WO2014069994A1

WO2014069994A1 - A method and system for preparing a foamed food product

Info

Publication number: WO2014069994A1
Application number: PCT/NL2013/050760
Authority: WO
Inventors: Wiebe Nicolaas Van Druten; Maarten Joannes Botman
Original assignee: Friesland Brands BV
Current assignee: FrieslandCampina Nederland BV
Priority date: 2012-10-29
Filing date: 2013-10-29
Publication date: 2014-05-08
Anticipated expiration: 2015-04-29
Also published as: NL2009713C2

Abstract

A method and system for preparing a foamed food product A method for preparing a foamed food product comprises the step of supplying a liquid food product to a microfiltration device comprising a microfiltration surface (12) having gas transmissive pores. A gas supply (42) is connected to the microfiltration device, gas is supplied via the transmissive pores to the liquid food product flowing over the microfiltration surface, and the gas supply is disconnected from the microfiltration device. Between connection and disconnection of the microfiltration device from the gas supply gas is continuously supplied through the gas transmissive pores of the microfiltration surface even in the situation where no foamed food product is made. A system for preparing a foamed food product is configured for carrying out such a method and comprises a product preparation apparatus, an assembly (1) comprising concentrated liquid food product, a microfiltration device and a pressurized gas source configured for detachable connection to the microfiltration device. The apparatus comprises an operating device for continuously activating said gas pressurizing means between its connection to and disconnection from the microfiltration device.

Description

Title: A method and system for preparing a foamed food product

FIELD OF THE INVENTION

The invention relates to a method for preparing a foamed food product, for instance, a milk product, milk, foam, cream or aerated dessert, or a different product.

Such a method is known from WO-Al-2011/028117. According to WO-Al-2011/028117 an assembly, e.g. containing a product, such as milk is operatively connected to an operating apparatus for e.g. producing and discharging milk foam or froth. The assembly comprises a holder provided with a fluid entrance for supplying fluid coming from a fluid supply means of the operating apparatus to an inner space surrounded by the holder for bringing this space containing the milk to a desired milk expelling pressure for dispensing the milk via discharge means. This discharge means comprises a microfiltration device for foaming the milk by introducing a gas, such as air via the microfiltration device to the milk flowing through the microfiltration device. The operating apparatus comprises cooling means to cool the milk in the disposable assembly for preventing potential degradation of the milk.

Furthermore, for dispensing a hot product the operating apparatus can comprise a steam generator or hot water supply connected to a valve device positioned between the holder and the microfiltration device to heat milk expelled from the holder. In addition the valve device can be set such as to only pass the steam for cleaning the microfiltration device and optional devices downstream of the microfiltration device.

Although highly user-friendly, such a method, especially when preparing a foamed product from milk or another perishable liquid food product, requires additional measures for preventing decay of the product, such as cooling during transport, and also a cooling device in the operating apparatus, which require a relatively large amount of energy. Furthermore, since milk is highly perishable, in the method of WO-Al-2011/028117 frequent cleaning is required. This frequent cleaning is performed by using steam and thus is costly not only in view of e.g. the energy used to produce the steam for cleaning, but also in view of the down-time of the operating apparatus during such cleaning. In addition a robust mechanical construction of the preparation apparatus is needed which can resist the high stresses coming along with the production of steam, as a result of which the operating apparatus will be relatively costly. SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method for preparing a foamed food product with which in particular a high standard regarding hygiene can be realized with an at least substantial reduction of cleaning. It is a further object of the invention to provide a method for preparing a foamed food product with which in particular a foamed product without a cooking taste can be obtained in a particularly efficient manner, with relatively inexpensive and durable means using only a relatively low amount of energy.

To this end, the invention provides a method for preparing a foamed food product, said method comprising the step of connecting a microfiltration device comprising a microfiltration surface having gas transmissive pores and having a product inlet and a product outlet to a gas supply for supplying gas through the gas transmissive pores of the microfiltration surface, said product outlet being arranged for discharging foamed product, the step of supplying a liquid food product to the microfiltration device, the step of supplying gas to the liquid food product flowing from the product inlet to the product outlet over the microfiltration surface, and the step of disconnecting the microfiltration device from the gas supply, wherein the method comprises the step of continuously supplying gas through the gas transmissive pores of the microfiltration surface between connection of the microiiltration device to the gas supply and disconnection of the microfiltration device from the gas supply even in the situation where no foamed food product is made. In this manner liquid product can flow over the filtration surface from the product inlet to the product outlet in order to be provided with gas in a sterile manner. Preferably, the microfiltration device comprises a tube having a tubular surface as microfiltration surface, said tube comprising a product entrance opening as the product inlet for receiving said liquid food product, a foamed product outlet opening as the product outlet for discharging foamed product and a product feed-through channel between said product entrance opening and said foamed product outlet opening, wherein the method further comprises the step of connecting the microfiltration device to a gas supply for supplying gas through the gas transmissive pores of the tubular surface, the step of supplying gas to the liquid food product flowing through the product feed-through channel, and the step of disconnecting the microfiltration device from the gas supply, wherein the method comprises the step of continuously supplying gas through the gas transmissive pores of the tubular surface between connection of the microfiltration device to the gas supply and disconnection of the microfiltration device from the gas supply even in the situation where no foamed food product is made.

