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

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Recently, interest in dietary fat originated from its

involvement in the etiology of cardiovascular dis-

eases, cancer, obesity, and hypertension. It is not dis-

puted importance of lipids but type and the amount of

fats to be responsible for the development of these

chronic diseases, cancer, obesity, and hypertension.

Lipids, particularly the type and amount of fats, are

now considered responsible for the development of

these chronic diseases. Nutritional recommendations

in Europe and North America stipulate a reduction of

total fat intake to 30% and saturated fat intake to less

than 10% of total energy. Over the past 30 years,

there has been a major shift from the consumption

of animal origin fats to vegetable oils. In Canada,

canola oil has become the major oil consumed and

processed. The shift to vegetable oils did not reduce

saturated fat consumption because a significant

number of these oils were used as hydrogenated fats

in margarine and shortening. Where unsaturated

fatty acids were hydrogenated, both saturated fatty

acids and trans isomers were produced to obtain fat

with proper technological properties such as a higher

melting point and crystallization structure and tex-

ture. Trans isomers have a similar effect on plasma

cholesterol level to saturated fatty acids. The compos-

ition of fatty acids in canola oil is compatible with

nutrition recommendations directed to reduce the

consumption of saturated fat and to have a ratio of

omega-6 to omega-3 within 3–5. Canola oil has a

ratio of 2 and has been found to be equally effective

as soybean, sunflower and corn oils in reducing

plasma levels of total and LDL cholesterol in normal

and hyperlipidemic subjects. Diets containing canola

oil also increased the content of long-chain polyun-

saturated fatty acid in plasma and platelet phospho-

lipids indicating the transformation of linoleic and

linolenic acids. Consumption of canola oil alters

clotting activity and thrombogenesis, and protects

against cardiac arrhythmias. All these findings and

the positive ratio of linoleic to linolenic acids in

canola oil make this oil suitable as a source of fat

for infant formulas and as part of any nutritious diet.

See also: Brassicas; Functional Foods; Soy (Soya)

Bean Oil; Triglycerides: Structures and Properties;

Vegetable Oils: Types and Properties; Oil Production and

Processing; Composition and Analysis

Further Reading

Downey RK, Kramer JKG, Sauer FD and Pygden WJ (eds)

(1983) High and Low Erucic Acid Rapeseed Oil:

Production, Usage, Chemistry, and Toxicological

Evaluation. New York: Academic Press.

Eskin NAM, McDonald BE, Przybylski R et al. (1996)

Canola oil. In: Hui Y (ed.), Edible Oil and Fat Products:

Oils and Oilseeds, Bailey’s Industrial Oil & Fats Prod-

ucts, 5th edn., vol. 2, pp. 1–95. New York: John Wiley.

McDonald BE (1999) Canola Oil: Nutritional Properties.

Bulletin. Winnipeg, Canada: Canola Council of Canada.

Przybylski R (1999) Canola Oil: Physical and Properties.

Bulletin. Winnipeg, Canada: Canola Council of Canada.

Shahidi F (1993) Rapeseed Production, Chemistry, Nutri-

tion and Processing Technology. New York: Van

Nostrand Reinhold.

Vaisey-Genser M and Eskin NAM (1987) Canola Oil:

Properties and Performance. Publication No. 60.

Winnipeg, Canada: Canola Council of Canada.

RASPBERRIES AND RELATED FRUITS

M P Pritts, Cornell University, Ithaca, NY, USA

Background

0001 Raspberries are a high-value crop owing to their

unique flavor, exacting climatic requirements, high

costs of production, and perishability. This article

describes the relationships among various raspberry

species and relatives, discusses the commercial

raspberry industry, describes the morphology, anat-

omy, and chemical composition of fruit, reviews har-

vesting and handling techniques for fresh fruit, and

presents various food uses for the raspberry.

Taxonomy and Commercial Importance

0002Raspberries are a diverse group of flowering

plants that are closely related to blackberries. Both

raspberries and blackberries belong to the genus

Rubus. Taxonomists recognize 12 subgenera within

Rubus, but only the raspberries (Idaeobatus) and

blackberries (Eubatus) have obtained commercial sig-

nificance. Species of a third group, the arctic rasp-

berries (Cylactis), are harvested from the wild, and

are popular in Scandanavia for making liqueurs, but

these are not cultivated. The fruit of raspberries de-

taches from the receptacle when picked, leaving

a white torus attached to the plant and a hollow

fruit. This characteristic distinguishes them from

4916 RASPBERRIES AND RELATED FRUITS

blackberries in which fruit abscission occurs behind

the receptacle.

0003 The genus Rubus is a member of the rose family

(Rosaceae), which also includes important fruit crops

such as apples, pears, cherries, peaches, plums, and

strawberries. Wild raspberries occur on five contin-

ents, but are most abundant in the northern hemi-

sphere. The temperature and subtropical region of

eastern Asia is recognized as the center of origin

where the most diversity exists. More than 200

species have been identified, but only a few are im-

portant commercially. These include the European

red raspberry (R. idaeus ssp. vulgatus Arrhen.), the

North American red raspberry (R. idaeus ssp. strigo-

sus Michx.), and the black raspberry (R. occidentalis

L.) of the eastern USA. Hybrids between the red and

black raspberry are commonly called purple rasp-

berries because of the fruit and cane color, and these

were once given the specific rank of R. neglectus Peck.

