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

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usually recommended to minimize the calcium sensi-

tivity of the pectin and avoidany risk of gelling. A slight

gelling of the product changes the rheology of the solu-

tion, resulting in undesirable pseudoplastic behavior.

For this reason, the most commonly used pectin is of

the rapid setting type. Pectin manufacturers usually

offer rapid-set pectins standardized to a viscosity in-

stead of gelling properties, so as to guarantee a consist-

ent performance in a beverage application.

Yogurt Drinks and Other Acidified Protein

Beverages

0037 From being largely restricted to certain regions or

addressed to specific consumer groups, acidified pro-

tein drinks today have become a highly esteemed and

popular food world-wide. Aided by the increased

focus on health benefits, the market for acidified

beverages with proteins is currently enjoying rapid

growth.

0038 Perfect stability and a consistent mouth feel are

essential to consumers, so the use of stabilizers is

necessary in order to prevent any defects such as sedi-

mentation, whey separation, and grainy mouth feel.

0039 At a low pH, the positive net charge of the protein

clusters in an acidified drink is insufficient to prevent

aggregation of the proteins, and the drink therefore

suffers from severe sedimentation of protein aggre-

gates and separation. This lack of physical stability is

even more pronounced if a shelf-stable, postpasteur-

ized product is desired as the unprotected proteins are

denatured by the heat treatment. Although specific

structural details vary, the same general stability

issues occur with various protein sources such as

casein, whey, soy, or other plant-derived proteins.

0040 The stability problem can be avoided by adding a

stabilizer such as a high-ester pectin. With its con-

trolled block structures of nonmethylated galacturo-

nic acid units, high-ester pectins can bind to the protein

surface as the blocks are negatively charged at a pH of

3.6–4.5, a typical level in acidified beverages. Bound to

the proteins, the long pectin molecules protect them

from reaggregation through steric stabilization. Even

with a postpasteurized drink, this stabilization can

produce a shelf-stable product and prevent unwanted

sedimentation and serum separation.

Yogurts and Other Dairy Products

0041 The gelling of low-ester pectins with calcium ions is

often used to set dairy products, but low-ester pectins

are also used to reinforce the texture of other types of

gel network such as the protein network in yogurts

and fermented dairy products. Recently, the trend

towards low-fat or non-fat dairy products has

increased the need to use textural ingredients and

stabilizers to restore a pleasant mouth feel and avoid

common defects such as syneresis.

0042Low-ester pectins can be dissolved in neutral milk

and are commonly used in the manufacture of gelled

neutral dairy desserts. Giving a softer texture with

more body and a high level of creaminess than widely

used carrageenan, pectin is preferred in premium

creamy formulations where the extra cost of pectin

can be justified. It is also used when carrageenan is

not desired on the label. In addition, pectin is the

main component of a variety of regional home-made

desserts formulations such as Fruche in Japan. Fruche

is a fruit and pectin solution sold in a pouch, which

the consumer can mix with milk. After half an hour in

the refrigerator, the gelled product can be consumed

as a refreshing dessert. In Europe, pectin is often seen

in dry mix blends for home-made desserts.

0043Whether the effect of low-ester pectins on the

texture of fermented dairy products comes through

gelation with calcium or interaction with proteins is

not quite clear. However, low-ester pectin is already

widely used on its own or together with gelatine or

starch to add texture to yogurts and other fermented

products.

0044Owing to the high level of calcium present, the

usage level of the pectin must be low in order to

avoid an excessively strong reaction between the

pectin and the calcium, resulting in a sandy product.

The maximum recommended usage level is around

0.25%. Interestingly, high-calcium-reactive pectins

usually show a better performance than their low-

calcium-sensitive counterparts. Amidated pectins are

usually preferred, even if conventional low-ester

pectins do prove useful in specific recipes for syneresis

control.

0045Pectin can also be used in combination with carra-

geenan for mousse products, where gelatine is not

desired. Pectin provides a much better gelation

after the mousse mix is whipped, leading to a more

sliceable texture compared with carrageenan alone.

Other Applications

0046Pectin is used in a great number of other applications.

For example, it is used in tomato-based products such

as barbecue or taco sauce as an alternative to starch.

Usually, low-ester conventional pectins are used to

thicken the sauce and ensure a nonmelting texture

when the sauce is poured over hot food.

See also: Dairy Products – Nutritional Contribution;

Gelatin; Jams and Preserves: Methods of Manufacture;

Chemistry of Manufacture; Soft Drinks: Chemical

PECTIN/Food Use 4455

Composition; Sweets and Candies: Sugar

Confectionery; Yogurt: Yogurt-based Products

Further Reading

Beli R. Thakur, Singh RK and Handa AK (1997) Chemistry

and uses of pectin – a review. Critical Reviews in Food

Science and Nutrition 37(1): 47–73.

May CD (1990) Industrial pectins: sources, production and

application. Carbohydrate Polymers 12: 19–99.