In a further aspect of the invention a method for preparing a foamed food product is provided comprising the step of supplying a liquid food product to a microfiltration device comprising a tube with a microfiltration surface, said tubular surface having gas transmissive pores, said device being provided with a product entrance opening for receiving said liquid food product, a foamed product outlet opening for discharging foamed product and a product feed-through channel between said product entrance opening and said foamed product outlet opening, the step of connecting the microfiltration device to a gas supply for supplying gas through the gas transmissive pores of the tubular surface, the step of supplying gas to the liquid food product flowing through the product feed-through channel, and the step of disconnecting the

microfiltration device from the gas supply, wherein the method comprises the step of continuously supplying gas through the gas transmissive pores of the tubular surface. In this manner gas is constantly supplied to keep the microfiltration device under constant sterile (slight) overpressure. This decreases the risk of growth of microorganisms significantly which can result in a liquid food product (in the holder) that will maintain its sterility over extended periods of time, even under ambient conditions. Since the

overpressure is a slight overpressure, it can be produced by relatively low cost devices and with a relatively low amount of energy. If the condition of sterile gas at overpressure is maintained only during a part of the total time period in which the microfiltration device is connected to the gas supply of e.g. a product preparation apparatus, the time period within which the liquid food product maintains its sterility will reduce but can still be longer than compared with the situation in which no sterile overpressure is used at all. In comparison with the energy consumption of a method disclosed in WO-Al-2011/028117, the energy consumption of the present inventive method is significantly reduced, while at the same time a product with a more appealing taste can be provided at a strongly reduced cleaning frequency. Consequently, a very hygienic preparation of foamed food products can be realized.

Preferably the gas is an inert gas, for example containing air, helium, nitrogen or carbon dioxide.

A stable foamed product is preferably obtained when the step of supplying said gas to the microfiltration device comprises the step of supplying said gas at a constant gas flow, preferably via a reducing valve, in particular via a small orifice. Such a constant gas flow improves the sterile conditions at which the method can be performed. In addition, in this manner the

generation of foamed product has proven to be less dependent on fluctuations in flow of product through or over the microfiltration device. The generation of foamed product has proven to be even more independent on fluctuations in flow of product through or over the microfiltration device when the diameter of the orifice is chosen such as to create a (near) supersonic gas flow through the orifice and/or the diameter of the orifice is chosen such that in dependence on the morphology and dimensions of the microfiltration device a required effective pressure over the filtration surface of the filtration device for generating a foamed product is obtained.

In a further embodiment of a method according to the invention, in which the method comprises the step of supplying gas to the microfiltration device under an overpressure of 0.101 to 0.15 MPa and with a gas flow of 0.05 to 1.2 Nliters/min, preferably 0.05 to 0.4 Nliters/min, more preferred 0.15 to 0.4 Nhters/min, most preferred 0.2 to 0.3 Nhters/min, not only a very reproducible, stable foamed product can be prepared using a relatively low amount of energy, but also such a relative low overpressure appears to be sufficient to prevent degradation of the quality of the liquid food product.

In a further embodiment of a method according to the invention, the step of supplying a food product to the microfiltration device comprises providing an amount of concentrated liquid food product and mixing said concentrated liquid food product with an amount of water to obtain a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content, which liquid food product is supplied to the microfiltration device. By using a concentrated liquid food product, it is possible to store the food product for an extended period of time at ambient temperatures, i.e. without cooling, without degradation of the concentrated liquid food product. Preferably the water is heated before it is mixed with the concentrated food product. In particular when dispensing a hot product using heated water before it is mixed with the concentrated liquid food product, the hot product can be prepared with a relatively low amount of energy and without a cooking taste which appears to be quite appealing for at least some of the consumers. Preferably a method according to the present invention comprises the steps of providing an eductor with a mixing chamber, providing a water conduit for heated water to the eductor, providing a food product conduit for the concentrated liquid food product to the eductor, supplying heated water to the inlet of said eductor such that suction created at the eductor by the flow of heated water entrains concentrated liquid food product into the chamber where said concentrated liquid food product is mixed with water. The use of an eductor makes it possible to on the one hand in an simple manner add such an amount of water to the concentrated liquid food product that after mixing with the water a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content, also called an unconcentrated liquid content herein, is obtained. This provides the possibility to prepare a foamed food product having a particularly pleasant taste sensation. On the other hand the eductor can be used simultaneously to entrain concentrated liquid food product out of a holder by the suction provided by the water flowing through the eductor, so that no additional devices are necessary to expel the concentrated liquid food product from a holder.

In a preferred embodiment of a method according to the invention, the method comprises the steps of storing the concentrated liquid food product at ambient temperature and of heating water to such a temperature and supplying said heated water at such a pressure to the eductor that the concentrated liquid food product is entrained at such an amount that after mixing with the heated water a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content is obtained. In this manner, it is possible to obtain a liquid food product with a normal amount of dry matter, or normal amount of liquid content from a concentrated liquid food product by just adjusting the temperature and the pressure of the supply of water. In this particular advantageous use the eductor makes it possible to add such an amount of water to the concentrated liquid food product that after mixing with the water a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content, also called an unconcentrated liquid content herein, is obtained. This provides the possibility to prepare a foamed food product having a particularly pleasant taste sensation if the product is intended for consumption. The concentrated liquid food product contained within the disposable assembly can be (fruit) juice/drink, an alcohol-containing drink or drink base, for instance, beer or wine, a dairy or dairy-based drink, for instance, a whey drink or permeate-based drink, (milk) shake, chocolate drink, (drinking) yoghurt, sauce, ice cream or dessert, juice, the invention is in particular advantageous when the concentrated liquid food product is concentrated milk. The product can further comprise, for instance, vegetal or animal fat or oil, a thickener, sugar, sweeteners, flavoring, coloring and/or the like, and/or various other ingredients. The product could even comprise, for instance, a non-consumable product, a body care product, a hair treating agent, or the like. When as concentrated liquid food product concentrated milk is used comprising 20 wt% dry matter to 30 wt% dry matter, preferably 23 - 27 wt% dry matter, whereas unconcentrated milk, i.e. milk with a normal liquid content, comprises 10 wt% dry matter, it is particularly advantageous to use a method according to the invention wherein water is heated to a temperature in a range generally between 60°C to 110°C, preferably 90°C to 98°C, more preferred 95°C to 98°C and wherein the heated water is pressurized to a range between 0.11 and 2.5 MPa, preferably 0.2 - 0.4 MPa and then is supplied to the water inlet of the eductor. In this manner with a relatively low amount of energy a heated milk product having a temperature in a range generally between 50°C to 85°C, more preferred between 60°C and 70°C, most preferred in a range between 65°C to 68°C, can be produced without the "cooked milk taste".

