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

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conducted, the increase in percentage of mature

peanuts in progressive harvests predisposes those

lots to longer shelf-life.

Environment

0022 The fact that growth, production, and handling prac-

tices affect quality, flavor, and shelf-life of peanuts and

peanut products is implicit in data from numerous

studies, years of manufacturing use, and the wide

ranges of flavor and shelf-life observed in those count-

less situations. However, although studies report spe-

cific biochemical constituents and the effect of certain

practices and conditions on changes in those com-

pounds, the total effect on final product shelf-life

resulting from all these processes must be extrapolated

using established quantitative and qualitative relation-

ships of specific constituents to shelf-life potential.

0023 The role of environment on peanut yield has been

consistently documented, but the effect on peanut

quality factors potentially related to flavor and

shelf-life has received little recent research attention.

Higher soil temperatures tend to result in smaller seed

size distributions, but studies on biochemical com-

parisons among years do not relate well to specific

environmental conditions. Drought and temperature

stress have been shown to affect some of the protein

factors of peanuts. Soil temperature increases result in

decreased concentrations of the free carbohydrates

fructose, glucose, sucrose, raffinose, and stachyose

in peanuts.

Harvest

0024 When peanut plants are removed from the soil, the

peanuts begin to dry, and the final natural processes

related to potential flavor and shelf-life are initiated.

When peanuts are harvested into inverted windrows,

temperatures inside pods near the ground may reach

40–50



C when air temperatures are no higher than



C. Conditions that slow the drying process with

associated high moisture may lead to fungus growth

with resulting high free fatty acid values due to

microbial lipase activity. Peanuts affected in this

way are usually visibly damaged and may be removed

electronically as part of the shelling process, or in less

developed countries they may be removed by hand

picking. Although off-flavors may not normally be

thought of as factors that reduce shelf-life, usually

the physical, physiological, and biochemical mechan-

isms that contribute to off-flavor development so

disrupt the normal processes that shorter shelf-life

should be anticipated. Obviously, processors will

not knowingly utilize off-flavor peanuts in formula-

tions, but knowledge or stipulation of growing and

handling practices for purchased peanuts may

contribute to the production and delivery of more

stable products by the processor.

0025Maturity, as previously discussed, is a primary

factor in total quality of peanuts, and the level of

total crop maturity at harvest influences many of the

handling and storage factors that follow. Moisture

content decreases as peanuts mature on the plant,

and at harvest, a wide range of moisture percentages

are present. The range has variably been ascribed as

20–70% moisture at the time of digging. Given this,

and the degree of biochemical and physical develop-

ment of the various peanuts, it is readily discernible

that differences in flavor and shelf-life are still being

affected. Peanuts normally air-dry for some period of

time before they are harvested. In mechanical harvest

situations, peanuts usually dry to an average of 20–

25% moisture before being picked and further dried.

0026The physical process of machine harvest has poten-

tial effects on the shelf-life of peanuts due to the force

used to pick and transport peanuts into the machine.

The physical damage in mechanical harvest, noted as

cracked or broken pods, must inherently damage seed

integrity, although relationships to quality reduction

have not been investigated. Peanuts that are field-

dried are subject to various environmental conditions

which may affect quality. Harvested peanuts with a

high percentage of immature pods will be difficult to

dry to an overall safe storage level. High-moisture

peanuts going into storage provide an increased

opportunity for decrease in shelf-life potential.

Storage

0027Shelf-life potential may be maintained in storage of

in-shell and shelled peanuts. In-shell peanuts are

stored in bulk situations in many parts of the world,

often at approximately 10% moisture content. In

these situations, care must be given to ventilation

and moisture control, because as the stored peanuts

cool in response to ambient conditions that are usu-

ally cool, they dry further. The moisture that is lost

must not be allowed to concentrate into the bulk lot

because of obvious quality and microbial consider-

ations. Adequate conditions of storage, especially

ventilation, are critical to maintaining low levels

of free fatty acids and total carbonyl compounds.

Because of the removal of the shell, which is a normal

protective barrier, shelled peanuts are somewhat

more susceptible to quality/shelf-life deterioration.

Shelled peanuts may be held in conditions of c. 0.5–



C and 55–70% relative humidity for periods of a

year or more without quality loss.

0028Moisture content should be in the 7% range and

slightly lower levels may impart additional protec-

tion. In peanuts stored at c. 6 and 9% moisture, the

PEANUTS 4425

higher moisture content resulted in reduced flavor

quality and changes in amino acids, carbohydrates,

and the phospholipid fraction of oil.

Consumption/Uses of Peanuts

Peanut Oil

0029 Peanut oil is used as a cooking oil, especially in deep-

fat frying; peanut oil is excellent since it has a smoke

point of 229.4



C. Degradation which may occur

during frying results in the increase of free fatty

acids and a decrease in smoke point. Crude peanut

oil has a bland, slightly beany, nut-like flavor which

is removed during refining to produce an oil that is

odorless. Peanut oil develops few off-flavors or odors

in use as a frying oil. Peanut oil is sometimes used in

salad oil and in pourable dressings because of the

length of time solids are held in suspension in the

oil, although it solidifies from 0 to 3



C. Refined

peanut oil is widely used to prepare pastries, shorten-

ing (hydrogenation), oleomargarine, mayonnaise,

salad dressings, and other food products. It is superior

to oils from corn, soybean, cotton seed, olive, or

safflower for making salad dressings to be stored

below 12.2



Roasted Peanuts

0030 Peanut roasting is a common practice in much of the

world since roasting brings out the unique flavor. In

western countries, particularly the USA, roasted and

salted peanuts are one of the popular food items,

produced on a commercial scale under a highly

mechanized system with excellent quality control

and packaging methods. In many European coun-

tries, peanuts are roasted and then coated with vari-

ous flavors. A large portion of the US peanut crop is

processed into roasted product for use in peanut

butter, salted peanuts, and confections. Although the

salted, roasted form predominates, oil-cooked, salted,

unsalted, and low-calorie forms such as whole or

mixed nuts are also popular.

