Patent Description:
Milk protein concentrate (MPC) and Milk protein isolates (MPI) are high protein products produced from skimmed milk. They are widely used in different food products based on their protein content and purity. The common applications include desserts, baked foods, toppings, low fat spreads, dairy-based beverages, texture improvement in yogurts and nutritional drinks. The composition of protein, lactose, calcium and other minerals dictates the use of MPC in various applications.

Currently MPC and MPI are produced using continuous membrane separation process followed by diafiltration to obtain various grades of MPC and MPI. MPI has a higher protein concentration than MPC (generally <NUM>% or more protein "as is"), and a lower level of lactose. See comparative Figure A. However, the level of calcium and lactose in conventional MPC and MPI inhibits the use in niche applications such as clinical products, infant formula and sports market.

Current methods of producing low-lactose MPI's generally involve use of enzymes (<CIT>), which are undesirable due to the generation of additional compounds such as glucose and galactose from enzymatic breakdown of lactose, and ion-exchange resins (<CIT>) which are undesirable due to the leaching of ions from the resins which end up in the product. Another method of preparing a protein concentrate with reduced lactose, which comprises steps of pH adjustment, ultrafiltration and diafiltration, is disclosed in <CIT>. The use of ultra-sonication in the processing of dairy ingredients in disclosed in e.g., <CIT>.

It is an object of the invention to overcome at least one of the above-referenced problems.

The Applicant has addressed the problems of the prior art by providing a process for producing a low-lactose milk concentrate (for example, a low-lactose milk protein isolate; MPI) from a milk concentrate (for example, a milk protein concentrate; MPC) that comprises treating the substrate to ultra-sonication following by diafiltration. The method successfully reduces the level of lactose in the product to less than <NUM>% (%DM) and, in addition, significantly reduces the calcium levels in the product. This is illustrated in Table <NUM> and Table <NUM> where the low-lactose MPI produced according to the method of the invention has more than <NUM>% depletion in calcium compared to the starting MPC substrate, less than <NUM>% lactose (%DM), and in some cases a higher protein concentration. As compared to existing solutions, this is a simple process that obviates the requirement of enzymatic and ion-exchange methodologies.

In a first aspect, the invention provides a method of producing a low-lactose milk protein concentrate comprising the steps of:.

Also disclosed, but not part of the claimed invention, is a method of calcium depletion of a milk product, for example a milk concentrate, comprising pre-treating the milk product by ultra-sonication, and treating the pre-treated milk product by diafiltration to provide a calcium depleted milk product.

In one embodiment, the liquid milk protein concentrate is obtained by ultrafiltration (UF) followed by diafiltration and optionally has a degree of diafiltration of <NUM>-<NUM>%, <NUM>-<NUM>% or <NUM>-<NUM>%.

In one embodiment, the liquid milk protein concentrate comprises <NUM>-<NUM>% protein, <NUM>-<NUM>% protein, <NUM>-<NUM>% protein, or <NUM>-<NUM>% protein (% DM).

In one embodiment, the liquid milk protein concentrate comprises <NUM>-<NUM>% lactose, <NUM>-<NUM>% lactose, <NUM>-<NUM>% lactose, or <NUM>-<NUM>% lactose (% DM).

In one embodiment, the liquid milk protein concentrate comprises <NUM>-<NUM>% calcium (% DM). In one embodiment, the method produces a product that is depleted in calcium compared with the substrate by at least <NUM>%, <NUM>%, <NUM>% or <NUM>% (% DM).

In one embodiment, the liquid milk protein concentrate substrate comprises at <NUM>-<NUM>% protein, <NUM>-<NUM>% lactose, and <NUM>-<NUM>% calcium (% DM).

In one embodiment, the low-lactose milk protein concentrate produced by the method of the invention comprises less than <NUM>% lactose (% DM).

In one embodiment, the low-lactose milk protein isolate produced by the method of the invention comprises less than <NUM>% lactose (% DM).

