IE84778B1 - Process for producing a fat-filled milk powder - Google Patents

Abstract

ABSTRACT The present invention relates to a process for producing a fat-filled milk powder comprising, among other components, a substantial whey component and further relates to a milk powder produced by that process.

Description

lntroduction The present invention relates to a process for producing a fat-filled milk powder comprising, among other components, a substantial whey component and further relates to a milk powder produced by that process.

Acid whey which is produced as a by-product from casein manufacture contains a much higher concentration of sodium, potassium and chloride ions than whey which is a by-product of cheese production. This makes the taste unpalatable and prevents its use, to any significant level. in most applications. Thus, as well as being effectively a low value by-product, it is also costly to dispose of.

One of the ways in which whey can be used is in the production of milk powders.

Using whey as one of the components 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 method of utilising whey which is the result of casein production.

The main difficulty in replacing a portion of the skim milk powder with whey is achieving a desirable product in terms of physical, chemical and organoleptic analysis and shelf life.

US Patent No. 5,906,847 discloses a method for preparing a liquid milk substitute composition comprising among its components a whey solids powder in the amount of 5% to 9% by weight. The disadvantage of this process, however, is that the whey solids must be dissolved in an aqueous medium. The need to dissolve the whey solids increases the processing time as well as manpower and processing plant requirements.

However, it must be pointed out that this US Patent Specification is directed towards producing liquid milk substitutes. What is required is to produce a dried milk powder which is fat-filled and which, when. for example, added to hot drinks, will mix correctly with the drinks without lumps or any separation of the components. It is also necessary, when using acid whey, to make sure that the organoleptic properties are satisfactory. For example, it is important that the acid whey does not leave anything other than a clean aftertaste.

U.K. Patent No. 1,274,390 discloses a powdered milk product and a process for production thereof. The disadvantage of this process is that the whey powder is blended with a milk powder thereby restricting the amount of whey which can be added as a percentage of dry solids. The present invention overcomes this problem as the whey is added to liquid skim milk and therefore a substantially higher proportion of whey may be added.

U.K. Patent Application No.9325442.3 discloses a process for preparing a dairy product and the product produced by that process wherein a substantial part of the animal fat usually present is replaced by vegetable fat. The disadvantage of this process, however, is that only a small amount of whey is used as its function in the dairy product is to act as a stabiliser so as to allow a high fat content. The present invention is to allow both a high whey content and a high fat content to be used.

U.S. Patent No. 5,518,751 discloses a process for the preparation of milk and milk powders having a long storage life. This process is particularly useful for the manufacture of milk for premature children, which will be enriched with unsaturated fatty acids, these fatty acids resulting in the rancidity of the milk. US. Patent No. 4,544,559 describes a nucleotide enriched humanised milk for infant nourishment and a process for the preparation thereof. The raw materials used in the manufacture of this humanised milk include a small proportion of whey which is distributed by a spreader. In the above documents, the amount of whey used in the respective processes is substantially less than that of the present invention.

Additionally, the nanofiltration of acid whey is not included in either process.

U.S. Patent No. 4,446,164 describes a whey based imitation milk composition. The type of whey used in this document is sweet whey, as opposed to acid whey which is utilised in the present invention. Furthermore, the sweet whey is not subjected to a nanofiltration process as in the present invention, thereby resulting in a lower solids concentration of the whey as compared to that of the present invention. The disadvantage of this process is that non-fat dry milk solids are used to form a basis for a dry blend. The portion of whey added as a percentage of the dry solids composition is therefore also substantially less than that of the present invention.

The present invention is directed towards overcoming the limitations of previous processes in that it allows the preparation of fat-filled milk powders wherein a substantial whey component is included without compromising the physical, chemical and organoleptic properties of the milk powder product.

Statements of Invention According to the invention, there is provided a process for preparing a fat-filled milk powder comprising:- a skim milk liquid in a quantity sufficient to supply between 45% and 60% of solids by weight of the final fat-filled milk powder produced; nanofiltering a liquid acid whey to produce an acid whey retentate having 20 to 25% solids by weight and in a quantity sufficient to supply between 10% and 15% of the solids by weight of the milk powder; neutralising the acid whey retentate to a pH of between 6.4 and 6.7; mixing between 1% and 4% of sucrose by weight of the milk powder with the concentrated skim milk and the neutralised whey retentate; evaporating the mixture of skim milk, sucrose and whey to form a whey and skim milk liquid having between 36% and 48% solids, by weight; adding vegetable oil to the whey and skim milk liquid in a quantity sufficient to provide 26% to 34% solids by weight of the milk powder; adding vitamins and colouring to the skim milk, whey and oil liquid to form a fat enriched liquid having between 48% to 60% by weight solids. pasteurising the fat enriched liquid; mixing and homogenising the pasteurised liquid; spray drying the pasteurised liquid to produce a partially dried milk powder; transferring the partially dried milk powder to a horizontal fluid bed dryer; spraying lecithin at between 0.1% and 0.3% by weight of the milk powder on the partially dried milk powder while drying it in the horizontal fluid bed drier to a moisture content of below 3% by weight of the milk powder; and storing the dried milk powder.

