Smoke
Content
HeaIth aspects
of using smoke fIavours
as food ingredients
Health protection of consumers
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HeaIth aspects
of using smoke fIavours
as food ingredients
French edition;
Les aspects sanitaires de l'utilisation d'arômes de fumée comme ingrédients
alimentaires
ÌSBN 92-871-2188-5
Strasbourg, Council of Europe, Publishing and Documentation Service
ÌSBN 92-871-2189-3
c Council of Europe, 1992
Printed in Belgium
Contents
Page
Summary......................................................................................................... 5
Introduction............................................................................................... 6
I - GeneraI information
1.1 Historical background.................................................................................. 7
1.2 Definitions.................................................................................................... 8
II - Smoking technoIogy
2.1 Smoking technology.................................................................................... 9
2.2 What is in the smoke?................................................................................ 9
2.3 Smoking methods....................................................................................... 10
2.4 Smoke absorption by the food.................................................................... 10
2.5 Development in technology......................................................................... 12
2.6 Smoking food in private households and
catering sector.............................................................................................. 12
2.7 Smoke flavourings...................................................................................... 12
2.8 Application of smoke flavourings................................................................ 13
2.9 The technological importance of smoke..................................................... 13
III - ChemicaI composition of smoked food
3.1 Chemical aspects of smoked food............................................................... 15
3.2 Nitrogen oxides............................................................................................ 16
3.3 Smoke flavourings and
chemical aspects.......................................................................................... 16
IV - HeaIth aspects of smoked food and smoke fIavourings
4.1 General........................................................................................................ 18
4.2 PAH-components......................................................................................... 18
4.3 Nitrogen oxides and nitrosamines.............................................................. 19
4.4 Phenols....................................................................................................... 19
4.5 Other components and health aspects....................................................... 19
4.6 Health aspects of smoked food produced
by use of smoke flavourings......................................................................... 20
4.7 Conclusion................................................................................................... 20
V - CounciI of Europe guideIines concerning the
transmission of fIavour of smoke to
food..................................................................................................... 21
VI - BibIiography........................................................................................ 28
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Summary
Smoking of food like ham, sausages and other meat products, fish and fish
products and some cheese products has been used for centuries in many countries.
Originally the purpose was to preserve the food, partly by drying and partly by
adding antimicrobiological constituents like phenols from the smoke to the food.
Smoking is now primarily used to achieve the characteristic taste and
appearance of smoked food and to a minor degree to obtain preservation.The
traditional smoking process can be conducted in several ways, to give different food
products, both from an organoleptic point of view and in the light of health aspects.
Besides the traditional smoking process, the use of smoke flavouring
preparations based on smoke condensates and to some extent on artificial smoke
flavourings produced by mixing chemically defined flavouring substances has been
introduced in many countries.
As some of the constituents in the smoke and in the smoke condensates may
give rise to health problems, limits should be set for the quantities of these components
in the flavouring or in the final food e.g. for benzo(a)pyrene and volatile nitrosamines in
smoked food.
The Council of Europe Committee of Experts on Flavouring Substances has
drawn up guidelines for the evaluation of safety aspects of smoked food and the use of
smoke flavourings. The guidelines give guidance on the smoking process and the
production of smoke flavourings in order to minimise the possible formation of
substances of danger to health. Furthermore, limits in the flavourings and smoked foods
are suggested for impurities and constituents of danger to health. The guidelines do not
cover the microbiological aspects of food smoking as these were outside the remit and
expertise of the Committee.
The guidelines should enable governments, and especially producers and users
of the smoking process and smoke flavourings, to improve food safety.
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Introduction
The Council of Europe Committee of Experts on Flavouring Substances has
been working on the safety evaluation of flavouring preparations and flavouring
substances for many years.
One of the results of this work is the so-called "Blue Book",-" FLAVOURÌNG
SUBSTANCES AND NATURAL SOURCES OF FLAVOURÌNGS" where some two
thousand substances and some eleven hundred sources which have been evaluated
for safety are listed.
The "Blue Book" includes suggested limits for the use of flavourings in food and
beverages, based on technological and toxicological data and possibly on natural food
occurrence.
The "Blue Book" is used by many governments in Europe and by many
flavouring and food producers as a part of the safety evaluation of food for consumers.
Health aspects of many kinds of food items have, in recent years, been
discussed and investigated, and this is also the case for smoked food and the use of
smoke flavouring. Ìn any case it is always difficult to evaluate a traditional production
method, such as the smoking process - people have been eating smoked food for
centuries and feel that it is part of their traditional food.
However, for complex flavouring mixtures such as smoke flavourings, the expert
committee is preparing guidelines for conditions for the production of safe products and
for the safety evaluation of smoke flavourings.
As regards smoked food, the committee adopted a resolution in 1985 on
"Guidelines concerning the transmission of the flavour of smoke to food". The
resolution described the different methods in which a smoke flavour can be transmitted
to food and suggested components for which limits should be set.
The work has now been completed on the Council of Europe guidelines for the
production and evaluation of smoked food and smoke flavourings (See section V). The
principles in the guidelines are already being used in some countries and should
contribute to the wholesomeness of food.
