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

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ical Analysis, vol. 20, pp. 87–101. New York: Wiley.

Potter BVL (1990) Recent advances in the chemistry

and biochemistry of inositol phosphates of biological

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(1989) Phytates in Cereals and Legumes. Boca Raton:

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mination of isomers of inositol mono- to hexapho-

sphates in selected foods and intestinal contents using

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Inositol hexaphosphate hydrolysis by Baker’s yeast.

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of Agricultural and Food Chemistry 48: 100–104.

Xu P, Price J and Aggett PJ (1992) Recent advances in

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16: 245–262.

Nutritional Impact

U Konietzny, Karlsruhe, Dettenheim-Liedolsheim,

Germany

R Greiner, Centre for Molecular Biology, Federal

Research Centre for Nutrition, Karlsruhe, Germany

Introduction

0001 Mixed salts of phytic acid [myo-inositol(1,2,3,4,5,6)-

hexakisphosphoric acid) are common constituents of

foods and feed, since phytate is a naturally occurring

compound formed during the maturation of seeds and

cereal grains. Depending on the amount of plant foods

in the diet and the grade of food processing, the daily

intake of phytate can be as high as 4500 mg. On

average, the daily intake of phytate was estimated to

be 2000–2600 mg for vegetarian diets as well as diets

of inhabitants of rural areas of developing countries

and 300–1300 mg for mixed diets (Table 1).

0002 Phytate behaves in a broad pH region as a highly

negatively charged ion and therefore has a tremen-

dous affinity for food components with positive

charge(s) (See Phytic Acid: Properties and Determin-

ation). There is a large body of evidence that minerals

are less available from foods of plant origin as com-

pared to animal-based foods. Minerals of concern in

this regard include zinc, iron, calcium, magnesium,

manganese, and copper. The formation of insoluble

cation–phytate complexes at physiological pH values

is regarded as the major reason for the poor mineral

bioavailability, since these complexes are essentially

nonabsorbable from the gastrointestinal tract. Fur-

thermore, phytate phosphorus may not be nutrition-

ally available, since phytate is not hydrolyzable

quantitatively in the human gut. Consumption of

phytate, however, seems not to have only negative

aspects on human health. In the last few years, results

of epidemiological and animal studies also suggest

beneficial effects, such as decreasing the risk of heart

disease and colon cancer, but data from human

studies are still lacking.

tbl0001Table 1 Phytate content of foods of plant origin

Food Phytate

(mgg

1

drymatter)

Cereal-based

French bread 0.3–0.4

Mixed-flour bread (70% wheat, 30% rye) 0.2–0.7

Mixed-flour bread (70% rye, 30% wheat) 0–0.3

Sourdough rye bread 0–0.3

Wholewheat bread 4.3–6.8

Whole rye bread 2.5–4.8

Unleavened wheat bread 9.2–19.5

Corn bread 5.2–7.1

Unleavened corn bread 11.4–16.3

Oat bran 12.4–29.6

Oat flakes 8.2–10.3

Oat porridge 7.7–10.6

Pasta 2.2–8.6

Maize 11.5–14.2

Cornflakes 0.8–1.3

Rice (polished, cooked) 1.4–2.9

Wild rice (cooked) 16.4–20.1

Sorghum 5.6–9.8

Legume-based

Chickpea (cooked) 4.9–6.1

Cowpea (cooked) 5.8–10.3

Black beans (cooked) 8.5–11.3

White beans (cooked) 9.1–10.9

Lima beans (cooked) 6.2–9.8

Faba beans (cooked) 10.1–13.7

Kidney beans (cooked) 8.9–11.2

Navy beans (cooked) 7.4–10.6

Soybeans 9.9–14.9

Tempeh 9.1–10.3

Tofu 8.2–9.3

Lentils (cooked) 6.5–9.3

Green peas (cooked) 5.7–7.8

Peanuts 16.5–19.1

Others

Sesame seeds (toasted) 43.2–55.1

Soy protein isolate 4.3–11.7

Soy protein concentrate 12.4–21.7

Buckwheat 10.3–14.1

Amaranth grain 12.6–14.3

PHYTIC ACID/Nutritional Impact 4555

Phytate as an Antinutrient

0003 The main concern about the presence of phytate in

the diet is its negative effect on mineral uptake. Most

studies have shown an inverse relationship between

phytate content and mineral availability, although

there are great differences in the behavior of indivi-

dual minerals (Table 2).

Difficulties in Experimental Approaches

0004 The effect of phytate on mineral absorption is highly

controversial, since many investigations have shown

a negative effect, but some studies have also shown no

effect or even enhancement of mineral uptake. This

controversial result gives an idea of the complexity of

mineral absorption in the intestine (Figure 1). The

differing types of experimental design may explain

much of this controversy. In vitro studies can only

incompletely simulate the physiological factors and

physicochemical conditions affecting mineral avai-

lability. Also, in vivo approaches, widely used in

mineral bioavailability studies, are not easily compar-

able due to the existence of many factors that cannot

be reproduced in the different experiments. In add-

ition, part of the variability may arise from differ-

ences in the method of phytate analysis and

experimental techniques for measuring mineral bio-

availability. (See Minerals – Dietary Importance.)

