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

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Further Reading

Charley H (1982) Food Science, 2nd edn, pp. 243–255.

New York: John Wiley.

Daniel AR (1963) Baking Materials and Methods, 4th edn,

pp. 362–391. Essex: Elsevier Science.

Goodsell GR (1985) Making Danish – basics that determine

quality results. Bakers Digest 59(3): 16–21.

Loving HJ and Brenneis LJ (1981) Soft wheat uses in the

United States. In: Yamazaki WT and Greenwood CT

(eds) Soft Wheat: Production, Breeding, Milling and

Uses, pp. 169–207. St Paul, Minnesota: American Asso-

ciation of Cereal Chemists.

Pyler EJ (1988) Baking Science and Technology, vol. II,

pp. 1107–1183. Meriam, Kansas: Sosland.

Rijkaart C (1984) Producing the perfect pastry. Food

Manufacture 59(7): 29–31.

Rijkaart C (1984) Producing the perfect pastry. Food

Manufacture 59(8): 46–47.

Sultan WJ (1990) Practical Baking, 5th edn, pp. 217–328,

379–423, 425–485. New York: Van Nostrand Reinhold.

Pathogens See Emerging Foodborne Enteric Pathogens; Food Poisoning: Classification; Tracing

Origins and Testing; Statistics; Economic Implications; Microbiology: Classification of Microorganisms

PEACHES AND NECTARINES

C Blattny

, Prague, Czech Republic

Introduction

0001 Both peaches and nectarines originated from the

same tree – the peach, whose botanical name is Pru-

nus persica L. (rose family – Rosaceae). They are

a typical stone fruit with the seed in a hard stone;

soft pulpy flesh surrounds the stone and the surface

is covered with a relatively thin skin. The peach

and nectarine are closely related to other species

of the genus Prunus: apricot, almond, plum, and

cherry.

Origin and History

0002 The peach is a native of China, where it was depicted

in old paintings and mentioned in Chinese mythology

and folklore as far back as the tenth century bc. The

peach signifies long life and peach blossom has also

been important in China for a very long time. There

semiwild forms can be found in all native peach areas

from south to north-west and north-east.

0003 It is unclear how peach and nectarines spread to

Europe. At least two or three ways are probable.

First, when the Romans occupied Syria to the end of

the first century bc and found the peach, they named

it ‘Persian apple.’ It must have been important that

peaches grow quickly from seed, and this permitted

their rapid dispersal from China to the west. The

second way was probably across Egypt to Rhodes

and the third route was over Greece and the Balkans.

Since the beginning of the second millennium peach

and nectarines spread throughout Europe, especially

in the south and south-east. France played an import-

ant role in the development of the peach – at the

beginning of the seventeenth century about 30 culti-

vars of peach were grown there. During the following

two centuries this number reached more than 350

cultivars. Also in Italy interest in peach and nectarine

increased from century to century. Much archeo-

logical evidence of peach seeds has been found there

along the central Donau in Hungary and Slovak

republic. The Spaniards brought peaches to America

(Mexico and Florida) in the sixteenth century.

Peaches spread in America very quickly and, espe-

cially in California, the peach became the leading

fruit grown in orchards.

Requirements of the Peach Tree

0004Peaches have different requirements according to

their old native district. The hardiness, early or late

blooming, and requirement of winter cold exposure

(chilling) are most important. Most older cultivars

need more than 950 h at around 6



C. However it

should also be emphasized that the peach tree is a

warmth-seeking botanical species. It needs higher

PEACHES AND NECTARINES 4415

temperatures in summer with strong intensive sun-

shine and relatively mild frost in winter – attributes

of a mild climate. However, cultivars from south

China are suitable for subtropical regions as they

need less chilling.

0005 The peach has very similar requirements for envir-

onmental conditions as the vine. The soil for peach

should be warm, not too heavy, airy, pH 6–7.5, and

CaCO

3–5%. Selection of the rootstock for given

conditions is important. The following seedlings are

used in various countries: peach seedling (various

types), peach almond hybrids, almond seedlings,

plums seedlings, Prunus davidiana (China), and

peach P. davidiana hybrids. Peach seedlings prevail:

in some countries peach almond are very often

used.

0006 Nectarine cultivars have greater environmental

demands. They need warmer summers (without

rain), as the fruit’s skin tends to crack after rain.

The Fruit

0007 Peach is one of the most variable of all tree fruit

species. From the pomological point of view, the

cultivars are divided into five groups:

0008 True peaches – freestone or semifreestone with

fuzzy skin

0009 Clings – clingstone with fuzzy skin

0010 Nectarines (smooth-skin peaches) – with fuzz-free

skin and freestone

0011 Brugnons – small clingstone nectarines

0012 Peento – a special group of peaches with flat fruit

(almost like dried figs) and exposed stone

0013 This division is by no means accurate. It is neces-

sary to emphasize that in some years when there is a

cold and rainy summer, a stronger fusion of flesh and

stone also occurs with freestone cultivars.

0014 Cultivars of peach and nectarine differ in their

height, width, and thickness. Both peaches and nec-

tarines are round or oval-round, oval, oblong, or

somewhat flat. The suture leading from the stem pit

to the top of the fruit or behind it is a typical feature.

