Method of Making a Concentrated Dairy Product

Abstract

A method of making a concentrated dairy product comprising: heating raw milk 104 using a first stage of a pasteuriser 124; ultrafiltering the heated milk 114 to produce a retentate 115a and permeate 1

Description

Field of the Invention The present invention relates to concentrated dairy products and methods of making concentrated dairy products. Background of the Invention Milk is an important source of complete protein and calcium in western diets. Milk, in particular cow’s milk, is used in the production of a vast array of foodstuffs suitable to be served with a wide variety of dishes at any meal time. Raw milk may be processed to produce a drinking milk product having improved properties such as shelf life, safety, appearance and texture. For example, raw milk may be pasteurised to destroy bacteria and / or homogenised to evenly distribute fat throughout the milk. Further, milk is often processed to produce a standardised drinking milk product, that is, a drinking milk having a predetermined fat content, so that the consumer is provided with a consistent milk product. Furthermore, milk may be fortified by the addition of protein, vitamins and / or minerals that are not naturally found in milk in significant quantities, for example, vitamin D, vitamin A, iron or zinc. Drinking milk may also be fortified to contain a greater quantity of protein and minerals than are naturally found in milk. For example, drinking milk may be fortified with dried milk powder to increase a protein content of the milk. Summary of the Invention At its most general, the present invention provides an efficient method of making a dairy product having a high concentration of protein and trace elements, such as calcium and phosphorus, without exogenous fortification, such as the addition of dried milk powder. The method comprises ultrafiltering a milk product to produce a retentate that is high in protein and trace elements and a permeate that is mostly water. In this way, a healthy and nutritious milk product may be produced for consumption as drinking milk, for use as a cooking or beverage ingredient, or for further processing into other dairy based foodstuffs such as yogurt or ice cream. According to a first aspect of the invention, there is provided a method of making a concentrated dairy product, the method comprising: providing a raw milk product; heating, using a first stage of a pasteuriser, the raw milk product to produce a heated milk product; ultrafiltering, using an ultrafiltration plant, the heated milk product to produce a retentate and permeate; wherein protein, fat and at least one mineral are concentrated in the retentate compared to in the permeate; and pasteurising, using a further stage of the pasteuriser, the retentate to produce a concentrated dairy product. As a first step, the milk product enters the first stage of the pasteuriser and is heated by the first stage of the pasteuriser. The milk product may be heated to approximately 50°C by the first stage of the pasteuriser. Next, the heated milk product exits the first stage of the pasteuriser and enters the ultrafiltration plant for ultrafiltration. After ultrafiltration, the retentate re-enters the pasteuriser where it is pasteurised by the further stage of the pasteuriser. In the further stage of the pasteuriser, the pasteurising heat treatment process is completed to produce a concentrated dairy product. By using the pasteuriser to heat the milk before ultrafiltration and to pasteurise the retentate after filtration, the method may be energy efficient. For example, the milk is not heated and cooled multiple times during the process for separate purposes by separate pieces of equipment and each piece of equipment is operated at an optimum temperature. Ultrafiltering the heated milk product may comprise separating the heated milk product into a retentate and a permeate, using a semipermeable membrane through which water and low molecular weight solutes such as free minerals and lactose may pass while solids and high molecular weight solutes, e.g., protein and fat, are unable to pass. The ultrafiltering step may be characterised by a concentration factor. The concentration factor may describe a relative concentration of solids and solutes of high molecular weight present in the retentate when compared with milk product input to the ultrafiltration plant, i.e., the heated milk product. For example, the concentration factor may describe a concentration of protein in the retentate relative to a concentration of protein in the heated milk product. In this way, a concentration factor of 1.5 may define an ultrafiltering step which produces a retentate with a protein content that is 1.5 times higher than a protein content of the milk product input to the ultrafiltration plant. For example, such an ultrafiltering step may produce a retentate with a protein content of 6% from milk input to the ultrafiltration plant having a protein content of 4%. Ultrafiltering takes place outside of the pasteuriser in an ultrafiltration plant. The raw milk product is heated in the first stage of the pasteuriser, ultrafiltered outside of the pasteuriser, and re-enters the pasteuriser ahead of final heat treatment to achieve pasteurisation in the further stage of the pasteuriser. In some embodiments, the permeate comprises less than 0.3% protein. In some embodiments, the permeate comprises less than 0.25% protein. In some embodiments, the permeate comprises less than 0.2% protein. In some embodiments, the permeate comprises less than 0.15% protein. In some embodiments, the permeate