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

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DAIRY PRODUCTS – NUTRITIONAL

CONTRIBUTION

J Buttriss, British Nutrition Foundation, London, UK

Introduction

0001 Dairy products are traditional dietary items in many

parts of the world, in particular in regions such as

northern Europe where the cooler climate is especially

suited to dairying. The history of milk as a food has

been documented over the centuries and examples of

early dairying are depicted in Egyptian friezes such as

that from the sarcophagus of Queen Kawit from

Der-al-Bahri, between Luxor and Karnack, dating

back 4000 years. There is an even earlier Mesopota-

mian frieze from the temple of Nin-khasarg, near Ur,

which is thought to be 1000 years older.

0002 The popularity of milk as a staple food over the

centuries must partly be due to its versatility. Early

humans discovered that it could be churned to make

butter and fermented with bacterial cultures to pro-

duce cheese and yogurt, all of which were methods of

preserving some or all of the nutrients in milk for

consumption at a later date. (See Cheeses: Dietary

Importance; Milk: Dietary Importance; Yogurt: Diet-

ary Importance.)

0003 This article summarizes the nutritional contribu-

tion made by milk and milk products.

Variety

0004 Today, the range of dairy products on the market is

immense. In most countries, a range of milks with

differing fat contents is available. For example, in the

UK consumers can choose between Channel Islands

milk, with 5.1 g per 100 g fat, through whole milk

(3.9 g per 100 g) to semiskimmed (1.6 g per 100 g fat)

and skimmed milk, which has virtually no fat. Simi-

larly, a wide range of cheeses exists with varying fat

contents: at one end of the spectrum are soft fresh

cheeses, made with skimmed milk and, at the other,

hard cheeses such as cheddar. Also available is cheese

made with nonanimal rennet, suitable for vegetar-

ians. In the UK alone, almost 200 different cheeses

are produced, and cheese is particularly popular in

countries such as France, where an even greater var-

iety is available.

0005 Fermented milk products such as yogurt, smetana,

and kefir have always been popular in Middle Eastern

countries, but their popularity, particularly that of

yogurt, is dramatically increasing in the UK. Again,

a wide range of yogurts exists, from the very-low-fat

to the creamier, whole-milk or Greek-style product,

including set yogurts, stirred yogurts, fruit yogurts,

frozen yogurts and fromage frais. (See Fermented

Milks: Types of Fermented Milks; Yogurt: The Prod-

uct and its Manufacture.)

0006Traditional products such as cream and butter are

still in demand, in spite of their relatively high fat

content, and are being joined by other ‘luxury’ prod-

ucts, such as real dairy icecreams, fresh cream desserts,

and luxury mousses. To meet the demand for a spread

with a buttery flavor, spreads have been developed

which incorporate butterfat for taste but often have a

lower fat and calorie content. (See Butter: The Product

and its Manufacture; Cream: Types of Cream; Ice

Cream: Methods of Manufacture.)

0007A number of products also exist to which nutrients

have been added, such as the calcium-enriched milks,

and yogurts fortified with additional vitamins.

Nutritional Value

0008Most dairy products offer a wide range of nutrients

and this is reflected in the contribution made by milk

and milk products to dietary intake in many coun-

tries. For example, in the UK, milk and milk products

provide over half the calcium in the average diet and

make a significant contribution to the needs of other

nutrients (Table 1).

Nutritional Significance of Milk and Milk

Products

0009In countries where dairying has traditionally been a

strong industry, milk and milk product consumption

tends to be widespread and makes a significant con-

tribution to nutrient needs. For example, the average

daily intake of milk in the UK in 1998 was a little

under half a pint per person (285ml). Table 2 shows

the contribution this quantity of whole milk makes to

the nutrient and energy needs of a 4-year-old girl and

a man. Skimmed or semiskimmed milk would make

smaller contributions to intake of energy and fat-

soluble vitamins.

0010In Scandinavian countries, where dairying is also

traditional, liquid milk consumption is typically

higher than in the UK. However, in warmer climates,

in particular the Indian subcontinent, Africa and

1726 DAIRY PRODUCTS – Nutritional Contribution

South America, climatic conditions lend themselves

less readily to cows’ needs, so that the development of

dairying and, hence, milk-drinking habits has been

far more patchy. Exceptions exist, such as the Masai

in Eastern Africa, whose culture is dominated by the

cow. Similarly, in parts of India, cows have religious

significance but have not until recently been inten-

sively managed for their milk. Table 3 presents esti-

mates of milk consumption in different countries.