The depth of the suture also differs between cultivars.

Some have a small tip on the top, some have deeper

ones, and a small number of cultivars have a small

knoll (like Venus). The skin of true peaches and clings

is fuzzy. This fuzz differs according to the cultivars –

sometimes it is very fine, sometimes it is dense and

very fuzzy. The skin is orange-yellow, white with red

cheeks, or red with stripes, or plain red. The flesh is

soft, sometimes too firm or too fibrous, yellow,

orange-yellow, nearly white, green-white, or red. In

old-type cultivars, which have only been selected to

a limited degree, the flesh is often farinaceous. The

color of flesh around the stone and under the skin is

slightly darker and sometimes red.

0015Nectarines usually have a somewhat smaller fruit

and a smooth shiny skin (like plums); the flesh is

harder, more like a plum, and not melting like true

peaches. The taste differs slightly from true peaches;

however it is outstanding too. Greater consumer ac-

ceptance is attained of the fruit of nectarines which

are more acidic than peaches. The color of the skin is

often red to purple-red. In recent years an important

development of white-flesh nectarine cultivars has

occurred.

0016The stones of peaches and nectarines are conspicu-

ous by their surface, with different deep branch-like

grooves and pits. These characteristic shape, size,

grooves, and color of the stone are peculiar to every

single cultivar.

Regulations

0017Commission regulation (EC) no. 2335/1999 lays

down marketing standards for peaches and nectar-

ines.

Definition of Produce

0018This standard applies to peaches and nectarines

grown from cultivars of Prunus persica L., to be

supplied fresh to the consumer; peaches and nectar-

ines for industrial processing are excluded.

Provisions Concerning Quality

0019The purpose of this standard is to define the quality

requirements for peaches and nectarines after prepar-

ation and packing.

0020Minimum requirements Peaches and nectarines

must be:

intact, sound, produce affected by rotting or deterior-

ation such as to make it unfit for consumption is

excluded, clean, practically free of any visible foreign

matter, practically free from pests, practically free from

damage caused by pests, free of all abnormal external

moisture, free of foreign smell and/or taste

Peaches and nectarines must have been carefully

hand-picked. The development and ripeness of

peaches and nectarines must be such as to enable

them to withstand transport and handling and to

arrive in a satisfactory condition at the place of

destination.

0021Classification

0021Extra class

0022Class I

0023Class II

4416 PEACHES AND NECTARINES

Provisions Concerning Sizing

0024 Sizing is determined by circumference or maximum

diameter of the equatorial section (Table 1).

Diseases

0025 Peaches and nectarines are subject to attack by a

cosiderable number of diseases. Viruses and Myco-

plasma are the most significant. We will discuss only a

few diseases here

0026 Peach mosaic (vector – eriophyoid mite Eriophyes

insidiosus)

0027 Peach yellows and little peach (vector – leafhopper

Macropsis trimaculata)

0028 Phony (distributed through the root system)

0029 X-disease (vectors – more species of the leaf-

hoppers)

These diseases have various symptoms on the leaves,

twigs, and fruits. All these diseases are transmitted

with buds by propagation, therefore healthy bud-

wood and rootstocks are the most important control

measures (together with the fight against vectors).

Affected trees have nearly no crop and usually die

within a short period.

0030 The fungus diseases leaf curl, brown rot, and

mildew are troublesome:

0031 Leaf curl (Taphrina deformans) curls and deforms

the leaves early in the season; their color changes to

dark red or violet. It must be prevented by applying

fungicides just before bud opening.

0032 Peach mildew (Sphaeroteca pannosa) appears in

the form of a white powdery substance upon the

leaves and fruits. Spraying with fungicides will

commonly hold it in check.

0033 Brown rot (Monilia fructicola). Infection begins

during flowering but fruit rot often occurs after

harvest. Control with fungicide during vegetation

and then immediate cooling after harvest are

important.

0034 Gray mold (Bothrytis cinerea) occurs especially

after a wet spring during storage if the fruit has

been infected during gathering. Gentle harvest,

undamaged fruit, and temperature about 0



during storage and transport are effective control

measures.

Harvesting of Fruit

0035In the 1930s the harvesting season of peaches was

about 3 weeks – mid-July to mid-August. Due to

intensive breeding work, especially in the USA (and

in France and Italy), the harvesting season is now

extended to at least 2 months; in the most favorable

environmental conditions it may be more than 3

months (mid-May to 3 September). As regards

ripening, the cultivar Redhaven grown worldwide is

taken as the reference. Most peach cultivars ripen in

the midseason 2–3 weeks after Redhaven; more nec-

tarine cultivars ripen before Redhaven; the canning

clingstone cultivars have a shorter harvesting period

before and 6 weeks after Redhaven.

0036The harvest differs according to the purpose of

using the fruit. For fresh fruit the fruit has to be

harvested 2–3 days before it will reach ripeness,

with a fully developed flavor. This is called tree-ripe.

Therefore it is sometimes recommended to repeat

harvesting at least three times according to advancing

ripeness. The grade of ripeness can be determined by

skin ground color changes from green to yellow in

most cultivars (exept for the white-flesh cultivar).

