WO2001008502A1

WO2001008502A1 - Reduced fat whey protein concentrate and method of manufacture

Info

Publication number: WO2001008502A1
Application number: PCT/NZ2000/000140
Authority: WO
Inventors: Robert Philip Boswell; Joanne Campbell Hutchinson
Original assignee: New Zealand Co-Operative Dairy Company Limited
Priority date: 1999-07-29
Filing date: 2000-07-27
Publication date: 2001-02-08
Also published as: AU6326200A; EP1204328A4; JP2003505097A; UY26262A1; HK1047016A1; CA2379169A1; AR024983A1; EP1204328A1; AU773344B2

Abstract

This invention relates to reduced fat whey protein concentrate (WPC) and a method of producing such a WPC. The method of the invention involves concentrating the solids content of whey to produce an intermediate WPC, diluting the intermediate WPC with water to an ionic strength no greater than a preselected ionic strength, adjusting the pH of the diluted intermediate WPC to within the range 3.8 to 5.0, holding the pH at that level for a period to optimise formation of a floc, and removing the floc to leave a reduced fat WPC supernatant. The resulting WPC has a fat content of ≤ 4%, and preferably ≤ 1%. The method has particular application for producing a reduced fat WPC from sweet whey which has functional characteristics similar to those of a conventional WPC derived from acid whey. In addition, the method may produce a reduced fat WPC, from acid or sweet why having functional characteristics and a composition similar to those of a whey protein isolate (WPI).

Description

REDUCED FAT WHEY PROTEIN CONCENTRATE AND METHOD OF MANUFACTURE

TECHNICAL FIELD

This invention relates to reduced fat whey protein concentrate (WPC) and a method of producing such a product, preferably, although not exclusively, from a sweet whey.

BACKGROUND

Whey Protein Concentrates (WPC) and Whey Protein Isolates (WPI) are two of the major whey protein product categories. WPC typically contains > 35% protein and > 4% fat, while WPI contains > 80% protein and < 2 % fat. The high protein and low fat content of WPI imparts greater functional attributes and a preferred composition as compared to WPC. As a result, WPI commands a higher market value. However, the processes used to manufacture WPI are very expensive and the yield is low (generally 50-60% for ion exchange WPI, 50-75 % for microfiltration WPI) .

WPC have many different uses. Those uses may broadly be divided into two categories, one being nutritional- based uses and the second being functional-based uses. The nutritional-based uses would include, for example, infant formulae, enteral formulae, and sports drinks. The functional-based uses include, for example, for gelling, whipping, emulsification and other valuable properties for baking products.

Functionality has been defined by Pour-El, A. ( 1 981 , "Protein Functionality: classification, definition, and methodology", Protein Functionality in Foods, USA) as 'any property of a food or food ingredient except its nutritional ones that affect its utilisation'. Functional properties of a protein ingredient are influenced by the composition of the ingredient, the composition of the food system it is to be used in, and by the processing conditions required to manufacture this food system. The majority of functional characteristics of ingredients can be categorised into hydration related (dispersibility, solubility, swelling, viscosity, gelation) and surface related (emulsification, foaming, adsorption at air-water and oil- water interfaces) properties.

Traditionally, WPC is derived from whey which is the by-product of either acid (mineral acid or lactic whey) or sweet (cheese or rennet whey) coagulation of milk protein from milk in the manufacture of cheese or casein. The standard methods for producing WPC from acid or sweet whey are well known and are discussed, for example in United States patent specification US 4,200,662.

Acidification of milk to a pH of about 4.6 causes casein to become insolubilised and to coagulate as in, for example, casein (mineral acid casein or lactic casein) or certain cheese types (cottage cheese). The by-product removal of the casein curd, cheese curd, is known as acid whey. The alternative method of producing whey is by the addition of rennin and/or pepsin, proteolytic enzymes, to cause coagulation of casein. The resulting whey, after removal of the coagulated casein, is known as sweet or cheese whey.

To produce a WPC the acid or sweet whey is concentrated to produce a product having nominally 35 % whey protein solids. The process of concentration may involve delactosing, electrodialysis, reverse osmosis, gel filtration or ultrafiltration. In several applications, WPC has a lower functional performance than WPI. However, in some applications, acid WPC has a superior functionality as compared to WPI. Typically, cheese WPC has an inferior functional performance as compared to acid WPC. This is thought to be due to the difference in fat content, where cheese WPC typically has a higher fat content as compared to acid WPC. Cheese WPC has a lower market value than acid WPC and WPI. An improvement in functionality is expected to increase the market returns for cheese WPC. In addition, improved functional characteristics may also be achieved for acid WPC if the fat content could be reduced to a level similar to that for WPI.

Thus, it is an object of the present invention to provide a WPC and/or method of its manufacture which reduces or overcomes at least some of the abovementioned problems, or which at least provides the public with a useful alternative.