In a further embodiment of a method according to the invention, the method comprises the use of gas transmissive pores having a pore size in the range of 0.05-10 microns, in particular a pore size of at least 0.1 micron and less than 2 microns, wherein a length of the wall is between 1 cm to 6 cm, preferably 1.5 cm to 5 cm, more preferred 1.5 cm to 3 cm, most preferred 1.6 - 2.0 cm measured in a product flow direction of product during use flowing along that wall, parallel to that wall, wherein the pore size is preferably in the range of 0.2 micron to 1.5 microns. In case the microfiltration device comprises a tube having a tubular surface, the outside diameter is then preferably between 1 mm to 10 mm, more preferred 1.5 mm to 8 mm, further preferred 2 mm to 5 mm, most preferred 3 mm amongst other things dependent on the desired flow rate of the product. In this manner, when liquid product is supplied to the microfiltration device, it is possible to inject gas in the product in a sterile manner, since a microfiltration device with such transmissive pores, and in particular when manufactured from a hydrophobic material, functions as a HEPA (High-Efficiency Particulate Air) filter, leading to a very hygienic manner of preparing the foamed food product. In particular when preparing a milk foam product, the use of such a microfiltration device for adding gas to the product can provide a highly stable, attractive foam, in particular of constant quality, in a relatively simple manner. With various foamable products, moreover, a particularly high "overrun" (also sometimes called "degree of aeration") can be obtained.

In this regard it is observed that the volume increase of a product after foaming is often denoted with the term "overrun" or "overrun

percentage". The overrun percentage gives the volume increase of the product P after foaming with respect to the volume of the non-foamed product and can be represented as:

W_p - W_s

Overrun = x 100%

W_s wherein W_p represents the mass of a fixed volume of unfoamed product and W_s the mass of the same volume of foamed product (inclusive of any product drained therefrom). Thus, an overrun percentage of 100% means that a volume of 100 ml after dispensing has increased to 200 ml. The present invention also relates to a system for preparing a foamed food product, configured for carrying out a method according to any one of the preceding claims, said system comprising:

- a product preparation apparatus for preparing said foamed food product; and

- a disposable assembly comprising:

- a holder containing a concentrated liquid food product;

- an eductor;

- a microfiltration device;

- a transfer tube connecting an outlet of said eductor with the inlet of said microfiltration device;

- a concentrated liquid food product tube connecting said holder to a concentrated liquid food inlet of said eductor;

- a water inlet tube connecting a water inlet of said eductor with a water connection of the disposable assembly, said water connection being configured for connection to an external source of water under pressure, said liquid food inlet of said eductor being positioned between said water inlet and said outlet of said eductor;

- a gas inlet tube connecting said microfiltration device to a gas connection of said disposable assembly, said gas connection being configured for connection to an external source of gas; and

- a foamed food product outlet tube connecting the outlet of the microfiltration device to an outlet connection of the disposable assembly for discharging a foamed food product created by the microfiltration device from the disposable assembly;

said product preparation apparatus comprising a source of pressurized gas, said source of pressurized gas being configured for detachable connection to the gas connection of said disposable assembly for supplying pressurized gas to the gas inlet of the microfiltration device, said product preparation apparatus further comprising an operating device for controlling the operation of the source of pressurized gas, a sensor for detecting connection and disconnection, respectively, of the source of pressurized gas to the gas connection of said disposable assembly and for supplying a signal indicative of said connection and disconnection, respectively, to the operating device, said operating device being configured for continuously activating said source of pressurized gas between said detected connection to and said detected disconnection from said gas connection of said disposable assembly. In this manner not only sterile gas can be supplied to the product via the

microfiltration device when preparing a foamed food product, but also sterile gas is constantly supplied to keep the system under constant sterile (slight) overpressure even in the situation where no foamed food product is made. This decreases the risk of growth of microorganisms significantly, which can result in a concentrated liquid food product that will maintain its sterility over extended periods of time, even under ambient conditions. Preferably the product preparation apparatus is free of any cooling devices for the disposable assembly. In addition by using a assembly, preferably a disposable assembly for a concentrated liquid food product, it is possible to store the disposable assembly for an extended period of time at ambient temperatures, i.e. without cooling, without degradation of the concentrated liquid food product. In particular the use of an eductor makes it possible to add such an amount of water to the concentrated liquid food product that after mixing with the water a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content, also called an unconcentrated liquid content herein, is obtained. This provides the possibility to prepare a foamed food product having a particularly pleasant taste sensation if the product is intended for consumption. On the other hand the eductor can be used to entrain concentrated liquid food product out of the holder by the suction provided by the water flowing through the eductor, so that no additional devices are necessary to expel the concentrated liquid food product from the assembly. In this way, it is possible that a product preparation apparatus or operating apparatus in which the disposable assembly is to be used can be manufactured relatively compactly and relatively inexpensive. In addition, such a disposable assembly can contain the concentrated liquid food product very hygienically, e.g. in case the assembly is filled aseptically with the concentrated liquid food product.

