GB2566289A - Method of preparing milk from milk powder - Google Patents

Abstract

A method of reconstituting milk powder comprises (a) adding milk powder and water to a container; and (b) mixing the milk powder and water together in the container whilst substantially excluding air from the mixture and avoiding the formation of an air vortex extending into the mixture. The method may include a step of processing the mixture to remove a foam portion. The container may include a mixer head which may rotate at 4000 rpm or less. The air may be displaced from the container after step (a) by providing a cover substantially adjacent to the water in the container and sealing the container prior to step (b). The advantage is a reconstituted milk from powder without an unpleasant off taste. Also disclosed is a milk powder formulation comprising at least one milk powder and an additive starch.

Description

METHOD OF PREPARING MILK FROM MILK POWDER

The present invention relates to a method of preparing milk from milk powder, and also to a milk powder suitable for use in that method.

BACKGROUND TO THE INVENTION

Milk is used across the food industry, both domestically and commercially. It is sterilised prior to use (often via pasteurisation), typically at a large processing plant, before being distributed for sale/use. Significant transportation costs are incurred before and after processing, due to the weight and volume of the milk, and the fact that it must be kept cold at all times to avoid spoiling.

The transportation time involved prior to pasteurisation and later consumption/use cuts into the shelf-life of the milk. Even when refrigerated, milk does not keep for long, and the availability of milk is not guaranteed in more remote areas, particularly in countries with hot climates. All of these factors contribute to significant milk waste when the product exceeds its ‘use by’ date.

To help address these problems, various alternative milk products have been developed for the market, such as condensed milk and evaporated milk. Microfiltration, ultra-hightemperature (UHT) processing or high-temperature/short time (HTST) pasteurisation can also prolong the useable life of milk, provided it remains unopened. Milk powders are also available, such as Marvel(RTM) milk powder, but the milk in (or made from) these products does not taste the same as standard pasteurised milk, either due to artificial sweetening to disguise the taste of the milk, or as a result of the additional processing and the inclusion of air (particularly oxygen, which can cause an off-taste). Converting a milk powder back into milk produces excessive foam, but it must still be possible to foam the milk after conversion, to create a latte for example. These factors are significant and put off some customers (for example coffee shops) and consumers from buying or using these products.

It is an object of the present invention to reduce or substantially obviate the aforementioned problems.

STATEMENT OF INVENTION

According to a first aspect of the present invention, there is provided a method of reconstituting milk powder, the method comprising the steps of

a) adding milk powder and water to a container;

b) mixing the milk powder and water together in the container, whilst substantially excluding air from the mixture and avoiding the formation of an air vortex extending into the mixture.

This method substantially avoids incorporating gases (particularly oxygen, which can cause an off-taste) from the air into the milk formed from the powder. The surface area of the water is minimised during mixing by avoiding the creation of a deep sustained vortex. By substantially preventing air from being mixed into the milk during reconstitution, the smell and flavour of the resulting milk is much improved relative to conventional reconstituted milk, to the extent that it is more or less indistinguishable from the smell and flavour of standard pasteurised milk.

A milk powder is a powder formed from milk which has been dehydrated, removing water to leave the other component parts. A milk powder can be derived from a dairy' source, such as cow’s milk, or a non-dairy or vegetarian source, such as soya milk. Reconstituted milk is liquid milk that has been prepared from a milk powder. Within this document, references to milk are to be interpreted as meaning milk which has not been dehydrated and then reconstituted, unless the context implies otherwise.

The method may further include the step of processing the mixture to remove a foam portion of that mixture. The liquid part of the mixture may be drained into a different container. The foam may be removed by sieving the mixture. The milk mixture formed in step (b) may be decanted to separate a liquid part of the mixture from the foam part.

The foam created during mixing of the milk powder is very stable, and the bubbles do not collapse quickly on their own after mixing has been stopped. Destabilising and bursting the bubbles can reduce the volume of milk mixture lost as foam. Sieving the mixture has the advantage of removing the foam as well as potential contaminants or agglomerations not broken up during mixing. Decanting the liquid allows the foam to be isolated for other potential uses.

