From the Special Topic of
Mycotoxins are natural metabolites produced by fungi
infecting cereals, either as crops in the field or found in
grain in storage. More than 300 mycotoxins have already
been chemically characterized, but the total number of
secondary fungal metabolites is estimated to be more than
20,000. National and international bodies such as the US
Food and Drug Administration, the European Commission, and
the World Health Organization have recognized the health
risks to animals and humans caused by mycotoxins entering
the food chain.
These institutions have compiled comprehensive directives to regulate
the permitted levels of mycotoxins in food and animal feed. Appropriate
drafting of regulations for trace contaminants is critically dependent on
tools from analytical chemistry because the screening of food and feed
needs to be fast, cost-effective, and accurate.
A Special Topics examination of mycotoxins research over the past
decade ranks the research of Professor Rudolf Krska at #2 by total number
of papers, and at #4 by total citations. His record in this analysis
includes 48 papers cited a total of 546 times. Three of these papers have
been named as Highly Cited Papers in
Essential Science IndicatorsSM from
Professor Krska is
head of the Center for Analytical Chemistry at the
University of Natural Resources and Applied Life Sciences,
Vienna, Austria. In the interview below, Dr. Simon
European correspondent, talks with Professor Krska to
find out more about his high-ranking papers published in
the past 10 years.
Globalization means that the food industry
has to take biosecurity extremely seriously, so that's why UN agencies
such as WHO have a hand in making regulations for toxins in our food.
The Special Topics analysis by Clarivate shows that you have been
making state-of-the-art contributions to the development of tools that
can detect mycotoxins in cereal-based food. How did you become an
analytical chemist specializing in these contaminants?
I graduated from the High School here in Vienna. From there I attended the
Vienna University of Technology, where I received my diploma in chemistry.
That's where my interest in agricultural and environmental pollutants
started, because my thesis topic was on the decontamination of soils
polluted by cyanides.
persistent: they are usually not broken
down in digestion, nor does cooking
The next step for me was a Ph.D., and for that the thesis concerned the
development of a new infrared fiber-optic sensor for chlorinated
hydrocarbons in water.
So your interest in toxicology moved in the
direction of improving the analytical techniques for the detection of
Very much so. My interest in mycotoxins in particular started when I was a
postdoc working in Ottawa with Health Canada. My mentor there was Peter M.
Scott, a world expert in the field, and we have remained firm colleagues
ever since I returned to Vienna.
Why should we be concerned about
They are potent toxins with a wide range of actions on humans and animals.
An extensive literature describes neurotoxic, carcinogenic, mutagenic,
immunosuppressive, and estrogenic effects of mycotoxins. Although the
greatest risk to humans comes from the direct contamination of food, the
entry of mycotoxins into the food chain via eggs, milk, and meat should not
be overlooked. However, health issues as a result of mycotoxin
contamination of human food are restricted to developing countries.
Nonetheless, in industrial countries mycotoxin contamination is an
important agricultural problem and thus related to feed stuffs. Mycotoxins
are persistent: they are usually not broken down in digestion, nor does
cooking destroy them.
There are hundreds of them, and from the point of view of organic chemistry
they exhibit great structural diversity that leads to different chemical
properties, and that variety is of course a challenge in terms of detection
Aflatoxins, which are produced by the Aspergillus species, can be
deadly. In 2004 more than 100 people died in Kenya after eating home-grown
maize that was contaminated.
The toxins in which I specialize are produced by several species of the
genus Fusarium. They include trichothecene mycotoxins such as
deoxynivalenol and zearalenone. They are also very stable and can survive
cooking. The trichothecenes are not acutely toxic but they can weaken the
immune system and can cause vomiting and diarrhea.