0005 The solubility of phytate complexes is a critical and

perhaps overriding issue, because complexes that are

insoluble in the upper small intestine, where max-

imum mineral absorption normally occurs, are highly

unlikely to provide absorbable essential elements.

Thus, chemical interactions of phytate in the upper

gastrointestinal tract are of particular concern. The

form in which many minerals occur in foodstuffs is

largely unknown, as is also the form in which they

occur in the gut. Thus, predicting the specific inter-

actions of phytate in the gastrointestinal tract and

the nutritional implications of these interactions is

very difficult. As foods are ingested and the digesta

travels through the gastrointestinal tract, phytate may

continue to maintain associations developed during

ripening or food processing or phytate complexes

may dissociate and other chelates form, since binding

of phytate with minerals or proteins depends upon

the pH value, which changes from low pH in the

stomach to about neutral in the upper intestine.

0006 The total composition of experimental diets has a

great importance on mineral bioavailability, since the

reduced availability of essential minerals depends on

several dietary factors, such as the total concentration

and composition of minerals or the phytate concen-

tration. Phytate per se seems not to have a direct

adverse affect on mineral absorption, since the

physiological concentration of a single mineral is

generally not sufficient for the formation of insoluble

phytate complexes in the small intestine. Since cal-

cium concentration in the diet is high enough for

complete precipitation of phytate, leading to a copre-

cipitation of other minerals, the calcium content of

the diets is of vital importance to the negative impact

of phytate on mineral bioavailability. Calcium clearly

augments the adverse effects of phytate on mineral

absorption, and numerous other dietary components

have lesser effects, both beneficial and adverse. For

example, the intake of organic acids such as ascorbic

acid and/or meat effectively counteracted the inhibi-

tory effect of phytate, whereas dietary fiber and poly-

phenols intensified it. Both phytate and fiber have a

high potential binding capacity for minerals and, be-

cause they are generally presented together in many

foods, it is very difficult to separate completely the

effects of these two in studies with typical human

diets.

0007Phytate degradation during digestion in the gastro-

intestinal tract may have a positive effect on mineral

absorption, since results of animal and human studies

indicated that besides phytate, only the first degra-

dation product of phytate, myo-inositol pentakis-

phosphate, showed negative effects on zinc, iron,

and calcium absorption in its isolated form, while

myo-inositol tetrakis- and trisphosphates had no

effect in the concentrations under investigation. Fur-

thermore, phytate phosphorus becomes available for

utilization after release from the myo-inositol ring.

The hydrolysis of phytate in the gastrointestinal

tract of monogastric animals, including humans,

may be carried out by the action of phytate-degrading

enzymes from three sources: dietary phytases, phy-

tases from the bacterial flora in the gut, and intestinal

mucosal phytases. The level of dietary calcium is

thereby of particular interest. A low calcium concen-

tration may favor increased phytate hydrolysis in the

gut, whereas elevated dietary calcium decreases its

hydrolysis. It was recently reported that mucosal phy-

tase, if present in the human small intestine, does not

seem to play a significant role in phytate digestion,

whereas the dietary phytases are an important factor,

since these enzymes are active in the stomach for a

certain time. Phytate degradation by phytases from

the bacterial flora in the colon does not contribute to

mineral and phytate phosphorus absorption, since,

with the exception of calcium, absorption is negli-

gible there.

0008Furthermore, the history of food processing

appears to be of great interest insofar as it can affect

the availability of phytate phosphorus and phytate-

associated cations. Depending on the manufacturing

process, reduction in phytate content of the foods,

4556 PHYTIC ACID/Nutritional Impact

tbl0002 Table 2 Effect of phytate on mineral and phosphorus availability

Zinc Iron Calcium Copper, manganese, magne-

sium

Phosphorus

Zinc was reported to be the essential mineral

most adversely affected by phytate. Zinc

deficiency in humans was first reported in

1963 in Egyptian boys whose diet consisted in

the main of bread and beans. These patients,

who were characterized by dwarfism and

hypogonadism, showed a response to zinc

supplementation of their diet. It became

accepted that the presence of phytate in plant

products was an important factor in the

reduction of zinc absorption from foodstuff.

Zinc absorption was shown to be inversely

correlated with phytate content of the meal.

There is, however, some lack of agreement

among studies, particularly with respect to

specific foods and their components. In

addition, it was shown that phytate not only

depresses the bioavailability of dietary zinc,

but also substantially reduces the

reabsorption of endogenous intestinal zinc

A great deal of controversy exists

regarding the effect of phytate on the

availability of dietary iron. Much of this

controversy may be due to the low

absorption of iron in general, the

presence of different iron phytates with

different solubility, and the existence

of two types of food iron, heme and

nonheme iron. Heme iron is better

absorbed and is little influenced by

dietary factors; nonheme iron is less

easily absorbed, and its absorption is

affected by other dietary factors. Since

many human studies indicated that

phytate had a very strong inhibitory

effect on iron absorption, it is well

accepted today that phytate appeared

to be the major contributor to the

reduction in iron availability in

humans, but some other factor(s) also

contribute

Human studies indicated that

phytate inhibited calcium

absorption, but the effect

of phytate on calcium

availability seems not to

be as extreme as on that of

iron and particularly zinc.

