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1
Introduction
SOURCES OF MICROORGANISMS IN FOODS
Man's food supply consists primarily of plants and animals and products
derived from them. Microorganisms are naturally present in the soil, water,
and air, and therefore exterior surfaces of plants and animals are contam-
inated with a variety of microorganisms. There is little specificity to this
microflora since it reflects that of the environment in which the plants
were grown and the animals were raised. Interior tissues of plants and
animals usually contain few, if any, microorganisms. The gastrointestinal
tracts of animals, however, contain large numbers of organisms. But if
proper slaughtering-dressing procedures are used, contamination of inte-
rior muscle tissue can be avoided.
From the time of slaughter, catch, or harvest, the surface and interior
tissues of animals and plants are subject to contamination. This is due in
part to the breakdown of normal defense mechanisms, particularly in
animals. Each processing step subjects the raw material to additional
opportunities for contamination. Sources of contamination include surfaces
of the harvested plant or slaughtered animal, water, equipment, utensils,
workers, and the processing environment.
MICROBIAL ACTIVITIES IN FOODS
Historical Aspects
During their existence, human beings have been confronted with the
problem of limited shelf-life of animal and plant foods in part due to
41
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42 EVALUATION OF THE ROLE OF MICROBIOLOGICAL CRITERIA
microbial activities. During the last 5,000 to 10,000 years a variety of
techniques (such as drying, salting, heating, fermentation, refrigeration,
or freezing) evolved empirically and contributed to the increased shelf-
life of plant and animal foods. These techniques, which controlled mi-
crobial activity to a greater or lesser extent, were applied before the
mechanism of their effect was understood. In the early 1800s Francois
Nicholas Appert was awarded a patent for a practical method of food
preservation, namely, "canning." Since that time, and particularly during
the last 40 years, new processes have been developed to extend shelf-life
of foods. Although some others may have suggested microbial involve-
ment in food spoilage at earlier dates, it was Louis Pasteur who in the
mid-1800s first established a scientific basis for the direct relationship
between food spoilage and microbial activity. Microorganisms responsible
for foodborne diseases were first recognized around 1880. Since that time,
the number of microbial agents recognized as involved in foodborne illness
has increased steadily.
Spoilage, Pathogenic, and Useful Microorganisms
Microorganisms associated with foods can be categorized as "spoil-
age," "pathogenic," or "useful." Spoilage microorganisms are those
that can grow in a food and cause undesirable changes in flavor, consis-
tency (body and texture), color, or appearance. Also bacterial enzymes
may effect slow deterioration of frozen or dried foods during long-time
storage. These changes diminish the quality characteristics of foods and
may render them ultimately unfit for human consumption. For example,
refrigerated perishable foods such as milk, fresh meat, poultry, fish, fruits,
tat ~~ r
and vegetables lose some quality characteristics during normal storage
and ultimately spoil, due in part to the activity of microorganisms capable
of growth at refrigeration temperatures. Usually, extensive microbial growth
(millions of organisms per g or cm2) occurs before quality losses are
perceptible. These changes, when perceived by the consumer, serve as
an alert that extensive microbial activity has taken place.
Pathogenic microorganisms can render foods harmful to humans in a
variety of ways. Foods may serve as the vehicle for the introduction of
infectious microorganisms into the gastrointestinal tract, e.g., Salmonella
and Shigella. Multiplication of certain microorganisms in foods prior to
consumption may result in production of toxins, e.g., Clostridium botu-
linum, Staphylococcus aureus, and Bacillus cereus. Foods may also be
the vehicle for microorganisms that form toxins in viva, e.g., Clostridium
perfringens and certain pathogenic Escherichia colt.
With some foods, conditions are chosen to favor the development of
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INTRODUCTION
43
useful microorganisms such as lactic acid bacteria and yeasts, which are
either naturally present or added intentionally. Such foods as cheeses,
yogurt, breads, pickles, and fermented sausages offer desirable organo-
leptic properties and shelf-life.