Rolin C and De Vries J (1990) Pectin. In: Harris P (ed.) Food

Gels, pp. 401–434. Amsterdam: Elsevier.

Walter RH (ed.) (1991) The Chemistry and Technology of

Pectin. London: Academic Press.

PELLAGRA

D A Bender, University College London, London, UK

Introduction

0001 Pellagra is a nutritional disease due to deficiency of

the vitamin niacin and the essential amino acid

tryptophan. The clinical features of pellagra are

dermatitis, diarrhea, and dementia; it is commonly

known as the ‘disease of the four Ds,’ since it is also

fatal – the fourth ‘D’ is death.

0002 During the first half of the twentieth century, pel-

lagra was a major problem of public health in the

southern USA, with some 87 000 deaths attributed

to the disease between 1900 and 1950. Through the

1950s to 1980s, it continued to be a problem in

southern Africa and parts of India, but improvements

in food availability and general nutritional status

have led to more or less complete eradication of pel-

lagra as an endemic nutritional deficiency disease.

0003 There have been a few reports of outbreaks of pel-

lagra among refugees in southern Africa when rations

have been inadequate to meet the demand, and indi-

vidual cases have been reported among alcoholics and

people with Crohn’s disease and other gastrointestinal

diseases that impair nutrient absorption.

0004 Pellagra may also occur as a result of a variety of

(relatively rare) conditions affecting tryptophan me-

tabolism and as a side-effect of a number of drugs that

inhibit tryptophan metabolism. In alcoholics, it is not

clear whether pellagra is the result of an impairment

of tryptophan and niacin metabolism directly attrib-

utable to alcohol, or whether it reflects general under-

nutrition among people who obtain a considerable

proportion on their energy needs from alcohol, and

hence have a low intake of (nutrient rich) foods.

0005 The first full description of pellagra was given by

Casal in 1735, working in Spain; he called it ‘mal de

la rosa’–the red disease. The name pellagra was

coined by Frapolli in 1771, from the Italian ‘pelle’

for skin and ‘agra’ for rough, thus describing the most

striking feature of the disease, the roughened appear-

ance of the skin, resembling severe sunburn in areas

exposed to sunlight. Casal recognized that the under-

lying cause of pellagra was nutritional, associated

with the limited diet of many in central Spain at the

time, although he did not associate it with the then

recent introduction of maize from Central America.

0006The spread of pellagra largely followed the intro-

duction of maize as a dietary staple, and by the nine-

teenth century, it was a major problem around the

Mediterranean, in the Balkans, and in the Ukraine, as

well as the southern USA and southern Africa. In

South Africa, pellagra became a problem following

the outbreak of rinderpest in 1897, which killed most

of the cattle, leading to a marked deterioration in the

diet of people who had previously had ample supplies

of milk and meat to supplement their maize-based

diet. In the USA, it was the social and economic

upheaval of the Civil War, which led to large numbers

of subsistence farmers living on a diet based very

largely on maize.

0007The other region where pellagra was a major prob-

lem is the Deccan plateau in India, where the dietary

staple is jowar (a variety of millet, Sorghum vulgare),

rather than maize.

0008Although Casal had described pellagra as a nutri-

tional disease, at the beginning of the twentieth

century it was generally assumed to be due to an

infectious agent. The nutritional basis of the disease,

and the interaction between deficiencies of both

niacin and tryptophan, was established mainly by

Goldberger and coworkers in the USA between

1913 and 1948. A ‘pellagra-preventing factor’ isol-

ated from protein-free yeast extract was shown in

1937 to be nicotinic acid, and either nicotinic acid

or its amide, nicotinamide, was shown to prevent or

cure the disease in both man and experimental

animals. The name niacin was coined when it was

4456 PELLAGRA

decided to enrich foods with the vitamin, since it

was considered that nicotinic acid would be un-

acceptable as a food additive, because of its chemical

(but not metabolic) relationship with nicotine. In the

USA, ‘niacin’ is commonly used to mean nicotinic

acid, and the amide is niacinamide; elsewhere,

‘niacin’ is used as a generic descriptor for nicotinic

acid and/or nicotinamide.

0009 Other early studies showed that feeding additional

protein, and especially the essential amino acid tryp-

tophan, would also prevent or cure pellagra, suggest-

ing that it was a protein-deficiency disease rather than

due to a lack of a vitamin. It was not until 1947 that

the problem was resolved, when it was shown that

tryptophan is a metabolic precursor of the nicotin-

amide moiety of the coenzymes nicotinamide adenine

dinucleotide (NAD) and nicotinamide adenine di-

nucleotide phosphate (NADP). The coenzymes can

be formed in the body either using preformed dietary

niacin or by de novo synthesis from tryptophan.

0010 The reason a maize-based diet predisposes to pel-

lagra is that the proteins of maize are particularly

poor in tryptophan, so that a diet in which there are

few other sources of protein provides insufficient

tryptophan for nicotinamide synthesis. Other cereals,

such as wheat, barley, rye, rice, and millet, contain

enough tryptophan to meet the requirement for niacin

synthesis.