0031 A typical protocol for dry-roasted peanuts is expos-

ure to 160



C for 20–30 min. Seed coats are generally

removed before applying oil and salt. In oil-roasting,

blanched peanuts are immersed for 3–5 min in heated

oil. After roasting the peanuts are then subjected to

air cooling and salting with about 1.8–2.2% salt.

Studies conducted to determine the effect of high-

oleic-oil roasting indicated slight increases in shelf-

life of normal oleic peanuts. Since peanut seed coats

contain phenolics, including tannins, and the germs

contain bitter saponin compounds, these are often

removed before consumption. The current methods

of blanching eliminate the skins and germs so that

blanching always precedes oil-roasting, but often

follows dry-heat roasting.

0032Peanuts have a high oil content and defatted

peanuts have been developed to meet a specific con-

sumer market. Partially defatted peanuts are obtained

by hydraulic pressing to remove about 50% oil,

followed by restoration of pressed kernels to their

original size and shape by immersion in boiling

water containing salt, species, or flavorings. Kernels

are then dried and roasted. The pressure applied in

the hydraulic press, the holding time, and the initial

depth of peanuts in the compression influence the

reconstitution of peanuts.

Peanut Butter

0033Although not a product accepted worldwide, peanut

butter and products made from it are the most

consumed form of peanuts in the USA, and notable

consumption occurs in Canada and The Netherlands.

Marketing introductions of peanut butter are still

in progress in many European countries. Peanut

butter is made by the fine grinding of dry roasted

peanuts. Salt, hydrogenated oil, and sugar are usually

added. Peanut butter may be made from any variety

of peanuts but the blend of two parts Spanish or

runner peanuts with one part Virginia peanuts is

considered best for the most desirable consistency.

Peanut quality, roasting techniques, manipulation of

temperature, and grinding result in a wide range of

colors, flavors, and consistencies of peanut butters on

the market.

0034After grinding, oil separates from the solid particles

unless a crystalline lattice is formed. Since crystals of

fat are not present in the natural oil of peanut butter

at ordinary temperatures, hydrogenated peanut oil,

which is crystalline at these temperatures, is mixed

uniformly with the product to provide such crystals.

Generally, the incorporation is accomplished above

the melting point of the hydrogenated peanut oil to

insure more complete dispersion of the hydrogenated

oil. In a satisfactorily stabilized peanut butter, crystal-

lization of the added fat (hydrogenated peanut

oil) takes place generally throughout the product

before the oil–meal mixture can separate. Trans-fats

infrequently associated with hydrogenated oil have

recently been examined in commercial peanut butters

and the work demonstrated unmeasurable quantities

using current technology.

Confections

0035Peanuts (split, granulated, whole or ground peanut

paste) are used in a wide range of other products,

4426 PEANUTS

including confections such as candy bars, drage

es,

hard-coated peanuts, peanut butter cups, peanut

brittle, and a variety of other specialty applications.

Shelf-life is important for confectionary products

and is greatly affected by the product configuration,

moisture content, and storage temperature.

Aflatoxin

0036 Aflatoxin is a potentially carcinogenic compound

produced by Aspergillus flavus and A. parasiticus

which can invade peanuts, corn, cottonseed, and

other commodities. In technologically advanced

countries, control programs and testing programs

are in place which significantly reduce the concen-

trations of aflatoxin over those found in developing

countries. Aflatoxin contamination is usually found

to be the most serious when drought conditions are

present during the last few weeks of growth and pod

development. Preharvest contamination is a signifi-

cant economic problem for the peanut industry. Pre-

harvest aflatoxin contamination in the crop is a

problem when drought-type conditions predispose

peanuts to insect damage by lesser corn stalk borer

and other insects which are known carriers of fungus

spores. Invasion of pods and infestation of seed often

result in visible damage, and high levels of aflatoxin

are characteristically found in damaged kernels. Pre-

harvest invasion can occur with no obvious kernel

damage and, although extensive studies have been

conducted, the exact mechanism of fungal invasion

is not yet known. Aflatoxin contamination is often

highest in small, immature seed. Studies have demon-

strated a relationship between the water activity-

related physiological ability of the seed to produce

phytoalexins and the water activity at which the

fungus can best invade the seed. As the ability of the

seed to produce phytoalexins decreases, there appears

to be a point at which the fungus can grow in the seed

before decreasing water activity terminates growth of

the fungus.

0037 Although generally less frequent, postharvest

contamination may be a problem, especially when

moisture accumulation and proper temperatures are

present in harvest, transport, or storage.

0038 Once the pods are field-dried and stripped from

plants, they must be dried to moisture content less

than 9% prior to storage. Peanuts stored at moisture

content greater than 10% have increased risk for

growth of A. flavus. Once dried to less than 9%

moisture, peanuts can be stored for long periods

with little loss of quality if kept under controlled

storage conditions. Control of aflatoxin is best

addressed during production by the appropriate

irrigation of the crop through harvest time. In most

contaminated lots, only a relatively small number of

kernels is contaminated, and in many cases physical

separation is the ideal method. This is based on the

assumption that contaminated kernels are either

discolored or shriveled. Methods include manual

sorting, mechanical sorters, or electronic scanning,

which examines each kernel separately and accepts

or rejects it on the basis of reflectance. Action levels of

aflatoxin in peanuts and other commodities are set

and rigorously enforced within producing countries,

and import regulations carefully control levels which

may be imported.

