WO2015091026A1

WO2015091026A1 - Process for preparing asoluble milk ingredient with improved foaming properties

Info

Publication number: WO2015091026A1
Application number: PCT/EP2014/076731
Authority: WO
Inventors: Markus KREUSS
Original assignee: Nestec SA
Current assignee: Nestec SA
Priority date: 2013-12-20
Filing date: 2014-12-05
Publication date: 2015-06-25
Anticipated expiration: 2016-06-20

Abstract

Process for preparing a milk component from raw milk, said process comprising at least the steps of standardising raw milk and then heating standardised milk, wherein : - the process comprises the step of adjusting the pH of standardised milk between about 6,8 and about 7,5 before the step of heating, and - the conditions for heating the standardized milk correspond to the heating conditions resulting in achieving a low or medium heat milk powder.

Description

PROCESS FOR PREPARING ASOLUBLE MILK INGREDIENT WITH IMPROVED

FOAMING PROPERTIES

Field of the invention

The present invention relates to soluble milk ingredients like milk powders or milk concentrates presenting improved foamability properties when mixed with a diluent in beverage preparation machine.

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 and 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.

It is an object of the present invention to propose a milk ingredient which can provide milk foam with improved foamibility when mechanically whipped.

It is an object of the present invention to propose a milk ingredient which can provide milk foam with improved foamibility when mechanically whipped without adding non-natural and/or expensive additives in the milk ingredient.

Summary of the invention

According to a first aspect, the invention concerns a process for preparing a milk component from raw milk, said process comprising at least the steps of standardising raw milk and then heating standardised milk, wherein :

- the process comprises the step of adjusting the pH of standardised milk between about 6,8 and about 7,5 before the step of heating, and

- the conditions for heating the standardized milk correspond to the heating conditions resulting in achieving a low or medium heat milk powder.

The process of the present invention aims at preparing a milk component presenting improved foamability, either as such or when mixed with water, and in particular when this milk component is used to prepare foamed milk by mechanical whipping.

In the process of the present invention the starting material is raw milk.

Firstly raw milk is standardised ; this can be achieved by appropriate mixing of skimmed milk and cream in order to control the fat content of the final milk component and/or the taste of the final milk component.

Standardized raw milk is further heat treated as a preservation process : this step is currently implemented to inactivate microorganisms and enzymes to make milk safe and more stable. Different heat treatments are known in the state of the art like thermisation, pasteurisation, UHT process, sterilisation which differ one from the other by the temperature and holding time. According to the invention, the heating applied to the milk correspond to the heating conditions resulting in enabling the production a low or medium heat milk powder from the milk.

Generally these conditions of heating, essentially the temperature and the time of heating, are set so that :

- a part of the milk proteins are denatured,

- the degree of denaturation of whey proteins is such that a powder derived from said heated milk leads to the classification of a low heat or medium heat milk powder.

In the present invention :

- such a low heat treatment corresponds to the process to get low heat milk powder that is to say powder having a whey protein nitrogen index (WPNI) greater than 6,0 mg N/g, and

- such a medium heat treatment corresponds to a WPNI comprised between 4,00 and 5,99 mg

N/g.

This whey protein nitrogen index (WPNI) refers to the amount of still denaturable serum protein left in the milk powder as described in literature, especially in 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 conditions for heating the standardized milk and corresponding to the heating conditions resulting in achieving a low or medium heat milk powder the present invention are generally performed by heating milk at a temperature of at least 74 °C during at least 10 seconds. The conditions can be adapted depending on the equipment used for heating, the volume size of the production, energy optimisation considerations, ...

The heating step can be implemented by means of any equipment usually used for heating milk like for example a plate heat exchanger. The flow of milk in the equipment is monitored in order to apply the conditions of time and heating temperature defined for the heating step. These conditions can depend on the size of the equipment and the temperature it applies.

According to the invention before the standardized milk is heated pH of standardized milk is adjusted in order to reach a pH comprised between 6,8 and 7,5, in another aspect between 6,9 and 7,4, in another aspect between 7,0 and 7,3, in another aspect 7,0 and 7,2. Since the pH of standardized milk is usually of about 6,7, the pH of standardized milk is raised by adding at least one food agreed 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.

According to one embodiment, further to the heating step milk can be concentrated to produce a milk concentrate. The concentration is generally implemented with an evaporator.

According to a second embodiment further to the heating step milk can be concentrated and then dried to produce a milk powder. In general milk is concentrated in order to reach a concentration adapted for further drying. The concentration is generally done with an evaporator. After the concentration step the concentrated milk can be spray-dried, freeze dried or rotary drum dried

Preferably milk powder is agglomerated after drying. Agglomeration presents the advantage of improving the flowability of the powder, especially in view in a further use in a beverage dispenser. The heat treatment applied prior to concentration and optionally drying is the prime determinant of the extent of whey protein denaturation during milk concentrate or powder manufacturing because minimal heat damage occurs during the concentration and drying stages.

According to a second aspect the invention concerns a milk component susceptible to be obtained from the process such as described hereabove. The milk component can be milk, a milk concentrate or a milk powder.

Optionally flavouring additives or functional additives can be mixed with the milk powder or the milk concentrate as it is known in the prior art.

According to a third aspect the invention concerns a process for preparing a foamed milk based beverage comprising the step of whipping the milk component susceptible to be obtained from the process such as described hereabove.

Optionally the milk component is mixed with water during the step of whipping, in particular if the milk component is a milk concentrate or a milk powder. The quantity of water that is mixed with milk component is defined so as to reconstitute milk from the milk concentrate or the milk powder. In order to prepare hot milk based beverage water preferably presents a temperature of at least 50°C.

