Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

Подождите немного. Документ загружается.

Whole

milk

Separation

Skim milk

Coagulation Drying

Drying

Concentration

Neutralization

Evaporation

Crystallization

Ion exchange

Crystallization

Evaporation

Ultrafiltration

Churning

Buttermilk

Evaporation

Ultrafiltration

Curd

Caseinates

Buttermilk powder (BMP)

Whey powder

Demineralized whey powder

Whey protein concentrate powder

Whey protein isolates

Lactose

Full-cream milk powder (FCMP)

Skim-milk powder (SMP)

Milk protein concentrate (powder)

Casein

Anhydrous milk fat (AMF)

Butter

Cheese

Demineralization

Cream

Coagulation

Whey

fig0001 Figure 1 Milk ingredients. Reproduced with permission of the Australian Dairy Corporation.

Principal Spray-Dried Milk Powder

Products

0005 Skim, full-cream, and buttermilk powders are the

traditional milk powders and are the major milk

powders in the marketplace. The typical compos-

itions of these powders are given in Table 1. The

powders are dried to achieve specified standards for

various grades of milk powders (Table 2).

Production of Skim, Full-Cream, and Buttermilk

Powders

0006 The main steps in the commercial manufacture of

milk powders are: the preparation of the milk, heat

treatment of the milk, concentration by evaporation,

and spray drying. During the production of full-

cream milk powder, there is an additional step, in-

volving the homogenization of the concentrate prior

to drying. Figure 2 shows the main steps in the manu-

facture of milk powders. Where a powder with in-

stant properties is required, an agglomeration step is

included during powder manufacture.

0007 Preparation of milk This step defines the final

composition of the powder. For the production of

skim-milk powder, the milk is first separated into

skim milk and cream by centrifugal separation.

The skim milk should have a fat content of < 0.1%.

For full-cream milk powders, the milk is normally

standardized, generally by blending cream or skim

to obtain a fat content of 25–28% in the final powder.

Supplements such as vitamins and minerals may

be added to the skim or full-cream milk to enhance

the nutritional value of these powders. Buttermilk

powders are made from the aqueous fraction

remaining after churning of cream during buttermak-

ing or during manufacture of anhydrous milkfat.

0008Heat treatment of milk The milk has to receive a

heat treatment prior to concentration. A range of heat

treatments may be used. These range from low-heat

treatment (72



C for 15 s) for pasteurization to high-

heat treatments (e.g., 85



C for 30 min or ultrahigh-

temperature (UHT) at 140



C for a few seconds). A

primary purpose of the heat treatment is to achieve

a required microbiological specification. The heat

treatment also reduces the enzyme activity in the

milk and increases the shelf-life of the powder prod-

ucts. Another consequence of the heat treatment is the

denaturation of the whey proteins in milk. Appropri-

ate heat treatments can be used to develop desired

physical, chemical, and functional properties in milk

powder products.

0009Skim-milk powders are generally classified on the

basis of the heat treatment received during powder

manufacture. Although the heat treatment classifica-

tion is not used in the grading of milk powders, they

are used as a general guide to the selection of powders

for specific applications. The most commonly used

heat classification is that of the American Dried Prod-

uct Institute which is based on the amount of unde-

natured whey protein in the powder (Table 3). (See

Powdered Milk: Characteristics of Milk Powders.)

0010Concentration of milk This is the first stage for

removal of water from milk. The milk is concentrated

at a low temperature by vacuum evaporation. The

temperature of the milk reaches a maximum of 70



in modern evaporators. Generally, about 90% of the

water is removed by the evaporator, as removal of

tbl0002 Table 2 Specifications for milk powders

Constituent Skim-milk powder

Full-creammilkpowder

Buttermilk powder

Moisture (%) Max. 4.0 Max. 4.5 Max. 4.0

Fat (%) Max. 1.25 Min. 26.0, max. 40.0 Min. 4.5

Protein (%) Min. 30.0

Titratable acidity (%) Max. 0.15 0.10–0.18

Insolubility index Max. 1.25 ml Max. 1.0 ml Max. 1.25 ml

Scorched particles Not more than disc B (15.0 mg) Not more than disc B (15.0 mg) Not more than disc B (15.0 mg)

Bacterial estimate Not more than 50 000 per g Not more than 50 000 per g Not more than 50 000 per g

Extra-grade spray-dried powder.

Label should specify the minimum protein content.

Adapted from Standards for Grades of Dry Milks Including Methods of Analysis (1990). Bulletin 916. American Dairy Products Institute.

tbl0001 Table 1 Typical composition of milk powders

Constituent Skim-milk

powder

Full-cream

milk powder

Buttermilk

powder

Moisture (%) 3.0 2.25 3.0

Fat (%) 0.7 26.75 5.0

Protein (N 6.38: %) 36.0 26.0 34.0

Lactose (%) 51.0 38.0 48.0

Ash (%) 8.2 6.0 7.9

Calcium (%) 1.31 0.97 1.3

Phosphorus (%) 1.02 0.75 1.0

Adapted from Standards for Grades of Dairy Milks Including Methods of

Analysis (1990). Bulletin 916. American Dairy Products Institute.

