The HEATOX project - World Food Science

HEATOX PROJECT
The HEATOX project
Kerstin Skog discusses the formation of potentially
hazardous compounds in foods during heating, with an
emphasis on acrylamide
Background
Heating food gives many advantages:
it adds taste, colour and texture and
minimises harmful bacteria. However,
modern science has shown that
heating foods also can generate
potentially hazardous compounds.
This became obvious when Swedish
researchers in April 2002 reported the
finding of high levels of acrylamide in
some heated foods. Acrylamide is
classified as a probable human
carcinogen by the International
Agency for Research on Cancer and
therefore it is important to minimise
its presence in our diet.
The HEATOX project
The focus of the EC-supported
HEATOX project is on the health risks
associated with acrylamide and similar
toxic substances in heat-treated,
carbohydrate-rich foods. The levels of
acrylamide in potato crisps can be very
high, up to 2000 µg/kg, while it is
lower in bread.
The HEATOX project brings
together scientists from different
disciplines (and countries) to work
together on questions related to
acrylamide and other heat-induced
toxicants. We are also happy to have
the European Consumer Organisation
(BEUC) as one of our partners, since
there is much concern about health
issues among the general public. The
project started late 2003 and has a
duration of 40 months.
The project (Fig.1) explores the
mechanisms of formation, the impact
of raw material composition, cooking
and processing methods in
households, restaurants and industry,
with the aim to control and minimise
the formation of acrylamide. Exposure
assessment and data on hazard
characterisation will be combined in a
risk assessment of the intake of heattreated,
carbohydrate-rich foods.
Expected results are recommendations
to consumers, restaurants and the
food industry on how to minimise the
amounts of heat-generated toxicants
in foods, while ensuring product
quality from a nutritional and sensory
point of view.
Household
cooking
Formation
Industrial
Processing
External
exposure
Formation and processing
The Maillard reaction between
sugars and amino acids adds taste,
flavour and colour to heated foods but
may also generate small amounts of
PROJECT OUTLINE
toxic compounds, such as acrylamide.
This compound can be formed from
the amino acid asparagine and
reducing sugars, for example, glucose
or fructose. These precursors are
naturally occurring in raw potato,
cereals and coffee beans. It is a
challenge to find new processing
techniques in order to achieve safe
and consumer attractive end products.
As consumers, we like Maillard
reactions!
The HEATOX project deals mainly
with potato products, bread and
coffee, and one of the aims of the
project is to increase our knowledge of
the mechanisms and reaction
conditions under which acrylamide is
formed or degraded. This is necessary
for the development of new or
improved processing technologies that
Internal
exposure
DNA
damage
Non-genetic
damage
Mutation
cancer
Fertility
Neurological
effects
Research themes
• Formation • Exposure assessment • Analysis • Hazard characterisation
• Risk assessment Management, Communication, Dissemination and Training
The HEATOX project deals with questions regarding heat-generated
food toxicants, such as:-
• In which foods are these compounds mainly found?
• How are they formed?
• Do they constitute a health risk?
• How can we measure/control the amounts produced?
• How much is consumed?
• What are the effects on the human body?
• How can they be avoided?
• Is there a cooking method to be recommended?
Figure 1. Overview of the HEATOX project.
will reduce acrylamide formation.
The key strategy is to understand the
chemical mechanisms and reaction
pathways for acrylamide formation,
and to elucidate what factors in terms
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HEATOX PROJECT
of reaction conditions and chemical
composition influence these reactions.
A database containing 570
compounds that can be formed in
simple amino acid-sugar reaction
systems has been compiled. This
information can be used by
toxicologists for defining heat-derived
compounds that may be considered as
potentially harmful.
The kinetics behind the formation
and loss of acrylamide during heating
of low moisture model systems, e.g.
potato cakes, has been studied. It was
found that long heating times resulted
in a tremendous loss in acrylamide.
Higher temperature for coffee
roasting yielded lower levels of
acrylamide, and interestingly, high
concentrations of sugars in coffee
beans correlated with lower
concentrations of acrylamide after
roasting.
The limiting factor for formation of
acrylamide in bread is asparagine,
which is mainly concentrated in the
cereal bran. This means that bread
made from flour rich in dietary fibre
will contain more acrylamide than
bread from sifted flour. However, new
fermentation techniques could
degrade the asparagine and thus
lower the acrylamide content. New
baking techniques such as air jet
impingement and infrared radiation
baking seem promising and the effect
on sensory quality, bread crust and
acrylamide formation is under
investigation.