Peanut Allergy

0039In recent years, concern for food allergies in general

has increased, and concern for peanut allergy is no

exception. For unknown reasons, peanut allergy is

associated with a higher incidence of fatal food-

induced anaphylaxis than any other food allergy. Im-

mediate hypersensitivity to foods occurs in 6–8% of

children and about 1% of adults. In the USA, a recent

survey suggested that 0.7% of children are allergic to

peanuts in varying degrees. Avoidance is the only

current method of dealing with food allergy. Research

potentials in dealing with peanut allergy will be

discussed later.

0040Five peanut allergens have been identified by dif-

ferent research groups. Two major allergens, Ara h 1

(a vicilin) and Ara h 2 (a conglutin) are recognized by

serum immunoglobulin E (IgE) of greater than 90%

of peanut allergic individuals. Ara h 3 is recognized

by serum IgE of about 40–45% of allergic individuals

and is thus considered to be a minor allergen. Ara h 5

(a profilin) is also a minor allergen; IgE is recognized

by about 13% of allergic individuals. Refined peanut

oil (heat-processed) is not allergenic; however, oils

contaminated with peanut protein may indeed pro-

duce significant allergic reactions in peanut-sensitive

individuals. Cold-pressed oils are more likely to con-

tain peanut proteins than hot-pressed oils.

0041Current research on peanut allergy is directed at

testing an approved asthma drug, anti-IgE mono-

clonal antibody, against peanut allergy. Development

and testing of a vaccine against peanut allergy are

progressing towards human trials. A third area of

research involves identification of enzymes involved

in mediation of the allergic reaction and development

of a test kit for individuals (especially children) to

determine potential for peanut allergy.

See also: Aflatoxins; Amino Acids: Properties and

Occurrence; Food Intolerance: Food Allergies; Sweets

and Candies: Sugar Confectionery; Vegetable Oils:

Composition and Analysis

PEANUTS 4427

PEARS

C Blattny

, Prague, Czech Republic

Introduction

0001 The genus of pear Pyrus has about 20 species. Culti-

vars of the common pear (mainly European and

American) belong to Pyrus communis. The Asian

cultivars belong to the sand pear Pyrus serotina ¼

P. pyrifolia. The pear is a member of the rose family

(Rosaceae).

Origin and History

0002 The common pear came from Central Asia. It was

well known and popular in ancient Greece. In the

year 287 bc Theofrast, in his Historia Plantarum,

described four cultivars of pears. The Romans

took over the cultivation of pears from the Greeks.

In the time of Vergil (50 years bc), Cato described

35 cultivars. The number of cultivars increased

very quickly and by the end of the Middle Ages over

200 cultivars were described. But most of the out-

standing dessert cultivars that are now widespread

were selected out in the eighteenth and nineteenth

centuries in France and in Belgium. Most of these

old pear cultivars arose out of the selection of seed-

lings that grew as a consequence of random cross-

breeding. Intentional or deliberate breeding led to

new cultivars during the twentieth century, but a

number of excellent cultivars from the eighteenth

and nineteenth century have not been replaced. By

the end of the twentieth century it is roughly esti-

mated that 3000 cultivars of the common pear had

come into being.

0003 In China the cultivation of sand pear cultivars was

known some centuries before Christ. Nowadays,

many cultivars of the sand pear are widespread in

East Asia. By the end of the twentieth century this

sand pear had spread not only to North America, but

also in smaller amounts to other continents. This

species is also used for hybridization with the

common pear, especially in the USA, as hybrids are

less susceptible to the dangerous infectious bacterial

disease fireblight.

Requirements of the Pear Tree

0004 The pear tree, depending on the species and cultivar,

has moderate to high demands of temperature (in

winter as well as in summer) and length of vegetation

period. Winter cultivars need warmer regions with a

longer vegetation period to ripen properly and to

attain better quality. Some of the cultivars do not

tolerate extensive winter frost, e.g., Bartlett (Williams

Christ). Fairly rich, warm, loamy soil, of sufficient

depth and with a well-drained subsoil are suitable for

the pear. Of all temperate climate fruit species, pear

quality is the most influenced by soil properties and

weather.

0005The trees that grow naturally from seeds (or grafts

on pear seedlings) reach a height of up to 9 m with

trunks of 30 cm or more in diameter. The cultivars of

pears can only reproduce by being grafted on a root-

stock – usually a pear seedling. In order to create

smaller or dwarf trees the quince can be used as the

rootstock. Most widespread vegetatively propagated

clones of the quince are: quince A, quince C, from

East Malling Research Station in England, French Pro-

vence Quince BA 29 C, and Le Page series C. In the

USA a new hybrid Old Home Farmingdale 333

(OH F333) is now also recommended. Certain

cultivars like Bartlett (Williams Christ) and Bosc are

incompatible with the quince and require an interstem,

e.g., cultivar Hardy or Old Home (used in the USA).

0006Many pear cultivars are self-sterile. They need the

pollen of other cultivars to develop fruitfully. Some

cultivars have relatively often parthenocarpic fruit

(without kernels). Those fruits are usually longer

and slimmer.

0007The cultivars of the Japanese-type Asian pear will

pollinate each other. Chinese types need another cul-

tivar for pollination, and when they bloom with the

cultivars of the common pear, these cultivars could be

very good pollinators for them.

