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Title:
A2 BETA-CASEIN AND VISCOSITY OF MILK PRODUCTS
Document Type and Number:
WIPO Patent Application WO/2017/003300
Kind Code:
A1
Abstract:
The use of milk for the preparation of a dairy product, wherein the milk contains at least 90% A2 beta-casein by weight of total beta-casein, and the dairy product has a viscosity at least 5% greater than the same dairy product prepared from milk containing less than 90% A2 beta-casein by weight of total beta-casein. Improved viscosity leads to improved foaming ability, frothing ability and/or mouthfeel of milk and dairy products.

Inventors:
CLARKE, Andrew, John (14 Cleveland Road, ParnellAuckland, 1052, 1052, NZ)
Application Number:
NZ2016/050104
Publication Date:
January 05, 2017
Filing Date:
June 29, 2016
Export Citation:
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Assignee:
THE A2 MILK COMPANY LIMITED (C/- Simpson Grierson, Level 27 88 Shortland Street, Auckland, NZ)
International Classes:
A23C9/20; A23C9/00; A23L33/19
Attorney, Agent or Firm:
CATALYST INTELLECTUAL PROPERTY (Level 5, 111 Customhouse QuayWellington, 6011, 6011, NZ)
Download PDF:
Claims:
CLAIMS

1. The use of milk for the preparation of a dairy product, wherein :

(i) the milk contains at least 90% A2 beta-casein by weight of total beta-casein, and

(ii) the dairy product has a viscosity at least 5% greater than the same dairy product prepared from milk containing less than 90% A2 beta-casein by weight of total beta-casein.

2. The use as claimed in claim 1, wherein the viscosity of the dairy product is 5-20% greater than the same dairy product prepared from milk containing less than 90% A2 beta- casein by weight of total beta-casein.

3. The use as claimed in claim 1 or claim 2, wherein the A2 beta-casein is any beta- casein having proline at position 67 of the beta-casein amino acid sequence.

4. The use as claimed in any one of claims 1 to 3, wherein the milk contains at least 95% A2 beta-casein by weight of total beta-casein.

5. The use as claimed in any one of claims 1 to 4, wherein the milk contains 100% A2 beta-casein by weight of total beta-casein.

6. The use as claimed in any one of claims 1 to 5, wherein the dairy product is steamed milk, cream, yoghurt, quark, custard, junket, mousse, condensed milk, cream cheese, creme anglais, creme fraiche, sour cream, soft-serve ice cream, whipped cream, or clotted cream.

7. The use as claimed in any one of claims 1 to 6, wherein the dairy product has improved foaming ability, frothing ability or mouthfeel relative to the same dairy product prepared from milk containing less than 90% A2 beta-casein by weight of total beta-casein.

8. The use as claimed in any one of claims 1 to 7, wherein the milk is fresh milk, milk powder, liquid milk reconstituted from powder, skim milk, homogenised milk, condensed milk, evaporated milk, pasteurised milk, or non-pasteurised milk. 9. A process for preparing a dairy product from milk, wherein :

(i) the milk contains at least 90% A2 beta-casein by weight of total beta-casein, and

(ii) the dairy product has a viscosity at least 5% greater than the same dairy product prepared from milk containing less than 90% A2 beta-casein by weight of total beta -casein.

10. A process as claimed in claim 9, wherein the dairy product is steamed milk, cream, yoghurt, quark, custard, junket, mousse, condensed milk, cream cheese, creme anglais, creme fraiche, sour cream, soft-serve ice cream, whipped cream, or clotted cream. 11. A process as claimed in claim 9, wherein the milk is fresh milk, milk powder, liquid milk reconstituted from powder, skim milk, homogenised milk, condensed milk, evaporated milk, pasteurised milk, or non-pasteurised milk.

Description:
A2 BETA-CASEIN AND VISCOSITY OF MILK PRODUCTS

TECHNICAL FIELD

The invention relates to the milk protein A2 beta-casein and its effect on the viscosity of milk and milk products. In particular, the invention relates to milk and milk derived food products that have improved viscosity due to the presence of the protein A2 beta-casein.