What are the main research areas at your Center of
The Center comprises about 35 professionals in chemistry. We cover three
toxicological potential of the many
mycotoxins can obviously be quite
different depending on the fungal
species from which they have been
One is mycotoxin research in general, not just the chemical analytical
techniques for detecting these substances in different commodities. We also
study microbial reaction processes of these mycotoxins by microbes, as a
means to degrade the toxins in vivo. Our research has continuously
shifted towards metabolomics, an area where we study the interactions
between plants and fungi, and the resulting range of bioactive metabolites.
Metabolic profiling is also an important tool in toxicology. We have now
shifted the emphasis from target analysis to understanding the whole range
of possible metabolites that are formed in plants.
Our second area is water analysis, where we are organizing proficiency
Our third area is the development of rapid test methods. This covers
immunochemical assays, and lateral flow devices, both for rapid on-site
detection of mycotoxins as well as for allergenic proteins in food.
Your papers show that you've made important
progress in speeding up analysis, particularly by increasing the
number of identifications that can be made via a single
You bet! In 2006 my group scooped a $50,000 prize for the development of a
fast and reliable method of mycotoxin detection. We won that award for the
development of fully C13-labeled mycotoxins and the quick detection of 12
different mycotoxins, but we have since developed our technique so that it
can handle as many as 87 toxins at a time. Our analysis has shifted from
single identifications to broad spectrum analysis.
We have been among the first to develop multitoxin methods by mass
spectrometry, particularly for masked mycotoxins, and that's the topic of
the 2005 Journal of Agriculture and Food Chemistry paper, "Masked
mycotoxins: Determination of a deoxynivalenol glucoside in artificially and
naturally contaminated wheat by liquid chromatography-tandem mass
spectrometry," (Berthiller F, et al., 53:3421-5). These masked
mycotoxins were first detected by us. They escape routine analysis but can
cause intoxication once the free toxin is released again during digestion.
Our breakthrough increased the awareness of toxins that are not apparently
there but are still a potential threat to human and animal health.
Several of your highly cited papers are on
trichothecenes. I note that these are papers on applications, with the
emphasis on detection.
The toxicological potential of the many mycotoxins can obviously be quite
different depending on the fungal species from which they have been
produced. The most toxic are the aflatoxins, and that has been known since
the 1960s. However, my specialty has always been a focus on the
Fusarium mycotoxins which are most prevalent in the moderate
climatic regions of the world.
These Fusarium mycotoxins do show much less toxicity compared to
aflatoxins. The most prevalent mycotoxins, and the subject of my most-cited
papers, are the trichothecenes, which do not show acute toxicity. However,
they can occur at quite high levels sufficient to cause vomiting and
weakening the immune system—that's a major issue here. But I must
point out that these mycotoxins are also more important for animal feed
rather than for food. It is mainly an agricultural problem in the first
instance and only secondarily about food.
Are the regulatory authorities the main drivers of
the impact of your practical papers on analysis?
Yes, that's particularly the case for the most prevalent Fusarium
mycotoxins. There is new legislation which came into force in 2006, and
that certainly has increased the awareness of these toxins. For example,
the European regulation on deoxynivalenol in bread includes a maximum
accepted level of 500 ng g-1, 500 parts per billion. Also in the
couple of years before 2006, people were already aware that new regulations
were coming into play, and that's one of the reasons why interest in the
analysis of these compounds increased.
My most-cited paper from this analysis, "The state-of-the-art in the
analysis of type-A and -B trichothecene mycotoxins in cereals," (Krska R,
et al., Fresen. J. Anal. Chem. 371: 285-99, 2001), probably drew
attention due to the expected EU-regulations. In addition, the
state-of-the-art of detection for trichothecenes has gradually changed from
gas chromatographic methods to liquid-chromatography coupled to mass
Professor Rudolph Krska, Ph.D.
Department for Agrobiotechnology (IFA-Tulln)
University of Natural Resources and Applied Life Sciences, Vienna
Keywords: mycotoxins, cereals, food chain, animal feed,
trichothecenes, chemical analysis, microbial reaction processes,
metabolomics, water analysis, rapid test methods, regulation.