13. Diagnostics for saftey and authenication of foods.

Bioluminescence
the use of this method has necesitated the development of specific clean up procedures for removing non microbial ATP from foods. it also can be engineered into bacterial genomes and luminescence used as a measure of biological activity in the presence of environment toxins.

Enzyme Based Assays and immunodiagnostics
sensitivity, specificity and simplicity have been improved by conjugating enzymes with specific antibody giving rise to Enzyme Linked Immunosorbent Assay(ELISA).

In food microbiology, ELISAs have a greater impact. Pathogens including Salmonella, Listeria and Escherichia Coli and the bacterial toxins from Staphylococcus Aureus, Bacillus Cereus and Clostridium Botulinum can now be detected using commericial kits. Furthurmore, ELISA kits are able to detect fungal toxins such as aflatoxin and ochratoxin. It is also used to detect Clostridium Botulinum enterotoxins and certain molds (e.g. Asperigiullus and Penicillium spp.)

DNA Probes
Gene probes are specific. Simple methods based on nucleic acid probes are developed for detecting specific genes expressing gungal toxins. they also have potential in authenicity testing. however, a problem is faced as most DNA probes can only detect approximately 10^5 cells/ml in a food matrix.and many pathogenic microorganisms that may be present at very low levels need to be enriched using conventional cultural methods. this problem can be solved as nanogram quantities of DNA can be amplified using the polymerase chain reaction (PCR) and is able to detect Legionella at a levele of 100 cells/ml in 4h. Similar developments were developed to detect Salmonella. therefore, gene probes are constructed to contain complementary bases which hydrise target DNA sequences.

Biosensors
Most diagnostic involve the specific binding of target molecule to a recognition molecule. binding event is sensed by labelling the ligated complex. optical biosensors are developed for the estimation of biotin and folate and for the detection of Salmonella and Listeria.

Reference:
Institute of Food Science and Technology (UK). Diagnostics for saftey and authenication of foods. Guide to Food Technology. Year 1996. Pages 41-45.