0011As it is rich in calcium needed for skeletal develop-

ment and maintenance, milk has traditionally been

seen as an important food during childhood, preg-

nancy, and lactation, when calcium requirements are

particularly high. This view is still supported today

by a recent UK government report. A pint of milk

(0.568 l) provides about 700 mg of calcium. (See

Calcium: Properties and Determination; Children:

Nutritional Requirements.)

Claims of Adverse and Beneficial Effects

to Health

Allergy or Intolerance to Cows’ Milk

0012True milk allergy is typically seen in infants. Although

estimates vary, it is thought that at its peak incidence

in 1–3-year-olds, cows’ milk allergy affects about 1%

of infants. Most children outgrow this reaction to the

protein in milk by their fifth birthday and in many

instances it is short-lived, being brought on by a

gastrointestinal upset.

0013Intolerance to the sugar in milk – lactose – occurs in

those people who lack or who have low levels of the

enzyme lactase, which digests lactose to its compon-

ents, glucose and galactose. This enzyme is invariably

present in the intestines of infants to enable them to

tbl0001 Table 1 Contribution of milk and milk products to daily nutrient intake in the UK

Whole milk Semiskimmed and

skimmed milk

Cheese Allmilkandmilkproducts,

including cheese

Amount % of total

intake

Amount % of total

intake

Amount % of total

intake

Amount % of total

intake

Energy (kJ) 276 3.6 314 4.1 226 2.9 974 12.6

Total fat (g) 4.0 5.2 2.3 3.0 4.5 5.9 12.7 16.7

Saturated fatty acids (g) 2.6 8.6 1.6 5.3 2.8 9.3 8.1 26.9

Polyunsaturated fatty acids (g) 0.1 0.7 0.1 0.7 0.2 1.5 0.5 3.7

Total sugars (g) 4.4 4.3 7.9 7.7 0.1 0.1 16.2 15.7

Calcium (mg) 116 14.1 198 24.1 91 11.1 452 55.1

Iron (mg) 0.1 1.0 0.1 1.0 – – 0.2 2.0

Sodium (mg) 42 1.7 70 2.8 104 4.1 240 9.4

Vitamin C (mg) 1.7 2.7 2.8 4.4 – – 5.0 7.9

Folate (mg) 7 2.9 9 3.7 5 2.0 24 9.8

Vitamin A (mg) retinol eq. 32 4.1 34 4.3 49 6.2 141 17.9

Vitamin D (mg) 0.2 6.3

Reproduced from Ministry of Agriculture, Fisheries and Food (1999) National Food Survey 1998. London: Stationery Office, with permission.

tbl0002 Table 2 Contribution of 285 ml (half a pint) of whole milk to

nutrient needs

Percentage of UKreference

nutrient intake (RNI)

Girls

(4^6 years)

Adult men

(19^50 years)

Energy

12.5 7.6

Fat

19.0 11.5

Saturates

37.3 22.7

Monounsaturates

14.3 8.6

Polyunsaturates

2.7 1.7

Carbohydrate

7.0 4.2

Protein 47.5 16.8

Nonstarch polysaccharide – –

Vitamin A 32.8 23.4

Thiamin 16.4 11.5

Riboflavin 62.5 38.5

Nicotinic acid equivalents 22.1 14.3

Vitamin B

19.4 12.5

Folic acid 17.5 8.8

Vitamin B

143.8 76.7

Vitamin C 10.0 7.5

Calcium 74.8 48.1

Sodium 23.9 10.4

Chloride 26.6 11.7

Copper Trace Trace

Iodine 44.0 31.4

Iron 2.4 1.7

Magnesium 26.7 10.7

Phosphorus 77.0 49.0

Potassium 37.3 16.4

Selenium 15.0 4.0

Zinc 17.7 12.1

There is no RNI for these components of food. For energy, the estimated

average requirement has been given; for fat and carbohydrate, the

desirable average has been given.

Figures for milk composition from Holland B, Unwin ID, Buss DH (1989)

Milk Products and Eggs. Fourth supplement of McCance and Widdowson’s

The Composition of Foods, 4th edn. London: Royal Society of Chemistry and

Ministry of Agriculture, Fisheries and Food.

Figures for RNIs from Department of Health (1991).

DAIRY PRODUCTS – Nutritional Contribution 1727

digest their mother’s milk, but levels fall off in some

adults, particularly those who come from areas of the

world where milk consumption is not traditional.