4696 POWDERED MILK/Milk Powders in the Marketplace

water by evaporation requires 16–20 times less energy

per kg water than spray drying. The milk concentrate

of about 48–50% total solids is then fed into the

spray drier.

0011 Homogenization of milk concentrate Homogeniza-

tion of full-cream milk concentrates is carried out to

reduce the ‘free-fat’ content (i.e., solvent-extractable

fat) of the powder. During homogenization, the fat

globule size is reduced, proteins are transferred to the

surface of the globule, and the globule is stabilized.

Homogenization of the milk concentrate results in

powders with improved flow properties and resist-

ance to caking and clumping.

0012 Spray drying Spray drying transforms the fluid milk

concentrate that is fed into the hot air of the drier to a

powder. The moisture content of the spray-dried

powder is usually 3–4% (w/w). The main stages of

spray drying are atomization of the concentrate into a

spray through pressure nozzle atomizers or rotary

atomizers, the mixing of the atomized particles with

the hot air, the evaporation of moisture from the

surface of the particles, and separation of the powder

from the air. Single- and double-stage spray driers are

used in milk powder manufacture. Commercial milk

powders are typically dried to 4% moisture or less.

0013Agglomeration of milk powders For the production

of milk powders with instant properties, the milk

powders are agglomerated. This process yields large

powder agglomerates. The wettability and dispersi-

bility of powders are improved by agglomeration.

Surfactants (e.g., lecithin) may be used during ag-

glomeration of full-cream milk powders to improve

their instant properties in cold water. (See Agglomer-

ation; Drying: Spray Drying; Evaporation: Basic

Principles; Homogenization.)

Applications of Skim, Full-cream Milk, and

Buttermilk Powders

0014Milk powders are used in many applications.

Instant milk powders, which dissolve readily in

water, are used by consumers as a substitute for

fresh milk and in beverage mixes. Also available in

the market are a range of nutritionally enriched milk

powder products that have been tailored to meet the

needs of consumers at various stages of life. These

tbl0003 Table 3 Heat classification of skim-milk powder

Heat class Whey protein nitrogenindex (mg undenatured

whey protein N g

1

powder)

Low heat Not less than 6

Medium heat 1.51–5.99

High heat Not more than 1.5

Adapted from Standards for Grades of Dry Milks Including Methods of

Analysis (1990). Bulletin 916. American Dairy Products Institute.

Full-cream

milk

Separate

Cream

Churn

ButterButtermilk

Preheat

Evaporate

Dry

Buttermilk

powder

Preheat

Evaporate

Dry

Skim-milk

powder

Preheat

Evaporate

Homogenize

Dry

Full-cream

milk powder

Skim-milk

fig0002 Figure 2 Schematic diagram of manufacture of milk powders.

POWDERED MILK/Milk Powders in the Marketplace 4697

include powders fortified with various nutrients.

Most common in the market are milk powders en-

riched with calcium, iron, and folate.

0015 Milk powders have major applications as ingredi-

ents in manufactured dairy and processed food prod-

ucts. A significant amount of milk powder is used

in the manufacture of traditional recombined dairy

products such as evaporated milk, sweetened con-

densed milk, and UHT milk in countries which do not

have an adequate supply of fresh milk. Milk powders

are also used as ingredients in a range of food prod-

ucts, including icecream, cultured milks and yogurts,

chocolate, confectionery, bakery products, soups, and

sauces. Buttermilk powders are used as replacers for

skim-milk powder in applications where enhanced

dairy flavors are desired. Table 4 gives the proportion

of skim-milk powders used in various applications.

Their ability to bind water, thicken and gel, and their

emulsifying and foaming properties make milk

powders valuable food ingredients. These properties

of milk powders can be modulated by the amount of

heat treatment received by the powder during manu-

facture. The characteristics of milk powders that

make them useful in food applications are discussed

in more detail elsewhere. (See Powdered Milk: Char-

acteristics of Milk Powders.)

Dried Casein Products

0016 Caseins are the principal milk proteins, accounting

for *80% of the proteins in milk. They can be separ-

ated or precipitated from milk. Among the major

products in this class of dairy products are acid and

rennet casein, caseinates, and coprecipitates.

Production of Casein Products

0017 Acid casein is made by direct acidification of skim

milk to pH 4.6 by mineral or organic acids. Rennet

casein is made by adding rennet to skim milk. The

casein is separated, washed, and dried. Acid casein is

insoluble in water. This limits the applications of acid

casein in some applications. To obtain a casein prod-

uct that is soluble, the acid casein is neutralized with

an alkali and spray-dried to obtain caseinates. Vari-

ous types of alkali have been used. Sodium, potas-

sium, and calcium caseinates are the most common

types of caseinates on the market. Coprecipitates are

total milk protein powders; they contain both casein

and whey proteins. The proteins are precipitated

from skim milk under controlled conditions of heat,

acid, and calcium concentration. The composition of

casein products is given in Table 5.

