Field of the invention

The present invention relates to beverages comprising foamed milk and process for improving the foamability of such beverages.

Background of the invention

A trend in the field of beverages concerns beverages comprising milk and in particular foamed milk. Beverages comprising coffee and foamed like latte macchiatos, cappuccinos are more and more consumed.

Usually these beverages are prepared from fresh milk which is frothed with steam inside a frothing device. Resulting fresh milk foam is excellent in terms of taste and texture. Yet such frothing devices are often manually handled. Consequently the quality of the foam can depend on the experience of the person preparing the foam. Moreover these frothing devices are often hard to clean which can create hygiene issues. Finally fresh milk has to be refrigerated and presents short shelf life.

It is possible to prepare beverages with milk foam with more convenient and automatic beverage preparation machines. In particular it is known to prepare milk foam from soluble milk powders and milk concentrates by mechanically whipping one of said ingredient with a diluent - usually water - by means of a mixer, a whipper, an agitator or by means of water jets. The mechanical agitator is usually a whipper actuated by a motor

In order to improve the quality of the foam prepared with these machines nad these ingredients it has been proposed particular whippers like the whippers described in EP 1 476 060 or WO 2013/149942. Yet it has never been proposed to provide a milk starting ingredient which could present improved foamability properties when mechanically reconstituted and mechanically frothed.

It is known to add additives like foam boosters in milk powders. Yet these powders are dedicated to the preparation of foamy beverage in a cup by pouring water on the powder. Such additives are not desired for beverage preparation with a mechanical whipper. Moreover these additives raise costs of the milk component and can impact the taste of the foam.

In EP 1 903 885 it has been proposed to add a multivalent ion source like a calcium source in milk powder before or while it is mixed with water and whipped.

It is an object of the present invention to propose a process to improve foaming of milk when said milk is prepared in a beverage dispenser. It is an object of the present invention to propose a process to improve foaming of milk when said milk is prepared in a beverage dispenser starting from milk powder or milk concentrate. Summary of the invention

The invention concerns a process for producing a foamed milk, said process comprising the steps of :

a) - reconstituting milk by dissolution of a milk powder or a milk concentrate with a diluent, said milk powder or milk concentrate being selected in the list of : low heat milk powder, medium heat milk powder, low heat milk concentrate and medium heat milk concentrate,

b) - adjusting the pH of the milk between 6,8 and 7,5, and

c) - simultaneously or subsequently to the pH adjustment of step b), whipping the milk.

In the process of the present invention the raw material can be a milk powder or a milk concentrate.

If a milk powder is used as a raw material it is selected in low and medium heat milk powders. Low and medium heat milk powders are defined according to the heat treatment classification based on the whey protein nitrogen index (WPNI) of the milk powder. This whey protein nitrogen index (WPNI) refers to the amount of still denaturable serum protein left in the powder after heat treatment as described in literature, especially in "Walstra, P., J.T.M. Wouters, T.J. Geurts, Dairy Science and Technology, Second ed., Boca Raton : CRC Taylor & Francis", page 530. In the present invention the raw material can be a low heat milk powder that is a powder presenting a whey protein nitrogen index (WPNI) greater than 6,0 mg N/g or a medium heat milk powder presenting a WPIN comprised between 4,0 and 5,99 mg N/g.

Preferably the milk powder is agglomerated.

If a milk concentrate is used as a raw material it is selected between low and medium heat milk concentrates. Low and medium heat milk concentrates are defined according to the same above heat treatment classification based on the whey protein nitrogen index (WPNI) of the milk powder derived from the concentrate.

Milk powders and milk concentrates cover powders and concentrates with any fat level such as full fat milk, skimmed milk, semi skimmed milk for example.

In step a) milk can be reconstituted by dissolving the milk powder or the milk concentrate in a diluent, generally water. Dissolution is usually achieved by mixing the powder or the concentrate with the diluent. The temperature of the diluent can depend on the nature of the final prepared beverage which can be either hot or cold. Preferably the diluent is hot water presenting a temperature comprised between 75 and 85°C.