In one embodiment, the low-lactose milk protein concentrate produced by the method of the invention comprises more than <NUM>% protein (% DM).

In one embodiment, the low-lactose milk protein concentrate produced by the method of the invention comprises less than <NUM>% calcium (% DM).

In one embodiment, the pre-treated milk protein concentrate is treated by diafiltration to a degree of at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> % DF.

In one embodiment, the diafiltration step employs soft water or a dilute salt solution as a diafiltration media.

In one embodiment, the dilute salt solution has a salt concentration of <NUM>-<NUM> salt solution.

In one embodiment, the method comprises a step of drying the low-lactose milk protein concentrate to a powder. Various drying methods may be used to dry the concentrate, including spray-drying, fluidised bed drying, vacuum drum drying, and evaporation.

Also disclosed, but not part of the claimed invention, is a low-lactose milk protein concentrate obtained by the method of the invention.

Also disclosed, but not part of the present invention, is a composition comprising a low-lactose milk protein concentrate obtained by the method of the invention. The composition is generally a comestible composition, for example a food product, beverage, infant formula, a food for special medical purpose (FSMP), or nutritional supplement.

Also disclosed, but not part of the present invention, is a an infant formula comprising a low-lactose milk protein concentrate obtained according to the method of the invention.

Other aspects and preferred embodiments of the invention are defined and described in the other claims set out below.

As used herein, the term "comprise," or variations thereof such as "comprises" or "comprising," are to be read to indicate the inclusion of any recited integer (e.g. a feature, element, characteristic, property, method/process step or limitation) or group of integers (e.g. features, element, characteristics, properties, method/process steps or limitations) but not the exclusion of any other integer or group of integers. Thus, as used herein the term "comprising" is inclusive or open-ended and does not exclude additional, unrecited integers or method/process steps.

As used herein, the term "milk protein concentrate" or "MPC" should be understood to mean skimmed milk concentrate that has been concentrated generally by a membrane filtration process to a protein level of up to <NUM>% and typically <NUM>-<NUM>% milk protein (% DM) and contains more than <NUM>% lactose (% DM), generally <NUM>-<NUM>% or <NUM>-<NUM>% lactose depending on the method of manufacturing. Generally, it is produced by ultrafiltration optionally combined with diafiltration. The casein and whey proteins are generally present in the same ratio as found in unprocessed skimmed milk.

As used herein, the term "milk protein isolates" or "MPI" should be understood to mean high purity protein product produced from milk protein concentrate (MPC) by diafiltration and that contains at least <NUM>% (%DM) protein. In one embodiment a milk protein isolate is a skimmed milk protein concentrate produced by membrane filtration process that contains higher protein content and less than <NUM>% lactose (%DM) as compared to milk protein concentrate. The milk protein isolate has been prepared by membrane process involving high degree of diafiltration. In this case diafiltration of MPC is performed in the range of <NUM>-<NUM> %DF and preferably about <NUM>-<NUM> %DF.

The substrate of the method of the invention may be a milk protein concentrate and the product may be a milk protein isolate. The term "milk protein concentrate with at least <NUM> %DF" or "MPC with at least <NUM> %DF" indicates milk protein concentrate fraction obtained after diafiltration is performed to a level of at least <NUM> %DF.

As used herein, the term "low-lactose" as applied to milk protein isolates produced by the method of the invention should be understood to mean a lactose concentration of less than <NUM>% (% DM), and preferably less than <NUM>%, <NUM>%, <NUM>% or <NUM>% lactose (% DM).

As used herein, the term "calcium depleted" as applied to a low-lactose milk protein isolates means a milk protein isolates that has a calcium level that is depleted compared with the starting milk protein concentrate, and generally depleted by at least <NUM>%, <NUM>%, <NUM>% or <NUM>% (% DM). In one embodiment, the calcium depleted milk protein isolates has less than <NUM>% calcium (% DM).