This is called minimum maturity, and is used to har-

vest fruits determined for distant markets and long

transport. The ideal time to harvest peaches is when

they are beginning their ripening process, but are still

firm. At this stage they withstand picking operations

and hauling quite well and complete the ripening

process in good condition. If picked too soon, poten-

tial tonnage is lost because peaches and nectarines

grow considerably just before reaching maturity. If

the harvest delay is too long, they begin to soften,

bruise easily, and shelf-life is reduced. To satisfy con-

sumers that the fruit is ready to eat it is necessary to

initiate the ripening process at the right time before

the fruit is put on the market. Nowadays detailed

ripening protocols for different peach and nectarine

cultivars from important international export dis-

tricts have been developed. For home gardens usually

the best time is when the yellow-fleshed cultivars

change from yellowish-green to yellow or orange-

yellow. White-fleshed cultivars are ready for harvest

when the color changes to cream white.

0037The nearly ripe fruits of the best quality should be

gathered and placed in the market boxes that are

provided with special niches for each individual fruit

to prevent bruising during transport. Rapid transport

should take place in refrigerated trucks.

tbl0001 Table 1 Classification of peaches and nectarines according to

size

Diameter Size (code) Circumference

90 mm and over AAAA 28 cm and over

80 mm – under 90 mm AAA 25 cm under 28 cm

73 mm – under 80 mm AA 23 cm under 25 cm

67 mm – under 73 mm A 21 cm under 23 cm

61 mm – under 67 mm B 19 cm under 21 cm

56 mm – under 61 mm C 17.5 cm under 19 cm

51 mm – under 56 mm D 16 cm under 17.5 cm

PEACHES AND NECTARINES 4417

0038 Cultivars destined for processing are usually picked

all at once – true peaches by hand and clings with the

help of fruit-shaking machines.

Postharvest Operations

0039 Peaches and nectarines are transported from orchard

to packinghouse and cooler as soon as possible after

harvest. In the packinghouse the fruits of minimum

maturity are sorted to eliminate fruits with visual

defects, and to select outstanding nice colored and

big fruits (for the extra class). Cleaning machinery

to remove fuzz from peaches is often used in all

major production areas. In the defuzzing operation

the peaches are scrubbed with rotating brushes to

remove the fuzz and then washed and rinsed with

fresh cold water. Sizing segregates fruits by size or

weight. It is very important to cool the fruit as quickly

as possible to near 0



C. Also longer chilling at 0



Cis

recommend. When the fruits are stored at a higher

temperature, between about 2.2



C and 7.5



chilling injury (internal breakdown) occurs. First the

flavor is lost, then the flesh becomes mealy, wooly, or

harder, and brown around the pit of the stone. Culti-

vars of peach and nectarine differ in their suscepti-

bility to chilling injury; nectarines are less susceptible.

0040 Sometimes during harvest or after 1–2 days, black

spots or stripes occur on the skin. This is a result of

abrasion combined with touch with metal – iron

or copper. Therefore it is very important to handle

fruit gently during harvest and postharvest hauling

operations.

Supplying Fresh Fruit to Consumers

0041 The fruits must be intact, sound, clean, practically

free of any visible foreign matter, practically free

from pests, free of abnormal external moisture and

free of any foreign smell or taste. The fruits must have

been carefully picked and sufficiently developed that

the ripening process can continue in order to reach

the degree of maturity proper to their cultivar char-

acteristic, to withstand transport and handling, and

to arrive at their destinations in satisfactory condi-

tions. Usually they are classified to four or seven

classes according to the diameter of the widest part

of the peach and nectarine.

Use of fresh fruits

0042 Peaches – and, to a certain extent, nectarines – belong

to the most sought-after fruits, thanks to their deli-

cious taste and the development of global trade. Most

of the peach crop (usually about 60%; in some

regions much more) is marketed as fresh fruit; for

nectarines, nearly all of the crop is used fresh. Culti-

vars of true freestone peaches with white and orange-

yellow melting flesh, thin skin with not too dense

fuzz, and delicious taste, fully ripened are the best

for eating fresh. On the market such cultivars are

sold in four to five classes. Sliced fresh peaches or

nectarines are eaten alone or in combination with

other fruit in salads or cocktails. Canned or frozen

fruit can be used in the same way. Dried fruits are

usually eaten as an energy-giving snack. In homes and

confectioneries peaches and nectarines can be used

for baked goods, icecream, gelatine desserts, pies,

juices, and sherbets.

0043Some sensitive individuals can experience difficul-

ties caused by a thicker fuzzy skin of certain peach

cultivars. This unpleasant characteristic can be solved

by a defuzzing operation (with rotating brushes) or by

developing large nectarines, as was done in the last

decades, especially in the USA.

Processing

0044The main method of processing is canning, usually

about 30% of the whole crop, while a small amount

is dried in some regions. The fruits are further used

for jams, jellies, juices, brandy and liqueurs, pre-

serves, and other miscellaneous products.

Technological Requirements

0045Peaches are inspected, graded, halved, pitted, and

peeled before canning, freezing, and drying. The

shape of the fruit should be round or flattened

round and almost uniform; the diameter should be

at least 45 mm. The flesh should be soft but firm

enough (not farinaceous), of yellow-orange color,

and have a taste full of the aroma. The smaller the

stones, the better – 8–9% of total fruit weight. Tannin

content should not be more than 0.08%. True

peaches and clings are used in the processing industry.