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I - GeneraI information
1.1 HistoricaI background
Smoking of food has been used for centuries and its main purpose was originally
to preserve the food.
At first smoking of food might have been a side effect due to preservation by
drying in the fireplace.
Later on the process was developed and changed and was combined with other
processes e.g.to obtain a satisfactory shelflife for the food. Most food items have both
been smoked or either salted, dried, fermented or preserved in another way too, as
smoking alone does not ensure the food's proper lifespan.
For example, smoked ham such as Parma ham is both smoked and salted. By
combining the two processes, a product is obtained which is stable against a broader
spectrum of food-spoiling factors such as microorganisms and enzymes.
The use of the smoking process has also changed from being a process used at
home for storage of food to being mainly an industrial process, and now smoking in
most countries is only - or mostly - an industrial process.
The use of the process has also changed because of changes in the use of
other techniques. Nowadays most countries in Europe have effective preservation
methods such as cooling, heat treatment, canning and the use of preservatives.
Therefore in many countries the main purpose of smoking food is to give the product a
special taste, texture and appearance, and the preservation and antioxidative effect as
a result of the smoking process is of minor importance. Nevertheless, the smoking of
food still has some importance for the shelflife of some food products with regard to
inhibition of rancidity and growth of microorganisms.
Besides the production of smoked food by using the traditional smoking process,
the special taste in the smoked food can also be obtained by the use of "liquid smoke"
or a combination of both. The use of liquid smoke has developed during the twentieth
century because of health concerns regarding smoked food and due to technical and
economic reasons.
Ìn European and most other countries in the world the traditional smoking
process is used, but in some countries such as the USA smoking by the use of "liquid
smoke" is predominant in most of the industrial production of smoked foods.
The major advantage of using "liquid smoke" is the possibility of having a
continuous process, as the addition of the smoke preparation can be done as a step in
the production line. The smoke flavourings are then added by, for example, atomizing
them directly on the food.
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1.2 Definitions
Smoked food is food produced either by the use of a traditional smoking process
or by use of smoke flavourings or by a combination of the two methods.
Ìn principle, 4 different ways can be used to produce smoked food:
1. smoking with freshly generated smoke from wood,
2. smoking with smoke regenerated from smoke condensates,
3. flavouring with smoke flavour preparations derived from smoke
condensates,
4. flavouring with smoke flavours prepared by mixing chemically-defined
substances
The first method is the traditional smoking process and the 3 others are
performed by the use of different kinds of smoke flavourings or "liquid smoke".
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II - Smoking technoIogy
2.1 Smoking technoIogy
Ìn the traditionaI smoking process the first step is to make a fire using dried
wood. What kind of wood may depend on tradition and normally it will differ from
country to country. For instance in the United Kingdom the use of oak is common,
whereas in Denmark beech is normally used.
Generally speaking a kind of hardwood is used. Besides the use of wood, some
kinds of aromatic herbs and spices and twigs of junipers can be used in order to give a
special taste to the smoked products.
After having made the fire, the flames are reduced to a glow. The wood is then
decomposed by the high temperature in the ignition zone. The composition of the
smoke depends very much on the temperature in this area.
The period of time during which the food products are exposed to the smoke is
highly important for the flavour of the food.
This process can be regulated by several means including cooling of the smoke
and addition of water and/or air. By this regulation the flavour of the products can be
changed, but to some degree this regulation might also influence the formation of
unwanted impurities which are transported from the smoke to the food. As changes in
the composition of the smoke might also influence the taste of the food product,
changes like these would often have to be the result of a compromise.
The use of smoke flavourings often comprises atomizing of smoke flavouring
and then spraying it on to the surface of the food. The result in taste, appearance and
preservation is more or less the same as that obtained by using the traditional smoking
process.
2.2 What is in the smoke ?
Smoke from wood consists of several components: gases, liquid and solid
particles. Most of the smoke is air with a mixture of small particles of different size.
These particles spread the light and give the appearance of the smoke.
The particles in the smoke are to some degree left on the food, but this is only of
minor importance for the smoking process. Of major importance is the absorption of
gases by the food products. This is the part of the smoke which gives the characteristic
colour changes and flavour, while the particles are responsible for the antioxidizing
effect.
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2.3 Smoking methods
Smoking of food is nowadays mainly an industrial process, but in some countries
it seems to have become popular again in private households, for example among
fishermen. As the industrial process is of most importance, the different methods used
by industry will be described in detail. The methods used in private households are
similar to the industrial smoking processes, except that direct smoking is the method
most likely to be used.
Traditionally, smoking only allows limited possibilities for control of temperatures,
humidity, content of smoke, circulation and so on.
The development of equipment for smoking of food has concentrated on the
possibility of controlling all these factors.
The different methods are normally characterised by the temperature used:
- CoId smoking where the temperature is normally 18-20 degrees celsius. The
process is typically used for salmon, salamis, kippers, hams and special
cheese. A cold smoking process may last several weeks. Normally the
smoking process lasts for 6-24 hours.
- Warm smoking by a temperature around 40 degrees celsius is used for
bacon, sirloin and some types of sausage.
- Hot smoking is a combination of strong heating and smoke, which gives a
temperature in the products of 70-90 degrees celsius. Warm smoking is a
combination of a drying, cooking and smoking process.