Hence, in the UK, lactose intolerance is rare among

Caucasians but is experienced by some ethnic groups

of Indian, African, or Chinese extraction. In many

cases, sufferers have low levels of the enzyme and

can thus tolerate small quantities of milk and larger

quantities of foods such as cheese or yogurt. In the

case of cheese, the lactose has largely been lost with

the whey in the cheese-making process. In the case

of yogurt, it is suggested that the b-galactosidase

enzyme, present in the bacterial culture used to

make yogurt, may be able to digest some of the lac-

tose. (See Food Intolerance: Lactose Intolerance.)

Health Benefits of Yogurt

0014A number of health benefits of yogurt have been

claimed, including an ability of certain types of bac-

teria used in the manufacture of yogurt to colonize

the gut and help fend off harmful bacteria.

Coronary Heart Disease

0015One of the risk factors for coronary heart disease

(CHD) is a raised plasma cholesterol level. A number

of factors, including genetic make-up, influence an

individual’s plasma cholesterol level. One such factor

is thought to be intake of saturated fatty acids, par-

ticularly in genetically susceptible people who are less

able to remove low-density lipoproteins (LDLs) from

their blood stream.

0016Many governments have issued guidelines on diet in

relation to heart disease. In the UK, guidelines of

energy and nutrient intake include recommendations

on total fat intake and on fatty acid intake. The guide-

lines on saturated fatty acids (saturates) have been set

with a view to reducing average plasma cholesterol

tbl0003 Table 3 Estimates of liquid milk consumption in a selection of

countries in 1998

Liquid milk consumption

(kg perperson per year) 1998

Australia 103

Canada 90.7

Chile 30.3

Czech Republic 57.0

Denmark 93.8

Finland 143.5

France 75.5

Germany 64.4

Iceland 153.6

Ireland 143.5

Israel 59.2

Italy 85.3

Japan 40.2 (1997 figure)

Netherlands 54.9

Norway 119.3

South Africa 25.1

Spain 94.3

Sweden 116.4

UK 117.9

USA 98.9

Reproduced from International Dairy Federation (1999) The world dairy

situation 1998. Bulletin of the IDF 339: 49, with permission.

tbl0004 Table 4 Contribution of sources of fat and saturates in the household food supply

Fat Saturated fatty acids

gday

1

%gday

1

Whole milk 4.0 5.2 2.6 8.6

Reduced-fat milks 2.3 3.0 1.6 5.3

Cheese 4.5 5.9 2.8 9.3

Total milk, cream, and cheese 12.7 16.7 8.1 26.9

Carcass meat and poultry 6.9 9.1 2.6 8.6

Bacon, ham, meat products 9.8 12.7 3.7 12.3

Total meat 16.7 21.9 6.3 20.9

Total fish 1.3 1.7 0.3 1.0

Eggs 1.4 1.8 0.4 1.3

Butter 4.5 5.9 3.0 10.0

Margarine 2.9 3.8 0.8 2.7

Other fats and spreads 13.7 17.8 2.7 9.0

Total fats and spreads 21.1 27.7 6.5 21.6

Total vegetables 4.9 6.4 1.5 5.0

Total fruit 1.3 1.7 0.3 1.0

Cakes, biscuits and pastries 6.8 8.9 3.3 11.0

Bread, flour, breakfast cereals 1.6 2.1 0.3 1.0

Total cereals 13.1 17.2 5.1 16.9

Other foods and beverages 3.7 4.9 1.6 5.3

Total all foods and drinks 76.9 100 30.1 100

Reproduced from Ministry of Agriculture, Fisheries and Food (1999) National Food Survey 1998. London: Stationery Office, with permission.

1728 DAIRY PRODUCTS – Nutritional Contribution

concentration by 0.4 mmol l

1

, thus bringing it down

to a level associated with a substantially lower inci-

dence of CHD than witnessed in the UK at present.

0017 In 1999, saturates provided an average of 14.9% of

energy intake. The Department of Health report ad-

vises that average consumption is reduced to 10% of

total energy (11% of food energy). This advice does

not apply to children under the age of 2 years.

0018 Intake of specific foods has not been linked directly

with CHD risk. However, a reduction in foods con-

tributing significant amounts of fat (Table 4), espe-

cially saturated fatty acids, to the diet has been

recommended for those people with a high fat intake.

Such advice calls for a reduction in foods such as

whole milk and its products, fatty meats, fried

foods, spreading and cooking fats, and baked goods

such as biscuits, cakes, and pies.

0019 A wide range of lower-fat milks and milk products

is now available, so that those people concerned

about their fat intake can change to a lower-fat option

rather than cutting down on dairy products and

losing a valuable source of calcium and other essential

nutrients.