Cling cultivars are better, as they have firm flesh from

the skin to the stone. Therefore after pitting and

peeling the flesh is equally firm and does not crumble.

The cling cultivars withstand better mechanical

harvesting with shaking machines, longer transport,

and storage. A further advantage of clings is equal

ripening and slower overripening than true peaches.

For processing the optimal grade of ripeness has to be

measured just before processing starts. Prematurely

harvested and processed fruit is too hard and lacks

intense taste and flavor. Peaches are usually canned in

light to heavy syrup, less so in water or juicy pack.

When freezing the syrup, a small amount of ascorbic

acid (to prevent browning) is used. Peeled peaches

must be sulfured for drying.

4418 PEACHES AND NECTARINES

Recommended Cultivars

0046 Nowadays grown cultivars have different origins. In

earlier times cultivars from the Persian (Iran) region

were a base for many old cultivars. But in the middle

of the nineteenth century some Chinese clings were

imported to America directly from China. Some from

North China (with hard winters) required high

chilling and some from South China required less

chilling. From these Chinese imports accidental

hybrids with cultivars grown in that time in the USA

have been chosen. One such hybrid was introduced in

the 1870s as the cultivar Elberta. It had become one

of the most widespread cultivars in a short time and a

parent of many new cultivars.

0047 Some examples of worldwide cultivars (2000 ad)

are:

0048 true peaches – freestone and semifreestone –

yellow: Redhaven, O’Henry, Spring Lady, Rich

Lady, Cresthaven, Maycrest, Springcrest, Elegant

Lady, Royal Glory, Fayette; white: Maria Bianca,

White Lady

0049 clingstones: Babygold 5, 7, Vivian, Harbinger,

Andross, Loadel, Helford 2, Golden Queen

0050 nectarines – yellow: Redgold, Fantasia, Flamekist,

Supercrimson, Venus, Armking, May Grand,

Marycrest; white – Queen Giant, Silverking.

0051 In many districts these has been a shift from middle

and late cultivars to early-maturing ones. This

resulted from the strong demand for the first peaches

and nectarines harvested. This is reflected in the high

prices of early peaches and nectarines. In recent years

there has been an improvement in the size and color

of early peach and nectarine cultivars. Many have

firm, white flesh with a delicious flavor and taste. In

the typical great peach district a peach cultivar now

usually lasts less than 20 years before being replaced

by new superior one. Elberta’s (1870) longevity is a

distinguishing feature. North American cultivars

became popular in European districts (Italy, France,

Spain, Hungary, and Yugoslavia) and also in South

America and North Africa. New cultivars were

selected that required less chilling in the USA around

the year 1970. This allowed an important increase in

peach growing in very warm regions – India, Peru,

Thailand, Brasil, Israel, not just in the USA. In the last

decade many new cultivars have been developed in all

main peach- and nectarine-growing regions – for in-

stance, in the USA about 250, France about 55, Italy

about 90, China about 35, Mexico about 20, and in

the whole world more than 500 new cultivars.

Nutritional Value

0052The composition of peaches and nectarines is given in

Tables 2, 3 and 4. When ripe, most modern cultivars

of peaches and nectarines exhibit a well-balanced

proportion of acids and sugars. The content of dietary

fiber and mineral salts, principally potassium, is

important. Vitamin content is relatively low. It is

influenced by the cultivar, how it is grown, the envir-

onment, and ripeness grade. There is also a rich con-

tent of delicious aromatic substances present. All this

contributes to the great popularity of peaches and

nectarines.

Production

0053Worldwide production of peaches and nectarines is

increasing. This trend is mainly based on a large

tbl0002 Table 2 Chemical composition of peaches and nectarines

gkg

1

Water 805.0–877.0

Protein 7.0–8.0

Total lipid 0.9–2.0

Sugar 70.0–150.0

Acids 6.0–12.0

Dietary fiber 14.0–20.0

Ash 4.0–5.0

Sugar is composed on average from 13% glucose, 15% fructose, and 72%

saccharose. Organic acids fluctuate according to grade of ripeness: 42%

citric acid and 58% malic acid.

tbl0003Table 3 Mineral salt content of peaches and nectarines

Mineral salts mg kg

1

Calcium 50.0–70.0

Iron 1.1–12.0

Magnesium 70.0–100.0

Phosphorus 120.0–300.0

Potassium 1970.0–2050.0

Sodium 0.0–30.0

Zinc 0.2–1.4

Copper 0.5–0.7

Manganese 0.4–1.1

Selenium Traces

tbl0004Table 4 Vitamin content of peaches and nectarines

Vitamins

Beta-carotene 0.58–4.40 mg kg

1

Vitamin E 7.00 mg kg

1

Vitamin B

0.17–0.50 mg kg

1

Vitamin B

0.40–0.53 mg kg

1

Vitamin B

0.18–0.30 mg kg

1

Niacin 6.00–9.90 mg kg

1

Pantothenic acid 1.40–1.70 mg kg

1

Folate 30.00–34.00 mgkg

1

Vitamin C 66.00–370.00 mg kg

1

The content of beta-carotene (provitamin A) depends on the color of the

cultivar (white, yellow, orange-yellow, red).