This may be due to the

relatively high calcium

content of plant-based

foods, the ability of phytate

degradation by microbial

phytases of the gut flora,

and the absorption of

calcium in the large

intestine

Relatively few studies have

dealt with the effects of

phytate on dietary copper,

manganese, and

magnesium utilization.

Phytate has been shown to

decrease their

bioavailability in in vivo

studies. It appears that the

effect of phytate on copper,

manganese, and

magnesium bioavailability

is less marked than those

for some other essential

elements

The fact that phytate

phosphorus is poorly

available to monogastric

animals, including humans,

was demonstrated several

years ago. Phosphorus is

absorbed as the

orthophosphate. No

conclusive evidence for

absorption of phytate or

other myo-inositol

phosphates is available at

present. Thus, the utilization

of phytate phosphorus by

monogastric animals will

largely depend on their

ability to hydrolyze phytate

destruction or alteration of food compounds

promoting or depressing mineral availability, and

inactivation of phytate-degrading enzymes may

occur. Inactivating the endogenous dietary phytase

leads to a limited degradation of phytate in the stom-

ach and therefore to a lower bioavailability of min-

erals and phytate phosphorus. During food processing

and food digestion, phytate can be partially

dephosphorylated to yield a large number of pos-

itional isomers of myo-inositol pentakis-, tetrakis-,

tris-, bis-, and monophosphates (See Phytic Acid:

Properties and Determination). Especially with re-

spect to the isomers, their chelating potential has

not been carefully studied. This is of great import-

ance, since processed foods and digesta may contain

lower myo-inositol phosphates in great amounts and

human studies have shown that myo-inositol tetrakis-

and tris-phosphates contribute in high concentrations

to the negative effect on mineral absorption. On the

other hand, recent evidence has suggested that, be-

sides the adverse effects of phytate and other highly

phosphorylated myo-inositol phosphates on mineral

absorption, lower phosphorylated myo-inositol phos-

phates may improve mineral absorption. Therefore, a

reliable and accurate determination of the individual

myo-inositol phosphates in diets must be utilized

before any useful evaluation can be made of their

physiological effect on mineral availability (See Phy-

tic Acid: Properties and Determination).

0009The source of phytate and minerals also influences

the results of experimental studies. Endogenous

phytate and added phytate are not necessarily equal.

Usually sodium phytate is added to experimental

diets; this is capable of chelating the multivalent

cations therein, whereas endogenous phytate is al-

ready bound to those cations in the seeds and grains.

Furthermore, the availability of minerals has mostly

been examined after addition of ionic salts to the

experimental diets. Results obtained under such con-

ditions may not represent the level of absorption of

minerals present in natural sources.

0010The effect of phytate on mineral absorption also

seems to be dependent on the experimental species

used. Phytate degradation in the stomach and small

intestine varies with the species. For example, it was

suggested that rats may not be a good model for

assessing mineral absorption from phytate-containing

foods due to the existence of rat intestinal phytase

activity. In addition, the age of the individuals is of

importance, since it seems that phytate digestion de-

creases with age. The ability of endogenous carriers in

the intestinal mucosa to absorb essential minerals

Food processing (↑, ↓)

Total gastrointestinal phytase activity (↑)

Dietary phytases (↑)

Mucosal phytases (↑, but no significant role in humans)

Dietary calcium content (↓)

Mineral content and composition (↑, ↓)

Calcium content (↓)

Phytate content (↓)

Fiber content (↓)

Content of organic acids, proteins,

amino acids, meat, etc. (↑)

Composition of the diets (↑, ↓)

Species

Age

Mineral status or need

Adaptation to high phytate intakes

Gastrointestinal phytate degradation (↑)

Individual

Intestinal mineral absorption

Phytate degradation (↑)

Destruction or alteration of food compounds

promoting or depressing mineral availability (↑, ↓)

Inactivation of the phytases in the food (↓)

fig0001 Figure 1 Factors interacting with intestinal mineral absorption. " promoting mineral uptake; # depressing mineral uptake.

4558 PHYTIC ACID/Nutritional Impact

bound to phytate or other dietary substances as well

as the mineral status and need of the individual also

have to be considered. A possible adaptation to a

high-phytate intake is controversially discussed. A

long-term study did not show any human adaptation

to a high phytate diet with respect to iron absorption,

whereas the normal bone and teeth calcification

throughout the world in several populations who

depend almost exclusively on cereal diets suggests

human adaptability towards high phytate consump-

tion with respect to calcium absorption.