0008As regards the sand pear’s requirements of the en-

vironment, these are similar to the common pear, but

it seems that suitable districts for peaches will also be

best for most sand pear cultivars. Pyrus betulaefolia is

recommended as standard rootstock for sand pear

cultivars. The hybrid OH F333 is also suitable.

The Fruit

0009The pear is a typical pome fruit closely related to

the apple. The basic shape is pear-shaped and

ranges according to the cultivar from bell-shaped, to

egg-shaped, conical, globular and teardrop-shaped

(Figure 1). Further differences are in size, color,

texture, flavor, taste, ripening season, and possibil-

ities for processing and cooling.

0010The flesh is usually firmer than that of apples;

when fully ripe it softens and finally it melts. After

4428 PEARS

overripening the flesh quickly melts due to hydrolysis

of pectin and total disorganization of enzymes. At

optimal grades of ripeness, the fruit of the best dessert

cultivars melts like butter. The skin is smooth and its

color varies from yellow, yellow green, to brown

(maybe russet) and also almost red. Only two culti-

vars are bright dark red: Max Red Bartlett and Red

Anjou. The flavor and taste of cultivars differ greatly

– some are spicy like muscat. There is another con-

spicuous difference between pears and apples. In the

center of a pear around the core and along the vessels

from the stem to the core, the gritty cells called stone

cells are present. The more gentle the cultivar, the

fewer small stone cells are present. However, very

small stone cells in a very small number are always

present in the best dessert cultivars, e.g. Bartlett

(Williams Christ). The number of stone cells is not

only influenced genetically by also by the quality of

the soil, especially for winter cultivars. Most modern

dessert cultivars of the common pear have large

heavy fruit: medium weight 150–180 g, heavy weight

200–400 g, giant weight up to 750 g.

0011 Asian pears are also called Oriental pears, Chinese

pears, and Japanese pears. The Asian pear cultivar

differs in its flesh texture – when eaten ripe they

remain pleasantly firm, crisp, and juicy like apples

but with a different and distinctive texture. They do

not change texture after being picked and stored like

common pears. Most Asian pears are sweet, flavorful,

and low-acid. They are round or flat fruit with yellow

or green skin, with bronze-colored and russeting skin

or they are pear-shaped with either smooth or

russeted skin.

Diseases and Pests

Diseases

0012Some virus and Mycoplasma diseases are relatively

widespread. We will only discuss a few here. Ring

pattern mosaic gives striking light-green or greenish-

yellow rings and a line pattern in the leaves. Yellow

veins and red mottle are typical with chlorotic

banding of the tertiary and final veins. Both diseases

suppress growth in a number of pear cultivars. The

disease stony pit occurs wherever pears are grown.

The fruits of diseased trees become pitted and

deformed with many gritty cells in the tissue near

pitty areas. Fruits with many pits are woody and

difficult to cut. Either only a few or all of the fruits

of diseased trees may develop symptoms, depending

on the susceptibility of the cultivar. An affected fruit

may have one or a number of pits and is not suitable

for eating. The content of dry matter, ash, potassium,

calcium, and mallic acid is higher in diseased fruits

then in comparable healthy ones. The content of

monosaccharides is less. The affected fruits cannot

be used to produce sherry and brandy. Very sensitive

cultivars are Bosc, Doyenne

du Comice, while Bartlett

in the USA is relatively resistant.

0013Fireblight, a bacterial disease, is the greatest

problem limiting production of pears in the USA.

Fireblight seldom affects Europe. Leaves and young

terminal shoots infected by bacteria Erwinia amylo-

vora wilt, die, and blacken. Further infection of

branches and trunk results in the development of

cankers and finally the death of the tree. Recommen-

dations for decreasing the danger of fireblight are:

0014Select tolerant, better resistant cultivars. In the

USA recommended hybrids between common

and Asian pears include: Moonglow, Kieffer,

Seckel, Waite, and Maxim.

0015Control of the vector – green apple aphids (Aphis

pomi).

0016Avoid any practice that encourages excessive and

soft terminal growth.

0017Prune out and burn the infected portion of the tree

(better in winter) and avoid overfertilization.

910

23 4

fig0001 Figure 1 Different shapes of pear. 1, pear-shaped; 2, bottle-

shaped; 3, bell-shaped; 4, conical; 5, egg-shaped; 6, teardrop-

shaped; 7, cylinder-shaped; 8, fig-shaped; 9, globe-shaped;

10, flat globe-shaped

PEARS 4429

0018 Pear scab is a disease caused by the fungus Venturia

pirina. The infection starts at blossom time and

occurs on the blossoms, more so on the leaves than

on the fruits. Infection of young pear fruits may cause

the pear to be lop-sided and sometimes cracked. Then

the scab spots spread on the whole fruit, especially on

that of the susceptible cultivar. After very late infec-

tion, small scabs occur which then develop into so-

called storage scabs. Spraying during infection time

(May–July) is one of the best control measures.

