IES20030564A2 - Process for preparing a milk powder - Google Patents

Abstract

A process for preparing a milk powder comprising among other components a substantial lactose component while still remaining a desirable product. A process for preparing a fat-filled milk powder comprising a substantial lactose component is also disclosed. The lactose is obtained by subjecting acid whey to nanofiltration followed by ultrafiltration.

Description

The present invention relates to a process for preparing a milk powder comprising among other components a substantial lactose component and also relates to a milk powder produced by that process. The invention further relates to a process for preparing a fat-filled milk powder comprising a substantial lactose component and also refates to a fat-filled milk powder produced by that process.

It is well known to use whey or acid whey in the production of milk powders, and this use has the following advantages: a) the powders are cheaper to produce as less skim milk is required and therefore more powder may be produced per unit of skim milk available to the processors. b) the use of whey in the production of the milk powder provides a cost efficient 0 method of utilising whey which is the result of casein production.

In the specification the term “nanofiltration” is used to describe the process of pressure driven membrane separation of electrolytes. In the specification the term “ultrafiltration” is used to describe the separation of colloidal or very fine solid materials by filtration through microporous or semipermeable membranes. When whey is subjected to ultrafiltration it is separated into whey protein concentrate (WPC) and lactose permeate. The whey protein concentrate is a valuable product and can be used as an ingredient in the manufacture of other products such as infant formulae, nutritional beverages, sports nutrition, yoghurt and confectionary products.

Lactose permeate, on the other hand, is considered to be a product of limited value.

In the specification the term “lactose permeate” refers to the lactose which passes through the membrane during ultrafiltration, and is hereinafter referred to as “lactose”.

US Patent No. 4,001,198 discloses a method of separating lactose constituents from mW—mnnr- T-iim·--- . i...·..·..· .__ OPEN TO PUBLIC INSPECTION UNDER SECTION 28 AND RULE 23 CTCL IE OS 0 5 64 - 2 whey by ultrafiltration. US Patent No. 4,497,836 discloses the ultrafiltration of whey to produce a protein-rich retentate fraction and a lactose-rich permeate fraction.

US Patent No. 5, 966,847 discloses a milk substitute composition prepared either from whey solids or a combination of whey solids and added lactose. US Patent Publication No. US2002/0098273 discloses a process for the manufacture of an evaporated milk product from a whey product, in which the whey is optionally partially substituted with lactose. The disadvantage of these compositions and processes for preparation is that the whey can only be partially substituted by lactose in order to achieve a product having desirable properties.

Although it has been previously recognised that whey can be partially substituted by lactose, it has up until now not been possible to achieve a milk powder of the desired quality where whey has been completely substituted by lactose.

The main difficulties in replacing whey with lactose are in achieving a desirable product in terms of physical, chemical and organoleptic properties and shelf life. Additionally, there is further difficulty, in that lactose is a very hygroscopic product which usually must be dried and further rehydrated before use. This is also a costly procedure.

There is therefore a need for a milk powder which can be produced from lactose and does not require any addition of whey, while still remaining a desirable product.

Statements of Invention According to the invention, there is provided a process for preparing a milk powder comprising; a skim milk liquid in a quantity sufficient to supply between 50% and 80% of the solids by weight of the milk powder; nanofiltering a liquid acid whey to produce a concentrated acid whey having 20% to 25% solids by weight; IE nJ 0 5 6 4 - 3 ultrafiltering the concentrated acid whey to provide lactose; neutralising the lactose to a pH of between 6.4 and 6.7; adding the lactose to the skim milk in a quantity sufficient to supply between 2% and 20% of the solids by weight of the milk powder; evaporating the mixture of skim milk and lactose to form a liquid having between 34 and 52% solids by weight; pasteurising the liquid; homogenising the liquid; spray drying the liquid to produce a partially dried milk powder; spraying lecithin at between 0.1% and 0.3% by weight of the milk powder on •to the partially dried milk powder while further drying the milk powder to a moisture content of less than 3% by weight of the milk powder; and storing the dried milk powder.

The advantage of using lactose in the preparation of milk powder is that it allows production of the powder at a reduced cost. A further advantage is that it provides a use for what is commonly recognised as a commercially valueless product. The aforementioned difficulties in replacing whey with lactose are overcome by using nanofiltered acid whey as the raw material for ultrafiltration which produces lactose which is not as susceptible to spoilage and development of off-flavours typical in lactose derived from cheese whey.

An additional product of acid whey ultrafiltration is whey protein concentrate which is a valuable product and can be dried and used as a valuable ingredient for nutritional products such as infant formulae and sports nutrition products. ΙΕ α 3 05 6 4 - 4 The advantage of nanofiltering the acid whey is that it produces a concentrated acid whey as the raw material for ultrafiltration which also helps in overcoming problems of rapid spoilage and development of off flavours. Additionally nanofiltration of the acid whey removes ions, thereby rendering the resultant powder more palatable. Furthermore nanofiltration allows for more cost effective storage and transportation.