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 form the milk based component. Such a type of whipping is described in WO 2010/034722 for example.

According to an embodiment further to the step of whipping the resulting foamed milk can be mixed with another non-milk beverage component. This non-milk beverage component can be coffee, tea, chocolate or syrup for example.

According to the preferred embodiment the foamed based milk beverage is prepared in a beverage dispenser comprising a container for storing the milk component, a dosing unit for dosing said milk component and a whipping chamber for whipping at least a dose of milk component. The dispenser can also comprise a water supply which can provide a dose of water to the whipping chamber. The milk component treated according to the process of the present invention enables the preparation of foamed milk based beverages presenting increased foamability and foam texture compared to foamed milk based beverages prepared with milk components produced according to standard processing conditions without pH adjustment before the low heat or medium heat treatment. Foamability and foam texture can be increased by at least 10 %.

In the present application the terms :

- "milk component" relates to milk or milk under one of its dehydrated form that is milk concentrate or milk powder,

- "milk based beverage" relates to a beverage comprising at least a milk component,

- "non-milk beverage component" relates to a beverage that does not comprise milk like coffee, tea or a beverage in which milk is not the major component like chocolate reconstituted from chocolate powder,

- "raw milk" relates to milk which has not been treated by a heat treatment that denatures whey proteins. Raw milk presents native milk proteins showing a whey protein denaturation inferior to 5 % generally. Raw milk covers milk with any fat level such as raw full fat milk, raw skimmed milk, raw semi skimmed milk for example. Brief description of the drawings

The characteristics and advantages of the invention will be better understood in relation to Figure 1 which 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 each connected to a respective 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 or a peristaltic pump for a beverage 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

Example 1 : milk powder preparation according to the prior art

A milk powder was prepared from a skimmed raw milk presenting a WPNI of 9,24 mg N/g as follows :

- skimmed raw milk was heat treated at 74°C during 30 seconds in a plate heat exchanger, - then heat treated milk was evaporated using a four effect falling film evaporator at an in-going temperature of 68°C and an outgoing temperature of about 40°C. The evaporated milk was collected in a buffer tank at about 40°C under constant stirring.

- then evaporated milk was spray dried using a spray dryer. Ingoing product temperature was about 74°C while inlet air was in the area of 180°C. Outlet air temperature was set either to

80°C by adjustment of product mass flow. The final WPNI was of 6,93 mg N/g.

Example 2 : milk powder preparation according to the invention

A milk was prepared according to the process described in Example 1 except that before heat treating milk at 74°C during 30 seconds in a plate heat exchanger, the pH of standardized milk was increased from 6,7 to 7,2 by adding NaOH. The final WPNI was of 7,13 mg N/g.

Example 3 : preparation of foamed milks

Foamed milks were prepared from the milk powders of Example 1 and 2 according to the following process.

9,7 g of powder was dissolved in 100 ml of water at ambient temperature by gentle stirring in order to reconstitute milk. Then 100 ml of reconstituted milk was heated at 85°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 and several corresponding mixing bowls in order to prepare different beverages.

In the present example, since milk was not reconstituted inside the mixing bowl of the dispenser but prepared in a simple container 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 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.

The foamability and the texture of the foamed milk 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 :

- 35 mm cylindrical aluminium probe,

- 1 mm/s penetration speed,

- 20 mm 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 and 2. Foamed milk prepared with Foamed milk prepared with powder of Example 1 powder of Example 2

Foamability (ml) 127 140

Texture/max force (g) 9,4 10,5

The results illustrate how the foamed milk prepared with the powder of Example 2 according to the present invention presents both increased foamability and foam texture compared to the foamed milk prepared with the powder of Example 1 .

Claims

1. Process for preparing a milk component from raw milk, said process comprising at least the steps of standardising raw milk and then heating standardised milk, wherein :

2. Process according to Claim 1 wherein the conditions for heating the standardized milk correspond to the heating conditions resulting in achieving a low heat milk powder having a whey protein nitrogen index (WPNI) greater than 6,0 mg N/g

3. Process according to Claim 1 wherein the conditions for heating the standardized milk correspond to the heating conditions resulting in achieving a medium heat milk powder having a whey protein nitrogen index (WPNI) greater comprised between 4,0 and 5,99 mg N/g.

4. Process according to any one of the precedent claims wherein milk is heated at a temperature of at least 74 °C during at least 10 seconds.

5. Process according to any one of the precedent claims wherein the pH of standardized milk is raised by adding at least one food agreed component able to raise said pH.

6. Process according to the precedent claim wherein the component is selected in the list of the following components : phosphate salts, citrate salts, hydroxides, carbonates and combinations thereof.

7. Process according to any one of the precedent claims wherein further to the heating step milk is concentrated to produce a milk concentrate.

8. Process according to any one of Claims 1 to 3 wherein further to the heating step milk is concentrated and then dried to produce a milk powder.

9. Milk component susceptible to be obtained from the process of any one of Claims 1 to 8.

10. Process for preparing a foamed based milk beverage comprising the step of whipping the milk susceptible to be obtained from the process of any one of Claims 1 to 8, optionally with water.

1 1 . Process according to Claim 10 wherein the step of whipping is implemented with a mechanical whipper inside a whipping chamber.

12. Process according to Claim 10 wherein the step of whipping is implemented with at least one water jet, said at least one water jet hitting the milk and frothing it.

13. Process according to Claim 1 1 or 12 wherein the milk component is a milk concentrate or a milk powder and it is whipped with water presenting a temperature of at least 50 °C.

14. Process according to any one of Claims 10 to 13 wherein further to the step of whipping the resulting foamed milk is mixed with another beverage component.