0019 During longer storage some pathological and

physiological disorders can occur:

0020 blue mold rot (Penicillium expansum) – after

mechanical injury

0021 gray mold rot (Botrytis cinerea) – infection during

blossoming or through wounds of mature fruits

0022 senescent scald – dark brown skin discoloration

0023 superficial scald – diffuse brown skin discoloration

0024 freezing injury – translucent, water-soaked appear-

ance of tissue

0025 bitter pit – brown, corky lesions in the flesh

0026 watery breakdown – rapid enzymatic flesh break-

down

0027 carbon dioxide injury – browning of interior walls

of carpels and adjacent core tissue

0028 low-oxygen injury – core browning

0029 Control measures

0029 effective preharvest disease control procedures

0030 careful handling during harvesting and postharvest

preparation for market to minimize mechanical

injuries

0031 prompt cooling to 0



0032 maintenance of proper temperature (1



Cto0



during storage and transport

0033 use of postharvest chemical treatments

0034 use of the controlled atmosphere

Pests

0035 Codling moth (Laspeyresia pomonella) larvae feed on

the fruits to the core and enlarge an exit hole which

they plug with frass. They can have two to three

generations and they are the most dangerous pests

to apples and sometimes can be pernicious to pears.

Spraying when females lay their eggs (June, July) is a

good control measure.

0036 Pear midge (Contarinia pyrivora) can cause consid-

erable damage to young fruits. The attacked fruitlets

become deformed and enlarged, and are later black in

the center and full of white maggots, and they crack,

decay, and fall down in a short time. They hibernate

in the soil. Spraying just before the blossoming can

decrease the damage.

0037Pear leaf midge (Psylla pyricola) in some districts

is an important pest, resembling a miniature cicade.

The psyllas suck on the leaves which margins roll.

Maggots produce a honeydew that collects in drop-

lets on the leaves, branches, and the fruit. It is an

excellent medium for sooty molds. The crop is usually

lower and unsellebled. Another danger to pear psylla

is in its transmission of Mycoplasma.

Harvesting

0038The pear has to be gathered from the tree before full

ripeness, usually when the basic green color changes

to yellowish green. It is very important to determine

the correct time for the crop. Prematurely harvested

fruits do not ripen but they stay hard permanently

and become leathery. Therefore the best time for

gathering is when the fruits attain normal size,

which is optimal for the cultivar, at the time when

the stem parts readily from the branch if the fruit is

slightly lifted. Then it is important to get the fruit

quickly to cool storage. Overripe fruits soften so

quickly that they are nearly useless.

0039To harvest fruits of Asian pears one must hold them

lightly in the palm and pluck them using an upward

twisting motion to remove the fruit from the spur. A

pulling motion can result in damage as the stalk may

be removed from the fruit. The skin of Asian pears is

much more susceptible to abrasion and friction marks

than common pears. Smooth surface containers such

as polystyrene trace should be used to gather fruit.

Fruit should be placed into trays with the stem end

upward, preferably in single layers.

Chill Storage

0040Only a very small number of common pear cultivars

can endure longer preservation in chill storage (Bosc,

Anjou, Doyenne

du Comice) if they do make it to the

fresh market. These cultivars can be stored in con-

trolled atmosphere (1–2% O

þ 0–1% CO

)at1



for up to 4 months (Bosc and Doyenne

du Comice) or

6 months (Anjou) while maintaining their capacity to

ripen and attain good flavor and texture. Some winter

cultivars can be stored in cooler places for some

months until spring, but their quality is much lower

(Diel, Comtesse de Paris, Nelis). For chilling it is

necessary to have optimal temperature 1–0



C, op-

timal relative humidity 90–95%, and for ripening,

optimal conditions are 15–22



Cand90–95% rela-

tive humidity. This basic schedule for ripening must

be introduced after each longer cool storage of all

pear cultivars to help the development of flavor and

optimal texture of the flesh.

4430 PEARS

0041 Some of the Asian pear cultivars, e.g., Shinseiki,

Hosui, Kosui, Nijisseiki, have an adequate storage

life. If fruits are harvested at the recommended ma-

turity, a storage life of 12–20 weeks and subsequent

shelf-life of 10–15 days can be expected, depending

on the cultivar.

Important World Cultivars

.0042 Common pear

0043 Summer – Bartlett (¼ Williams Christ), Dr J.

Guyot, Clapp’s Favourite, Santa Maria, Max Red

Bartlett

0044 Autumn – Doyenne

du Comice, Bosc, Conference,

Fondante de Charneuses, Elisabeth, Luise Bonne,

Boussock, Hardy, Lucas

0045 Winter – Diel, Comtesse de Paris, Anjou, Red

Anjou, A. Lucas, Passe Crassane, Nelis

0046 Sand (Asian) pear (recommended in the USA)

0047 Early – Shinseaki

0048 August – Hosui, Kosui, Nijisseiki (Twentieth Cen-

tury), Yo Inashi

0049 Late – Shinko, Olympic (Korean Giant)

0050 Sand (Asian) pear (widespread in China)

0051 Ya Li, Tse Li

Supplying Fresh Fruit to the Consumer

0052 The fruit must be intact, sound, clean, free of any

visible foreign matter, free from pests, free of abnor-

mal external moisture, and free from any foreign

smell or taste. The fruit must have been carefully

picked and sufficiently developed so that the ripening

process can continue in order to reach the degree of

maturity appropriate to the cultivar, to withstand

transport and handling, and to arrive at the destin-

ation in a satisfactory condition. Usually fruit is clas-

sified into three or four classes according the diameter

of the widest part of the pear fruit.

Use of Fresh Fruit

0053 The time to ripeness for consumption varies

according to the cultivar: summer cultivars – up to

2 weeks; autumn cultivars – 2–8 weeks; winter culti-

vars up to 16 weeks. It is greatly influenced by the

grade of ripeness during gathering and by storage

temperature.

0054 Dessert cultivars of the common pear, when eaten at

the right stage of ripeness (the flesh should melt like

butter) are delicious fruits. The fruits are used in vari-

ous cookies, fruit salads, desserts, and gelatine dishes.