This process normally takes some hours, but the smoking part of the process is
only part of this time. Products like herring, eel and some sausages are smoked in this
way.
2.4 Smoke absorption by the food
During the smoking process many different factors are of importance, and some
of them also influence the absorption of the smoke by the food.
Some of the factors which influence the absorption are:
- density of the smoke
- humidity
- temperature
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As far as the density of the smoke is concerned, the connection between this
factor and the absorption is simple: the higher the density, the greater the absorption of
the smoke, if all other circumstances are the same during the smoking process.
For food products which are warm smoked the surface is dried during the
process and the condensation of smoke particles on to the surface is less than on
products smoked at lower temperatures.
As a result of high smoke density more smoke particles are condensed on to the
surface of the food. Absorption of smoke components during the process is also
affected by humidity.
Ìf the relative humidity is high, steam will condense on the surface of the
products and the absorption of the water soluble parts of the smoke will increase. Ìf the
surface remains moist the formation of colour will be inhibited as colour formation is
increased by low water content. However, if the surface is too dry, penetration of the
smoke into the food will be decreased with a loss of flavour and preservative effects.
Ìn a modern, industrial smoking process where the smoke generator and the
smoking chamber are separated, the ability to control density of the smoke, humidity
and temperature is quite good. Besides this there is the possibility of carrying out certain
treatments on the smoke.
The smoke can be washed with water in order to remove some of the
components with high boiling points or filtered in order to decrease the content of, for
example, polycyclic aromatic hydrocarbons (PAH), which are substances of health
concern.
The problem with this process is that it will not only remove unwanted
components, but also some of the components which significantly influence the well-
known flavour of smoked food.
This problem also arises if other processes are used to minimise the content of
substances of health concern in the smoke. Changes in the smoking processes will
therefore have to be investigated carefully, as the result should be acceptable both from
a technological point of view and from a health point of view.
Heating of the smoke can be done by using steam, gas or electricity. Heating by
steam or electricity has a minor influence on the composition of the smoke but heating
by direct burning of gas in the smoking chamber can initiate some secondary reactions
because of the high temperature of the flame and may give rise to the formation of
nitrogen oxides in the smoke.
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2.5 DeveIopments in technoIogy
The following should be considered where new technology for the smoking
process is to be developed:
a. to get a better controlled process and thereby a better controlled
development of flavour and appearance
b. to reduce the amount of possible carcinogenic or other toxic components
in the smoke
c. to reduce the contamination of the environment by the smoking process
d. to increase the turnover in production
The development of electrostatic filters in order to remove unwanted particles
has been one of the results in this area, but it is estimated that the use of these filters is
not widespread. Water filters for the washing of smoke are more popular.
Another development is the use of smoke flavourings. This is a development
which is desirable in some industrial production lines, to create the possibility of having
a continuous production line, which is not interrupted by a separate and more time-
consuming smoking process. The use of smoke flavourings might also be important in
relation to the health aspects of smoked food.
2.6 Smoking food in private househoIds and the catering sector
Smoking of food is an industrial process in most European countries and is only
used as such to a limited degree in private homes. Nevertheless, modern smoking
equipment for private households is coming on to the market.
This equipment is sold for instance to fishermen and to people who are camping
as a leisure occupation in the summer. Some cookery books describe the process of
both cold and warm smoking. Ìn general it is the direct smoking of food which is
described.
The health aspects of smoking food in private households are the same as for
industrial smoking from a chemical/toxicological point of view. The microbiological
aspects are not considered here, but for home smoked food these aspects should be
considered carefully as the microbiological contamination can be quite severe, if strict
and proper hygiene control of the food and temperature is not kept.
2.7 Smoke fIavourings
Ìn addition to the traditional method of smoking, a smoke flavour can be added to
food by using smoke flavourings.
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Smoke flavourings can be divided into two main groups:
a. smoke flavourings made from smoke from burning wood
- condensed smoke possibly with adjuncts added and where some
components of health concern may have been removed
b. synthetic smoke flavourings
The condensed smoke flavourings are made by condensation of smoke, usually
followed by fractionation and purification.
2.8 AppIication of smoke fIavourings
Smoke flavourings can be blended directly into the food, for instance in minced
meat products, or they can be sprayed on to the surface of the products.
By using smoke flavourings one can prevent the drying loss which normally
takes place during the smoking process and the production time can be reduced. The
traditional smoking process is normally combined with drying whereby the weight of the
product is reduced. By using smoke flavourings, the food product does not lose weight
and this affects the quality and the price of the product. Ìn industrialised countries a
reduction of processing time is regarded as an advantage as it can often reduce the
price of the product sold to the consumer or give better profits to the producer.
The flavour from smoke flavourings is more or less the same as the flavour given
by traditional smoking, but the food product does not always acquire the same special
texture or colour as the traditional smoked food. Smoke flavourings are therefore often
used in combination with a traditional smoking process.
The advantage of the combination is, generally speaking, to get the right colour
from the smoke and the right taste from the smoke flavouring.
2.9 The technoIogicaI importance of smoke
Ìn general the smoking process is a surface treatment and it only affects a layer
of a few millimetres inside the product.