PEACHES AND NECTARINES 4419

number of new more suitable cultivars and better

cultivation methods (fertilization, irrigation, preven-

tion of diseases and pests). These developments have

led to the possibility of exploiting moderately favor-

able environmental conditions. Worldwide produc-

tion increased over 20 years by more than 50% and

in 1996–98 reached a volume of 11146 million

tonnes. The USA produced 1302 million tonnes, and

Europe 3418 million tonnes, of which the most im-

portant are Italy 1447 million tonnes, Spain 894 mil-

lion tonnes, Greece 648 million tonnes, and France

468 million tonnes. High production volumes have

been registered in China: 2922 million tonnes,

Turkey: 372 million tonnes, Argentina: 284 million

tonnes, Chile: 278 million tonnes, South Africa 221

million tonnes, and Tunisia 221 million tonnes. The

development of international trade was also a great

contributory factor: it solved problems of rapid trans-

port without losses, mainly due to standardization

and refrigeration all the way from harvest to con-

sumer.

Seealso: Canning:Principles;Cansandtheir

Manufacture; Cherries; Chilled Storage:Principles;

Controlled-atmosphere Storage:EffectsonFruitand

Vegetables; Fruits of Temperate Climates:Commercial

andDietaryImportance;FactorsAffectingQuality;

ImprovementandMaintenanceofFruitGermplasm;

Plums and Related Fruits; Preservation of Food;

Ripening of Fruit

Further Reading

Blattny

C (1986) Koserva

renske

Suroviny. Prague: SNTL.

Commission Regulation (EC) no. 2335 (1999) Laying

down marketing standards for peaches and nectarines.

Official Journal of the European Communities L 281/

11: 4.11.

Crisosto CH and Kader AA (2002) Peach – postharvest

quality maintenance guidelines. http://postharvest.ucda-

vis.edu/produce/producefacts/.

Crisosto CH and Kader AA (2002) Nectarines – postharvest

quality maintenance guidelines. http://postharvest.ucda-

vis.edu/produce/producefacts/.

Das Grosse Lebensmittel Lexikon, 3rd edn. (1985) Inns-

bruck: Pinguin Verlag.

Der Kleine Souci Fachmann Kraut, 2nd edn. (1991)

Lebensmitteltabelle fuer die Praxis, 2nd edn. Stuttgart:

Wissenschaftliche Verlagsgeselchaft.

Ensminger AH, Ensminger ME, Konlande JE and Robsen

JRK (1995) The Consise Encyclopedia of Foods and

Nutrition. Boca Raton, FL: CRC Press.

Faust M and Timon B (1995) Origin and dissemination of

peach. In: Janiek J (ed.) Horticultural Reviews, vol. 17.

John Wiley.

Fideghelli C, Della Strada G, Grassi F and Morico G (1998)

The peach industry in the world: present situation and

trend. Proceedings of the Fourth International Peach

Symposium. Acta Horticulture 465:

Hubbard EE, Purcell JC and Ott SL (1986) Variety Changes

in the Georgia Peach Industry, 1957–1984. University of

Georgia: Agricultural Experiment Station.

Kutina J et al. (1991) Pomologicky

Atlas 1,2. Prague:

Zeme

l. Nakl. Bra

zda.

Kyzlink V (1990) Principles of Food Preservation. Amster-

dam: Elsevier.

Marec

ek F et al. (1994) Zahradnicky

Slovnı

´k

Nauc

Prague: U

ZPI.

Stehlı

kVet al. (1969) Nauc

Slovnı

k Zeme

lsky

1,2.

Prague: UVTI-SZN.

PEANUTS

T H Sanders, North Carolina State University, Raleigh,

NC, USA

Origin

0001 Arachis hypogaea L., commonly known as peanut,

groundnut, monkey nut, goober, or earth nut because

the seed develop underground, is in the division

Papiolionaceae of the family Leguminosae. The

peanut is only one of a few hundred species of

legumes that produces flowers above ground but de-

velops the fruit below ground. Peanuts are native to

South America and were cultivated in pre-Columbian

native societies of Peru as early as 3000 bc. Peanuts

probably originated in the region of eastern South

America, where a large number of species are found

growing wild. A Bolivian origin is suggested by the

wide range in seed and pod morphology documented

there. It has been suggested that A. hypogaea origin-

ated from a hybrid between A. cardenasii (nn) and

A. batizocoi (K. & G.), as both parents occurred in

reasonable proximity in Bolivia. Peanuts were widely

distributed throughout South and Central America

and the Caribbean region during the time of Colum-

bus. Peanuts were probably brought to West Africa

from Brazil in the sixteenth century and then to the

African east coast and to India. Peanuts from widely

4420 PEANUTS

separated regions of the world were brought to Africa

and it is regarded as a center of genetic diversity.

Production

0002 Worldwide production figures for peanuts are esti-

mated at slightly less than 30 10

t and peanuts

are produced on a significant basis in more than 30

different countries. In recent years, India, China, and

the USA, the three largest producers, accounted for

approximately 65% of the world production. Pro-

duction figures for the USA are relatively stable at

about 1.6 10

metric tons. However, production

from China and India have been about 10.9 10

and 7.4 10

t, although recent estimates from India

at 7.4 10

t are probably much higher than current

production. Although cultivated for many centuries,

the economic importance of groundnuts and ground-

nut oil has increased rapidly only in the past century.