comprises less than 0.1% protein. In other words, the permeate comprises a very small quantity of protein. In this way, the majority of the protein of the heated milk product is retained in the retentate to provide a high protein retentate to produce a concentrated dairy product. The permeate may also comprise lactose. A lactose content of the permeate may be substantially equal to a lactose content of the retentate following ultrafiltration. In this way, the lactose contents of the permeate and retentate may be substantially in equilibrium. In some embodiments, heating, using the first stage of the pasteuriser, the raw milk product to produce a heated milk product comprises heating the raw milk product to approximately 50°C. In some embodiments, heating, using the first stage of the pasteuriser, the raw milk product to produce a heated milk product comprises heating the raw milk product to a temperature between 45°C and 55°C. In some embodiments, heating, using the first stage of the pasteuriser, the raw milk product to produce a heated milk product comprises heating the raw milk product to a temperature between 48°C and 55°C. In some embodiments, a temperature of the heated milk product before ultrafiltration is approximately 50°C. In some embodiments, a temperature of the heated milk product before ultrafiltration is between 45°C and 55°C. In some embodiments, a temperature of the heated milk product before ultrafiltration is between 48°C and 55°C. The temperature of the heated milk product before ultrafiltration may be controlled using a heat exchanger of the first stage of the pasteuriser. Additionally, the temperature of the heated milk product before ultrafiltration may be maintained using thermal insulation of the pasteuriser. Additionally or alternatively, the temperature of the heated milk product before ultrafiltration may be controlled using any other suitable thermal mechanism of the pasteuriser. When the temperature of the heated milk product is between 45°C and 55°C before ultrafiltration, a quality of the retentate obtained by the ultrafiltering step may be optimised and loss of protein during ultrafiltration may be minimised. In some embodiments, a temperature of the retentate after ultrafiltration is approximately 50°C. In some embodiments, a temperature of the retentate after ultrafiltration is between 45°C and 55°C. The temperature of the retentate during ultrafiltration may be controlled using a heat exchanger of the ultrafiltration plant. Additionally, the temperature of the retentate during filtration may be maintained using thermal insulation of the ultrafiltration plant. Additionally or alternatively, the temperature of the retentate during filtration may be controlled using any other suitable thermal mechanism of the ultrafiltration plant. In some embodiments, the temperature of the retentate during ultrafiltration is not controlled. After ultrafiltration, the retentate re-enters the pasteuriser to complete the pasteurisation process in the further stage of the pasteuriser. In some embodiments, pasteurising the retentate comprises heating the retentate to a temperature of at least 72.5°C for at least 25 seconds. In this way, the retentate may be pasteurised to destroy or denature microorganisms in the retentate for safe consumption and to prolong product life. As such, the concentrated dairy product is a pasteurised concentrated dairy product. In some embodiments, the concentrated dairy product is chilled to approximately 4°C after pasteurisation. In this way, the concentrated milk product may be cooled to a safe storage temperature to prolong product life and in preparation for packaging or onward distribution or processing. The concentrated dairy product may be chilled to approximately 4°C by the pasteuriser. Recovering heat from the concentrated dairy product after pasteurisation may contribute to an energy efficiency of the method. In some embodiments, pasteurising the retentate comprises heating the retentate to a temperature of at least 95°C for at least 5 minutes. In this way, the retentate may be high-temperature short-time (HTST) pasteurised to destroy or denature microorganisms, including bacterial spores, present in the retentate ahead of being used to make yogurt. In this way, when the concentrated milk product is fermented to make yogurt, a risk of harmful microorganisms growing in the yoghurt is reduced. In some embodiments, the concentrated dairy product is chilled to approximately 43°C after pasteurisation. At this temperature, the concentrated dairy product may be at a temperature suitable for fermentation into yogurt. The concentrated dairy product may be cooled to approximately 43°C by the pasteuriser. Recovering heat from the concentrated dairy product after pasteurisation may contribute to an energy efficiency of the method. The concentrated dairy product may be chilled to any suitable temperature after pasteurisation. In some embodiments, excess cream is removed for further processing. Excess cream may be processed into refrigerated or frozen desserts, such as ice cream, or into cultured products, such as sour cream. In addition, the cream may be processed by separation to produce a cream product having a fat content of approximately 18%, 36% or 48%. In this way, cream products corresponding to single cream (light cream), whipping cream or double cream (heavy cream or heavy whipping cream) may be produced. It will be appreciated that the cream may be separated in any suitable manner to produce any suitable composition having any suitable fat concentration. In some embodiments, the permeate is removed for further processing. For