To summarise, the smoking process results in typical flavours, colour and
texture, and to some extent, a preservative and antioxidizing effect, together with
surface hardening.
These effects can be obtained both by traditional smoking and by the use of
smoke flavourings, but not always to the same degree. The choice between the use of
traditional smoking and smoke flavourings therefore also depends on which results are
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wanted from the smoking. Ìs it only a matter of flavour or a combination of all the
effects which can be obtained by the use of the process?
The colour of the products will not be affected if the smoke flavouring is added
and preservation of the products can only be obtained to a limited extent by adding
smoke flavourings on the surface.
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III - ChemicaI composition of smoked food
3.1 ChemicaI aspects of smoked food
The composition of smoke is very complex, more than 400 volatile substances
having been identified in wood smoke. The chemical composition depends among
other things on the temperature of the smoke generation, the kind of wood used, the
method used for developing the smoke, the water content in the wood, and addition of
air and water.
From a technological or health point of view the most important chemical
substances in the smoke are substances from the following groups:
a. nitrogen oxides
b. polycyclic aromatic hydrocarbons (PAHs)
c. phenolic compounds
d. furans
e. carbonylic compounds
f. aliphatic carboxylic acids
g. tar compounds
For some of these compounds, mainly those which are not very reactive and
which have a high boiling point like polycyclic aromatic hydrocarbons and phenolic
compounds, a good correlation is found between the content in the smoke and in the
smoked food.
Some of the volatile and more reactive compounds will very seldom be found in
the food. The nitrogen oxides can react with myoglobin to give colour to the food
product or these gases may react with amines or amides from the food to form N-
nitrosocompounds or with phenols to give nitro or C-nitroso phenols.
The carbonylic compounds and the acids react with proteins and carbohydrates
in the food.
The components from group a) and b) are normally only found in small amounts
in the smoke but because of the potential health risk of the nitrosamines and polycyclic
aromatic hydrocarbons, much attention has been drawn to them. These components
will therefore be dealt with in more detail below.
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3.2 Nitrogen oxides
Smoked food products may contain N-nitroso compounds. The most common of
these components is the volatile N-nitrosodimethylamine, but other substances from
this group may occur. The nitrosamines are formed due to reaction between nitrogen
oxides from the smoke and amines or amides in the food products. Because of this the
highest amounts of nitrosamines are found in food products with higher concentrations
of amines such as fish and meat products.
Ìn samples of smoked fish analysed in Denmark levels of N-
nitrosodimethylamine of up to 10 microgram/kg have been found. Ìn samples from other
countries similar concentrations have been measured.
Ìn smoked meat products occurrence of nitrosamines has been demonstrated
occasionally in smaller amounts of about 1 microgram/kg or less. One exception is
bacon, where higher amounts have been found in fried products: N-nitrosopyrrolidine
has been found in nearly all samples. The nitrosamine content in these products is
primarily due to the added nitrite and the high frying temperature, but it is possible that
phenols in the smoke may act as catalysts for nitrosamine formation. Ìn some cases a
higher content of nitrosamines is found, and direct smoking especially may give quite a
high content of non-volatile nitrosamines like N-nitrosothiazolidine and N-
nitrosothiazolidine carboxylic acid.
The chemical composition of smoked food produced by the use of smoke
flavourings is more or less the same as mentioned above, but as the smoke flavourings
are produced in a way which reduces some components such as PAHs, the amount of
the different components in "smoked" food by using smoke flavouring may be
somewhat different. The content of nitrosamines will probably be lower due to the
changed nitrosating conditions.
However it will be qualitatively almost the same components which are present
due to smoking.
3.3 Smoke fIavourings and chemicaI aspects
Many of the smoke flavourings are produced only by using the water-soluble
fraction of the smoke. As a marker for PAHs the benzo(a)pyrene content of the product
is analysed, and a maximum limit of 1 microgram/kg of condensate is obtainable.
Ìn order to limit the benzo(a)pyrene content, condensates may be produced with
a content of total organic substances below some 25%, so that during production it is
possible to remove or reduce unwanted components from the smoke. These
components might be unwanted because of health aspects or because of organoleptic
properties.
Much of the tar formed during pyrolysis in these products can be removed in
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several ways. A typical commercial smoke condensate will contain about 70% of water,
29% of volatile organic compounds, and 1% of tar. Ìt is difficult to improve on this as if
this 1% of tar is removed, more tar will be formed by polymerisation during the storage
of the smoke condensate until the ratio of volatile organic compounds to tar is again
about 29 to 1.
Smoke flavouring preparations usually contain carriers such as salt or dextrose.
The synthetic smoke flavourings are blends of well-defined chemical substances,
blended for the purpose of creating a special flavour. The components used in these
smoke flavourings are specific substances added in exact amounts, and each of them
should be evaluated from a health point of view.
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IV - HeaIth aspects of smoked food and smoke fIavours
4.1 GeneraI
The first observations on cancer from smoke or condensed smoke were made in
1775 by an English scientist Dr. Pott, who described the appearance of skin cancer
seen in a group of chimney sweeps. Most attention has been paid to the PAH-
components (the polycyclic aromatic hydrocarbons) with respect to skin cancer. Other
components in the smoke of concern to health are the nitrogen oxides which may give
rise to nitroso compounds in smoked food.