Food as a Selective Environment
Microbial activities in foods can be viewed from the perspective of the
food as a "selective environment," despite the diversity of microorgan-
isms that contaminate the surfaces of the raw materials. The selectivity
is imposed by the physical-chemical characteristics of the food, the ad-
ditives it contains, the processing techniques, the packaging material, and
the storage conditions. It is necessary to distinguish between the shelf-
life of two broad categories of foods, namely those that are shelf-stable
and those that are perishable. For this discussion, shelf-life will be treated
as it relates to microbial activity only.
Microbiological shelf-stability of many foods is related to storage con-
ditions. For example, dried and frozen foods are microbiologically shelf-
stable as long as they remain dry or frozen. Shelf-stable foods are not
necessarily sterile; indeed, many do contain microorganisms. Some shelf-
stable canned foods may undergo microbiological spoilage if they are
exposed to elevated temperatures permitting the growth of surviving ther-
mophilic sporeforming bacteria, whereas these organisms are inactive at
ambient temperatures and indeed tend to die during normal storage. Shelf-
stable food is distinguished from perishable food in that an attribute or
attributes of the shelf-stable food prevented the growth of contaminating
microorganisms. For example, certain canned products are heat processed
to the degree that they are sterile; the attribute assuring stability of such
products is elimination of all living forms. With many shelf-stable foods,
other attributes prevent microbial growth. Dried beans are shelf-stable
because they contain insufficient moisture to permit microbial growth.
Mayonnaise is shelf-stable because it contains sufficient quantities of acetic
acid in the moisture phase of the product to prevent growth of contami-
nating organisms. Certain canned cured meats are shelf-stable, not because
they are sterile, but because sublethal heat treatment so injures surviving
spores that they are incapable of outgrowth in the presence of salt and
nitrite. The distinguishing characteristic of shelf-stable foods, then, is their
resistance to microbiological spoilage. Microbial growth in such products
is an abnormal and unexpected event.
Perishable foods, on the other hand, have a finite shelf-life and if not
consumed, will spoil at some time during storage. The exact time of
spoilage depends upon a great number of variables. Though various pro
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44 EVALUATION OF THE ROLE OF MICROBIOLOGICAL CRITERIA
cessing procedures, additives, packaging methods, and storage conditions
may be applied to increase shelf-life, microorganisms capable of growth
survive and ultimately grow. When such growth proceeds to the extent
that undesirable changes are perceptible to the processor, preparer, or
consumer, the food is deemed of inferior quality or spoiled and is rejected.
The distinguishing feature of perishable foods, in contrast to shelf-stable
foods, is that microbiological spoilage is an expected event. It will ulti-
mately occur even if the food has been prepared from wholesome raw
materials and has been properly processed, packaged, and stored.
Microflora of Processed Foods
Although the microflora of raw materials is usually heterogeneous,
processing of foods (except those that are sterile) often imposes a char-
acteristic and highly specific microbiological flora. The normal flora of
severely heat processed, but not sterilized, low-acid canned foods is com-
prised of thermophilic sporeforming bacteria, the most heat-resistant mi-
crobial components of the raw materials. The predominating flora of shelf-
stable canned cured meats consists of mesophilic aerobic and anaerobic
sporeforming bacteria, the predominant organisms resistant to the heat
process applied to these products. The normal flora of mayonnaise and
salad dressing is comprised of small numbers of sporeforming bacteria,
yeasts, and lactic acid bacteria. Aerobic sporeforming bacteria predomi-
nate in dry spices and in a number of dry vegetable products. Molds and
yeasts predominate in dried fruits. The normal flora in carbonated bev-
erages is comprised of yeasts. In each of the foregoing, the surviving and
predominating microflora reflects the nature of the raw materials, pro-
cessing conditions, packaging, and storage of the shelf-stable product.