example, the permeate may be used as a feedstock, for production of biofuels, or for anaerobic digestion. In this way, the permeate may be a byproduct of the method. In other embodiments, the permeate is removed as a waste product. In some embodiments, the pasteuriser is a heat exchanger pasteuriser. The pasteuriser may be configured to perform high temperature / short time (HTST) pasteurisation. The pasteuriser may be configured to perform any other appropriate pasteurisation regime. In some embodiments, a volume of the retentate may be substantially half a volume of the heated milk product. In other words, ultrafiltering the heated milk product may substantially halve the volume of the product to produce the retentate. In this way, a concentrated dairy product with the desired protein, fat and trace elements may be provided. Such a volumetric ratio may correspond to the ultrafiltering step having a concentration factor of 2. In some embodiments, the permeate and the retentate are substantially equal in volume. In other words, when the heated milk product is ultrafiltered to produce the retentate and the permeate, a substantially equal in volume of retentate and permeate may be produced. The volumes of the permeate and retentate may be measured for a given volume of the heated milk product and / or in a given time period. In some embodiments, the permeate and the retentate are substantially different in volume. In other words, when the heated milk product is ultrafiltered to produce the retentate and the permeate, a substantially different volume of retentate and permeate may be produced. The volumes of the permeate and retentate may be measured for a given volume of the heated milk product and / or in a given time period. In some embodiments, the method of making a concentrated dairy product further comprises one or more selected from the list: clarifying the milk product to produce a clarified milk product; separating the milk product into skimmed milk and cream; standardising the skimmed milk and cream in a predetermined composition to produce a standardised milk product; homogenising the milk product to produce a homogenised milk product. Clarifying the heated milk product may comprise removing bacteria, particulate contamination and / or bacterial spores from the heated milk product. A centrifugal separator may be used to clarify the heated milk product. Separating the clarified milk product may comprise separating a skimmed milk portion of the clarified milk product from a cream portion. A centrifugal separator may be used to separate the clarified milk product into skimmed milk and cream. One centrifugal separator may be used to clarify and separate the heated milk product to produce skimmed milk and cream that has been clarified. Alternatively, the clarifying and separating steps may be performed by a plurality of centrifuges arranged in sequence. For example, the heated milk product may be clarified in a first centrifuge to produce a clarified milk product which may then be separated in a second centrifuge into skimmed milk and cream. Alternatively, the heated milk product may be separated in a first centrifuge into skimmed milk and cream, one or both of which may be clarified in a second centrifuge to produce a clarified milk and / or cream product. Standardising the skimmed milk and cream in a predetermined composition to produce a standardised milk product may comprise combining the skimmed milk and cream in a predetermined composition to produce a milk product having a predetermined fat content. That fat content may correspond to the desired fat content of the concentrated dairy product divided by a concentration factor of the ultrafiltering step. So, to produce an end product having a first fat content, the skimmed milk and cream may be combined during standardisation to produce a standardised milk product having a second fat content, wherein the first fat content equals the second fat content multiplied by the concentration factor of the ultrafiltering step. For example, to produce a concentrated dairy product having a fat content of approximately 0.1%, 1%, 1.8% or 3.5%, by an ultrafiltering step having a concentration factor of 2, the skimmed milk and cream may be standardised to produce a standardised milk product having a fat content of approximately 0.05%, 0.5%, 0.9% or 1.75% respectively. In this way concentrated milk products corresponding to skimmed milk, 1% milk, semi-skimmed milk or whole milk may be produced. It will be understood that an ultrafiltering step having any other suitable concentration factors may be used. It will be understood that the skimmed milk and cream may be combined in any other suitable proportions to create any other standardised milk product such as to produce a product having a fat content of approximately 5%, 10% or any other desired amount. Homogenising the standardised milk product may include passing the milk product through a homogenising device to break up and disperse fat globules to improve the texture, appearance, taste and stability of the milk product. Heating the raw milk before clarification and separation may increase a yield of the clarifying and separating steps. When goat’s milk is used, an optimal temperature for the clarifying and separating steps may be 48°C. When cow’s milk is used, an optimal temperature for the clarifying and separating steps may be 55°C. When clarification and separation are performed using a centrifuge, the temperature of the heated milk product may be critical to ensure correct operation of the centrifuge and avoid fouling resulting in protein loss. Accordingly, in