Dairy Products and Dental Health

0020 The frequency of sugar consumption is positively

related to the incidence of dental caries. Although

lactose (milk sugar) is moderately cariogenic if con-

sumed in isolation, when it is consumed as part of milk

any cariogenicity is counteracted by protective factors

in milk. Consequently, milk without added sugars can

be considered to be virtually noncariogenic. (See

Dental Disease: Etiology of Dental Caries.)

0021 Cheese is now recognized to help protect against

dental decay. Dental caries results from acid produc-

tion at the tooth surface, following fermentation of

sugar by the bacteria present in dental plaque. It has

been known for some time that eating a small amount

of cheese at the end of a meal can counteract this

effect; however, a recent study indicated that cheese

incorporated within a meal confers similar benefits,

in so far as it reduces the fall in plaque pH recognized

to be associated with decay.

0022 A number of possible mechanisms have been

offered to explain this beneficial effect of cheese.

Eating cheese causes an increased flow of saliva,

which is slightly alkaline and acts as a buffer to the

acid. Also, cheese favors remineralization of any

damage since it is rich in calcium and its consistency

brings calcium and phosphorus into contact with the

tooth surface.

See also: Butter: The Product and its Manufacture;

Cheeses: Quarg and Fromage Frais; Dietary Importance;

Cream: Types of Cream; Dental Disease: Etiology of

Dental Caries; Fermented Milks: Types of Fermented

Milks; Food Intolerance: Lactose Intolerance; Ice

Cream: Methods of Manufacture; Milk: Dietary

Importance; Yogurt: The Product and its Manufacture;

Dietary Importance

Further Reading

Ashwell M (ed.) (1997) Diet and Heart Disease: A Round

Table of Risk Factors, 2nd edn. London: Chapman &

Hall.

British Dietetic Association (1987) Children’s Diets and

Change. A report of the Child Health and Nutrition

Working Party. Birmingham: British Dietetic Associ-

ation.

Buttriss JL (ed.) (2001) Adverse Reactions To Food. British

Nutrition Foundation Task Force Reporter. Oxford:

Blackwell Science.

Department of Health (1991) Dietary Reference Values for

Food Energy and Nutrients in the UK. Committee on

Medical Aspects of Food Policy. Report on Health and

Social Subjects 41. London: HMSO.

Department of Health (1994) Nutritional Aspects of Car-

diovascular Disease. Report on Health and Social Sub-

jects 46. London: Stationery Office.

Department of Health (1998) Nutrition and Bone Health;

with Particular Reference to Calcium and Vitamin D.

Report on Health and Social Subjects 49. London: Sta-

tionery Office.

DHSS (1989) Dietary Sugars and Human Disease. Com-

mittee on Medical Aspects of Food Policy. Report on

Health and Social Subjects 27. London: HMSO.

International Dairy Federation (1999) The world dairy

situation 1998. Bulletin of the IDF 339: 49.

Ministry of Agriculture, Fisheries and Food (1999)

National Food Survey 1998. London: Stationery Office.

Moynihan P (2000) Food and factors that protect against

dental caries. BNF Nutrition Bulletin 25(2) (in press).

Renner E (1983) Milk and Dairy Products in Human

Nutrition. Munich: Volkswirtschaftlicher Verlag.

Renner E (1989) Micronutrients in Milk and Milk-Based

Food Products. London: Elsevier Applied Science.

Silva MF A et al. (1986) Effect of cheese on experimental

caries in human subjects. Caries Research 20: 263–269.

The Dairy Council (2000) Milk Matters: A Guide to the UK

Dairy Industry and its Products. London: The Dairy

Council.

DAIRY PRODUCTS – Nutritional Contribution 1729

DATE PALMS

A A A Kwaasi, King Faisal Specialist Hospital &

Research Centre, Riyadh, Saudi Arabia

Background

0001 The date palm (Phoenix dactylifera L.) has been

known for as long as recorded history. Apart from

its importance as a food source for man and animals,

all parts of the plant have their use in medicine,

pharmacognosy, chemistry, and religion, and in the

fishing, horticulture, and construction industries.