0011 Although maize proteins are poor in tryptophan,

the other cereal associated with pellagra, jowar, pro-

vides a minimally adequate amount of tryptophan to

meet requirements. However, the proteins of jowar

are considerably richer in leucine than most other

proteins, and a diet based largely on jowar provides

a considerable excess of leucine. There is a consider-

able body of evidence that this amino acid imbalance

can be a precipitating factor in the development of

pellagra when the dietary intake of preformed niacin

is extremely low, and the intake of tryptophan is only

marginally adequate. Leucine inhibits kynureninase,

and hence reduces the rate of oxidative metabolism of

tryptophan, resulting in reduced formation of NAD.

In addition, leucine competes with tryptophan for

tissue uptake, and thus has a further inhibitory effect

on the rate of tryptophan oxidative metabolism and

NAD synthesis.

0012 All cereals contain preformed niacin. However, this

is largely present as a variety of nicotinoyl esters,

collectively known as niacytin, which are not hydro-

lyzed by digestive enzymes to any significant extent,

so that most of the niacin present in cereals is nutri-

tionally unavailable. A small proportion of the niacin

present as niacytin (up to about 10%) may be bio-

logically available as a result of nonenzymic hydroly-

sis by gastric acid.

0013Interestingly, pellagra has not been a problem in

Central America, the original home of maize. This is

because of the traditional way in which it is prepared.

Rather than milling the grain, it is steeped overnight

in limewater (calcium hydroxide solution), then

squeezed to form the dough from which tortillas are

made. This alkaline treatment results in hydrolysis of

most of the nicotinoyl esters, so releasing free nico-

tinic acid, which is nutritionally available. Although

maize spread to many countries following its discov-

ery, it was generally milled like other grains rather

than being treated in the traditional Mexican manner.

Clinical Features of Pellagra

Dermatitis

0014Exposure of the skin to modest amounts of sunlight

results in a severe sunburn-like dermatitis in sufferers

(pellagrins). Mechanical pressure can cause similar

lesions, especially around the wrists and ankles. The

skin in the affected areas is red and slightly swollen at

first, and then becomes rough, thickened, cracked,

and dry, with scaling, a shiny surface, and brown

pigmentation.

0015The cause of this photosensitive dermatitis in pel-

lagra is unknown and cannot be attributed to the

known metabolic functions of either tryptophan or

the nicotinamide nucleotide coenzymes. There is some

evidence that there is increased metabolism of the

amino acid histidine in the skin in pellagra, resulting

in a lower than normal concentration of both histi-

dine and an intermediate in its metabolism, urocanic

acid, both of which are believed to have a role in

absorbing ultraviolet light, and so minimizing

damage to the skin from exposure to sunlight. Treat-

ment of pellagrins with niacin both clears the derma-

titis and also increases the concentration of histidine

and urocanic acid in the dermis.

0016The skin lesions of pellagra may be due to second-

ary zinc deficiency when tryptophan intake is inad-

equate or its metabolism is disturbed; they resemble

the lesions seen in acrodermatitis enteropathica,

which is due to a failure to secrete the intestinal

zinc-binding ligand, which is believed to be picolinic

acid – a tryptophan metabolite. There is some evi-

dence that some pellagrins have a poor zinc status,

and the zinc depletion associated with excessive alco-

hol consumption may be a factor in the development

of pellagra among alcoholics.

Diarrhea

0017Although diarrhea is common in pellagrins, it is not a

constant feature of the disease, and indeed in some

PELLAGRA 4457

cases, there may be chronic constipation. The cause of

both the diarrhea and the constipation is almost

certainly general nutritional deficiency, resulting in

atrophy of the intestinal mucosa and the intestinal

musculature.

Dementia

0018 The psychiatric disturbances of pellagra range from

mild hallucinations with some psychomotor retard-

ation, through confusion with increasing hallucin-

ations, to severe dementia and anxiety psychosis,

with melancholia, intermittent stupor and possibly

epileptiform convulsions. In many ways, this resem-

bles schizophrenia, but the dementia of pellagra can

be differentiated from schizophrenia and the organic

psychoses by the sudden lucid phases that alternate

with the most severe mental symptoms.

0019 Although the cause of the psychiatric disturbance

in pellagra remains to be firmly established, it is likely

that it is largely due to deficiency of tryptophan, as

a precursor for the neurotransmitter serotonin

(5-hydroxytryptamine), rather than a direct result of

inadequate supply of the nicotinamide nucleotide

coenzymes in the brain.