embodiments comprising the steps of clarifying, separating, standardising and / or homogenising, these may take place after heating and before ultrafiltering. According to a second aspect of the invention, there is provided a concentrated dairy product prepared by the method of the first aspect of the invention. The concentrated dairy product may comprise drinking milk. The concentrated dairy product may be processed into other products, for example yoghurt or ice cream. Brief Description of the Drawings Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 depicts a flowchart illustrating a method of making a concentrated dairy product according to an embodiment of the present invention. Detailed Description With reference to Figure 1, there is provided a flowchart illustrating a method 100 of making a concentrated dairy product. The method comprises providing a raw milk product at step 102. Next, at step 104, the method comprises heating, using a first stage of a pasteuriser, the raw milk product to produce a heated milk product. Next, at step 106, the method comprises clarifying the heated milk product to produce a clarified milk product. Next, at step 108, the method comprises separating the clarified milk product into skimmed milk 109a and cream 109b. Next, at step 110, the method comprises standardising the skimmed milk 109a and cream 109b in a predetermined composition to produce a standardised milk product. Next, at step 112, the method comprises homogenising the standardised milk product to produce a homogenised milk product. Next, at step 114, the method comprises ultrafiltering, using an ultrafiltration plant, the homogenised milk product to produce a retentate 115a and permeate 115b. Protein, fat and at least one mineral are concentrated in the retentate 115a compared to in the permeate 115b. Next, at step 116, the method comprises pasteurising, using a further stage of the pasteuriser, the retentate 115a to produce a concentrated dairy product. Finally, at step 118, the method comprises cooling the concentrated dairy product. It will be understood that the steps of clarifying 106, separating 108, standardising 110 and homogenising 112 are optional and may be omitted in the making of a concentrated dairy product. In this case, the heated milk product may be ultrafiltered at step 114 directly after being heated at step 104. Further, the step of cooling 118, may be optional depending on the intended purpose of the concentrated dairy product. After ultrafiltration at step 114, the permeate 115b may be removed for further processing. The permeate may comprise less than 0.3% protein. Preferably, the permeate 115b may comprise less than 0.25% protein. Further preferably, the permeate 115b may comprise less than 0.2% protein. Further preferably, the permeate 115b may comprise less than 0.15% protein. Further preferably, the permeate 115b may comprise a minimum amount of protein possible, typically less than 0.1% protein. In addition, the permeate 115b may comprise approximately 0.18% non protein nitrogen. Further, the permeate 115b may comprise between 4% and 5% lactose. Further preferably, the permeate 115b may comprise between 4.25% and 4.75% lactose. Preferably, the permeate 115b may comprise approximately 4.5% lactose. Further preferably, the permeate 115b may comprise 4.61% lactose. The permeate 115b may comprise an ash content of less than 1%. Preferably, the permeate 115b may comprise an ash content of approximately 0.7%. Further preferably, the permeate 115b may comprise an ash content of approximately 0.68%. Ash may be the inorganic residue remaining after the water and organic matter have been removed by heating the permeate 115b in the presence of oxidising agents. The ash content provides a measure of the total amount of minerals within the permeate 115b. A fat content of the permeate 115b may be substantially negligible. In other words, the permeate 115b may be substantially fat free. Numerically, the permeate 115b may comprise a fat content of substantially 0%. The permeate 115b may comprise less than 6% solids in total. Preferably, the permeate 115b may comprise approximately 5.5% solids in total. Further preferably, the permeate 115b may comprise approximately 5.57% solids in total. The composition of the retentate 115a may be varied depending on product requirements. Values of an indicative composition of the retentate 115a are provided below. The retentate 115a may comprise a total sugar content of approximately 4%. Preferably, the retentate 115a may comprise a total sugar content of approximately 4.2%. The retentate 115a may comprise a fat content according to a desired fat content of concentrated milk product. For example, the retentate 115a may comprise between 0.01% and 8% fat. During standardising 110, the skimmed milk 109a and cream 109b may be combined to provide a standardised milk product having a fat content that may correspond to the desired fat content of the concentrated milk product divided by an ultrafiltration factor of the ultrafiltering step. For example, for a concentration factor of 2, the fat content of the retentate 115a may be substantially double the fat content of the standardised milk product. The retentate 115a may comprise a protein content according to a specification of the concentrated dairy product. For example, the retentate 114a may comprise between 3% and 8% protein. The retentate 115a may comprise an ash content of approximately 1%. Preferably, the retentate 115a may comprise an ash content of approximately 1.1%. Ash may be the inorganic residue remaining after the water and organic matter have been removed by