However, most taxonomists do not recognize hybrids

as distinct species. Interspecific hybrids with

blackberries have also been made; some of these are

commercially important, such as Tayberry, Logan-

berry, Boysenberry, and Youngberry.

0004 Several other species within the genus Rubus have

edible fruit, or have been used by plant breeders to

improve cold hardiness and resistance to diseases and

insects in raspberries. Examples are R. glaucus

Benth., a South American tetraploid black raspberry

that is probably a raspberry blackberry hybrid,

R. leucodermis Torr. and Gr. (the western North

American black raspberry), and R. spectabilis Pursh.

(salmonberry); the Asiatic species R. coreanus Miq.,

R. phoenicolasius Maxim. (Japanese wineberry),

R. parvifolius Nutt. (trailing raspberry), R. ellipticus

Sm. (golden evergreen), R. illecebrosus Focke (straw-

berry raspberry), R. kuntzeanus Hemsl. (Chinese

raspberry), and R. nivens Thumb.; the Hawaiian

species R. macraei Gray and R. hawaiiensis Gray

(Akala berries); and the arctic raspberries of Europe

(R. arcticus L.) and North America (R. stellatus Sm.).

Commercial Industry

0005 Raspberries were first introduced into cultivation in

Europe nearly 450 years ago. By the early nineteenth

century, more than 20 cultivars of red raspberry were

grown in both England and the USA. English cultivars

were then exported to the USA, where crosses

between them and North American seedlings gave

improved cultivars. Red raspberries are the most

widely grown, whereas black raspberries are popular

only in certain regions of the eastern USA. The pro-

geny of black and red raspberries have purple fruits

and canes; these types are popular in eastern North

America. Yellow-fruited R. idaeus, caused by a reces-

sive mutation, is also grown on a limited scale for

specialty markets. R. occidentalis genotypes with

yellow fruit are not grown commercially.

0006The three major raspberry production regions are

(1) Russia, (2) Europe (mostly in Poland, Hungary,

Serbia, Germany, and the UK), and (3) the Pacific

Coast of North America and Canada (British Colum-

bia, Washington, and Oregon). Much of the fruit

produced in these regions is harvested mechanically

and processed. In other production regions, such as

eastern North America, nearly all the production is

for the fresh market. Many other countries, such as

Chile, New Zealand, and Australia, have a significant

production as they supply the fresh market during

winter in the northern hemisphere. World production

is estimated at more than 400 000 tonnes.

0007Patterns of production in North America shifted

dramatically in the early 1900s. In 1920, New York

State growers (East Coast) harvested more than

4000 ha. The systemic ‘mosaic virus disease’ infected

most of the planting stock, and the processing

raspberry industry collapsed in this region. With the

development of tissue culture propagation tech-

niques, virus-indexing of nursery stock, and breeding

for resistance to the virus vector, the raspberry pro-

cessing industry redeveloped on the West Coast. In

Britain during World War II, little attention was paid

to maintaining the health of raspberry stock. It was

not until the 1970s that the raspberry industry

reorganized with certification programs and heat-

treatment therapy for the elimination of viruses. Cur-

rently, there is interest in both Europe and North

America in greenhouse raspberry production to

supply local markets during winter and spring.

Varieties

0008Two types of bearing habits are found in commercial

red raspberries. The first type is called a ‘summer-

bearing’ habit. Canes originate from either crown

buds or adventitious root buds in early spring.

Canes elongate during the growing season, forming

fruit buds in the axils of leaves in the autumn when

temperatures decrease and day lengths shorten. The

plants become dormant for winter, and then the buds

on the cane grow the following spring once the

chilling requirement has been fulfilled. The chilling

requirement varies considerably among summer-

bearing varieties, ranging from a few hundred hours

to more than 1800 h. The lateral axillary buds on

dormant canes contain both leaf and flower primor-

dia. At the onset of warm weather, buds break, and

flowering occurs about 6–10 weeks later. Fruiting

occurs in early to late summer, depending on variety,

RASPBERRIES AND RELATED FRUITS 4917

and then the entire cane senesces. While these second

year canes (floricanes) are flowering, first-year canes

(primocanes) are growing from the crown or roots.

These primocanes will fruit the following year. More

than 40 summer-bearing red raspberries are grown

commercially, and these change with the release of

new, improved varieties. Among the major varieties

originating in North America are ‘Boyne,’‘Canby,’

‘Killarney,’‘Meeker,’‘Reveille,’‘Taylor,’‘Titan,’

‘Tulameen,’ and ‘Willamette.’ The Glen and Malling

series are important varieties from the UK. The Scot-

tish Crops Research Institute is the leading institution

in the world for raspberry variety development.

0009 The second type of growth habit is called ‘fallbear-

ing.’ In some varieties, fruiting laterals will develop

from the top of first year primocanes after they reach

a certain height, without any chilling. If the growing

season is sufficiently long, fruit can be harvested from

the upper portion of these canes through autumn. The

lower portion of the cane will fruit the following

summer, if it is allowed to remain in the field. The

major variety worldwide is ‘Heritage;’ other import-

ant varieties are ‘Amity,’‘Autumn Bliss,’‘Polana,’

and ‘Autumn Britten.’