Applications of Casein Products

0018Casein products have good emulsifying, whipping,

and water-binding properties which make them

suitable in applications such as desserts, confection-

ery, bakery products, salad dressings, processed

meats, soups, and sauces. They have applications in

dairy-based products such as coffee whiteners, yogurt,

icecream, and processed cheese and imitation cheese

products. As they are high-protein products, they are

also used as supplements in dietetic foods. (See Casein

and Caseinates: Uses in the Food Industry.)

Dried Whey and Whey Protein

Concentrates

0019Whey, the serum remaining after the manufacture of

cheese or casein, can be converted into powder. Sweet

whey (pH *6.3) is obtained during rennet-coagu-

lated cheese manufacture whereas acid whey (pH

< 5.1) is produced during cottage cheese or casein

manufacture. Acid whey has a higher mineral content

than sweet whey.

Production of Whey-Based Powders

0020Whey is preheated gently, evaporated, and dried for

production of whey powders. To facilitate drying,

the lactose in the whey concentrate is precrystallized

for the production of nonhygroscopic whey powders.

For the production of reduced-lactose or reduced-

mineral whey powders, a portion of these compon-

ents can be selectively removed from the whey. Whey

can also be concentrated by membrane separation

(ultrafiltration, with or without diafiltration). These

tbl0004 Table 4 World use of skim-milk powder in products

Product % Used

Condensed milk 30%

Ultrahigh-temperature (UHT) fluid 26%

Icecream 18%

Cultured products and yogurts 9%

Bakery 5%

Cheese 4%

Other products 3%

Based on figures from Dairy Foods Jan 1999, 100(1): 15.

tbl0005Table 5 Typical compositions of acid casein, caseinates, and

coprecipitate

Constituent Acid

casein

Sodium

caseinate

Calcium

caseinate

Coprecipitate

Moisture (%) 9.0 3.5 3.5 4.0

Fat (%) 1.0 1.0 1.0 1.0

Protein (N 6.38: %) 88.0 91.4 90.9 89.0

Lactose (%) 0.1 0.1 0.1 1.5

Ash (%) 2.2 4.0 4.5 4.5

Adapted from Chandan R (1997) Dairy-Based Ingredients. St Paul,

Minnesota: Eagan Press.

4698 POWDERED MILK/Milk Powders in the Marketplace

processes separate the proteins from the water,

lactose, and minerals. The concentrated protein

solutions are then spray-dried to obtain dried whey

protein concentrates with a range of protein contents,

typically between 34 and 80% protein. Table 6 gives

the typical compositions of dried whey and whey

protein concentrates. Whey protein concentrates

with a lower protein content (25% protein) and

whey protein isolates (> 90% protein) can also be

produced and are on the market.

Applications of Whey-Based Powders

0021 Dried whey, reduced-lactose and reduced-minerals

whey and whey protein concentrates are used as

ingredients in many food applications, including

confectionery, bakery products, snack foods, yogurts,

dips, desserts, meat products, pasta products, ice-

cream, soups, sauces, beverages, and processed cheese

products. Whey protein concentrates have been

also used as economic egg-white replacers in food

formulations. With increasing protein content, the

whey protein concentrates provide greater nutritional

value as well as improved functional properties such

as emulsification, foaming, water binding, viscosity

building, and gelling to foods. Whey protein isolates

are widely used as nutritional supplements in sports

drinks and health foods such as nutritional bars

and protein supplements. (See Whey and Whey

Powders: Production and Uses; Protein Concentrates

and Fractions.)

Other Milk Powder Products

0022 Nowadays, a range of other types of milk powders

may be formulated to achieve a desired fat, protein,

lactose, or mineral content, as well as to obtain target

functional attributes in the powder. These include

a range of cream powders, high ‘free-fat’ milk

powders for the chocolate industry, high-heat ‘heat-

stable’ milk powders for evaporated milk, milk pro-

tein concentrate powders, skim milk/whey powder

blends, lactose-hydrolyzed powders, yogurt powders,

and a variety of customized formulations for use in

target food applications. These tailor-made ingredi-

ents are finding their way into the marketplace, as

food manufacturers increasingly demand ingredients

with enhanced performance in their applications.

0023The major steps in the manufacture of skim milk/

whey powder blends and specialized milk powders

generally include the same essential unit processes of

heating, concentration, and drying that are used in

conventional milk powder manufacture, except that

sometimes additional processing steps are required

during the preparation of the milk or milk concen-

trate prior to drying.

Cream and High-Fat Powders

0024Cream and high-fat powders, containing 40–75% fat,

may be produced by spray drying of cream or milk

with an increased fat content. A typical cream

powder obtained from drying of cream contains

*70% fat. Cream powders were developed more

than 40 years ago. The early powders were difficult

to dry and handle because of their high fat content.