The Equivalence of Dietary Tryptophan

and Niacin

0020 The nicotinamide ring of the coenzymes NAD and

NADP can arise either from preformed dietary niacin

or by de novo synthesis from quinolinic acid, an

intermediate in the oxidative metabolism of trypto-

phan. For an adult in nitrogen balance, the amount of

tryptophan available for oxidative metabolism is

about 99% of the dietary intake, since new synthesis

of protein is balanced by catabolism of tissue pro-

teins, releasing their tryptophan for metabolism. A

variety of studies have shown that under normal con-

ditions, 60 mg of tryptophan are equivalent to 1 mg of

preformed dietary niacin, and it is usual to express the

total niacin intake in terms of niacin equivalents – the

sum of preformed niacin plus 1/60 of the tryptophan.

On this basis, average Western diets provide more

than enough niacin to meet requirements from tryp-

tophan alone, ignoring preformed niacin. Indeed,

reanalysis of dietary records of people who died

from pellagra in the USA during the first half of

the twentieth century shows that their intake of

preformed niacin and tryptophan was (marginally)

adequate to meet requirements, suggesting that

some other factor may have been involved in

precipitating the disease.

Complicating Factors in the Etiology of

Pellagra

Deficiency of Vitamins B

and B

0021The enzyme kynurenine hydroxylase in the oxidative

pathway of tryptophan metabolism is a flavoprotein,

and hence its activity is impaired in riboflavin (vita-

min B

) deficiency. The enzyme kynureninase is

pyridoxal phosphate-dependent, and its activity is

impaired in vitamin B

deficiency. This means that

deficiency of either vitamin B

or B

will reduce the

rate of oxidative metabolism of tryptophan and hence

the rate of formation of quinolinic acid and NAD. If

the intake of tryptophan is anyway marginal, this

could well precipitate pellagra.

Mycotoxins

0022A number of mycotoxins cause DNA damage, and

activate poly(ADP-ribose) polymerase as part of the

DNA repair mechanism. This enzyme uses NAD as

the source of ADP-ribose, releasing nicotinamide.

While, theoretically, this nicotinamide could be

reused for synthesis of NAD, the enzymes involved

(nicotinamide phosphoribosyltransferase, nicotina-

mide deamidase, and nicotinic acid phosphoribosyl-

transferase) are all more or less saturated with their

substrates at normal tissue concentrations. This

means that the additional nicotinamide released by

poly(ADP-ribose) polymerase cannot be used for

NAD synthesis but will largely be methylated to N-

methylnicotinamide and excreted. Exposure to such

mycotoxins may therefore be a factor in the etiology

of pellagra, depleting the body of nicotinamide. The

one report of an outbreak of pellagra in Mexico was

associated with a shipment of maize that had suffered

considerable fungal damage.

Estrogens and Progestagens

0023Through the first half of the twentieth century, when

pellagra was a major problem in the southern USA,

there was a twofold excess of women over men among

those affected. In a number of reports of more recent

outbreaks, there is a similar sex ratio between the

menarche and menopause. There is no difference in

the numbers of males and females affected among

either prepubertal children or adults aged over

about 40 years. This suggests that estrogens and/or

progestagens may have a pellagragenic effect. Estro-

gen metabolites are competitive inhibitors of kynur-

eninase, and the administration of progesterone

results in reduced activity of kynurenine hydroxylase,

although in vitro, neither progesterone nor its conju-

gates affects the activity of kynurenine hydroxylase.

4458 PELLAGRA

When the intake of preformed niacin is low, and that

of tryptophan is marginal, the impairment of trypto-

phan metabolism by estrogens and progesterone may

be sufficient to precipitate pellagra more commonly

in women than men.

Non-nutritional Pellagra

0024 Pellagra can occur as a result of impairment of tryp-

tophan metabolism due to a variety of diseases that

affect the tryptophan oxidative pathway, or as a

result of drugs that inhibit one or more enzymes of

the pathway, despite an apparently adequate intake of

tryptophan. General malabsorption associated with

gastrointestinal disease; there have been a number of

case reports of pellagra among people with Crohn’s

disease. In most cases, the condition responds well to

supplements of nicotinamide.

Carcinoid Syndrome

0025 Under normal circumstances, about 1% of the daily

intake of tryptophan is metabolized by way of

5-hydroxytryptamine in the central nervous system

and gut, with the remainder being oxidized by

way of kynurenine, and thus available for NAD

synthesis. A carcinoid is a tumor of the enterochro-

maffin cells of the gastrointestinal tract, which forms

5-hydroxytryptamine from tryptophan. The carci-

noid syndrome occurs when the tumor has metasta-

sized, usually to the liver, and in extreme cases as

much as 60% of the daily intake of tryptophan may

be metabolized by way of 5-hydroxytryptamine. The

result is a considerable reduction in the rate of oxida-

tive metabolism through kynurenine, and hence a

considerable reduction in the synthesis of NAD

from tryptophan, resulting in the development of

pellagra in a significant proportion of patients.

Hartnup Disease

0026 Hartnup disease is an inborn error of metabolism

affecting the membrane proteins that transport the

large neutral amino acids (including tryptophan).

