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ANALYTICAL PROBLEMS IN FOOD CONTAMINATION |
The symposium will be held at the American Chemical Society National Meeting in Las Vegas, NV on Thursday, September 11, 1997, and will be part of the Agricultural and Food Chemistry Division program.
The topics to be covered include analytical or contamination aspects of insect
and animal filth, decompostion, and foreign objects. The speakers will
participate in a short panel discussion after each session.
Below is listed the titles of the different talks and the abstracts.
For more information
on the symposium please contact:
George C. Ziobro, PhD
U.S. Food and Drug Administration
200 C. St S.W. HFS-315
Washington, DC 20204
phone: 202.205.4994
fax: 202.205.4091
e-mail
GZiobro@cfsan.fda.gov
METHODS FOR THE DETECTION OF FILTH, DECOMPOSITION, AND FOREIGN OBJECTS IN FOODS
What is filth? What is it's source? How does
one analyze for it? What is the influence of the
matrix on the on the recovery of filth? An
overview of the methods for the detection of
filth, decomposition, and foreign objects in
foods will be described and discussed. Specific
methods for each type of contaminant will be
described and the mechanism of detection or
recovery discussed in detail. Current literature
sources of these methods will also be discussed.
MODIFYING AND DEVELOPING METHODS FOR FILTH, DECOMPOSITION, AND FOREIGN OBJECTS
Analytical methods for filth, decomposition, and
foreign objects in foods are generally designed
for a specific product and typically perform as
intended only on that product. Methods can
sometimes be revised and adapted to new
products if the analyst considers the basic
operating mechanism of the methods with
respect to the product composition and analytes
intended for recovery. Approaches for the
revision of existing methods and the
development of new methods for the recovery
of filth, decomposition, and foreign objects from
a variety of food matrices will be discussed.
INVISIBLE FILTH A: ROACHES and THEIR ALLIES
Evidence of food adulteration by cockroaches
and their allies is often invisible. Regulatory
analysts frequently have to put on their
detective's hat to find and identify the
microscopic clues (feces and body fragments)
left behind by the perpetrator(s). This grouping
includes insects known for their ability to
transmit diseases and to be prolific and
gregarious invaders of buildings where food is
processed and stored. A description of the
diagnostic insect fragments and excreta pellets
commonly encountered during filth analyses of
food products will be presented.
INVISIBLE FILTH B: DISEASE-CARRYING FLIES
Twelve species of flies (Diptera) are
documented in the scientific literature as
repeatedly associated with the food-borne
pathogens E.coli, Salmonella, and Shigella. The
"dirty dozen" species are all synanthropic and
belong to one of three families: Calliphoridae
(blow files), Muscidae (house flies) or
Sarcophagidae (flesh flies). A method for
differentiating these flies by the characteristic
venation of the wings is presented, along with
brief descriptions of fly behaviors that may put
food products at risk of microbial contamination.
MAMMALIAN, AVIAN, AND INSECT METABOLIC WASTE IDENTIFICATION
Mammalian, avian, or insect contamination of a
food, drug, cosmetic, or medical device can
sometimes be determined by analysis of the
suspect product for the presence of metabolic
waste products, either fecal or urinary. These
waste metabolites have unique chemical
signatures. The presence of these chemicals
from metabolic waste materials in a sample
confirms contamination. A review of the
different chemical indicators will be presented
as well as the current methodology used for the
detection of these compounds.
CHEMICAL METHODS FOR THE DETECTION OF DECOMPOSITION IN FISHERY PRODUCTS
Decomposition occurs rapidly in fishery
products when effective handling procedures are
not followed. Millions of pounds of fishery
products are affected annually and many of the
decomposed products are associated with
numerous reports of illnesses by consumers. A
wide variety of chemicals are produced during
spoilage which depend upon the microbial
contamination and the conditions of abuse, and
which are further affected by processing,
chemical treatments and storage. Classes of
compounds studied have included the biogenic
amines (histamine, cadaverine, indole), low
molecular weight amines (trimethylamine),
organic acids and breakdown products of
adenosine triphosphate. Practical applications
of selected indicator compounds, the structure
of analytical methods, and the development of
field testing procedures will be discussed.
Correlations between sensory evaluations, the
levels of indicator compounds and the
conditions of spoilage for several major fishery
products will be given.
DIRECT MICROSCOPIC MOLD COUNTS AND HYPHAE RECOGNITION
Mold is the primary agent of decomposition in
fruit and vegetable products. Mold hyphae
which survive processing and remain
recognizable after long periods of time are good
indicators of rot. The presence and enumeration
of mold hyphae in the Howard mold count
method, still going strong after first being
introduced in 1906, is considered a rapid and
reliable quality indicator of the raw fruit and
vegetable stock going into processed products.
Geotrichum candidum, frequently called
"machinery mold" grows on the moist product
contact surfaces of inadequately cleaned fruit
and vegetable processing plant equipment. The
uniquely branched mycelial fragments slough
off and contaminate finished products. Both
Howard and Geotrichum methods use low
magnification compound microscopes and short,
fifteen minute sample preparation times.
Proficient analysts can be trained in two to four days.
USE OF ELECTRONIC IMAGING IN FILTH ANALYSIS
The dramatic decrease in the cost of computers
combined with their increased abilities have
opened the way for their use in filth analysis.
Using inexpensive scanners it is possible to
record the results of TLC plates and gels as well
as "photocopy" labeling. Television or digital
cameras can be interfaced to a microscope to
record the results of an analysis. Using a
variety of examples, this talk will discuss the
setup and use electronic imaging in filth
analysis.
AN IMMUNOASSAY FOR DETECTING INSECT CONTAMINATION OF GRAIN: COMPARISON TRIALS WITH OTHER PROCEDURES
In collaboration with the U.S. Department of
Agriculture and a number of major milling
companies, the "Insect-Detect" immunoassay
for analyzing grain for insect contamination has
been compared with several more traditional
methods, including X-ray, crack and float and
insect fragment counts. Testing was carried out
in blind fashion using clean wheat samples that
were spiked with differing numbers of grain
kernels infested with 4th instar larvae of the
granary weevil. The collaborative trials showed
that the insect immunoassay clearly provided
the most accurate measure of actual insect
infestation, followed by X-ray analysis. While
both crack and float and fragment count
procedures provided a general measure of
contamination, they showed much greater variability.
MACROANALYTICAL PROCEDURES MANUAL - SECOND EDITION
This talk reports progress on the revision of the
Macroanalytical Procedures Manual, a
compendium of methods for detecting filth and
extraneous materials in food products. In
addition to a new format, the manual will
include a new method for examining rodent
filth, a method for differentiating toxic
mushrooms by morphology and a description of
parasites found in seafood. Other changes
include harmonization with USDA
methodologies and other minor modifications of
the manual.
WHERE DO WE GO FROM HERE: THE FUTURE OF FILTH RESEARCH
Filth analysis faces additional challenges as we
approach the 21st century. Among these
challenges are: replacement of current methods
dependent on hazardous solvents, replacement
of methods which are very time and/or analyst
intensive; development of methods for new
products, increased regulatory concerns,
international standardization of methods and
procedures, and detection of genetically
engineered proteins as possible adulterants. As
chemists, where do we go from here?
7 June 1997