction.

Among the factors of influence that are of importance to a minimum cocoa butter consumption are, inter alia, the moisture content of the mixture, the addition of an allowed small amount of lecithin, the properties of the solid constituents and the comminution process.

As for the properties of the solid constituents especially the type of milk powder to be used proves to be influential.

Milk powder is often used as a starting material for milk chocolate in pure form and standardized at a specific fat content (e.g., 26% or 1%).

In the manufacture of milk powder a development has occurred in the past decennia that has proved to be of importance to the manufacture of chocolate. The fact is that the formerly conventional roller-drying process has been increasingly replaced by the spray-drying process. Accordingly, the chocolate manufacturer is confronted with the choice between these two types of milk powder. This choice is connected with difficult questions and problems. In the dairy industry spray drying is generally considered a superior process,inter alia because the thus prepared milk powder has sustained much less heat damage than roller-dried milk powder and is considerably better water-soluble.

Also in view of economic and hygienic criteria the roller-dryer is usually inferior to the spray-dryer. In many countries roller-drying of milk has therefore nearly completely disappeared to give way to spray-drying.

The chocolate manufacturer, who for a long time past has been accustomed to roller-dried milk powder and is confronted with spray milk powder will establish a taste difference: the new product has a more natural, less burnt taste. This will affect the taste of the chocolate, i.e., very generally speaking, in a favourable sense. The fact is that nowadays we notice a very frequent use of spray milk powder in chocolate.

Yet the new product also has a great disadvantage and in this connection we return to the chocolate manufacturing process. The fact is that the viscosity of chocolate manufactured with spray milk powder proves to be higher than when roller-dried milk powder is used.

This means that the new product necessitates the addition of more cocoa butter, which is a very serious economic disadvantage. For this reason spray milk powder is often known in the chocolate industry as a 'cocoa butter devourer'. An explanation of this difference is not known. Of course, it has been searched for, but there is a large number of different properties and it is unknown which of them are of importance to the chocolate viscosity.

The size distribution and the shape of both types of powder particles, for instance, show characteristic differences. But it may also be argued in view of the two manufacturing processes that the mechanical strength and the behaviour during distortion, crushing and grinding must indeed strongly differ. Very known is the difference in heating and the copending protein denaturation, and furthermore differences with respect to the milk sugar crystallization might also be of importance.

Finally, it is sometimes reported that the high content of free fat in roller dried milk powder contributes to a low cocoa butter consumption. This idea is obvious because, in a sense, on the exterior of milk powder particles such fat may replace cocoa butter in chocolate. But this, too, is at most a partial explanation, for when fat is brought into spray milk powder in free form (e.g., by mixing spray-dried skin milk powder with milk fat) only a very limited improvement will be obtained.

According to British patent 637796 spray milk powder is more suitable for being processed in chocolate when it has a low porosity, i.e. a reduced content of vacuoles or air bubbles. The thus obtained improvement,however, is relatively small, and consequently this proposal has not found acceptance in practice.

Summarizing, it may therefore be said that in the manufacture of milk chocolatee the nearly disappeared roller-dried milk powder is attractive from a viewpoint of business economics, but gives problems as for its taste, and that spray milk powder has an excellent taste, but leads to a high cocoa butter consumption in the manufacture of chocolatee and can therefore only be used in this manufacture to a limited extent.

The object of the invention is therefore to provide a milk powder which combines both good properties.

Surprisingly, it turned out that this object was attained by means of a spray milk powder having both a great fineness and a low porosity. In explanation of the invention these terms will be defined as follows.

The fineness of a powder is expressed as the weight average particle size which indicates that particles having a smaller diameter account for 50% of the powder weight. The weight average particle size is determined by means of a Malvern 2600 D particle sizer, based on the principle of diffraction of laser irradiation.

The porosity is defined as a percentage which indicates the average volume fraction of the cavities (air bubbles or vacuoles) in the powder particles. The porosity is calculated from the density of the powder, as it is measured with an Air-Comparison Pycnometer according to Beckman. The following formula is used in the calculation: 1 1 Porosity=100 (---) ml/100 g powder Dl D2 wherein: D, = real density of powder in g/ml D2 = density of powder at a porosity of O ml/100 g powder. For a whole milk powder with 26% fat this density is 1.28 g/ml.

For the known spray powders the weight average particle size is about 80-120 pm, and the porosity often ranges between 5 and 40 my/100 g powder.

Spray milk powders according to the invention have a weight average particle size less than 80 ,um and a porosity less than 5 ml/100 g powder.

According to a preferred embodiment of the invention these values are respectively 40-70 ,um and less than 3 ml/100 g powder. It is further preferred that the final fat content is adjusted by later adding at least a portion of the milk fat to the spray-dried milk powder.

Preferably, the amount of later added fat is 20-50% of the final fat content.

The invention will hereinafter be illustrated by the following examples: the examples show the effect of the invention over the saving of cocoa butter. It should be noted that the examples are not intended to be limitative.

