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

Подождите немного. Документ загружается.

animals except humans, other primates, guinea-pigs,

fruit bats, and some bird species are able to synthesize

ascorbic acid from glucose.

0008Aqueous solutions of vitamin C are stable unless

transition metal ions are present. Copper and iron

both catalyze the oxidation of ascorbic acid, utilizing

molecular oxygen, to produce hydrogen peroxide

and hydroxyl radicals (Fenton chemistry/Haber–

Weiss reaction).

Role in the Body

0009Vitamin C was first isolated in 1928. It is necessary for

the synthesis of the body’s cementing substances: bone

matrix, collagen, dentin, and cartilage, and is needed

as a cofactor for several enzymes. These enzymes

include proline and lysine hydroylases, which are in-

volved in the biosynthesis of collagen, and the copper-

dependent enzyme dopamine-b-hydroylase, which

converts dopamine into norepinephrine.

0010Deficiency of vitamin C results in scurvy, the symp-

toms of which are largely related to inadequate colla-

gen synthesis and defective formation of intercellular

materials due to reduced hydroxylation. Vitamin C

was identified as the curative agent for scurvy in

1932. The symptoms of scurvy are usually not seen

for 3–6 months in the absence of any dietary vitamin

C (< 1 mg per day) because vitamin C is metabolized

slowly in humans.

0011Smokers have an increased turnover of vitamin C,

which means that in order to maintain their body

pool and circulating levels at a concentration equal

to that of a nonsmoker, their intake should be about

80 mg per day, compared with the 40–60 mg required

by a healthy nonsmoker.

0012Vitamin C promotes uptake of nonheme iron by

reducing Fe(III) to Fe(II), and inhibits the activity of

nitroso compounds by maintaining them in their re-

duced inactive form. This ability to act as a reducing

agent (electron donor) may also be responsible for the

antioxidant role of vitamin C.

Antioxidant Role of Vitamin C

0013Oxygen-based reactive species are reduced by

donation of one electron from vitamin C/ascorbic

acid. During this process, the semidehydroascorbate

tbl0002 Table 2 Diseases involving reactive oxygen species and/or

free radicals

Primary single organinvolvement

Cardiovascular system

Atherosclerosis

Alcohol cardiomyopathy

Brain

Stroke/cerebrovascular/traumatic injury

Dementias and amyloid diseases

Demyelinating diseases

Ataxia-telangiectasia syndrome

Aluminum overload

Lung

Effects of cigarette smoking

Inhalation of oxidant pollutants

Emphysema

Hyperoxia

Acute respiratory distress syndrome

Pneumoconiosis

Skin

Solar radiation and photosensitivity

Thermal injury

Porphyria

Contact dermatitis

Eye

Cataractogenesis

Age-related macular degeneration

Degenerative retinal damage

Ocular hemorrhage

Retinopathy

Joint abnormalities

Rheumatoid arthritis

Gastrointestinal tract

Endotoxin liver injury

Carbon tetrachloride liver injury

Free fatty acid-induced pancreatitis

Nonsteroidal antiinflammatory drug-induced lesions,

abetalipoproteinemia

Kidney

Nephrotic membrane diseases

Aminoglycoside and heavy metal nephrotoxicity

Renal graft rejection

Erythrocytes

Lead poisoning

Protoporphyrin photooxidation

Malaria

Sickle-cell and other anemias

Multiorgan involvement

Cancer

Aging

Disorders of ‘premature aging’

Premature retinopathy

Immune deficiency

Inflammatory-immune injury

Glomerulonephritis (idiopathic, membranous)

Autoimmune diseases

Ischemia-reflow states

Drug and toxin-induced reactions

Iron overload

Idiopathic hemochromatosis

Dietary iron overload

Nutritional deficiencies

Keshan disease (selenium deficiency)

Kwashiorkor

Vitamin E deficiency

Alcohol damage

ROS and free radicals may be the sole cause of only a few but may make

some conditions worse or prevent the normal action of the body’s healing

processes.

284 ANTIOXIDANTS/Role of Antioxidant Nutrients in Defense Systems

radical is formed, which, despite being a free radical,

is not very reactive (Figure 1). Semidehydroascorbate

can undergo disproportionation to reform ascorbic

acid and dehydroascorbate. Alternatively, it may be

oxidized directly to form dehydroascorbate. Dehy-

droascorbate is highly unstable and breaks down,

via a series of complex reactions, to give oxalic and

l-threonic acids. Dehydroascorbate and its break-

down products are, however, toxic and the more

usual reaction is the conversion of dehydroascorbate

to ascorbic acid. This reaction is catalyzed by the

enzyme dehydroascorbate reductase and oxidizes

two glutathione molecules in the process. The same

enzyme may also recycle the semidehydroascorbate

radical. Both vitamin C and dehydroascorbic acid

play a pivotal role in protecting lipids against oxida-

tive damage by regenerating vitamin E.

0014 Vitamin C reacts rapidly with superoxide and

its derivatives, and even more quickly with hydroxyl

radicals. It also scavenges singlet oxygen, and re-

duces thiyl radicals and hypochlorous acid. The

human lens is rich in vitamin C, whereas levels of

naturally occurring antioxidant enzymes (e.g., super-

oxide dismutase) are low. It may, therefore, protect

the eye from oxidative damage, in particular the

damage caused by UV that is mediated by singlet

oxygen.