However, spoilage is still possible. If the severely heat-processed canned
foods were exposed to high temperatures during storage, spoilage due to
the germination and outgrowth of thermophilic sporeforming bacteria might
occur. If shelf-stable canned cured meat were to contain excessive numbers
of aerobic sporeforming bacteria, growth of these organisms might result
in spoilage, despite an adequate heat process and normal levels of salt
and nitrite. Excessive levels of yeasts or lactic acid bacteria might result
in their growth and subsequent spoilage of the mayonnaise, despite levels
of acetic acid that would assure the stability of a product containing
"normal" levels of the same organisms. Time/temperature abuse of an
ingredient of a carbonated beverage (for example, a flavor) may lead to
the development of large numbers of yeasts that could overcome the effect
of carbonic acid, which would normally render the same beverage stable.
The normal flora in microbiologically shelf-stable products is, therefore,
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INTRODUCTION
45
rather specific. If the stabilizing nature of the system should be overcome,
this microflora may multiply and cause spoilage-an unexpected event.
With perishable products, the microflora that survives processing may
be heterogeneous, but that portion of it developing during storage and
causing spoilage is usually quite specific. For example, a heterogeneous
flora exists on raw red meats, poultry, and fish as a result of contamination
from the animal and/or the processing environment. Yet, during refrig-
erated storage of such products, spoilage is caused predominantly by a
highly specific group of microorganisms, namely Pseudomonas and closely
related aerobic, psychrotrophic gram-negative bacteria. If the same prod-
ucts are vacuum-packed in oxygen-impermeable films, a different micro-
flora becomes predominant, namely, lactic acid bacteria that grow under
both aerobic and anaerobic conditions. In both examples, despite the
heterogeneous flora of the finished product, a rather restricted group of
microorganisms may develop and ultimately cause sensory changes in the
product. Similar relationships exist for many other perishable foods.
It follows that since most classes of perishable foods constitute selective
environments for rather restricted groups of microorganisms, the spoilage
caused by the growth of these microorganisms manifests itself in a char-
acteristic manner, i.e., normal spoilage pattern. For example, when pseu-
domonads and other closely related gram-negative psychrotrophic aerobic
bacteria grow to large numbers on the surface of refrigerated fresh meat,
poultry, and fish, sensory changes occur. The first manifestation of spoil-
age is development of off-odor. As growth proceeds, slime may develop
and the off-odor may intensify. The normal spoilage pattern of a perishable
food can be a safeguard, since under certain situations it warns the pro-
cessor, preparer, or consumer that the food is no longer edible.
Changes in processing of perishable foods must take into account the
effect these changes may have on the spoilage flora, and thus on the
normal spoilage pattern of the food involved. If such changes tend to alter
the normal patterns of spoilage the public health aspects must be taken
into account. A classic example of this relates to the merchandising of
smoked whitefish. For generations this product was merchandised under
conditions where the fish was exposed to air. Spoilage was evidenced by
the development of bacteria which produced off-odors and slime that were
readily recognized by the consumer and caused rejection of the product.
Then it was discovered that the shelf-life of smoked fish could be signif-
icantly increased if the product was packed in an oxygen-impermeable
film. With extended storage of the product under these conditions,
C. botulinum type E was able to grow and produce toxin, just as it would
have been able to do in the conventionally packaged product. However,
under these storage conditions the aerobic bacteria producing off-odor and
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46 EVALUATION OF THE ROLE OF MICROBIOLOGICAL CRITERIA
slime could not develop and the normal spoilage flora was now comprised
of lactic acid bacteria that did not produce off-odors. This change in the
normal spoilage pattern of the product reduced the probability that the
consumer would reject a product that had been held in storage out of
refrigeration for an extended period of time. This led to a multistate
outbreak of type E botulism (Kautter, 19641. Thus, it is essential that if
changes are made in the processing or merchandising of a perishable
product, the influence of these changes on the normal spoilage patterns
of the product be taken into account.
CONTROL OF MICROORGANISMS IN FOODS
Control must be exercised over three different categories of microor-
ganisms that may be present in foods: (1) those that have the potential for
producing foodborne disease, (2) those that cause food spoilage, and (3) those
that grow in food and produce desirable changes.
