Patent Description:
Concentrated dairy products such as condensed milk have become popular over the last years. The condensed milk contains important nutrients of milk such as calcium, protein, idiom, potassium, and vitamin B2 and B12. The condensed milk is obtained by removing roughly <NUM>% of water from the milk. Conventionally the condensed milk has been produced by evaporating the milk. In addition, the evaporation of milk requires excessive amounts of energy for heating and hence is expensive. Therefore, there is a need to provide a method, to at least partly, address the abovementioned limitations.

<CIT> discloses a process for producing a concentrated or a concentrated and sterilized milk composition, including subjecting the composition to multi-stage recirculating reverse osmosis, where during recirculating reverse osmosis (RRO), for at least part of the RRO process, a step in the RRO process, or during the entire RRO process, the RRO process is carried out at a temperature of from greater than 45F to 60F, where water is removed, to produce a concentrated milk composition. The concentrated milk composition can optionally be sterilized by first heating the concentrated composition to a first elevated temperature of from 175F to 185F (and in some cases to 210F) within a time period of <NUM> seconds to produce a first heated composition.

<CIT> discloses a process for preparing aseptically packaged concentrated milk. To avoid the use of a stabilizer and allow the storage of concentrated milk in packages without refrigeration and without the formation of age gelatin, milk products are concentrated by reverse osmosis, the concentrated milk products are then sterilized by an ultra-high sterilization process, the milk is optionally homogenized, and the sterilized product is then aseptically packaged.

<CIT> discloses a process for producing a concentrated and sterilized milk product comprising the steps of concentrating raw whole milk or skim milk by a cold reverse osmosis process and heating the concentrated product at a first elevated temperature, followed by heating at a second elevated temperature.

<CIT> discloses a method comprising: preparing skimmed milk by separating milk fat content from raw milk (step S1); preparing a primary condensed skimmed milk by condensing the skimmed milk (step S2) by concentrating skim milk prepared in Step S1 preferably without heating, for example, by a reverse osmosis membrane. A part of the moisture contained in the skimmed milk permeates through the reverse osmosis membrane, whereby the nonfat milk solids and milk fat contained in the skim milk are concentrated. By concentrating skimmed milk without heating, it is possible to prevent degradation of proteins contained in skimmed milk by heat denaturation and loss of frankincense components contained in skimmed milk. The primary condensed skimmed milk is preheated by use of an indirect heating method (step S3). The preheated primary condensed skimmed milk is heated to a predetermined sterilization temperature by use of a direct heating method (step S4); and cooled by use of an indirect cooling method (step S6).

It is an object of the present inventive concept to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object of the present inventive concept to provide a method for producing a heat-treated concentrated dairy product with a lower cost and in a manner which may at least reduce thermal impact, compared to the conventional evaporation method. Another object of the present inventive concept is to enable a method to produce heat-treated concentrated dairy products which allows for that less space is required during production as compared to the conventional evaporation method.

According to an aspect of the present inventive concept there is provided a method for producing a heat-treated concentrated dairy product, the method comprising the steps of passing the dairy product under a pre-determined pressure through a reverse osmosis, RO, filter at a first temperature, the pre-determined pressure being sufficient to allow reverse osmosis, thereby concentrating the dairy product, pre-heating the dairy product or the concentrated dairy product at a second temperature within a range of <NUM> to <NUM>° C for a second period of time within a range of <NUM> sec to <NUM> to stabilize the dairy product or the concentrated dairy product, homogenizing the stabilized concentrated dairy product to reduce a size of particles in the stabilized concentrated dairy product, and heating the stabilized concentrated dairy product at a third temperature within a range of <NUM> to <NUM> for a third period of time within a range of <NUM> sec to <NUM> to reduce microorganisms in the stabilized concentrated dairy product, thereby forming the heat-treated concentrated dairy product. In the method, the step of homogenizing the stabilized concentrated dairy product is performed prior to the step of heating the stabilized concentrated dairy product.