Protein

0011 Phytate also interacts with proteins, which may affect

protein digestibility negatively. Strong evidence exists

that phytate–protein interactions negatively affect

protein digestibility in vitro. The extent of this effect

depends on the protein source. The inhibition of

digestive enzymes such as alpha-amylase, lipase, or

proteinase by phytate may also be of significance, as

shown in in vitro studies. This may be due to the

nonspecific nature of phytate–protein interactions,

the chelation of calcium ions which are essential for

the activity of trypsin and alpha-amylase, or the inter-

action with the substrates of these enzymes. The

inhibition of proteases may be partly responsible for

the reduced protein digestibility. In vivo, phytate has

also been considered to inhibit alpha-amylase, as

indicated by a negative relationship between phytate

intake and blood glucose response. A negative effect

of phytate on the nutritive value of protein, however,

was not clearly confirmed in vivo. While some have

suggested that phytate does not affect protein digest-

ibility, others have found improvement in protein

utilization with decreasing levels of phytate. This

difference may be at least partly due to the use of

different protein sources. Thus, the significance of

protein–phytate complexes in nutrition is still under

scrutiny. (See Protein: Digestion and Absorption of

Protein and Nitrogen Balance.)

Beneficial Effects of Phytate

0012 In view of the above results, the evidence seems over-

whelming that high intakes of phytate can have

adverse effects on mineral uptake in humans. In the

last few years, however, some novel metabolic effects

of phytate or some of its degradation products

have been recognized. Results of epidemiological

and animal studies suggest possible protective effects

of certain myo-inositol phosphates on heart disease,

renal stone formation, and colon cancer in humans.

Moreover, the potential beneficial effects of phytate

in the prevention of severe poisoning should also be

considered. Calcium phytate 1–2% in the diet has

been found to protect against dietary lead in experi-

mental animals and in human volunteers. Further-

more, calcium phytate was capable of lowering

blood lead levels. Thus, phytate seems to be a helpful

means of counteracting acute oral lead toxicity. The

effect of calcium phytate on acute cadmium toxicity is

still controversially discussed.

Phytate and Diabetes Mellitus

0013Diabetes mellitus is one of the commonest nutrition-

dependent diseases in western society. It may be

caused by hypercaloric diets with a high percentage

of quickly available carbohydrates. Foods that result

in low blood glucose response have been shown to

have great nutritional significance in the prevention

and management of diabetes mellitus. In this regard

phytate-rich foods are of interest, since a negative

relationship between phytate intake and blood

glucose response was reported. For example, phytate-

enriched unleavened bread based on white flour re-

duced in vitro starch digestibility as well as flattening

the glycemic response in five healthy volunteers com-

pared to bread without the addition of phytate. The

in vitro reduction of starch digestion was positively

correlated with the myo-inositol phosphate concen-

tration and negatively with the number of phosphate

groups on the myo-inositol ring. It has to be noted

that there are also studies which have not found an

inhibition of alpha-amylase and starch digestion by

phytate. (See Diabetes Mellitus: Etiology.)

Phytate and Coronary Heart Disease

0014Heart disease is a leading cause of death in western

countries, yet it is low in Japan and developing

countries. Elevated plasma cholesterol or, more

specifically, elevated low-density lipoprotein (LDL)-

cholesterol concentrations have been shown to be one

of the risk factors. It has been proposed that dietary

fiber or, more specifically, phytate as a component of

fiber may influence the etiology of heart disease.

Animal studies have demonstrated that dietary phy-

tate supplementation resulted in significantly lowered

serum cholesterol and triglyceride levels. This effect

was accompanied by a decrease in serum zinc level

and in the ratio of zinc to copper. Thus, the hypothesis

was put forward that coronary heart disease is pre-

dominantly a disease of imbalance in regard to zinc

and copper metabolism. The hypothesis is also based

on the production of hypercholesterolemia, which is a

major factor in the etiology of coronary heart disease,

in rats fed a diet with a high ratio of zinc and copper.

It was thought that excess zinc in the diet resulted in

decreased copper uptake from the small intestine,

PHYTIC ACID/Nutritional Impact 4559

since both minerals compete for common mucosal car-

rier systems. As phytate preferentially binds zinc rather

than copper it is presumed that phytate exerts its effect

probably by decreasing zinc without affecting copper

absorption. It should be pointed out that the support

for the preventive role of phytate in heart disease is only

based on a fewanimal andin vitro studies. Results from

human studies are still lacking. (See Coronary Heart

Disease: Etiology and Risk Factor.)

Phytate and Renal Calculi

0015 The increase of renal stone incidence in northern

Europe, North America, and Japan has been reported

to be coincident with the industrial development of

these countries, making dietary intake suspect. Epi-

demiological investigations found that there were

substantial differences in renal stone incidences

between white and black residents of South Africa.

Whereas renal stone occurred in the white population

with no less frequency than in other Western commu-

nities, it was seldom seen in the black South Africans.

The major dietary difference is that, compared to the

white population, blacks consumed large amounts of

foods containing high levels of fiber and phytate.

Furthermore, a high-phytate diet has been used effect-

ively to treat hypercalciuria and renal stones in

humans. Thus, there is evidence to support the role

of phytate in the prevention of renal stone formation.