As used herein, the term "ultra-sonication" should be understood to mean the application of sound energy of ultrasonic frequency (about <NUM> or higher) to a liquid to breakdown particles in the liquid by means of cavitation effect. In the present case, the purpose of the ultra-sonication step is to disrupt casein micelles in the MPC and release calcium phosphate which is then removed in the subsequent diafiltration step. Ultra-sonication may be performed at <NUM>-<NUM>% amplitude, preferably about <NUM>% amplitude. Generally, a plurality of ultra-sonication steps are performed on the MPC. In one embodiment, the ultra-sonication step employs an ultra-sonicator system - such systems are supplied by Hielscher-Ultrasound Technology; Model: UIP1500hdT.

As used herein, the term "diafiltration" should be understood to mean a process involving ultrafiltration membrane to washing out low molecular weight components (in this case lactose and minerals) in the membrane retentate ( in this case MPC and ultrasonicated MPC) by addition of water or DF media into a retentate and removal of permeate from the membrane. The diafiltration is the washing process that involves addition of DF media into substrate and subsequent removal of DF media through membrane that leads to depletion of components other than the product depending on the membrane pore size.

The diafiltration process may be a batch or continuous process. An example of a system for performing continuous diafiltration is illustrated in <FIG>. The diafiltration (DF) media may preferably be water, preferably soft water or a dilute salt solution. At the start of the process, the substrate (i.e. MPC and ultrasonicated MPC) is generally mixed with DF media, typically in a <NUM>:<NUM> volumetric ratio, and fresh DF media is preferably added to the UF retentate in a feed tank at a rate similar to UF permeate flow rate. In one embodiment, the diafiltration step is configured to achieve <NUM>-<NUM> %DF. In one embodiment, the UF membrane has a molecular weight cut off (MWCO) of about <NUM>,<NUM> Da, although membranes with different MWCO may be employed. In a preferred embodiment, diafiltration is performed at below room temperature, typically about <NUM>-<NUM> and ideally about <NUM>.

As used herein, the term "% DM" or "% dry matter" as applied to a component of a milk product should be understood to mean the amount of the component as a % of the dry matter in the milk product by weight. Thus, an MPC having <NUM>% protein (% DM) means that when the MPC is dried to a powder, <NUM>% by weight of the powder will be protein.

As used herein, the term "% DF" as applied to a MPC or MPI should be understood to mean the degree to which the MPC or MPI has been diafiltered as a %. DF % is calculated based on the volume of skimmed milk processed to prepare MPC fraction. It is calculated as per the following formula.

For instance, to achieve <NUM>% DF of MPC fractions, the DF media is calculated as shown in the Table <NUM>. The value of DF media is varies depending on the DF % of MPC fraction. For milk protein concentrate with <NUM>% DF and milk protein concentrate with <NUM>% DF (produced from 5X concentration of skimmed milk) the DF media <NUM> and <NUM> is required to obtain <NUM>% DF.

As used herein, the term "soft water" should be understood to mean containing less than <NUM>/L calcium carbonate.

As used herein, the term "dilute salt solution" should be understood to mean a <NUM>-<NUM> salt solution in which the salt is a generally a sodium or potassium salt (i.e. NaCl or KCI) that produces ions in solution capable of releasing calcium from the casein micelle.

The invention will now be described with reference to specific Examples. These are merely exemplary and for illustrative purposes only: they are not intended to be limiting and constitute the best mode currently contemplated for practicing the invention.

The composition of protein, lactose and calcium in the MPC starting substrate is shown in Table <NUM>.

