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Cows’ milk in some parts of Austria, Germany, and

Switzerland reached activity concentrations of several

hundred becquerels per liter during the first week of

May. Owing to its short half-life, radioiodine disap-

peared quickly from the environment, and the two

cesium nuclides became dominant. As shown in

Figure 3, the levels of

Sr were little affected in

Central Europe. Released radionuclides of low vola-

tility, such as plutonium, were deposited mostly in the

near vicinity of the accident site.

0013 The results presented in Figure 2 allow a compari-

son of radiocesium in total diet after the Chernobyl

accident with that observed at the time of atmos-

pheric testing of nuclear weapons. The data of the

preChernobyl years represent

137

Cs alone (measur-

able levels of

134

Cs were not present in the fall-out

from weapons tests), whereas those of the first

postChernobyl years also show

134

Cs, which – owing

to its short half-life – had fallen to below measurable

levels by 1990. It may seem surprising that Figure 2

indicates a higher radiocesium ingestion in 1987 than

in 1986. This is mostly due to the fact that in 1986,

radioactivity from Chernobyl played a role only from

May to December. With the exception of milk and

fresh fruit and vegetables, most of the food and feed

consumed in 1986 came from the harvest of 1985;

only when the preChernobyl supplies of grain, pota-

toes, and frozen and canned foods had been largely

exhausted, was the peak daily intake of 11 Bq of

137

Cs and 5 Bq of

134

Cs reached in March 1987.

0014Activity concentrations of

137

Cs in various food-

stuffs in the years 1986 and 1996 are presented in

Table 2, with the natural

K-levels for comparison.

As in Figure 2, the data are based on the situation in

1960 1965 1970 1975

Bq (d*p)

−1

1980

Cs-137

Cs-134

1985 1990 1995 2000

fig0002 Figure 2 Annual average intake of radiocesium (Bq per day per person); daily total diet samples collected in the Federal Republic of

Germany, 1963–1996. Source: Federal Research Center for Nutrition, Karlsruhe, data bank ‘Leitstelle Umweltradioaktivito

t.’

0.0

0.5

1.0

1.5

Bq (d*p)

−1

1960 19701965 1975 1980 1985 1990 1995 2000

Sr-90

fig0003 Figure 3 Annual average intake of radiostrontium (Bq per day per person); daily total diet samples collected in the Federal Republic

of Germany, 1960–1997. Source: Federal Research Center for Nutrition, Karlsruhe, data bank ‘Leitstelle Umweltradioaktivito

t.’

4906 RADIOACTIVITY IN FOOD

the Federal Republic of Germany. In all areas, the

local deposition of Chernobyl fallout varied consider-

ably, mostly depending on the amount of rainfall

during the critical days (‘washout effect’); the radio-

activity in crops and animal products differed accord-

ingly, samples taken in southern Germany generally

showing two- to fivefold higher contamination than

those taken further north. In Switzerland, milk pro-

duced in the Kanton of Ticino had 10 times higher

activity concentrations of

131

I and radiocesium than

milk from the area around Geneva. Data given in the

1986 column of Table 2 can therefore only serve as a

rough approximation. In field crops and products

obtained from farm animals, the

137

Cs concentration

had returned to the preChernobyl level by 1996; ven-

ison, wild growing mushrooms and blueberries, and

fish from the Baltic Sea still showed elevated levels of

radioactivity, although these do not seem to be high

when compared with the natural levels of

K. Accu-

mulation of cesium in mushrooms is species-depend-

ent; in the first years after the Chernobyl accident

some species, such as Xerocomus badius, reached

radiocesium levels of many thousands of becquerels

per kilogram in some samples, whereas other species

growing in the same habitat accumulated very little

radioactivity. The sometimes very high concentra-

tions of radiocesium in venison are at least partly,

perhaps primarily, due to consumption of mushrooms

by the animals. High radiocesium activities in wild

growing blueberries and other species of forest berries

are probably due to the generally more acidic pH of

forest soils, which makes cesium more available to

absorption by plant roots.

Radiation Exposure from Incorporated

Radionuclides

Natural Exposure

0015Radioactivity alone, measured in becquerels, does not

provide enough information to evaluate possible risks

associated with the intake of radionuclides, because

one becquerel of one radionuclide does not usually

have the same biological effect as one becquerel of

another radionuclide. It is the amount of energy de-

posited in living tissues that primarily determines the

possible biological effects of radiation. The radiation

energy imparted per gram of tissue, the type of radi-

ation (a, b, g), the distribution of the particular radio-

nuclide in the body and its rate of excretion, and the

different vulnerability to radiation of different tissues

and organs must all be taken into account. Following

procedures developed by ICRP (the International

Commission for Radiological Protection), the effect-

ive dose can be calculated, taking all these factors into

consideration. It was formerly called the ‘effective

equivalent dose;’ it is an approximate measure of

the actual (‘effective’) risk of genetic and somatic

radiation damage to man during the remaining life

time. For brevity it is simply referred to as ‘dose’ in

the following discussion – unless the full term is re-

quired for clarification. The dose unit is called the

sievert (Sv), and 1 Sv is defined as 1 J kg

1

0016Following the ICRP procedure, the annual dose

caused by ingestion of various naturally occurring

radionuclides has been estimated to be 380 mSv for

adults (world-wide average), with

K making the

largest single contribution (Figure 4). A comparison

of Figure 4 with Table 1 shows that the radionuclides

of the uranium and thorium series contribute signifi-

cantly to the ingestion dose in spite of their low

activity concentration in the diet. This is partly due

to the higher vulnerability of biological systems to a

radiation as compared to b and g radiation, but the

long biological half-life of some of these a emitters

also plays a role. (Biological half-life is the time re-

quired for the human or animal organism to eliminate

half of a given substance).