Other objects of the invention may become apparent from the following description which is given by way of example only.

STATEMENT OF THE INVENTION

According to one aspect of the present invention there is provided a method for producing a WPC having a fat content of no greater than 4%, from whey, the method including the steps of:

concentrating the solids content of whey to produce an intermediate WPC, diluting the intermediate WPC with water to reduce the ionic strength, adjusting the pH of the diluted intermediate WPC to within the range substantially 3.8 to 5.0, holding the pH at that level for a period to optimise formation of a floe, and removing the floe to leave a reduced fat WPC supernatant.

One preferred form of the process of the invention may further include controlling the temperature of the diluted intermediate WPC prior to pH adjustment.

Preferably, the temperature may be increased to substantially 50°C. Alternatively, it may be reduced to substantially 1 0°C.

In one preferred form of the process of the invention the pH may be adjusted to substantially 4.2 to 4.4.

Preferably, the pH may be adjusted by the addition of a mineral or organic acid, preferably citric acid.

Preferably, the temperature may be increased to substantially 50°C and the removal of floe may be by a clarifier.

In a further preferred form the whey may be concentrated to a solids concentration in the range substantially 1 2 to 30% total solids, more preferably > 1 8% and in one preferred form substantially 23% .

Preferably, the solids concentration may involve ultrafiltration.

Preferably, the intermediate WPC may be diluted with water at a ratio in the range substantially 1 :3 to 1 :20, retentate:water. Preferably, the intermediate WPC having a solids content of > 1 8% total solids may be diluted in the ratio substantially one part retentate to nine parts water. Preferably, that water is demineralised water.

Preferably, the starting whey for use in the process of the invention is sweet whey.

In a further preferred form the process of the invention may include further processing of the reduced fat WPC supernatant to concentrate the solids content and thereafter prepare a dry powder product by conventional means.

According to a further aspect of the present invention there is provided a WPC derived from a sweet whey, having functional characteristics at least equivalent to those of a WPC derived from acid whey by conventional means.

According to a further aspect of the present invention there is provided a WPC derived from acid or sweet whey having functional characteristics substantially equivalent to those of a conventional WPI.

Other aspects of the present invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings and/or Examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 : is a flow diagram of the general features of the process of the invention, in one preferred form; Figure 2: is a flow diagram of one specific embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The process of the invention is broadly identified in Figure 1 , and involves the processing of whey (preferably sweet whey) to produce a reduced fat WPC. As indicated in Figure 1 the process, in broad terms, involves concentrating the solids component of the whey, preferably by an ultrafiltration process, to produce an intermediate WPC with a solids content in the range 1 2% to 30% total solids. The solids content is preferably > 1 8%, and 30% is a maximum practical content. The intermediate WPC is then diluted with water to produce a WPC retentate with a lower ionic strength. The dilution ratio will vary depending on the solids content of the intermediate WPC, but will be in the range 1 :3 to 1 :20, retentate:water. With a preferred solids content > 1 8% a ratio of about 1 :9 is appropriate. The pH of the diluted retentate is then adjusted to a selected level in the range 3.8 to 5.0, the diluted retentate is held under those conditions for a specified period during which a floe forms and the floe, which contains a high proportion of fat, is then separated to leave a low fat supernatant which can subsequently be processed to produce, for example, a dried, powder, reduced fat WPC.

The end product has a reduced lactose content, as well as a reduced fat content, and this combination results in an increase in protein content. Starting with a sweet whey the fat content may be reduced to 1 % or lower. Conventional sweet WPC has a fat content of 6 to 7% and conventional acid WPC has a fat content of generally above 4%. Thus, reductions in fat content of a sweet WPC produced from the process of the invention to 4% or less provides at least functional equivalence to a conventional acid WPC product. Reductions below 4% offer functional advantages which, as the fat content is reduced to 1 % or less, approach the functional performance of WPI. It will be appreciated, therefore, that the functional characteristics of an acid WPC may also be improved by the process of the invention.

Specific details of the process of the invention, and the product resulting therefrom, in one preferred embodiment, are now provided by way of example.

Example

Figure 2 summarises the process employed in a pilot plant trial.

Sweet whey was dosed with citric acid to reduce the pH to 6.00.

The whey was then thermalised by heating indirectly to 73°C and holding for 1 5 seconds, before cooling regeneratively to 55°C. The thermalised sweet whey was stored prior to ultrafiltration (UF). UF was used to increase the total solids (TS) (brix) of the whey from about 6% to 23 % using 1 3 loops of 1 0kD spiral wound membranes. Diafiltration (DF - the addition of demineralised water to allow a high concentration ratio to be used) was used after loop 8. After UF, the retentate was chilled to about 4°C, for microbial control, prior to storage.