4.2 PAH-components
The PAH-component benzo(a)pyrene and approximately 10 other components
from this group have proved to be both mutagenic and carcinogenic in experimental
studies. The components have been applied either by injection or on the skin of test
animals in the carcinogenicity studies. Five of the components have also been shown to
be carcinogenic in animals after ingestion. Depending on which way the substances
have been administered to the test animals, they can cause cancer of the skin, lung,
mammalian tissue, stomach, intestine, liver or lymph. The carcinogenic effects of these
components have been seen after doses of only a milligram per kg bodyweight per day.
PAHs may be formed when burning organic material and are widespread in the
environment. Vegetables, and especially cereals and vegetable oils can be polluted
from the air, from the earth or from drying processes. Food made from animals is
practically free of PAHs, if it is not polluted during preparation eg. by being smoked or
overcooked (charred). Even though meat or fish products are smoked they do not
automatically contain enough PAHs to give rise to health concern.This is shown in
analytical studies made in several countries, in particular in Sweden and the United
Kingdom.
However, high amounts can be found especially on the surface of smoked
products,and mainly on products smoked for a long time with direct smoking at higher
temperatures.
Ìn many countries the smoking process is nowadays performed for a relatively
short period of time and besides this, many products are washed after being smoked
eg. frankfurter sausages. This procedure minimises the content of smoke particles,
which may contain substances of health concern.
"Total diet studies" from the United Kingdom and other countries show that the
largest amounts of carcinogenic PAH-components in the food do not come from
smoked meat and fish products, but from polluted cereals, fats and oils.
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Ìn Sweden the average intake of PAH-components of concern to health is
calculated to be 1,2 mg per year. Smoked meat and fish only contribute to 10 % of this,
the rest coming from pollution of the environment and smoking of tobacco. Generally
speaking, the intake of PAH from food is therefore regarded as of minor importance,
however on some occasions smoked food can have an unacceptably high content of
PAH mainly due to the smoking process used and can accordingly be of health
concern.
Home smoked food may have higher amounts of PAH, as the smoking process
mainly used in home smoking is direct smoking in small chambers with virtually no
possibility of controlling the process.
4.3 Nitrogen oxides and nitrosamines
As the smoke contains nitrogen oxides, formation of nitrosamines may take
place in the smoked meat and fish products. Nitrosamines are among the most
carcinogenic substances which have been studied in animals.
Ìn some countries there seems to be a correlation between the intake of heavily
smoked food ( and/or salted food) and a higher frequency of cancer of the stomach.
4.4 PhenoIs
Several phenolic compounds are found in smoke. These phenols are important
for the taste of smoked food. Ìn cured meat where addition of nitrite is often used, the
phenols may react with the nitrite to form nitro- and nitrosophenols. Some of these have
been shown to be mutagenic. The nitrogen containing phenols may be found in smoked
meat products, but whether the amounts there are of any health concern is unknown.
Furthermore some of the phenols may catalyse the formation of nitrosamines during the
smoking of food.
4.5 Other components
Many of the other components in smoked food are known to be toxic. This is the
case for some of the carbonylic compounds, for instance formaldehyde, which is
carcinogenic in test animals.
These compounds are not generally considered to be a health problem in
smoked food as they react with other compounds in the food to form products which are
not considered as dangerous to health.
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4.6 HeaIth aspects of smoked food produced by use of smoke fIavourings
The health aspects of the use of smoke flavourings, whether they are used as
smoke condensates or mixtures of chemically-defined flavouring substances, are
generally considered to be of less concern than the traditional smoking process.
Smoke condensates
The condensed smoke flavourings are rarely used without processing in order to
remove some of the components of special health concern.
The health aspects of smoke flavourings produced by condensation are in
principle more or less the same as those for traditional smoking. However, the use of
condensates produced in such a way that there is a possibility of removing some of the
components most dangerous to health, gives rise to less concern than the traditional
smoking process. For example, nitrogen oxides are not present in smoke condensates.
Ìt should be stressed, however, that the tar compounds are not well characterised and
are therefore difficult to evaluate from a health point of view.
By setting limits for some of the undesirable components health problems due to
smoked food produced by use of smoke condensates have been reduced. For
example, the European Community Directive 88/388/EEC sets a limit for
benzo(a)pyrene in flavourings which must be implemented into the regulations of the 12
Member States of the Community, and some other countries such as Sweden have
also set limits.
Smoke fIavourings produced by mixing chemicaIIy-defined components
Smoke flavourings may be produced by mixing well-defined flavouring
substances. They should be produced by using components which are toxicologically
acceptable such as the flavouring substances listed in the Council of Europe "Blue
Book".
These smoke flavourings are then of minor health concern.
4.7 ConcIusions
Ìt must be concluded that smoked foods do give rise to some health concern,
especially with respect to the possible content of nitrosamines and polycyclic aromatic
hydrocarbons (PAHs). Fortunately, however, there are several means available to
minimise some of the health concern by removing or reducing the amounts of relevant
components, by using smoke flavourings with a well known and " safe" composition or
by modifying the smoking process. The content of nitrosamines and/or PAHs may be
reduced by using a proper source material, temperatures below 400 °C for smoke
generation, indirect smoking, no open fire, a reduced smoking time and by optimising
the moisture and air supply.