The same proteins are involved in the absorption of

free tryptophan from the gastrointestinal tract into

the bloodstream, from the bloodstream into tissues,

and in the reabsorption of amino acids from the urine.

The result of the defect is a considerable reduction in

the amount of dietary tryptophan that is absorbed, as

well as a considerable loss in the urine. Thus, despite

an apparently adequate intake, there is a deficiency of

tryptophan (and other large neutral amino acids),

resulting in the development of pellagra.

Inborn Errors of Tryptophan Metabolism

0027A number of inborn errors of metabolism affecting

enzymes of the tryptophan oxidative pathway have

been reported, all of which result in the development

of pellagra. Such conditions include much reduced

activity of tryptophan dioxygenase, the first enzyme

of the pathway; low or undetectable activity of kynur-

eninase and kynurenine hydroxylase; and increased

activity of aminocarboxymuconic semialdehyde

decarboxylase, the enzyme that competes with the

nonenzymatic cyclization of aminocarboxymuconic

semialdehyde to quinolinic acid, the precursor for

NAD synthesis.

Drug-induced Pellagra

0028A number of drugs can precipitate pellagra, despite

an apparently adequate intake of tryptophan. The

best-documented such drug is the antituberculosis

drug isoniazid (isonicotinic acid hydrazide), al-

though two antiparkinsonian drugs, Benserazide

and Carbidopa, are also associated with niacin de-

pletion. These drugs have an indirect effect on tryp-

tophan and niacin metabolism. They are hydrazine

derivatives that act as carbonyl-trapping reagents

and therefore cause depletion of vitamin B

forming inactive adducts with the metabolically

active form of the vitamin, pyridoxal phosphate.

Among other effects, this results in impaired activity

of kynureninase, and hence a reduced rate of trypto-

phan oxidative metabolism and NAD synthesis. Al-

though the pellagra responds to supplements of

nicotinamide, it is more usual to give supplements

of vitamin B

, at least in combination with isoniazid,

in order to minimize the other metabolic effects of

vitamin B

depletion.

0029Pellagra has also been reported among cancer

patients treated with a variety of chemotherapy

agents that cause strand breaks in DNA. This acti-

vates poly(ADP-ribose) polymerase as part of the

DNA repair mechanism, and so depletes tissue

NAD. Indeed, this is the mechanism of action of

these drugs; they deplete NAD in the tumor cells to

such an extent that there is severe impairment of

energy-yielding metabolism, leading to cell death. It

has been suggested that patients treated with such

chemotherapeutic agents should receive supplements

of niacin to protect against the development of

pellagra.

See also: Cereals: Contribution to the Diet; Dietary

Importance; Drug–Nutrient Interactions; Maize;

Mycotoxins: Toxicology; Niacin: Physiology; Vitamins:

Overview; Determination

PELLAGRA 4459

Further Reading

Bender DA (1983) Biochemistry of tryptophan in health

and disease. Molecular Aspects of Medicine 6: 101–197.

Bender DA (2003) Nutritional Biochemistry of the Vita-

mins, 2nd edition. Cambridge: Cambridge University

Press.

Bender DA and Bender AE (1986) Niacin and tryptophan

metabolism: the biochemical basis of niacin require-

ments and recommendations. Nutrition Abstracts and

Reviews (Series A) 56: 695–719.

Roe DA (1973) A Plague of Corn: the Social History of

Pellagra. Ithaca, NY: Cornell University Press.

PEPPERS AND CHILLIES

B Pickersgill, The University of Reading, Reading,

Berkshire, UK

Introduction

0001 Pepper and chilli have been used to designate many

different plants and plant products. This article is

concerned principally with Capsicum peppers, whose

fruits are consumed as a pungent spice or condiment

(chilli or cayenne peppers), or as a nonpungent vege-

table or source of color and flavor (sweet or bell

peppers, paprika, pimentos). Several species of Cap-

sicum were domesticated in the American tropics, but

C. annuum has outstripped all others in global im-

portance. The basic structure of the fruit is similar in

all types of Capsicum. However, variation in thick-

ness of the fruit wall and thickness of the cuticle

affects ways in which the fruits are harvested, handled,

and processed. The domesticated peppers vary even

more strikingly in the characteristics most valued by

humans: color, aroma, and pungency. Their fruits

have significant nutritional value, as well as medicinal

properties related to their pungency. World produc-

tion of both spice and vegetable peppers has increased

steadily throughout the last two decades.

Pepper, Chilli, Pimento, and Malagueta

0002 The European discoverers of the Americas often

named the novel plants they encountered on the

basis of real or perceived similarities to those with

which they were already familiar. The confusion thus

begun in the names associated with Capsicum still

persists.

0003 ‘Pepper’ is derived from a Greek word originally

used for black and white pepper, but subsequently

applied to genera belonging to seven different families

(Table 1), all of which have pungent fruits or seeds.

