toxin detection techniques

-Physicochemical Methods
In this method, the mycotoxin is extracted, purified, concentrated and separated via thin-layer chromatography before the mycotoxin in the food sample can be quantified.

-Immuno Assays
Mycotoxins are made to interact with specific antibodies before they are isolated. Radioimmunoassay (RIA) and enzyme-linked immunoabsorbent assay (ELISA) are two techniques of this method.

-Biological Assays
Biological systems such as cell and tissue cultures, animals and microorganisms are used as bioassays to detect and quantify mycotoxins. Furthermore, it can display the physiological and pathological effects of mycotoxins.

Adapted from: Food and Beverage Mycology, 2nd Edition, Larry R. Beuchat, 1987

Mycotoxins

The harmful chemicals produced by fungi in food are referred to as mycotoxins. Mycotoxins do not get eliminated during digestion or even temperature treatments during food processing. These harmful compounds can be carcinogenic, teratogenic, tremorgenic, hemorrhagic and dermatitic. They may also limit growth in affected consumers as protein synthesis is inhibited.

Adapted from: http://en.wikipedia.org/wiki/Mycotoxin and
Food and Beverage Mycology, 2nd Edition, Larry R. Beuchat, 1987

Isolation and Identification of Foodborne Pathogens

Conventionally, the sample food is mixed with a buffer and homogenized before it is placed into a non-selective media for the resuscitation of the microorganisms. Upon revival of the microorganisms, the food sample is incubated in a selective media for selection of specific microorganisms. Then it is placed in a growth media which promotes propagation of the microorganism. The microorganisms go through another selection phase via the use of differential and selective agars. After a specified incubation period, the colonies present on the agar will be isolated. These isolates then undergo biochemical testing for identification and characterization purposes. Cultural methods are labour intensive and time-consuming. Hence, rapid methods have been established to give accurate results, quicker.

Rapid methods include
-Immunological Methods (Antibody-based Assays)
-DNA/RNA Methodology (Nucleic Acid-based Assays)
-Next Generation Technologies
-rTPCR
-Immunosensors/ Biosensors
-DNA Microarrays

Adapted from: Food Microbiology, M.R. Adams & M.O. Moss, 1995

GM food in Singapore

Singapore’s position on GM food is on par with international practice. The Agri-Food & Veterinary Authority (AVA) ensures that GM food are subjected to extensive assessments and approval in other developed countries before they are made available in the Singapore market. Labelling of GM food is also not requirement as making it mandatory will curtail supplies thereby, increasing the prices of food. Nonetheless, the Genetic Modification Advisory Committee (GMAC) and AVA will continue to ensure that labelling requirements in Singapore are in accordance with the latest international developments. Besides, AVA is developing acceptable guidelines on the labelling of GM food with the help of the international Codex Committee on Food Labelling.

Reference:
http://www.ava.gov.sg/NR/rdonlyres/1693236D-7808-4260-BADE-DB7EA7861BEE/20483/STGMFOOD.pdf

Genetic Engineering Technologies (rDNA technology): Microinjection

In this process, DNA is directly injected into cells. Some of these cells will survive and integrate the injected DNA. This method is labour intensive and inefficient compared to other methods.

Adapted from: Safety of Genetically Engineered Foods Approaches to Assessing Unintended Health Effects, Institute of Medicine and National Research Council of the National Academies, 2004, The National Academy Press

Genetic Engineering Technologies (rDNA technology): Electroporation

This method is quite similar to somatic hybridization. Instead of fusing two cells together, like in somatic hybridization, this technique fuses the protoplast with the added DNA in the culture medium. An electrical pulse is also used in this method. The transformed cell will then reconstruct its cell wall and grow to a whole, fertile plant. However, the inability for most plant species to regenerate from protoplasts makes this method ineffective.

Adapted from: Safety of Genetically Engineered Foods Approaches to Assessing Unintended Health Effects, Institute of Medicine and National Research Council of the National Academies, 2004, The National Academy Press

Genetic Engineering Technologies (rDNA technology): Genetic Engineering Agent (Agrobacterium tumefaciens)

The genetic engineering agent that is responsible for the majority of GM crops is a soil microbe called Agrobacterium tumefaciens. Upon infecting a host cell, this pathogen transfers a segment of its own DNA into the plant cell. The host cell then expresses the transferred genes and the instructions for the production of substances that induce the development of a crown gall (disease) will begin. These substances will then be distributed throughout the plant, causing the food produced by these plant to also contain these substances. By exchanging the crown gall disease-causing DNA with a DNA of interest, new strains of this bacterium can be obtained to introduce new useful genetic material into the host plant. Eventually, the progeny of this whole fertile plant would also contain the same inserted DNA of interest.

Adapted from: Safety of Genetically Engineered Foods Approaches to Assessing Unintended Health Effects, Institute of Medicine and National Research Council of the National Academies, 2004, The National Academy Press