The ultra-sonication system and membrane separation unit used for the development of innovative hybrid process is shown in <FIG>. In the current process, milk protein concentrate (MPC with <NUM>% DF and MPC with <NUM>% DF) was first subjected to continuous ultra-sonication process using an ultra-sonicator system (Hielscher-Ultrasound Technology; Model: UIP1500hdT, voltage: 230V, amplitude: <NUM> to <NUM>%) with sonication frequency of <NUM> and Power of 1500W. The ultra-sonication pre-treatment of MPC was performed at <NUM>% amplitude at the feed flow rate of <NUM>/min. Four cycles of ultra-sonication treatment were performed at <NUM>% amplitude and solution collected at end of 4th cycle labelled as ultra-sonicated MPC (US-MPC). For all trials, diafiltration was performed at <NUM> using Spectrum® Hollow fiber ultra-filtration module with membrane having MWCO of <NUM>,<NUM> Da and area of <NUM><NUM>.

The ultra-sonication and diafiltration system is illustrated in <FIG>. The continuous diafiltration process is illustrated in <FIG>.

The experiment was performed with liquid MPC sample of Table <NUM> that was subjected to <NUM>-cylces of ultra-sonication treatment (amplitude <NUM>%, sonication frequency: <NUM>, temperature <NUM>). The MPC treated by ultra-sonication is referred to herein as US-MPC. First, Raw MPC sample (<NUM>) and US-MPC with <NUM>% DF level (<NUM>) was introduced into a feed tank in separate trials. Then <NUM> soft water (DF media) was added into each tank and mixed continuously at temperature of <NUM>. In both trials, the mixture was fed onto ultra-filtration membrane (Spectrum® Hollow fiber module, MWCO 0f <NUM>,<NUM> Da, <NUM><NUM> area) and diafiltration was conducted at <NUM>. The membrane permeate was collected separately with simultaneous addition of soft water (<NUM>) to achieve DF level of <NUM>%. The retentate stream was concentrated to achieve total solid content of <NUM>% w/w basis. The membrane retentate i.e. MPI obtained from both trials were analysed for lactose and calcium content.

The MPC sample (<NUM>) of Table <NUM> and ultra-sonication treated MPC (<NUM>) was introduced in a feed tank in separate experiment. The DF media i.e. sodium chloride solution (<NUM>, <NUM>) was added into each tank with continuous stirring at temperature maintained at <NUM>. The mixture was then fed onto the ultra-filtration membrane with molecular weight cut-off <NUM>,<NUM> Da (Spectrum® Hollow fiber module with <NUM><NUM> area). The diafiltration was performed in a continuous mode with addition of DF media with simultaneous removal of permeate from membrane. The diafiltration was performed at <NUM> to achieve <NUM>% DF level and total solid content level of <NUM>% w/w. The membrane retentate samples from both trials, with and without ultra-sonication, were analysed for lactose and calcium content.

The significance of ultra-sonication pre-treatment in the calcium depletion was prominently observed when diafiltration was performed with MPC as such and ultra-sonicated MPC.

Table <NUM> indicated 2X increase in calcium removal with ultra-sonication assisted diafiltration. The ultra-sonication of MPC followed by diafiltration using soft water leads to <NUM>% calcium removal as compared to that obtained with diafiltration trial without ultra-sonication treatment.

The diafiltration trials using dilute sodium chloride solution (<NUM>) further confirms the importance of ultra-sonication in the calcium removal from MPC. The ultra-sonication pre-treatment prior to continuous diafiltration leads to <NUM>% calcium removal which was <NUM> times higher than that obtained after diafiltration of MPC without ultra-sonication treatment. The composition of DF media also found to play a role in calcium removal. The diafiltration of ultra-sonicated MPC using soft water and salt solution produce 3X and 5X, respectively, higher calcium depletion than that obtained with their respective control diafiltration experiment involving no ultra-sonication pre-treatment. This attributed to combined action of ultra-sonication and ionic effect due to presence of salts in DF media that leads to release of calcium from protein micelles and further removal through the membrane separation process.

Claim 1:
A method of producing a low-lactose milk protein concentrate comprising the steps of:
providing a starting liquid milk protein concentrate;
pre-treating the milk protein concentrate by ultra-sonication; and
treating the pre-treated milk protein concentrate by diafiltration to provide a calcium depleted low-lactose milk protein concentrate.