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V - CounciI of Europe guideIines concerning the transmission of fIavour of
smoke to food
Introduction
Smoking of food has traditionally been used for about ten thousand years to
inhibit spoilage and to enhance the keeping qualities of food. Besides colouring and
preserving effects, the primary purpose today is to impart a smoke flavour to the final
product.
Smoke flavour can be added to food by using a traditional smoking process, by
use of smoke condensates, smoke preparations based on smoke condensates, or
flavour blends of chemically-defined substances.
Smoke flavourings are either smoke condensates, smoke preparations or flavour
blends.
The smoke condensates are obtained by condensing smoke and they may be
further fractionated, purified or concentrated. The fractionation steps have two
purposes: to obtain products of interesting olfactory properties and to reduce the
concentration of undesirable by-products of the smoke. The smoke condensates are
not generally used as such for the flavouring of food but are used as the basis for
smoke flavouring preparations.
The smoke fIavouring preparations are based on smoke condensates with the
addition of other substances and can be used either to regenerate smoke or used
directly in or on foods.
Smoke fIavour bIends are produced by mixing chemically-defined substances
in known amounts.
Smoking by conventional methods usually results in the contamination of the
smoked food with small amounts of toxic substances such as polycyclic aromatic
hydrocarbons. Substances present in smoke may react with components of the food to
produce toxic substances, for example, nitrogen oxides which may react with amines to
form nitrosamines. The Council of Europe Resolution AP (85) 2 adopted on 17 January
1985 considered that the potential hazard resulting from the presence of these toxic
substances should be reduced as much as possible.
Ìt is agreed that decisions on methods of analysis are essential when setting up
limits on impurities, but the guidelines do not give reference to methods of analysis as
the safety problems have been given highest priority.
Ìt is further recommended that smoke flavourings be preferably used on the
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surface of whole, cured meat products and that smoke flavourings should not be
premixed with curing salt or other nitrite blends.
The following Council of Europe guidelines are intended for manufacturers and
regulatory authorities and outline the minimum requirements to ensure the safety of the
preparations.
As only a few smoke flavourings have been studied toxicologically and as they
are not well characterised in terms of chemical composition, especially with respect to
the non-volatile part, adequate toxicological studies should be carried out with a well-
defined spectrum of these flavourings. This is in accordance with the Joint FAO/WHO
Expert Committee on Food Additives recommendation of 1987 (WHO technical report
series 759, 1987).
GuideIines concerning the transmission of fIavour of smoke to food
The flavour of smoke may be transmitted to food by:
1. smoking with freshly generated smoke;
2. smoking with smoke regenerated from smoke condensates;
3. flavouring with smoke flavouring preparations derived from smoke
condensates;
4. flavouring with smoke flavourings prepared by mixing defined substances.
1. Smoking with freshIy generated smoke
1.1 Generation of smoke should be based only on the combustion of specified,
acceptable types of natural wood (see appendix 1), to the exclusion of wood treated by
paint or impregnated with tar or other chemicals such as pesticides (for example
arsenicals or chlorinated phenols).
Herbs and spices may also be added, as well as twigs of Juniper and twigs,
needles and cones of Picea.
1.2 The smoking has traditionally been conducted in the following ways:
a. smoking with cooled smoke for weeks or only for a few days,
b. warm smoking at medium temperature, 25-50°,
c. hot smoking lasting 0.2 - 0.3 hours at temperatures higher than 50°,
d. black smoking with a strong smoke, special types of wood and ingredients -
such as resin for instance.
Suitable conditions for the generation of smoke and for smoking procedures
should be:
- 23 -
a. smoke developed by a smoke generator (indirect smoking) should be
preferred to direct smoking (smoke developed in the smoking chamber);
b. the smoking time should be as short as possible;
c. a washing procedure after the smoking process should be used.
1.3 Ìn view of limiting possible contamination, the process which gives a minimum of
contaminants should always be preferred. As upper limits, smoked food should not
contain more than 5 g of volatile N-nitroso compounds per kg of food and 1 g of
benzo(a)pyrene per kg of food, with the exception for smoked fish of 5g
benzo(a)pyrene per kg.
2. Smoking with smoke regenerated from smoke condensates
2.1 Data should be supplied on:
- the method of production of the preparation from which the regenerated smoke
is produced, including the type of wood used (see appendix 1),
- the composition of the smoke condensate giving the main components as
precisely as possible, and especially the content (percentage) of phenols, carbonyl
compounds, acids and resins.
For major organic compounds, in particular smoke condensates and for those
organic compounds most commonly occurring in smoke condensates, both quantitative
and qualitative information should be provided. Batch variations and methods of
analysis should also be supplied.
2.2 The smoke condensates used to prepare the regenerated smoke should be
purified in order to minimise the content of undesirable substances.