0003 Yield per hectare is highly variable, depending on

environment, variety, disease, and other factors.

Important increases in peanut yield occurred between

1960 and 1990 and these increases are due to

improved technology and management of factors

which reduce yield. Peanuts are a high-value crop

and an important source of revenue to producers

throughout the world, and especially in less

developed countries. The exportation of peanuts is

mainly from the USA, China, and Argentina, while

less developed countries utilize peanuts produced

within the country, and the majority of these are

processed for oil. The percentage of peanuts crushed

for oil is a function of the use of peanuts as edible

products and the need for readily available, cheap

cooking oil. On a world basis, more than 50% of

the peanuts produced are crushed for oil. In India,

75–80% of the peanuts produced are crushed for oil,

while in the USA only approximately 12% of recent

production is crushed.

0004 World production of peanut oil is estimated at 4.65

million metric tons (Table 1). Extraction methods

(hydraulic press, expeller, and/or solvent extractor)

may differ widely due to technological advances in

some countries; however, residue may contain 1–7%

oil and with inefficient equipment the percentage may

be much higher.

Peanut Plant

0005 The leaves of peanuts are alternate and pinnate, with

three to four leaflets on long petioles (Figure 1). The

leaflets, which are obovate and softly hairy, are

normally about 3–5 cm long. Peanuts have a distinct

main stem and variable numbers of lateral branches.

There are two major types of peanuts based on

growth habit of the plant – upright with erect central

stem and spreading with numerous laterals. The

upright type is suitable for mechanical production,

and the spreading type is grown more often in less

developed farming operations. The root system of

peanuts is often expansive and may be found up to a

depth of 2 m. Several strains of Rhizobium nitrogen-

fixing bacteria are found in abundant nodules on

main and lateral roots.

Flower, Fruit, and Seed

0006Peanuts have yellow flowers on axillary branches

which are small (about 12 mm long). Depending on

genotype, environment, and temperature, flowering

starts at about 25 days after emergence and the most

tbl0001Table 1 Area, yield, and production of peanuts: average for

1995–2000

Country Area

(million hectares)

Yield

(tonsper hectare)

Production

(million metric

tons)

India 7.78 0.95 7.39

China 3.89 2.80 10.90

USA 0.58 2.87 1.67

Senegal 0.73 0.90 0.66

Sudan 0.55 0.67 0.37

Brazil 0.09 1.77 0.16

Argentina 0.29 1.49 0.43

South Africa 0.09 1.57 0.15

Other 6.93 0.98 6.77

Total 20.94 1.36 28.51

Source: US Department of Agriculture, Foreign Agricultural Service,

Cotton, Oilseeds, Tobacco, and Seeds Division. October 2001.

fig0001Figure 1 Peanut plant.

PEANUTS 4421

prolific flowering occurs between 5 and 11 weeks

after planting (Figure 2).

0007 Under the best of conditions, fewer than 20%

of the flowers produce mature fruit and with drought

or heat stress the percentage may decrease to fewer

than 15%. Genotypes which produce most flowers

during the first 2 weeks of the flowering period

produce greater numbers of pods. Peanuts are gener-

ally self-pollinating, although a small amount of

cross-pollination may occur. About 7–10 days after

fertilization, the receptacle thickens and elongates

into a long carpophore bearing the fertilized ovules

to the ground. The carpophore is commonly known as

the peg, and the action of burying the immature pod is

known as pegging. Growth of the peg is positively

geotropic until it enters the soil – approximately

5–7 cm. The tip then turns horizontal and begins to

develop into a fruit, commonly referred to as a pod,

containing from two to four seeds and ranging in size

up to 8.0 2.7 cm. The enlargement of the pod pro-

ceeds from base to apex and reaches maximum size

about 3 weeks after the penetration of the peg into the

soil. As the pod matures, the inner face of the shell

becomes increasingly darker in color, associated with

an increased tannin content, and becomes very dark

brown on maturation. Seeds show large variations in

size, shape and color, all of which are fairly stable for

any given cultivar. Seed size, together with the seed

mass, has been used extensively in agronomic classifi-

cation of peanuts. Larger seed types are generally

preferred for confectionery purposes; mostly small

and medium-size seeds are used to produce oil.

Peanut Composition

0008 Peanut composition is greatly affected by variety,

environment, and maturity. The interaction of these

factors with harvest date and handling determines the

specific composition of an individual lot. Average

percentages for peanut components are presented in

Table 2.

Oil

0009Peanut oil content is considered to average about

50% and the triacylglycerol content is generally in

the range of 95%. Peanut oil is composed of mixed

glycerides and contains a high proportion of unsatur-

ated fatty acids, in particular, oleic (18:1) and linoleic

(18:2). Additional fatty acids are palmitic (16:0),

stearic (18:0), arachidic (20:0), 11-eicosenoic (20:1),

behenic (22:0), and lignoceric (24:0). A comparison

of fatty acid content with some other vegetable oils

(Table 3) shows that peanuts are considered to

have generally undetectable levels of linolenic acid.

