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

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0028 Being parthenocarpic (seedless, but otherwise nor-

mal), pineapple propagation is vegetative and can be

problematical as only limited planting material is

available from any one plant. The best planting ma-

terial, that producing the most uniform plants and

fruits, is the fruit crown, but if the fruit is sold as

fresh fruit (as opposed to canning), tops are not avail-

able, so that suckers and other vegetative material

must be collected and used. Up to 80 000 pieces of

planting material (tops, suckers or slips) are required

per hectare, planted in double rows. The time of

planting and the size and type of planting material

affect the date of harvest and fruit size, and are pre-

determined. Weeds can be readily controlled as the

plant is resistant to several effective herbicides (e.g.,

diuron, fluazifopbutyl, ametryne) which are applied

over the rows of growing plants with a boom spray.

Ten to fourteen months after planting, a flower-

inducing hormone (commonly the ethylene-releasing

compound Ethrel, 2-chloroethyl-phosphonic acid) is

applied, and the treated plants uniformly produce a

single, blue-petalled inflorescence about 8 weeks

later. Fruit development occurs without further inter-

ruption, but as sunburn can be a serious injury, fruit

may be individually covered (bagged) or sprayed with

a reflective bentonite clay suspension.

0029 Harvesting pineapples at the correct stage of

internal ripeness is important as it is the major factor

that determines the fruit quality at consumption. As

skin color is an inconsistent guide to eating quality,

pickers have to use past experience and market

demands.

0030Sodium naphthaleneacetic acid (NAA) is some-

times applied as a spray on the fruit to increase

fruit size by delaying degreening (becoming yellow).

Adverse effects on fruit quality from using NAA are

reportedly minor but are under current debate. Ethrel

is also sometimes sprayed on both fresh and cannery

crops to increase flesh yellowness and to ‘accelerate

ripening.’ While very effective and cost-saving on

cannery fruit, its use on fresh-market fruit has been

shown to be of questionable value as the variability of

the eating quality is greatly increased.

See also: Canning: Quality Changes During Canning;

Controlled-atmosphere Storage: Applications for Bulk

Storage of Foodstuffs; Freezing: Structural and Flavor

(Flavour) Changes; Fruits of Tropical Climates:

Commercial and Dietary Importance; Fungicides;

Ripening of Fruit

Further Reading

Bartholomew DP and Paull RE (1986) Pineapple. In: Mon-

selise SP (ed.) Handbook of Fruit Set and Development,

pp. 371–388. Boca Raton, Florida: CRC Press.

Dull GG (1970) The pineapple: general. In: Hulme AC (ed.)

The Biochemistry of Fruits and their Products, vol. 2,

pp. 303–324. London: Academic Press.

Py C, Lacoeuilhe JJ and Teisson C (1987) The Pineapple:

Cultivation and Uses. Paris: GP Maisonneuve et Larose.

Smith LG (1988) Indices of physiological maturity and

eating quality in Smooth Cayenne pineapples. Queens-

land Journal of Agricultural and Animal Sciences 45(2):

213–228.

PINE KERNELS

B T Styles

, University of Oxford, Oxford, UK

Background

0001 Pine nuts, also known as Indian nuts, pin

ons, or pigno-

lias, have been an important food crop in some areas

of the world since prehistoric times. The ‘nut’ is, in

fact, the seed of different species of pine (Pinus), nearly

all of which belong to a group known as ‘soft’ or

‘white’ pines or their relatives. These species are ever-

green, coniferous trees whose cones are softly woody

and have few scales and two large seeds per scale that

lack a wing (see Figure 1). The kernel consists of the

endosperm tissue of the seed containing the stored

food material and the developing embryo (germ).

The ‘shell’ surrounding it is the testa. This must be

removed before the kernel can be eaten.

Sources

0002Pine nut kernels are almost all obtained from wild

forest trees. Pin

ons from the drier areas of southwest

USA and Mexico form the largest wild source, but the

Italian pignolia tree has been cultivated and protected

in the Mediterranean region for centuries. Almost all

the other species grow in upland mountainous areas,

but information about them is scanty (Table 1). The

harvest of pine nuts is only a fraction of the produc-

tion of cultivated nuts such as pecan, macadamia,

walnut, or filbert, and the crop is generally irregular,

with bumper harvests occurring approximately every

Deceased.

PINE KERNELS 4575

5 years. Harvesting is chiefly by an itinerant labor

force that moves into the pine forests during the

autumn. Green cones are cut from the trees, dried in

the sun and opened to release the seeds, or the seeds

are collected from beneath the trees. The collection

and later preparation can at best be considered as a

cottage industry. The kernels of only two or three of

the pin

on pines and the pignolia pine are important in

commercial trading on a large scale. They may be

bought in health food shops or delicatessens but are

considered expensive, £12.50 per kilogram in the UK.

0003Kernels of most of the other pines may be found on

sale in local markets near the site of collection. There

are no reliable statistics on yields of these wild crops,

but it has been estimated that about a million kilo-

grams of Colorado pine nuts were collected annually

in southwest USA. This quantity has probably not

changed a great deal since then.

Storage and Preparation

0004After harvesting, nuts should be kept unshelled, in a

dry, cool, well-ventilated place in cloth or paper bags.