In step b) pH of milk is adjusted in order to reach a pH comprised between 6,8 and 7,5, in another aspect between about 6,9 and about 7,4, in another aspect between about 7,0 and about 7,3, in another aspect between 7,0 and 7,2. Since the pH of milk is usually of about 6,7 pH of milk is raised by adding a component able to raise said pH. Such a component can be selected in the list of the following components : phosphate salts, citrate salts, hydroxides, carbonates and combinations thereof.

When the process starts from milk powder as a raw material, the process can be implemented according to two different modes.

According to a first mode step a) occurs before step b).

According to a second mode steps a) and b) can occur simultaneously, preferably inside a dissolution chamber in which milk powder is dissolved. The at least one component able to raise the pH of milk is introduced with the milk powder and the diluent. According to said second mode, when a milk powder is used as a raw material, said powder can comprise an additive for adjusting the pH of the reconstituted milk when said powder is dissolved with water. Consequently the mere fact of dissolving the powder with a diluent, preferably water, enables the implementation of step b) simultaneously to step a). Said additive can be comprised in the list of the following components : phosphate salts, citrate salts, hydroxides, carbonates and combinations thereof.

Step c) aims at whipping the milk of which pH has been adjusted in order to get whipped milk. Whipping can occur according to any known methods.

Preferably the step of whipping is done mechanically, more preferably this step is implemented with a mechanical whipper inside a whipping chamber. Generally the whipper is actuated by a motor.

Alternatively the whipping can be implemented with at least one water jet, said at least one water jet hitting the milk and frothing it. Simultaneously said at least one water jet can provide water to dissolve milk powder or milk concentrate in order to foam the milk. Such a type of whipping is described in WO 2010/034722 for example.

Step c) can occur after step b) or simultaneously to step b). In practice a component able to raise pH of milk can be added to milk while it is whipped. The whipping enables the mixing of said component with milk.

According to the preferred embodiment the process of the present invention is implemented in a beverage dispenser comprising a container for storing milk, a milk powder or a milk concentrate, a device for dosing milk, the powder or the milk concentrate and a whipping chamber for mixing a dose of milk, milk powder or milk concentrate and optionally a diluent.

According to an embodiment of the process of the present invention the foamed milk resulting from step c) can be mixed with a non-milk beverage component. Non-milk beverage component relates to a beverage that does not comprise milk. Such a component can be coffee, tea or a beverage component in which milk is not the major component like chocolate reconstituted from chocolate powder.

The present invention presents the advantage of enabling the improvement of the foaming properties of a milk powder or a milk concentrate when it is used in a beverage dispenser. The present invention presents a significant advantage because current milk powders or milk concentrates can be used in beverage dispensers, yet their foaming properties can be improved inside the dispenser itself.

Brief description of the drawings

The characteristics and advantages of the invention will be better understood in relation to the following figures.

Figure 1 is a schematic diagram a beverage dispenser configured for preparing foamed milk beverages.

Detailed description of the Figure

With reference to Figure 1 the beverage dispenser comprises at least one beverage ingredient container 13a, 13b connected to a dosing unit 14 able to provide beverage ingredient doses to a dissolution chamber 6. The containers 13a, 13b can be disposable tanks like a cartridge, a can or tin, a pouch, ... or it can be non-disposable containers that are refilled with beverage ingredients. The beverage ingredient can be any ingredient that forms a beverage when mixed with a liquid diluent, preferably water. It can be a soluble powder or a soluble liquid concentrate. According to the invention it is preferably milk powder or milk concentrate. When several ingredient containers 13a, 13b are present, they preferably contain different beverage ingredients. For example one can store a semi skimmed milk powder and the other one can store skimmed milk powder.