Peanuts contain higher levels of oleic acid than corn

and soybean but lower levels than olive oil. However,

peanut lines with high oleic acid concentration have

recently become commercially available. The fatty

acid profile from these peanuts is similar to that of

olive oil.

0010Several years ago, research at the University of

Florida examined approximately 500 peanut lines

for fatty acid distribution and identified two lines

with oleic-to-linoleic ratios of about 35. Using

classical breeding techniques, commercial peanut

varieties have been developed incorporating the high

oleic acid trait. The developed lines do not have

meaningful differences in oil content, flavor, color,

or texture. Oxidative stability comparisons of high

160 170 180 190 200 210 220 230

Julian date

100

125

150

Number of flowers 3 m

−1

fig0002 Figure 2 Number of flowers of peanut plant as a function of

time.

tbl0002Table 2 Typical composition of peanut kernels

Constituent Range (%) Average (%)

Moisture 3.9–13.2 5.0

Protein 21.0–36.4 28.5

Lipids 35.8–54.2 47.5

Crude fiber 1.2–4.3 2.8

Nitrogen-free extract 6.0–24.9 13.3

Ash 1.8–3.1 2.9

Reducing sugars 0.1–0.3 0.2

Disaccharide sugar 1.9–5.2 4.5

Starch 1.0–5.3 4.0

Pentosans 2.2–2.7 2.5

tbl0003Table 3 Fatty acid profiles of peanut, olive, corn, and soybean

oils

Fatty acid 16 18 18:1 18:2 18:3 20 20:1 22 24

Peanut 11.1 2.4 46.7 32.0 1.3 1.6 2.9 1.5

Olive 9.0 2.7 80.3 6.3 0.7 0.4

Corn 10.9 2.0 25.4 59.6 1.2 0.4

Soybean 10.6 4.0 23.2 53.7 7.6

4422 PEANUTS

oleic peanut oil versus normal peanut oil were made

using extracted, neutralized, and bleached oil from

isogenic peanut lines varying only in fatty acid com-

position. Oil from the high oleic line contained

76.3% oleic and 4.7% linoleic compared to 56.6%

oleic and 24.2% linoleic in the normal peanut oil.

Oxidative stability was found to be as high as 14.5

times greater for high oleic peanut oil depending on

the method of measurement. Details of peanut oil

composition and characteristics are provided in the

section on vegetable oils.

Extraction of Peanut Oil

0011 Peanut oil is held in cells in an extremely fine emul-

sion. Damage to cells results in the release of oil.

Peanut oil is usually extracted by hydraulic press,

expeller, and solvent extractor. These may be used

separately or in combination. The oil in the residue

from oil recovery by the three methods is about 7, 5,

and 1%, respectively. The residue (press cake) from

the hydraulic press and expeller is generally used for

livestock feed, and that from solvent oil extractors

may be finely ground into flour for human consump-

tion, if the nuts were of good quality.

0012 Proteins The total protein content of whole seed

peanuts ranges between 22 and 30%. Total protein

can be separated into four major fractions: albumins,

arachin, nonarachin, or conarachin. The arachin and

conarachin fractions represent about 63% and 33%

of the total, respectively. The arachin fraction is rich

in threonine and proline and poor in lysine and

methionine, while the conarachin fraction is poor in

phylalanine and tyrosine.

0013 The arachin and conarachin protein fractions are

complex in composition and structure. Gel electro-

phoresis of sodium dodecyl sulfate dissociated pro-

teins showed that these two fractions each contained

five different components having molecular weights

between 20 and 84 kDa. Two-dimensional poly-

acrylamide gel electrophoresis of seed polypeptides

resulted in the detection of at least 74 major and

between 100 and 125 minor peptides among various

peanut cultivars and breeding lines. Variation existed

among the major polypeptides of the cultivars, as

noted by isoelectric points between pH 4.4 and 8.0

and molecular weights between 16 and 75 kDa. There

is genetic variability in the mechanism for peanut

protein synthesis, indicating that there is a potential

for the development of peanut cultivars possessing

nutritionally desirable proteins by manipulating

protein synthesis.

0014 Nutritional value of peanut protein depends on the

amount and kind of essential amino acids available

during digestion (Table 4). Amino acid availability

in peanuts and peanut products is enhanced by the

processing they undergo before consumption. Anti-

nutritive factors, including trypsin inhibitors, hemag-

glutinins, goitrogens, saponins, and phytic acid are

present in raw peanuts, and heat treatment in blanch-

ing and roasting of peanuts destroys the trypsin

inhibitor and hemagglutinin. Peanuts are generally

considered to be deficient in lysine and methionine,

thus their relative nutritive value is decreased in

comparison with a reference protein. The protein

efficiency ratio for peanut protein is generally con-

sidered to be 1.5–1.8 and these values are related to

the limited availability of lysine and methionine.

0015Carbohydrates The carbohydrate content of peanut

kernels is usually determined by difference from the

proximate analysis. It has been found to range from

10 to 20% of the fresh weight. Defatted peanut meal

contains about 38% total carbohydrate. The major

components are starch, sucrose, and nonstarch

polysaccharides. Defatted meal contains about 18%

sugars.