Tannins in the shell and in the seed coat of the kernel

may function as antioxidants in preserving the fat and

oil in the nuts. Fresh kernels stored in closed containers

soon go moldy or rancid, but after drying, they can be

safely preserved and have excellent keeping qualities

for up to 3 years. They freeze well when fresh. Shelling

of the nuts can be done domestically by lightly crush-

ing the nuts on a cloth with a rolling pin. Those of the

thin-shelled, single-leaf pine can be easily removed

with the fingers. The thicker Colorado pin

on, stone

pine, and pignolia nuts must be cracked mechanically

to release the kernels. (See Antioxidants: Natural

Antioxidants; Oxidation of Food Components.)

0005Although the kernels can be eaten raw, roasting is

necessary to bring out their full flavor. They may be

roasted with or without the shell, the amount of time

required depending on shell thickness and moisture

content.

Composition and Nutritional Value

0006The richness and flavor of pine kernels are well known,

and they rank highly among all other nuts in food

value. There are, however, considerable differences in

the properties of the kernels of different species. A

comparison of the nutritional value of pine kernels

and some commercial nuts is provided in Table 2.

Refuse and Wastage

0007When compared with other nuts, pin

ons have low

percentages of shell waste or refuse. Shell thickness

tbl0001 Table 1 Sources of pine kernels (Pinus species and their

distribution)

Group Latinname Distribution

Pion pines Pinus edulis Southwestern states of

USA and Mexico

P. monophylla

P. q u a d r i f o l i a

P. maximartinezii Mexico

P. cembroides

Stone pines

Italian (pignolia) P. p i n e a Mediterranean basin and

Turkey

Japanese P. p u m i l a Northeast Asia, Siberia to

Korea and Japan

Korean P. koraiensis Korea, southeast Siberia

and Japan

Siberian P. siberica Western Russia to Siberia

and Mongolia

Swiss P. c e m b r a Alps and Carpathian

Mountains

Chilgoza pine P. gerardiana Eastern Afghanistan to

northern India and

Pakistan

(a)

(b)

(c)

fig0001 Figure 1 Pignolia (Pinus pinea): (a) cone; (b) seeds; (c) polished

kernels (all natural size). Reproduced from Pine Kernels, En-

cyclopaedia of Food Science, Food Technology and Nutrition,

Macrae R, Robinson RK and Sadler MJ (eds), 1993, Academic

Press.

4576 PINE KERNELS

varies considerably: 30–35% of seed weight of the

very-thin-shelled single-leaf pin

on is made up of shell,

whereas the thicker-shelled Colorado pine has a

waste factor of 42%. Mediterranean pignolia has a

particularly thick shell that must always be removed

before it is sold. Thus, pine kernels of pin

ons consti-

tute some 58–70% of the edible portion. The average

is lower than that found in all other commercial nut

crops except peanuts.

Protein

0008 The average protein content is about 15% for pin

nut kernels and about 34% for pignolias. It is higher

than for pecan nuts and about the same as that for

English walnut and Brazil nut. It is only greatly

exceeded by peanuts. A study in the former Yugo-

slavia has shown that kernels of pignolias are richer

in proteins than pork and goose meat. Kernel protein

has a digestibility value almost as good as that of beef

and is distinctly better than almost all other nuts. It

is near the proportion required for a balanced diet.

Colorado and single-leaf kernels are especially rich in

tryptophan and cystine. (See Protein: Requirements.)

Fat (Lipid) and Oil

0009 Pin

on pine kernels average about 60% of fatty mater-

ials. This is lower than pecan, English walnut, and

Brazil nut, which approximate to 70%. Pignolia

kernels in the former Yugoslavia are reported to con-

tain 48% of lipid, which is again higher than for fat

pork (37%) and goose meat (44%). As Table 2 indi-

cates, the Siberian stone pine is also very rich in fats

and oil. This is processed commercially for the pro-

duction of cooking oil, but no published details of

production methods or quantities are available. The

fats of pin

ons, particularly Colorado and single-

leaved pine, contain monounsaturated oleic, and poly-

unsaturated linolenic and linoleic acids. It has been

reported that pignolia kernels from the Mediterranean

region contain up to 50% of linoleic acid. Commer-

cially produced pine kernels studied contained 46.40 g

of fat by weight, of which 6.12 g is saturated (fatty acid

not named). (See Fats: Requirements.)

Carbohydrate

0010The average oily pin

on kernel of Colorado pine con-

tains 19% carbohydrate, but this can increase to as

high as 54% in the more starchy kernels of the single-

leaf pine. In the Parry pine, it is 44%, but the former

is much preferred. (See Carbohydrates: Requirements

and Dietary Importance.)

Other Substances

0011Pine kernels are extremely rich in phosphorus

(6040 mg kg

1

) which is about the same as for soya

bean, and iron (53 mg kg

1

). They also contain sig-

nificant amounts of vitamin A, thiamin, riboflavin,

and niacin. Refer to individual nutrients.

Uses

0012In the past, pine kernels were a staple component

in the diet as well as a subsistence food, but because

of their enormous versatility, they now hold a high

profile in modern cuisine among people of the de-

veloped nations, particularly in the USA, Europe,

Asia, and North Africa. As roasted nuts, they are

very widely used in the preparation of soups, sauces,

and dressings, and may be served as a garnish for fish

meals, in mixtures with cooked meat and as part of

side-dishes with rice. They form suitable ingredients in

cakes, puddings, and biscuits, and as a garnish for

icecream. They are also highly appreciated in fruit

desserts and vegetable salads. The kernels are so nutri-

tious that a number of recipes have recently appeared

under the label of ‘Backpackers’ Friends.’ These

products bear such names as Pin

on Pemmican and

Granola, and may be carried as bars in the rucksack

as emergency rations or snacks. Pine kernels will

probably become even more popular as the rise in

vegetarianism continues.