0010 At least 13 varieties of black raspberries are grown

in North America. The most successful are ‘Allen,’

‘Bristol,’‘Haut,’ and ‘Jewel.’‘Royalty’ is the most

popular purple raspberry. Several yellow or golden

raspberry varieties are grown on a small scale for

specialty markets.

Morphology and Anatomy of Fruit

0011 Each raspberry flower contains 60–160 ovaries. Each

ovary contains two ovules, but one usually aborts

after differentiation. About 1 month after pollination,

the ovaries ripen simultaneously to form the fruit.

0012 Fruits ripen in three phases. Pollination is followed

by a period of rapid cell division. In the second phase,

cell division slows while the embryo develops, and the

seed coat hardens. Finally, very rapid growth occurs

as a result of cell enlargement. Each phase lasts 10–12

days. Considerably variation in fruit size exists, with

a range of 1–5 g. Under certain conditions, fruit can

exceed 10 g.

0013 As with most climacteric fruit, ethylene production

in the raspberry begins in the receptacle when the

fruit starts to color and peaks when fully ripe. Respir-

ation, however, decreases as ripening proceeds.

Growth stresses help to fracture the middle lamella

and walls of cortical cells where the fruit attaches to

the receptacle. Cell-wall breakdown and disintegra-

tion are complete when the fruit is fully ripe. The

detachment force is small, usually 25 g, when fruits

are ripe. A 12-fold difference in detachment force can

exist between underripe and overripe fruit. This dif-

ferential is exploited by mechanical harvesters.

0014The raspberry fruit is not a true berry, but rather an

aggregate of many individual drupelets. Each drupe-

let is anatomically analogous to a cherry with a hard

endocarpic seed (pyrene) surrounded by a fleshy

mesocarp and an outer exocarp. The fleshy mesocarp

is composed of thin-walled, turgid parenchymatous

cells. Just below the exocarp is a thin layer of oval,

collenchymatous cells. Large seeds are undesirable,

but there is a relationship between seed size and

drupelet size. Small seeds tend to be associated with

small drupelets. An average seed has a mass of about

1 mg, and comprises 4–5% of the total mass of a

berry. A 100-g sample of raspberries may contain

more than 4000 seeds.

0015The cohesion of individual drupelets results from

the entanglement of unicellular, epidermal hairs that

are most abundant on the sides and base of the drupe-

let. In some black raspberry varieties, fusion of the

cuticle or wax also contributes to drupelet cohesion.

Drupelets cannot normally be separated without

tearing the exocarp. Considerable variation in fruit

firmness and drupelet cohesion exists among com-

mercial varieties. If the percentage of developed

drupelets is low, cohesion will be poor. Firmness is

related to cell diameter and tissue compactness.

Chemical and Nutritional Composition

Fruit Composition

0016The main constituent of the raspberry fruit is water

(approximately 87%). Of the remaining solids, 9%

are soluble and the rest insoluble. Pectins comprise

0.1–1.0% of the soluble fraction, but this amount

decreases with ripening owing to hydrolysis.

0017The main sugars are glucose, fructose, and a

smaller amount of sucrose. These comprise the

major soluble component of the juice. A typical

ripe raspberry fruit contains 5–6% sugar. Citric acid

is the second largest component of the soluble frac-

tion; raspberries contain very little malic acid, but at

least 10 other acids in trace amounts. The amount of

acid in the fruit increases early in development, then

decreases as the fruit begins to ripen. The balance

between the sugars and acids is important for con-

sumer acceptance. A fruit with a low sugar:acid ratio

will taste tart; one with a high ratio will taste bland. A

typical pH of a ripe raspberry fruit is 3.0–3.5; the

ratio between sugars and acids (w/w) is approxi-

mately 1.0. Fruits grown under warm, dry summers

(daytime temperatures near 25



C) are sweeter, less

acid, more aromatic, and more highly colored. Hot

weather (temperatures greater than 30



C) reduce the

4918 RASPBERRIES AND RELATED FRUITS

aroma of the fruit, and wet weather reduces the sugar

content.

0018 A large number of volatile compounds are found in

raspberry fruit, but most are present at less than

10 p.p.m. and are below the threshold of detection

by the human nose. Compounds include alcohols,

acids, esters, carbonyls, ketones, and other hydrocar-

bons (naphthalene and related compounds). A par-

ticular ketone, 1-(p-hydroxyphenyl)-3-butanone has

an odor very characteristic of raspberry.

0019 Considerable changes occur in phenolic compounds

as fruits mature. Raspberry juice from ripe fruit con-

tains 0.10–0.14% polyphenols, mainly as catechin

and chlorogenic, ferulic, and neochlorogenic acids.

0020 Raspberry fruits contain small amounts of vita-

mins; only vitamin C is present at a significant level.

Amino acids include alanine, serine, asparagine, glu-

tamic acid, glutamine, (gamma)aminobutyric acid,

valine, leucine, and aspartic acid. The high levels of

antioxidants and ellagic acid in raspberries have been

highlighted in the popular press as public interest in

cancer prevention increases. Table 1 presents data on

the vitamin and nutrient content of red raspberries.