Like all economic plants, dates are also afflicted by

a number of diseases from microbes, insects, and

rodents. Dates are one of the few foods that have a

high potassium content and, at a certain stage of

development, have a low sucrose content. As know-

ledge in agriculture, medicine, and industry develops,

so does the number of new agents that are found to be

harmful or useful to man. In the last two decades,

there has been a dramatic increase in the number of

foods that have been found to be allergenic, and

accidental consumption of these foods by susceptible

individuals has led to fatalities. Date fruit and pollen

are no exception. Results of recent research have

revealed that both date pollen and fruit peptides

from certain date cultivars can elicit allergic responses

in susceptible individuals and share a number of

cross-reactive epitopes with some well-known aller-

gens. The beneficial properties of the date are such

that its cultivation should be expanded.

History

0002 The date palm has provided inhabitants of the hot dry

regions of the world with a highly desirable food and

has therefore been thoroughly exploited. The earliest

archeological finds dated 5000–6000 bc were from

Iran, Egypt, and Pakistan. Remnants of dates have

been found in excavations of Neolithic sites dating

back 7000–8000 years and in the tombs of Egyptian

Pharaohs. The earliest cultivated finds dated around

4000 bc were from Eridu, Lower Mesopotamia in the

Bronze Age. Dates are mentioned in Akkadian and

Sumerian cuneiform sources (c. 2500 bc) and later.

The date palm has historical and religious fame in

Judaism, Christianity, and Islam. Date palm fronds

are used on Palm Sunday and are thought to have

been used in Jesus’ triumphant entry into Jerusalem

(Synoptic Gospels, New Testament), and the book of

Psalms states that ‘the righteous shall flourish like a

palm tree.’ Date fruits are eaten by most Christians

during Christmas and are used in breaking the fast

during the Islamic Holy Month of Ramadan. It

is mentioned in the Qur’a

n (Maryam 19:25–26) in

relation to Jesus’ birth, and there are a total of 26

references to dates in this holy book.

Origin and Distribution

0003The palm is presumed to have originated in the

Persian Gulf area and in Western India, but its exact

origin is difficult to establish. Apart from remnants of

some wild dates still present in areas around Jordan

and the Iraq–Iran border, all dates known today are

fully domesticated. The date was naturalized in

Arabia and spread through Northern Africa, Spain,

the drier parts of the Nile valley, and around the

Euphrates River. From Spain, it was introduced to

America, where it is now grown commercially in the

warm valleys of Southern California and Arizona.

Dates are cultivated throughout the desert regions of

the world and grow well between latitudes of 15 and



N, from the Canaries and Morocco in the west,

to India in the east. It is recorded from all the inner

and littoral parts of North Africa, the southern parts

of the Balkan Peninsula, and Asia Minor, from Syria,

Palestine, Transjordanian, Iraq, Arabia Peninsula,

Iran and Baluchistan regions. Dates are grown on

family compounds and along streets and highways,

and are seen in every conceivable space in the Middle

East. The date is cultivated as an ornamental plant in

South Europe, where it seldom matures into fruit,

except in southern Italy and Spain, and is cultivated

in parts of Queensland, Australia.

Botany

0004The date palm belongs to the Class: Monocotyledo-

neae, Subclass: Areciae and is a member of the Family

Arecaceae (formerly Palmaceae). It is an aborescent,

erect, unbranched stem with large petioles that are

sheathed at their bases. The tree is characterized by

numerous offshoots that are produced at the base of

the trunk of young palms. The average mature tree is

about 20 m tall, but some may be as high as 30 m. A

young, actively bearing date palm, showing offshoots

and fruits at the end of the ‘khalaal’ stage is shown in

Figure 1.

0005The trunk of the palm is covered with persistent

grayish leaf bases. It is surmounted by a handsome

array of pinnately divided long leaves and needle-

sharp fronds. Between 10 and 20 new leaves are

1730 DATE PALMS

produced annually. Date palm leaves are subtended at

their bases by a cylindrical sheath of reticulate mass

of tough, fibrous material, together forming a tight

protective envelope for the terminal bud. Even though

the phyllotaxy of date palm is not always clear,

it forms the basis for the identification of some

cultivars.

0006 The palm produces many long rope-like adventi-

tious roots that arise from the spherical base of the

stem, often traversing long distances in search of

water and nutrients. In Egypt and Algeria, mycor-

rhizal association of the root tips with arbuscular

fungi of the genera Glomus, Autochthon, Aoufous,

and Sclerocystis is common, but Glomus mosseae has

been found to be most efficient in helping the date

palm maintain water balance.

0007 Male and female flowers are borne on different

plants (dioecious), but all date plants look alike.