The advantage of ultrafiltering the acid whey is that it produces a concentrated stream'of lactose that is easy to handle and cost-efficient to transport.

The advantage of lecithin is that it emulsifies the milk powder.

In one embodiment of the invention, prior to evaporation between 1% and 4% of sugar and buffering salt by weight of the milk powder are mixed with the skim milk and neutralised lactose.

Preferably, the sugar and buffering salt provide between 2% and 3% by weight of the milk powder. Preferably the ratio of sugar to buffering salt is approximately 20:1.

Further, preferably the buffering salt is di-sodium orthophosphate.

Ideally ultrafiltration is carried out at a temperature not exceeding 10°C.

The advantage of carrying out ultrafiltration at a temperature of 10°C or less is that protein denaturation, bacterial growth and membrane fouling are minimal under these conditions.

Preferably, the lactose is neutralised by the addition of potassium hydroxide.

Ideally the liquid is pasteurised at approximately 74° C for between 13 and 17 seconds and then at approximately 81 ° C for between 0.75 and 1.25 seconds.

Preferably the lactose provides approximately 13% solids by weight of the milk powder.

IE 0 3 05 6 4 - 5 Ideally the lecithin comprises approximately 0.2% solids by weight of the milk powder.

Preferably the skim milk provides approximately 79% solids by weight of the milk powder.

Ideally the skim milk and lactose liquid has between 34% and 52% solids by weight.

In a further embodiment of the invention vegetable oil is added to the liquid after evaporation in a quantity sufficient to provide between 26% and 34% solids by weight of the milk powder to form a fat-enriched liquid, wherein the resultant powder is a fatfilled milk powder.

Preferably the vegetable oil provides approximately 30% solids by weight of the fat filled milk powder.

Ideally the skim milk provides approximately 53% solids by weight of the fat-filled milk powder.

Preferably the fat-enriched liquid has between 50% and 54% solids by weight.

Detailed Description of the Invention The invention will be more clearly understood from the following description of one process according to the invention described with reference to Figs. 1 and 2 of the drawings which outlines, in flow diagram form, the process according to the invention.

All of the equipment used in carrying out the process is well known equipment and accordingly does not require any further description. However, one item of equipment not normally used in this type of process, although it is a well known piece of equipment in other processes, is a nanofiitration plant which is a pressure driven membrane separator for electrolytes. The ultrafiltration step is performed using standard ultrafiltration equipment, however it is carried out at temperatures of 10°C - 6 IE 03 05 6 4 or less.

Referring to the drawings, in step 1, skim milk is stored. Sugar is also stored in the store in step 2, while acid whey, in step 3, is taken and stored as a by-product from a casein production plant and then, in step 4, is nanofiltered to remove approximately one third of the concentration of potassium and sodium ions in the acid whey as well as approximately two thirds of the concentration of chloride ions to provide partially demineralised acid whey. The acid whey liquid is concentrated to have a solids concentration of 20% to 25% by weight, in comparison to the original solids concentration of the order of 5% by weight.

Then, in step 5, the concentrated acid whey liquid is subjected to ultrafiltration to provide lactose permeate. Whey protein concentrate is also produced as the retentate fraction.

The lactose is stored in step 6. It is possible to store the lactose for longer periods of time before it is neutralised. This is due to the lactose being in an acidic form which renders it less susceptible to microbial spoilage. Then, in step 7, the lactose is neutralised by the addition of potassium hydroxide, the potassium hydroxide usually of a concentration of 35% by volume. The lactose is neutralised to a pH in the range 6.4 to 6.7 preferably just prior to use. In step 8, skim milk from the store, is added to a mixer so as to be sufficient to supply between 50% and 80% of solids by weight of the final milk powder produced. A sufficient quantity of the neutralised lactose is delivered from the store to supply between 2 and 20% of the solids by weight of the milk powder when it is finally produced. Finally, between 1% and 4% of sugar and buffering salt by weight of the milk powder is added in the ratio of 20:1 and mixed with the lactose and concentrated skim milk.

Then, in step 9, evaporation of the lactose and skim milk liquid is carried out to provide a liquid having between 34% to 52% by weight solids. Optionally in step 10, vegetable oil is stored. Then, in step 11, the partially evaporated lactose and skim milk are optionally mixed with vegetable oil. The amount of vegetable oil added is usually in a quantity sufficient to provide between 26% and 34% solids by weight of the milk powder. This mixture, in step 11, then provides a liquid having between 48% IE 0 3 05 6 4 - 7 to 60% by weight solids. Then, in step 12, the liquid is pasteurised. This is usually carried out at approximately 74°C for between 13 and 17 seconds and then at approximately 81 °C for between 0.75 and 1.25 seconds.

Then, in step 13, the pasteurised liquid is homogenised in a standard two-stage homogenisation process and then, in step 14, is delivered to a spray dryer where a milk powder is formed. Then, in step 15, lecithin is delivered from a previous store to a horizontal fluid bed dryer, where the lecithin comprising between 0.1 % and 0.3% by weight of the milk powder is sprayed onto the milk powder as it is further dried in step 16. Then, in step 17, the dried milk powder which has been dried to less than 3% moisture is stored.