Where reference is made to milk powders, these also include other milk-derived chocolate starting materials, such as whey powders, whether or not proteinenriched or mixed products obtained by spray-drying, e.g., consisting of milk constituents, vegetable fats and added sugars. Where reference is made to spray-drying, different embodiments of this process are included, such as centrifugal spraying, pressure spraying, propellant gas spraying etc. Also the term milk chocolatee is used in a broad sense in this connection, so that it also includes immitation chocolatees, coverings and the like. In fact, the technological situation to which the present invention relates occurs in all of these cases.

Example I 200,000 raw fresh farmer's milk was standardized to obtain a powder with 26% fat and 3% moisture, then pasteurized (for 30 seconds at 850C) and evaporated in a downdraft evaporator. Subsequently it was dried in a spray dryer by means of a wheel sprayer at which measures were taken to supply vapour to the sprayer wheel. The vapour pressure was 0.5 kg/cm2 measured in the vapour supply pipe to the sprayer wheel. The temperature of the dry air input was 185"C and of the dry air output 87"C. The revolution speed of the sprayer wheel was 11000 rpm. The resulting product was packaged in multi-walled bags in the usual manner. The thus obtained milk powder consisted of particles having a weight average particle size of 64 ,am and a porosity of 2.3 ml/100 g powder.The thus obtained milk powder was used for the manufacture of milk chocolate. The recipe was as foliows: cocoa mass 90 g powdered sugar 450 g milk powder 230 g cocoa butter 230 g lecithin 4 g The ingredients (with the exception of a portion of the lecithin, which was later added) were mixed and then rolled in a three-roll Pascall roller. Subsequently the mass was conched and shaped into tablets. The flowing properties (viscosity) were measured with a Haake RV12 rotation viscosimeter at 40"C.

The measured values were converted into a Casson viscosity ()1CA) and a Casson flowing point (icy) as described by inter alia H. Fincke, Handbuch der Kakaoerzeugnisse, Springer Verlag Berlin/Heidelberg/New. York.

The results were: UCA = 2.3 Pa.S and rCA = 9.1 Pa.

These results were such that the chocolate was suitable for shaping while the cocoa butter content was only 23%, as appears from the above recipe. For the purpose of comparison milk chocolate was made from a corre sponding manufactured milk powder but without vapour being supplied to the sprayer wheel, having a weight average particle size of 95 cm and a porosity of 15 ml/100 g powder according to the above recipe. The viscosity of the product was considerably higher, i.e. such that 3.2% extra cocoa butter had to be added in order to obtain the same viscosity level as of the above described powder.

Example II 100,000 kg raw fresh farmer's milk was standardized to obtain a powder with 18% fat and 3% moisture, then pasteurized (for 1 minute at 90"C) and evaporated in a downdraft evaporator. Subsequently, it was dried by means of pressure spraying, using nozzles especially selected for the manufacture of a powder with small particles. The spraying pressure was 25 mPa. The dry air temperatures were respectively 187"C (input) and 92"C (output). The thus obtained product was then mixed in an industrial mixer with milk fat in a mixing ratio of 90 parts of powder and 10 parts of milk fat in such a manner that the final product had a fat content of 26%. The weight average particle size of this product was 76 ,lem, and the porosity was 4.5 ml/100 g.

The thus obtained powder was processed to milk chocolatee, as described in Example I.

The viscosity of the chocolate was measured, as in Example I, with the following result: ?;cA = 3.1 Pa.S, and rCA = 9.6 Pa, low enough to shape the chocolate A powder correspondingly manufactured but under generally accepted conditions during spraying and having a fat content of 26% immediately after spraying (no mixing with milk fat) gave, in an identical chocolatee manufacturing process, a chocolatee having such a viscosity that 2.5% extra cocoa butter was required for equalling the flowing properties of the above-mentioned powder.

Claims (12)

1. A milk powder obtained by spray-drying and suitable as a starting material for the manufacture of milk chocolate, the weight average particle size of the milk powder being less than 80,'tom and the porosity of the milk powder being less than 5 ml/100 g powder.

2. A milk powder according to claim 1, in which the weight average particle size of the milk powder is 40 to 70 m.

3. A milk powder according to claim 1 or 2, in which the porosity of the milk powder is less than 3 ml/100 g powder.

4. A process for manufacturing milk powder suitable as a starting material for the manufacture of milk chocolate, the processes including manufacturing, by spray-drying, a milk powder having a weight average particle size of less than 80 um and a porosity of less than 5 ml/100 g powder.

5. A process according to claim 4, in which the final fat content is adjusted by later adding at least a portion of the milk fat to the spraydried milk powder.

6. A process according to claim 5, in which the amount of later added milk fat is 20 to 50% of the final fat content.

7. A process according to any one of claims 4 to 6, in which a milk powder having a weight average particle size of 40 to 70 i,m is manufactured.

8. A process according to any one of claims 4 to 7, in which a milk powder having a porosity of less than 3 ml/100 g powder is manufactured.

9. A process for manufacturing milk chocolate, in which a milk according to any one of claims 1 to 3 is used as a starting material.

10. Milk powder substantially as hereinbefore described in either Example.

11. A process of manufacturing milk powder the process being substantially as hereinbefore described in either Example.

12. A process of manufacturing milk chocolate, the process being substantially as hereinbefore described in either Example.