Prooxidant Potential?

0015Vitamin C has a potentially duplicitous action.

Hydrogen peroxide and hydroxyl radicals produced

during oxidation of vitamin C, catalyzed by transi-

tion metals, could be responsible for subsequent

oxidative damage to the cell and cellular components

including DNA.

0016The sequestration of metal ions in vivo by proteins

(e.g., transferrin – Table 3) means that the prooxidant

role of vitamin C is less likely. It is, however, not

impossible because the binding of the metal ions, by

the various proteins, does not render them entirely

inactive. Furthermore, in the event of physical damage

(e.g., bruising) heme iron may be released from eryth-

rocytes, which is available for participation in Fenton

chemistry. Oxidative damage caused by the vitamin C

in plasma may be a real danger to surrounding tissues.

Risk:Benefit

0017Megadoses of vitamin C, synthetic or natural, have

previously been considered beneficial or, at the very

least, harmless. However, there is mounting evidence

that doses as small as 500 mg per day may result in

increased levels of DNA damage and damage to the

lining of major arteries, which subsequently leads to

an elevated risk of stroke.

−

(a)

(b)

(c)

fig0001 Figure 1 (a) Structure of vitamin C; (b) dehydroascorbate radical; and (c) dehydroascorbic acid.

tbl0003 Table 3 Plasma proteins that bind metals or iron complexes

Protein (plasma concentration) Action

Ceruloplasmin (0.18–0.4 g l

1

) Ferroxidase activity

Inhibits iron and copper-dependent lipid peroxidation

Reincorporates iron mobilized from the iron storage protein ferritin back to ferritin

Does not react directly with peroxyl radicals

Transferrin (1.8–3.3 g l

1

) Binds iron and stops or slows down its participation in lipid peroxidation and iron-catalyzed

Haber–Weiss reactions

Can take up iron released from ferritin, thereby inhibiting ferritin-dependent lipid peroxidation

Lactoferrin (20010

6

1

) Action similar to that of transferrin

Albumin (50 g l

1

) Binds copper tightly and iron weakly

Haptoglobin (0.5–3.6 g l

1

) Binds free hemoglobin (Hb) and met-Hb, thereby preventing these proteins from catalyzing lipid

peroxidation

Transferrin and hemopexin do not inhibit Hb-mediated lipid peroxidation

Hemopexin (0.6–1.0 g l

1

) High affinity for heme (K

<10

13

mol l

1

)

Unlike transferrin and haptoglobin, hemopexin inhibits heme-mediated lipid peroxidation

ANTIOXIDANTS/Role of Antioxidant Nutrients in Defense Systems 285

Vitamin E

0018 There are no UK dietary reference values available for

vitamin E, but the US RDA is 30 IU. Vitamin E is the

major lipid-soluble antioxidant nutrient. Deficiency

symptoms are very rare, and usually only occur as a

result of fat malabsorption syndromes. Good food

sources include cereals, nuts and seeds, wheat germ,

vegetable oils, and ‘spreads,’ which contain vitamin E

as an antioxidant.

Chemistry

0019 Vitamin E (Figure 2) is an essential nutrient, which

happens to function as an antioxidant. The term

‘vitamin E’ is generic, and includes all entities that

exhibit the biological activity of a-tocopherol.

0020 In nature, eight substances have been found to have

vitamin E activity: a-, b-, g- and d-tocopherol, and a-,

b-, g- and d-tocotrienol. The acetate and succinate

derivatives of the natural tocopherols also have vita-

min E activity, as do the synthetic tocopherols and

their acetate and succinate derivatives. Of these, d-a-

tocopherol (RRR-a-tocopherol) has the highest bio-

availability and is the standard against which others

are compared.

0021 Natural and synthetic vitamin E are not equivalent

in composition, structure, or bioavailability. Natural

vitamin E (RRR-a-tocopherol or d-a-tocopherol) is a

single entity, whereas synthetic vitamin E (all-rac-a-

tocopherol or dl-a-tocopherol) is a mixture of eight

stereoisomers in equal amounts. The other seven

stereoisomers have different molecular configur-

ations and lower biological activities.

0022The richest natural sources of vitamin E are vege-

table oils, nuts, and whole grains. Wheatgerm oil is

the single richest source, whereas foods of animal

origin are generally low in vitamin E. In general, the

amount of vitamin E (as d-a-tocopherol) supplied by

a normal diet ranges from 6 to 13 mg per day (1 IU ¼

0.67 mg). In most countries, the estimated average

intake is below 10 mg per day. During refining, pro-

cessing, and storage, all foods containing vitamin E

lose some of their activity. Vitamin E in foods is

destroyed by oxygen, freezing causes degradation,

and, like vitamin C, the oxidative process is acceler-

ated by heat and light.

Role in the Body

0023Those compounds with vitamin E activity have a

number of roles in human metabolism that include

(1) acting as an antioxidant to protects cells and other

body components from free radical attack; (2) stimu-

lation of the immune response; (3) reducing the

severity of prostaglandin-mediated disorders such as

inflammation, premenstrual syndrome, and circula-

tory irregularities (nocturnal leg cramps and blood

platelet adhesion); (4) inhibition of the conversion

of nitrites in smoked, pickled, and cured foods to

nitrosamines in the stomach; and (5) regulation of

gene expression in particular the proliferation of

smooth muscle cells, which are involved in the

development of atherosclerosis.

