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• Detection of Genetically Modified Organisms
  (GMOs)
• Nachweis von transgenen Organismen
• Approaches to evaluating the transgenic status
  of transformed plants.
• TIBTECH 15, 141-146 (1997).
• Detection of genetically modified organisms in
  foods. TIBTECH 20, 215-
• 223 (2002).

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• in the recent years new plant varieties have
  been
• developed
• USA ?40 of corn, ?50 of cotton, ?45 of
  soybean
• ? genetically modified (1999)
• about 60 of food products in US supermarkets
• contained GMOs (1999)

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• Acceptance of GMOs
• USA generally less resistance to introduction
• of genetically modified (GM) food
• Europe more mistrust, environmental and
• public health safety
• ? potential gene flow to other organisms
• ? agricultural diversity ?
• ? allerginicity, antibiotic resistance and
• gastrointestinal problems

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• restrict the import of bio-engineered foods
• introduce strict laws concerning labeling of GM
  foods
• and food ingredients (additives, flavorings)
• ? EU regulations mandate labeling of food
  containing
• GMOs
• ? established a 1 treshold for contamination of
• unmodified foods with GM food products

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Absolutely important that government, food
industry, testing laboratories and crop producers
develop ways to exactly quantitate GMOs in crops,
foods and food ingredients to assure compliance
with treshold levels of GM products.
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Testing Methods Protein-based
DNA-based Western Blot
Southern Blot ELISA
PCR /
qualitative Lateral Flow Strip
PCR / quantitative
NIR
spectroscopy
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• Western Blot
• qualitative results
• denaturating conditions ? problems of
• solubilization, aggregation, coprecipitation
  eliminated
• research application than for routine testing
• detection limit 0.25 - 1

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• ELISA
• qualitative and quantitative results
• but no quantitative internal standard ?
• no information concerning presence of GMOs at
  ingredient
• level in food
• less sensitive than PCR
• detection limit 0.25 - 1

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• Southern Blot
• no quantitative results
• difficult method
• moderate sensitivity
• research

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• PCR / qualitative
• highly sensitive
• detection limit 0.0001 - 1
• but
• heat, nuclease activity, low pH ? DNA
  degradation
• compounds present in foods ? PCR inhibitors
• false positive results

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• Quantitative real-time PCR
• concentration of DNA is proportional to PCR
  cycle number
• during exponential phase ?? conventional PCR
  end-point
• analysis of amplified product
• highly sensitive
• low copy DNA number
• reference house-keeping gene ? allows
  quantitation in the
• assay

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• NIR spectroscopy
• non-destructive analysis of whole grains for the
  prediction
• of moisture, protein, oil, fiber and starch
• fast (? 1 min), no sample preparation, cheap
• but
• not identify compounds
• not detect change in DNA or single protein, but
  much
• larger unknown structural changes, that are
  introduced by
• the presence of new DNA

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