Both male and female inflorescences are branched

and are completely enclosed during development by

sheathing fibrous spathes. The female inflorescence

has pendulous branches, and florets (small flowers)

are spread out along their entire length. A female

flower with branches of male inflorescence inserted

and tied, and a male inflorescence with abundant

pollen are shown in Figure 2a and 2b, respectively.

0008A typical female flower (gynoecium) has a small

cup-shaped calyx tube formed from three outer peri-

anth segments. It has three inner perianths, which are

small and circular, and are closely appressed to the

three carpels of the superior apocarpous ovary, each

of which is surmounted by a short, hooked stigma.

Only one ovary develops into a seed after fertiliza-

tion. The floral formula of the female flower is:

0009The male palms produce between 30 and 50 inflor-

escences yearly. Their spathes are narrower and

shorter than the female flowers and are covered

with a rust-colored powdery coating (See Figure 2b).

The inflorescence consists of a short, stiff peduncle

with numerous copious branches and white, sweet

scented flowers along their length. The male flower

has six stamens bearing long flattened anthers with

undulate margins and has the floral formula:

. The center of the androecium bears a

(vestigial) small rudimentary ovary. Pollen produc-

tion is prolific, and typical pollen is light, small, and

pale yellow in color, and measures about 8 by 25 mm.

Date pollen is distinct and only slightly resembles

the pollen of Sabal palmetto and Ginkgo biloba

(see scanning electromicrograph of pollen grains in

Figure 3).

(a) (b)

fig0001 Figure 1 (see color plate 42) (a) Young actively bearing date palm with offshoots or suckers. (b) Bunches of fruit from the same tree

photographed at the end of the ‘khalaal’ stage.

DATE PALMS 1731

Genetic Diversity

0010 The heterozygous nature of the palm, its dioecious

habit and the long period of cultivation, has led to the

establishment of thousands of different date cultivars.

In Riyadh (Saudi Arabia) alone, about 100 different

cultivars are sold in the local open markets during

harvest. A photograph of 18 of these cultivars is

fig0003 Figure 3 Scanning electromicrograph of two pollen grains.

(a) (b)

fig0002 Figure 2 (see color plate 43) (a) Female flower with branches of male inflorescence inserted and tied to the female. (b) Opened male

inflorescence with abundant pollen.

1732 DATE PALMS

shown in Figure 4. Results of enzymatic and genetic

studies have been carried out on the fruits of several

cultivars in Algeria and Iraq, and other studies of

isoenzymes in leaves demonstrate that there is a high

percentage of polymorphic loci, strong heterozygos-

ity, and genetic diversity among cultivars. Extensive

date breeding continues, and reports from the African

Centre of Diversity indicate that date cultivars able

to withstand such characteristics as alkaline soil,

drought, frost, heat, heavy soil, high pH, salt, sand,

slope, smog, and water logging have been bred. Fur-

thermore cultivars with such fruit qualities as attract-

iveness, resistance to spoilage, heavy yield, late or

early maturity, richness of flavor, smoothness of

skin, and coloration are available in the germplasm

repository of USDA, California, USA.

0011 Many of the native palms in the Arabian Peninsula

and North Africa have originally grown from either

volunteer or intentionally nursed seedlings, but in

modern date culture, many different cultivars are

propagated vegetatively from offshoots or suckers

(See Figure 1a). There are hundreds of established

varieties or cultivars, and it is estimated that there

are 350 cultivars of soft dates in the Basra region of

Iraq alone.

0012Dates can be categorized into three different groups

depending on the type of fruits they produce: soft,

semisoft, and dry. Soft dates have a soft fleshy con-

sistency and contain about 60% sugar in the form of

glucose and fructose, and this concentration is suffi-

cient to prevent undesired fermentation. They are

used fresh or preserved in the form of ‘agwa,’ a

pressed mixture of dates. Semisoft dates have a firmer

flesh and contain much more sugar than soft dates.

Dry dates contain much more sugar than soft and

semisoft dates (65 to 70%), and they ripen and

dry to a hard consistency while still on the palm tree.

Ecology

0013The environmental demands of date palms are

summed up in the old Arab adage that ‘the date

palm needs its feet in running water and its head in

the fire of the sky.’ Date palms enjoy high tempera-

tures and can withstand very low temperatures for

short periods only. Temperatures below 8



C are

harmful. They can tolerate annual precipitation of

between 31 and 403 mm and grow well in regions of

low humidity and where rainfall is low or non-

existent. Flowering is favored by long, hot, and

1234

5678

910 1112

13 14

17 18

15 16

fig0004 Figure 4 (see color plate 44) Eighteen of the most popular date cultivars sold in Riyadh, Saudi Arabia. Their names are as follows:

1 ¼Assela, 2 ¼Labana, 3 ¼Sabbaka, 4 ¼Rothana, 5 ¼Manifi, 6 ¼Naboot-Ali, 7 ¼Sefri, 8 ¼Mabroom, 9 ¼Roshidia, 10 ¼Sokary,

11 ¼Khodri, 12 ¼Safawi, 13 ¼Halaw/Helwa, 14 ¼Hanini, 15 ¼Barhi, 16 ¼Juffair, 17 ¼Qattar, 18 ¼Seeleg.

