whole/equivalent insects, insect fragments, mites, animal hairs and feather
parts. Sometimes both types of analyses
may be required.
The second challenge is if a microscopic analysis is to be performed, the
ingredient statement must be looked at
to see what methodologies will be employed. The main objectives of the
method chosen are to recover as many
of the filth elements in the product as
possible and to leave behind the majority of the product. The method chosen
can be divided into three distinct activities: pretreatment, extraction and recovery. Pretreatment is the preparation of
the product for extraction. The extraction is the separation of an oil phase
from an aqueous phase (light filth elements associate with the oil phase). The
recovery step is where isolated filth elements are placed onto filter paper for
further microscopic examination.
Where internal filth is a concern, the
product must be broken down to simpler components, thus freeing the filth
elements. Sometimes, an acid digestion
must be used. For external filth, a relatively uncomplicated method can be developed, provided that the product can
be easily mixed with an appropriate
reagent and dispersed in a suitable extraction vessel. Dispersions are usually
accomplished in water or in an alcohol-water combination. If the product contains internal or external oil, it must be
defatted to remove the interfering substance. Wet sieving, which removes
water-soluble components and any
added reagents, can reduce the amount
of product to be analyzed. Boiling the
remaining residue will remove any
trapped air that would have made the
residue buoyant. Sometimes, even after
boiling, considerable residue is still floating. Cooling it rapidly to room temperature in a water bath will cause the
material to sink, or a sequestering agent
can be added to suppress the residue further. Stirring oil into the aqueous phase
is a crucial step. If it is not done properly, the residue does not settle out and
all the previous procedures are negated.
The oil is floated off, isolated and finally
placed onto ruled filter paper.
The final and most critical challenge
is having a thoroughly trained micro-
“All edible portions of field and orchard crops are
affected by an assortment of pests.”
scopist who can both quantify and, most
importantly, identify any isolated filth
The analysis of a product for filth is
incomplete if the analyst does not distinguish between kinds of filth contaminants by determining their scientific
names or identities. Filth element identification has become increasingly important in sanitation analyses as it serves as
a guide to the etiology of contamination
in a manner that nonspecific counting of
filth elements cannot duplicate.
When the etiology of contamination
is understood, the value of the analysis is
immeasurably increased since laboratory
clues can be interpreted in terms of
breakdowns in the sanitation of raw materials and in the manufacturing or handling facilities. As a forensic scientist, the
microanalytical entomologist helps determine whether the “crime” of adulteration has been committed and, if so,
develops evidence that helps establish
the guilt or innocence of suspects. What
sets microanalytical entomology apart
from other disciplines of entomology is
its emphasis on the identification of filth
elements, the interpretation of the sanitary significance of filth in food and the
detection of postharvest adulteration
that may occur during the manufacture,
packing or warehousing of food.
serious concern to consumers, food
processors and food regulators, and include birds, bats, lizards, storage insects
and grain mites.
Category 3 includes agricultural pests,
nuisance pests and other incidental
pests. These are natural or unavoidable
contaminants that pose no hazard to
health and are natural or unavoidable, to
a degree, in rural environments where
food crops are grown and harvested.
Category 3 contaminants are an area of
concern over the quality of the food that
enters the marketplace.
As can be seen, correct identification
of contaminants found in food is critical
and essential to proper risk assessment.
The simple counting of isolated filth is
insufficient. Therefore, it is essential that
any laboratory performing filth analyses
have a thoroughly trained microscopist
expert in the field of microanalytical
The next time you are in a restaurant
and hear somebody exclaim, “Waiter!
There’s a fly in my soup,” this analyst
would say, “Ah, yes! But what type of
Assignment of Risk
Filth and extraneous materials found
can be grouped into three risk categories.
Category 1 includes vectors of foodborne pathogens regardless of whether a
microbiological hazard is detected.
These contaminants are associated with a
potential hazard to health and are of the
highest concern to consumers, food
processors and food regulators. Pests in
this category include the housefly, German cockroach, pharaoh ant and house
Category 2 includes pests whose presence in or near food processing or storage areas is an indication of unsanitary
conditions. Pests in this category are of
Richard Haynos is manager and lead
microscopist for the Food Forensics
Department of Certified Laboratories of
Gentry, J. W. and K.L. Harris. 1991.
Microanalytical entomology for food sanitation control,
2nd ed. Arlington, VA: AOAC International.
Gorham, J.R., ed. 1981. Principles of food
analysis for filth, decomposition and foreign
matter, 2nd ed. FDA Tech. Bull. No. 1. Washington, DC: U.S. Food and Drug Administration.
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