Improvements in formulation science and drying

technology have enabled cream powders with super-

ior properties to be made. These powders are becom-

ing more prevalent in the marketplace and can be

used as an alternative to fresh cream or in formulae

where milk fat is required. Some of their applications

include chocolate, confectionery, icecream, desserts,

soups, and sauces.

High Free-Fat Milk Powders

0025High ‘free-fat’ powders for use in chocolate manufac-

ture have traditionally been produced by roller-

drying. In roller-dried powder, greater than 90%

of the fat in the powder is readily extractable. In

addition, roller-dried powders are flaky and do not

contain much air. These properties of roller-dried

powders make them more suitable for chocolate

manufacture than conventional spray-dried powders

that have a high level of entrapped air and a low free-

fat content. The use of high free-fat powders in

chocolate reduces the requirement for cocoa butter

in chocolate making. As roller-drying is more expen-

sive than spray drying, there have been attempts to

increase the level of free-fat in milk powders intended

as ingredients for chocolate. Nowadays, some high

free-fat powders are produced by spray drying and

have improved performance compared to conven-

tional milk powders in chocolate manufacture. (See

Fats: Uses in the Food Industry.)

High-Heat Heat-Stable Milk Powders

0026High-heat heat-stable milk powders have been pro-

cessed to insure that they are suitable for use in the

manufacture of recombined evaporated milk. For

tbl0006 Table 6 Typical composition of whey-based powders

Constituent Sweet

whey powder

Acid

whey powder

Dried whey

protein

concentrates

Moisture (%) 3.5–5.0 3.5–5.0 3.0–4.0

Fat (%) 1.0–1.5 0.5–1.5 1–10

Protein (N 6.38: %) 11.0–14.5 11.0–13.5 34–80

Lactose (%) 63.0–75.0 61.0–70.0 10–55

Ash (%) 9.8–12.3 9.8–12.3 4–8

Adapted from Chandan R (1997) Dairy-Based Ingredients. St Paul,

Minnesota: Eagan Press.

POWDERED MILK/Milk Powders in the Marketplace 4699

the manufacture of this product, reconstituted milk

powder is recombined with fat to produce a concen-

trate containing typically 26% total solids (18%

skim-milk solids and 8% fat) and the concentrate is

sterilized. A heat-stable milk powder is required in

these applications, as the milk concentrate that is

prepared from the powder has to withstand in-can

sterilization (120



C for 12 min) without coagulation

or excessive thickening.

Milk Protein Concentrate Powders

0027 In the production of milk concentrate powders, skim-

milk concentrates obtained using a membrane process

that concentrates the casein and whey proteins without

precipitation are spray-dried. A range of milk protein

concentrates with varying protein, lactose, and mineral

contents may be made. The degree of concentration

and process conditions used during membrane process-

ing dictates the composition of the final powder. These

powders are used in various applications where trad-

itional milk powders and milk protein products have

been used previously. As the protein content of these

powders is higher than that of skim-milk powder, they

have better functional properties.

Skim Milk/Whey Powder Blends

0028 Skim milk/whey powder blends are made by re-

placing a portion of the skim-milk solids by whey-

based solids. These replacers can be dry blends of

skim-milk powders and whey-based solids or, alter-

natively, skim milk and whey may be blended prior to

heat treatment, concentration, and drying. There are

currently no specifications for the composition of

these powders which contain a higher ratio of whey

protein to casein than conventional milk powders.

Blends are formulated to obtain the desired compos-

ition and functionality in the target applications, such

as confectionery, bakery, icecream, and yogurts. Skim

milk/whey powder blends are used as economic alter-

natives to skim-milk powder in many recombined

dairy products. (See Whey and Whey Powders:

Production and Uses; Protein Concentrates and

Fractions.)

Lactose-Hydrolyzed Milk Powder

0029 Lactose-hydrolyzed milk powders are niche products

that have been developed for people who are lactose-

intolerant. For the production of lactose-hydrolyzed

milk powders, an enzyme, b-galactosidase (EC

3.2.1.23), that hydrolyzes lactose to glucose and gal-

actose is added to the milk and allowed to act until

the desired degree of hydrolysis is obtained; the

enzyme is then inactivated by heat treatment prior

to further processing. These powders may be used as

alternatives to milk powders.

Yogurt Powder

0030A small amount of yogurt powder is available in the

market. Milk is fermented prior to spraying to yield

powder with a yogurt flavor. The powder has appli-

cations in confectionary as fillings and pastes, bakery

products, and in a range of soups, sauces, and dips.

Milk Protein Hydrolysates

0031A number of milk protein, casein, and whey protein

hydrolysates have been developed. These products

are aimed at the nutritional supplement and sports

nutrition markets. The hydrolyzed products are

soluble and are quickly absorbed by the body.

Milk Powder Production Worldwide

0032Milk powder is the third largest category of dairy

products, after cheese and fresh dairy and liquid milk

products. World production of milk has continued to

grow at the rate of about 1% a year through both

increased cow numbers and better yields from herds.