The dosing unit comprises means for dosing the beverage ingredient. This means can be a dosing screw, a dosing auger, perforated discs for a milk powder or a peristaltic pump for a milk concentrate. The dosing unit is placed at the bottom of the container to receive the beverage ingredient therefrom by gravity. The dose of beverage ingredient issued from the dosing unit is delivered to the dissolution chamber 6 where it is mixed with a diluent, usually water, introduced from a diluent inlet 12. The shape of the chamber 6 and the orientation of the diluent inlet 12 are such that the diluent creates a sufficiently turbulent stream that helps the dissolution of the beverage ingredient in the diluent in the chamber. The mixture of the dissolved beverage ingredient is then introduced in a mixing device 1 comprising a whipper housing 2 and a back wall 4. The assembly of the whipper housing 2 and the back wall 4 forms a chamber in which is lodged a rotor 3 such as an impeller. The rotor is connected to a drive shaft 41 fixed to the frame 10 of the dispenser. The drive shaft is actuated by a motor 8. The whipped beverage leaves the mixing device 1 through an outlet 7 that can be connected to an outlet tube 9 and is delivered in a cup 15.

Examples

Comparative Example 1 : preparation of foamed milk from milk powder according to prior art

Milk was reconstituted from an agglomerated low heat milk powder presenting a WPNI of

6,93 mg N/g : powder was dissolved in water in a weight ratio of 9,3 g of powder for 90,7 of water at ambient temperature by gentle stirring in order to reconstitute milk. The pH of said reconstituted milk was 6,7. Then 100 ml of said reconstituted milk was heated at 80°C and introduced through the opened top of the mixing bowl of a beverage dispenser referenced as Milano and commercialised by Nestle Professional. This dispenser is configured according to the general principle illustrated to Figure 1 except that it comprises several containers 13 and several corresponding mixing bowls 6 in order to prepare different beverages. In the present example, since milk was not reconstituted inside the mixing bowl of the dispenser, the dosing unit was not activated and no diluent was introduced through the diluent inlet 12 during the beverage preparation. The whipper was actuated during 13,5 seconds once heated reconstituted milk was introduced in the mixing bowl. After starting the whipper the valve closing the outlet 9 was opened to deliver foamed milk in a graduated transparent beaker at the dispensing area of the dispenser. Example 2 : preparation of foamed milk from fresh milk according to the invention

A foamed milk was prepared from the same fresh milk and in the same conditions as in Example 1 except that the pH of the reconstituted milk was raised from 6,7 to 7,1 by adding Na ₂ C0 ₃ before its introduction in the mixing bowl of the beverage dispenser. Comparative Example 3 : preparation of foamed milk according to prior art

Example 1 was reproduced except that the milk powder was introduced in the powder container of the dispenser and foamed milk was ordered from the dispenser. Consequently the reconstitution and the whipping of the milk were implemented simultaneously in the mixing bowl of the dispenser.

The foamed milk was dispensed in a graduated transparent beaker at the dispensing area of the dispenser.

Example 4 : preparation of foamed milk according to the invention

Example 3 was reproduced except that milk powder was mixed with powder of Na ₂ C0 ₃ inside the dispenser powder container. The ratio of the powders mixture was defined so that milk reconstituted from the mixed powders presents a pH of 7,1.

Results

The foamability and the texture of the foamed milks of Examples 1 , 2, 3 and 4 were measured as follows.

Foamability relates to the foam volume and was deduced from the height of foam in the graduated transparent beaker

Texture relates to foam stiffness and was determined with a Texture analyser TA-HDi Penetration tests were performed with the following parameters :

- 50 mm diameter cylindrical probe or 35 mm cylindrical aluminium probe,

- 1 mm/s penetration speed,

- 20 mmm deep in the foam.

The value of the maximal force was selected to express foam stiffness. Table 1 summarises the results for powders of examples 1 , 2 and 3

Table 1

The results illustrate how foamed milks prepared with the process of the present invention presented increased foaming qualities in term of quantity and texture. Results also illustrate the difference in foaming between :

- a milk pre-reconstituted from a milk power and water and subsequently foamed in a machine and

- a milk simultaneously reconstituted from a milk powder and foamed in a machine.

Yet whatever the process used for preparing the foamed milk the present invention improves the foaming qualities of the raw material.