0024Most vitamins function as cofactors for enzymatic

reactions, but vitamin E has no such role. Require-

ments for, and utilization of, vitamin E vary according

to an individual’s oxidative status. Furthermore,

unlike other vitamins, deficiency of vitamin E does

not produce a disease with rapidly developing symp-

toms. The absence of vitamin E only produces overt

deficiency symptoms in cases involving fat malab-

sorption syndromes, premature infants, and patients

on total parenteral nutrition. However, there are no-

ticeable effects of inadequate vitamin E intake, which

develop over a long time, typically decades, and

have been linked to the development of degenerative

diseases.

Antioxidant Role

0025Vitamin E is present in all lipids in the body, most

significantly in lipids of cell membranes and in circu-

lating low-density lipoproteins (LDL – the so-called

‘bad’ cholesterol). It is recognized to be the major fat-

soluble antioxidant in lipid tissue, and the primary

defense against lipid peroxidation – oxidation of fats.

Compound

Alpha (α)-tocopherol

Beta (β)-tocopherol

Gamma (γ)-tocopherol

Delta (δ)-tocopherol

Alpha (α)-tocotrienol

Beta (β)-tocotrienol

Gamma (γ)-tocotrienol

Delta (δ)-tocotrienol

fig0002 Figure 2 Tocopherols and tocotrienols.

286 ANTIOXIDANTS/Role of Antioxidant Nutrients in Defense Systems

When a free radical reacts with lipid in a cell mem-

brane, the resulting chain reactions oxidizing sur-

rounding lipid (lipid peroxidation) damage both the

structure and function of cell membranes. Vitamin E

is particularly important in tissues that contain rela-

tively high levels of polyunsaturated fatty acids (e.g.,

brain and central nervous system), those in direct

contact with high concentrations of oxygen (e.g.,

lung) and cell organelles dealing with oxygen or

oxygen-free-radical reactions (e.g., mitochondria).

Epidemiology

0026 Epidemiological studies provide data supporting the

benefits of higher intakes of foods containing vitamin

E as well as other antioxidants. These studies suggest

that individuals with low blood concentrations

and/or intakes of foods containing vitamin E have

increased risk for development of a number of degen-

erative diseases including certain types of cancer,

heart disease, Alzheimer’s disease, and cataract.

However, as yet, there is no proof that the vital com-

ponent in the prevention of these diseases is anymore

likely to be vitamin E than any of the other com-

pounds contained in such foods.

0027 A limited number of intervention trials have been

completed, with mixed results. However, for the most

part, such trials have used isolated natural or syn-

thetic vitamin E, and there is increasing evidence

that these compounds do not interact with the body

in the same way as food-sourced vitamin E (e.g.,

reduced bioavailability).

Source and Dose

0028 How much vitamin E an individual needs depends on

what is required; enough to prevent deficiency dis-

ease, prevent oxidation of lipids, prevent free radical

damage and promote optimal health, or to produce a

therapeutic effect. Deficiency per se can be prevented

by intakes in line with government recommended

dietary intakes. However, if prevention of oxidative

damage and promotion of optimal health is the ob-

jective, intakes of up to 10 times the current levels

have been proposed. If a therapeutic result is the aim,

even higher intakes may be necessary.

0029 Research data suggest that considerably more vita-

min E needs to be consumed in the average diet to

prevent free radical cell damage. Foods are depleted

of vitamin E by processing, refining, and storage, and

the current trend to reduce fat intake means that a

diet-conscious population tends to eliminate those

oil-rich foods likely to provide vitamin E. Not only

do most people not get enough vitamin E in their diets

for optimal health, but a large number are considered

to be marginally deficient of the amount necessary to

prevent deficiency disease.

Carotenoids

0030No dietary reference values are available for the

recommended daily allowance. Those with a b-

ionone ring are precursors for vitamin A.

0031No deficiency symptoms are known except those

associated with vitamin A deficiency. Good food

sources are colorful fruit and vegetables (e.g., peas,

tomatoes, and carrots) and commercial products such

as ‘spreads’ and milkshake flavoring, which contain

b-carotene as an antioxidant.

Links with Vitamin A

0032In 1913, it was shown that a fat-soluble factor in

butter – later characterized as vitamin A – stimulated

the growth of rats fed on an incomplete diet. Vitamin

A is a fat-soluble vitamin that helps in the formation

and maintenance of healthy teeth, skeletal and soft

tissue, mucous membranes, and skin. It is also known

as retinal because it generates the pigments that are

necessary for the functioning of the retina. However,

it is not an antioxidant.

Chemistry

0033Carotenoids are naturally occurring brightly colored

plant pigments. More than 600 different carotenoids

have been identified, all derived from the same basic

C40 isoprenoid skeleton (Figure 3).

0034Mixed carotenoids can be isolated from algae, b-

carotene from palm oil, lutein and lutein esters from

marigolds, lycopene from tomatoes, and crypto-

xanthin from citrus and tropical fruits, in particular

orange fruit. b-Carotene has been synthesized for a

number of years, and lycopene more recently.

