By Monique Bremer, Ph.D.
Selecting a Suitable
these assays will also become commercially available. With the introduction of
these types of assays, routine screening
of products for the presence of the “Big
Eight” will become possible.
Undeclared traces of allergenic sub-
stances in food may cause problems
for allergic individuals as they are inad-
vertently exposed to the offending sub-
stance. To improve consumer safety,
labeling of the eight major allergens be-
came mandatory within the U.S. in 2006. These so-called “Big Eight”
include tree nuts, peanuts, soy, eggs, milk, fish, wheat and shellfish.
Strip tests (Figure 1) are based on the
formation of complexes between anti-allergen antibody-coated colored beads
with allergenic proteins in the sample
and anti-allergen antibodies on the test
strip. These complexes give rise to a colored test line on the strip, indicating a
positive (i.e., allergen-containing) sample. In a similar way, a colored control
band is formed, indicating that the test
has been carried out correctly.
Strip tests are very easy to use, inexpensive, rapid (analysis time of a few
minutes), do not require instrumentation and can therefore be used in the
field. Today, most available strip tests are
only qualitative; however, it is anticipated that in the near future, more and
more suppliers will deliver simple hand-held readers with which semi-quantita-tive results can be obtained. With strip
tests, only single samples can be analyzed for the detection of a single allergen at one time.
To comply with allergen labeling laws and to protect their own reputation and
business, food producers need analytical methods to monitor the presence of allergens during production and to avoid cross-contamination in production lines.
How can food producers effectively select and implement a detection method
from the range of methods available? In this article, the most widely used methods
available at present and upcoming ones are described, and the pros and cons of the
various methods are analyzed to facilitate the selection procedure.
ELISAs are carried out in multiple-well strips or 96-well microtiter plates.
The proteins of the allergenic compound are detected by a specific en-
Immunological Screening Methods
Immunological methods are most widely used to detect allergenic
products at trace levels (i.e., a low mg/kg range) in foods. These methods are based on the binding of an allergenic protein by specific antibodies. Immunological methods are available in different formats,
with the more conventional formats being enzyme-linked im-munosorbent assays (ELISAs) and strip tests. Over the past few
decades, many ELISAs and strip tests for the detection of different allergens have been developed and have become commercially available. More recently, research has focused on multiple-allergen
Figure 1: Principle of a strip test: Anti-allergen antibody-coated
detection (i.e., the development of methods in which several allergens
colored beads form a complex with allergens in the sample and
or allergenic compounds can be detected simultaneously). These as-
anti-allergen antibodies on the strip. This leads to a colored test
says are usually developed on biosensors and microsphere-based flow line indicating a positive (i.e., allergen-containing) sample. A
cytometric systems. It is anticipated that within the next few years,
colored control band indicates correct performance of the test.