BACKGROUND OF THE INVENTION

The viscosity of dairy products has important implications for the processes by which dairy products are manufactured as well as for meeting consumer preferences for dairy products such as firmness, creaminess, foaminess, thickness and organoleptic characteristics such as mouthfeel and flavour. Manufacturing processes such as evaporation and ultrafiltration are influenced by the viscosity of milk and other materials as well as by the viscosity of products made utilising such processes.

The concentrations of milk-derived lactose, casein, fat, and whey protein can all have a significant influence on the viscosity of a dairy product. Studies have been conducted to determine the effect of casein micelles on the viscosity of milk and dairy products. Viscosity can be an indicator of the amount of casein micelle agg regation in milk as well as an indicator of the rate of creaming, mass and heat transfer, and flow conditions in dairy processes.

The applicant has now found that certain casein proteins found in milk, specifically beta-caseins, can have an influence on the viscosity and related characteristics of dairy products including foaming and mouthfeel .

The applicant and others have previously determined a link between the consumption of Al beta-casein in milk and milk products and the incidence of certain health conditions including type I diabetes (WO 1996/014577), coronary heart disease (WO 1996/036239) and neurological disorders (WO 2002/019832). Further, the applicant has shown a link between beta-casein Al and bowel inflammation (WO 2014/193248), lactose intolerance (WO 2015/005804), and high blood glucose levels (WO 2015/026245) .

The applicant has now found evidence for improved viscosity characteristics in certain dairy products prepared from milk that has beta-casein which is predominantly A2 beta-casein and has little or no Al beta-casein.

It is therefore an object of the invention to provide a dairy product having desirable viscosity characteristics, or to at least provide a useful alternative to existing dairy products.

SUMMARY OF THE INVENTION

In a first aspect of the invention there is provided the use of milk for the preparation of a dairy product, wherein : (i) the milk contains at least 90% A2 beta-casein by weight of total beta-casein, and

(ii) the dairy product has a viscosity at least 5% greater than the same dairy product prepared from milk containing less than 90% A2 beta-casein by weight of total beta-casein.

In some embodiments of the invention, the viscosity of the dairy product is 5-20% greater than the same dairy product prepared from milk containing less than 90% A2 beta- casein by weight of total beta-casein.

The A2 beta-casein may be any beta-casein having proline at position 67 of the beta- casein amino acid sequence.

In preferred embodiments, the milk contains at least 95% A2 beta-casein by weight of total beta-casein, and may contain 100% A2 beta-casein by weight of total beta-casein.

The dairy product may be any type of dairy product, for example steamed milk, cream, yoghurt, quark, custard, junket, mousse, condensed milk, cream cheese, creme anglais, creme fraiche, sour cream, soft-serve ice cream, whipped cream, or clotted cream.

In some embodiments, the dairy product has improved foaming ability, frothing ability or mouthfeel relative to the same dairy product prepared from milk containing less than 90% A2 beta-casein by weight of total beta-casein.

The milk may be fresh milk, milk powder, liquid milk reconstituted from powder, skim milk, homogenised milk, condensed milk, evaporated milk, pasteurised milk, or non- pasteurised milk, or any other type of milk.

In a second aspect of the invention there is provided a process for preparing a dairy product from milk, wherein :

(i) the milk contains at least 90% A2 beta-casein by weight of total beta-casein, and

(ii) the dairy product has a viscosity at least 5% greater than the same dairy product prepared from milk containing less than 90% A2 beta-casein by weight of total beta-casein. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows viscosity measurements for A2 skim milk and A1A2 skim milk samples at 5% to 20% w/w concentrations.

Figure 2 shows average foam volumes for A2 skim milk and A1A2 skim milk.

Figure 3 shows average foam stabilities for A2 skim milk and A1A2 skim milk.

Figure 4 shows average foam heights of reconstituted A1A1 milk and A2A2 milk. DETAILED DESCRIPTION

The invention relates to the use of milk containing a high proportion of A2 beta- casein relative to Al beta-casein for the preparation of dairy products having desirable viscosity and related characteristics.