‘Chilli’ comes from one of the indigenous languages

of Mexico, where Capsicum has been consumed for

more than 5000 years. The Spanish spelling of this

word is ‘chile’. In the USA today ‘chile’ tends to be

used for the plant and its fruit, but ‘chili’ for a cooked

dish containing Capsicum and various other ingredi-

ents. ‘Chile powder’ thus signifies ground fruits of

Capsicum, but ‘chili powder’ also includes garlic,

onions, cumin, and other spices.

0004‘Pimento’ is derived from the Latin word for pig-

ment, and in medieval times signified spices in gen-

eral. Pimento is still used as an alternative name for

allspice (Table 1), but when applied to Capsicum,

‘pimento’ or ‘pimiento’ in English usage is usually

restricted to large red nonpungent fruits, sold canned

or used in processed foods.

0005The name ‘malagueta,’ used throughout much of

Latin America for an extremely pungent small-fruited

Capsicum, has also been borrowed from an Old

World spice and is used for two unrelated genera in

the American tropics (Table 1).

Botanical Background

0006Capsicum belongs to the family Solanaceae, which

also includes tomato, eggplant (aubergine), and

potato. (See Potatoes and Related Crops: Fruits of

the Solanaceae; Tomatoes.) Capsicum contains

about 20 species, all confined to the Americas until

Columbus’ discovery of the New World. In the Amer-

icas, human selection produced much variation in the

fruits. Many of these variants were formerly regarded

as distinct species, but now only five domesticated

species are generally recognized: C. annuum, C. fru-

tescens, C. chinense, C. baccatum, and C. pubescens.

Each was domesticated independently, but contains a

similar range of variation in fruit characters.

0007The bell peppers, paprikas, and pimentos, together

with most of the Mexican chillies, are all included in

C. annuum. This is now the most widespread, and

economically the most important, of all the cultivated

species of Capsicum. There is disagreement over

whether C. frutescens is or is not a species distinct

from C. annuum. If it is considered distinct, then the

4460 PEPPERS AND CHILLIES

cultivar ‘Tabasco’, which is the main ingredient of

tabasco sauce, belongs in C. frutescens. In Mexico

and Central America, wild forms of both species are

often lumped together as bird pepper (also known as

chile piquin or chiltepin).

0008 The most common cultivated pepper of the West

Indies and much of South America is C. chinense,

which is closely related to C. annuum and C. frutes-

cens but has a distinctive aroma and flavor. Habanero

and Scotch Bonnet types (the latter named from the

shape of the fruit) are now finding specialty markets

in some developed countries. Nonpungent forms of

C. chinense are grown commercially in Amazonia,

where C. annuum does not succeed, and may prove

suitable for other parts of the humid tropics.

0009 The remaining two domesticated species are virtu-

ally unknown outside the Americas. C. baccatum is

widespread in Andean South America and southern

Brazil. The rocoto, C. pubescens, is another Andean

species, easily recognized by its dark seeds.

Morphology and Anatomy of the Fruits

0010 The fruit of Capsicum is a berry, which is unusual in

being hollow, not filled with pulp as in tomato. In

wild peppers, the very pungent small red fruits are so

palatable to birds that ripe fruits are rarely found. As

the fruits ripen, an abscission layer develops between

the base of the fruit and the calyx, so birds can readily

remove mature fruits from the plant. In domesticated

peppers, this abscission layer does not develop, so the

fruits remain on the plant until harvested by humans.

Domesticated peppers may have much larger fruits

than wild peppers, and may be pungent, mild, or

nonpungent. Size and pungency are genetically inde-

pendent characters, so small nonpungent fruits and

very pungent large fruits can and do occur. Fruits of

domesticated peppers have various shapes, described

by local names such as girl’s finger, dog’s penis, fish

eye, and friar’s hat. In some European countries,

sweet peppers always have pointed fruits, while in

others, ‘blocky’ types that can be stood on the stylar

end and stuffed from the stalk end are preferred.

0011In all Capsicum fruits, an outer wall or pericarp

surrounds an inner cavity that contains the seeds.

Fruits that are used fresh have a thick pericarp,

whereas fruits that are used dry or after grinding

have a thinner pericarp. Water loss from the pericarp

is retarded by an impermeable outer cuticle, which is

indigestible and may be tough, but accounts for the

relatively long shelf-life of the vegetable peppers. The

cuticles of pimentos are removed before canning,

but cuticles of bell peppers are not usually removed,

so human selection for palatability has produced thin-

ner cuticles in bell peppers than in pimentos. When

the fruits are used dried, those that lose moisture

quickly without becoming wrinkled or unattractive

in appearance are preferred. These fruits thus also

often have thin cuticles.