Stagnant sales of drinking milk in high-milk-produc-

tion countries have meant that there has been a steady

increase in manufacturing milk available for drying

and milk powder production, particularly in Argen-

tina, New Zealand, and Australia (Tables 7 and 8),

with the last two countries exporting the majority of

their production (Tables 9 and 10).

0033China and India have also shown steady increases

in their production of full-cream milk powder, which

has been used mostly for home consumption to

shift production of milk products internally to cover

areas and times of low production (Table 8). The

tbl0007Table 7 Skim-milk powder production (

000 tonnes)

Country 1995 1996 1997 1998 1999

Argentina 36.6 36.6 40.0 38.0 81.0

Australia 229.6 237.9 230.8 272.8 275.4

Belarus 31.4 30.7

Brazil 60.0 50.0 55.0 58.0

Canada 71.1 64.6 66.2 69.8 77.4

Czech Republic 65.6 51.6 33.6 31.9 34.6

Estonia 19.2 21.6 16.1 14.1

European Union

(15 countries)

1187.7 1186.0 1130.4 1074.0 1113.9

Japan 189.4 200.3 199.9 201.8 191.1

Lithuania 30.1 26.4 17.4

New Zealand 127.1 172.0 177.0 160.0 227.0

Poland 118.0 120.6 119.9 131.3 110.9

Russia 107.0 79.0 83.0

South Africa 18.7 9.0 10.5 22.1 9.3

Switzerland 28.9 26.9 27.2 29.1 29.6

Ukraine 34.6 28.0 19.8 22.4 19.2

USA 564.0 477.6 548.0 515.0 625.1

Adapted from The World Dairy Situation 2000 (2000) Bulletin 355, Table 14.

International Dairy Federation.

4700 POWDERED MILK/Milk Powders in the Marketplace

USA and the European Union continue to be major

producers and exporters of all forms of milk powder

(Tables 7–10).

0034 During the 1990s, skim-milk production increased

an average of only 1.7% compared with the average

annual increase in full-cream milk powder of 7%.

Over this period, conventional skim-milk powder

lost market share as a livestock feed component. It

also faced increased competition in the food ingredi-

ent market from full-cream milk powders and special-

ist dairy powders, such as whey powders and other

milk components, for the production of both dairy

and general food products. The demand for dairy

products made from preserved milks and manufac-

tured food items with dairy ingredients such as

bakery goods, confectionery, processed meats, and

beverages continued to grow in all markets.

0035Factors which have influenced the increased con-

sumption and demand for a greater variety of dairy

products and manufactured foods containing dairy

products throughout the period include:

0036an increased middle class with more discretionary

income

0037changes in consumption patterns as diet becomes

increasingly international in style

0038increased identification of dairy products as a

healthy food

0039newly identified applications for dairy ingredients

and components

0040growth in food service establishments worldwide

0041growth in food-manufacturing capacity in key

markets

0042extended availability of dairy technology as an

increasingly concentrated dairy industry moves

into new markets and expands its processing cap-

ability in developing countries

0043better distribution systems to support and extend

the availability of dairy products in developing

countries

Whilst milk production has outstripped demand for

dairy products in high-production countries, the

demand for dairy products and components, includ-

ing powders, has continued to grow in developing

areas. Key markets for imported milk powders in the

1990s included South-East Asia, Africa, and Latin

America. Algeria, Japan, the Philippines, and Mexico

were the world’s largest importers of skim-milk

powders throughout the latter parts of the 1990s,

with Algeria, Brazil, Venezuela, and Saudi Arabia

taking large amounts of the world’s production of

full-cream milk powders (Tables 11 and 12).

0044Economic factors, such as the financial crises

suffered by Brazil, some South-East Asian and East-

ern bloc countries and changing agreements on world

trade policies, affected trade in milk powders through

the 1990s, with downturns occurring in affected

economies. Import trends (Tables 10 and 11) show

the influences of these factors on changes in the sales

of milk powders throughout this period. Other factors

which affect the demand for milk powders and prices

obtained on international markets include:

tbl0008 Table 8 Full-cream and semi-skimmed milk powder production

(

000 tonnes)

Country 1995 1996 1997 1998 1999

Argentina 146.5 162.3 166.0 207.0 269.0

Australia 113.0 133.7 126.5 144.8 172.0

China 352.0 358.0 391.0 422.0 552.0

Czech Republic 29.6 29.2 22.5 25.9 21.9

European Union

(15 countries)

942.6 877.5 898.8 927.4 896.0

India 82.0 103.8 115.2 120.0 130.0

Japan 30.6 23.7 18.9 18.7 17.8

Lithuania 15.4 13.4 13.2 16.4 16.0

New Zealand 342.0 337.2 396.0 375.0 373.0

Poland 40.0 35.2 39.8 39.3 32.2

Russia 124.0 107.0 89.0 79.0 83.0

South Africa 11.6 9.7 13.0 10.8 11.3

Switzerland 10.3 9.9 9.3 8.0 8.0

Ukraine 11.5 6.3 4.8 3.2 3.1

USA 74.8 58.8 55.4 64.6 53.5

Adapted from The World Dairy Situation 2000 (2000) Bulletin 355, Table 13.