Milk, mainly bovine milk, consumed in populations throughout the world, is a major source of protein in human diets. Bovine milk typically comprises around 30 grams per litre of protein. Caseins make up the largest component (80%) of that protein, and beta-caseins make up about 37% of the caseins. In the past two decades the body of evidence implicating casein proteins, especially beta-caseins, in a number of health disorders has been growing.

The beta-caseins can be categorised as Al beta-casein and A2 beta-casein. These two proteins are the predominant beta-caseins in milk consumed in most human populations. Al beta-casein differs from A2 beta-casein by a single amino acid. A histidine amino acid is located at position 67 of the 209 amino acid sequence of beta-casein Al, whereas a proline is located at the same position of beta-casein A2. This single amino acid difference is, however, critically important to the enzymatic digestion of beta-caseins in the gut. The presence of histidine at position 67 allows a protein fragment comprising seven amino acids, known as beta-casomorphin-7 (BCM-7), to be produced on enzymatic digestion. Thus, BCM-7 is a digestion product of Al beta-casein. In the case of A2 beta- casein, position 67 is occupied by a proline which hinders cleavage of the amino acid bond at that location. Thus, BCM-7 is not a digestion product of A2 beta-casein.

Other beta-casein variants, such as B beta-casein and C beta-casein, also have histidine at position 67, and other variants, such as A3, D and E, have proline at position 67. But these variants are found only in very low levels, or not found at all, in milk from cows of European origin. Thus, in the context of this invention, the term "Al beta-casein" refers to any beta-casein having histidine at position 67, and the term "A2 beta-casein" refers to any beta-casein having proline at position 67.

The term "dairy product" means any food produced from the milk of mammals. Apart from breastfed infants, the human consumption of dairy products is sourced primarily from the milk of cows, water buffalo, goats, sheep, yaks, horses, camels, domestic buffalo, and other mammals. Examples of dairy products that have a measurable viscosity include cream, yoghurt, quark, custard, junket, mousse, condensed milk, cream cheese, creme anglais, creme fraiche, sour cream, soft-serve ice cream, whipped cream, and clotted cream.

The term "viscosity" of a fluid refers to dynamic (or shear) viscosity and is a measure of resistance to shearing flows where adjacent layers of the fluid move parallel to each other at different speeds. Viscosity is usually measured in Pascal-seconds (Pa.s). Water has a viscosity of 8.94 x 10 "4 Pa.s. In contrast, the viscosity of honey is 2-10 Pa.s, molten chocolate 45-130 Pa.s, and ketchup 50-100 Pa.s. Viscosity generally relates informally to the thickness of a material.

Viscosity is a key aspect of food rheology which is the study of the flow of matter, primarily in a liquid state, but also as 'soft solids' or solids under conditions in which they respond with plastic flow rather than deforming elastical y in response to an applied force. Rheology applies to substances that have a complex microstructure, including many foods and food additives. The viscosity of foods, including dairy products, is also an important characteristic of mouthfeel. Other related characteristics include firmness, creaminess, foaminess and thickness.

While the milk may be obtained from any mammal, including humans, cows, water buffalo, goats, sheep, yaks, horses, camels, domestic buffalo, in preferred embodiments of the invention the milk is bovine milk.

The milk may be in the form of fresh milk, milk powder, liquid milk reconstituted from a powder, skim milk, homogenised milk, condensed milk, evaporated milk, pasteurised milk or non-pasteurised milk, or any other form of milk.

Milk comprising beta-casein that is predominantly or exclusively A2 beta-casein (i.e. contains little or no Al beta-casein) may be obtained by firstly genotyping cows for the beta-casein gene, identifying those cows that have the ability to produce A2 beta-casein in their milk and no other beta-casein (i.e. cows having the A2A2 allele), and milking those cows. The methodology is described generally in WO 1996/036239 and will be appreciated and understood by those skilled in the fields of animal genotyping, herd formation and the production and supply of bovine milk.