0017It would be difficult – and not advisable – to try to

achieve a total ingestion dose of much less than

380 mSv by resorting to special diets. Potassium (and

with it

K) is an essential mineral under close homeo-

static control in the body. Carbon (and with it

C) is

contained in all foods. The elements of the uranium

and thorium series are present in most foods of plant

tbl0002 Table 2 Typical activity concentrations of

137

Cs in various

foodstuffs of the postChernobyl harvest (1986) in Germany,

compared with annual (arithmetic) mean concentrations in the

year 1996, and with concentrations of

Food Bq per kilogram freshweight

137

Cs (1986)

137

Cs (1996)

Wheat 7 0.11 130

Barley 12 0.15 140

Rye 16 0.21 140

Potatoes 3 0.17 130

Peas 7 0.04 98

Carrots 5 0.15 80

Apples 20 0.13 40

Wild blueberries 140 54 22

Wild mushrooms (up to 2  10

) 170 95–170

Beef 50 1.1 115

Pork 19 0.33 115

Veal 41 1.3 115

Venison (roe deer) (up to 10

) 50 100

Hens’ eggs 5 0.1 23

Cows’ milk 8 0.2 46

Fish from the Baltic Sea 4 9 90–140

Fish from the North Sea 3 0.5 90–140

Source: Federal Research Center for Nutrition, Karlsruhe, data bank

‘Leitstelle Umweltradioaktivito

t.’

RADIOACTIVITY IN FOOD 4907

or animal origin, although at very low concen-

trations. Populations living in areas where the soils

are rich in uranium/thorium minerals or individuals

regularly consuming reindeer meat, brazil nuts,

or shellfish can reach annual exposure levels of

1000 mSv.

0018 Ingested radionuclides are not the only source of

radiation to which man is inevitably exposed. Inhal-

ation of the natural radionuclides

222

Rn and

220

causes an annual dose of 1000 mSv (Figure 4). This

must be seen together with an annual external dose

of f650 mSv, of which 250 mSv come from cosmic

radiation and 400 mSv from terrestrial radiation, for

instance the gamma radiation emitted from

K pre-

sent in the soil and in building materials. The dose

from ingested natural radionuclides thus contributes

19% of the total dose of 2030 mSv from all natural

sources.

0019 Actual dose levels can vary widely above and

below the average values presented in Figure 4. The

contribution from cosmic radiation increases with

increasing altitude; that from terrestrial radiation

and from inhalation fluctuates considerably with

local geological conditions. In Switzerland, for in-

stance, the average dose from cosmic radiation is

350 mSv, from terrestrial radiation 450 mSv and from

inhalation 1600 mSv; the internal dose of 380 mSv

contributes 14% to the total dose of 2780 mSv from

all natural sources. Recent studies from several coun-

tries tend to assign higher dose contributions to inhal-

ation of radon, sometimes also to cosmic and

terrestrial radiation, with the effect of lowering the

contribution from ingestion to 12% and even less.

Man-made Exposure

0020The average intake of

137

Cs from fallout in 1964

reached 9 Bq per day in Central Europe (Figure 2),

or 3280 Bq in the whole year. For adult individuals,

this meant an effective dose of 46 mSv. The daily

intake of 1.1 Bq of

Sr (Figure 3), or 400 Bq per

year, added 14 mSv. In all, the intake of fallout radio-

activity up to 1985 in adults living in Central Europe

resulted in a lifetime dose of 240 mSv from

137

Cs and

160 mSv from

Sr.

0021The effect of the Chernobyl disaster on the internal

dose received by adults in the Federal Republic of

Germany during the years 1986–1993 is demon-

strated in Table 3. The data were calculated from

the intake (Bq per year) with total diet (Figures 2

and 3), using the ICRP’s conversion factors. For com-

parison, the external dose from radiocesium deposited

on the ground is also shown. Inhalation of radio-

nuclides occurred only during the few days when the

radioactive cloud was present, and the dose resulting

from inhalation was negligible, compared with that

from ingestion and from external radiation. An inges-

tion dose of 3 mSv caused by

131

I during 1986 was not

included in the table, because radioiodine had disap-

peared after a few weeks. It should be noted that a

small part of the exposure caused by

137

Cs and a large

tbl0003 Table 3 Annual effective dose from ingestion and from external exposure to man-made radionuclides (adults, Germany)

Calendar year Ingestion dose (mSvper person) External dose resulting fromradiocesium (mSvper person)

13 7

13 4

Sr Sum of columns 2^4

1986 21.5 14.6 4.4 40.5 70

1987 37.8 22.0 3.3 63.1 30

1988 9.2 5.4 2.2 16.8 25

1989 4.5 2.2 2.8 9.5 21

1990 2.5 1.7 2.9 7.1 20

1991 1.8 1.6 3.4 19

1992 1.6 1.5 3.1 18

1993 1.2 1.6 2.8 17

Total 80.1 45.9 20.3 146.3 220

Source: Federal Research Center for Nutrition, Karlsruhe, data bank ‘Leitstelle Umweltradioaktivito

t.’