100 L of this sweet whey retentate (at 23% brix) was then diluted using 900 L of demineralised water at about 50°C; an approximate ratio of 1 0% retentate to 90% water. This mixture, having a preferred ionic strength for the process, was agitated to ensure a homogenous solution. Once mixed, the dilute retentate was heated to 50°C using indirect heating. The heated dilute retentate was then acidified. Citric acid was dosed in-line, to reduce the pH from approximately 6.00 to approximately 4.30. The solution was then held for about 1 5 minutes prior to clarification using a pilot clarifier (GEA-Westfa a model KNA3). This was run at 750 L/hr, 4-4.5 bar back pressure, with continuous discharge, and two 0.5mm nozzles to separate the floe from the supernatant.

It will be appreciated that other acids or acid combinations may be employed in the acidification step. Furthermore, whilst the preferred pH may be about 4.30, floe formation may be achieved, although perhaps less effectively, with a pH in the range 3.8 to 5.0. Adjustment of the time the solution is held may be appropriate to optimise floe formation for removal.

The supernatant was then heated to 50°C prior to UF through 5kD spiral wound membranes. This second UF step concentrated the product to about 20% TS (brix). The volume concentration fraction (VCF) used was approximately 1 0. No diafiltration water was added.

The retentate was then pH adjusted to about 6.8 (to give a pH in the final powder of 6.8 - 7.0) using a mix of KOH and NaOH prior to spray drying.

It will be appreciated by those skilled in the art that different processes may be involved in the initial solids concentration of sweet whey, resulting in higher or lower proportions of solids than described in this example. To produce the required ionic strength of the WPC retentate will then require a greater or lesser rate of dilution. It will also be appreciate by those skilled in the art that alternative methods may be employed for separating the floe from the supernatant, for example gravity settling, filtration or hydrocyclones.

Whilst the process described in the example includes the step of heating the diluted WPC retentate to about 50°C, the optimum temperature for the process will depend on a number of variables, including the holding time and the method of separation used. The process may, for example, involve chilling of the diluted WPC retentate to about 1 0°C prior to acidification, rather than heating, where the separation method is other than by clarification.

Product Composition

Table 1 provides compositional data for product manufactured using the process of the invention in a pilot plant.

Table 1

The table shows that the by-product floe has a fat content of about 1 3% . The dried WPC end-product has a protein content of about 87% and a fat content of only 1 % . Functional Testing

End-product from the pilot plant trial was assessed for functional characteristics (solubility, viscosity, gelation (aqueous and brine), foaming (with sugar and without sugar), and performance in an acid beverage rapid test) and in model food systems (meringues, infant formula and yoghurt) . The results were as follows. 1 . Functional Test Systems a) Solubility.

It is desirable for products to have good solubility over a wide pH range to avoid sediment forming in final product applications, particularly beverages. Table 2 illustrates the solubility of each sample over a range of pH's. The pilot plant sample had a much greater degree of solubility than that of an acid WPC. This is shown by the narrow pH range over which sediment formed, and also by the small amount of sediment which formed in comparison to the Acid WPC.

Table 2. Solubility results - amount of sediment formed at varying pH values for Pilot Plant Sample and Acid WPC.

b) Viscosity.

The relationship between viscosity and total solids for the pilot plant trial sample as compared to Acid WPC is shown below. Viscosity is a measure of rheological properties and is important in applications for example, sauces, gravies and salad dressings. The viscosity characteristic for the pilot plant sample is equivalent to acid WPC.

250

o 200

CM o

5 150 _@ 10% TS B20% TS D 30% TS

™ 100 _π40% TS

0- ε 50

o o to

0

Acid WPC Pilot Plant Sample 0 Foaming.

Foaming is important for applications such as, for example, cakes and meringues. Table 3 shows that the pilot plant sample has a maximum overrun greater than that of the target product for the application (WPI) in the foaming system without sugar. In both systems, the pilot plant sample has greater foam stability than WPI.

Table 3. Functional results for a pilot plant sample and a WPI in a foaming test system.

d) Gelation.

Gelation is a functional characteristic important in systems, for example, yoghurts and restructured meats. Table 4 illustrates the similarity between the pilot plant sample and Acid WPC (target product) in 0% NaCI gels. No data was available for comparison in 0.4% NaCI systems, and it can be seen that the pilot plant sample does not perform as well overall in the 2 % NaCI system. Table 4. Functional results for a pilot plant sample and Acid WPC in gelation test systems.

e) Acid Beverage Rapid Stability Test

Absorbance of pilot plant sample and WPI over range of pH's after heating at 80°C for 20 minutes is shown below. For acid beverages, pH 3.8 is the most relevant. It can be seen that the two products, where WPI is the target product for the application, are very similar in absorbance over the pH range.