The invention is supported by the findings of Example 1 where milk powder obtained from different sources was evaluated for viscosity under controlled temperature conditions following dissolution in water. The milk referred to as "A2 skim milk" is skim milk that has been prepared from milk having a beta-casein composition that is 100% A2 beta-casein. The milk referred to as "A1A2 skim milk" is skim milk that has been prepared from milk having a beta-casein composition that is 31% Al beta-casein and 69% A2 beta-casein. The content of beta-casein proteins was measured using LC-MS/MS following a tryptic digestion to yield proteotypic peptides for the Al and A2 beta-casein phenotypes. The results show that A2 skim milk is more viscous than A1A2 skim milk (particularly at a concentration of 20% w/w concentration).

The invention is further supported by the findings of Examples 2 to 4 where foam- ability and foam stability of A2 skim milk and A1A2 skim milk were assessed.

A foam is a system comprising two phases: air separated by a continuous liquid. The protein content of milk is important for foam characteristics. Proteins are amphiphilic macromolecules and therefore have a role in both the formation and stability of milk foam. Beta-caseins are known to be relatively loose and flexible molecules which can rapidly adsorb to the interface where air meets water in new bubbles. This decreases the interracial free energy to form a continuous film surrounding each air bubble. Foam plays a central role in the texture of aerated dairy products.

Example 2 shows that A2 skim milk and A1A2 skim milk behave differently in terms of both immediate foam volume as well as foam stability over time. A2 skim milk was found to be consistently more foamable and therefore is expected to provide an advantage in the development of aerated dairy products.

Example 3 describes a simple experiment using a commercially available espresso machine to assess the frothing of milk samples when subjected to steaming. Froth height and volume was found to be greater for samples having beta-casein which is 100% A2 beta-casein.

Example 4 shows that milk containing A2 beta-casein and no Al beta-casein (A2A2 samples) produced a significantly greater volume of foam as measured by height compared to milk containing Al beta-casein and no A2 beta-casein (A1A1 samples). A maximum increase of 29.6% in foam height was observed for A1A1 milk. This height was reached after bubbling air into the milk for 30 seconds. The foam maintained a consistent height until the air flow was turned off. The foam height started to drop within 30 seconds of the air flow being turned off. For A2 milk, a maximum increase of 402.3 % in foam height was observed for A2A2 milk. This maximum height was reached after 90 seconds of air flow and maintained until the air flow was turned off. The foam height dropped back to very near to starting height levels (3.2%) 120 seconds after the air flow was turned off.

The observations of Examples 1 to 4 therefore show that milk containing beta-casein that is predominantly or exclusively A2 beta-casein may advantageously be used to prepare dairy products having improved or more desirable characteristics due to the higher viscosity and foamability of such milk relative to milk having a greater proportion of Al beta-casein. The milk used for preparing such dairy products preferably has a beta-casein component that comprises at least 90% by weight A2 beta-casein. The amount of A2 beta-casein may be any amount in the range of 90% to 100% by weight of the beta-casein, for example at least 90%, at least 95%, at least 98%, at least 99%, or even 100%. Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field.

As used in this specification, the words "comprises", "comprising", and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to".

The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. EXAMPLES

Example 1: Viscosity measurements

Milk powders were prepared in an identical manner. Milk was made by reconstituting the powder to 5%, 10%, 15% and 20% w/w using Milli-Q water treated with 0.02% sodium azide (to prevent microbial growth). Each milk sample was prepared by solubilising the powder with Milli-Q in a beaker using a magnetic stirrer bar and a stirring plate set to 500rpm. Para-film was used to cover the beaker and prevent evaporation. After 90 minutes of stirring, the samples were transferred to Schott bottles and stored overnight in a 4°C fridge before being subject to analysis. On the day of analyses, the milk samples were removed from the fridge and left to equilibrate to room temperature (2 hours).

Viscosity measurements were performed using an Anton Paar Physica MCR 301 rheometer with cylinder peltier temperature device and a concentric cylinder system. This provides a defined shear gap and results in constant shear conditions (Schaupp- Morocutti, 2008). Each sample was run in duplicate and subject to the same temperature, shear and time parameters, as outlined in Table 1.