International Dairy Federation.

tbl0009 Table 9 World trade in skim-milk powder – exports (

000

tonnes)

Country 1995 1996 1997 1998 1999

World 958 1074 975 1130 1200

Argentina 22 17 15 29

Australia 168 205 199 238 240

Canada 45 30 31 41

European Union 227 282 175 272 370

New Zealand 127 183 166 174 157

Poland 77 112 101 83

Other countries 270 152 177 114

Adapted from The World Dairy Situation 2000 (2000) Bulletin 355, Table 15.

International Dairy Federation.

tbl0010 Table 10 World trade in full-cream milk powder – exports (

000

tonnes)

Country 1995 1996 1997 1998 1999

World 1154 1302 1392 1420 1430

Argentina 55 62 97 149

Australia 93 109 110 139

European Union 540 571 588 571 580

New Zealand 278 341 359 362 370

USA 16 27 20 17 20

Other countries 227 254 315 331

Adapted from The World Dairy Situation 2000 (2000) Bulletin 355, Table 15.

International Dairy Federation.

POWDERED MILK/Milk Powders in the Marketplace 4701

.0045 protectionist policies, such as subsidies and market

price supports

0046 quotas and stockpiles in storage in producing coun-

tries

0047 domestic consumption by producing countries

0048 policies on self-sufficiency and import reduction by

importing countries

0049 competitiveness of major exporting countries

0050 currency fluctuations

Future of Milk Powders in the Marketplace

0051 Consumers and food product manufacturers recog-

nize that milk powders have many desirable attri-

butes. The nutritional, physical, and physiological

functionality of milk powders, coupled with the ease

with which they can be handled and stored, make

them sought-after ingredients in the market place.

This is evidenced by the growing demand for milk

and dairy-based powders. As users of ingredients are

placing more stringent requirements for consistent

performance and enhanced functional performance

in food, the trend towards tailored milk powder

ingredients that are matched to specific food

application sectors is expected to grow.

See also: Agglomeration; Casein and Caseinates: Uses

in the Food Industry; Drying: Spray Drying; Evaporation:

Basic Principles; Fats: Uses in the Food Industry;

Homogenization; Powdered Milk: Characteristics of

Milk Powders; Whey and Whey Powders: Production

and Uses; Protein Concentrates and Fractions

Further Reading

American Dairy Products Institute (1990) Standards for

Grades of Dry Milks Including Methods of Analysis.

Bulletin 916. Chicago: ADPI.

Anonymous (1996) Milk materials multiply. Ingredients

and Analysis International 18: 30–35.

Ashton D, Brittle S and Shaw I (2000) Dairy outlook to

2004–05.Australian Commodities 7: 66–72.

Chandan R (1997) Dairy-Based Ingredients. St Paul: Eagan

Press.

Early R (1998) Milk concentrates and milk powders. In:

Early R (ed.) The Technology of Dairy Products, 2nd

edn, pp. 228–300. London: Blackie Academic and Pro-

fessional.

Hall CW and Hendrick TI (1971) Drying of Milk and Milk

Products, pp. 1–16. Westport: AVI.

Hardcastle S, Gleeson T and Topp V (1999) Dairy outlook

to 2003–04. Australian Commodities 6: 69–78.

Hunziker OT (1935) Condensed Milk and Milk Powder:

Prepared for Factory, School and Laboratory, 5th edn,

pp. 457–527. La Grange, IL: Hunziker.

International Dairy Federation (1990) Recombination of

Milk and Milk Products, special issue no. 9001. Brussels:

International Dairy Federation.

International Dairy Federation (1999) Third International

Symposium on Recombined Milk and Milk Products.

Special issue no. 9902. Brussels: International Dairy

Federation.

International Dairy Federation (2000) The World Dairy

Situation 2000. Bulletin no. 355. Brussels: International

Dairy Federation.

Knipschildt ME and Andersen GG (1994) Drying of milk

and milk products. In: Robinson KR (ed.) Modern Dairy

Technology, vol. 1, 2nd edn, pp. 159–254. London:

Chapman & Hall.

Masters K (1985) Spray Drying Handbook, 4th edn.Lon-

don: Godwin.

Pisecky J (1986) Standards, specifications, and test methods

for dry milk products. In: MacCarthy D (ed.) Concen-

tration and Drying of Foods: Proceedings of the Kellogg

Foundation 2nd International Food Research Sympo-

sium (Cork: 1985), pp. 203–220. London: Elsevier

Applied Science.

Rasmussen KW (2000) World market for milk powder in

for a boom. Scandinavian Dairy Industry 2/00: 46–47.

Singh H and Newstead DF (1992) Aspects of proteins in

milk powder manufacture. In: Fox PF (ed.) Advanced

Dairy Chemistry – 1: Proteins, pp. 735–765. London:

Elsevier Applied Science.