heating the retentate 115a in the presence of oxidising agents. The ash content provides a measure of the total amount of minerals within the retentate 115a. The ash content may comprise inorganic minerals. The ash content may comprise any selected from the list: sodium; potassium; calcium; phosphorus. The ash content may comprise less than 0.05% sodium. Preferably, the ash content may comprise approximately 0.03% sodium. The ash content may comprise between 0.1% and 0.2% potassium. Preferably, the ash content may comprise between 0.14% and 0.16% potassium. The ash content may comprise between 0.1% and 0.5% calcium. Preferably, the ash content may comprise between 0.13% and 0.3% calcium. The ash content may comprise between 0.05% and 0.3% phosphorus. Preferably, the ash content may comprise between 0.09% and 0.2% phosphorus. In the method 100, the permeate 115b and the retentate 115a may be substantially equal in volume. At step 104, heating, using the initial stage of the pasteuriser, the raw milk product to produce a heated milk product may comprise heating the raw milk product to approximately 50°C. Before ultrafiltration at step 114, the homogenised milk product may be heated to approximately 50°C. After ultrafiltration, the retentate may be heated to approximately 50°C. At pasteurisation step 116, the retentate 115a may be pasteurised at a temperature of at least 72.5°C for at least 25 seconds. Alternatively, at pasteurisation step 116, the retentate 115a may be pasteurised at a temperature of at least 95°C for at least 5 minutes. At step 116, pasteurising may comprise heating the liquid to be pasteurised to any suitable temperature for any suitable duration. The pasteurising steps may comprise ultra high temperature pasteurisation, high temperature short time pasteurisation, or any other suitable method of heat treatment. At cooling step 118, the concentrated dairy product may be chilled to a temperature of approximately 4°C. Alternatively, at cooling step 118, the concentrated milk product may be chilled to a temperature of approximately 43°C in preparation for further processing into a fermented dairy product. Any other required temperature to suit onward processing requirements may be used. At step 120, excess cream may be removed for further processing, e.g., into cream products such as single, whipping or double cream. At step 122, the permeate 115b may be removed for further processing. The steps of heating 104, pasteurising 116 and cooling 118 may be performed by a pasteuriser, indicated by dashed boxes 124. As such, the steps of clarifying 106, separating 108, standardising 110, homogenising 112 and ultrafiltering 114, as well as any further processing of cream 120 or permeate 122, may not be performed by the pasteuriser 124. Pasteurising the retentate may comprise heating the retentate to a temperature of at least 72.5°C for at least 25 seconds. By heating the raw milk product to approximately 50°C before clarifying, separating, standardising, homogenising and ultrafiltering the milk, an efficiency of each of those processes is improved. Further, an energy efficiency of the method is improved as the milk is not heated and cooled multiple times for separate purposes by separate pieces of equipment. A concentrated dairy product may be prepared by the method 100. The concentrated dairy product may be a drinking milk. That is, the concentrated dairy product may be suitable for drinking without further processing. Further embodiments within the scope of the present invention may be envisaged that have not been described above. For example, the steps of the method 100 may be altered in any suitable manner to produce a concentrated dairy product. To the extent that a concentrated dairy product is produced, the steps of the method may be performed in any suitable order. Further, each step may be performed according to any suitable method. It is envisaged that a concentrated dairy product produced by the method of the present invention may be used to make any suitable milk containing product. For example, the concentrated dairy product may be used to make drinking milk, half-and-half, yogurt, kefir, cream, creme fraiche, ice cream, desserts, dairy spreads, quark, fromage frais or cheese. To provide an efficient method of making a concentrated dairy product suitable to be a drinking milk without exogenous fortification, an innovative process is required. The present invention utilises a unique combination of steps to provide a cost-effective method of making a concentrated dairy product that does not require post-processing for suitability as drinking milk. Further, the present invention provides a healthy and nutritious concentrated dairy product. The invention is not limited to the specific examples or structures illustrated, a greater number of steps than are 5 illustrated in the figures could be used, for example. Accordingly, there is herein described a method of making a concentrated dairy product, the method comprising: providing a raw milk product; heating, using a first stage of a pasteuriser, the raw milk product to produce a heated milk product; ultrafiltering, using an ultrafiltration plant, the 10 heated milk product to produce a retentate and permeate; wherein protein, fat and at least one mineral are concentrated in the retentate compared to in the permeate; and pasteurising, using a further stage of the pasteuriser, the retentate to produce a concentrated dairy product. The pasteuriser may pasteurise the retentate according to any appropriate pasteurisation regime. There is also described a concentrated dairy product prepared by the method. 15