0016 Experimental evidence indicates that myo-inositol

bis- and trisphosphates are effective in preventing the

formation of hydroxyapatite crystals in vivo, which

can function as nuclei for stone formation. Thus, the

hypothesis was put forward that a high dietary phy-

tate intake results in an increased urinary content

of lower myo-inosital phosphates, which may act as

very effective inhibitors of stone formation. (See

Renal Function and Disorders: Kidney: Structure

and Function.)

Phytate and Caries

0017 The higher incidence of caries in industrialized com-

pared to developing countries was suggested to be

nutrition-dependent. Phytate lowers the solubility of

calcium, fluoride, and phosphate, the major compon-

ents of enamel. Thus, teeth are more protected against

the leading cause of caries, the attack of acids and

bacteria. Furthermore, the very high affinity of phy-

tate for hydroxyapatite may prevent the formation of

plaque and tartar. (See Dental Disease: Etiology of

Dental Caries.)

Phytate and Cancer

0018 The frequency of colonic cancer varies widely among

human populations. It is a major cause of morbidity

and mortality in western society. The incidence of

cancer, especially large intestinal cancer, has been

associated principally with dietary fat intake and is

inversely related to the intake of dietary fiber. It was

further suggested that the apparent relationship be-

tween fiber intake and rate of colonic cancer might

arise from the fact that many fiber-rich foods contain

large amounts of phytate and that this latter might

be the critical protective element, since an inverse

correlation between colon cancer and the intake of

phytate-rich fiber foods, but not phytate-poor fiber

foods, has been shown. A high phytate intake may

also be an important factor in reducing the breast and

prostatatic cancer mortality in humans. (See Cancer:

Epidemiology.)

0019Both in vivo and in vitro experiments have shown

striking anticancer potential for phytate. It was dem-

onstrated that a treatment regimen of 1–2% sodium

phytate in the drinking water of growing rats signi-

ficantly decreased the number of colon tumors and

tumor volume when treatment was commenced prior

to carcinogenic induction or when administered up to

8 months postinitiation. The inhibitory effect of

phytate was dose-dependent and a mixture of 1%

myo-inositol and 1% phytate was more effective in

suppressing cell proliferation. Unfortunately, these

investigations failed to study and/or report the min-

eral status of the animals.

0020A recent study demonstrated that phytate also

has antineoplastic effects on another tumor model,

the murine fibrosarcoma. Further rat studies indi-

cated that phytate may also reduce the risk of breast

cancer.

0021Not only pure phytate dissolved in the drinking

water, but also phytate in experimental diets such as

wheat bran has a protective effect against colon

cancer, as shown in animal studies. It was concluded

that, while having a role, endogenous phytate is not

the sole active component in wheat bran. This result

clearly emphasizes the fact that dietary components

should not be studied individually for their antineo-

plastic effect. Though phytate at the 2% level signifi-

cantly reduced the weight gain of the animals, it does

not seem to be of major consequence.

0022How phytate exerts its antineoplastic and antipro-

liferative action is not understood. It was proposed

that the mechanism by which dietary phytate reduced

colon cancer was via chelation of iron and suppres-

sion of iron-related initiation and promotion of car-

cinogenesis, since in vitro experiments demonstrated

that phytate is a powerful inhibitor of the Haber–

Weiss reaction, in which iron catalyzes hydroxyl

radical formation (Figure 2). These radicals are medi-

ators of several tissue damages related to tumor initi-

ation and promotion. Phytate not only suppresses

4560 PHYTIC ACID/Nutritional Impact

iron-catalyzed hydroxyl radical generation, but also

acts to inhibit almost totally iron-catalyzed lipid per-

oxidation. Myo-inositol tris-, tetrakis-, and pentakis-

phosphate are also shown to be effective. The effects

of phytate on cancers distant from the intestine, such

as breast cancer, might be simply explained by limita-

tion of iron absorption.

0023 According to a further hypothesis, suppression of

tumor incidence in experimental animals may be

mediated in part by natural killer cells, since phytate

treatment enhanced the activity of natural killer cells

involved in the destruction and growth inhibition of

tumor cells. It was also suggested that phytate acts by

influencing cell regulation. Decreased tumor cell

growth may be due to the complexation of zinc and

magnesium, which play an important role in cell

regulation and gene expression, or due to an influence

of extracellular phytate on the intracellular phospha-

tidylinositol phosphate system, which is important in

regulating a variety of physiological and biochemical

processes, including cell growth via the second

messengers d-Ins(1,4,5)P

and d-Ins(1,3,4,5)P

(See

Phytic Acid: Properties and Determination). Theoret-

ically, dietary phytate could serve as a precursor for

second messengers in situ or as a negative-feedback

inhibitor for their formation. As a prerequisite, phy-

tate or its hydrolysis products have to be taken up by

tumor cells. It was shown that, after exposure of

human-transformed cells to [

H]-phytate, a rapid

uptake of radioactivity occurred, whereas nontrans-

formed cells showed only a limited uptake. The

uptake of radioactivity seems to correspond with

tumor cell growth rate. Furthermore, intragastric-ad-

ministered [

H]-phytate is rapidly absorbed through

the upper gastrointestinal tract and distributed to

various organs in the rat. Analysis demonstrated

that in both studies most of the radioactivity was

due to myo-inositol and myo-inositol monopho-

sphate. The authors suggested that phytate could be

absorbed as such or after a variable degree of depho-

sphorylation, but it cannot be ruled out that phytate

was taken up after complete dephosphorylation to

myo-inositol. From the extracellular area, phytate or

its degradation products may be internalized by endo-

cytosis involving fluid-phase pinocytosis, phagocyt-

osis, or receptor-mediated endocytosis, as well as by

partitioning into and/or through the plasma mem-

brane. The possibility of receptor-mediated endocy-

tosis was supported by identification of a receptor

protein for phytate in rat brain.