1000 µSv

inhalation

(49%)

250 µSv

cosmic

(12%)

400 µSv

terrestrial

(20%)

380 µSv

ingestion

(19%)

190 µSv

20 µSv

and others

20 µSv Th-series

160 µSv U-series

fig0004 Figure 4 Effective dose from natural sources of radiation. The

dose from incorporated radionuclides contributes 19% of the

total of 2030 mSv per person.

4908 RADIOACTIVITY IN FOOD

part (around 90%) of that caused by

Sr originated

in the nuclear test fallout of the 1960s rather than the

Chernobyl accident. Except for the year 1987, the

dose from external radiation was always higher than

that from ingestion, and the relative importance of

external exposure will grow as time progresses. Dis-

regarding the contribution from

Sr and adding that

from

131

I, the ingestion dose attributable to the

Chernobyl accident reached about 129 mSv by 1993

and is unlikely to exceed a total of 140 to 150 mSv in

the future. In the UK, the average effective dose

resulting from ingestion of radionuclides from Cher-

nobyl has been estimated to be less than 20 mSv. These

calculated lifetime doses are small compared with an

annual dose of 0.38 mSv from ingestion of natural

radionuclides. They are also small compared with

the ICRP annual dose limit of 1 mSv for the general

public. The large regional variations in deposition

and in activity concentrations of groups of foodstuffs

observed in Germany, Switzerland, and other coun-

tries were not reflected in similarly large variations of

the internal radiation dose. Even farm families now-

adays buy much of their food in supermarkets, where

products from many parts of Europe and from over-

seas are offered. As a result, ingestion dose levels in

different areas of one country rarely differ by a factor

of more than two.

0022 A dissimilar situation prevails in the area surround-

ing the accident site. There, the highest contribution

to the effective dose received during the first year

came from external gamma radiation (50%), and

about 25% each from inhalation and ingestion. The

radionuclide contributing the highest fraction of

the total dose was

131

I. Retrospective calculations

indicate that some 270 000 living in an area of

10 000 km

have received a total dose of > 50 mSv,

most of it during the first year. The former Soviet

Government set a ‘temporary dose limit’ of 100 mSv

(combined internal and external) for the population

during the first year after the accident. In an effort to

minimize the number of persons exceeding this limit,

some 135 000 people were evacuated from a 30-km

zone around the reactor. For various periods of time,

the sale of various locally produced foodstuffs was

restricted. Among the inhabitants who stayed or

returned in the meantime, those living in towns

could purchase uncontaminated food brought in

from other regions. However, many of the people in

the area live on small farms, and they and their do-

mestic animals eat crops from their farms. Radioce-

sium in the soil of the family farm is now the main

source of human contamination. As a consequence of

high

131

I-exposure during the first few weeks after

the accident, both from inhalation and food intake

(especially milk), the incidence of thyroid cancer in

children and adolescents has sharply increased in the

more severely affected areas of Belarus and the

Ukraine in the years since 1990, with a less pro-

nounced increase in the bordering area of the Russian

Federation. Other consequences reported in the

media, such as an increased incidence of leukemia or

other forms of cancer, have not been confirmed by

scientific investigations. However, since the peak in

the incidence of radiation-induced cancer may occur

more than 10 years after the exposure, final conclu-

sions concerning the long-term health effects attrib-

utable to radioactive contamination must await the

results of ongoing epidemiological studies.

Regulation and Control

0023Most countries have established systems of govern-

mental control of environmental radioactivity in the

1960s, including surveillance of food. In Europe, the

EURATOM Treaty, which came into effect in 1958,

obliged member countries to organize the surveillance

of radioactivity in air, water, and soil, and to report

the results annually to the European Commission.

Milk was later included in the system, followed by

certain other foodstuffs. After the Chernobyl acci-

dent, many national and regional authorities had

taken steps to limit the intake of man-made radio-

nuclides by setting maximum permitted levels of ac-

tivity concentration in foods. These limits varied

widely, and such variations did not inspire confidence

in a wary public. The Commission of the European

Communities announced a European Community

Regulation on 31 May 1986, setting the following

limits for radiocesium (i.e.,

137

Cs plus

134

Cs): milk

and milk products 370 Bq l

1

, baby food 370 Bq kg

1

all other foods 600 Bq kg

1

. These limits initially ap-

plied only to foods imported into the EC, but were

subsequently applied also to the internal market.

Some countries outside the EC adopted more strin-

gent standards, some going so far as to require the

complete absence of

134

Cs and

137

Cs or even – forget-

ting the presence of natural radionuclides –‘zero

radioactivity.’ This caused considerable difficulties

in world food trade. In an effort to overcome the

confusion, the Codex Alimentarius Commission has

proposed the Guideline Levels cited in Table 4.A

higher dose per unit intake factor (Sv/Bq ratio), as it

applies to the a-emitting nuclides of americium and

plutonium, demands a lower Bq kg

1

limit than the

lower intake factor of the g emitters, with the bone-

seeking b emitter

Sr taking a position in between.