As a maximum limit the contaminants in the condensate should not exceed:
benzo(a)pyrene max. 10 g/kg (giving rise to less than 0.03 g/kg in the
foodstuff as consumed)
benzo(a)anthracene max. 20 g/kg (giving rise to less than 0.06 g/kgin the
foodstuff as consumed)
As max. 3 mg/kg
Hg max. 1 mg/kg
Cd max. 1 mg/kg
Pb max. 10 mg/kg
2.3 Documentation for toxicological results
Ìn general for smoke condensates, the minimum toxicological data required for
smoke flavouring are as follows:
- 24 -
- a gene-mutagenicity test (eg. Ames test), a test for chromosome damage in
vivo (eg. micronucleus test) or in vitro and a 90 day feeding study in animals in
accordance with OECD or EEC guidelines.
2.4 Ìnformation should be provided on the kind of food for which the smoke
condensate is intended to be used.
3. FIavouring with smoke fIavouring preparations derived from smoke
condensates
The use of smoke flavouring preparations based on smoke condensate should
only be authorised on the basis of satisfactory information fulfilling the following criteria:
3.1 Data should be supplied on:
- the method of production of the preparation from which the smoke flavouring is
produced, including the type of wood used (see appendix 1);
- the composition of the smoke flavouring preparation giving the main
components as precisely as possible, and especially the content (percentage) of
phenols, carbonyl compounds, acids and resins;
For major organic compounds, in particular smoke flavouring preparation and for
those organic compounds most commonly occurring in smoke flavouring preparations,
both quantitative and qualitative information should be provided. Batch variations and
methods of analysis should also be supplied.
3.2 The smoke flavouring preparation should be purified in order to minimise the
amount of undesirable substances.
As a maximum limit the contaminants in the fIavouring preparation should not
exceed:
benzo(a)pyrene max. 10 g/kg (giving rise to less than 0.03 g/kg in the
foodstuff as consumed)
benzo(a)anthracene max. 20 g/kg (giving rise to less than 0.06 g/kg in the
foodstuff as consumed)
As max. 3 mg/kg
Hg max. 1 mg/kg
Cd max. 1 mg/kg
Pb max. 10 mg/kg
3.3 Documentation for toxicological results
- 25 -
Ìn general, for smoke flavouring preparations, the minimum toxicological data
required are as follows:
- a gene-mutagenicity test (eg. Ames test), a test for chromosome damage in
vivo (eg. micronucleus test) or in vitro and a 90 day feeding study in animals in
accordance with OECD or EEC guidelines.
3.4 Ìnformation on use levels and the kind of food in or on which the smoke
flavouring preparation is intended to be used should be provided.
4. FIavouring with smoke fIavours prepared by mixing chemicaIIy-defined
substances
The following information is required for the use of a smoke flavouring based on
chemically-defined substances:
4.1 Ìnformation on the composition of the smoke flavouring blend is required in all
cases.
4.2 Where the substances concerned have all been judged by the competent
Council of Europe body to be acceptable from the toxicological point of view and the
levels of the individual compounds to be used in the specified foods are within the limits
established by the Council of Europe : in "Flavouring substances and natural sources
of flavourings" (4th edition) no further information is required.
4.3 Where some of the chemically-defined substances have not been accepted by
the Council of Europe then each chemically defined substance could be tested
toxicologically as described in the 4th edition of the Council of Europe's publication
"Flavouring substances and natural sources of flavourings" (4th edition, Part Ì -
Chemically-defined flavouring substances).
4.4 As an alternative to 4.3, the tests mentioned below could be used for the
complete smoke flavouring blend.
Ìn general, the minimum toxicological data required for smoke flavours prepared
by mixing chemically-defined substances are as follows:
- a gene-mutagenicity test (e.g. the Ames test), a test for chromosome damage
in vivo (e.g. a micronucleus test) or in vitro, and a 90 day feeding study in
animals in accordance with OECD or EEC guidelines should be provided.
- 26 -
Appendix 1
Wood traditionaIIy used which is acceptabIe for production of smoke fIavourings
Acer negundo L. Maple tree Erable
Betula pendula Roth. (with ssp. B.
alba L. and B. verrucosa Ehrh.) White birch Bouleau
Betula pubescens Ehrh. European birch Bouleau
Carpinus betulus L. Hornbeam Charme
Carya ovata (Mill.) Koch (C. alba
(L.). Nutt.) Hickory Hickory
Castanea sativa Mill. Chestnut tree Châtaignier
Eucalyptus sp. Eucalyptus Eucalyptus
Fagus grandifolia Ehrh. Beech Hêtre
Fagus silvatica L. Beech Hêtre
Fraxinus excelsior L. Common ash Frêne commun
Juglans regia L. Walnut tree Noyer
Malus pumilia Mill. Apple Pommier
Prosopis juliflora DC. Mesquite wood Mesquito
Prunus avium L. Cherry tree Cerisier
Quercus alba L. White Oak Chêne blanc
Quercus robur L. Common red oak Chêne rouvre
(Q. penduculata Ehrh.)
Rhamnus frangula L. Alder Buckthorn Bourdaine
Robinia pseudoacacia Black locust Robinier
Ulmus fulva Michx Sweet elm Orme
Ulmus rubra Mühlenb. Elm Orme
Submissions for further inclusion may be made to the Council of Europe.
Wood treated by paint or impregnated with tar or other chemicals such as
pesticides (for example arsenicals or chlorinated phenols) is excluded.