See also: Antioxidants: Natural Antioxidants;

Carbohydrates: Requirements and Dietary Importance;

Fats: Requirements; Oxidation of Food Components;

Protein: Requirements

tbl0002 Table 2 Comparison of the nutritional value of pine kernels and

some commercial nuts

Type of nut Food content

Protein

(%)

Fat

(%)

Carbohydrate

(%)

Colorado pi•on, Pinus edulis 14 62–71 18

Single leaf pin

on, P. monophylla 10 23 54

Mexican pin

on, P. cembroides 19 60 14

Parry pin

on, P.  quadrifolia 11 37 44

Digger pine, P. s a b i n i a n a 30 60 9

Pignolia pine, P. p i n e a 34 48 7

Siberian stone pine, P. siberica 19 51–75 12

Chilgoza pine, P. g e r a r d i a n a 14 51 23

Pecan, Carya illinoensis 10 73 11

Peanut, Arachis hypogaea 26 39 24

English walnut, Juglans regia 15 68 12

Almond, Prunus dulcis 21 54 7

Brazil nut, Bertholletia excelsa 16 69 8

Typical energy value per 100 g ¼556 kcal.

Data from Lanner RM (1981) The Pion Pine. Reno, Nevada: University of

Nevada Press and Botkin CW and Shires LB (1948) The Composition and

Value of Pion Nuts. Bulletin 344, New Mexico Experiment Station.

PINE KERNELS 4577

Further Reading

Botkin CW and Shires LB (1948) The Composition and

Value of Pin

on Nuts. Bulletin 344, New Mexico Experi-

ment Station.

Budzynska J (1964) Note sur la composition en acides gras

de l’huile des noix de Pinus pinea. Revue Franc¸aise des

Corps Gras 11: 143–145.

Kaic M (1985) Prehrambenotenoloske osobine sjemenki

oraha (Juglans regia), crnog oraha (Juglans nigra) i pinije

(Pinus pinea). Sumarski List 109: 325–328.

Lanner RM (1981) The Pin

on Pine. Reno, Nevada: Univer-

sity of Nevada Press.

Little EL (1938) Food Analyses of Pin

on Nuts. Research

notes, Southwestern Forest and Range Experiment

Station, Arizona.

Rowe DB, Blazich FA and Weir RJ (1999) Mineral nutrient

and carbohydrate status of loblolly pine during mist

propagation as influenced by stock plant nitrogen

fertility. Hortscience 34: 1279–1285.

Siew WL (2001) Crystallisation and melting behaviour of

palm kernel oil and related products by differential scan-

ning calorimetry. European Journal of Lipid Science and

Technology 103: 729–734.

Zakaria S, Hamzah H, Murshidi JA and Deraman M

(2001) Chemical modification on lignocellulosic poly-

meric oil palm empty fruit bunch for advanced material.

Advances in Polymer Technology 20: 289–295.

Pituitary Hormones See Hormones: Adrenal Hormones; Thyroid Hormones; Gut Hormones; Pancreatic

Hormones; Pituitary Hormones; Steroid Hormones

PLANT ANTINUTRITIONAL FACTORS

Contents

Characteristics

Detoxification

Characteristics

G D Hill, Lincoln University, Canterbury, New Zealand

Background

0001 The growing of plants as a major food source for

humans only started about 10 000 years ago with

the birth of agriculture. At that stage, human inter-

vention disrupted the chain seed – plant – seed.

Because the seeds, tubers, and fruits of a number of

plant species are rich in carbohydrates, protein, and

fats, plant materials now provide a substantial

proportion of the food energy that is consumed by

humans and their domestic animals. When that

process happened, a number of chemical compounds

occurring naturally in plants, and often with a role in

protecting the plant from attack by animals – be they

insect, ruminant herbivore, or monogastric – became

antinutritional factors (ANFs).

0002 Other articles will deal in detail with most of these

ANFs, which are sometimes called secondary metab-

olites. This chapter will consider the plant species

involved and their interaction with animals and

humans when they are eaten. The chapter will also

consider briefly how the effects of ANFs can be over-

come. It will not cover their exact chemical structure,

their determination, or their biosynthesis.

Plant Antinutritional Factors

Antigens

0003A number of legume species, but particularly soybean

(Glycine max) and peanut (Arachis hypogaea), pro-

duce severe antigenic reactions in both people and

animals. Affected persons can go into anaphylactic

shock, and unless treatment is quickly applied, death

can follow. In a recent case in the USA, a person who

was allergic to peanuts died after licking his fingers

having touched a chicken leg coated with peanut

sauce. Similarly, some airlines now have peanut-free

flights. Other plant foodstuffs that are reported

to induce allergenic reactions include rice (Oryza

sativa), hazelnuts (Corylus avellana), apples (Malus

sylvestris), and celery (Apium graveolens).

4578 PLANT ANTINUTRITIONAL FACTORS/Characteristics

0004 Compounds responsible The proteins that are

thought to be responsible for the development of

allergenic reactions are generally water-soluble

glycoproteins that are resistant to breakdown by

heat, acid, and digestive enzymes. In soybean and

peanuts, the glycoproteins are thought to be the stor-

age proteins, glycinin and b-conglycincin. These pro-

teins resist digestion and are absorbed into the

intestinal mucosa. The body responds by producing

immunoglobulins or antibodies in the Peyer’s patches

of the gut and their associated lymphoid tissue. These

antibodies are then released into the gut and react

with the antigens to prevent their absorption. Anti-

gens that escape absorption cause inflammation of

the intestinal mucosa.