Because of the high sensitivity of the young thyroid

to radioiodine, the limit for

131

I in infant food

and milk is lower than in food destined for general

consumption.

RADIOACTIVITY IN FOOD 4909

Countermeasures

0024 In the 1960s and again after Chernobyl, many pro-

posals for the removal of radionuclides from the food

chain or for the reduction of activity concentrations

in foods have been published. Radioactive contamin-

ants adhering to the surface of vegetables and fruit

can be largely removed by washing, removal of outer

leaves, or peeling. In the process of milling, much of

the radioactivity in grain remains in the bran, low-

extraction flour being more or less free of radioactive

contamination. Dairy processing of milk produces

butter that is essentially free of nuclides of cesium or

strontium. If

131

I is present, the butter can be stored

until the radioiodine has disintegrated sufficiently.

Acid precipitation of curd leaves almost all radioce-

sium, -strontium, and -iodine in the whey, thus pro-

ducing decontaminated cheese, whereas in enzymatic

(rennet) precipitation, most of the radiostrontium

originally present in milk is found in the curd. Many

studies, some of them on a semi-industrial scale, have

been carried out on the removal of cesium and stron-

tium ions from liquid food (milk, fruit juices, tomato

juice) by ion exchange or electrodialysis. Efficient

decontamination can be achieved, but the treatments

are relatively expensive. Some authors have described

undesirable effects on sensory quality or on nutri-

tional value. Many of these studies were probably

carried out with a war situation in mind, when food

would be at a premium. Should another nuclear

disaster occur during peacetime, it will be more eco-

nomical under most circumstances to bring in uncon-

taminated products from other areas than to try to

decontaminate food by procedures more costly than

simple washing or peeling.

0025 Another approach is the reduction of contamin-

ation during agricultural production of food. Con-

tamination of farm animals can be reduced by

keeping them indoors during the fallout period.

Root uptake of radiocesium in relatively acid soils

can be minimized by liming. The fecal excretion of

radionuclides can be greatly increased and their

uptake into meat and milk minimized by adding ad-

sorbents, such as bentonite or complexing com-

pounds, such as ammonium ferric hexacyanoferrate

(Prussian Blue), to the feed. The efficiency of such

methods is high, and the cost is moderate.

0026The assessment of the radiological impact of re-

leases of radionuclides to the terrestrial and fresh-

water aquatic environments requires knowledge of

the transfer of various radionuclides from soil to

plants, plants to animals, and food to man, and of

the many factors that influence the rates of transfer.

Numerous studies have been carried out with this aim

since the 1960s; tables of transfer coefficients are

available. Complex mathematical models, such as

ECOSYS, have been developed to permit prediction

of the biological consequences of a major radioactive

release. Experience after the Chernobyl catastrophe

has shown that these systems, when fed with solid

data, allow reasonably accurate predictions to be

made. In contrast, many of the population dose

estimates announced soon after the accident under

the pressure of circumstances later turned out to be

several-fold too high.

See also: Adulteration of Foods: Detection; Analysis of

Food; Immunoassays: Radioimmunoassay and Enzyme

Immunoassay; Protein: Synthesis and Turnover

Further Reading

Carter MW (ed.) (1988) Radionuclides in the Food Chain.

Berlin: Springer.

Codex Alimentarius (1995) Levels of Radionuclides,

Volume 1 – 1995, Section 6.2, CAC/GL 5-1989.

Rome: Codex Alimentarius Commission.

Diehl JF, Frindik O and Mu

ller H (1989) Radioactivity in

total diet before and after the Chernobyl reactor acci-

dent. Zeitschrift fu

r Lebensmittel-Untersuchung und

-Forschung 189: 36–38.

tbl0004 Table 4 Codex Alimentarius Guideline Levels for radionuclides in foods

Dose per unitintake factor (SvBq

1

) Representative radionuclides Guideline level (Bq kg

1

)

Foods destined for general consumption

6 241

Am,

239

Pu 10

790

Sr 100

8 131

134

Cs,

137

Cs 1000

Milk and infant foods

5 241

Am,

239

Pu 1

7 131

Sr 100

8 134

Cs,

137

Cs 1000

Guideline Levels are intended for use in regulating foods moving in international trade. When the Guideline Levels are exceeded, governments should

decide whether, and under what circumstances, the food should be distributed within their territory or jurisdiction. The levels indicated above are

designed to be applied only to radionuclides contaminating food moving in international trade following an accident and not to naturally occurring

radionuclides that have always been present in the diet. The Guideline Levels remain applicable for one year following a nuclear accident.

4910 RADIOACTIVITY IN FOOD

European Commission (1996) The Radiological Conse-

quences of the Chernobyl Accident. Proceedings of the

First International Conference, 18–22 March 1996,

Minsk, Belarus. Report EUR 16544. Brussels.

IAEA (1989) Measurement of Radionuclides in Food and

the Environment. A Guidebook. Vienna: International

Atomic Energy Agency.

IAEA (1994) Handbook of Parameter Values for the Pre-

diction of Radionuclide Transfer in Temperate Environ-

ments. Vienna: International Atomic Energy Agency.