Table 1: Parameters used for viscosity measurements

The results from viscosity measurements (Figure 1) show that as the concentration of milk powder used increases, the viscosity of the milk increases when subjected to shear stress and strain. This holds true for both milk samples tested. In general, the difference in viscosity at each concentration is increasingly apparent at higher concentrations (15% w/w and 20% w/w). A2 skim milk, which has viscosity of up to 0.00471 Pa.s at 20% w/w concentration, is the most viscous compared to A1A2 skim milk with the lowest viscosity of up to 0.0035 Pa.s at 20% w/w concentration.

Example 2: Foaming and foam stability

Milk samples were prepared according to the method described in Example 1. A2 skim milk and A1A2 skim milk (10% w/w) were tested in triplicate for this experimental method. Samples (20 mL) were measured into centrifuge tubes and subjected to vertical shaking in a Griffin Flask Shaker at a fixed output of 200 volts and 60 watts for one minute. Photographs of the foam in the centrifuge tubes were taken immediately after shaking (Omin) and at intervals of 2.5 min, 5 min, 10 min, 20 min and 30min after shaking. These photographs were later compared and analysed for immediate foam volume and changes over the 30 minute time period. Figure 2 shows average immediate foam volumes. Figure 3 shows average foam stabilities. The results show that A2 skim milk has better foaming ability compared to A1A2 skim milk at a 10% w/w concentration. For A2 skim milk, the average immediate foam volume was 12.46 mL compared to the average foam volume for A1A2 skim milk which was 10.29 mL. A2 skim milk was found to have a consistently higher foam volume between 0 to 30 minutes but the stability of A1A2 skim milk is better. This is shown in Figure 3 where the initial difference in foam height between the samples of 2.18 mL reduces to 0.9 mL after 30 minutes.

Example 3: Frothing of milk

Samples of two types of milk were tested . One type contains beta-casein that is 100% A2 beta-casein and is referred to as A2A2 milk. The second type contains beta- casein that is 60 :40 A2 beta-casein to Al beta-casein and is referred to as A1A2 milk. Each milk sample (250 ml), having an initial temperature of 4 °C +/- 1°C, was placed in a 7.5 cm graduated beaker. Using a commercial Feama Espresso machine (model c 85/1) producing steam at 1-1.2 kPa, the tip of the steaming arm was placed just below the surface of the milk. The milk was steamed for 25 seconds, the temperature of the milk noted, and the sample allowed to settle. The following measurements were taken :

• Initial height of milk level (IF)

• Height of froth after 1 minute (FH1)

• Height of froth after 5 minutes (FH5)

• Volume of liquid milk (LV)

• Total volume of milk and forth (TV)

Each sample was frothed 2-3 times, and the mean for each value determined.

Table 2: Froth measurements

Example 4: Foaming ability of milk

The foaming ability of a 12% solution of milk containing 100% Al beta-casein (A1A1 milk) and milk containing 100% Al beta-casein (A2A2 milk) made from spray dried powders was measured by bubbling air into the milk and measuring the height of the foam after predetermined times. Each experiment was repeated 4 times.

A 12% solution of both A1A1 and A2A2 spray dried milk powder was made by weighing 24 g powder and adding this to 176 g of Milli-Q water at 25 °C. The solution was mixed by inverting and shaking for at least 30 min for complete solubility before use. The reconstituted milk (50 g) was added to duplicate measuring cylinders containing the dissipation stones attached to the air hose and inserted into the bottom of the cylinder. The air pump was operated, and the air flow gauges set to 5 mL/min water for each cylinder. The height of the foam in each cylinder was measured at 30, 60, 90, 120 s after air pressure commenced. At 120 s, the air pump was turned off. The foam height was again taken at 30, 60, 90 and 120 s. The results are shown in Figure 4.

Although the invention has been described by way of example, it should be appreciated that variations and modifications may be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred in this specification.