0005 Three mechanisms are involved. An immediate

mechanism that involves IgE antibodies and mast

cells (type I hypersensitivity), semidelayed, which

is brought about by antigen–antibody complexes

(type III), and delayed caused by specific activated

T-lymphocytes (type IV). The last is so called because

there can be a delay of several days between the

antigen challenge and the onset of observable

symptoms. (See Food Intolerance: Food Allergies.)

0006 Symptoms Affected animals show poor growth and

diarrhea, and may die. In the gut, there are changes in

the structure of the mucosa, increased gut motility,

and reduced absorption of electrolytes (Na

, and



). Once animals are sensitized, they can remain so

for a considerable period. In laboratory animals,

chronic stimulation by antigens has given reduced

disacchiridase activity, reduced surface area of the

brush borders of the microvilli, reduced microvilli

height, crypt hyperplasia, cell degranulation, and

increased numbers of mast cells.

0007 Minimization of problems In humans, the develop-

ment of food allergies seems to be related to age.

Among young children, up to 8% can suffer from

food allergies. In adults, the rate of occurrence is

considered to be < 1%. Thus, as people get older,

they seem to be less prone to the development of

food allergies. Where products such as soybean are

used as milk substitutes, it is possible to treat the

material by procedures such as steam heating to

reduce the level of antigenicity.

a-Galactosides

0008 It is probably not strictly correct to refer to the a-

galactosides as ANFs, as they are not toxic. However,

their presence in plant foods can cause severe digest-

ive upsets in monagastrics that are embarrassing in

humans and can lead to severely reduced growth rates

in animals such as pigs.

0009Compounds responsible The a-galactosides or

oligosaccharides comprise the sugars raffinose,

stachyose, verbascose, and ajugose. They are simple

sugars comprising a sucrose molecule to which are

attached a-d-galactopyranosyl units in a-1,6-galacto-

sidic linkages. They are a common carbohydrate

present in the seed of grain legumes. It is thought

that on seed germination, they provide energy for

the emerging plant embryo.

0010Symptoms When members of the raffinose group of

sugars are consumed by monogastrics, the animals do

not have the necessary gut enzymes to digest these

sugars in the intestinal tract. Consequently, they pass

undigested to the large intestine where they are anae-

robically fermented by gut bacteria. The products of

this fermentation are, among other things, the gases

carbon dioxide, methane, and hydrogen. Thus, con-

sumption of legumes rich in these sugars leads to a

considerable increase in flatus production. Some

legumes can produce up to 137 ml h

1

of flatus, caus-

ing severe abdominal discomfort, bloating, belching,

flatulence, constipation, and diarrhea. In pigs, in par-

ticular, high levels of oligosaccharides in their rations

can cause severe digestive upsets and reduced growth.

0011Minimization of problems There is considerable

interspecific variation in the level of oligosaccharides

in legume seed. Soybean, chickpea (Cicer arietinum),

and Phaseolus spp. tend to contain high levels, whereas

lentil (Lens culinaris) and mung bean (Vigna radiata)

contain lower levels. There is also some evidence of

intraspecific variation among cultivars within species.

0012Traditional methods of processing grain legumes

prior to their consumption significantly reduced the

level of oligosaccharides. In the production of bean

sprouts, the oligosaccharide level falls as germination

continues. Tofu, which is a traditional protein pre-

cipitate produced from soybean, has low levels of

oligosaccharide. In the production of tempe, which

is a traditional Indonesian soy-based food, cooked

beans are fermented with Rhizopus oligosporus.

During fermentation, the oligosaccharides are util-

ized by fungus as an energy source, and the resulting

tempe contains low levels of oligosaccharides.

0013Traditional legume-processing methods cannot be

used for bulk quantities, however, because of the cost

of processing. In the stock food industry, the problem

is approached by the plant breeders trying to reduce

the level of these sugars in the seed using selection

within the species.

Alkaloids

0014A number of plant species contain significant amounts

of alkaloids. Of the alkaloids, the most universally

PLANT ANTINUTRITIONAL FACTORS/Characteristics 4579

known is probably nicotine, which is a component of

tobacco (Nicotiana tabacum) and is ingested on a

daily basis by millions of people. Edible members of

the plant family Solanaceae, such as potato (Solanum

tuberosum), tomato (Lycopersicon esculentum), and

and eggplant (Solanum melongena), may contain high

levels of glycoalkaloids. (See Alkaloids: Toxicology.)

0015 Among legumes that are eaten by humans, or used

in stock rations, plants of the Genus Lupinus contain

high levels of alkaloid in both their foliage and their

seed. In most lupin species, the alkaloids present are

quiniolizidine alkaloids. However, Lupinus luteus,

which is from the Iberian Peninsula, contains the

indol alkaloid gramine.

0016 Compounds responsible The alkaloids present in

food plants of the family Solanaceae are glycoalka-

loids. They have a stereoalkaloid nucleus, which is

attached to a sugar side-chain. Their role is to protect

the plant from insect attack. They are also implicated

in both fungal and nematode resistance. The alka-

loids tend to be concentrated near the epidermis and

in the leaves. In green tomatoes, the fruits are pro-

tected while ripening by the alkaloid tomatine. As the

fruit matures, the tomatine level falls.