Conclusion

0024Numerous reports suggest that a high phytate intake

may suppress absorption of minerals such as zinc,

iron, and calcium and that removal of dietary phytate

significantly improves the bioavailability of those

minerals in humans and animals. Thus, maintaining

a diet exceptionally high in phytate may not be

entirely without risk. However, there is no uniform

agreement on this score, and several studies indicate

that phytate may have minimal or no adverse effects

on mineral bioavailability in humans. Furthermore, it

has been suggested that phytate may exhibit some

beneficial health effects, such as reducing the risk of

heart disease, renal stone formation, and certain types

of cancer.

0025The most severe effects attributable to phytate in

humans have occurred in populations with unrefined

cereals and/or pulses as a major dietary component.

In particular, zinc and iron deficiency, but not cal-

cium, magnesium, manganese, or copper deficiency,

were observed as a consequence of high phytate

intake. Therefore, the anticalcifying and rachitogenic

effect of phytate has been questioned; it appears that

marginal vitamin D status is more important in the

etiology of rickets and osteomalacia. Furthermore,

marked mineral deficiency syndromes attributed to

phytate have not been identified in highly developed

countries. Thus, phytate intake does not necessarily

result in mineral deficiency. The absorption of min-

erals depends on the total composition of the meal

and in a balanced diet containing animal protein, a

high phytate intake does not imply a risk of inad-

equate mineral supply. Therefore, the recommenda-

tion for increasing dietary fiber in western diets

would not be expected to have any adverse effect on

mineral absorption. The higher phytate intake with

whole-grain products will undoubtedly lead to a

percentage decrease in mineral absorption, but the

absolute amount of absorbed minerals may remain

unchanged, because of the large amounts of minerals

in these products. In addition, the impact of phytate

on phosphorus availability can be considered to be of

little consequence in humans, since the phosphorus

intakes are usually high, and phytate phosphorus rep-

resents only a small portion of the total phosphorus in

the diets.

−

+ Fe

Fe-reduction

+ Fe

−

+ OH* + Fe

Fenton reaction

−

+ H

+ OH

−

+ OH*

Haber−Weiss reaction

fig0002 Figure 2 Iron-catalyzed radical formation.

PHYTIC ACID/Nutritional Impact 4561

0026 In population groups where phytate-containing

foods contribute to poor or marginal mineral status,

fortification of some such foods with the correspond-

ing minerals and/or the reduction in phytate content

are possibilities to reduce the risk of mineral deficien-

cies. Since phytate and certain phytate degradation

products have been proposed to exhibit health

benefits in humans, complete degradation or removal

of phytate during food processing should not be

followed up, but a controlled degradation to lower

myo-inositol phosphates. This seems to be a way of

avoiding the adverse effects of phytate on intestinal

mineral absorption and of utilizing their potential

beneficial properties. Controlled degradation is most

easily feasible by using phytases. The addition of

exogenous or activation of endogenous phytases

during food processing has already been shown to

result in extensive phytate degradation without

affecting other food components.

0027 Phytases are also of interest in areas of intensive

animal agriculture. There has been widespread con-

cern in recent years about possible phosphorus pollu-

tion from animal manures. The accumulation of

phosphorus over time from excessive excretion in

manure increases the potential for contaminating

water sources from runoff and erosion. The effect of

increased content of phosphorus in water is eutrophi-

cation, which decreases the available oxygen within

the water, thus posing a hazard to fresh-water animal

life. Effluent control is therefore a high priority in

areas of intensive animal production and, in this con-

text, phytase can become an important waste man-

agement tool, since phytase is active in the stomach

for a certain time and thus increases phytate hydroly-

sis during digestion. Phytase not only has the poten-

tial to reduce environmental pollution by minimizing

the excretion of phosphorus and nitrogen in manure,

but also reduces the need for mineral supplementa-

tion by increasing the availability of cations bound to

phytate.

0028 Because suggestions for the beneficial aspects of

myo-inositol phosphates are only derived from

in vitro, animal, or epidemiological investigations,

carefully controlled human and animal studies should

be carried out to evaluate simultaneously the poten-

tial benefits and adverse effects of dietary myo-inosi-

tol phosphates. If certain phytate degradation

products induce physiological effects (the position of

the phosphate groups on the myo-inositol ring is of

great significance for the physiological function),

phytase may also find application in food processing

to produce foods with improved nutritional value,

health benefits, and maintained sensory properties

(functional foods). By adding the phytase to the

raw material, the antinutritional factor phytate will

be degraded to physiologically active myo-inositol

phosphates during food processing. Thus, foods

with a reduced content of phytate and a regulated

content and composition of lower myo-inositol

phosphate with beneficial health effects could be

designed.