A mind map was created to get an
overview of factors affecting
acrylamide formation during potato
processing. Then a fry simulator, i.e. a
computer program, was developed
based on oil temperature, sugar and
asparagine concentrations. The fry
simulator can be applied to new and
improved processing technologies to
evaluate acrylamide formation and
quality of the product. So far, the most
crucial parts seem to be the corners of
French fries.
The effect of storage conditions on
sugar development and acrylamide
formation has been studied for
different potato varieties. It was found
that low storage temperatures
increased the sugar content as well as
the acrylamide content. However,
potato varieties adapted to cold
storage had lower sugar content and
for some varieties, the level of
asparagine seemed to be important for
acrylamide formation. Work has also
been undertaken on home-cooked
potatoes, for example, the effect of
frying in a commercially-available
domestic fryer on acrylamide
formation. When the potato sticks
were put in the fryer, the oil
temperature dropped drastically and
slowly reached its original
temperature. At that time, high levels
of acrylamide were found. The drop
in temperature depends of the
product/oil ratio and this makes it
difficult to define an initial oil
temperature as a measure to reduce
acrylamide.
Analysis
Adequate analysis is a prerequisite
for reliable results. A variety of
analytical techniques for different
heat-induced toxic compounds in
foods and precursors, along with
analytical techniques for adducts and
metabolites in humans and animals,
have been developed. Special focus
has been on high-intake foods like
bread and infant food for which low
determination limits are needed for
intake estimates, and also difficult
matrices which are estimated to
account for up to 30% of the
acrylamide exposure in some
countries.
Different analytical methods for
acrylamide, furan and HMF (5-
hydroxy-methylfurfural) in different
types of foods have been investigated.
Regarding acrylamide analysis, an
improved extraction procedure for
both clean-up and sample preconcentration
has been developed,
and comparison between several
analysers for LC-MS/MS methods has
been performed. The influence of
high pH on the release of acrylamide
during water extraction of food
samples has been studied. Several of
the partners in the project have access
to sophisticated analytical equipment
and techniques, such as HR-GC-TOF-
MS (High Resolution Gas
Chromatography Time-of-Flight Mass
Spectrometry), LC-MS/MS, NMR,
AMS (Accelerator mass spectrometry)
and a flow cytometer-based
micronucleus assay for human
erythrocytes.
Cooking practices and dietary habits
vary between countries and food
samples have been analysed in
connection with exposure assessment,
for example, foods for which literature
data is insufficient. This includes
ethnic foods, foods for specific risk
groups (e.g. children), home-cooked
foods and foods where reliable data
are missing due to limitations of the
analytical methods. To get refined
dietary exposure estimates, samples of
ready-to-eat meals prepared from
frozen and similar pre-prepared
products have also been examined.
Thus, data on acrylamide levels for
exposure estimates have been
obtained from different countries
within the project.
A literature search for known
cooked-food toxicants and other
potential hazardous substances that
could be formed in thermal processing
of foods has been performed, and a
preliminary QSAR (quantitative
structure-activity relationship)
assessment of a large number of
browning reaction products has been
conducted.
Hazard characterisation
Knowledge of the dose-effect
function, including the bioavailability
of heat-induced toxicants in food, is
important. Bioavailability is measured
with different biomarkers, i.e.
different adducts. A number of
different studies have been
performed, not only on acrylamide
but also on HMF and other heatinduced
compounds and a few of
them are commented upon below.
Progress has been made in the use
of AMS in the determination of
acrylamide, acrylamide metabolites
and DNA-adducts at the very low
concentrations corresponding to
human exposure levels, and a good
dose response relationship was
obtained for DNA adducts.
The potency of different heatinduced
toxicants has been studied in
the micronucleus assay in mice.
The results indicate that some heatinduced
toxicants show both stronger
and lower potency compared with
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HEATOX PROJECT
acrylamide. It raises the question of
how quantitative data on potency could
be used in risk assessment.
Animal experiments on neurodevelopmental
toxicity showed that the
developing brain is particularly
susceptible to acrylamide exposure,
which causes persistent changes in
behaviour in mice, a finding with
important impact on human hazard
assessment.
Exposure assessment
Monte Carlo Risk Analyses software is
a probabilistic model originally made
for exposure assessment of pesticide
residues. The model has been
extended and optimised to perform
‘what-if scenarios’ using acrylamide
concentration data. A few ‘what-if
scenarios’ have been performed to
study the effect of food processing on
acrylamide exposure levels.