The container may include a mixer head. The mixer head may be used to perform mixing in step (b) at a rate of 4000 rpm or less. The rate may be around 2000 rpm. Preferably, the rate may be at or around 2200 rpm.

Mixing at these rates is sufficient to reconstitute the milk powder with water to make milk in around a couple of minutes. This is viable for commercial application in a coffee shop, for example, without creating undue delay. Advantageously, mixing in this way greatly reduces the volume of foam produced during mixing.

After step (a), air may be displaced from the container by providing a cover substantially adjacent to the water in the container, which is preferably sealed prior to performing step (b).

By providing a cover which occupies the empty portion of the container (i.e. the portion not containing ingredients to be mixed), the container contains insufficient air to create large amounts of foam during mixing. The seal prevents the ingress of air into the container during mixing, which may otherwise replace residual air in the container if drawn into the mixture.

The container may be sealed and air evacuated from the container prior to performing step (b).

By removing air from an empty portion of the container (i.e. the portion not containing ingredients to be mixed), air cannot be extensively incorporated into a foam during mixing. The seal maintains the lower pressure or vacuum inside the container during mixing.

The milk powder may include a frothing agent. The method may include the step of processing the mixture to produce a froth. Preferably, the processing step includes heating the mixture.

Using a frothing agent can ensure that bubbles in the milk froth are more stable, and affects the distribution of bubble sizes. The flavour of the milk is also affected by frothing, and creating a more stable froth is advantageous for some coffees, for example.

An additive comprising starch may be provided in the container in step (a). The additive is preferably added to the milk powder after preparation of the milk powder from liquid milk, but before it is reconstituted into milk. The starch may be provided as a starch powder.

The starch is both thermally and mechanical responsive. When the prepared milk is heated, such as during frothing, the starch stabilises the bubbles in the froth. This is useful for making a latte, for example.

The method may include the step of draining a liquid portion of the mixture (formed in step (b)) from an outlet at the lower end of the container. The mixture may be allowed to stand for a period of time before isolating the liquid portion.

By draining liquid from the container rather than pouring it out, this mitigates incorporation of air into the liquid part of the reconstituted milk. Any foam which was formed by the inclusion of residual air in the container will predominantly be on top of the liquid milk, so draining also ensures that the foam is not transferred with the liquid portion of the milk.

The method may include the step of testing the conductivity of the mixture in step (b).

When preparing reconstituted milk, it is possible that the ratio of water to milk powder could be incorrect. Conventionally, milk quality is tested via the freezing point depression test. This is used to check whether milk has been watered down, but freezing the milk prepared by a barista, for example, is commercially impractical. By testing the conductivity of the reconstituted milk, and checking it falls within an acceptable range, the quality of the milk can be verified prior to use, to check that the user has not added too much or too little water.

Preferably, the conductivity of the mixture may be tested during mixing. If the conductivity of the mixture reaches a predetermined value, or remains within a predetermined range for a period of time (e.g. 5 or 10 seconds), this can indicate that the mixture is ready. The results of the conductivity test may be used to automatically cease mixing at the minimum necessary time for mixing. This may in turn minimise the amount of foam created during reconstitution.

Step (a) of the method may involve:

i) adding a first portion of water to the container, ii) adding the milk powder to the first portion of water, and iii) adding a second portion of water to the container.

Preferably, substantially the same amount of water is used in both steps (i) and (iii). This allows for a reduced mixing time when reconstituting the milk powder into milk.

According to a second aspect of the present invention, there is provided a milk powder formulation comprising at least one milk powder, and an additive comprising starch.

This provides a formulation suitable for use in the method of the first aspect of the invention. The starch molecules respond to mechanical stress during mixing in a way that improves the consistency of milk which is reconstituted from the formulation. This leads to reconstituted milk which tastes much more similar to normal milk.

The powder formulation can be stored in much less space (both refrigerated and at ambient temperature) than that required for liquid milk. It is also less expensive to transport the dry formulation to a site than liquid milk, because then fuel is not required to move large volumes of water as part of the milk. This is both commercially preferable and more environmentally friendly.