McDonald P, Jackson D, Leonard DRP and McKay K

(1999) An assessment of

210

Pb and

210

Po in terrestrial

foodstuffs from regions of England and Wales. Journal

of Environmental Radioactivity 43: 15–29.

Ministry of Agriculture, Fisheries and Food (1994) Radio-

nuclides in Foods. Food Surveillance Paper No. 43.

London: HMSO.

ller H and Pro

hl G (1992) ECOSYS-87. A dynamic

model for assessing radiological consequences of nuclear

accidents. Health Physics 64: 232–252.

hm W, Steiner M, Kammerer L, Hiersche L and Wirth E

(1998) Estimating future radiocaesium contamination of

fungi on the basis of behaviour patterns derived from

past instances of contamination. Journal of Environ-

mental Radioactivity 39: 129–147.

UNSCEAR (2000) Sources and Effects of Ionizing Radi-

ation, UN Committee on the Effects of Atomic Radi-

ation (UNSCEAR), 2000 Report to the General

Assembly. New York: United Nations. (Also earlier

reports of the UNSCEAR series.)

Woodman RFM and Nisbet AF (1999) Derivation of

working levels for radionuclides in animal feedstuffs

for use following a nuclear accident. Health Physics

77: 383–391.

Radioimmunoassay See Immunoassays: Principles; Radioimmunoassay and Enzyme Immunoassay

Raising Agents See Leavening Agents; Yeasts

Raisins See Grapes

Raman Spectroscopy See Spectroscopy: Overview; Infrared and Raman; Near-infrared;

Fluorescence; Atomic Emission and Absorption; Nuclear Magnetic Resonance; Visible Spectroscopy and

Colorimetry

RAPE SEED OIL/CANOLA

N A M Eskin and R Przybylski, University of

Manitoba, Winnipeg, Manitoba, Canada

Introduction

0001 Oilseed rape species that produce canola oil and meal

are from the Brassica genus in the Cruciferae family.

It was first cultivated in India almost 4000 years ago.

Large-scale plantings of oilseed rape were first

reported in Europe in the thirteenth century. The

Brassica species probably evolved from the same

common ancestor as wild mustard (Sinapis), radish

(Raphanus), and Eruca.

Development of Canola

0002Rapeseed was first introduced into Canada from

Poland in 1936. Because of oil shortages during

RAPE SEED OIL/CANOLA 4911

World War II, Brassica rapa seeds were tested for

agronomic adaptation. At the same time, rapeseed

(B. napus) seeds of Argentinean origin were obtained

from the USA and grown under contract in the Pro-

vince of Saskatchewan. During the war years, acreage

increased with the first rapeseed crushing plant

built in 1945. The first Canadian B. napus cultivar,

Golden, was registered in 1954, followed by Echo,

the first Canadian cultivar of B. napus in 1964. Oil

shortages during the war suggested that Canada must

develop its own domestic oil supply. Because of its

agronomic adaptation, rapeseed was selected.

0003 Early rapeseed cultivars, however, had very high

levels of eicosanoic and erucic acids in the oil as

well as glucosinolates in the meal. These factors

were of concern if rapeseed were to be marketed for

human consumption and approved by the Food and

Drug Directorate of the Department of National

Health. High levels of erucic acid were shown to

produce fatty deposits in the heart, skeletal muscles,

and adrenals of rodents as well as impair the animal’s

growth. Plant-breeding programs were initiated to

reduce the level of erucic acid in rapeseed oil. In

1959, Liho, a rapeseed line containing low levels of

erucic acid was identified. A program of backcrossing

and selection was conducted to transfer the low-

erucic trait into agronomically adapted cultivars.

This led to the release of the first low-erucic-acid

cultivar of B. napus, Oro, in 1968 and the first

low-erucic-acid B. rapa cultivar, Span, in 1971.

Because of health concerns related to high levels of

erucic acid, over 95% of the rapeseed grown in

Canada in 1974 were low-erucic-acid varieties.

0004 Glucosinolates were also considered detrimental

in rapeseed meal fed to poultry and ruminants. Its

hydrolyzed products, isothiocyanates and other

sulfur-containing compounds, were shown to inter-

fere with the uptake of iodine by the thyroid gland,

contribute to liver disease, and reduce growth and

weight gain in animals. Consequently, breeders real-

ized that if rapeseed meal were to be used in animal

feed, the glucosinolate content had to be reduced. A

Polish line with a low-glucosinolate trait, Bronowski,

was identified by Dr. Keith Downey in the late 1960s.

Breeding efforts to introduce this trait into low-erucic

lines by Dr. Baldur Stefannson resulted in the release

of the world’s first low-erucic, a low-glucosinolate

cultivar of B. napus. This was followed in 1977, by

the release of the first low-erucic, low-glucosinolate

cultivar of B. rapa, Candle, by Dr. Keith Downey.

Approximately 80% of the total Canadian rapeseed

acreage in 1980 consisted of the double low cultivars.

(See Glucosinolates.)