In an embodiment of a system for preparing a foamed food product according to the invention, the system comprises means for providing a constant gas flow to the microfiltration device, said means preferably being formed by a reducing valve. Preferably the source of pressurized gas is configured to supply pressurize gas at a slight overpressure, preferably in a range between 0.101 to 0.15 MPa, and the source of pressurized gas comprises a holder with a continuous gas pump or a compressor for providing a gas flow of 0.05 to 1.2 Nliters/min, preferably 0.05 to 0.4 Nhters/min, more preferred 0.15 to 0.4 Nliters/min, most preferred 0.2 to 0.3 Nliters/min and a reducing valve. In this manner sufficient gas pressure can be obtained to introduce gas via the microfiltration device into the product by using relatively low cost means using a relatively low amount of energy. Preferably the reducing valve is formed by an orifice having a diameter in a range between 0.03 mm and 0.3 mm, preferably between 0.05 and 0.11 mm so that a constant gas flow can be generated.

In a further embodiment of a system for preparing a foamed food product according to the invention, said product preparation apparatus comprises a water source, a heater for heating water, means for pressurizing heated water, said means being configured for detachable connection to the water connection of the disposable assembly for supplying heated water to the water inlet of the eductor of the disposable assembly. The water source of the product preparation apparatus can e.g. be a water reservoir or can be formed by a connection to the water mains. This system is a particularly user-friendly system in that the operative connection of the disposable assembly to the product preparation apparatus can be realized quickly and reproducibly, and furthermore the system can be easily designed to dispense product in a reliable, hygienic manner. Preferably said heater for heating water is then configured to heat water to a temperature in a range between 60°C to 110°C, preferably 90°C to 98°C, more preferred 95°C to 98°C. In contrast to steam injected in a liquid food product before it enters the microfiltration device as described in WO-Al-2011/028117, the heater according to this embodiment requires significantly less energy for heating the water, while still being able to reproducibly produce a foamed food product at an elevated temperature. In comparison to the use of steam, a foamed food product can be obtained without a cooking taste which appears to be quite appealing for at least some of the consumers. In addition, according to a further embodiment of the invention, it is possible to correctly obtain a foamed food product by using means for pressurizing water which is configured to pressurize water in a range between 0.11 to 0.2 MPa. In comparison with existing product preparation apparatus such a pressure is relatively low and can be realized at relatively low costs.

The invention is in particular advantageous in case of a system for preparing a foamed food product wherein the product preparation apparatus is configured to prepare a foamed food product, such as a milk foam or froth, having a temperature in a range generally between 50°C to 85°C, more preferred between 60°C and 70°C, most preferred in a range between 65°C to 68°C.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further explained with reference to the

Figures, in which non-limiting exemplary embodiments of a system for preparing a foamed food product in accordance with the invention are shown. In the drawing: Fig. 1 shows a schematic view in cross section of a disposable assembly for concentrated milk which can be used in an exemplary

embodiment of the system and method according to the invention; and

Fig. 2 shows a schematic view in cross section of a system for preparing a foamed food product according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS In Fig. 1 a schematic view in cross section of a disposable assembly 1 containing concentrated milk is shown, which assembly can be used in an embodiment of a system and method according to the invention. The

disposable assembly 1 comprises a holder 2 which in this Example is designed to contain a maximum amount of 4 liters of milk 3 in concentrated form. This concentrated milk comprises 20 wt% dry matter to 30 wt% dry matter, preferably 23-27 wt% dry matter, whereas unconcentrated milk, i.e. milk with a normal liquid content, comprises 10 wt% dry matter, which latter is also called unconcentrated milk herein. Please note that, although the invention will be explained with respect to milk as (concentrated) liquid food product, the invention can also be applied to other concentrated liquid food products, for instance, (fruit) juice/drink, an alcohol-containing drink or drink base, for instance, beer or wine, a dairy or dairy-based drink, for instance, a whey drink or permeate-based drink, (milk) shake, chocolate drink, (drinking) yoghurt, sauce, ice cream, dessert, or other products, but is in particular intended to provide a foamed milk food product. In addition the maximum amount of milk contained in the holder can in other examples amount to 2 to 5 liters for professional use and 0.5 to 1 liter for home use, and the concentrated milk can in other embodiments comprise 20 wt% dry matter to 30 wt% dry matter.

In the following, air is discussed as the gas to be supplied to the microfiltration device, however, according to an alternative embodiment, the gas can comprise, for instance, an inert gas or another gas or gas mixture, for example containing nitrogen or carbon dioxide.

The disposable assembly 1 furthermore comprises an eductor 4 having a housing 5 with a water inlet 6, a concentrated liquid food inlet 7 and a liquid food outlet 8. The concentrated liquid food inlet 7 of the eductor 4 is positioned between the water inlet 6 and the liquid food outlet 8. Within the housing 5 of the eductor 4 a converging nozzle 9 is present which is in direct communication with the water inlet 6 and a mixing chamber and a diffuser or venturi 10 which are in direct communication with the liquid food outlet 8 of the eductor 4.