DATE PALMS 1733

completely dry periods, and an average temperature

of 30



C is considered optimal for proper ripening.

The plants can tolerate a wide variety of soil types

and a fair amount of alkalinity (pH range of 5–8.2)

with the only proviso that the soil be well aerated. To

bear well, the roots must be in a stratum with less

than 1% of alkali salts. Recently, salt-tolerant date

cultivars have been bred, and cultivation in halophy-

tic (salty) soils close to the sea has been made pos-

sible. Most date palms are grown under carefully

controlled irrigations or in oases. Date trees must be

pruned to allow new leaves to grow, to prevent rodent

and insect infestation, and to facilitate pollination,

fruit setting, and harvesting.

Propagation

0014 Dates can be generally grown from seeds or vegeta-

tively propagated from offshoots, but in recent years,

organogenesis has been researched, and the use of

plantlets from tissue culture has become popular. Al-

though impractical for the poor peasant farmer, it has

the advantage that several plantlets can be produced

in a very short time from a small amount of meristem-

atic tissue.

0015 Growth of dates from offshoots is, however, the

preferred option for the native grower and has almost

completely replaced the old fashioned growth from

seeds. Adult date palms in their early years produce

many offshoots, and these offshoots are removed

from the parent plant and transplanted about 9.2 m

apart. The young transplanted tree needs protective

wrapping or shelter against cold, heat, and wind, and

should be watered daily during the first week and

once weekly thereafter until the roots have fully

developed. In Saudi Arabia, it is common practice

for whole mature trees to be dug out and transplanted

as a ‘quick fix.’ Growth from seeds is still used in a

few areas for pollen production. Date plantations

should be irrigated and the soil fertilized. Inter--

cropping of date trees with citrus and other fruit

plants is common practice, and alfalfa (Medicago

sativa) is often grown.

Pollination, Fruit Formation, and

Development

0016 It is estimated that one male plant is sufficient to

pollinate 50–100 female date trees, and it is common

practice to plant 2.4 male plants per hectare. In Saudi

Arabia, dates usually flower between February and

April, and dates are pollinated during these months.

Date pollen can be stored at various temperatures for

differing lengths of time without much loss of viabil-

ity or ability to fertilize female flowers. Dates should

be naturally wind-pollinated, but there is a small

contribution from visiting insects and birds. How-

ever, the native form of pollination is to insert one

to three branches of male inflorescence in the fully

exposed female inflorescence (See Figure 2a). In order

to effect efficient fertilization and to maximize fruit

yield, this method has largely been replaced by hand

pollination, in which pollen is placed in porous sacs

or dusters and spread as dust on female flowers or by

mechanical spraying. A temperature of 35



C is opti-

mal for pollen germination. After successful pollin-

ation and fertilization, one of the three ovules of the

ovary develops into a one-seeded drupe with a fleshy

inner tissue and an outer shiny chitinous skin.

0017The fertilized rudimentary fruit is referred to in

Arabic as ‘hababauk.’ Dates take about 200 days to

reach maturity. After pollination, the fruit passes

through four distinct phases, known in Arabic as

‘kimri,’‘khalaal,’‘rutab,’ and ‘tamr’ stages. The

kimri stage is the time from which the rudimentary

seed is formed until it is about 17–19 weeks old. The

fruit increases rapidly in size and weight, and in its

reducing sugar, acid, and moisture content. This ends

the time of botanical maturity, and the fruit turns

yellow or red, depending on the cultivar. The khalaal

stage is the second stage of development (from 19 to

25 weeks). Weight gain is slow, but sucrose content

increases, whereas the moisture content decreases.

Tannins start to precipitate, leading to a reduction in

astringency, making some varieties palatable and

commercially mature at this stage. At the rutab

stage, which sets in from around 26 to 28 weeks,

there is further moisture loss, and in some varieties,

sucrose turns into inverted sugar, and there is

browning and skin softening. The moisture content

decreases to about 35%, and this is the time during

which fresh soft dates are sold. The final stage, tamr,

is used only to refer to dates that are left on the palm

trees to undergo further ripening, and some dates

become self-preserving at this stage.