0005 The name ‘canola’ was registered by the Western

Canadian Oilseed Crushers in 1978. The name

included those cultivars containing less than 5%

erucic acid in the oil and 3 mg per gram of aliphatic

glucosinolates in the meal. The canola trademark was

subsequently transferred to the Canola Council of

Canada in 1980. In 1986, the definition of canola

was amended to B. napus and B. rapa lines with less

than 2% erucic acid in the oil and less than 30 mmol

per gram of glucosinolates in the air-dried oil-free

meal and was added to the ‘generally recognized as

safe’ (GRAS) list of food products in the USA.

0006It was much more difficult to introduce the low-

erucic-acid trait into the European rapeseed lines

because they were primarily of the winter type. This

extended the time required to produce each gener-

ation and crosses between spring low-erucic-acid

rapeseed (LEAR) cultivars and winter lines resulting

in undesirable segregates. Nevertheless, the develop-

ment of European LEAR varieties was accomplished

within 15 years. European acreage of rapeseed de-

clined during the 1970s as a result of health concerns.

In 1977, the low-erucic-acid trait was mandatory in

Europe in 1977. Initially, the new LEAR cultivars

produced lower yields and oil content compared

with the traditional cultivars. Subsequent plant

breeding overcame this problem with European pro-

duction of LEAR increasing substantially by 1984.

Distribution and Adaptation

0007Canola is the only oilseed crop adapted to temperate

regions. Its ability to germinate and grow at low

temperatures permits production in cooler regions

and at higher elevations compared with other oilseed

crops. As a result, it can be grown as a winter crop in

Europe where the winters are not too severe. The

major producers of canola and rapeseed are China,

European nations, India, and Canada, with Canada,

China, and India accounting for over 65% of the

world’s total production.

0008Different species of Brassica crops are grown

throughout the world, although B. napus and

B. rapa are both grown in Canada. B. napus is

higher-yielding as well as slightly higher in oil and

protein content than B. rapa. However, B. rapa

matures 2–3 weeks earlier and can be seeded in

areas with a shorter growing season (less than

95–110 days). In addition, B. rapa is shorter, more

shatter-resistant and frost-resistant, containing less

chlorophyl and fiber than B. napus. The main canola

species grown in western Canada are spring types,

except for a small amount of high-erucic-acid rape-

seed (HEAR) grown for industrial purposes. Winter

cultivars of both B. napus and B. rapa are grown

throughout Europe, except Sweden. In northern

Sweden, spring types predominate. In the Indian

4912 RAPE SEED OIL/CANOLA

subcontinent, high-erucic-acid, high-glucosinolate

spring B. juncea and some B. rapa types are grown.

Winter types of B. napus and B. rapa are grown in

central and southern China, whereas spring types

predominate in western China. Spring B. juncea is

also found in China. Asia still grows mainly the

HEAR varieties.

Development of New Cultivars

0009 During the last 20 years, breeding goals in Canada

included increasing yields, oil and protein contents,

earlier maturity, development of yellow seeded

varieties, reduced green seed, and improved disease,

insect, and herbicide resistance. The first triazine

tolerant cultivar was released in Canada in 1984,

followed by agronomically improved Tribute.

0010 Genetic breeding is now used to modify oil quality.

Using mutagenesis, a low-linolenic (C18:3)-acid cul-

tivar, Candle, was developed. Similar techniques by

researchers at Pioneer Hybrid produced a mutation

that blocked the desaturation of C18:1 to C18:2,

producing a high-oleic (C18:1) oil. The resulting mu-

tation was then crossed with low-linolenic (C18:3)

cultivars producing a high-oleic/low-linolenic line.

A successful transformation by Calgene produced

canola strains high in stearate (C18:0) and high in

laurate (C12:0), with future plans for high-palmitate

(C16:0) lines.

Oil Production

0011 Canola/rapeseed oil accounts for 16% of the world

supply of edible oils compared with 32 and 18% for

soybean and palm and palm kernel oil, respectively.

In 1997, canola oil accounted for 70.4% of all

deodorized fats and oil, 72.8% of the vegetable

oils, and more than 80% of the salad oils produced

in Canada. The growing demand for canola prod-

ucts resulted in 424 000 tonnes of oil to the USA

in 1996–1997, accounting for over 80% of the

total oil exports. (See Vegetable Oils: Types and

Properties.)

Canola Oil Extraction

0012 On an 8% moisture basis, canola seeds contain be-

tween 38 and 44% oil. The most efficient method for

extraction involves mechanical pressing or expelling

in which 60% of the total oil is released. The

remaining 40% is solvent-extracted, the common

practice for most other oilseeds. The various stages

involved are summarized below. (See Vegetable Oils:

Oil Production and Processing.)

Seed Cleaning

0013The first step is designed to remove weed seeds, grain

seeds, other foreign material as well as any canola

seed fragments. This involves a combination of aspir-

ation and screening. The foreign material removed

accounts for less than 2.5% of the remaining seed

and is used for animal feed.

Preconditioning

0014This involves preheating the seeds prior to flaking to

temperature of 30–40



C. This is achieved directly

with a fluid bed type using hot air or steam or indir-

ectly in rotary kilns equipped with steam-heated coils.

This renders the seed more pliable, preventing it from

shattering.

Flaking

0015The preheated seed is then flaked on smooth-surface

rolling mills. This can be performed using a single-

stage operation or as two separate stages; flakes of

0.2–0.3 mm thickness are obtained.