The disposable assembly 1 is in addition provided with a

microfiltration device 11 comprising a tubular microfiltration surface 12 having air transmissive pores, and a housing 13 surrounding the tubular microfiltration surface 12. In the shown embodiment the housing 13 and the tubular microfiltration wall 12 are positioned coaxial with respect to one another and an air supply space 17 is formed between the tubular

microfiltration wall 12 and the housing 13. The housing 13 and the tubular microfiltration wall 12 comprise a product inlet opening 14 and, in the embodiment shown in the drawing, an outlet opening 15 opposite the product inlet opening 14. Please note that in other embodiments the inlet and the outlet can be positioned differently to each other. Furthermore, an air opening 16 is in communication with the air supply space 17. In the shown embodiment the air transmissive pores 18 have a pore size of 0.6 micron, but in alternative embodiments the pore size can be in the range of 0.05-10 microns, in particular in a range between 0.1 micron and 2 microns, more particularly a range between 0.2 micron and 1.5 microns. In the present embodiment the tubular microfiltration wall 12 is made of hydrophobic material, such as polypropylene (PP), which in combination with the air transmissive pores 18 of the

mentioned dimensions ensures that the tubular microfiltration wall 12 functions as a HEPA filter. The use of a hydrophobic material ensures that no water or moist, possibly with microorganisms embedded therein, stick to the wall 12, which leads to an improved hygiene during transport and use. In the shown embodiments the eductor 4 and the housing 13 are also made of a hydrophobic material, but it will be clear that in other embodiments other materials can be used. Please note that in the exemplary embodiment, the product feed-through channel is surrounded by the microfiltration wall and the air supply space is at the outside of the microfiltration wall. In an alternative embodiment the product feed-through channel can be positioned outside the microfiltration wall, while the air supply space is formed by the space surrounded by this wall. In addition the microfiltration device can be designed in various other manners.

In the disposable assembly 1 a transfer tube 19 connects the outlet 8 of the eductor 4 with the product inlet opening 14 of the microfiltration device 11. Furthermore, a concentrated liquid food product tube 20 connects the holder 2 to the concentrated liquid food inlet 7 of the eductor 4 and a water inlet tube 21 connects the water inlet 6 of the eductor 4 with a water

connection 22 of the disposable assembly 1. This water connection 22 is configured for connection to an external source of water, preferably a source of hot water under pressure. Please note that with "external source of water" a water source external in relation to the assembly is meant. An air inlet tube 23 connects the microfiltration device 11 to an air connection 24 of the disposable assembly 1, which air connection 24 is configured for connection to an external source of air, preferably an external source of air under (slight) overpressure. As shown in Figure 1, a foamed food product outlet tube 25 connects the outlet opening 15 of the microfiltration device 11 to an outlet connection 26 of the disposable assembly 1 for discharging a foamed food product created by the microfiltration device 11 from the disposable assembly 1. In the shown embodiment the outlet connection 26 is provided with an optional discharge spout 27 and all the tubes and connections are made of hydrophobic material. The connections 22, 24 and the spout 27 (or the connection 26) are closed off by an aseptic seal 28, 29 and 30, respectively. These aseptic seals are designed to be opened by any means known in the art.

In the embodiment shown in Figure 1, the eductor 4, the microfiltration device 11, the transfer tube 19, the concentrated liquid food product tube 20, the water inlet tube 6, the water connection 22, the air inlet tube 16, the air connection 24, the foamed food product outlet tube 25 and the outlet connection 26 (and optionally the spout 27) are assembled as one unit 31. This unit 31 is by said concentrated liquid food product tube 20 connected to a concentrated liquid food product connection 32, which liquid food product connection 32 is detachably connected by an intermediate piece 33 to an outlet connection 34 of the holder 2. From the outlet connection 34 a supply tube 35 extends downward into the concentrated milk 3.

In an alternative example the unit 31 and the holder 2 can be integrated into one piece, in which - when compared to Figure 1 - the concentrated liquid food product tube 20 also forms the supply tube 35 and the connections 32, 34 and the piece 33 need not be present. Please note, that in a non-shown embodiment of a system according to the invention this unit can also form an integral part of the product preparation unit.

In Fig. 2 a schematic view in cross section of a system for preparing a foamed food product according to an exemplary embodiment of the invention is shown. The system comprises a product preparation apparatus 36 for preparing a foamed food product and a disposable assembly 1 as shown in Figure 1. Please note that although in the embodiment shown in Figure 2 the disposable assembly is detachably connected to the product preparation apparatus, in other embodiments of a system according to the invention the disposable assembly can be an integral part of the product preparation apparatus, whilst in addition it is also possible that all the elements of the disposable assembly are distributed over the product preparation apparatus to best fit within the available space of the product preparation apparatus.

Providing the product preparation apparatus with a new amount of concentrated milk can thus e.g. either be realized by replacing an empty disposable assembly with a filled one or be refilling a holder incorporated within the product preparation apparatus.

In the product preparation apparatus 36 a water reservoir 37 is provided as well as a pump 38 as a means for pressurizing water. From the water reservoir 37 a water line 41 runs through the product preparation apparatus 36 and, in this example, has an extension 41A which is configured for detachable connection to the water connection 22 of the disposable assembly 1 for supplying water to the water inlet 6 of the eductor 4 of the disposable assembly 1. The water line 41 runs through an optional particle filter 54, a heater 39 for optionally heating water and passes an optional flow meter 40 for measuring the flow of the water coming from the reservoir 37. Please note, that in other embodiments the water source could be provided by a connection to the water mains.