Wong NP, Jenness R, Keeney M and Marth EH (1988)

Fundamentals of Dairy Chemistry, 3rd edn. New York:

Van Nostrand Reinhold.

tbl0011 Table 11 World trade in skim-milk powder – imports (

000

tonnes)

Country 1995 1996 1997 1998 1999

World 1190 958 1074 975 1130

Algeria 108 53 40 43

Brazil 54 34 29 24

European Union 43 61 74 65 75

Japan 87 75 73 57 57

Mexico 107 127 130 149

Philippines 104 79 98 90

Russia 31 109

Adapted from The World Dairy Situation 2000 (2000) Bulletin 355, Table 16.

International Dairy Federation.

tbl0012 Table 12 World trade in full-cream milk powder – imports (

000

tonnes)

Country 1995 1996 1997 1998 1999

World 1165 1154 1300 1390 1420

Algeria 75 78 91 120

Brazil 217 116 100 100

Malaysia 60 62 65 50

Mexico 30 30 30 20

Philippines 36 42 52 47

Russia 35 35

Saudi Arabia 63 69 63 64

Singapore 30 26 26 20

Venezuela 66 66 56 80

Adapted from The World Dairy Situation 2000 (2000) Bulletin 355, Table 16.

International Dairy Federation.

4702 POWDERED MILK/Milk Powders in the Marketplace

Characteristics of Milk

Powders

M A Augustin, P T Clarke and H Craven, Food

Science Australia, Weribee, Victoria, Australia

Background

0001 Milk powders are used by consumers as a substitute

for fresh milk and as ingredients for the manufacture

of a range of processed food products. In order to be

acceptable to consumers and users of ingredients, it is

essential that milk powders are of a good quality.

Milk powders are manufactured to meet certain spe-

cifications and standards for composition. These have

been developed for milk powders by authorities such

as the American Dairy Products Institute, the Inter-

national Dairy Federation, the Food and Agricultural

Organization of the United Nations and national

food authorities in individual countries. In addition,

a range of other technical specifications have been

developed for the characterization of milk powders

to ensure that they have the required functional

performance in specific target applications. Milk

powders may be similar in composition but have

different functional properties.

0002 There are many types of milk powders in the

market place. This article focuses on the characteris-

tics of skim and full-cream milk powders, which are

the major types of milk powders produced. The

microbiological quality, physical and chemical attri-

butes of these milk powders, and their functional

properties are discussed. Aspects of deteriorative

changes that may occur in milk powders during

transport and distribution that have an impact on

the sensory properties of powders and their perform-

ance as food ingredients are included. The produc-

tion, composition, and applications of various

types of milk powders have been discussed else-

where. (See Powdered Milk: Milk Powders in the

Marketplace.)

Microbiological Aspects

Standards for Quality and Safety

0003Milk powder is a microbiologically stable product.

It has a water activity of 0.3–0.4, which is too low

to support the growth of microorganisms. However,

after milk powder has been reconstituted, it is suscep-

tible to microbial growth and spoilage in a similar

manner to pasteurized milk. Provided milk powder is

protected from moisture contamination before use,

the numbers of microorganisms present generally de-

crease during storage, although the numbers of spores

may remain constant.

0004Although milk powder does not support the growth

of microorganisms, the microbiological content is an

important consideration in the subsequent use of the

powder. For this reason, government bodies and cus-

tomer groups have developed microbiological limits

or specifications that apply to certain groups of

microorganisms that may be present in milk powder.

These specifications may relate to expectations of raw

milk quality, hygiene during manufacture, microbial

safety, or compatibility with the intended use of the

milk powder.

0005Common end-product standards relate to the total

number of bacteria (mesophilic aerobes), coliforms,

Salmonella, and Staphylococcus aureus. Criteria may

also be applied for Bacillus cereus, Listeria, thermo-

philes, Enterobacteriaceae and spore-forming bac-

teria. The standards developed by the International

Dairy Federation, for example, are shown in Table 1.

Many countries have either adopted these standards

or developed their own local specifications based on

the principles of the International Commission on

Microbiological Specifications for Foods (ICMSF).

0006The microbiological count of milk powder is

influenced by both the numbers and types of micro-

organisms in the raw milk and the processing condi-

tions under which the milk powder is produced.

In powders subjected to a high heat treatment,

the microorganisms present will be predominantly

spore-formers, belonging to the genus Bacillus.

When heat treatment is less severe, vegetative cells

tbl0001 Table 1 Microbiological specifications for milk powder, as recommended by the International Dairy Federation

Criteria

Total count (per gram) Salmonella (per 25 g) Coliforms (pergram) Staphylococcus aureus (per gram)

m 50 000 0 10 10

M 200 000 na 100 100

n 515 5 5

c 20 1 1

For a production batch, n ¼number of samples that must be tested, c ¼number of samples that may exceed the microbiological limit specified as m, and

M is the maximum allowable microbiological limit specified for any of the samples examined.

na ¼not applicable.

