Some population groups are also concerned about specific properties of foods - the presence of allergens - the components causing intolerances or which are prohibited by dietary or religious restrictions.
Methods of detection
Methods of immunoanalysis mostly detect proteins, proteoglycans, polysaccharides, or low molecular weight antigens (haptenes).
Immunoassays, due to their comparative simplicity, can be used for broad screening of foods, leaving the final decision for more accurate and sophisticated methods.
Moreover, some of immunoassay modifications (for example, immunochromatographic rapid tests) are simple enough to be used outside laboratories, in kitchens.
Fish
Fish is the only of the 'big eight' of most important food allergens which is still not detected by commercial assays.
Recently we have obtained a single monoclonal antibody X21 recognising heat-resistant muscle derived antigen for all species of finfish tested up to date.
The immunoassay, consisting of this monoclonal capture and affinity purified rabbit polyclonal, reaches subnanogram sensitivity from which it is essential to protect the allergics.
Pork
Meat detection and meat speciation testing is especially important for some social and religious groups. For example, the immunoassay for presence of pork may be used for continuous control of foods. We have developed the set of monoclonal antibodies which are able to distinguish heat-resistant pork-specific epitopes on tropomyosin complex.
These antibodies being used in microplate ELISA and lateral flow rapid test can form immunoassay pairs capable of detecting minor quantities of pork specific antigens (down to 1ng/ml) in food extracts by means of routine laboratory immunoassays. The great advantage of these assays is an extreme thermal resistance of target epitope (up to 30 minutes at 300 °C).
Prolamins
Prolamins are the group of closely related storage proteins from the grains of cereals (wheat, rye, barley, oat and others) enriched by proline acid residues. Prolamins are the major components of human nutrition; their processing is the pivotal part of bakery and beer production; many other food technologies use gluten for stabilisation, stiffening and forming.
To study the immunochemistry of prolamins, we have developed a set of monoclonal antibodies for wheat gliadin.
The resulting antibodies, however, show broad and variable reaction with other cereal species and electrophoretic groups of prolamins.
Based on our anti-gliadin mAbs, we have constructed a group of the assays for determination of different prolamin varieties:
- Total gliadin kit based on two-site binding method and LMW Total gliadin kit based on single antibody competition principle - to be used for quantitative determination of gliadin in ethanol extracts of foods and control of gluten-free foods, which is important for celiac patients.
- Antibody XGY20 specifically binds gliadin of Triticum aestivum but not Triticum durum species. The properties of this antibody enabled us to construct ELISA kit for pasta quality evaluation, showing the consistent results independently of pasta drying temperature.
- Antibody XGY7 shows differential binding activity with barley sorts; it distinguishes between the sorts in individual grains and control barley for sort purity.
Other anti-prolamin mAbs of XGY family can be used for more advanced applications, for example monitoring of beer production, beer brand adulteration control, determination of wheat in rye bakery products, etc.
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- Yuri Lebedin is R&D Manager, Xema Co.Ltd., Moscow, Russia, and Alexandr Grachev is Senior Researcher, Xema Co Ltd, St Petersburg, Russia. www.xema-medica.com.