0012A layer of so-called giant cells immediately under

the inner epidermis of the pericarp gives the inner

surface of the fruit wall a characteristic blistered ap-

pearance which may help to distinguish fragments of

Capsicum pericarp from other contaminants in the

ground spice. The function of the giant cells is not

known, but they are not associated with pungency.

tbl0001 Table 1 Botanical identities, geographic origins, and uses of plants for which the names pepper, pimento, and malagueta have been

used

Scientific name Common names Origin Uses

Anacardiaceae (mango, cashew, pistachio family)

Schinus molle Pepper tree, pink peppercorn Andes Condiment

Annonaceae (custard apple family)

Xylopia aethiopica Guinea pepper, African grains Tropical Africa Spice

Xylopia spp. Malagueto, pimenta de macaco (monkey pepper) Tropical America Condiment

Myrtaceae (clove, guava, eucalyptus family)

Pimenta dioica Jamaica pepper, pimento, allspice Caribbean Spice

Piperaceae (pepper family)

Piper nigrum Black, white, green pepper(corns) India Condiment

Solanaceae (potato, tomato, tobacco family)

Capsicum spp. Red pepper, chilli pepper, capsicum, aji, malagueta American tropics Spice and condiment

Capsicum annuum

(nonpungent cultivars)

Sweet, bell, green or red pepper, pimento, mango (USA) Mexico Vegetable

Rutaceae (citrus family)

Zanthoxylum spp. Szechuan pepper, Chinese prickly ash Far East Condiment in Chinese

cookery

Zingiberaceae (ginger, cardamom, turmeric family)

Aframomum melegueta Melegueta pepper, grains of paradise, guinea grains West Africa Spice, especially for

alcoholic drinks

PEPPERS AND CHILLIES 4461

0013 In small-fruited chilli peppers, there are two cham-

bers, or carpels, separated by an inner wall, or septum.

The seeds are attached to a spongy tissue called the

placenta that develops from the septum. Large fruits

are often formed from more than two carpels, and

therefore have additional septa. The septa are better

developed at the stalk end of the fruit, and often fail

to reach the tip, so most of the seeds are borne on a

hemispherical placenta at the stalk end of the single

cavity in the fruit.

Special Characteristics

0014 Quality of pepper fruits, and of the products made

from them, depends on their color, aroma, and pun-

gency. Hot peppers also have certain well-known

pharmacodynamic effects. Nutritionally, both hot

and sweet peppers are valuable sources of vitamins.

Color

0015 The middle layer or mesocarp of the fruit wall is

responsible for the color of both ripe and unripe

fruits. The cells of the mesocarp contain plastids,

which in the unripe fruit usually contain chlorophyl.

The quantity of chlorophyl varies in different culti-

vars. Occasionally chlorophyl is absent and the

unripe fruits are creamy white. Immature fruits may

also contain sap-soluble, purple anthocyanin pig-

ments. As the fruit ripens, both chlorophyl and antho-

cyanin usually disappear. Chloroplasts are converted

to chromoplasts, and additional chromoplasts form

de novo. There is a relationship, not yet fully under-

stood, between chlorophyl content of the unripe fruit

and carotenoid content of the ripe fruit. Immature

fruits that lack chlorophyl may ripen red, but the

red is deepest in fruits that are dark green when

unripe. (See Chlorophyl; Colorants (Colourants):

Properties and Determination of Natural Pigments;

Ripening of Fruit.)

0016 As a red pepper ripens, total carotenoids increase

35-fold and are sequestered within fibrils in the chro-

moplasts. About half of this increase represents de

novo synthesis of red pigments. These consist of

three ketocarotenoids: capsanthin (30–60% of total

carotenoids present), capsorubin (5–15%), and cryp-

tocapsin (about 5%). They are unusual in containing

the cyclopentanol ring, unlike red carotenoids of

fruits such as tomato (which accumulates lycopene).

Lycopene is thought to be an intermediate in the

biosynthesis of capsanthin and capsorubin (Figure 1).

0017 Although the carotenoid pigments are formed in

the chromoplasts, the quality and quantity of these

pigments, which determine the different colors of the

mature fruit (Table 2), are controlled by genes located

on the chromosomes, not in the plastids. Fruits of the

yellow color series cannot synthesize red carotenoids.

In C. annuum, yellow-fruited plants carry a deletion

of the DNA that codes for the enzyme capsanthin-

capsorubin synthase, which catalyzes the final step in

the production of capsanthin and capsorubin. Reces-

sive alleles of other nuclear gene(s) reduce the quan-

tities of pigments in the fruits, but we do not know

where or what these blocks to pigment synthesis may

be. Chocolate-brown fruits, such as those used in the

famous Mexican sauce mole, are homozygous reces-

sive for an allele of another nuclear gene, which pre-

vents chlorophyl breakdown in the ripe fruit. The

combination of red carotenoids and green chlorophyl

appears as brown.

0018Breakdown of the red pigments in harvested fruits,

or in powders produced by drying and grinding these

fruits, is not prevented by blanching, but is retarded

by antioxidants. This suggests that pigment break-

down is not due to enzyme action, but may involve

two other processes: an autoxidative degradation

which is accelerated by heat, and an autocatalytic

destruction in light which involves direct absorption

of light energy.