The step of passing the dairy product through the RO filter allows for concentrating the dairy product. Thereby, there is no need for evaporation of the dairy product which in turn reduces the thermal impact on the concentrated dairy product. In addition, the step of passing the dairy product through the RO filter allows to produce the heat-treated concentrated dairy product with a lower cost at least by reducing the energy consumption as compared to traditional heating. The step of passing the dairy product may be performed by using one RO filter or a plurality of RO filters arranged in series such that an inlet of a RO filter may be arranged downstream an outlet of an adjacent RO filter. Moreover, a plurality of RO filters may be arranged in parallel. A plurality of RO filters may be arranged in series and in parallel. In other words, the dairy product may be passed through parallel RO filters where each RO filter may include a plurality of RO filters arranged in series.

The step of pre-heating the dairy product or the concentrated dairy product allows stabilization of proteins of the dairy product or the concentrated dairy product. In other words, the step of pre-heating allows the proteins of the dairy product to withstand the heat during the step of heating. In addition, the step of pre-heating the dairy product or the concentrated dairy product contributes to the stabilization of the heat-treated concentrated dairy product against sedimentation during storage.

The step of homogenizing the stabilized concentrated dairy product allows for reducing a size of particles in the stabilized concentrated dairy product. The step of homogenizing also contributes to the stabilization of the heat-treated concentrated dairy product against sedimentation during storage. In addition, the step of homogenizing the stabilized concentrated dairy product improves sensory properties of the heat-treated concentrated dairy product such as viscosity, taste and texture.

The step of heating the stabilized concentrated dairy product allows reducing microorganisms in the stabilized concentrated dairy product. Thereby, the step of heating allows for forming the heat-treated concentrated dairy product. Some examples of the heating are ultra-high temperature (UHT) treatment and pasteurization processes. The step of heating contributes to stabilization of the heat-treated concentrated dairy product against sedimentation during storage.

By a "concentrated dairy product" is hereby meant a dairy product with a substantially lower water content as compared to starting or native dairy product.

By "concentrating the dairy product" is hereby meant removing water from the dairy product. For instance, roughly <NUM>% of water from the dairy product may be removed.

By "stabilize" is hereby meant stabilizing proteins of the dairy product such that the proteins of the dairy product withstand the step of heating. By "stabilize" is also meant that the heat-treated concentrated dairy product remains stable such that no or little sedimentation occurs during storage.

The method may further comprise, subsequent to the step of passing the dairy product through the RO filter, adding a stabilizing salt to the concentrated dairy product. The optional step of adding the stabilizing salt may assist stabilizing proteins of the dairy product to withstand the heat during the step of heating. The optional step of adding the stabilizing salt may also assist stabilization of the heat-treated concentrated dairy product against sedimentation during storage.

The step of passing the dairy product through the RO filter may further comprise circulating the dairy product through the RO filter until a pre-determined concentration of the dairy product is achieved. The circulation of the dairy product through the same RO filter may at least allow a more compact RO filter by for instance not requiring more space to arrange a plurality of RO filters. The circulation of the dairy product through the same RO filter may be performed by a loop pump. The loop pump may hence control flow of the dairy product over the RO filter. This may in turn prevent or at least reduce fouling of the RO filter. However, the dairy product may be circulated through one RO filter or a plurality of RO filters arranged in series such that an inlet of a RO filter may be arranged downstream an outlet of an adjacent RO filter. Moreover, the dairy product may be circulated through a plurality of RO filters arranged in parallel, or plurality of RO filters arranged in series and in parallel.

The step of pre-heating the concentrated dairy product at a temperature within a range of <NUM> to <NUM> for a period of time within a range of <NUM> sec to <NUM> may be performed subsequent to the step of passing the dairy product through the RO filter. Thereby the stabilized concentrated dairy product may already have a higher temperature prior to the heating step. This may in turn reduce energy consumption by e.g. saving energy for increasing a temperature of the stabilized dairy product prior to the step of heating.

The step of pre-heating the dairy product at a temperature within a range of <NUM> to <NUM> for a period of time within a range of <NUM> sec to <NUM> may be performed prior to the step of passing the dairy product through the RO filter. This may in turn improve a flexibility of the method for producing the heat-treated concentrated dairy product.