Generally, the skim milk provides somewhat of the order of 50 to 80% of the solids of the final milk powder. The lactose provides more than 2% and up to 20%. The solids provided by the vegetable oil is usually of the order of 26 to 34% and the solids provided by the sugar and buffering salt is usually about 2% to 3%. Lecithin is generally added at the rate of 0.2% of the final product.

Table 1 gives the composition of raw materials showing the composition of a final milk powder.

Table 1 : Composition of raw materials showing contribution to final milk powder.

Composition % By Weight Skim milk 79% Lactose 15% Sucrose 3% Leicithin 0.2% Moisture 2.8% Weight of milk powder 100% IE Ο 3 Ο 5 6 4 - 8 Table 2 gives the composition of raw materials showing the composition of a final fatfilled milk powder.

Table 2: Composition of raw materials showing contribution to final fat-filled 5 milk powder.

Composition % By Weight Skim milk 53.5% Lactose 12.0% Vegetable Oil 30.0% Sucrose 2.0% Lecithin 0.2% Moisture 2.3% Weight of milk powder 100.0% A fat-filled milk powder was prepared with lactose in accordance with the invention 10 and compared with a standard fat-filled milk powder prepared without lactose. Table below gives the chemical analysis of the milk powder, while Table 4 gives the physical analysis and Table 5 the microbiological analysis.

Table 3: Chemical Analysis Compositional requirement Fat-filled milk powder without lactose Fat-filled milk powder with lactose Moisture (%) 3.0% 3.0% Sugar 2.0% 2.0% Free fat (%) 3.0% max 3.0% max Vitamin A (I.U./1 OOg) 2500 min 2500 min Vitamin D3 (I.U./100g) 350 min 350 min IE Ο 3 0 5 6 4 - 9 Table 4: Physical Analysis Compositional requirement Fat-filled milk powder without lactose Fat-filled milk powder with lactose Bulk density (g/ml) 0.5 0.5 Solubility Index (mis) Less than 1.25 Less than 1.25 Sediment Disc A Disc A Acidity Less than 0.125 Less than 0.125 Taste Bland clean / full bodv Bland clean / full bodv Sink (s) 15 max 15 max Solubility (relative) No fleck / no grit No fleck / no grit Tea/Coffee test No lumps / scum No lumps / scum Whey Protein Nitrogen Index (WPN1) 2.5 - 6.0/g 2.5 - 6.0/g Disc A is a term used in the industry which means that a solution of the product is filtered through a disc and compared to a standard. Disc A is the highest standard and means that there are no burnt particles.

Table 5: Microbiological analysis Compositional requirement Fat-filled milk powder without lactose Fat-filled milk powder with lactose Total bacterial count Less than 50,000 / g Less than 50,000 / g Yeast Less than 50 / g Less than 50 / g Mould Less than 50 / g Less than 50 / g Conforms Absent in 1 g Absent in 1 g Salmonella Absent in 375 g Absent in 375 g E-Coli Absent in 0.1 g Absent in 0.1 g IE 0 3 0 5 6 4 The above results indicate that the fat-filled milk powder with lactose as prepared in accordance with the invention has desirable properties in that favourable results were achieved in terms of chemical, physical and microbiological analysis.

In the specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms “include, includes, included and including” or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments described above but may be varied within the scope of the claims.

Claims (5)

1. A process for preparing a milk powder comprising; 5 a skim milk liquid in a quantity sufficient to supply between 50% and 80% of the solids by weight of the milk powder; nanofiltering a liquid acid whey to produce a concentrated acid whey having 20 to 25% solids by weight; ultrafiltering the concentrated acid whey to provide lactose; neutralising the lactose to a pH of between 6.4 and 6.7; 15 adding the lactose to the skim milk in a quantity sufficient to supply between 2% and 20% of the solids by weight of the milk powder; evaporating the mixture of skim milk and lactose to form a liquid having between 34 and 52% solids by weight; pasteurising the liquid; homogenising the liquid;

2. 5 spray drying the liquid to produce a partially dried milk powder; spraying lecithin at between 0.1% and 0.3% by weight of the milk powder on to the partially dried milk powder while further drying the milk powder to a moisture content of less than 3% by weight of the 3.0 milk powder; and storing the dried milk powder. A process for preparing a milk powder substantially as described herein, with IE 0 3 05 6 4 - 12 reference to and as illustrated in the accompanying drawings.

3. A process for preparing a milk powder as claimed in claims 1 or 2 further comprising adding vegetable oil to the liquid after evaporation in a quantity sufficient to provide between 26% and 34% solids by weight of the milk powder to form a fat-enriched liquid, wherein the resultant powder is a fatfilled milk powder.

4. A process for preparing a fat-filled powder substantially as described herein, with reference to and as illustrated in the accompanying drawings.

5. A milk powder produced by the process as claimed in any preceding claim.