Fruit Color

0021 The color of raspberry fruit is imparted by anthocya-

nins. The anthocyanin molecule in raspberry consists

of cyanidin and pelargonidin with glucose attached at

the 3 position. Additional glucose, rhamnose, or

xylose sugars may be present in various combinations

to give diglycosides or triglycosides. Fruits with a

preponderance of pelargonidin glycosides have an

orange–red color, as opposed to a deep red color

with cyanidin glycosides. The type and concentration

of anthocyanins in the fruit are controlled by a few

major genes. Fruits with a yellow color are produced

when one or more of these genes suppress anthocya-

nin production. Molecules that are complexed with

the anthocyanin also affect color development, and

the pH of the fruit has a small effect. During storage,

raspberry fruits increase in anthocyanin, darken, and

become more blue, owing in part to an increase in

cytoplasmic pH.

Handling and Storage of Fresh Produce

Harvest Considerations

0022 Raspberries have one of the highest respiration rates

of any fruit. This, coupled with their thin skin and

sugary interior, makes them among the most perish-

able of all fruits. With any given variety, fruit on

a bush will ripen over a period of several weeks.

Harvesting the same planting frequently (once every

2 days) is critical. Fruit harvested before it is fully ripe

will have a much longer shelf-life than fully ripe or

overripe fruit but will be lower in sugar and antho-

cyanins. The optimum stage of maturity for the

raspberry occurs when the berry first becomes com-

pletely red but before any darker hues develop.

0023Fruit quality for fresh market raspberries usually

declines as the season progresses. Marketing channels

must be open before the first berries ripen, as these are

likely to be of the highest quality and largest size for

the season. Berries should not be touched before har-

vest, and only undamaged berries with a good

appearance should be placed in the pack. The magni-

tude of injury caused by human pickers can be so

great as to mask any other causes of deterioration.

Overripe or damaged berries should be harvested and

discarded, because they are susceptible to molds.

0024Botrytis is the most common pathogen of raspberry

fruit. Once the mold growing on overripe berries

sporulates, large amounts of inoculum will be present

to infect other ripening fruit. Overripe berries also

attract ants, wasps, and other pests.

tbl0001Table 1 Reported values or ranges of nutrient content in 100 g

of fresh raspberries

Nutrient Amount

Water (g) 84–87

Food energy (kcal) 31–49

Protein (g) 0.42–1.40

Fat (g) 0.20–0.55

Carbohydrate (g) 5.8–11.6

Fiber (g) 3.0–7.4

Ash (g) 0.40–0.51

Minerals (mg)

Calcium 22–50

Iron 0.57–1.20

Magnesium 18–30

Phosphorus 12–50

Potassium 130–221

Sodium 0–2.5

Zinc 0.46

Copper 0.07–0.21

Manganese 1.01

Sulfur 17.3

Chlorine 22.3–22.8

Boron 71–125

Vitamins (mg)

Carotene 0.05–0.08

Thiamin 0.01–0.03

Riboflavin 0.03–0.10

Pantothenic acid 0.24–0.30

Nicotinamide 0.20–1.00

Vitamin B

0.06–0.90

Vitamin C 13–38

Tocopherols 0.3–4.5

Data from: Jennings DL (1988) Raspberries and Blackberries ^ Their

Breeding, Diseases and Growth. New York: Academic Press, Green A (1971)

Soft fruits. In: Hulme AC (ed.) The Biochemistry of Fruits and their Products,

vol. 2, pp. 375–410. New York: Academic Press and Souci et al. (1986/7)

Wissenschaftliche Verlagsgedellschaft, Stuttgart, Germany.

RASPBERRIES AND RELATED FRUITS 4919

0025 Containers holding approximately 150 g of rasp-

berries are typically used. Wide, shallow containers

are preferable to deep containers; each should have

no more than four layers of raspberries to prevent

crushing. Many different types of containers are

available, but among the most popular today

are plastic clamshells.

Postharvest Considerations

0026 The objective of postharvest handling of raspberries

is to slow down the respiration and transpiration rate

of fruit. Respiration and transpiration result in

shrinkage and reduced sweetness. Conditions that

slow down the respiration process are low tempera-

tures, high carbon dioxide levels, and low oxygen in

the storage chamber. Transpiration is slowed down by

high humidity.

0027 Temperature is the easiest environmental

variable to modify for extended storage of rasp-

berries. A 5



C reduction in temperature reduces the

respiration rate by approximately 50%: at 0



the respiration rate is 24 mg of carbon dioxide per

kilogram of raspberry per hour; at 5



C, the rate is 55;

at 10



C, the rate is 92; at 15



C, the rate is 135; and at



C, the rate is 200. Rapid movement of cold,

humid air through the berries is essential during the

first few hours after harvest to slow down respiration

and prevent deterioration. Large growers may have a

precooling facility, specifically designed for removing

field heat, and an additional storage cooler. For every

hour’s delay in cooling, the shelf-life can be reduced

by 1 day. Growers take advantage of natural night

cooling by harvesting fruit as early in the morning

as possible. Mechanical harvesting is often done at

night.

0028 Once the berries are cool, containers are wrapped

in plastic to prevent water loss from the fruit

and condensation on the berries when they are

removed from the cooler. The plastic is not removed

until the temperature of the berries approaches ambi-

ent temperature. The storage room can be maintained

as low as 1



C. Berries will not freeze at or above

this temperature, because the sugars in the fruit de-

press the freezing point.

0029 When the temperature is lowered, the amount of

moisture in the air is reduced. For raspberries, it is

critical to maintain a humid atmosphere (90–95%)

simultaneously with a low temperature to prevent

water loss from the fruit. Special cooling units

designed to maintain a high humidity are required

for raspberries. At 25



C and 30% relative humidity,

fruits lose water 35 times faster than at 0



C and 90%

relative humidity.