See also: Cancer: Epidemiology; Coronary Heart

Disease: Etiology and Risk Factor; Dental Disease:

Etiology of Dental Caries; Diabetes Mellitus: Etiology;

Minerals – Dietary Importance; Phytic Acid: Properties

and Determination; Protein: Digestion and Absorption of

Protein and Nitrogen Balance; Renal Function and

Disorders: Kidney: Structure and Function

Further Reading

Challa A, Ramkishan R and Reddy BS (1997) Interactive

suppression of aberrant crypt foci induced by azoxy-

methane in rat colon by phytic acid and green tea.

Carcinogenesis 18: 2023–2026.

Erdman JW Jr and Poneros-Schneier A (1989) Phytic acid

interactions with divalent cations in foods and the

gastrointestinal tract. Advances in Experimental Biology

249: 161–171.

Fox MRS and Tao TH (1989) Antinutritive effects of

phytate and other phosphorylated derivatives. Nutri-

tional Toxicology 3: 59–96.

Harland BF and Morris ER (1995) Phytate: a good or a bad

food component? Nutrition Research 5: 733–754.

Jariwalla RJ, Sabin R, Lawson S and Herman ZS (1990)

Lowering of serum cholesterol and triglycerides and

modulation of divalent cations by dietary phytate.

Journal of Applied Nutrition 42: 18–28.

Jenab M and Thompson LU (1998) The influence of phytic

acid in wheat bran on early biomarkers of colon carcino-

genesis. Carcinogenesis 19: 1087–1092.

Ohkawa T, Ebisuno S, Kitagawa M et al. (1984) Rice bran

treatment for patients with hypercalciuric stones: experi-

mental and clinical studies. Journal of Urology 132:

1140–1145.

Porres JM, Stahl CH, Cheng WH et al. (1999) Dietary

intrinsic phytate protects colon from lipid peroxidation

in pigs with a moderately high dietary iron intake. Pro-

ceedings of the Society for Experimental Biology and

Medicine 221: 80–86.

Sandberg AS, Brune M, Carlsson NG, Hallberg L, Skoglund

E and Rossander-Hulthen L (1999) Inositol phosphates

with different numbers of phosphate groups influence

iron absorption in humans. American Journal of Clinical

Nutrition 70: 240–246.

Shamsuddin AM, Vuvenik I and Cole KE (1997) IP-6: a

novel anti-cancer agent. Life Science 61: 343–354.

Shen X, Weaver CM, Kempa-Steczko A, Martin BR, Phil-

lippy BQ and Heany RP (1998) An inositol phosphate as

a calcium absorption enhancer in rats. Nutritional Bio-

chemistry 9: 298–301.

Thompson LU (1988) Antinutrients and blood glucose.

Food Technology 42: 123–132.

4562 PHYTIC ACID/Nutritional Impact

Vucenik I and Shamsuddin AM (1994) [

H]Inositol hexa-

phosphate (phytic acid) is rapidly absorbed and metab-

olized by murine and human malignant cells in vitro.

Journal of Nutrition 124: 861–868.

Zhou JR and Erdman JW Jr (1995) Phytic acid in health and

disease. Critical Reviews in Food Science and Nutrition

35: 495–508.

Phytochemicals See Functional Foods

PICKLING

D M Barrett, University of California Davis, CA, USA

This article is reproduced from Encyclopaedia of Food Science,

Introduction

0001 Pickling is one of the oldest, and most successful,

methods of food preservation known to humans.

This article reviews the origins of pickling, the vari-

ous methods of pickling employed commercially, and

the nature of preservative action. The optimization of

pickle quality depends on maintenance of proper

acidity, salt concentration, temperature, and sanitary

conditions.

History and Tradition

0002 It is difficult to suggest a date for production of the

first pickled foods, but it is known that both vinegar

and spices were being used during biblical times.

Fermentation of plant and animal foods was known

to the early Egyptians, and fish were preserved by

brining in prehistoric times. By the third century bc,

Chinese laborers were recorded to be consuming

acid-fermented mixed vegetables while working on

the Great Wall. In about 2030 bc, northern Indians

brought the seed of the cucumber to the Tigris Valley.

The Koreans created kimchi from acid-fermented

Chinese cabbage, radish, and other ingredients

many centuries ago. Corn, cassava, and sorghum

were fermented and became staples of the African

diet. In the west, acid fermentation of cabbage and

cucumbers produced sauerkraut and pickles, prod-

ucts that are still popular today. Early explorers

carried kegs of sauerkraut and pickles that prevented

scurvy on their voyages.

0003Peterson in 1977 defined pickling, in a broad sense,

as ‘the use of brine, vinegar or a spicy solution to

preserve and give a unique flavour to a food.’ In a

1936 document, the US Department of Agriculture

described cucumber pickles as:

0004immature cucumbers properly prepared, without taking

up any metallic compounds other than salt, and pre-

served in any kind of vinegar, with or without spices.