Cooking

0016Flakes are indirectly heated on steam-heated surfaces

in stack cookers or in rotary cookers with steam coils.

The cooking temperature is held between 75 and

100



C. In order to adjust the moisture content of

the material to 5–7% for the expeller operation, am-

bient air may be admitted to the cooking equipment.

Besides coelescing minute oil drops into large drops,

this step alters the protein and makes the oil more

extractable. In addition, it also inactivates a number

of enzymes, particularly myrosinase, responsible for

the hydrolysis of glucosinolates to sulfur-containing

compounds, lipases, and phospholipases responsible

for the formation of nonhydratable phosphatides.

Oil Extraction by Prepressing

0017The heat-conditioned flakes are then subjected to

continuous screw-presses or expellers to reduce the

oil content from around 42 to 16–20%. The expellers

are designed with a rotating screw shaft in a cylin-

drical barrel to allow oil to flow between the flat steel

bars of the barrel while retaining the solid material or

presscake.

Solvent Extraction

0018Before extracting with solvent, the presscake is cooled

with ambient air to minimize hexane vaporization

when it enters the extractor. The solids, now at

around 80



C, are washed with hexane in several

stages. In the first stage, hexane is already high in oil

content (miscella), followed by progressively leaner

RAPE SEED OIL/CANOLA 4913

miscella and ultimately pure hexane. A variety of

different extractors are available, all using some

type of countercurrent extraction system. The oil

content in the meal is reduced to around 1%,

depending on the type of equipment and throughput

rate, as well as on the type of cooking, flaking, and

prepress operations conducted. The resulting meal

and miscella are stripped to insure the production of

solvent-free meal and crude oil. The prepressed and

solvent-extracted canola oils are usually blended

before subjecting them to degumming.

Canola Oil Refining and Processing

0019 Crude canola oil is converted to an edible oil using the

same processing principles applied to other vegetable

oils. The following steps are typical for the overall

production of refined edible oils for food application.

Degumming

0020 This process removes phosphatides from the crude

oil, present at around 1.0–1.5% and measured as

phosphorus, 400–600 mg kg

1

0021 Two methods are used:

0022 Degumming with water in which oil at 80



Cis

intensely mixed with 2% water for 5–30 min in an

agitation tank or reactor. The majority of the

phosphatides are precipitated in suspension and

then removed by centrifugation leaving around

0.25–0.5% phosphatides or 100–200 mg per kilo-

gram of phosphorus in the oil. Nonhydratable

phospholipids are not removed by this process.

0023 Degumming with acid and water, also known as

‘superdegumming,’ also removes nonhydratable

phosphatides. This involves intensively mixing

the crude oil with 0.1–0.5% of a 50% solution

of citric or malic acids for up to 15 min, depending

on the mixing rate. Then, 2% of water is added,

before or after cooling the mixture to 25–45



and is mixed in a continuous stirred reactor for

1–3 h. The precipitated phosphatide particles are

removed by centrifugation. The phosphatides

remaining range from 5 to 50 mg per kilogram

of phosphorus, depending on the amount of non-

hydratable phosphatides in the crude oil.

Refining

0024 Degummed oils are further purified by bleaching

followed by either alkali refining or physical refining

process, winterization, and deodorization.

0025 Bleaching. Adsorptive bleaching is performed

with 1–3% of acid-activated clays to remove

colored components, metals, and phospholipids.

Oil is mixed with clay at 100



C under vacuum

for up to 30 min at 10–15% moisture, and then

clay is removed by filtration. Chlorophyls will be

reduced to below 0.05 mg kg

1

. Other adsorbents

are rarely used for canola oil.

0026Alkali refining. This is the most commonly used

process to remove phosphatides and free fatty

acids (FFA). Firstly, oil is mixed with 0.05–0.1%

concentrated phosphoric acid to precipitate phos-

pholipids. Secondly, the oil is treated with 12%

aqueous sodium hydroxide to neutralize FFA and

phosphoric acid, and precipitate phosphatides. In

both cases, intensive mixing and a short contact

time at 40–90



C are applied, followed by centri-

fugation, and then the oil is washed with water to

remove soaps. Alkali refining reduces FFA and

phosphorus to below 0.05% and 3 mg kg

1

respectively, chlorophylides are reduced by up to

70%, and iron and copper are removed.

0027Physical refining. The acid-degummed oil first

undergoes phosphoric acid pretreatment followed

by bleaching with acid-activated clay. The

bleached oil is then subjected to physical (steam)

refining which removes the free fatty acids by

steam distillation in the deodorizer.

0028Winterization. Salad oils are winterized to remove

wax esters, which can cause sediment formation in

oil. Oil is chilled to 5



C and filtered to reduce wax

content to below 50 mg kg

1

0029Deodorization. This process is performed for up to

an hour at 225–260



C under vacuum, 2–4mmof

mercury with 1–3% steam blown through the oil

to remove flavor components. During this process,

some tocopherols and sterols are removed from oil

together with FFA. When oil is cooled to 60–



C, additives are added, and spurging with ni-

trogen gas is performed.