0055 A small warning: it should be mentioned that some

sensitive people can experience flatulence after eating

fruits of the common pear, especially fruits which are

not fully ripened.

0056The Asian pear cultivars are refreshing, very juicy,

crispy like apples and, as with common pears, they go

well with salads.

Processing

0057Pears are less often used for processing, compared to

apples, due to their relatively low acid content and,

above all, to a rapid ripening process which leads to

the already-mentioned melting disintegration and

liquefaction of the fruit. Selected pear cultivars are

outstanding raw material for canning. They must,

however, fulfill strict conditions:

0058The shape of the fruits is one of the decisive deter-

minants of industrial preparation, since a suitable

shape facilitates basic processing – peeling,

halving, and removal of the core. The most suit-

able is a longish pear form with a wider stem part

(for instance, the parthenocarpic fruits of the

Bartlett (Williams Christ)). Cultivars that are too

round have their core situated too high, which

causes difficulties for machine coring. Fruits that

are bottle-shaped, that crack, and that are too

small are unsuitable.

0059The flesh should be white or faintly yellowish.

0060The skin should be firm, not too thick, clearly

demarcated from the flesh, and easily peelable.

0061For factory processing, pears must be of the pre-

scribed size and shape. Fruits of a uniform size

and shape reach most uniformly technologically

required ripeness. This degree is attained when

the basic green color of the skin changes to yellow.

Accurate appraisal of the degree of ripeness

heralded by the changing color of different culti-

vars calls for an experienced eye. Many manufac-

turers use penetrometric methods to measure the

firmness of the flesh, i.e., the pressure needed

to push a special needle to a certain depth of the

fruit. In areas of great production of cultivars

destined for canning, for instance the summer Bar-

tlett (Williams Christ) it is possible to employ

long-term storage at temperatures 1to0



C for

9–12 weeks, or at temperatures þ1



C for 6–8

weeks to extend the processing season. The rela-

tive humidity must be 90–95%. The ripening pro-

cess must follow this chill storage. Similar

conditions can be also used for further canning of

suitable cultivars like Clapps Favourite, Elisabeth,

or Kieffer. The fruits are canned in syrup. To pre-

vent browning of the flesh it is recommended to

plunge the peeled halves in a solution of ascorbic

or citric acid.

PEARS 4431

.0062 Sweetening – the same requirements as for canning

are applied.

0063 Drying of pears is relatively widespread in some

regions. Pears suitable for drying should be of

medium size (3 cm length), typically pear-shaped,

slimmer in the stem part, the skin thinner, and the

flesh with a small number of stone cells. Dried

fruits should have a cinnamon color. Pears should

be fully ripe with the highest content of sugar. They

are dried whole, halved, or divided into small

pieces, with the skin on or peeled.

0064 Pears are not frequently frozen. The requirements

are the same as for canning.

0065 Brandy – due to the delicious flavor of some culti-

vars, e.g. Bartlett (Williams Christ), pear brandy is

the mildest of the fruit brandies.

0066 Perry is a famous light alcoholic drink (like light

wine) made from special perry cultivars. This drink

was produced and beloved in Roman times. It is a

drink of choice particularly in Normandy, the UK,

Austria, Switzerland, and the USA. The special

perry cultivars are highly fertile, with small fruit,

and they should have a high content of sugar and

acids and a rich content of tannins. Unfortunately,

the production of those cultivars declined strikingly

during the twentieth century.

Production

0067 The pear is a popular fruit in temperate regions. Their

production over the last 10 years in individual

countries has developed differently. Worldwide it is

increasing – in 1996–98 it reached 14 034 million

tonnes, while in 1989–91 it was only 9529 million

tonnes. It especially rose in China, by 245%, and

amounted to 6401 million tonnes in 1996–98, that

is, 45% of world output. The increase can also be

observed in South America and Africa – in Chile by

c. 500%, in Ecuador by 300%, in Argentina by 225%,

in Morocco by 430%, in Algeria by 310%, in Tunisia

by 210%, and in Egypt by 350%. Even in other warm

regions production also increased, for instance, in

Lebanon by 390% and in Turkey by 140%.

0068 The changes are the result of the development of

international trade which has facilitated refrigerated

transport of high-quality dessert cultivars over long

distances. Particularly profitable is the supply of the

winter market either from southern countries of

the northern hemisphere or from countries of the

southern hemisphere. Among the largest exporters of

pears we find now Argentina and Chile – not only

Italy, France, and The Netherlands, as it was some

years ago. The decrease in pear output in European

countries is chiefly connected to the increase in the

cultivation of apples and peaches to replace the pear.

Nutritional Value

0069The composition of the pear is given in Tables 1–3.

Pears contain a good quantity of sugars (rapidly

assimilated fructose, glucose, saccharose, and sorbit),

as well as pectin, tannin, mineral salts, organic acids,

some vitamins, and dietary fiber. There is also a rich

content of delicious aromatic substances present. All

this contributes to the great popularity of pears.

Further Reading

Bailey LH (1958) The Standard Cyclopedia of Horticulture,

17th edn. New York: MacMillan.

Blattny

C (1986) Konserva

renske

Suroviny. Prague: SNTL.