Pickled onions, pickled beets, pickled beans and other

pickled vegetables are vegetables, prepared as described

above, and conform in name to the vegetables used.

Literature references concerning the technology of

acid fermentation began to appear in the western

press in the early 1900s. In 1919, Orla-Jensen isolated

strains of Betacoccus arabinosaceus from sour pota-

toes, sour cabbage, and sour dough. Pederson, in a

number of classic studies in the 1930s, enumerated

and identified the sequence of microorganisms in-

volved in sauerkraut fermentation. Leuconostoc

mesenteroides was identified as being one of the

most important microorganisms for initiation of

vegetable fermentation. Numerous investigators

have carried out studies on acid-fermented vegetables

over the past century. (See Fermented Foods: Bever-

ages from Sorghum and Millet.)

Advent of New Pickling Methods

0005Brining vegetables in salt, and the resultant lactic acid

fermentation, is an ancient form of preservation. Two

new methods of pickling cucumbers, which represent

the largest volume of a single vegetable preserved by

pickling, have been developed during the 1900s. Both

methods use lower salt concentrations and result in a

milder product. The first new method, pasteurization

and direct acidification, was developed and began

commercial production in the 1940s. The second,

PICKLING 4563

refrigeration and direct addition of acid and preser-

vative, was introduced in the 1960s. Relative quan-

tities of cucumbers preserved by the three pickling

methods in 1984 were: brine fermentation, 43%;

pasteurization, 43%; and refrigeration, 14%.

0006 Pickling remains a major form of preservation in

many countries because it: (1) yields desirable or-

ganoleptic qualities; (2) provides a means for

extending the processing season of fruits and vege-

tables; and (3) requires relatively little mechanical

energy input.

Outline of the Process

0007 Pickled products may be produced by one of three

methods, i.e. fermentation, acidification followed by

pasteurization, or refrigeration. Because they are rela-

tively straightforward, the methods for producing

pasteurized and refrigerated pickled products will be

described first.

Pasteurized Pickles

0008 Vegetables which are fresh or only partially fer-

mented may be preserved by the addition of vinegar

or acetic acid and subsequent pasteurization. Vinegar

alone is not sufficient to insure product safety, and so

requires an additional form of preservation such as

heat or refrigeration. The steps involved in producing

pasteurized or ‘fresh-pack’ pickles are the following:

0009 slice, cube, or dice product;

0010 place in clean container;

0011 mix water, salt, vinegar, sugar, spices and bring to

boil;

0012 add hot brine to container;

0013 seal and pasteurize.

0014 Two possible pasteurization methods include: (1)

heating such that the center of the jar or can reaches



C, and holding for 15 min, followed by a prompt

cooling to 35



C or below, or (2) heating at 70



C for

10 min, followed by prompt cooling. (See Vinegar.)

0015 The pasteurization process essentially destroys

spoilage microorganisms and prohibits fermentation

from occurring. Both acid-forming bacteria, which

are active in brine fermentation, and yeasts, which

cause gas production, are destroyed by pasteuriza-

tion. The pasteurization process inhibits polygalac-

turonase, the enzyme responsible for pickle

softening. Enzyme activity may also be controlled

through use of appropriate salt concentrations. Cal-

cium chloride is often added to brine to aid in firming

cucumber pickles. Pasteurized pickled products have

steadily gained in popularity, and have a very differ-

ent flavor and texture to that of fermented pickled

products. (See Pasteurization: Principles.)

Refrigerated Pickles

0016Refrigerated pickle products, which represent the

latest development in pickling technology, are pro-

duced by direct acidification and addition of sodium

benzoate or another preservative. In these nonfer-

mented pickles, the preservative takes the place of

pasteurization in preventing spoilage of the product.

This process is essentially the same as that used for

pasteurized pickles, but instead of pasteurizing, the

sealed containers are refrigerated. It is essential that

this type of pickle is kept refrigerated throughout

the production process and during subsequent

consumption.

Fermented Pickles

0017Cucumbers are by far the most common vegetable

fermented; therefore, most of the following processes

will be described using cucumbers as an example.

There are three general methods which may be used

for cucumber fermentation; (1) salt stock; (2) genuine

dill; and (3) overnight dill.

0018Salt stock The first method, salt stock, involves fer-

mentation in 5–8% sodium chloride until all ferment-

able sugars have been converted to acids and other

end products. The cucumbers are then stored in open

tanks containing 10–16% salt to maintain stability

for up to 1 year. Figure 1 outlines the general process

for salt stock pickles. Desalting to an acceptable

organoleptic level (2–2.5% salt) is carried out by

Harvest

Transport

Grade

Presalting treatment

Tank

Salt

Ferment

Store

Further process

Final products

fig0001Figure 1 General flowchart for preservation of vegetables by

brining. Reproduced from Fleming HP and McFeeters RF (1981)

Use of microbial cultures: vegetable products. Food Technology 1:

84–88, with permission.

4564 PICKLING