0017 In potato, the major alkaloids present are a-

solanine and a-chaconine. They are present through-

out the plant. Apart from a case in Scandinavia,

where plant breeders increased the alkaloid levels in

a new cultivar to the level where they produced toxic

symptoms in humans, potato alkaloids are not a

problem, provided that the tubers have been properly

grown and stored. If potato tubers form too close to

the soil surface, or are exposed to light after harvest,

there is a rapid increase in alkaloid level. Harvested

potatoes should be stored in the dark. In modern

shopping systems, potatoes are often exposed to

light in supermarkets when they are packed in clear

plastic bags.

0018Among lupin species that are grown for their seed,

there are a large number of quinolizidine alkaloids

(Table 1). However, only eight of these occur in

amounts of more than 4% of total alkaloids. The

main alkaloids are sparteine, lupanine, 13-hydroxy-

lupanine, albine, multiflorine, angustifioline, tetrahy-

drorhombifoline, and lupinine. The distribution of

the alkaloids tends to vary with plant species. Most

of the alkaloid in Lupinus albus, L. angustifolius, and

L. mutabilis is lupanine. In L. luteus, the major alkal-

oid present is lupinine. The gramine in L. luteus (an

indol alkaloid) can comprise up to 0.12% of total

seed dry matter.

0019Symptoms Both potato and lupin alkaloids affect

the nervous system. An excess of potato alkaloids

can produce symptoms similar to a bad hangover.

There have been deaths reported from the ingestion

of excess potato alkaloids. Ingestion of lupin alkaloid

leachate by a human has been known to produce

blurred vision, an irregular heart beat rate, and

urine retention. In animal feeding, the response to

foods high in alkaloids is a loss of appetite, because

of their bitter taste. This induces a reduction in feed

intake and reduces growth rate.

0020Minimization of problems Fortunately, the alka-

loids in both potatoes and lupins are water-soluble.

Further, in potatoes, they are concentrated under the

skin. Peeling the potato removes most of the alkaloid

in the tuber. Soaking and boiling in water further

reduce alkaloid levels. In both the altiplano of South

America and southern Europe, L. mutabilis and

L. albus are processed to reduce alkaloid levels. The

seed is soaked and boiled and then soaked in running

water for up to three days, by which time the alkaloid

levels are significantly reduced. As noted above, with

potatoes, correct storage in the dark, after harvest

and prior to use, is also important.

tbl0001 Table 1 Distribution of total alkaloids present in smooth seeded lupin species used in human diets and animal feeding

Alkaloid

Lupin species

L. albus L. angustifolius L. luteus L. mutabilis

Sparteine Trace Trace 30–50% 5–20%

Lupanine 50–80% 50–80% Trace 50–70%

17-Oxylupanineo Trace Trace

4-Hydroxylupanine 7%

13-Hydroxylupanine 5–15% 10–20% 10–20%

Albine 5–15%

Multiflorine 3–10% Trace

Angustifoline Trace 5–20% Trace

Tetrahydrorhombifoline Trace Trace Trace 4%

Lupinine 40–70% Trace

Esteralkaloids 1–5% 1–3% Trace 1–5%

Not detected.

4580 PLANT ANTINUTRITIONAL FACTORS/Characteristics

0021 In lupin, since the early 1920s, an alternative ap-

proach has been to select for low-alkaloid genotypes.

Since then, because of work by plant breeders in

Germany, Australia, and South America there are

now low-alkaloid genotypes of Lupinus albus,

L. angustifolius, L. luteus, and L. mutabilis. In Aus-

tralia, low-alkaloid genotypes of rough-seeded Medi-

terranean lupins have now been bred. Thus, lupin

seed is a safe food, and alkaloids are not likely to be

a problem, provided the seed is processed before

consumption or only low-alkaloid types are used.

Cyanogenic Glycosides

0022 A number of plant species produce hydrogen cyanide

(HCN) from cyanogenic glycosides when they are

consumed. These cyanogens are glycosides of a

sugar, often glucose, which is combined with a

cyanide containing aglycone.

0023 Plant species of major importance in human and

animal feeding are cassava (Manihot esculenta), lin-

seed (Linum usitatissmium), various sorghums (Sor-

ghum spp), white clover (Trifolium repens), and some

species of Lotus. Lesser quantities are found in the

kernels of such plants as almonds (Amygdalus com-

munis), apricots (Prunus armeniaca), peaches (Pru-

nus persica), and apples (Malus sylvestris).

0024 When plant material containing the glycoside is

consumed, it is broken down by a b-glucosidase to

produce a sugar and an aglycone. The aglycone is

then acted upon by a hydroxynitrile lyase to produce

cyanide and an aldehyde or a ketone.

0025 Compounds responsible The compounds respon-

sible vary with plant species. However, the major

cyanogens are amygdalin and prunasin, which are

found in fruit kernels. The latter also occurs in

bracken fern (Pteridium aquilinum), dhurrin, found

in members of the genus Sorghum and linamarin,

found in clovers, linseed, cassava, and lima beans

(Phaseolus lunatus). Cassava root contains relatively

low levels at 53 mg of CN per 100 g of plant tissue.

Sorghum forage contains 250 mg of CN per 100 g of

plant tissue and lima beans up to 300 mg of CN per

100 g of plant tissue.

0026 Symptoms As cyanide is extremely toxic, one of the

most obvious symptoms is death. In the body, cyanide

acts by inhibiting cytochrome oxidase, the final step in

electron transport, and thus blocks ATP synthesis.

Prior to death, symptoms include faster and deeper

respiration, a faster irregular and weaker pulse, saliva-

tion and frothing at the mouth, muscular spasms, dila-

tion of the pupils, and bright red mucous membranes.