Unlike milk reconstituted from conventional milk powder, people are essentially unable to differentiate between normal milk and the reconstituted milk made using the formulation (and using the method according to the first aspect of the invention), overcoming the main barrier to widespread use of milk powder by consumers.

The starch component may comprise about 5% or less by weight of the formulation (i.e. the powder mass). Preferably, the starch component comprises about 1% by weight of the formulation. The starch component may comprise around 0.5% by weight of the formulation. The granules of starch may be of similar size to the granules of milk powder.

The amount of starch is selected to provide a satisfying texture to the liquid milk prepared from the powder. This ensures that the mouthfeel of the reconstituted milk closely mimics that of normal milk, without the milk feeling too thin or too ‘starchy’.

The milk powder may include a dairy-based milk powder. The milk powder may include a non-dairy-based milk powder. The milk powder may include a vegetablebased powder. Soya milk powder, coconut milk powder, rice milk powder and almond milk powder are some examples of powders which can be used.

The milk powder may include a blend of at least two milk powders. Each milk powder may have been prepared using different heat treatments. One powder may have been prepared via a low temperature heat treatment, and the other prepared via a high temperature heat treatment. The blend may include dairy and/or non-dairy milk powders.

Using a blend of powders can result in reconstituted milk that is even more similar to normal milk. For example, milk powder prepared from milk which has undergone thermization (low heat treatment) retains more of its natural flavour. Higher temperature processing of another milk powder sterilises it more effectively. Using a blend of powders which includes milk powders from low- and high-temperature heat treatment improves the smell and flavour of the reconstituted milk without significantly affecting the shelf-life of the powder.

The milk powder formulation may further comprise one or more additives selected from the following: one or more flavourings; one or more texturants; dietary fibre; one or more stabilisers; one or more vitamins and/or trace elements; one or more protein powders; one or more yoghurt-derived powders; one or more medicines.

A texturant can improve the mouthfeel of the resulting milk. In the correct proportion, starch is a suitable texturant, thickening the milk and improving its stability. Adding vitamins or medicines to the milk powder can make it easier for a person to take a dose of either, which is more palatable than swallowing a tablet.

On a percentage basis, milk normally has around 7 parts water to 1 part other components. Preferably, when reconstituting milk from the milk powder formulation, a weight ratio of around 10:1 (water to powder formulation) is used.

Milk comprising a milk powder formulation according to the second aspect of the invention may be provided. The milk may be a portion or serving of milk, for use in a hot beverage, for example. This would typically be prepared on a millilitre (ml) or litre (1) scale, suitable for ‘worktop’ or ‘counter’ preparation. The milk may be a batch of milk prepared on a larger scale (tens of litres or more), if reconstituted for distribution in the immediate locality, for example.

A container comprising a milk powder formulation (or milk reconstituted from a milk powder formulation) according to the second aspect of the invention may be provided. The container may be a packet or sachet for smaller volumes of the milk powder formulation. The container may be a jar for larger volumes of the milk powder formulation. The container is preferably sealed for preventing contamination during long-term storage.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings, in which:

Figure 1 shows a flowchart of the process used to prepare milk from a milk powder formulation according to the first aspect of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Figure 1, an exemplary embodiment of the process for reconstituting milk powder into milk is shown. Small-scale (or gram-scale) reconstitution of milk from a milk powder formulation is described in the following sections. However, it will be appreciated that the method could also be used for industrial-scale reconstitution of milk (e.g. for reconstituting tens or hundreds of litres of milk per batch).

In a first step (10), a quantity of a milk powder formulation is added to a container. In a next step (12), a quantity of water is added to the milk powder in the container. The volume of water used can be selected according to the amount of powder used, i.e. predetermined quantities of powder and water. The container can have a ‘fill’ level indicator or mark to indicate the amount of water to add.