Claims

1. A method of making a concentrated dairy product, the method comprising:providing a raw milk product;heating, using a first stage of a pasteuriser, the raw milk product to produce a heated milk product;ultrafiltering, using an ultrafiltration plant, the heated milk product to produce a retentate and permeate;wherein protein, fat and at least one mineral are concentrated in the retentate compared to in the permeate; andpasteurising, using a further stage of the pasteuriser, the retentate to produce a concentrated dairy product.

2. The method of making a concentrated dairy product of claim 1, wherein the permeate comprises less than 0.3% protein.

3. The method of making a concentrated dairy product of claim 1 or claim 2, wherein heating, using a first stage of a pasteuriser, the raw milk product to produce a heated milk product comprises heating the raw milk product to approximately 50°C.

4. The method of making a concentrated dairy product of any preceding claim, wherein a temperature of the heated milk product before ultrafiltration is approximately 50°C.

5. The method of making a concentrated dairy product of any preceding claim, wherein a temperature of the retentate after filtration is approximately 50°C.

6. The method of making a concentrated dairy product of any preceding claim, wherein pasteurising the retentate comprises heating the retentate to a temperature of at least 72.5°C for at least 25 seconds.

7. The method of making a concentrated dairy product of any preceding claim, wherein the concentrated dairy product is chilled to approximately 4°C after pasteurisation.

8. The method of making a concentrated dairy product of any one of claims 1 to 5, wherein pasteurising the retentate comprises heating the retentate to a temperature of at least 95°C for at least 5 minutes.

9. The method of making a concentrated dairy product of claim 8, wherein the concentrated dairy product is chilled to approximately 43°C after pasteurisation.

10. The method of making a concentrated dairy product of any preceding claim, wherein excess cream is removed for further processing.

11. The method of making a concentrated dairy product of any preceding claim, wherein the permeate is removed for further processing.

12. The method of making a concentrated dairy product of any preceding claim, wherein the pasteuriser is a heat exchanger pasteuriser.

13. The method of making a concentrated dairy product of any preceding claim, wherein a volume of the retentate may be substantially half a volume of the heated milk product.

14. The method of making a concentrated dairy product of any preceding claim, wherein the permeate and the retentate are substantially equal in volume.

15. The method of making a concentrated dairy product of any preceding claim, wherein the method further comprises one or more selected from the list:clarifying the milk product to produce a clarified milk product;separating the milk product into skimmed milk and cream;standardising the skimmed milk and cream in a predetermined composition to produce a standardised milk product;homogenising the milk product to produce a homogenised milk product.

16. A concentrated dairy product prepared by the method of any one of the preceding claims.15

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