0027 In Africa, where many people consume cassava

on a regular basis, many members of the human

population are regularly exposed to low levels of

cyanide in their diet. This is associated with a condi-

tion called tropical ataxic neuropathy. Symptoms in-

clude neurological disturbances, which affect vision,

hearing, and the peripheral nervous system. There are

also raised levels of blood thiocyanate and goiter.

Cassava consumption, combined with protein defi-

ciency, which is often common in societies that con-

sume large amounts of starchy tubers, can lead to

reduced glucose tolerance and diabetes. There is

some evidence that the symptoms can be partially

alleviated by the administration of vitamin B

and

methionine.

0028Minimization of problems As with many other

problems of plant ANFs, one method of reducing

the problem is via plant breeding. Older varieties of

white clover used to produce high levels of cyanide.

Newer cultivars have much lower concentrations.

Similarly, breeding work has been carried out with

lima beans to reduce their potential toxicity.

0029To produce cyanide, plant enzyme systems need to

be active, and so heating plant material, and denatur-

ing the enzymes, will generally render it safe. Thus, in

the production of linseed meal, which is the residue

left over after oil extraction, the material is generally

heated sufficiently, while passing through an oil press,

to render the enzyme system inactive. The use of

entire linseed seeds in bakery products usually leads

to their being exposed to high temperatures before

they are eaten. In home consumption of cassava,

cooking is used to inactivate the enzymes. Roots are

also washed, grated, and soaked in water, and further

washed to eliminate the cyanide. As with clover and

lima beans, plant breeders are also trying to reduce

the level of the cyanogen in cassava roots.

Glucosinolates

0030Glucosinolates are a common component in plants of

the family Brassicacea. They have become of more

interest in recent years following the considerable

increase in the production of rape oil (Canola) from

the seed of spring and winter forms of Brassica cam-

pestris and B. napus. Following oil extraction in

these, and other Brassica spp., a high-protein meal is

left, which contains high levels of sulfur amino acids.

However, the presence of glucosinolates in the

resulting meal has limited the use of the meal in

animal feeding because of its tendency to produce

goiter and other symptoms associated with low

iodine availability. (See Glucosinolates.)

0031Compounds responsible Glucosinolates are glyco-

sides of b-d-thioglucose. They contain an aglycone,

which, on hydrolysis, can yield an isothiocyanate, a

PLANT ANTINUTRITIONAL FACTORS/Characteristics 4581

nitrile, or a thiocyanate. Glucosinolates are respon-

sible for the sharp flavor of such plants as horseradish

(Armoracia rusticana) various mustards (Brassica

spp), watercress (Nasturtium officinale), and radish

(Raphanus sativus).

0032 In plant tissues, the glucosinolates are present at

the same time as the enzyme myrosinase, which is a

thioglucosidase. In intact plants, the enzyme and the

substrate occur in different parts of the plant. How-

ever, when plant tissues are disrupted, as may occur in

chewing, or in pressing and grinding for oil extrac-

tion, the two components come together. As a result,

the myrosinase breaks the thioglucoside bond on the

glucosinolate. The result is the production of glucose

and an aglucone intermediate product. The latter

breaks down to produce a number of possible toxic

components. The most common are isothiocyanates

and nitriles. However, this depends on the conditions

at the time of breakdown, and other products, such as

goitrin, may be produced.

0033 Symptoms The major effect of the breakdown prod-

ucts of the glucosinolates is interference with thyroid

function. Goiter can occur in both humans and

animals, but it mainly appears in animals when they

are fed on rations in which rapeseed meal provides a

considerable amount of the protein in the ration.

Besides obvious morphological effects on the thyroid

gland of animals, differences can be shown in bio-

chemical parameters such as decreased serum

thyroxin levels. In pigs, when sows are fed on high-

glucosinolate rations, it can lead to abortion of piglets

and increased death of piglets after birth.

0034 Minimization of problems As with many other

ANFs, moist heating the meal prior to feeding it to

the animals or heat extrusion can reduce problems

associated with the feeding of glucosinolates in Bras-

sica meals. Bacterial fermentation and enzymes have

also been used. However, the most significant recent

achievement in reducing the problem was wrought by

Canadian plant breeders who produced new cultivars

of both major oils seed rape species, which contain

considerably reduced levels of glucosinolates. These

were originally known as ‘00’ rapes but have since

been renamed Canola. This major plant breeding

advance has meant that considerably greater amounts

of Brassica meal can now be incorporated into mono-

gastric rations without any deleterious effects on

thyroid function and iodine metabolism.

Lectins

0035 Lectins, or phytohemagglutinins, are present in the

seed of a number of legume species that are consumed

by humans. The most important legume species,

which is high in lectin, is Phaseolus vulgaris, because

of its major role in the diet of central and northern

South American populations. Phaseolus vulgaris

lectin is highly toxic, as is the lectin from scarlet

runner bean (Phaseolus coccineus) and tepary bean

(P. acutifolius). At the other extreme, legume species

with low to zero lectin activity include chick pea

(Cicer arietinum), cow peas (Vigna unguiculata),

faba bean (Vicia faba), lentil (Lens culinaris), mung

bean (Vigna radiata), peas (Pisum sativum), pigeon

pea (Cajanas cajan), and soybean (Glycine max). (See

Hemagglutinins (Haemagglutinins).)

0036In the plant, it appears that lectins are involved in

the chemical recognition of the legume root by Rhi-

zobium bacteria. Thus, although plant breeding may

be used to reduce their absolute concentration in seed,

it is unlikely that they could be entirely eliminated

from legume seeds because of their importance in

biological nitrogen fixation.