A total solid content of the heat-treated concentrated dairy product may be in a range from <NUM> to <NUM> wt%. Thereby, the water content of the heat-treated concentrated dairy product may be in a range from <NUM> to <NUM> wt%. By "total solid content" is hereby meant any substance in the dairy product except water. The total solid content comprises a fat content and a solid not fat content (SNF). Examples of such SNF content are protein, mineral and lactose.

A fat content of the heat-treated concentrated dairy product may be in a range from <NUM> to <NUM> wt%. The fat content of the heat-treated concentrated dairy product may be double or triple, compared to the starting or native dairy product.

The first temperature may be within a range of <NUM> to <NUM>° C. In other words, the step of passing the dairy product through the RO filter may be performed at the temperature within a range of <NUM> to10° C.

The second temperature is within a range of <NUM> to <NUM>° C. The second period of time is within a range of <NUM> sec to <NUM>. Thereby, the step of pre-heating the dairy product or the concentrated dairy product at the second temperature within a range of <NUM> to <NUM>° C for the second period of time within a range of <NUM> sec to <NUM> may stabilize the dairy product or the concentrated dairy product.

The pre-determined pressure may be within a range of <NUM> to <NUM> bar. In other words, the step of passing the dairy product through the RO filter may be performed under the pre-determined pressure within a range of <NUM> to <NUM> bar. The predetermined pressure within the range of <NUM> to <NUM> bar may concentrate the dairy product since the pressure is sufficient to initiate reverse osmosis at the RO filter.

The third temperature is within a range of <NUM> to <NUM>. The third period of time is within a range of <NUM> sec to <NUM>. Thereby, the step of heating the stabilized concentrated dairy product at the third temperature within a range of <NUM> to <NUM> for the third period of time within a range of <NUM> sec to <NUM> may reduce microorganisms in the stabilized concentrated dairy product and hence form the heat-treated concentrated dairy product.

With reference to <FIG> a system <NUM> is illustrated. The system <NUM> may be used to produce a heat-treated concentrated dairy product cdp. In the following a heat-treated concentrated dairy product cdp and the system <NUM> in relation to producing a heat-treated concentrated dairy product cdp will be described. The heat-treated concentrated dairy product cdp is typically a UHT treated or pasteurized concentrated dairy product. Examples of concentrated dairy products are sweetened and unsweetened condensed milk. Examples of dairy products dp are various kinds of milk such as semi-skimmed milk, skimmed milk, and whole milk.

In connection with <FIG>, the system <NUM> comprises a RO filter <NUM>. The RO filter <NUM> may comprise one RO filter. The RO filter <NUM> may comprise a plurality of RO filters arranged in series. Moreover, a plurality of RO filters <NUM> may be arranged in parallel. A plurality of RO filters <NUM> may be arranged in series and in parallel. The RO filter <NUM> may comprise one or a plurality of membranes. <FIG> shows that a dairy product dp is provided to the RO filter <NUM>. The RO filter <NUM> may comprise a balance tank to receive the dairy product dp. The RO filter <NUM> may further comprise one or more feed pumps and one or more high pressure centrifugal pumps. The one or more feed pumps may facilitate pumping the dairy product dp into the RO filter <NUM>. The one or more high pressure centrifugal pumps may increase a pressure of the received dairy product dp, prior to passing through the membrane(s) of the RO filter <NUM>. The one or more high pressure centrifugal pumps may increase the pressure of the dairy product dp until a desired pre-determined pressure is achieved. The pre-determined pressure may be within a range of <NUM> to <NUM> bar. The dairy product dp next passes under the pre-determined pressure through the RO filter <NUM> i.e. through the membrane(s) of the RO filter <NUM>. The pre-determined pressure is sufficient to allow reverse osmosis such that the RO filter <NUM> concentrates the dairy product dp. Subsequent to passing of the dairy product dp through the membrane(s) of the RO filter <NUM>, the dairy product dp may be divided to a retentate stream and a permeate stream. The retentate stream does not pass through the membrane(s) and forms the concentrated dairy product dp. The permeate stream is a portion of water content of the dairy product that passes through the membrane(s). The permeate stream may be discarded or used for other purposes. The RO filter <NUM> may further comprise a control valve. The control valve may be controlled to control the pressure over the membrane of the RO filter <NUM> and/or the amount of dairy product dp being fed to the RO filter <NUM>. For instance, the control valve may be controlled based on an instant pressure at the RO filter <NUM> and/or based on a ratio calculated from a flow of the received dairy product and a flow of the retentate stream. The RO filter <NUM> may further comprise filtration loops. In the filtration loops the dairy product dp may pass through one or a plurality of loop pumps. The loop pump(s) may circulate the concentrated dairy product dp i.e. the retentate stream through the RO filter <NUM> until a pre-determined concentration of the dairy product dp is achieved. The loop pump(s) may also ensure sufficient flow of the dairy product dp over the membrane surface(s) so as to minimize fouling of the membrane(s). Upon achieving the predetermined concentration of the dairy product dp, the concentrated dairy product dp may exit the RO filter <NUM>. The RO filter <NUM> may operate at a first temperature. The first temperature may be within a range of <NUM> to <NUM>° C.