Herbs and spices may also be added, as well as twigs of Juniper and twigs,
needles and cones of Pice.
- 27 -
VI. - BibIiography
Selected references:
1. Bøgh-Sørensen, L., Jensen, J.H. and Jul, M.
Preservation Technique 2 ( M Danish), DSR Forlag, København 1981.
2. Fabech,B. and Larsen, J.C.
Smoking of Food. A survey of Methods Used in Denmark (in Danish). Publication no.
135, 1986, 1-57.
3. Federation of American Societies for Experimental Biology (FASEB). Evaluation of
the Health Aspects of Smoke Flavouring Solutions and Smoked Yeast Flavouring as
Food Ìngredients. Prepared for Food and Drug Administration (FDA). National
Technical Ìnformation Service. U S Department of Commerce, Springfield, VA, 1981, 1-
47.
4. Lawley, P D
N-Nitroso Compounds.Ìn: Handbook of Experimental Pharmacology. Chemical
Carcinogenesis and Mutagenesis Ì, Cooper, C. S. and Grover, P. L.(Eds), Springer-
Verlag, Berlin etc, 1990, 410-469.
5. Maga, J A
Smoke in Food Processing, CRC Press, Ìnc., Boca Raton, Florida, 1988, 1-160.
6. Santodomato, J., Howard, P. and Basu, D. Health and Ecological Assessment of
Polynuclear Aromatic Hydrocarbons. J.Environ.Pathol.Toxicol.5, 1981, 1-364.
7. Schmidt, K.-F.
Schinkenrauchern - Das Neue Hobby.,Verlag Paul Parey, Hamburg, 1984.
- 28 -
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1. Propr|elary ard olrer prarraceul|ca|s c|ass|l|ed as rarcol|c suoslarces ard or sa|e |r 21 reroer 3lales ol lre Courc|| ol Europe. Arrua|
ed|l|or l33N 025ê-13Z8
2. lardooo| ol sea ard a|r porls |r lre excepled area. Arrua| ed|l|or l33N 0252-0ê80
3. Lurg carcer |r weslerr Europe. 3rd ed|l|or (19Z8) l38N 92-8Z1-0Z25-1
1. Europear Prarracopoe|a. 2rd ed|l|or (1980) Puo||srer: Va|sorreuve, 3.A. 8.P. 39, F-5Z1ê0 Vou||rs-|es-Velz
5. Adr|r|slral|ve arrargererls lor lre rea|lr corlro| ol sea, a|r ard |ard lrall|c, êlr ed|l|or (1981) l38N 92-8Z1-0Z21-8
ê. F|avour|rg suoslarces ard ralura| sources ol l|avour|rgs, 3rd ed|l|or (1981) Puo||srer: Va|sorreuve 3.A., 8.P.39, F-5Z1ê0 Vou||rs-|es-
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Z. Neorala| rass screer|rg lor relaoo||c d|sorders, 2rd ed|l|or (1981)
8. 3uoslarces used |r p|asl|cs raler|a|s cor|rg |rlo corlacl W|lr lood, 2rd ed|l|or (1982) l38N 92-8Z1-001ê-2
9. Cosrel|c producls ard lre|r |rgred|erls, 2rd ed|l|or (1981)
10. Res|dues ol veler|rary drugs |r lood ol ar|ra| or|g|r, 1sl ed|l|or (198ê) l38N 92-8Z1-090Z-9
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12. 0u|de||res lor lre eva|ual|or ol Wood prolecl|or producls, 1sl ed|l|or (|98Z) l38N 92-8Z1-10Z0-0
13. P|arl preparal|ors used as |rgred|erls ol cosrel|c producls, 1sl ed|l|or (1988) l38N 92-8Z1-1ê89-X
11. ¨Lex|cur prarraceul|cur¨ ol pr|rc|pa| prarraceul|ca| lerrs |r s|x |arguages (0errar, Erg||sr, Frercr, lla||ar, 3par|sr ard 0ulcr) 3rd
ed|l|or (1990) l38N 92-8Z1-1899-X
15. ¨Pesl|c|des¨, Zlr ed|l|or (1992) l38N 92-8Z1-1958-9
1ê. lea|lr aspecls ol us|rg sro|e l|avours as lood |rgred|erls (1992) l38N 92-8Z1-2189-3
1Z. Courc|| ol Europe 0u|de||res corcerr|rg lre lrarsr|ss|or ol sro|e lo lood (1992) l38N 92-8Z1-2191-5
0r|g|ra||y used lor preserv|rg lood, lre sro||rg process |s loday rosl|y used lo oola|r lre craracler|sl|c lasle ard appeararce ol sro|ed lood.
Tr|s ooo|, produced oy lre Courc|| ol Europe Corr|llee ol Experls or F|avour|rg 3uoslarces, a|rs lo |rlorr lre corsurer or lre sro||rg
process ard rea|lr aspecls ol us|rg sro|e l|avour|rgs as lood |rgred|erls.
Tre reader W||| a|so l|rd gu|darce or Ways lo r|r|r|se lre poss|o|e lorral|or ol suoslarces ol darger lo rea|lr.
Courc|| ol Europe Press
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