0037Compounds responsible Lectins are either carbohy-

drate-binding proteins or glycoproteins. They are

capable of recognizing and binding carbohydrates

in complex glycoconjugates. More than 70 lectins

have now been isolated from legumes. They usually

contain two or four subunits, each with a single

carbohydrate-binding site.

0038Symptoms The main effect of lectins, when they are

included in the diet, is through their interference with

digestion in the small intestine. Lectins are resistant to

breakdown in the digestive tract and bind to surface

receptors. These bound lectins then cause changes in

the metabolism of the epithelial cells. These changes

include cell hypertrophy and hyperplasia. Indeed,

animals fed high levels of toxic lectin can suffer

rapid body weight loss, while the weight of the small

intestine is significantly increased. Other changes that

may occur are changed gut endocrine systems and

hormone production, changed gut immune systems

and disturbances in gut bacterial ecology, which,

combined, can cause a greater sensitivity to bacterial

infection. At the gross level, these effects are mediated

via reduced growth, diarrhea, reduced nutrient

absorption, and increased incidence of bacterial

infections. In highly toxic species such as the red

kidney bean (Phaseolus vulgaris), these symptoms,

when combined, cause death.

0039Minimization of problems As indicated above, it is

unlikely that it will be possible to breed the lectins out

of legume seed entirely because of their role in the

establishment of biological nitrogen fixation. How-

ever, it may be possible to select for reduced levels

and/or to select for less toxic lectins. Fortunately,

4582 PLANT ANTINUTRITIONAL FACTORS/Characteristics

most lectins are heat-labile. Dry Phaseolus beans re-

quire long soaking and cooking times before they are

soft enough to eat, and therefore, for human con-

sumption, most seed is rendered safe before it is

consumed. However, there are reports that if beans

are heated at 80



C, lectin levels may be increased,

and thus the beans are more, not less, toxic.

0040 For animal feeding, however, lectin-containing seed

needs to be processed to reduce lectin levels before

the seed can be fed to monogastric animals. Gener-

ally, seed can be rendered safe by heat treatment prior

to consumption. Other techniques that have been

employed include chemical treatment, production of

protein isolates, germination, and moist extrusion.

Saponins

0041 Saponins are a diverse group of chemicals, which

derive their name from their ability to form soap-

like foams in aqueous solutions. They occur in a

considerable number of plant species ranging from

asparagus (Asparagus officinalis) to cucumber (Cucu-

mis sativus). They are also present in a number of

commonly used herbs and spices such as fenugreek

(Trigonella foenumgraecum), ginseng (Panax spp.),

liquorice (Glycyrrhiza glabra), and nutmeg (Myris-

tica fragrans). (See Saponins.)

0042 Saponins fall in a gray area between being ANFs or

beneficial plant constituents. When monogastric

animals such as pigs and poultry are fed rations con-

taining such products as alfalfa (Medicago sativa)

meal, there is a reduction in growth. However, experi-

ments with a number of animal species have failed to

show any significant effect of saponins on a number

of growth parameters. As saponins are very bitter, one

hypothesis is that their effects are mediated through

reduced food intake.

0043 On the positive side, it has been shown that sap-

onins can form complexes with cholesterol in the gas-

trointestinal tract. This leads to increased excretion of

cholesterol and a reduction in blood cholesterol level.

With the high level of coronary artery disease in most

developed countries, this is seen to have potential

medical benefits. The most common form of ingestion

by humans is through alfalfa sprouts. Recent publicity

would suggest that the sprouts are more dangerous

because of bacterial contamination, leading to gastro-

enteritis, than because of their saponin content.

0044 Compounds responsible All saponins contain an

aglycone, which is either sapogenol or sapogenein.

The aglycone is linked to one or more sugars or

oligosaccharides. However, the saponins fall into

two groups, depending on whether the aglycone is

triterpenoid or steroidal. Most cultivated plants

have a triterpenoid aglycone, whereas in many herbs,

it is steroidal. Saponin’s structure is complex and

depends on the variation in the aglycone structure

and the position and nature of attachment of the

glycosides to the molecule. Aglycones can be linked

to d-glactose, l-arabinose, l-rhamnose, d-glucose,

d-xylose, d-mannose, and d-glucuronic acid. The

chain lengths are generally linear and comprise two

to five saccharide units. This diversity in structure

leads to a diversity of biological activity.

0045Symptoms The major physiological effect of sap-

onins is on cell membrane permeability. It has been

proposed that the saponins combine with membrane

cholesterol to form permeable micelles in the plane of

the membrane. However, as indicated above, the

major effect of saponins in reducing intake appears to

be the result of their bitter flavor-reducing feed intake,

as experiments on a range of animal species have not

shown any pathogenic effects of saponin intake.

0046Minimization of problems Saponins that are pre-

sent in herbs and spices are likely to be present in

such small quantities in the diet that they are unlikely

to have any deleterious effect. Alfalfa has been

selected by plant breeders to contain low levels of

saponins. Similarly, quinoa (Chenopodium quinoa)

seed, which is a minor Andean food crop, has reported

saponin levels ranging from 0.14 to 2.3%. This has

allowed for the selection of low saponin genotypes. In

the Andes, in households, saponins are removed by

soaking, washing, and rubbing to reduce the saponin

levels in quinoa grain. Industrially, the seed is milled,

or washed and milled.

Tannins

0047Many plant species contain tannins. However, the

seed of a number of legume species and some sor-

ghum lines contain appreciable quantities of tannins.