0030 A high carbon dioxide (15–20%) and/or low

oxygen (5–10%) atmosphere will reduce respiration

and mold growth. Botrytis, Rhizopus, Alternaria,

Penicillium, and Cladosporium can cause postharvest

fruit rots, depending on the storage temperature and

carbon dioxide level. Modified atmospheres are used

frequently when raspberries are transported long dis-

tances. Special semipermeable wraps are sometimes

used by shippers to create a modified atmosphere

(low oxygen, high carbon dioxide) within individual

containers. Low-oxygen atmospheres will extend the

shelf-life of raspberries, but bad-tasting aldehydes

and alcohols can accumulate in the raspberry fruit

when oxygen is limited for an extended period of

time. Off-flavors and browning also develop when

raspberries are held under elevated carbon dioxide

levels for an extended period. Raspberries are con-

sidered to be at moderate risk of physiological injury

from high-carbon dioxide or low-oxygen atmos-

pheres.

0031The loss of raspberries from harvest to the con-

sumer’s table has been estimated at more than 40%.

A 14% loss occurs from farmer to wholesaler, a 6%

loss occurs from wholesaler to retailer, and 22%

is lost between the retailer and consumer. Most of

these losses result from poor handling of berries

after harvest.

Fruit Uses

0032Raspberries have been eaten fresh for thousands

of years. Medicinal uses of raspberries are fre-

quently found in the literature, with references to

raspberry leaf tea dating to the sixteenth century. In

the early 1900s, black raspberry juice was extracted,

concentrated, and used as an edible dye for food-

stuffs, such as meat. Raspberries were also dehy-

drated for long-distance transport. Today, raspberry

fruits are either harvested by hand and eaten fresh, or

machine-harvested and processed. Approximately

27 000 tonnes are processed each year. The major

products of processing are IQF, block frozen, pure

frozen (8–15



Brix), juice (about 9



Brix), concen-

trate, canned, aseptic packs, and preserves. These

products are then packaged and sold directly to

the consumer, or reprocessed into jam, jelly, dessert

topping, pie filling, icecream, yogurt, and other

desserts. Raspberry juice is usually blended with

apple, pear, or grape juice, because the flavor is

too intense for direct consumption. Recently, the

demand for fruit wines has increased, and raspberries

make one of the better wines. Some wineries add

raspberry juice to grape wine to obtain a less ex-

pensive raspberry-flavored wine. Raspberry beer is

also made at breweries and meaderies. The popular-

ity of raspberries continues to grow as many

raspberry-containing products are now on supermar-

ket shelves.

4920 RASPBERRIES AND RELATED FRUITS

See also: Fruits of Temperate Climates: Factors

Affecting Quality; Spoilage: Molds in Spoilage

Further Reading

Crandall PC and Daubeny HA (1990) Raspberry manage-

ment. In: Galletta GJ and Himeirick DG (eds) Small

Fruit Crop Management, pp. 157–213. Englewood

Cliffs, NJ: Prentice Hall.

Green A (1971) Soft fruits. In: Hulme AC (ed.) The Bio-

chemistry of Fruits and their Products, vol. 2, pp. 375–

410. New York: Academic Press.

Jennings DL (1988) Raspberries and Blackberries – Their

Breeding, Diseases and Growth. New York: Academic

Press.

Kader AA (1997) A summary of CA requirements

and recommendations for fruits other than apples and

pears. In: Kader AA (ed.) Proceedings of the Controlled

Atmosphere Research Conference 3: 1–34. Davis, CA.

Ourecky DK (1975) Brambles. In: Janick J and Moore J

(eds) Advances in Fruit Breeding, pp. 98–129. West

Layfayette, IN: Purdue University Press.

Pritts M and Handley D (1989) Bramble Production Guide.

Northeast Regional Agricultural Engineering Service

Bulletin 35. New York: Cornell University.

RECOMBINED AND FILLED MILKS

W Kneifel, University of Agricultural Sciences, Vienna,

Austria

This article is reproduced from Encyclopaedia of Food Science,

General Considerations

0001 The manufacture of recombined milk and milk prod-

ucts is a technology that has emerged over the past

three decades. During this time, there has been a

worldwide development in the establishment of

dairy recombination plants, mainly in countries that

have a limited indigenous dairy industry, or in regions

suffering from seasonal deficiencies in milk supply.

Recombined dairy products are therefore ensuring a

year-round supply for many households in developing

countries, and also enabling the extension of the

local dairy industries. However, for the industrialized

countries, milk recombination offers the opportunity

to transfer raw materials (milk powders, anhydrous

milk fat, etc.) from surplus production areas to defi-

ciency areas, in order to compensate for the above-

mentioned problems and to open up new markets.

Hence, it should be taken into consideration that

world stock levels and prices of butter and milk

powder are strongly affecting the development of

recombination industry as well as the trend of prices

of recombined dairy products.