Chittenden FJ (1956) Dictionary of Gardening: the Royal

Horticultural Society, 2nd edn. Oxford: Clarendon Press.

tbl0001Table 1 Chemical composition of pears

gkg

1

Water 775–869

Protein 4–5

Total lipid 3–4

Sugar 124–158

Acids 1–5

Dietary fiber 15–28

Ash 3–4

Sugar is composed on average from 54% fructose, 13% glucose, 15%

saccharose, and 18% sorbit. Organic acids fluctuate according to the

cultivar. In dessert cultivars malic acid, prevails citric acid is about 10% of

tbl0002Table 2 Mineral salt content

Mineral salt mg kg

1

Calcium 100.0–160.0

Iron 2.0–3.0

Magnesium 60.0–80.0

Phosphorus 110.0–150.0

Potassium 1100.0–1300.0

Sodium 0.0–20.0

Zinc 1.2–2.3

Copper 0.9–1.1

Magnesium 0.4–0.8

Selenium 0.0–10.0

tbl0003Table 3 Vitamin content

Vitamin

Beta-carotene 0.15–0.30 mg kg

1

Vitamin E 4.30–5.00 mg kg

1

Vitamin B

0.20–0.50 mg kg

1

Vitamin B

0.30–0.40 mg kg

1

Vitamin B

0.15–0.18 mg kg

1

Pantothenic acid 0.62–0.70 mg kg

1

Folate 70.00–140.00 mgkg

1

Vitamin C 40.00–50.00 mg kg

1

4432 PEARS

Commission Regulation (EEC) no. 920/89 (1989) Laying

down quality standards for carrots, citrus fruit and

dessert apples and pears and amending Commission

Regulation no. 58. Official Journal of the European

Communities no.I.97/19.

Crisosto CH (2002) Asian Pear – Postharvest Quality

Maintenance Guidelines. Dept. of Pomology, University

of California, Davis, CA 95616. Available on line at:

http: //postharvest.ucdavis.edu/producefacts.

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

bruck: Pinguin Verlag.

Dvor

k A, Vondra

ek J, Kala

ek J et al. (1978) Atlas Odru

Ovoce. Prague: SZN.

Ensminger AH, Ensminger ME, Konlande JE and Robsen

JRK (1995) The Concise Encyclopedia of Food and

Nutrition. Boca Raton, FL: CRC Press.

Koch V, Ferkl FR, Blattny

C et al. (1967) Hrus

ky. Prague:

Academia.

Kutina J, Kala

ek J, Blazˇek 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, Peka

rkova

E, Blazˇek J et al. (1994) Zahradnicky

Slovnı

k Nauc

. Prague: U

ZPI.

Mitcham EJ, Crisosto C and Kader AA (2002) Pear Anjou,

Bosc and Comice. Recommendation for Maintaining

Postharvest Quality. Available on line at: http://posthar-

vest.ucdavis.edu/producefact/fruit/pear2.html.

Senser and Scherz H (1991) Der Kleine ‘‘Souci Fachmann

Kraut’’. Lebensmitteltabelle fuer die Praxis, 2nd edn.

Stuttgart: Wissenchaftliche Verlagsgesellschaft.

Stehlı

´k

V, Trantı

´rek

J, Hrus

ka L et al. (1969) Nauc

Slovnı

´k

Zeme

lsky

1, 2. Prague: U

VTI-SZN.

PEAS AND LENTILS

G Grant and M Duncan, Rowett Research Institute,

Bucksburn, Aberdeen, UK

R Alonso and F Marzo, The Public University of

Navarra, Pamplona, Spain

Background

0001 Peas and lentils are potentially rich sources of macro-

and micronutrients and bioactive factors. This over-

view deals with the nutritional properties of the

seeds, possible physiological responses (detrimental

or beneficial) of animals to the constituent bioactive

compounds, and the effects of processing on nutri-

tional quality.

0002 Peas (Pisum spp.) and lentils (Lens spp.) have been

cultivated since around 6000–5000 bc, making them

amongst the earliest of the developed legume crop

plants. They are highly adaptable and can flourish

in a wide variety of habitats and environmental con-

ditions. As a result, they are grown in most regions of

the world and provide a staple source of dietary

protein and energy for a significant proportion of

the population.

0003 Much of the world output of peas and lentils

continues to be produced by traditional agricultural

methods, whereby they may be grown as part of a

crop rotation system or as secondary crops. Large-

scale intensive cultivation and industrial processing of

these legumes as foodstuffs do, however, occur in

some regions. Nonetheless, peas and lentils have

been at a commercial disadvantage to seeds such as

soyabean in that they do not contain significant

amounts of oil. This has limited their commercial

value. Protein and starch are the primary products

of cultivation of these seeds, whereas with soyabean,

they are essentially byproducts of vegetable oil pro-

duction and therefore comparatively inexpensive.

However, food production will need to increase

greatly to meet the requirements of a rising world

population. This is most likely to be met through

use of food sources that grow well in a wide range

of environments, in particular those that are adverse

to soyabean production. Peas and lentils are good

candidates for further development in this regard.

Furthermore, since many legume seeds contain bioac-

tive compounds that have been linked to health-pro-

moting effects, peas and lentils may have significant

health benefits in addition to being ready sources of

protein and energy.

Composition

0004Although peas and lentils are highly adaptable, their

actual composition varies greatly according to region,

climate, cultivar, and husbandry. The carbohydrate

levels may range between 525 and 740 g kg

1

, protein

between 156 and 355 g kg

1

, and lipid between 6 and

61 gkg

1

(Table 1). Intensively grown peas and lentils

have been developed and selected for yield and thus

are less variable in composition. In general, these

contain around 240–280 g protein per kilogram,

570–610 g of carbohydrate, about 100 g of lipid,

PEAS AND LENTILS 4433

and 250–300g of total dietary fiber. The protein and

lipid levels are far lower than those in raw soyabean

but are similar to the amounts found in other culti-

vated legumes, such as kidney beans. Carbohydrate

levels in peas and lentils are about double that in

soyabean, and the dietary fiber content can be two

to three times greater.