Effective food control programs eliminate the potential for foodborne
illness in a variety of ways. Processing techniques that cause destruction
of pathogens may be employed, e.g., the pasteurization of milk to destroy
Coxiella burnetii and Mycobacterium tuberculosis and less heat resistant
pathogens such as the diphtheria bacillus, salmonellae, and pyogenic strep-
tococci, and the 12-D process for the destruction of C. botulinum in low-
acid canned foods. In other cases, toxigenic and infectious microorganisms
are controlled by product formulation (acetic acid in mayonnaise) or stor-
age conditions (the refrigeration of perishable pasteurized canned cured
meats to control the growth of C. botulinum). In yet other situations, the
ultimate control is exercised by the person who prepares the food (adequate
cooking of poultry to eliminate salmonellae and of pork to eliminate
trichinellae). Despite such efforts, food control programs have fallen short
of their goals for controlling foodborne pathogens (see in particular Chapter 4
where foodborne illness of microbiological origin is treated in detail).
Control measures directed toward prevention of spoilage have also fallen
short of the ideal. Although precise figures are difficult to obtain, it is
estimated that one-fourth of the world's food supply is lost through mi-
crobial activity alone. The control of food spoilage is a prime economic
objective of control programs. For products designed to be shelf-stable,
The 12-D process is the minimum heat treatment applied to low-acid canned foods; it provides
for the reduction of 10~2 heat-resistant spores of C. botulinum to one. This requires approximately
2.5 minutes exposure at 121.1°C (250°F) or its equivalent.
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INTRODUCTION
47
control is accomplished through processing and/or formulation procedures
that result in the inhibition of spoilage organisms. With perishable foods,
the object is to achieve the longest possible shelf-life consistent with
product safety. In general, this is attempted by instituting measures that
will result in products with low microbial loads, since shelf-life and initial
level of contamination are usually directly related in perishable foods.
Control of remaining microorganisms is most often achieved by proper
refrigerated storage.
The desirable organoleptic properties (taste, odor, body, and texture)
of such foods as cheeses, yogurts cultured buttermilk, sour cream, pickles,
and fermented sausages result in part from the activities of a specific
microbial flora. Extensive microbiological control procedures are needed
to produce "cultured products" of high quality and to ensure that the
microbial activities are guided in such a manner that the end products
have the desirable sensory properties. For example, in cultured dairy
products this is achieved by (1) proper selection and handling of starter
cultures, (2) control of the presence of antibiotics and bacteriophages, and
(3) checking by chemical and organoleptic means the progress of microbial
activity in raw and finished products. These measures can influence both
the quality and the safety of the food. For example, the lack of acidity
caused by culture failure can allow the development of S. aureus, which
could result in cheese containing staphylococcal enterotoxin.
Another objective of food control programs is to keep filth and other
foreign substances out of food. In some cases, extraneous matter is of
public health concern, e.g., rodent pellets and hairs; in other instances,
the foreign material is of aesthetic rather than health significance, e.g.,
certain cereal insects.
Finally, another objective of food control programs is to ensure that
packaging, storage, handling, transportation, display, and sale of foods
are all properly carried out. Processors and regulatory officials can exert
control over a product while it is packaged, stored, and readied for dis-
tribution from the plant of origin. But beyond that point, the intensity of
control rapidly diminishes.
The bulk of the problems with foodborne disease and food spoilage
results from events that occur after food has left the processing plant-
during transport, during retail sales, and ultimately in the food service
establishment or home (CDC, 19811. In these locations, control on oc-
casion either does not exist or is executed ineffectively, thus producing
the weakest link in the food chain. Many improvements in food control
that are made at the processing level will be nullified if handling procedures
beyond the plant are not effectively controlled.