Definitions

0002 In principle, most types of dairy products can also be

produced in a reconstituted or recombined form. In

the Code of Principles Concerning Milk and Milk

Products, the Codex Alimentarius Commission of

the Food and Agriculture Organization and World

Health Organization has considered the relation

between conventional and recombined milk prod-

ucts: it was determined that all products must be

based on the use of fresh milk, reconstituted milk,

or recombined milk. Recombined products can be

subcategorized into seven main groups: milk, cream,

evaporated milk, sweetened condensed milk, cultured

milk products, butter, and cheese. According to def-

inition, a reconstituted milk product is the product

resulting from the addition of water to the dried or

condensed form of the product in the amount neces-

sary to reestablish the specified water: solids ratio. A

recombined milk product is the product resulting

from the combining of milk fat and milk solids-nonfat

(SNF) in one or more of their various forms, with or

without water. This recombination must be made in

order to reestablish the product’s specified fat: SNF

ratio and solids: water ratio. Among these two fun-

damental categories of special milk products, the

following designations are also commonly distin-

guished: toned milk is a product containing locally

produced milk enriched with reconstituted skim-milk

solids in order to obtain the average milk composition

(e.g., high-fat milk, such as buffalo milk, is adapted to

cows’ milk composition, or local cows’ milk showing

adverse variations in composition is adjusted to

normal composition). Blended milk is a product in

which recombined milk is used in mixture with local

fresh milk in order to restore the fluctuations in local

milk production. Filled milk is a recombined product

in which milk fat is partly or completely replaced by

locally available vegetable oils.

Ingredients Used for Recombination

0003The quality of recombined dairy products is directly

influenced by the quality of the ingredients used.

Nutritional, technological, and sensory specifications

RECOMBINED AND FILLED MILKS 4921

of raw materials must be considered in order that the

recombined products resemble the original products.

Typical compositions of some selected products are

shown in Table 1.

Dried Milk and Milk Protein Powders

0004 Skim-milk powder is generally the most usual com-

ponent for providing milk proteins in the manufac-

ture of recombined dairy products. Whole-milk

powder (prevailingly ‘instantized’ types) can be used

as a source for both SNF and milk fat, but oxidative

changes in the fat phase, leading to sensory deterior-

ation, are limiting its application. Certain propor-

tions of buttermilk powder can be used more or less

advantageously to enhance typical flavor characteris-

tics. In addition, different types of whey protein

powders and caseinates, and, recently, retentate

powders (for the manufacture of cheese) made from

ultrafiltered milk are coprocessed because of attribut-

ing certain functional properties to the final products.

(See Casein and Caseinates: Uses in the Food Indus-

try; Whey and Whey Powders: Production and Uses.)

0005Reconstitutability, heat stability, and viscosity

properties are the most important parameters,

limiting as well as enabling the utilization of milk

powders in recombined products. These properties

are determined mainly by the preheat treatment ap-

plied during milk powder production as well as by

seasonal variations in raw milk composition. Because

a number of milk proteins are heat-labile, the extent

to which they are denatured reflects the heat treat-

ment applied during milk powder manufacture. This

effect is also used as an indicator for its suitability to

be applied in a diverse array of recombined products.

The amount of undenatured whey protein (as charac-

terized by the ‘whey protein index’ or the ‘heat

number’ analysis) is usually taken as a measure for

milk powder classification, but for certain purposes,

dried milk is also classified, based on other analytical

indicators (see Table 2). Besides these parameters,

moisture and fat content, solubility index, bulk dens-

ity, flowability, wettability, scorched particles, rennet-

ability, emulsification properties, titratable acidity,

sensory aspects, and bacteriological requirements

are also included in various milk powder specifica-

tions. Most of these properties can be influenced to a

certain extent by applying a defined powder technol-

ogy. However, some particular factors are addition-

ally improved by using certain additives to the

product. (See Whey and Whey Powders: Protein Con-

centrates and Fractions.)

0006Milk powder is usually received in 25-kg multiwall

bags, with an inner layer consisting of polyethylene.

Alternatively, large bulk bins with a capacity of 200–

1000 kg are used.

tbl0001 Table 1 Typical composition of recombined milk products

Ingredients Product formulations (kg t

1

)

Recombined

milk

Recombined

cream

Recombined

sweetened

condensed milk

Skim-milk powder 80.5 85 30 229

Buttermilk powder 9.7 45

Anhydrous milk fat 33.3 35 190 88.5

Water 876.4 880 733.2 250

Carrageenan 0.3

Emulsifiers 1.5

Sucrose 432

Seed lactose 0.5

tbl0002 Table 2 Heat classification and applicability (*) of skim-milk powder to recombined dairy products

Categories of skim-milkpowder

Extra-lowheat Low heat Medium heat Medium-high heat High-heat

Classification parameters

Whey protein index (ADMI

, IDF) nd 6.0 5.9–4.5 4.4–1.5 1.4

Heat number (IDF) nd 80 80.1–83.0 83.1–88.0 88.1

Cysteine number 26–33 34–41 42–49 50–60 60

Recombined products

Pasteurized milk * * *

UHT milk * *

Sterilized milk * *

Evaporated milk *

Sweetened condensed milk * *

Yogurt * *

Cheese * *

Butter *

Icecream * * * *

American Dairy Products Institute (formerly American Dry Milk Institute), Chicago, Illinois, USA.

Specially manufactured, ‘heat-stable,’ high-heat powder is used.

nd, no data available.

