investigational procedure, including
sample inspection, preparation, and
identification of target contaminants.
The sources of contamination are diverse, whether individual or related, or
even unknown. Often, little is known
about the contaminants, how many
there might be, what size, what their
regulatory status might be, or whether
they might be in a food mixture.
Preexamination steps allow judgments to be made as to whether the
targets can be separated by size, shape,
mass or magnetic properties, the type of
samples and contaminants (e.g., organic
or inorganic), amount, circumstances of
contamination, and levels. It is normally
required to conduct resampling, inspection, macroscopic examination, extraction, filtration, floating, sieving, burning, dyeing, and further examination
using X-ray, metal detectors/magnets,
and other screening or targeting technologies. An example might be to use
magnets to gather and identify ferrous
metal particles from liquid samples.
2. Identify contaminants. Once the
suspected foreign matter screening procedures are carried out using stereo or
dissecting microscopic examinations as
a starting point, one can obtain detailed
evidence, identifying the morphology
and deciding what methods of analysis
should be applied. For example, if a
complainant believes that pieces of
glass were observed by the naked eye
in a food, it may be that the material
consists of rocks, salt, sugar, plastics,
minerals, struvite, or tartrate crystals.
If needed, a compound microscope,
bright-field/dark-field microscope, polarized microscope, or scanning electron
microscope could be applied to reveal
more details. Further tests are determined based on the results of microscopic examinations. Selection of such
analytical strategies may require a combination of techniques or the development of multidisciplinary approaches,
depending on contaminant conditions
and the goals of the investigation.
3. Conduct physical property tests.
A polarized microscope is used to dis-
play birefringent properties from some
materials, such as synthetic polymers.
Spectroscopic techniques can reveal
specific functional groups of a chemical
material. For example, different plastics
may be identified by FTIR analysis.
Physical properties can be classified by
many characteristics and features, such
as size, shape, thickness, magnetic char-
acteristics, solubility, buoyancy, elastic-
ity, flexibility, flammability, temperature
4. Perform a chemical examination.
Chemical analysis, including an elemental analysis, can reveal characteristic
features that enable an understanding
of chemical properties. Histochemical
staining techniques are useful to test
the chemical and
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(continued on page 62)