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48 EVALUATION OF THE ROLE OF MICROBIOLOGICAL CRITERIA
APPROACHES TO MICROBIOLOGICAL CONTROL IN FOODS
Traditionally, three principal means have been used by regulatory agen-
cies and food processors to control microorganisms in foods. These are
(1) education and training, (2) inspection of facilities and operations, and
(3) microbiological testing.
Although food handlers have the potential for contaminating foods with
disease-producing microorganisms, i.e., staphylococci, salmonellae, and
hepatitus virus, health examination of food handlers is a nonproductive
approach to the control of foodborne illness. Specimens from food handlers
have traditionally been examined only for a few microorganisms, and such
tests do not always detect carriers. Screening tests cannot be made with
sufficient frequency to be effective in detecting the carrier status in persons
who are continually exposed to the risk of acquiring foodborne pathogens.
Negative tests convey to food handlers, managers, and public health per-
sonnel the erroneous concept that the workers are free of infections and
therefore incapable of transmitting foodborne pathogens to the foods they
handle. Although direct transfer of pathogens from food handlers to food
is a hazard, far more frequently improper food-handling practices create
a hazard that is not circumvented by health examinations.
Education and Training Programs
These programs are directed primarily toward developing an under-
standing of the causes and consequences of microbial contamination and
of measures to prevent contamination and subsequent growth. The extent
of training required of personnel within processing plants and food service
establishments depends upon the technical complexity of the food oper-
ation and the level of responsibility of the individuals being trained. In-
depth training may be necessary for supervisory personnel, while for others
training may relate only to specific aspects of a food operation. Although
education and training are necessary parts of any food control program,
standing alone they have certain limitations and shortcomings. Personnel
turnover in the food industry is both constant and rapid, and thus education
of workers must be a continuing rather than a sporadic exercise. It is
essential that supervisory personnel be properly trained with respect to the
hazards associated with the operations for which they have responsibility.
Inspection of Facilities and Operations
Inspections of facilities and operations are commonly used to evaluate
adherence to good handling practices. The U.S. Department of Agriculture
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INTRODUCTION
49
(USDA) relies almost entirely upon this approach in the regulation of meat
and poultry operations. Resident inspectors observe all phases of pro-
cessing from the live animal to the finished product. Little reliance is
placed upon microbiological testing in the meat and poultry control pro-
grams. In its activities with respect to dried milk and egg processing, the
USDA relies not only on inspections but also on microbiological testing
of the finished products.
The Food and Drug Administration (FDA) also relies heavily on in-
spection of facilities and operations. In addition, both in-process and
finished product samples are collected and analyzed. Results of such
analyses are used to corroborate observations made during inspections;
they are not intended to perform the processors' responsibility of micro-
biological control on a day-to-day basis. The FDA inspection program is
designed to determine whether or not processors are operating in com-
pliance with the Federal Food, Drug and Cosmetic Act. Thus, this activity
is in sharp contrast to that of the USDA meat and poultry inspection,
wherein resident inspectors are charged to assure that plants are in com-
pliance with the Federal Meat Inspection Act and Poultry Products In-
spection Act on a day-to-day basis.
Procedures vary widely at the state, county, and municipal levels, but
the approach to regulatory control is primarily through periodic inspection
of facilities and operations.
Just as with the education and training approach to food control, in-
spection of facilities and operations alone is not sufficient. Generally, the
inspector relies upon advisory or mandatory documents such as Good
Manufacturing Practice (GMP) guidelines and Codes of Hygienic Practice
or local food control laws, ordinances, or regulations. Unfortunately, such
documents often refer to stated requirements without specifying what is
considered to be in compliance with the requirements.2 This lack of spec-
ificity, or failure to indicate the relative importance of the requirements,
leaves interpretation of compliance solely at the discretion of the inspector.
Lack of discrimination between important and relatively unimportant re-
quirements may result in overemphasis upon unnecessary or relatively
minor requirements, and thus increase costs without significantly reducing
hazards. Requirements that are critical to the safety of the product may
be overlooked or underestimated.