4922 RECOMBINED AND FILLED MILKS

Fats and Oils

0007 Among the traditional dairy-based fat sources – an-

hydrous milk fat (AMF), unsalted butter, anhydrous

butter oil, butter oil – AMF has been used most

because of its better keeping quality. In order to

maintain a good storage stability (6–12 months) of

AMF, suitable packaging in steel drums under an inert

atmosphere must be applied. Recently, fresh frozen

milk fat and soft-fat fraction (produced by fractional

crystallization from milk fat) have also been success-

fully employed in recombined products. Because of

their pronounced organoleptic properties, the use of

vegetable oils for the manufacture of filled dairy

products is restricted to a few oil sources. Only

palm oil, coconut oil, soya bean oil, and, to a certain

extent, maize oil have proved to be suitable. For filled

milks, highly refined, bleached vegetable oils are sug-

gested. Some of the oils contain considerable amounts

of natural antioxidants. However, all fat components

have to be regarded as very sensitive to oxidative and

lipolytic rancidity, leading to the formation of objec-

tionable off-flavors. Specifications regarding fats or

oils usually contain parameters such as fat and mois-

ture content, fatty acid composition, maximum con-

centration of free fatty acids, rancidity, peroxide

value, trace elements levels, and organoleptic proper-

ties. (See Butter: The Product and its Manufacture.)

Water

0008 Water is the major constituent in many of the recom-

bined dairy products. It is therefore essential that the

water used fulfils several standards for drinking

water, as laid down by the World Health Organiza-

tion. Besides sensory properties, physical, chemical,

(micro)biological, and radiological factors are impor-

tant. It has been shown that some physicochemical

parameters strongly coinfluence deposit formation

during thermal processing of recombined products.

Today, many countries impose established limits and

specifications for drinking water. According to the

recommendations of the International Dairy Feder-

ation (IDF), water to be used for the recombination

of dairy products should not exceed the following

maximum salt concentrations: total hardness,

100 mg of calcium carbonate (CaCo

) per gram of

water; chloride, 100 mgg

1

; sulfate, 100 mgg

1

;

nitrate, 45 mgg

1

Additives

0009 Additives can fulfil several targets in recombined

products. Owing to certain losses during production

and storage, the raw materials used for recombin-

ation may contain a lower vitamin content than

conventionally produced milk products. In this case,

the final vitamin content of the recombined product

would be reduced. Fortification with fat- and water-

soluble vitamins, either as single components or in

readily prepared mixtures, is therefore applied fre-

quently or is even obligatory. In general, it was

noted at the last IDF seminar on milk recombination,

in 1988, that recombined dairy products are of a high

nutritive value and comparable to conventional dairy

products. (See Vitamins: Overview.)

0010Antioxidants exhibit a very complex function in

preventing the generation of oxidized flavor of the

fat components in the product, Since some particular

vitamins (tocopherols and ascorbic acid) are capable

of inhibiting free radical chain reactions in the lipid

phase, they are commonly added as antioxidants. (See

Antioxidants: Natural Antioxidants.)

0011Stabilizers and emulsifiers (carrageenan, alginates,

gelatin, lecithin, and glycerolmonostearate) are used

to stabilize the fat phase and also to improve the

texture and the mouth-feel of the products. (See

Emulsifiers: Uses in Processed Foods; Stabilizers:

Types and Function.)

0012Different salts (sodium citrates, phosphates, cal-

cium salts, and sodium chloride) are used to assist

the reconstitution properties, heat stability, and

coagulation, and to act as stabilizing reagents.

0013Besides rennet, the addition of glucono-d-lactone

helps to improve the coagulation properties of milk in

the manufacture of recombined cheese. Pregastric

lipases are applied to enhance the development of

the desired cheese flavor.

0014Sugar, as needed for recombined sweetened con-

densed milk, must fulfil high-quality requirements:

sucrose should be of a refined ‘A1 granular quality’

and of a ‘water white’ color; the lactose seed material

must be finely ground with a maximum particle size

of 10 mm.

0015Depending on the wishes of the consumers, various

natural or synthetic flavors and colors of different

origin are also added. (See Colorants (Colourants):

Properties and Determination of Natural Pig-

ments; Properties and Determinants of Synthetic

Pigments; Flavor (Flavour) Compounds: Production

Methods.)

Recombination Technology

0016The processes for recombination of dairy products

range from rather simple (e.g., recombined pasteur-

ized milk) to more advanced technologies, such as

those applied in the manufacture of defined cheese

varieties or sweetened condensed milk. Milk recom-

bination plants are normally built with capacities

of up to 15 000 l h

1

. Parallel lines are installed

to achieve higher performances. In general, the

RECOMBINED AND FILLED MILKS 4923

recombination technique has been derived from the

conventional processes of dairying, which were fur-

ther adapted and supplemented by procedures such as

weighing, dissolving, mixing, and filtration. ‘Tailor-

made’ recombination systems are frequently built in

order to meet the individual requirements. The raw

materials are processed using discontinuous weigh-

ing, and semicontinuous or continuous recombin-

ation systems. Typical equipment for batchtype milk

recombination basically consists of the following

parts: a jacketed mixing vat, which is equipped with

a calibrated sight glass or mounted on load cells, so

that its contents can be exactly measured, and is

thermostatically controlled by circulation through

a heat exchanger; a powder–liquid blender or a

dumping funnel with a circulating pump for adding

and dispersing powder; equipment for melting milk

fat;aclarifier or duplex filters; a two-stage hom-

ogenizer; equipment for pasteurization;apackaging

line; equipment for refrigerated storage of the

products.