In the product preparation apparatus 36 also a source of air 42, in this case an opening in the product preparation apparatus 36 to the ambient atmosphere, is provided in which the opening is closed off by a grid 43 for preventing larger particles passing the opening. From the source of air 42 an air hne 44 runs through the product preparation apparatus 36 and, in this example, has an extension 44A which is configured for detachable connection to the air connection 24 of the disposable assembly 1 for supplying air to the air inlet 16 of the microfiltration device 11 of the disposable assembly 1. The air hne 44 passes through an optional particle filter 45 for filtering the air and through an air compressor 46 as means for pressurizing air to a slight overpressure. In this embodiment air from the air compressor is buffered in an air buffer tank 47, which is via a vent line 48, a relief valve 49 and a silencer 50 connected to the ambient atmosphere. In another embodiment in stead of an air compressor and a buffer tank a continuous air pump can be used to supply air to the microfiltration device. In the air line a reducing valve 51 is provided having an orifice having, in this embodiment, a diameter of 0.07 mm for generating a constant air flow. Please note, that in other embodiments the diameter of the orifice can be within a range between 0.03 mm and 0.3 mm.

The product preparation apparatus 36 as shown in Figure 2 can be free of any cooling devices for the disposable assembly 1, which is supported within the product preparation apparatus 36 on a platform 52.

The product preparation apparatus 36 further comprises an operating device 53. e.g a microprocessor, for controlling the operation of the product preparation apparatus 36. For this, the operating device 53 is via lines connected to the air compressor 46 for controlling its operation; the air buffer tank 47 for retrieving the air pressure within the air buffer tank; the water reservoir 37 for retrieving the water level within the reservoir; the water pump 38 and the heater 39 for controlling their operation; and the flow meter 40 for retrieving information on the water flow. In addition the operating device 53 is connected to a sensor 55 for detecting connection and disconnection,

respectively, of the air extension 44A to the air connection 24 of the disposable assembly 1. This sensor 55 is designed for supplying a signal indicative of said connection and disconnection, respectively, to the operating device 53.

In order to be able to perform the present inventive method, which shall be described later, the operating device 53 is configured for continuously activating the air compressor 46 between a detected connection to and a detected disconnection from said air connection 24 of the disposable assembly 1, as detected by the sensor 55. The heater 39 used in the apparatus 36 is configured to heat water to a temperature in a range between 60°C to 110°C, preferably 90°C to 98°C, more preferred 95°C to 98°C. Furthermore, the water pump 38 is configured to pressurize water in a range between 0.11 to 0.2 MPa. Please note, that this is a relatively slight overpressure which could in an alternative embodiment also be provided by a connection water mains alone. The air compressor 46 is configured to pressurize air to a slight overpressure, preferably in a range between 0.101 to 0.15 MPa and for providing an air flow of 0.05 to 1.2 Nliters/min, preferably 0.05 to 0.4 Nliters/min, more preferred 0.15 to 0.4 Nliters/min, most preferred 0.2 to 0.3 Nliters/min. In this manner, the product preparation apparatus 36 can be properly configured to prepare a foamed food product, such as a milk foam or froth having a temperature in a range generally between 50°C to 85°C, more preferred between 60°C and 70°C, most preferred in a range between 65°C to 68°C.

Now an embodiment of an inventive method for preparing a foamed food product utilizing the system as shown in Figure 2 will be described. In an initial step the disposable assembly 1 containing concentrated milk comprising 20 wt% dry matter to 30 wt% dry matter, preferably 23-27 wt% dry matter is connected to the product preparation apparatus 36, wherein the water extension 4lA is connected to the water connection 22 and the air extension 44A is connected to the air connection 24, during which connection the aseptic seals are perforated. The sensor 55 detects this connection and sends an appropriate signal indicating this connection to the operating device 53, which activates the air compressor 46 for continuously supplying air under a slight overpressure to the air supply space 17 around the tubular microfiltration wall 12. The operating device 53 operates to product preparation apparatus 36 to supply air via the orifice 51 to the microfiltration device 11 under a pressure of 0.101 to 0.15 MPa and with an air flow of 0.05 to 1.2 Nliters/min, preferably 0.05 to 0.4 Nliters/min, more preferred 0.15 to 0.4 Nliters/min, most preferred 0.2 to 0.3 Nliters/min. This slight overpressure creates a so-called sterile air curtain which decreases the risk of growth of microorganisms within the disposable assembly significantly which results in a liquid food product that will maintain its sterility over extended periods of time, even under ambient conditions. Since the overpressure is a slight overpressure, it can be produced by relatively low cost devices and with a relatively low amount of energy.

Consequently, a very hygienic preparation of foamed food products can be realized. If a consumer wants to obtain a serving of milk froth, or another product in other embodiments, he or she pushes an activation button (not shown in Figure 2) upon which the operating device 53 activates the heating of the water to a temperature of 95°C to 98°C and pressurizing the water to a pressure of 0.3 MPa by activating the pump 38 and the heater 39, respectively. When the water is sufficiently heated then the operating device 36 operates the product preparation apparatus 36 to supply the heated water to the water inlet 6 of the eductor 4. When the water emerges from the converging nozzle 9 it creates suction for entraining concentrated milk out of the holder 2 and the heated water and concentrated milk are mixed in the mixing chamber 10. By using such a water temperature and water pressure, concentrated milk is entrained out of the holder 2 at such an amount that after mixing with the heated water a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content is obtained. The disposable assembly 1 is kept at ambient temperature and does not require any cooling. Furthermore, in other embodiments pressurizing the water can be done to a pressure in a range between 0.11 to 2.5 MPa.