These have dietary impacts on animals that consume

them. Tannin is a generic name for polyphenolic com-

pounds derived from plants. They have molecular

weights of between 500 and 3000 and are divided

into two classes, hydrolyzable and condensed. The

former can be broken down by acid, alkali, and some

hydrolytic enzymes. The latter are resistant to being

broken down.

0048Faba bean (Vicia faba) tannins are involved with

the human disease favism. The inclusion of high levels

of tannin in rations for a range of monogastric

animals reduces weight gain and feed-conversion effi-

ciency. When fed to hens, tannins reduce egg produc-

tion. However, the consumption of forage with high

tannin levels can be advantageous in ruminant animal

production. Tannins prevent the formation of the

stabilized foams that produce bloat. Further, tannins

PLANT ANTINUTRITIONAL FACTORS/Characteristics 4583

form complexes with free protein in the rumen and

prevent protein degradation in the rumen. (See

Tannins and Polyphenols.)

0049 Compounds responsible Hydrolyzable tannins have

a polyhdric alcohol at their core, the hydroxyl groups

of which are partially, or fully, esterified with either

gallic or hexahydroxydiphenic acid. They may have

long chains of gallic acid coming from the central

glucose core. On hydrolysis with acid or enzymes,

the hydrolyzable tannins break down into their con-

stituent phenolic acids and carbohydrates.

0050 Condensed tannins are dimers, the simplest of

which is procyanidin, or higher oligomers of substi-

tuted flavan-3-ols. Monomeric tannins are usually

linked by carbon–carbon bonds between carbon-4

and carbon-8 of two flavan-3-ols. The bonds that

are formed are highly stable and require heating

with strong acids to break them down.

0051 Symptoms In humans, favism produces acute hemo-

lytic anemia. After susceptible subjects eat the beans,

symptoms can occur in 5–24 h. The symptoms in-

clude headache, vomiting, nausea, yawning, stomach

pains, and a raised temperature. The symptoms may

subside naturally or, in severe cases, lead to hemolytic

anemia, followed by hemoglobinuria. Previously,

deaths in children could reach 8%. The disease is

due to the lack of an enzyme in red blood cells,

glucose-6-phosphate dehydrogenase. It is thought

that over 100 million people, of mainly eastern Medi-

terranean origin, are susceptible to the disease. There

has been some suggestion that the high levels of

tannins in the diet of people who use sorghum as

their main staple may be associated with an increased

incidence of esophageal cancer.

0052 The condensed tannins provide an important plant

defense against herbivory. In particular, bird damage

can be reduced by high tannin levels in crops such as

sorghum and insect damage in seed of species like

faba beans. The adverse nutritional effects of tannins

are due to their reaction with proteins to form indi-

gestible complexes. They can also form complexes

with digestive enzymes and reduce the overall digest-

ibility of food. They can irritate the gut lining and

stimulate the secretion of mucus. This increases

endogenous protein secretion and therefore increases

protein demand. They also form complexes with

divalent metals and reduce mineral absorption. A

common feature of diets high in tannin is weight loss.

0053 Minimization of problems In most legume species,

there is a strong relationship between the level of

condensed tannin in the seed and their flower color.

Plants that have white flowers have low tannin levels

in their seed. Thus, in a number of the legume species

that have high tannin levels, the development of

white-flowered genotypes gives pale-colored seed

with low tannin levels.

0054In both legume seed and sorghum seed, the tannins

are located mainly in the seed coat. Thus, dehulling

the seed and discarding the hulls reduce the tannin

level. Heat treatments do not destroy tannins in sor-

ghum. However, sorghum tannins are unstable under

alkaline conditions. Soaking in an alkaline solution

followed by washing reduces the level of condensed

tannins. The tannins in sorghum can also be neutral-

ized by treatment with anhydrous ammonia. In

contrast, in faba beans, the principal thermolabile

antinutritional factor is the condensed tannins.

Toxic Amino Acids

0055In the legume family, there are two toxic amino acids

that have a major negative effect on animals or

humans that consume them. The tropical tree species

Leucaena leucocephala contains the amino acid

mimosine, which is an amitotic agent. Seed of the

hardy annual legume species Lathyrus sativus con-

tains a neurotoxic amino acid, generally referred to

as ODAP or BOAA. The latter can cause paralysis of

the lower limbs when eaten in excess.

0056Compounds responsible The full chemical name of

mimosine is b-[1-(3-hydroxy-4-pyridone)]-a-amino

propionic acid. The amino acid ODAP is b-N-

oxalyl-l-a-b-diamino-propionic acid.

0057Symptoms Mimosine is an amitotic agent, and one

of its major effects is to stop hair growth. It has been

tested for a possible role in the chemical shearing of

sheep. Leucaena seed, which is high in mimosine, is

usually only used to a limited extent in human diets

as a curry sambal in Indonesia.

0058The effects of Lathyrus sativus seed consumption

are somewhat more problematic. Consumption of

large amounts of Lathyrus seed in the diet often

occurs in countries such as India and Bangladesh at

times of food shortages as a result of drought. The

condition produced is neurolathyrism, which is par-

alysis of the lower limbs caused by damage to nerve

cells in the spinal cord. There is some evidence that

the response to Lathyrus consumption may be sex-

linked, as it seems to have a major effect on young

males.

0059Minimization of problems With regard to mimo-

sine, there have been some attempts to breed geno-

types of Leucaena leucocephala that are low in

mimosine. As it is such a minor component in human

diets, it is unlikes to be a major problem. During

4584 PLANT ANTINUTRITIONAL FACTORS/Characteristics