The milk powder formulation in this embodiment includes a blend of two dairy-based milk powders. The first milk powder was prepared using steps including a low-medium temperature treatment process. The second milk powder was prepared using steps including a high temperature treatment process. Equal weights of the two powders are provided in this embodiment. The blend of powders also includes a starch powder. The starch powder constitutes 1% of the weight of the formulation in this embodiment.

Once the ingredients have been added to the container, the container is sealed. The seal is airtight for substantially isolating the milk powder and water from air during mixing.

In one embodiment, sealing the container (14a) involves using a cover or lid which is adapted to fill the empty volume of the container, displacing all or substantially all of the air out of the container. In this case, the quantities of water and powder are selected to fill the container by a predetermined volume. The predetermine volume is less than the full volume/capacity of the container. The volume of the lid and the predetermined volume of the unmixed milk powder and water should then equal or almost equal the volume of the container. In practice, a gap of up to around 2-3cm may be present between the water surface and the lid. However, the water surface should ideally be in contact with an inner surface of the lid.

In another embodiment, the lid or container has a port with a valve. Sealing the container (14b) then involves using a vacuum-generating system or pump connected to the port to evacuate air from inside the container. Whilst closed, the valve prevents gases from re-entering the container through the port, for maintaining a vacuum or lowpressure environment within the container during mixing.

In each embodiment, the next step (16) is to mix the contents of the container. A mixer head is provided in the base of the container to effect this. The mixer head can be selected to generate a low level of shear during mixing. In this embodiment, the mixer head is a Silverson(RTM) type of mixer head. Chopper and blender type heads are less advantageous because they create more foam.

Activating the mixer head reconstitutes the milk powder into milk by gently mixing the ingredients together. The mixing time to fully reconstitute the milk is up to around 2 minutes, depending on the speed of mixing. A typical mixing speed for achieving this would be around 2000 to 4000 rpm. This avoids the creation of a substantial air vortex extending into the mixture. An air vortex is considered to be a swirl of air that extends into the mixture during mixing, substantially increasing the contact surface area between the mixture and the air.

In this embodiment, mixing is done at 2200rpm. In other embodiments, intermittent mixing (mixing in short bursts of time) and/or reversing the direction of the mixer head can be used to reconstitute the milk. Periodic mixing allows reconstitution of the milk powder without forming a sustained vortex of air in the mixture. An air vortex in the mixture can be considered as sustained when it lasts for more than around 5 to 10 seconds in a single instance. Alternatively, an air vortex in the mixture can be considered as sustained when the proportion of time that it is present during mixing is at least 20% of the time spent mixing.

Once the powder has been fully dispersed into the liquid, the mixer head is stopped. The mixture typically has a liquid portion (milk) and a foam portion, although the foam portion is minimal. In order to test whether the milk is fully reconstituted, a conductivity sensor can be used to probe the mixture. If the reading is sufficiently similar to a known predetermined value, then no further mixing is required. If the conductivity value is too dissimilar, then either too much or too little water has been added, and the user (e.g. a barista) can prepare a different batch. In some scenarios, it may be preferable to create a batch of milk which is more concentrated or dilute, according to the intended use of the milk for example.

The cover can then be opened or removed, allowing air back into the container. If the mixture is allowed to rest, the foam portion can increase in volume. If air has been evacuated from the container, the valve may be opened first before opening the lid.

The liquid portion is isolated (18) or separated from the foam portion by draining it from a drain at the base of the container. The foam can alternatively be removed by pouring the milk through a sieve. Another alternative is to mechanically collapse the foam. The liquid part (i.e. the milk) can then be used as desired, either alone or in combination with other food and/or drink. The starch powder improves the mouthfeel of the milk if ingested as-is, but also aids frothing if used in a cappuccino, for example.

In some embodiments, a water to milk powder weight ratio of approximately 10:1 is used. For example, in one batch, 455ml of water and 45g of milk powder formulation was used. This made approximately 470ml of milk, once foam had been removed.

The method tends to be more efficient when reconstituting low volumes of milk from powder, i.e. small-scale reconstitution performed in a domestic or commercial kitchen. Reconstituting low volumes of milk minimises the amount of foam created, thereby reducing the amount of milk powder lost as foam.