0035Natural mixed carotenoid supplements contain a

variety of carotenoids, including a- and b-carotene.

Commercially available synthetic carotenoid supple-

ments contain only b-carotene. Synthetic b-carotene

is composed of the all-trans isomers, and b-carotene

from algae, and fruits, and vegetables is composed of

all-trans,9-cis, and other cis-isomers.

Role in the Body

0036Humans regularly consume around 40 different

carotenoids, but only a small number of these can

be detected in appreciable quantities in human

blood and tissues. The major carotenoids are a-and

b-carotene, lutein, zeaxanthin, cryptoxanthin, and

lycopene.

0037Provitamin A carotenoids, those carotenoids pos-

sessing a b-inone ring, have vitamin A activity, and

can be converted into vitamin A by the body. b-

Carotene has the highest provitamin A activity, but

over 60 carotenoids have some provitamin A activity.

Vitamin A is toxic when taken in excess, but these

ANTIOXIDANTS/Role of Antioxidant Nutrients in Defense Systems 287

carotenoids are safe sources because they are only

converted to vitamin A as and when the body needs

it. The other biological roles of carotenoids, including

their antioxidant functions, are completely independ-

ent of their provitamin A activity. However, the car-

otenoids are not recognized as essential nutrients, and

there are no recommended dietary intakes. The only

exception is a recommended dietary intake for

vitamin A of 800–1000 retinol equivalents, where

one retinol equivalent is 6 mg of b-carotene or

12 mg of another provitamin A-carotenoid.

Role of Antioxidants

0038 Despite the similarities in their structures, the

carotenoids have diverse biological functions and

potentially different roles within the body. The caro-

tenoids are effective quenchers of singlet oxygen,

with lycopene exhibiting the highest singlet oxygen-

quenching activity. They are able to function as chain-

breaking antioxidants, much like vitamin E, and may

protect cells and cellular components from oxidative

damage. The carotenoids will protect lipids from oxi-

dation as well but only in the absence of vitamin E,

which is far more abundant. Importantly, the carote-

noids exhibit the ability to inhibit oxidative damage

at different oxygen tensions. At high oxygen tensions,

such as those in the lungs, lycopene is more effective

then b-carotene, which in turn is more efficient at low

oxygen concentrations.

0039 Carotenoids enhance the immune response and

protect the skin from redness and damage following

exposure to UV radiation. Certain carotenoids (in-

cluding lycopene and b-carotene) have the ability to

enhance cell–cell communication by increasing the

exchange of growth regulatory signals. Increased

communication between normal cells and damaged

cells encourages the latter to undergo apoptosis

(commit suicide) and protects the body from prolifer-

ation of initiated potentially precancerous cells. Some

carotenoids are more effective in tumor suppression

in different cultured cell lines, and it has been sug-

gested that others protect against specific cancer

types. For example, increased consumption of toma-

toes and tomato products (lycopene) is correlated

significantly with a decrease in incidence of prostate

cancer and foods containing lutein, zeaxanthin, and

a-andb-carotene with a reduced risk of lung cancer.

Lutein and zeaxanthin are oxycarotenoids (i.e. they

contain an oxygen atom) and are the only carotenoids

present in the macular region of the retina. These

carotenoids are linked to the normal function of the

macula, which is responsible for sharp and detailed

vision, and are thought to serve as filters for harmful

blue light in the macula and as scavengers of singlet

oxygen in retinal tissues.

Epidemiology

0040The majority of data examining carotenoid intakes

show that individuals with low carotenoid intakes or

low blood carotenoid levels are at a greater risk of

developing degenerative diseases associated with

aging. High intakes of carotenoid-rich fruits and

AstaxanthinLycopene

Canthaxanthin

Zeaxanthin

Lutein

Cryptoxanthin

Aplha-carotene

Beta-carotene

Gamma-carotene

fig0003 Figure 3 Carotenoids and oxycarotenoids.

288 ANTIOXIDANTS/Role of Antioxidant Nutrients in Defense Systems

vegetables and high carotenoid blood levels are asso-

ciated with a lower risk of cancer and cardiovascular

disease, which may refute the previously held convic-

tion that only vitamin E had the potential to amelior-

ate risk. In addition, studies have shown an inverse

correlation between levels of the oxycarotenoids

lutein and zeaxanthin and risk of cataracts and age-

related macular degeneration, although there is no

evidence that increased intake can reverse existing

damage. For the most part, research into the carote-

noids has focused on b-carotene, because it is the best

known, most abundant, and has provitamin A activ-

ity, but recent studies have suggested that lutein,

zeaxanthin, lycopene, and cryptoxanthin should also

be considered.

Source and Dose

0041 Research suggests that 9-cis b-carotene is the most

efficient antioxidant and that food sources are better

able to increase antioxidant protection than natural

isolates. As with vitamin E, the amount of carote-

noids required by an individual will depend on the

overall aim (i.e., to prevent vitamin A deficiency,

prevent oxidation of lipids, prevent free radical

damage or promote optimal health). If prevention of

vitamin A deficiency is the objective, quantities of

provitamin A carotenoids to meet the RDA for vita-

min A are adequate for most individuals in developed

countries. If prevention of oxidative damage and

promotion of optimal health is the objective, higher

intakes of carotenoids may be necessary.