Aroma

0019Droplets of volatile oil in the mesocarp cells produce

the characteristic aroma of the pepper fruit. These

droplets increase in quantity as the fruit ripens. The

oil is a mixture of methoxypyrazines, aliphatic alco-

hols, and esters, in which the most important con-

stituent is 2-methoxy-3-isobutylpyrazine. This has

one of the lowest odor thresholds of any compound

examined, being detectable at levels of 2 parts in 10

parts water. Methoxypyrazines have also been

reported from other vegetables such as raw potato

and French bean, but at much lower levels than in

Capsicum.(See Sensory Evaluation: Aroma.)

0020The aliphatic alcohols and esters seem to be re-

sponsible for the fruity and floral components of the

aroma. Although aroma is a valued attribute of fresh

chillies, and the different aroma and flavor properties

of different chillies are usually well-known to habit-

ual consumers, little is known about differences in

composition of the volatile oil either within or be-

tween different species of Capsicum.

Pungency

0021Some botanists have used pungency of the fruits to

distinguish Capsicum from allied genera. The bio-

logical significance of pungency is not known, but

the sensory effect is produced by a group of vanillyl

amides collectively known as capsaicinoids (Table 3),

amongst which capsaicin and dihydrocapsaicin

4462 PEPPERS AND CHILLIES

predominate. Capsaicin is insoluble in cold water but

soluble in alcohol, acetone, ether, and similar solv-

ents. It is one of the most pungent compounds known,

detectable by taste at dilutions of 1 in 15–17 million.

Pungent compounds are also present in other plants,

for example, ginger and black pepper (Table 3). The

capsaicin molecule has three characteristic features:

the vanillyl group, the acid–amide linkage, and the

alkyl side-chain. Change in any one of these decreases

pungency. Piperine from black pepper lacks the vanil-

lyl group and has a short side-chain with a bulky

substituent. Its pungency is more than two orders

below that of capsaicin. Gingerols and shogaols,

from ginger, have a vanillyl group and a long alkyl

Isopentenyl pyrophosphate

(IPP)

Dimethylallyl pyrophosphate

IPP

GGPP

Phytoene

Lycopene

γ-Carotene

β-Carotene

Zeaxanthin

Antheraxanthin

Capsanthin Capsorubin

Violaxanthin

Geranyl pyrophosphate

Farnesyl pyrophosphate

Geranylgeranyl pyrophosphate

(GGPP)

Stroma of

chromoplast

Membranes of

chromoplast

fig0001 Figure 1 Biosynthesis of carotenoid pigments in fruits of Capsicum. Modified from Camara B, Hugueney P, Bouvier F, Kuntz M and

Mone

ger R (1995) Biochemistry and molecular biology of chromoplast development. International Review of Cytology 163: 175–247, with

permission.

PEPPERS AND CHILLIES 4463

chain, but lack the acid–amide bond and thus are also

much less pungent than capsaicin. The length of the

alkyl side-chain has been varied experimentally in

synthetic analogs of capsaicin. Pungency appears

first in compounds with a six-carbon side-chain,

peaks with the nine-carbon side-chain, then gradually

declines as chain length increases. The synthetic nine-

carbon analog, N-vanillylnonamide, has been used as

a substitute for capsaicin.

0022Biosynthesis of capsaicinoids is thought to involve

one pathway from phenylalanine to vanillylamine,

and one from valine or leucine to their respective

isoacids, followed by condensation of vanillylamine

with the activated fatty acids. Two capsaicinoid-like

compounds (capsiate and dihydrocapsiate) have been

identified from a nonpungent Japanese cultivar of

C. annuum. These compounds have an ester moiety

in place of the amide moiety of capsaicin and

tbl0003 Table 3 Structure and pungency of capsaicinoids compared to pungent principles of ginger and black pepper

Name Structural formula Thresholdpungency

(10

Scoville units)

N-vanillyl alkyl amides (from Capsicum)

Capsaicin

(CH

)

NH CO CH CH CH(CH

)

160

Dihydrocapsaicin

(CH

)

NH CO CH(CH

)

160

Nordihydrocapsaicin

(CH

)

NH CO CH(CH

)

Homodihydrocapsaicin

(CH

)

NH CO CH(CH

)

Homocapsaicin

(CH

)

NH CO CH CH CH(CH

)

N-vanillylnonamide

(CH

)

NH CO CH

N-vanillyl alkyl ketones (from ginger)

Gingerol

(CH

)

CO CH(OH)

0.8

Shogaol

CHCH

(CH

)

CO CH

1.5

Substituted piperidine (from black pepper)

Piperine

NCOCH CH

CH CH

1.0

tbl0002 Table 2 Effects of pigment quality and quantity on color of the

ripe fruit in Capsicum

Pigment quantity Pigment quality

Red pigments present Red pigments absent

Normal Red Orange-yellow

Slightly reduced Tangerine Lemon yellow

Trace amounts only Pink Cream

4464 PEPPERS AND CHILLIES