The air present in the air supply space 17 has a pressure which is higher than the pressure of the milk flowing from the product inlet opening 14 to the outlet opening 15 and the air present in the air supply space 17 enters the milk uniformly via the pores so that fine air bubbles can be homogeneously introduced into the milk for the purpose of foam formation. Finally, the produced milk foam is discharged via the spout 27. In this manner, when milk is supplied to the microfiltration device, it is possible to inject air in the milk in a sterile manner, since the microfiltration device 11 with such transmissive pores and in particular when manufactured from hydrophobic material, such as PP functions as a HEPA filter, leading to a very hygienic manner of preparing the milk foam. Furthermore, adding air to the milk in this way can provide a highly stable, attractive foam, in particular of a constant quality, in a relatively simple manner for a desired period of time. With various foamable products, moreover, a particularly high overrun (degree of aeration) can be obtained.

After the serving of milk foam is discharged the operating device deactivates the water heater and the water pump, but still keeps the air compressor 46 activated to continuously supply air with an overpressure to the microfiltration device. This flow of air with an overpressure expels possible remains from the spout 27 and prevents microorganisms entering the inside of the disposable assembly 1. Only when the disposable assembly 1 is empty and the senor 55 detects disconnection of the air extension 44A from the air connection 24 then the operating device 53 deactivates the air compressor 46.

In this manner a single disposable assembly 1 which is aseptically filled with a content of 3 liter concentrated milk can be used to deliver an amount of milk foam servings for a regular restaurant for seven days, whilst being uncooled, i.e. kept at ambient temperatures, and without any cleaning required during that period. Thus the inventive method and system can provide a liquid food preparation with a minimum of energy consumption, a minimum of handling for the user (refilling and cleaning) and a maximum operation time.

The invention can prepare hot pour able foams, for instance, cappuccino, latte macchiato, and other hot milk drinks, with or without flavor additions. In a further elaboration, to that end, the product is foamed to a minimum overrun of 10%, and obtains/has immediately after dispensing a temperature generally between 50 and 85 °C, more preferred between 60 and 70 °C and most preferred between 65 and 68 °C. The product may be, for instance, predominantly pourable (for instance, with an overrun lower than 100%).

Alternatively, the invention can prepare cold and ice-cold drinks, for instance, milk drink, milk shake, lunch drink, etc. In that case, the product can have, for instance, a minimum overrun of 10%, and a temperature lower than 20 °C, preferably a temperature between -5 and 10 °C. The cold, dispensed product may be predominantly pourable, and can e.g. comprise a sweet or, conversely, a salty product, a fermented milk product.

The invention is particularly well-suited to prepare ice cream or a (milk) shake. The ice cream or (milk) shake product can have an overrun in the range of 10%-200%, and a temperature of 0 °C or lower (preferably a

temperature in the range of -10 °C to -2 °C).

The invention can be used, for instance, such that a product mentioned undergoes an overrun that is greater than 100% (in particular 150% or more, and more particularly 200% or more), utilizing a relatively low pressure (in particular a pressure of air supplied to a air supply space mentioned), for instance, a pressure lower than 0.2 MPa. The invention can be used, for instance, such that a product mentioned undergoes an overrun that is greater than 100% (in particular 150% or more, and more particularly 200% or more), while the dispensed product has a relatively low temperature, for instance, a temperature of 0 °C or lower.

Claims

1. A method for preparing a foamed food product, said method comprising the step of connecting a microfiltration device comprising a microfiltration surface having gas transmissive pores and having a product inlet and a product outlet to a gas supply for supplying gas through the gas transmissive pores of the microfiltration surface, said product outlet being arranged for discharging foamed product, the step of supplying a liquid food product to the microfiltration device, the step of supplying gas to the liquid food product flowing from the product inlet to the product outlet over the microfiltration surface, and the step of disconnecting the microfiltration device from the gas supply, wherein the method comprises the step of continuously supplying the gas through the gas transmissive pores of the microfiltration surface between connection of the microfiltration device to the gas supply and disconnection of the microfiltration device from the gas supply even in the situation where no foamed food product is made.

2. A method for preparing a foamed food product according to claim 1, wherein the microfiltration device comprises a tube with a microfiltration surface, said tube comprising a product entrance opening for receiving said liquid food product, a foamed product outlet opening for discharging foamed product and a product feed-through channel between said product entrance opening and said foamed product outlet opening, wherein the method further comprises the step of connecting the microfiltration device to a gas supply for supplying gas through the gas transmissive pores of the tubular surface, the step of supplying gas to the liquid food product flowing through the product feed-through channel, and the step of disconnecting the microfiltration device from the gas supply, wherein the method comprises the step of continuously supplying the gas through the gas transmissive pores of the tubular surface between connection of the microfiltration device to the gas supply and disconnection of the microfiltration device from the gas supply even in the situation where no foamed food product is made.

3. A method according to claim 1, wherein the step of supplying said gas comprises the step of supplying said gas at a constant gas flow, preferably via a reducing valve, in particular via a small orifice.

4. A method according to claims 1, 2 or 3, wherein the step of supplying gas comprises the step of supplying gas with an pressure of 0.101 to 0.15 MPa and with a gas flow of 0.05 to 1.2 Nliters/min, preferably 0.05 to 0.4

Nhters/min, more preferred 0.15 to 0.4 Nliters/min, most preferred 0.2 to 0.3 Nhters/min.