0042 The richest dietary sources of carotenoids are

brightly colored fruits and vegetables. Currently, the

estimated daily intake from a normal diet ranges from

1.5 to 3 mg for b-carotene and from 3.6 to 7.6 mg

for total carotenoids. Factors influencing carotenoid

intake levels include differences in varieties, variable

growth and harvesting conditions, postharvest hand-

ling and processing methods, exposure to light and

oxygen, and cooking methods. On the whole, mild

cooking of food before ingestion improves the bio-

availability of carotenoids, because the plant cell

wall structure is partially broken down, increasing

the ability of the gut to further digest the plant

material and release the carotenoids from the cel-

lular structures with which they are intimately

associated.

Risk:Benefit

0043 Results from intervention trials using a large dose of

synthetic b-carotene supplements over a long period

of time, often in combination with vitamin E, have

been neutral or negative, suggesting an increase in

both cancers and events related to cardiovascular

disease. In contrast, studies with other specific

carotenoids, mixed carotenoids, or foods with high

carotenoid contents have provided neutral or positive

results.

0044The carotenoids are not carcinogenic, mutagenic,

teratogenic, or cytotoxic when tested using typical

toxicological tests. Doses of 20–180 mg of b -carotene

per day, for many years, have been used to treat

erythropoietic protoporphyria, with no evidence of

toxicity or development of abnormally elevated

blood vitamin A levels. Based on current information,

therefore, an increased intake of a mixture of natural

carotenoids, preferably from food rather than in the

form of an isolate or b-carotene alone, may be of

greatest benefit in disease prevention.

See also: Antioxidants: Natural Antioxidants; Synthetic

Antioxidants; Synthetic Antioxidants, Characterization

and Analysis; Bioavailability of Nutrients; Cancer:

Epidemiology; Carotenoids: Occurrence, Properties, and

Determination; Cholecalciferol: Properties and

Determination; Cobalamins: Properties and

Determination; Nucleic Acids: Properties and

Determination; Physiology; Retinol: Properties and

Determination; Tannins and Polyphenols;

Tocopherols: Properties and Determination; Vitamin K:

Properties and Determination; Physiology

Further Reading

Block G, Patterson B and Subar A (1992) Fruit, vegetables

and cancer prevention: A review of the epidemiological

evidence. Nutrition and Cancer 18: 1–29.

Britton G, Liaaen-Jenson S and Pfander H (1995) Carote-

noids, vols. 1A, 1B & 2. Boston, MA: Birkhauser Verlag.

Frei B (1994) Natural Antioxidants in Human Health and

Disease. London: Academic Press.

Fund WCR (1997) Food, Nutrition and the Prevention

of Cancer: A Global Prospective. Washington, DC:

American Institute for Cancer Research.

Gutteridge JMC and Halliwell B (1995) Antioxidants

in Nutrition, Health and Disease. Oxford: Oxford

Academic Press.

Halliwell B and Gutteridge JMC (1999) Free Radicals in

Biology and Medicine, 3rd edn. Oxford: Clarendon

Press.

Institute of Medicine (2000) Dietary Reference Intakes for

Vitamin C, Vitamin E, Selenium, and Carotenoids: A

Report of the Panel on Dietary Antioxidants and

Related Compounds. London: Academic Press.

Sies H (1985) Oxidative stress. In: Sies H (ed.) Oxidative

Stress: Oxidants and Antioxidants, 1st edn. London:

Academic Press.

ANTIOXIDANTS/Role of Antioxidant Nutrients in Defense Systems 289

Appetite See Satiety and Appetite:TheRoleofSatietyinNutrition;Food,Nutrition,andAppetite

APPLES

L J Skog and C L Chu,UniversityofGuelph,Ontario,

Canada

Introduction

000 1 The apple belongs to the genus Malus, and is a

member of the rose family, Rosaceae. There are

about 25 species of Malus; however, most horticultur-

ists refer to Malus domestica as the cultivated apple.

This article discusses the global distribution, varieties,

commercial importance, morphology, nutritional

composition, handling, storage, and industrial uses

of this crop.

Origin and Global Distribution

000 2 The domestic apple of the west appears to have arisen

on the northern slopes of the Tien Shan range roughly

on the border of what is now Kazakhstan and the

Xinjiang province of China. This wild apple is called

M. sieversii. From this species, it seems, have emerged

the cultivated apples of our supermarkets, M. domes-

tica and M. pumila. Several crabapples and other

Malus species are considered native to China, India,

and North America. Although some species are not

hardy, the domestic apple (especially M. pumila)is

one of the hardiest of temperate-zone fruits. Apple

seeds require more than 60 days of cold temperature

before germination. In addition, its winter chilling

requirement for apple trees to break rest dormancy

(1000–1600 h) is high enough that it does poorly in

latitudes with warm winters. Apples are grown in

most temperate climates and many other countries

like Argentina, New Zealand, and South Africa.

Apples are also grown at the higher altitudes of

some countries with less temperate climates such as

Mexico. Production statistics for various areas of the

world are presented in Table 1.

Varieties

000 3 Variability in the wild species has been used by

breeders who use parents with desired traits when

crossesaremade. When seedsfromacrossare planted,

the resultant plant is a clone. Thus, breeders select

individual plants with desired characteristics rather

than selecting a population of plants.