3.5

WPI Riot Plant Sample

Sediment is undesirable and was observed in the pilot plant sample only at pH 4.0 ( 14.5 ml sediment), compared to the WPI which had 2ml sediment at pH 4.0 and 1 ml sediment at pH 3.8.

2. Model Food Systems.

Set Yoghurt.

Table 5 shows the similarity between the pilot plant sample and acid

WPC in a set yoghurt system.

Table 5. Free whey, total solids content (TS) and Texture Analyser results for set yoghurt samples.

Peak 1 - represents elasticity / bπttleness

Area - calculated from the area between Peak 1 and Peak 2, represents mouthfeel / body

b) Stirred Yoghurt Table 6 shows the similarity between the pilot plant sample and

Acid WPC in a stirred yoghurt system.

Table 6. Viscosity, drained syneresis and total solids (TS) results for stirred yoghurts.

0 Infant Formula.

The following results show the similarity between the pilot plant sample and Acid WPC in a model infant formula system.

Acid WPC Pilot Plant Sample

Heat Coagulation Time 7.5 minutes 7.5 minutes

Mean particle diameter 1 1 (d 0.9) 1 5 (d 0.9)

(Malvern Mastersizer)

Table 7. Particle Size distribution of pilot plant sample and Acid WPC as determined using the Malvern Mastersizer.

Thus, it can be seen that the process of the present invention enables the processing of a whey (preferably a sweet whey) in a manner which produces a readily removable floe containing a substantial portion of the fat, leaving a WPC end-product having a high protein and reduced fat content, and with improved functional performance. The resulting product, when derived from a sweet whey may have a functional performance at least equivalent to that of a conventional acid WPC, and a similar composition. Furthermore, a WPC product, whether derived from sweet or acid whey, may be produced with functional performance substantially equivalent to that of a WPI Where in the foregoing description reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example and with reference to possible embodiments thereof it is to be understood that modifications or improvements may be made thereto without departing from the scope or spirit of the invention.

Claims

1 . A method for producing a WPC having a fat content of no greater than 4%, from whey, the method including the steps of:

concentrating the solids content of whey to produce an intermediate WPC,

diluting the intermediate WPC with water to reduce the ionic strength,

adjusting the pH of the diluted intermediate WPC to within the range substantially 3.8 to 5.0,

- holding the pH at that level for a period to optimise formation of a floe, and

removing the floe to leave a reduced fat WPC supernatant.

2. A method according to claim 1 wherein the pH is adjusted to within the range substantially 4.2 to 4.4.

3. A method according to claim 2 wherein the pH is adjusted by the addition of a mineral or organic acid.

4. A method according to claim 3 wherein the pH is adjusted by the addition of citric acid.

5. A method according to any one of the preceding claims wherein the solids content of the whey is concentrated by ultrafiltration.

6. A method according to any one of the preceding claims wherein the whey is concentrated to a solids concentration of in the range substantially 1 2 to 30% total solids.

7. A method according to claim 6 wherein the solids concentration is

> 18% total solids.

8. A method according to claim 7 wherein the solids concentration is substantially 23% total solids.

9. A method according to any one of claims 6 to 8 wherein the intermediate WPC is diluted with water at a ratio in the range substantially 1 :3 to 1 :20, retentate:water.

10. A method according to claim 8 wherein the intermediate WPC is diluted with water in a ratio of substantially 1 part retentate to 9 parts water.

1 1 A method according to either claim 9 or claim 10 wherein the water is demineralised water.

1 2 A method according to any one of the preceding claims wherein the starting whey is sweet whey.

1 3. A method according to claim 1 further including the step of controlling the temperature of the diluted intermediate WPC prior to pH adjustment by increasing the temperature to substantially 50°C

14. A method according to claim 1 further including the step of controlling the temperature of the diluted intermediate WPC prior to pH adjustment, by reducing the temperature to substantially 10°C.

1 5. A method according to claim 1 3 wherein the floe is removed by a clarifier.

1 6. A method according to any one of the preceding claims further including the step of processing the reduced fat WPC supernatant to concentrate the solids content, and thereafter prepare a dry powder product.

1 7. A reduced fat WPC having a fat content < 4% and manufactured in accordance with a method of any one of claims 1 to 1 6.

1 8. A reduced fat WPC manufactured according to a method of claim 1 2 and having functional characteristics at least equivalent to those of a conventional WPC derived from acid whey by conventional means.

1 9. A reduced fat WPC manufactured according to a method of any one of claims 1 to 1 1 , derived from an acid whey and having functional characteristics substantially equivalent to those of a conventional WPI.

20. A method of producing a reduced fat WPC substantially as herein described and with reference to the accompanying figures and/or examples.

21 . A reduced fat WPC substantially as herein described and with reference to the accompanying figures and/or examples.