POWDERED MILK/Characteristics of Milk Powders 4703

of thermoduric bacteria will be present, with their

proportion to spore-formers decreasing with the in-

tensity of the heat treatment applied. Vegetative cells

of pathogenic bacteria and Gram-negative milk spoil-

age bacteria are destroyed during the heat treatment.

0007 Coliforms, Salmonella, and other Enterobacteria-

ceae are killed when the milk is heated prior to evap-

oration; however, they may contaminate milk powder

if conditions are not sufficiently hygienic during

drying. These bacteria can enter the dryer through

the intake air from the factory environment, or the

equipment used to dry or transport the milk powder.

Cracks in dryers have been shown to be a particularly

significant source of Salmonella. Here, Salmonella are

harbored in the insulation material. Although dryers

operate at a high temperature, the concentrated milk

offers protection to the bacteria, and they will survive

heating at dryer air inlet and outlet temperatures. Sal-

monella spp. are significant pathogens, and several

notable outbreaks of illness have been attributed to

the presence of this organism in milk powder.

0008 Staphylococcus aureus is significant, as certain

strains can produce a heat-stable toxin that is not

destroyed during powder manufacture. Although

Staphylococcus aureus is common in raw milk, it

does not normally grow to produce toxin unless the

milk is stored at a high temperature prior to process-

ing. The risk of toxin production increases with tem-

perature and storage time. Although the bacteria will

be killed during the process, the toxin remains and

can be detected only through specific tests. Large

outbreaks of illness have been attributed to the pres-

ence of Staphylococcus aureus toxin in milk powder.

0009 Another bacterium of potential significance in milk

powder is Bacillus cereus. This is commonly found in

milk, and its spores may survive heat processing.

Specialty powders such as infant formula often have

specifications for this bacterium, owing to the poten-

tial risk of the growth of this organism in warmed

milk and sensitivity of the target group of consumers.

0010 Sometimes, yeasts and molds or their toxins, and

Listeria are included in powder specifications. Yeasts

and molds may be significant spoilage organisms if

powder is contaminated with moisture, and Listeria

may contaminate powder from the factory environ-

ment, especially if the environment is not kept dry.

0011 In the milk powder process, milk is subjected to

heat whilst concentrated under vacuum. Such condi-

tions are conductive to the growth of thermophilic

Bacillus species that may form biofilms in the process

lines. When this occurs, the product may be contam-

inated with thermophiles that can reach more than

per gram in long production runs. Thermophiles

may sporulate in the process, leading to the presence

of large numbers of thermophilic spores in the

powder. The spores can be extremely heat-resistant

and may not be completely destroyed when the recon-

stituted powder is used in ultrahigh-temperature

(UHT) processes. They are significant because they

may cause sterility failures or spoilage in other heated

products. If not properly cleaned from the plant be-

tween production runs, residues of thermophiles will

seed subsequent batches of milk powder.

0012Although milk powder is a microbiologically stable

product, the microbial quality of the raw milk may

influence the shelf stability of the powder. Some bac-

teria present in raw milk, particularly Pseudomonas

species, produce heat-stable spoilage enzymes, in-

cluding proteases and lipases, that remain active in

milk powder over many months. Experience has

shown that lipase can act in full-cream milk powder

to degrade milk fat to cause rancidity and other ob-

jectionable flavors. Proteases retain activity in milk

powder and degrade milk proteins to cause objection-

able flavors after the milk powder has been reconsti-

tuted. Proteases and lipases may be particularly

detrimental in recombined milk products, or if milk

powder is used to prepare UHT milk. Here, very

low levels of protease and lipase may cause

spoilage during long storage periods. (See Bacillus:

Occurrence; Detection; Food Poisoning; Biofilms;

Listeria: Properties and Occurrence; Pasteurization:

Principles; Salmonella: Properties and Occurrence;

Spoilage: Bacterial Spoilage; Fungi in Food – An

Overview; Molds in Spoilage; Yeasts in Spoilage;

Staphylococcus: Properties and Occurrence.)

Control of Microorganisms

0013The manufacture of microbiologically sound milk

powder is dependent upon processing good-quality

raw milk under hygienic conditions. To ensure the

supply of good-quality milk, farm milk should be

tested regularly for microbial quality. Many countries

now use the total count test to monitor levels of

bacteria in farm supplies. Thermoduric counts are

sometimes used also. Raw milk ideally should be

stored at less than 5



C and used within 72 h of col-

lection to minimize bacterial growth.

0014The pasteurization of milk is important and is

normally identified as a critical control point. An

example of process criteria for pasteurization would

be heating of the milk for at least 15 s at 72



Cor5s

at 80



0015Within the factory, application of good manufac-

turing practice is essential to minimize the risk of milk

powder contamination with undesirable types or

levels of microorganisms. To achieve this, consider-

ation must be given to the design of the premises and

control of staff or vehicular movement to separate

raw materials from drying areas. Manufacturing

4704 POWDERED MILK/Characteristics of Milk Powders