0004The general objectives of apple-breeding programs

are as follows: (1) to enhance yields; (2) to improve

fruit quality, which includes factors such as flavor,

firmness, or other fruit characteristics; (3) to produce

plants adapted to specific environmental or cultural

conditions; (4) to develop varieties resistant to dis-

eases and insects; and (5) to develop varieties with

specific requirements, such as suitability for process-

ing, or extra firmness for long-distance shipping and

improved storage and shelf-life.

0005New apple varieties are continuously being intro-

duced: worldwide, there are more than 7000 varieties,

although most are not currently grown commercially.

Some of the more important varieties with their uses

are listed in Table 2. Apple characteristics vary

greatly with variety, and variety selection is a matter

tbl0001Table 1 Globaldistributionofappleproductionbygeographical

area,includingalistingofcountriesproducing1.010

metric

tonnes(Mt)ormore

Globaldistributionbygeographicalareaand

countrieswithinanyoneareaproducing

1.010

Mtormore

Production(Mt)

Worldtotal60831349

Africa1614736

North and Central America 5 794 038

USA 4 843 000

South America 3 292 391

Argentina 1 116 500

Brazil 1 160 475

Asia 33 591 517

China 22 887 600

India 1 580 000

Iran 2 200 000

Turkey 2 500 000

Europe 15 710 167

France 2 140 000

Germany 1 800 000

Italy 2 155 600

Poland 1 450 376

Russian Federation 1 200 000

Ukraine 1 325 000

Oceania (includes Australia and New Zealand) 828 500

Data from Food and Agriculture Organization of the United Nations (2000)

http://apps.fao.org.

290 APPLES

of personal preference and intended use. In general,

for fresh eating or dessert apples, North Americans

prefer mildly sweet, crisp apples, Europeans favor

tarter apples with high flavor and firmness, and

Asians and people of the Middle East select very

sweet apples. Some Japanese growers will leave

apples on the tree until the apples become extremely

sweet with an almost syrupy center (known as ‘water

core’). These apples would be considered overripe

and unsaleable in most European and North Ameri-

can markets.

0006 In North America, six varieties account for the

majority of the crop. In the USA, Red delicious,

Golden delicious and Granny Smith account for

65% of the apples grown. In Canada, McIntosh is

the most popular, followed by Red delicious and

Spartan. In both countries Gala and Fuji are being

increasingly planted in response to higher world

prices for new apple varieties.

0007 Golden delicious is the number-one variety in

Europe, with many clones being selected from this

parent, although plantings are decreasing. Red deli-

cious is popular, but some areas in Europe have diffi-

culty growing it due to susceptibility to frost and

physiological storage diseases and it too is experien-

cing decreased plantings. Granny Smith is very popu-

lar and increasing slightly in demand. Rome beauty

and Cox’s orange were quite popular but plantings

are now in decline. In Belgium, Germany, and the

Netherlands, Jonagold is the most popular variety.

Gala is increasing in demand in Europe, as in North

America. In 8 years, production of Gala increased by

1200% in the European Union (EU). Braeburn, which

is the most popular variety in New Zealand, its coun-

try of origin, is also the favorite variety in the UK and

Germany. World demand for Fuji has encouraged

increased plantings, although there are difficulties

finding suitable growing conditions. In China, ap-

proximately 40% of the crop consists of the cultivar

Fuji.

Commercial Importance

0008The Food and Agriculture Organization lists apple

production statistics for 88 countries. Thirteen coun-

tries – USA, Argentina, Brazil, China, India, Iran,

Turkey, France, Germany, Italy, Poland, the Russian

Federation, and the Ukraine – each produce in excess

of 1 million metric tonnes (Mt) annually. China is by

far the world’s largest producer of apples, accounting

for more than 50% of the world’s 6.0 10

annual production (Table 1). This worldwide produc-

tion would have a farm-gate value of over $3.0 10

(US) based on their value in North America. This

return would represent $0.50 kg

1

average price for

fresh-market fruit. Return varies greatly with variety

depending upon demand and availability. In North

America, per capita consumption averages 10 kg for

fresh consumption, with an additional 12 kg for pro-

cessed products (including juice).

tbl0002 Table 2 Selected apple varieties and their characteristics and uses

Variety Flavor Storage life Uses Remarks

Braeburn Sweet Excellent Cooking, fresh

Cortland Slightly tart Good Cooking, fresh White flesh that is slow to darken when cut

Cox’s orange Slightly tart Good Cooking, fresh Orange/red; yellow flesh

Empire Sweet/slightly tart Good Fresh

Fuji Sweet Good Cooking, fresh

Gala Slightly sweet Short Cooking, fresh Orange/red; yellow flesh

Golden delicious Sweet Excellent Cooking, fresh

Granny Smith Sweet/tart Excellent Cooking, fresh

Haralson Tart Excellent Cooking, fresh White, firm flesh

Honeygold Slightly sweet Good Cooking, fresh

Idared Slightly sweet Good Cooking, fresh

Jonadel Slightly sweet Good Cooking, fresh Red fruit

Jonafree Slightly tart Good Cooking, fresh

Jonagold Slightly tart Good Cooking, fresh Large yellow fruit with red striping

Jonathan Slightly tart Moderate Cooking, fresh

Liberty Slightly tart Good Fresh Greenish yellow with red stripes

McIntosh Slightly tart Moderate Cooking, fresh Bright red

Mutsu Slightly tart Excellent Cooking, fresh Yellow-green fruit

Northern spy Tart Excellent Cooking

Paulared Slightly tart Short Fresh

Red delicious Sweet Excellent Cooking, fresh

Rome beauty Slightly tart Good Cooking

Spartan Slightly tart Good Cooking, fresh

Primary source: Naeve L (1997). Apple varieties and their uses. Horticulture and Home Pest News IC-477(23): 138–139.