Preferably the skim milk liquid has been evapourated to form a concentrated skim milk liquid having 8.5% to 9.5% solids by weight.

In one example according to the invention, the skim milk provides between 50% and 55% solids by weight of the milk powder and preferably this percentage is approximately 53%. In accordance with the invention, ideally the liquid acid whey provides approximately 12% of solids by weight of the milk powder and this acid whey is often a by-product of a casein manufacturing process and contains potassium, sodium and chloride ions and the nanofiltration is carried out to remove of the order of one third of the potassium and sodium and two thirds of the chloride ions. Usually, the liquid acid whey from the casein process contains solids of the order of 5% by weight of the liquid acid whey. Preferably, the whey is neutralised by the addition of potassium hydroxide.

Ideally, the vegetable oil provides between 28% and 32% solids by weight of the milk powder and preferably the percentage solids are approximately 30%.

Further, in one embodiment of the invention, the sucrose provides approximately 2% by weight of the milk powder.

Ideally, the skim milk and whey liquid has between 40% and 44% solids by weight.

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

Ideally, the fat enriched liquid is pasteurised at approximately 74°C for between 13 and 17 seconds and at approximately 81° for between 0.75 and 1.25 seconds. ideally, the lecithin comprises approximately 0.2% solids by weight of the milk powder.

Detailed Descrigion 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 is a nanofilter which is a pressure driven membrane separator for electrolytes. The term "nanofi|tration" is the term used to describe the process of pressure driven membrane separation of electrolytes.

Referring to the drawings, in step 1. skim milk is stored. Sucrose 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. These are then removed from the whey liquid which is also now 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 neutralised by the addition of potassium hydroxide, the potassium hydroxide usually forming 35% by volume of the filtered whey liquid. The whey liquid is neutralised to a pH in the range 6.4 to 6.7.

The neutralised and concentrated whey liquid is then stored in step 6. In step 7, sufficient of the stored skim milk, is removed to a mixer so as to be sufficient to supply between 45% and 60% of solids by weight of the final fat filled milk powder produced. A sufficient quantity of the neutralised acid whey is delivered from the store to supply between 10 and 15% of the solids by weight of the milk powder when it is finally produced. Finally, between 1% and 4% of sucrose by weight of the milk powder is added and mixed with the liquid whey and concentrated skim milk.

Then, in step 8, evaporation of the whey and skim milk liquid is carried out. In step 9, vegetable oil has been previously stored, as has various additives in step 10, such as vitamins and colouring. Then, in step 11, the partially evaporated whey and skim milk, vegetable oil and additives are mixed together. The amount of vegetable oil added is usually in a quantity sufficient to provide 26% to 34% solids by weight of the milk powder. This mixture, in step 11, then provides a fat enriched liquid having between 48% to 60% by weight solids. Then, in step 12, the fat enriched 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 54% of the solids of the final milk powder. The nanoflltered whey provides more than 10%. The vegetable oil is usually of the order of 28 to 32% and sucrose usually about 2%, while the vitamins added are usually Vitamins A and D and do not add appreciably to the weight. 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 to a final % fat-filled milk powder.

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

Composition % By weight Milk 53.5% From Whey 12.0% Vegetable Oil 30.0% Sucrose 2.0% Lecithin and \/Itamins 0.2% Moisture _2_.__3% Weight of fat-filled milk powder 100.0% This milk powder then has a composition as given in Table 2 below. The milk powder produced by the process was uniform in composition and free flowing. Further, the powder was creamy-yellow in colour, free from lumps and free from visible dark particles.

TABLE 2 Composition % By weight Lactose 39.5% Vegetable Fat 30.0% Protein 19.5% Minerals 5.8% Sucrose 2.0% Lecithin 0.2% Moisture @ 100.0% Table 3 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 Analfiis Compositional Requirement Fat-filled milk powder Moisture (%) 3.0 (max) Sugar (%) 2.0 (+/- 0.5) Free fat (%) 2.0-3.0 (max) Vitamin A (|.U./100g) 2,500 (min) Vitamin D3 (|.U./100g) 350 (min) TABLE 4 Physical Analysis Compositional Requirement Fat-filled milk powder Bulk density (g/ml) 0.5 Solubility index (mis) Less than 1.25 Sediment Disc A Acidity (%) Less than 0.125 Colour Cream/yellow Taste Bland clean/full body Wettability: Sink (second) max Solubility (relative) No fleck/no grit Tea/coffee test No lumps/scum Whey Protein Nitrogen 2.5 — 6.0/g Index (WPNI) Disc A is a term used in the industry which means that a solution to 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.