Still in connection with <FIG>, subsequent to passing <NUM> the dairy product dp through the RO filter <NUM>, a stabilizing salt s may be added to the concentrated dairy product dp.

Still in connection with <FIG>, the system <NUM> further comprises a pre-heating unit <NUM>. <FIG> shows that the pre-heating unit <NUM> receives the concentrated dairy product dp with the optionally added stabilizing salts. The pre-heating unit <NUM> preheats the concentrated dairy product dp at a second temperature for a second period of time. The pre-heating unit <NUM> stabilizes the concentrated dairy product dp. The second temperature is within a range of <NUM> to <NUM>° C. The second period of time is within a range of <NUM> sec to <NUM>. The pre-heating unit <NUM> may be any conventional heating unit. For instance, the pre-heating unit <NUM> may be a tube type heat exchanger. The tube type heat exchanger may comprise straight and corrugated tubes. The tube type heat exchanger may provide optimal performance, long production time and low maintenance costs. Alternatively a plate type heat exchanger may be used as the pre-heating unit <NUM>. The pre-heating unit <NUM> may comprise a plurality of heat exchangers of different types.

Still in connection with <FIG>, the system <NUM> further comprises a homogenizing unit <NUM>. <FIG> shows that the homogenizing unit <NUM> is arranged downstream the pre-heating unit <NUM>. The homogenizing unit <NUM> reduces a size of particles in the stabilized concentrated dairy product dp. The homogenizing unit <NUM> may improve a homogeneity, stability and mouthfeel of the stabilized concentrated dairy product dp. The homogenizing unit <NUM> may be any conventional homogenizing unit which per se is known in the art.

Still in connection with <FIG>, the system <NUM> further comprises a heating unit <NUM>. <FIG> shows that the heating unit <NUM> is arranged downstream the homogenizing unit <NUM>. The heating unit <NUM> heats the stabilized concentrated dairy product at a third temperature for a third period of time to reduce microorganisms in the stabilized concentrated dairy product. The third temperature is within a range of <NUM> to <NUM>. The third period of time is within a range of <NUM> sec to <NUM>. The heating unit <NUM> may be any conventional heating unit. The heating unit <NUM> may provide UHT treatment or pasteurization. For instance, the heating unit <NUM> may perform the UHT treatment using a direct or an indirect heating. In the case of the direct UHT heating, the heating unit <NUM> may inject steam into the stabilized concentrated dairy product dp. In the case of the indirect UHT heating, the heating unit <NUM> may heat the stabilized concentrated dairy product dp in an indirect manner. In other words, in the case of the indirect UHT heating, the plant milk base MB may not come into direct contact with the heat source but may instead be heated by a heat exchanger. In this case, the heat exchanger may e.g. be a plate type heat exchanger. <FIG> shows that the outlet of the heating unit <NUM> is the heat-treated concentrated dairy product cdp.

Still in connection with <FIG>, the RO filter <NUM>, the pre-heating unit <NUM>, the homogenizing unit <NUM>, and the heating unit <NUM> may be arranged in some other order, provided that the heating unit <NUM> is arranged downstream the pre-heating unit <NUM> in a direct or an indirect manner. For instance, the system <NUM> may be arranged such that the RO filter <NUM> may be arranged downstream the pre-heating unit <NUM>, the homogenizing unit <NUM> may be arranged downstream the RO filter <NUM> and the heating unit <NUM> may be arranged downstream the homogenizing unit <NUM>.