APPLES 291

0009 In China, much of the best quality Fuji is destined

for East Asian markets. In the last 10 years, apple

production in China has quadrupled and is expected

to double again in the next few years. Approximately

2.5  10

ha of land is devoted to apple production,

compared to 3  10

ha for all of North and Central

America. Ten percent of the crop will be processed.

Several other Asian countries also produce large

quantities; however, distribution is primarily limited

to internal markets. Storage facilities are also limited

in some Asian countries.

0010 Central and Eastern Europe contains about 83% of

Europe’s total land mass but produces less than 50%

of its apples. Climate and economic conditions vary

greatly throughout this area, resulting in a wide vari-

ation of quality, production, and return. Newer var-

ieties are not available in most areas. Returns also

vary greatly, ranging from 100 to 150% higher than

production costs in countries with extensive cultiva-

tion, down to 20–40% in less developed countries.

Poland, Slovenia, and Hungary produce sufficient

crop to permit export. Storage facilities are limited

in most countries with only 20–30% of the fruit

stored. Storage is often in natural storages as some

lack cold and controlled atmosphere (CA) storages.

0011 Apple production in western Europe has been at a

surplus for some time. In 1997, almost 50% of apples

in storage were unsold as of 1 December. Changing

popularity of varieties and increased imports have

partially accounted for this surplus. The EU has

been directing orchard removals. Orchard removal

has been particularly evident in France, which has

accounted for 30% of European orchard removals.

0012 Apples are a major fruit crop in North America,

although returns are low for some of the traditional

varieties and growers are shifting to the more lucra-

tive varieties. Production in North America is concen-

trated in three main areas: (1) the eastern section,

including the north-eastern and Atlantic states and

provinces; (2) the central USA (Ohio to Arkansas);

and (3) the western section from Colorado to British

Colombia.

Morphology

001 3 The apple is a pome fruit which develops from the

inferior ovary of the flower. Specifically, it develops

from the ovary wall and the floral tube (the base parts

of the stamens, sepals, and petals). During matur-

ation, the tube fuses to the ovary wall, expands, be-

comes fleshy and ripens. The fleshy mesocarp is the

edible portion of the fruit. Five cavities are also pro-

duced which generally contain two seeds each.

0014 Apples differ greatly in their external characteris-

tics. When ripe, they may be green, yellow, or red

depending upon variety. Size, shape, sugar content,

acidity, and firmness all vary with variety. Apples may

be classified into three categories depending upon the

concentration of acid (calculated as malic acid)

and phenolic compounds or tannins. Bitter-sweet

apples contain greater than 0.2% (w/v) tannins and

less than 0.45% (w/v) acidity. Sharp apples have less

than 0.2% tannins and more than 0.45% acidity.

Sweet apples have less than 0.2% tannins and less

than 0.45% acid.

0015The physiological characteristics of apples, such as

the waxy skin and low respiration rate (5–10 mg

/kg h

1

at 5



C), make them very suitable for

storage and long-distance shipping, thus apples are

harvested once a year but available year-round.

Chemical and Nutritional Composition

0016A list of some of the nutrients in apples is presented in

Table 3, with those for strawberries and oranges in-

cluded for comparison. Apples contain the highest

percentage of carbohydrates and food energy of

these three fruits. A serving of one 150-g apple pro-

vides 8% of the US Department of Agriculture adult

daily requirement for ascorbic acid (vitamin C) and

2% of both the vitamin A and iron requirements.

Refer to individual nutrients.

0017Apples contain virtually no fat, cholesterol, or

sodium. Apples are rich in pectins (soluble fiber)

which has been found to be effective in lowering

cholesterol levels. Apples also contain phenolic anti-

oxidants and flavonoids (especially quercetin) which

may also provide health benefits. (See Antioxidants:

Natural Antioxidants; Synthetic Antioxidants; Syn-

thetic Antioxidants, Characterization and Analysis;

tbl0003Table 3 Nutrient composition (per 100 g fresh weight) of apples

compared to that of strawberries and oranges

Nutrients andunits Apple Strawberry Orange

Water (g) 83.93 91.57 86.75

Food energy (kcal) 59 30 47

Food energy (kJ) 247 126 197

Protein (g) 0.19 0.61 0.94

Total lipid (g) 0.36 0.37 0.12

Cholesterol (mg) 0 0 0

Carbohydrate (g) 15.25 7.02 11.75

Fiber (total dietary) (g) 2.7 2.3 2.4

Calcium (mg) 7 14 40

Magnesium (mg) 5 10 10

Phosphorus (mg) 7 19 14

Potassium (mg) 115 166 181

Ascorbic acid (mg) 5.7 56.7 53.2

Folate (mg) 3 18 30

Vitamin A (mg retinol) 5 3 21

Data from United States Department of Agriculture Nutrient Database

(2001)http://www.nal.usda.gov/fnic/foodcomp.