Wettability refers to the ability of the milk powder to be wetted when in contact with a liquid.

TABLE 5 Microbiological analysis Compositional Requirement Fabfiued Mflk Powder Total bacterial count Less than 50.000/g Yeast Less than 50/g Mould Less than 50/g Coliforms Absent in 1 g Salmonella Absent in 3759 E-coll Absent in 0.1g In this particular example, the filtered acid whey was neutralised with 35% by volume of potassium hydroxide to yield neutralised whey with a pH of 6.6. The neutralised whey had a solids concentration of 25%. Then, prior to the adding of the vegetable Then, after the addition of the vegetable oil, the liquid then had a solids content of 51.3%. The pasteurising stage oil, the mixture was evaporated to 42% solids. took place at 74°C for 15 seconds and at 81°C for 1 second.

The use of nanofiltration removes the ions that cause problems and make dried milk powder, having acid whey incorporated therein, unpalatable. Also, the nanofiltration concentrate of the whey allows for more cost effective storage and transportation.

Various production trials have been carried out under different heating conditions and the fat-filled powder according to the present invention operated satisfactorily.

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 (1)

1.CLAIMS A process for preparing a fat-filled milk powder comprising:- a skim milk liquid in a quantity sufficient to supply between 45% and 60% of solids by weight of the final fat-filled milk powder produced; nanoflltering a liquid acid whey to produce an acid whey retentate having 20 to 25% solids by weight and in a quantity sufficient to supply between 10% and 15% of the solids by weight of the milk powder; neutralising the acid whey retentate to a pH of between 6.4 and 6.7; mixing between 1% and 4% of sucrose by weight of the milk powder with the skim milk and the neutralised whey retentate; evaporating the mixture of skim milk, sucrose and whey to form a whey and skim milk liquid having between 36% and 48% solids, by weight; adding vegetable oil to the whey and skim milk liquid in a quantity sufficient to provide 26% to 34% solids by weight of the milk powder; adding vitamins and colouring to the skim milk, whey and oil liquid to form a fat enriched liquid having between 48% to 60% by weight solids; pasteurising the fat enriched liquid; mixing and homogenising the pasteurised liquid; spray drying the pasteurised liquid to produce a partially dried milk powder; transferring the partially dried milk powder to a horizontal fluid bed dryer; spraying lecithin at between 0.1% and 0.3% by weight of the milk powder on the partially dried milk powder while drying it in the horizontal fluid bed drier to a moisture content of below 3% by weight of the milk powder; and storing the dried milk powder. A process as claimed in claim 1, in which the skim milk provides between 50% and 55% solids by weight of the milk powder. A process as claimed in claim 2, in which the percentage solids is approximately 53%. A process as claimed in any preceding claim, in which the liquid acid whey provides approximately 12% of solids by weight of the milk powder. A process as claimed in any preceding claim, in which the acid whey is a by- product of a casein manufacturing process and contains potassium, sodium and chloride ions and the nanofiltration is carried out to remove of the order of one third of the potassium and sodium and two thirds of the chloride ions. A process as claimed in claim 5, in which the liquid acid whey from the casein process contains solids of the order of 5% by weight of the liquid acid whey. A process as claimed in any preceding claim, in which the whey is neutralised by the addition of potassium hydroxide. A process as claimed in any preceding claim, in which the vegetable oil provides between 28% and 32% solids by weight of the milk powder. A process as claimed in claim 8, in which the percentage solids is approximately 30%. A process as claimed in any preceding claim, in which the sucrose provides approximately 2% by weight of the milk powder. A process as claimed in any preceding claim, in which the skim milk and whey liquid has between 40% and 44% solids by weight. A process as claimed in any preceding claim, in which the fat enriched liquid has between 50% and 54% solids by weight. A process as claimed in any preceding claim, in which the fat enriched liquid is pasteurised at approximately 74°C for between 13 and 17 seconds and at approximately 81°C for between 0.75 and 1.25 seconds. A process as claimed in any preceding claim, in which the lecithin comprises approximately 0.2% solids by weight of the milk powder. A process for preparing a fat-filled milk powder substantially as described in the section entitled “Detailed Description of the Invention”. A fat-filled milk powder produced by the process as claimed in any preceding claim.