0030Hydrogenation. Hydrogenation modifies the

melting and crystallization behavior of the fat or

oil as well as rendering it more resistant to oxida-

tive and thermal damage. This process is per-

formed at 160–200



C and 100–300 kPa pressure

in the presence of catalyst, usually nickel. During

this process, saturated and isomerized fatty acids

are formed that change the physical properties of

fat. Hydrogenated fats containing trans fatty acids

have a tendency to crystalize to the b

form produ-

cing products with a smooth and pleasing mouth

feel and good spreadability. Health concerns

have resulted in the reduction of trans isomers

by searching for new catalysts or by blending.

An alternative method to hydrogenation used in

Europe and only to a limited degree in North

America is interesterification.

0031Interesterification. This process is used to obtain

fats similar to hydrogenation by applying chemical

4914 RAPE SEED OIL/CANOLA

or enzymatic rearrangement of FA in glycerides

within oil and between oils. Chemical process is

performed with an alkaline catalyst, sodium meth-

oxide or sodium hydroxide, at 100–150



C for up

to an hour. The enzymatic process conditions are

dictated by the enzymes applied. The main advan-

tage of this method is that no trans fatty acid

isomers are formed.

Properties of Canola Oil

Physical

0032 The physical properties of canola, including density

and viscosity, the main engineering parameters, are

presented in Table 1.

0033 The density and viscosity of canola oil decrease

with temperature increase in a linear and exponential

fashion, respectively. Most of the canola oil physical

parameters are within the range found for other

vegetable oils and are governed by composition of

fatty acids.

Chemical

0034 The average composition of canola, rapeseed, and

soybean oils is presented in Table 2.(See Fats: Classi-

fication.)

0035 Triacylglycerols or triglycerides are the main com-

ponents of vegetable oils composed of glycerol and

three fatty acids attached to it. The composition of

triglycerides defines the physical properties of oils

and their oxidative stability. (See Fats: Classification.)

0036 Tocopherols are the natural and most efficient anti-

oxidants produced by plants. There are four isomers

of tocopherols produced, and canola oil contains

about twice as much g isomer than a, both isomers

being present in important amounts. The tocopherol

content in canola oil is at the higher end among

vegetable oils. (See Tocopherols: Properties and De-

termination.)

0037 Phytosterols or plant sterols have been neglected

for many years, although the nutritional importance

of some of these components is receiving considerable

attention. Some plant sterols appear to lower plasma

cholesterol by inhibiting the absorption of dietary

cholesterol and reabsorption of biliary cholesterol.

In fact, canola oil contains high amounts of sterols

second only to corn oil.

0038The sensitivity of canola oil to deterioration is

often related to the presence of pigments such as

chlorophyls. They are capable of transferring light

energy into chemical energy and can initiate forma-

tion of radicals responsible for oxidative degradation

of oils. The content of chlorophyls in canola oil is

dependent on the maturity of seeds used for process-

ing, as even fully matured seeds contain a few p.p.m.

of these components.

0039The presence of components containing sulfur in

the structure is normal for oils produced from oil-

seeds from the Cruciferae family because of the pres-

ence of glucosinolates. In canola oil, minor fatty acids

with sulfur in the structure have been detected.

0040The composition of fatty acids in canola oil is

unique when compared with other oils. Canola oil

contains the lowest amount of saturated fatty acids

and is second after olive oil in the content of oleic

acid. The presence of essential fatty acid, such as

linoleic and linolenic, is intermediate, both acids

being important nutrients in the control of cardiovas-

cular diseases. The main fatty acid that differentiates

canola oil from rapeseed oil is erucic acid, which was

reduced to less than 2% in canola.

Nutritional Properties

0041Dietary fats serves as an important source of energy

and essential fatty acids, and serves as a carrier for

fat-soluble vitamins. In addition, it makes an import-

ant contribution to the feeling of satiety, palatability

of food products, and textural properties of foods.

tbl0001 Table 1 Physical properties of canola oil

Parameter Value

Relative density (g cm

3

;20



C/water at 20



C) 0.914–0.917

Refractive index (n



C) 1.465–1.467

Viscosity (kinematic at 20



C; mm

1

) 78.2

Smoke point (



C) 220–230

Flash point, open cup (



C) 275–290

Specific heat (J g

1

at 20



C) 1.910–1.916

Thermal conductivity (W m

1

) 0.179–0.188

tbl0002Table 2 Composition of canola, rapeseed, and soybean oils

Component Canola Rapeseed Soybean

Triglycerides (%) 94–99 92–99 93–99

Phospholipids (%) Up to 0.1 Up to 0.1 Up to 0.2

Free fatty acids (%) 0.2–1.2 0.5–1.8 0.2–1.0

Tocopherols (p.p.m.) 700–1200 700–1000 1700–2200

Plant sterols (p.p.m.) 8810 6900 4600

Unsaponifiables (%) 0.5–1.4 0.5–1.4 0.5–1.6

Chlorophyls (p.p.m.) 5–35 5–35 Trace

Sulfur (p.p.m.) 3–15 5–25 Nil

Iodine value 110–126 97–108 120–135

Saturated fatty acids (%)

6–7 7 15

Oleic (18:1)

(%) 61 15 24

Linoleic (18:2) (%) 21 14 54

Linolenic (18:3) (%) 11 9 8

Erucic (22:1) (%) 0.2 45 Nil

Percentage in oil.

Abbreviation of fatty acids.

RAPE SEED OIL/CANOLA 4915