292 APPLES

Role of Antioxidant Nutrients in Defense Systems;

Pectin: Properties and Determination; Food Use.)

Handling and Storage

0018 Apples in the northern hemisphere are harvested

in the months of August, September, and October.

Early varieties usually have a shorter shelf-life than

late varieties. Apples are harvested by hand using

a lifting and twisting motion to separate the fruit

stem from the branch. An apple picker needs to

handle the fruit gently to reduce the incidence

of bruising on the fruit. Pickers usually carry a

harvesting bag to hold the apples while they are

walking through the orchard. The bag must be suit-

able for local conditions and ease of use and not

damage the fruit. Often, the bag can be opened at

the bottom in order to release apples easily into an

orchard bin.

0019 An orchard bin can usually hold approximately

700 l of apples. The size of wood bins is approxi-

mately 120 102 74 cm and that of plastic bins is

approximately 122 113 88 cm. The advantage of

using plastic orchard bins is the cleanliness, the faster

cooling time, and the ease of fixing damaged bins,

which can be simply melted down and reformed. The

initial cost of a plastic orchard bin may be higher than

the wood orchard bin, but the longer usage life of a

plastic bin makes it a more attractive investment for a

long-term commercial operation. These orchard bins

can be stacked up to eight bins high for the plastic

bins and nine bins high for the wood bins when

placed inside a cold storage room. Bins need to be

stacked closely together in order to force the cold air

to pass through the apples.

0020 Most apples can be stored at 0



C. Some varieties of

apples need to be stored at slightly higher tempera-

tures in order to reduce the occurrence of disorders

associated with chilling injury. For example, McIn-

tosh apples have to be stored at 2.5–3



C to avoid

brown core disorder. Normally apples can be stored

in cold storage for 3–6 months. The length of the

storage life of apples depends on apple variety, stor-

age temperature, harvest date, and storage atmos-

phere. The storage life of apples can be doubled if

the apples are stored in CA storage rooms. Oxygen

levels in a CA room are maintained at 1–3% and

carbon dioxide levels are maintained at 1–5%. A

CA room is basically an airtight cold storage room.

The pressure in the CA storage room needs to be

slightly higher than the atmosphere outside to prevent

outside air from seeping into the room. The levels of

oxygen can be reduced by burning methane or pro-

pane gas or by adding nitrogen gas to the CA room.

Combusting oxygen with methane or propane can

remove unwanted oxygen and produce the desired

carbon dioxide. Nitrogen gas can be provided from

a bulk tank of nitrogen gas or by a hollow-fiber

membrane separation system. The principle of

hollow-fiber membrane air separation is based on

varying permeation rates for different gases, such as

oxygen, carbon dioxide, and nitrogen, through the

membrane.

0021The hollow-fiber membrane-type gas separator

consists of bundles of small hollow polymeric fiber

tubes in a vessel. Compressed air is fed into the separ-

ator, pressurizing the inside of the individual tubes. As

the air flows through the tubes, oxygen and carbon

dioxide permeate through the fiber walls faster than

the nitrogen. This oxygen-rich stream is vented to the

outside. The nonpermeate gas (nitrogen) outflow

stream is piped into the storage room. By changing

the output flow rate, the purity of the output can be

controlled. Nitrogen purity levels of up to 99.9% can

be obtained, but for CA applications purity levels of

97–99% are usually used.

0022The level of carbon dioxide in a CA room can also

be achieved by the natural respiration of the fruit.

When the level of carbon dioxide reaches 1–5%,

excessive amounts of carbon dioxide have to be re-

moved by absorbing carbon dioxide with lime or by

adding nitrogen gas to the CA room.

0023Table 4 shows a summary of recommended storage

temperature, levels of oxygen and carbon dioxide,

and storage life of apples in CA storage for major

apple cultivars in the world. Special care must be

exercised when entering a CA storage room because

the level of oxygen in a CA room is not enough to

support human life. (See Chilled Storage: Principles;

Attainment of Chilled Conditions; Quality and Eco-

nomic Considerations; Microbiological Consider-

ations; Use of Modified-atmosphere Packaging;

Chill Foods: Effect of Modified-atmosphere Pack-

aging on Food Quality; Chilled Storage: Packaging

Under Vacuum; Controlled-atmosphere Storage: Ap-

plications for Bulk Storage of Foodstuffs; Effects on

Fruit and Vegetables; Ripening of Fruit.)

Industrial Uses

0024In most countries, a high percentage of the apple crop

is used for processing. In the USA, statistics indicate

that, in 1997, 50% of fruit was eaten fresh, 20% was

processed into vinegar, cider (fresh or fermented),

wine, juice, jelly or apple butter, 17% was canned as

apple sauce, baby food, or pie filling, and the remain-

der was exported to other countries (predominantly

for the fresh market). Cider (fermented), wine and

brandy production are particularly important uses in

Europe. (See Cider (Cyder; Hard Cider): The Product

APPLES 293