0005 The levels of individual amino acids in peas and

lentils also vary greatly according to region, climate,

and cultivar. Again, those in intensively cultivated

varieties are more consistent (Table 2). The average

amino acid profile of peas is close to the MIT (Mas-

sachusetts Institute of Technology) recommended

amino acid pattern for humans, but that of lentils

may be slightly deficient in the sulfur amino acids

and possibly tryptophan (Table 2). However, when

compared with the requirements for rats, the most

widely used experimental animal, both seeds

are deficient in a number of amino acids. The sulfur

amino acids are limiting, being present at 47–56% of

the requirements of rats. (See Amino Acids: Proper-

ties and Occurrence.)

0006 Pea proteins are readily extractable in neutral or

alkaline aqueous conditions. They are mainly of the

globulin type, with the 7S globulins (vicilin) tending

to predominate over the 11S globulins (legumin).

Lentil proteins are also mainly of the globulin type,

with legumin being the more prominent form. How-

ever, lentil proteins tend to be poorly soluble under

neutral or alkaline aqueous conditions if whole seed

meal is extracted. In contrast, solubility is high if the

lentils have been dehulled. This may be a result of the

removal of tannins present in the hulls. The globulin

proteins of both seeds generally have low contents of

the sulfur amino acids. In contrast, the levels in

albumin (water-soluble) fractions from these seeds

are quite high, owing to the presence of sulfur

amino acid-rich proteins such as the trypsin/chymo-

trypsin inhibitors.

0007Protein digestibility values for peas and lentils

in vivo are around 79–84%. This is similar to the

values obtained in vitro (80–84%) with activated

pancreatic extracts. However, digestibility values

in vitro are around 65–70% if purified digestive

enzymes are used. This discrepancy in vitro is likely

to be a result of slow or poor digestion of vicilins by

the pure enzymes. A similar difference was noted with

phaseolin from kidney bean. It was highly resistant to

pure proteolytic enzymes but readily degraded when

incubated with rat intestinal tissue plus contents.

Enzymes or factors, in addition to pepsin, trypsin,

and chymotrypsin, were shown to be necessary to

facilitate digestion of this protein. The nature of

these components is unknown. However, if add-

itional factors are crucial to promote degradation of

legume globulins, there is no guarantee that all

animals will possess them. There could therefore be

tbl0001 Table 1 Comparisonofgeneralcompositionandnutritional

valueofrawlegumeseeds

PeasLentilsSoyabeans

N(gkg

1

)23–5729–5755–82

Protein(gkg

1

)

145–355184–355343–512

Carbohydrate(gkg

1

)599–700500–697247–370

Lipid(gkg

1

)15–6215–25181–227

Totalfiber(gkg

1

)188–34789–30593–192

Crudefiber(gkg

1

)25–8825–5023–39

Ndigestibility(%)

79–8579–9277–82

Biologicalvalue(%)57–7231–5848–54

Netproteinutilization(%)45–6122–4638–44

Proteinefficiencyratio0.1–2.70.4–2.70.8–1.6

N6.25.

Proteindigestibilityandutilizationbyrats.

DatafromSavage(1988),SavageandDeo(1989),HuismanandJansman

(1991)NutritionAbstractsandReviews(SeriesB)61:902–921,Lusasand

Riaz(1995)JournalofNutrition125:573S–580S,Cuadradoetal. (2002)

JournalofAgriculturalandFoodChemistry50:4371–4376,Grantetal. (1999),

andAlonsoetal. (2000)JournalofAgriculturalandFoodChemistry48:2286–

2290,Alonsoetal. (2001)NutritionResearch21:1067–1077.

tbl0002Table 2 Comparisonoftheaminoacidcompositionof

cultivatedrawlegumeseeds

PeasLentilsSoyabeansAminoacid

needs

Human

Rat

Alanine

4.4–4.92.4–4.24.7

Arginine8.6–8.93.9–7.77.85.0

Asparticacid4.9–11.89.9–11.112.6

Cystine1.1–1.51.3–1.51.6

Glutamicacid12.2–17.115.5–16.319.4

Glycine4.4–4.84.1–4.44.6

Histidine2.2–2.41.3–2.82.72.5

Isoleucine3.1–4.14.0–4.34.93.55.0

Leucine7.2–8.37.0–7.28.16.58.0

Lysine7.2–8.24.3–7.06.75.06.0

Methionine1.0–1.10.8–1.11.32.5

4.5

Phenylalanine4.6–5.34.9–5.55.26.5

5.0

Proline4.1–4.92.6–4.25.9

Serine4.4–4.92.9–4.65.8

Threonine3.6–3.92.5–3.64.32.54.0

Tryptophan0.9–1.10.91.51.01.5

Tyrosine2.9–3.91.1–2.53.84.0

Valine4.7–5.53.0–5.05.03.55.5

Aminoacidasgper100gofprotein.

MIT pattern of human amino acid requirements. Journal of Nutrition 130.

1841S–1849S.

Combined sulfur amino acids.

Combined aromatic amino acids.

Data from Lusas and Riaz, (1995) Journal of Nutrition 125: 573S–580S,

Urbano et al. (1995) Journal of Agricultural and Food Chemistry 43: 1871–

1877, Alonso et al. (2000) Journal of Agricultural and Food Chemistry 48:

2286–2290, Alonso et al. (2001) Nutrition Research 21: 1067–1077 and USDA

databasewww.nal.usda.gov.

4434 PEAS AND LENTILS