0016The major sugars in peanut are sucrose, stachyose,

raffinose, fructose, and glucose. Inositol, verbascose,

arabinose, and galactose have also been reported in

various studies. The total sugar content has been

found to vary with genotype, maturity, growing

conditions, storage conditions, and kernel size.

Large kernels usually contain less sugar. Cooler grow-

ing conditions were found to produce more sugars

and sugar content decreases with maturity. Sucrose

is the predominant sugar, with the content ranging

tbl0004Table 4 Amino acid composition of peanuts

Amino acid % Totalprotein

Aspartic acid 11.89

Threonine

2.43

Serine 5.11

Glutamic acid 19.83

Proline 4.44

Cystine 0.81

Glycine 6.59

Alanine 4.12

Valine

3.14

Methionine

0.51

Isoleucine

3.40

Leucine

5.21

Tyrosine 4.09

Phenylalanine

6.38

Histidine

3.17

Lysine

3.87

Arginine

10.81

Data represent means from several sources.

Essential amino acids.

PEANUTS 4423

from 2.7 to 3.5%. Stachyose is the next abundant,

at levels of 1.5–2.5%. Other values found are

0.02–0.06% for raffinose and 0.01–0.04% for inosi-

tol. Fructose and glucose are usually present at less

than 0.02%.

0017 The sugar content is important for peanut flavor.

Free sugars are noted to be precursors to roasted

peanut flavors. When roasted, there is loss of some

sugar content, with the greatest losses being sustained

by fructose and glucose.

0018 Vitamins and minerals The vitamin content of

peanut seed is shown in Table 5. Peanuts have little

or no vitamin A activity. Three forms of tocopherol

(a, g, b) have been found, with g-tocopherol the

highest and b-tocopherol the lowest. Peanuts are con-

sidered to be a good source of vitamin E, niacin, and

folate.

0019 Peanuts contain several of the minerals essential for

human growth and development (Table 6). Recom-

mended daily intake percentages of the quantities

present are significant and constitute a good source

of minerals.

Production and Handling Practices that

Affect Quality

Maturity

0020 Peanut maturation is extremely important in changes

of biochemical components related to quality and

shelf-life potential. Those facts have been demon-

strated collectively in sensory studies to evaluate the

relationship of maturity and flavor quality. Mature

peanuts tend to have increased intensity of positive

flavor descriptors, such as roasted peanutty and sweet

aromatic, while immature peanuts are more com-

monly associated with negative terms, such as painty

and fruity fermented. The term ‘painty’ is related to

the common term ‘rancid’ and indicates the propen-

sity of oil components in more immature peanuts to

undergo enzymatic or autooxidation changes that

result in decreased shelf-life. The degree of dark

roast color is related to maturity level, with immature

peanuts roasting darker because of higher free sugars

and free amino acids. The relationship of high curing

temperature to decreased sensory acceptability in

immature peanuts has been demonstrated. Further,

decreased sensory acceptability caused by high inten-

sities of the off-flavor term ‘fruity fermented’ in sized

lots was related to darker roast colored immature

peanuts in the lot.

0021 Maturity in peanuts is a complex concept because

peanuts of all market types are generally marketed in

various commercial seed sizes based on thickness, or

on count per unit weight. The complexity arises in

that all mature peanuts are not large and all immature

peanuts are not small. Although size and maturity are

positively related, the relationship is not absolute,

and peanuts of very different maturity are found

consistently in all commercial sizes. This fact is con-

founded even more in lots that are marketed on a

count-per-weight basis wherein large and small seed

may be mixed together to give the same count as seed

of consistent uniform size. Peanut seed size distribu-

tion is affected by the environment in predictable

ways. Soil temperature increases tend to shift the

mean seed size down while cooler temperatures shift

the mean size upward. Irrigation, harvest date, and

soil temperature treatments generally produced sig-

nificant differences among percentages of individual

maturity classes in each commercial size. The distri-

butions of maturity classes within commercial sizes

are sufficiently different to suggest that flavor, roast

color, shelf-life, and other quality factors would be

affected in final roast products. Published data indi-

cate that there are sensory differences in medium-

grade-size peanuts harvested on a weekly basis over

a 6-week period. In these studies, the percentage of

immature peanuts in the seed sized lots progressively

decreased with time. Roasted peanuts from earlier

harvests had lower roast peanut impact and more

bitter taste. Although shelf-life studies were not

tbl0005Table 5 Essential vitamin composition of peanuts

Amount

%RDI

Vitamin E 3.3 IU 11

Folate 41 mg10

Niacin 3.8 mg 19

Thiamin (B

) 0.12 mg 8

Riboflavin (B

) 0.03 mg 2

Vitamin B

0.07 mg 4

Based on 1 oz serving of dry roasted peanuts.

RDI, recommended dietary intake.

tbl0006Table 6 Composition of some minerals in peanuts

Amount (mg)

%RDI

Zinc 0.94 6

Copper 0.2 10

Potassium 186.5 6

Calcium 15.3 2

Iron 0.6 3

Phosphorus 101.5 10

Magnesium 50 13

Based on 1 oz serving of dry roasted peanuts.

RDI, recommended dietary intake.

Source: US Department of Agriculture, Agricultural Research Service,

1998. USDA Nutrient Database for Standard Reference, Release 12.

4424 PEANUTS