Another model has been developed
and used to study the issue of brand
loyalty in the scenario-analysis of
acrylamide exposure assessment. These
first calculations with the brand loyalty
model showed that brand loyalty has
influence on the higher exposure levels
and that brands with high acrylamide
levels can increase exposure levels
depending on the market share.
Blood samples have been collected
from around 100 persons to study the
variation of acrylamide concentration
in the blood between persons and
within the same person over time.
Animal experiments, where rats were
exposed to acrylamide through
drinking water during one week, at
dose rates applied in published cancer
tests, have resulted in data for species
extrapolation (from animal cancer tests
with acrylamide).
Risk assessment
For risk assessment, the most crucial
issues to be addressed include the
translation of results from animal
experiments to humans and
extrapolation from high to low dose. A
Workshop on risk assessment was held
in June 2006 with researchers from
HEATOX together with invited
stakeholders from, for instance,
industry and the authorities. Issues
such as “How to make final risk
characterisation” were discussed.
Furthermore, it was concluded that
some of the important tasks for
HEATOX were to generate data not
only for acrylamide but also for other
heat-induced toxicants if possible. The
final risk assessment will be made at the
end of the project taking all data into
account. This will result in Guidelines
for consumers on healthy homecooking
and consumption of cooked
foods, and Strategies for food
industries, restaurants, etc., to minimise
acrylamide formation.
Management, communication,
dissemination and training
Since no food industry is a partner in
the project, a close contact between the
project and other international
activities has been successfully
established through an External
Consulting Panel with invited persons
from different user groups and
relevant stakeholders.
Communication is an issue for most
researchers and within the project
different types of practices have been
tested, such as ‘Open space technology’
and ‘Aquarium’. Aquarium denotes a
specially designed type of panel debate
where key persons (stakeholders) are
invited to a round-table discussion, and
with supporters of each stakeholder
sitting in a segment of the circle behind
“their person”. During the discussion,
the supporters can advise, question and
support their representative by oral or
written messages. The discussion is
moderated by a chairperson. This type
of panel debate was part of the
HEATOX Workshop held in June
2006, where persons from the project
discussed relevant issues together with
representatives from consumer
organisations, food and food
equipment industry, and authorities.
Most of the partners have one or
more PhD students or young
researchers working in the project.
Special emphasis has been put on
communication training; at the 18
months’ meeting, this group presented
posters on their HEATOX work based
on ideas from risk communication; at
the 24 months’ meeting, a seminar was
arranged on the topic of risk
communication and dissemination. In
addition, the exchange of young
scientists is encouraged and many have
visited other research centres for some
weeks to learn or implement new
methods.
Future perspectives
Health risks with acrylamide in foods
are still an open question. It is also
important to find out to what extent the
food industry has fulfilled their promises
to reduce the acrylamide content in
their products. The progress made
within the HEATOX project may help
consumers, chefs and the food industry
to produce healthy and nutritious foods.
Acknowledgement
This work has been carried out with
support from the European
Commission, Priority 5 on Food
Quality and Safety (Contract No:
FOOD-CT-2003-506820 Specific
Targeted Research Project),
This paper reflects the author’s views
and not necessarily those of the EC.
Further reading
1. Dybing E. et al., (2005). Human
exposure and internal dose
assessments of acrylamide in food.
Food Chem. Toxicol., 43 (3) 365-410.
2. Gerrard, J. A. (2006). The Maillard
reaction in food: progress made,
challenges ahead. Trends Food Sci.
Tech., 17 (6), 324-330.
3. Jackson, L. S. and Al-Taher, F.
(2005). Effects of consumer food
preparation on acrylamide
formation. Chemistry and Safety of
Acrylamide in Food, 561, 447-465.
4. Skog, K. and Alexander, J. (eds)
(2006). Acrylamide and other Hazardous
Compounds in Heat-treated Foods.
Woodhead Publishing Ltd.
5. www.ciaa.be/documents/positions/
The%20CIAA%20Acrylamide%20Toolb
ox.pdf
(A comprehensive listing of references
on acrylamide can be found on the
HEATOX website, www.heatox.org.)
Professor Kerstin Skog is the Co-ordinator
of the HEATOX project and is at the
Department of Food Technology,
Engineering and Nutrition, Lund
University, Sweden
Tel: + 46 46 222 8319
Email: heatox@inl.lth.se
Web: www.heatox.org.
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