0017Modern, continuously working equipment for milk

recombination with automatic fat dosage, as designed

by Alfa Laval (Lund, Sweden), is shown in Figure 1.It

consists of mixing tanks (6), in which warm water at

40–50



C is metered. Skim-milk powder is supplied to

the funnel (4) and transported automatically into the

mixing tank by water flowing through a bypass line.

The agitator in the mixing tank is started at the same

time as the circulation pump (5). After completely

dissolving the milk powder, AMF is added via a meas-

uring tank (3) from the fat storage and melting tanks

(1). Then, the whole mixture is agitated until com-

plete fat dispersion is obtained. The process is

repeated in the next tank when all ingredients have

been mixed in and added to one tank. The mixture is

continuously drawn from the full mixing tank by a

pump (7), which propels the mixture through duplex

filters (8), which remove foreign particles. After pre-

heating in the heat exchanger (11), the product is

pumped through a homogenizer (10), where the fat

dispersion is completed. A vacuum deaerator vessel

Fat

Powder

Water

Product

fig0001 Figure 1 Plant for the manufacture of recombined milk with fat supply to mixing tanks. 1, Tanks for fat; 2, pumps; 3, weighing tank; 4,

powder-blending funnel; 5, circulation pump; 6, mixing tanks; 7, pump; 8, filters; 9, vacuum deaerator; 10, homogenizer; 11, heat

exchanger; 12, storage tanks; 13, pump. For an explanation, see text. (By courtesy of Alfa Laval Food Engineering AB, Lund, Sweden.)

4924 RECOMBINED AND FILLED MILKS

(9) installed in the line before the homogenizer can be

used to eliminate the air occluded in the powder

particles as well as that picked up during powder

mixing. The homogenized product is then cooled in

the plate exchanger (11) before storage in buffer

tanks or packaging.

0018 Besides high-capacity recombination systems such

as those shown in Figure 1, other automatic proces-

sors can be used advantageously. The Primodan (Hol-

baek, Denmark) recombiner, for example, is equipped

with an adjustable steam-heated butter melter and is

capable of milk production capacity of up to 25 000

1

. Another fully automated and energy-saving

milk powder dissolver is available from Jongia (Leeu-

warden, The Netherlands).

Mixing and Fat Melting

0019 In smaller plants, the powder bags are mostly handled

manually; they are emptied directly into the mixer. In

larger plants, automatic emptying systems are in-

stalled, and the powder is transported pneumatically

into storage silos, from which it is mechanically

conveyed to the mixing system via a weighing hopper

or a screw-feeder.

0020 Milk powder is usually dissolved at high stirring or

mixing rates. Simple mixing devices consist of a cen-

trifugal pump attached to a tank filled with the

defined amount of warm water, with a powder funnel

mounted between. The pump is connected to the

jacketed tank with a pipe enabling sufficient circula-

tion. The milk powder is transported into the tank by

the vacuum thereby obtained.

0021 In general, the choice of mixer used for dissolving

the powder and dispersing the fat depends on the

viscosity and/or the dry matter content of the product

mix. For recombined products of low viscosity (pas-

teurized, sterilized and ultra-heat-treated (UHT) fluid

milk, stirred yogurts), the following systems are used:

turbine or propeller mixers (e.g., Alfa Laval; APV

Rosista, Horsens, Denmark; Scanima, Aalborg, Den-

mark) driven by an electric motor; Venturi jet mixers

(e.g., Danish Turnkey Dairies, Aarhus, Denmark);

static mixers (Primodan, Jongia); high-speed blenders

(TMP mixer, APV Rosista; Tri-Blender, Tri-Clover,

Kenosha, WI, USA). The best dispersion is achieved

when applying a continuous recirculating motion in

the mixing tanks. High-speed blenders are also suited

for the preparation of high-viscosity recombined

products (e.g., evaporated and sweetened condensed

milk, icecream). Another category of mixers are the

disc mill mixers, which are also mainly used in the

production of recombined sweetened condensed

milk. The so-called Disko-Eulgiermix (Figure 2a),

capable of simultaneously homogenizing whilst recir-

culating, and of working under vacuum conditions,

was introduced recently (Balik, Vienna). It is suitable

for preparing products of different viscosity ranges.

By applying a defined vacuum, foaming and picking

up of air can be avoided during mixing. Another

example for a sophisticated mixing unit is the

(b)

(a)

fig0002Figure 2 Examples of special mixing units. (a) Disko-Emulgier-

mix (courtesy of Balik GmbH, Vienna, Austria): 1, vacuum mixing

tank; 2, thermostatically controlled jacket; 3, anchor-type stirrer;

4, disk mill dissolver; 5, flow-through homogenizer; 6, milk

powder intake. (b) Weighmatic (courtesy of Alfa Laval Food En-

gineering AB, Lund, Sweden): 1, powder intake; 2, liquid inlet; 3,

cleaning-in-place inlet; 4, product outlet; 5, weighing tank; 6,

buffer tank. Reproduced from Recombined and Filled Milks, En-

cyclopaedia of Food Science, Food Technology and Nutrition, Macrae

R, Robinson RK and Sadler MJ (eds), 1993, Academic Press.

RECOMBINED AND FILLED MILKS 4925