In connection with <FIG>, a block scheme of a method <NUM> for producing a heat-treated concentrated dairy product cdp is illustrated. The method <NUM> comprises passing <NUM> the dairy product dp under a pre-determined pressure through a reverse osmosis, RO, filter <NUM> at a first temperature, the pre-determined pressure being sufficient to allow reverse osmosis, thereby concentrating the dairy product dp. The step of passing <NUM> the dairy product through the RO filter <NUM> may be performed using the RO filter <NUM> or a plurality of RO filters <NUM>, as described above. The step of passing <NUM> the dairy product through the RO filter <NUM> may be performed, as described above.

The method <NUM> may further comprise subsequent to the step of passing <NUM> the dairy product dp through the RO filter <NUM>, adding <NUM> a stabilizing salts to the concentrated dairy product dp. The step of adding <NUM> the stabilizing salts to the concentrated dairy product dp may be performed, as described above.

The method <NUM> further comprises pre-heating <NUM> the concentrated dairy product dp at a second temperature within a range of <NUM> to <NUM>° C for a second period of time within a range of <NUM> sec to <NUM> to stabilize the concentrated dairy product dp. The step of pre-heating <NUM> the concentrated dairy product dp may be performed using the pre-heating unit <NUM>, as described above. The step of pre-heating <NUM> the concentrated dairy product dp may be performed, as described above.

The method <NUM> further comprises homogenizing <NUM> the stabilized concentrated dairy product dp to reduce a size of particles in the stabilized concentrated dairy product dp. The step of homogenizing <NUM> the stabilized concentrated dairy product dp may be performed using the homogenizing unit <NUM>, as described above. The step of homogenizing <NUM> the stabilized concentrated dairy product dp may be performed, as described above.

The method further comprises heating <NUM> the stabilized concentrated dairy product dp at a third temperature within a range of <NUM> to <NUM>° C for a third period of time within a range of <NUM> sec to <NUM> to reduce microorganisms in the stabilized concentrated dairy product dp, thereby forming the heat-treated concentrated dairy product cdp. The step of heating <NUM> the stabilized concentrated dairy product dp may be performed using the heating unit <NUM>, as described above. The step of heating <NUM> the stabilized concentrated dairy product dp may be performed, as described above.

The method <NUM> may be performed in any order, provided that the step of pre-heating <NUM> is performed prior to the step of heating <NUM>. The step of pre-heating <NUM> of the dairy product dp may be performed subsequent to the step of passing <NUM> the dairy product dp through the RO filter <NUM>. The step of pre-heating <NUM> of the dairy product dp may be performed prior to the step of passing <NUM> the stabilized dairy product dp through the RO filter <NUM>. The step of homogenizing <NUM> the stabilized concentrated dairy product dp is performed prior to the step of heating <NUM> the stabilized concentrated dairy product dp.

Claim 1:
A method (<NUM>) for producing a heat-treated concentrated dairy product (cdp), the method (<NUM>) comprising the steps of:
passing (<NUM>) the dairy product (dp) under a pre-determined pressure through a reverse osmosis, RO, filter (<NUM>) at a first temperature, the pre-determined pressure being sufficient to allow reverse osmosis, thereby concentrating the dairy product (dp),
pre-heating (<NUM>) the dairy product or the concentrated dairy product (dp) at a second temperature within a range of <NUM> to <NUM>° C for a second period of time within a range of <NUM> sec to <NUM> to stabilize the dairy product or the concentrated dairy product (dp),
homogenizing (<NUM>) the stabilized concentrated dairy product (dp) to reduce a size of particles in the stabilized concentrated dairy product (dp), and
heating (<NUM>) the stabilized concentrated dairy product (dp) at a third temperature within a range of <NUM> to <NUM> for a third period of time within a range of <NUM> sec to <NUM> to reduce microorganisms in the stabilized concentrated dairy product (dp), thereby forming the heat-treated concentrated dairy product (cdp); characterized in that
the step of homogenizing (<NUM>) the stabilized concentrated dairy product (dp) is performed prior to the step of heating (<NUM>) the stabilized concentrated dairy product (dp).