World Date Production

0018It is estimated that there are about 90 million date

palms in the world. One United Nations Food and

Agricultural Organization statistical report names 31

countries as the main date-producing countries. Out

of these, only 21 countries export any appreciable

amount of their produce. However, 72 countries

throughout the world import between 11 and over

500 000 tonnes of dates annually. In the year 2000,

the world date production totalled 5.21 million

tonnes. Date production figures for each of the 20

leading date-producing countries (except India) are

shown in Figure 5.

1734 DATE PALMS

Pests, Diseases, and Losses

0019 Dates are afflicted by a number of pests and diseases,

which result in substantial losses. Even though new

diseases keep emerging, the most important and

widespread of these is Bayoud disease, a fungal wilt

disease of date trees caused by the fungus Fusarium

oxysporium f. sp. albenidis. Plants infected by this

and other wilt fungi make way for opportunistic

microbes and pests to cause more damage. Some

newly emerging diseases are fungal rhizosis (Cerato-

cystis radicicola) in South Africa and Serenomyces

in California, and two new pathogens, Phomopsis

phoenicicola and Fusarium equiseti, have been

reported from Iraq. The most recently reported dis-

eases (December 2000) are the phytoplasma ‘white

tip die-back’ in Northern Sudan and the ‘slow decline’

disease in North Africa.

0020 Dates can also be attacked by a range of pests: the

scale insect is important in the Dangola District of

Northern Sudan, and termite damage is common.

Pakistani dates are mainly attacked by borers (Cole-

optera spp.) and the red palm weevil, Rhynchosporus

ferrugineus. Recently, this weevil has spread to Israel,

Jordan, the Palestinian Authority, and Saudi Arabia.

An isolated report from Oman implicates the Indian

palm weevil (Pseudophilus testaceus) as the cause of

some date tree infestations.

0021 Ants and locusts are troublesome, and mice and

other rodents feed on leaves, tender roots, and fruits.

Damage to fruit through direct infestation by fungi

results in the production of phytoalexins, and afla-

toxin contamination causing severe fungitoxicity

during packaging or marketing has been reported in

the cultivars Lulu and Naghal. A list of other disease

causing agents, pests, and some of the resultant symp-

toms is given in Table 1.

Harvesting, Packaging, and Storage

0022Under optimum conditions, dates start fruiting in 3–5

years of planting an offshoot and reach full maturity

in 12 years. Dates are usually harvested from July

to September, and the estimated yield of dates per

bunch is about 5–15 kg. After harvest, dates are

packed or transported loose to the market, packing,

or processing plants. The majority of techniques

that are applied by commercial growers to prevent

infestation and spoilage are fumigation, heat treat-

ment, chilled storage, and irradiation. The most

Iran

Egypt

Saudi Arabia

Pakistan

Iraq

Algeria

Sudan

UAE

Oman

Libya

Tunisia

China

Morocco

Yemen

Qatar

Mauritania

USA

Chad

Bahrain

Somalia

100

150

200

250

300

350

400

450

500

550

600

650

700

750

800

850

900

950

1000

Country

Metric tonnes 10

fig0005 Figure 5 World date-production figures (shown as histograms) for the 20 date-producing countries (figures for India not provided).

tbl0001Table 1 Diseases of the date palm

Agent Symptom/disease

Alternaria spp. Leaf spot

Alternaria citri Brown spot of fruit

Alternaria stemphylioides Fruit rot

Aspergillus niger Calyx end rot

Auerswaldia palmicola Leaf infection

Catenularia fuligenea Fruit rot

Ceratostomellara dicicola Root rot

Colletotrichum gloesporoides Leaf infection

Diplodia phoenicum Leaf stalk rot, fruit rot, and shoot

blight

Endoconidiophora paradoxa Black scorch and heart bud rot

Fusarium spp. Inflorescence blight and fruit rot

Graphiola phoenicis Leaf spot and false smut

Meliola furcata Black mildew

Meloidogyne spp. Root knot nematode

Omphalia pigmentata Decline disease

Omphalia tralucida Decline disease

Penicillium roseum Fruit rot

Pestalotia spp. Leaf spot

Phomopsis phoenicola Fruit rot

Phymatotrichum omnivorum Saprophytic contaminant on roots

Pleospora herbarum Fruit rot

Poria spp. Wood rot

DATE PALMS 1735