In one embodiment, 5 litres or less of milk may be reconstituted. In another embodiment, 4 litres of milk may be reconstituted. In a further embodiment, 3 litres of milk may be reconstituted. In yet another embodiment, 2 litres of milk may be reconstituted. In yet another embodiment, 1 litre of milk may be reconstituted.

It will be appreciated that other amounts of milk may also be prepared according to imperial units, such as one or more of the following: half a pint of milk; 1 pint of milk; 2 pints of milk; 4 pints of milk. Imperial units are deliberately recited here (as opposed to metric approximations of these amounts) because milk is generally sold in pints, in the UK, for example.

In some embodiments, the milk is reconstituted concurrently with the preparation of another food or drink item. For example, it may be preferable to create a milkshake in this way to save time. The milk powder formulation is also suitable for preparing other food items, including but not limited to one or more of the following: a smoothie, a tea, a coffee, a hot chocolate, a cream, a yoghurt, a cooking sauce, a dessert, a sports drink, and a medicinal drink.

It will be appreciated that other embodiments may differ from the foregoing. For example, in some embodiments, half of the water is provided in the container first, followed by addition of the powder, and then addition of the remaining portion of water. Other liquids which are substantially comprised of water are also envisaged for use in the method. A suitable example of an aqueous liquid for use in the process includes milk, for example. Different ratios of liquid to milk powder may be required where liquids other than water are used. Different ratios may also be required depending on the amount(s) of additive(s) in the formulation.

The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.

Claims (19)

1. A method of reconstituting milk powder, the method comprising the steps of:

a) adding milk powder and water to a container;

b) mixing the milk powder and water together in the container, whilst substantially excluding air from the mixture and avoiding the formation of an air vortex extending into the mixture.

2. A method as claimed in claim 1, further including the step of processing the mixture to remove a foam portion thereof.

3. A method as claimed in claim 1 or 2, in which the container includes a mixer head, and mixing in step (b) is performed using the mixer head at 4000 rpm or less.

4. A method as claimed in any of claims 1 to 3, in which air is displaced from the container after step (a) by providing a cover substantially adjacent to the water in the container, and the container is sealed prior to performing step (b).

5. A method as claimed in any of claims 1 to 3, in which the container is sealed and air is evacuated from the container prior to performing step (b).

6. A method as claimed in any preceding claim, in which the milk powder includes a frothing agent, and the method includes the step of processing the mixture to produce a froth.

7. A method as claimed in any preceding claim, in which an additive comprising starch is provided in the container in step (a).

8. A method as claimed in any preceding claim, further including the step of draining a liquid portion of the mixture formed in step (b) from an outlet at a lower end of the container.

9. A method as claimed in any preceding claim, further including the step of testing the conductivity of the mixture in step (b).

10. A method as claimed in any preceding claim, in which step (a) involves:

i) adding a first portion of water to the container, ii) adding the milk powder to the first portion of water, and iii) adding a second portion of water to the container.

11. A milk powder formulation comprising at least one milk powder, and an additive comprising starch.

12. A milk powder formulation as claimed in claim 11, in which the starch comprises about 5% or less by weight of the milk powder formulation.

13. A milk powder formulation as claimed in claim 11, in which the starch comprises about 1% by weight of the milk powder formulation.

14. A milk powder formulation as claimed in any of claims 11 to 13, in which the at least one milk powder includes a dairy-based milk powder.

15. A milk powder formulation as claimed in any of claims 11 to 14, in which the at least one milk powder includes a non-dairy-based milk powder.

16. A milk powder formulation as claimed in any of claims 11 to 15, including a blend of at least two milk powders.

17. A milk powder formulation as claimed in claim 16, in which the first milk powder was prepared using low temperature treatment, and the second milk powder was prepared using high temperature treatment.

18. Milk comprising the milk powder formulation of any of claims 11 to 17.

19. A container comprising the milk powder formulation of any of claims 11 to 17, or comprising milk as claimed in claim 18.