5. A method according to any one of the preceding claims, wherein the step of supplying a food product to the microfiltration device comprises providing an amount of concentrated liquid food product and mixing said concentrated liquid food product with an amount of water to obtain a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content, which liquid food product is supplied to the microfiltration device.

6. A method according to claim 5, comprising the step of heating the water before it is mixed with the concentrated food product.

7. A method according to claim 6, comprising the steps of providing an eductor with a mixing chamber, providing a water conduit for heated water to the eductor, providing a food product conduit for the concentrated liquid food product to the eductor, supplying heated water to the inlet of said eductor such that suction created at the eductor by the flow of heated water entrains concentrated liquid food product into the chamber where said concentrated liquid food product is mixed with water.

8. A method according to claim 7, wherein the method comprises the steps of storing the concentrated liquid food product at ambient temperature and of heating water to such a temperature and supplying said heated water at such a pressure to the eductor that concentrated liquid food product is entrained at such an amount that after mixing with the heated water a liquid food product with a substantially normal amount of dry matter, or normal amount of liquid content is obtained.

9. A method according to claim 8, wherein the step of heating water heats water to a temperature in a range between 60°C to 110°C, preferably

90°C to 98°C, more preferred 95°C to 98°C, wherein heated water having a pressure in a range between 0.11 and 2.5 MPa, preferably between 0.2 and 0.4 MPa is supplied to the eductor, and wherein as concentrated liquid food product concentrated milk is used comprising 20 wt% dry matter to 30 wt% dry matter, preferably 23-27 wt% dry matter.

10. A method according to any one of the preceding claims, wherein the method comprises the step of using a tube with providing gas transmissive pores having a pore size in the range of 0.05-10 microns, in particular a pore size of at least 0.1 micron and less than 2 microns, wherein a length of the wall of the tube is between 1 cm to 6 cm, preferably 1.5 cm to 5 cm, more preferred 1.5 cm to 3 cm, most preferred 1.6 - 2.0 cm, measured in a product flow direction of product during use flowing along that wall, parallel to that wall, wherein the pore size is preferably in the range of 0.2 micron to 1.5 microns.

11. A method according to any one of the preceding claims, wherein the filtration device is manufactured from a hydrophobic material.

12. A method according to any one of the preceding claims, wherein the prepared foamed food product has a temperature in a range generally between 50°C to 85°C, more preferred between 60°C and 70°C, most preferred in a range between 65°C to 68°C.

13. A system for preparing a foamed food product, configured for carrying out a method according to any one of the preceding claims, said system comprising:

- a product preparation apparatus for preparing said liquid food product; and

- a disposable assembly comprising: - a holder containing a concentrated liquid food product;

- an eductor;

- a microfiltration device;

- a foamed food outlet tube connecting the outlet of the microfiltration device to an outlet connection of the disposable assembly for discharging a foamed food product created by the microfiltration device from the disposable assembly;

said product preparation apparatus comprising a source of pressurized gas, said source of pressurized gas being configured for detachable connection to the gas connection of said disposable assembly for supplying pressurized gas to the gas inlet of the microfiltration device, said product preparation apparatus further comprising an operating device for controlling the operation of the source of pressurized gas, a sensor for detecting connection and disconnection, respectively, of the source of pressurized gas to the gas connection of said disposable assembly and for supplying a signal indicative of said connection and disconnection, respectively, to the operating device, said operating device being configured for continuously activating said source of pressurized gas between said detected connection to and said detected disconnection from said gas connection of said disposable assembly.

14. A system for preparing a foamed food product according to claim 13, wherein the system comprises means for providing a constant gas flow to the microfiltration device, said means preferably being formed by a reducing valve.

15. A system for preparing a foamed food product according to claim 13 or 14, wherein the source of pressurized gas is configured to supply

pressurized gas at a slight overpressure, preferably in a range between 0.101 to 0.15 MPa, and wherein the source of pressurized gas comprises a holder with a continuous gas pump or a compressor for providing a gas flow of 0.05 to 1.2 Nhters/min, preferably 0.05 to 0.4 Nliters/min, more preferred 0.15 to 0.4 Nhters/min, most preferred 0.2 to 0.3 Nhters/min and a reducing valve.

16. A system for preparing a foamed food product according to claim 14 or 15, wherein the reducing valve is formed by an orifice having a diameter in a range between 0.03 mm and 0.3 mm, preferably between 0.05 and 0.1 mm for generating a constant gas flow rate.

17. A system for preparing a foamed food product according to any one of the claims 13 to 16, wherein said product preparation apparatus comprises a water source, a heater for heating water, means for pressurizing heated water, said means being configured for detachable connection to the water connection of the disposable assembly for supplying heated water to the water inlet of the eductor of the disposable assembly.

18. A system for preparing a foamed food product according to claim 17, wherein said heater for heating water is configured to heat water to a temperature in a range between 60°C to 110°C, preferably 90°C to 98°C, more preferred 95°C to 98°C.

19. A system for preparing a foamed food product according to claim 17 or 18, wherein said means for pressurizing water is configured to pressurize water in a range between 0.11 to 0.2 MPa.

20. A system for preparing a foamed food product according to any one of the claims 12 to 18, wherein the product preparation apparatus is free of any cooling devices for the disposable assembly.

21. A system for preparing a foamed food product according to any one of the claims 13 to 20, wherein the product preparation apparatus is configured to prepare a foamed food product having a temperature in a range generally between 50°C and 85°C, more preferred between 60°C and 70°C, most preferred in a range between 65°C to 68°C.