2A notable exception is the USPHS/FDA Grade A Pasteurized Milk Ordinance wherein for
each requirement a statement is given that specifies what constitutes compliance with the re-
quirement.
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50 EVALUATION OF THE ROLE OF MICROBIOLOGICAL CRITERIA
Microbiological Testing
Samples of ingredients, materials obtained from selected points during
the course of processing or handling, and finished products may be ex-
amined microbiologically to determine adherence to Good Manufacturing
Practices. In some instances, foods are examined for a specific pathogen
or its toxins, but more often examinations are made to detect organisms
that are indicative of the possible presence of pathogens or spoilage or to
detect presence of the specific spoilage organisms or their products. Mi-
crobiological testing is absolutely essential to the control of certain prod-
ucts, e.g., to assure that dried milk and eggs and confectionery products
are free of a Salmonella hazard. Testing is essential to assure that critical
raw materials are satisfactory for their intended use, e.g., to assure that
the sugar used in canning meets established standards and to assure that
critical products used in dried blends are free of Salmonella.
Microbiological testing has severe limitations as a control option. The
most serious shortcoming is the constraint of time. Most microbiological
test results are not available until several days after testing. Therefore, if
finished product acceptability must be measured by microbiological test-
ing, the product is held pending results. With perishable foods, this is
generally not possible; with shelf-stable foods, the warehousing of finished
product increases costs. If in-line samples are collected and analyzed, the
results are of retrospective value since the finished product has already
been produced. Other difficulties are related to sampling (see Chapter 6),
analytical methods (see Chapters 4 and 5), and the use of indicator or-
ganisms for pathogens (see Chapter 51.
Composite Programs
Sophisticated microbiological control programs encompass the three
approaches, namely education and training, inspection of facilities and
operations, and microbiological testing. The emphasis varies from plant
to plant, product to product, and establishment to establishment, as does
the success of the various microbiological control programs.
The Hazard Analysis Critical Control Point (HACCP) System
The HACCP system, first presented at the 1971 National Conference
on Food Protection (APHA, 1971), provides a more specific and critical
approach to the control of microbiological hazards than that achievable
by traditional inspection and quality control procedures. The system con-
sists of: ( 1 ) identification and assessment of hazards associated with grow
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INTRODUCTION
51
ing, harvesting, processing-manufacturing, marketing, preparation, and/
or use of a given raw material or food product; (2) determination of critical
control points to control any identifiable hazarded; and (3) establishment
of procedures to monitor critical control points. Analysis of factors to be
considered in hazard analyses, detailed in Chapter 3, leads to establish-
ment of the control points to be monitored. Depending upon the situation,
the monitoring may involve inspections, physical or chemical measure-
ments, and/or microbiological testing.
The HACCP system is a structured approach to microbiological quality
control. The key lies in the meaning of "critical control point," which
is a location or a process that, if not correctly controlled, could lead to
contamination of the product with foodborne pathogens or spoilage mi-
croorganisms or their survival or unacceptable growth. A careful hazard
analysis leads to the identification of critical control points. Once the
critical control points have been identified, the final problem involves
finding the most effective and practical means for monitoring these points.
Properly applied, the HACCP system separates the essential from the
superfluous aspects of microbiological control. As discussed in Chapter 10,
use of the HACCP system by industry not only offers the food processor
a rational approach to microbiological control, but also leads to more
effective and economical utilization of regulatory manpower. The in-
spector focuses initial attention on monitoring records and, if the results
indicate satisfactory control over critical control points, logically con-
cludes that efforts could be more effectively expended on other food-
processing operations either with the same or with other food-processing
plants.
The HACCP system has been successfully applied to the microbiological
control of low-acid canned foods. Indeed, in the United States monitoring
of critical control points in the production of these products is subject to
federal regulations. Many industrial organizations have adopted the HACCP
system as a means of microbiological control over products other than
low-acid canned foods. The system has also been applied to microbio-
logical control over food service establishments and has even been used
in the home. Unfortunately, only limited use has been made of the HACCP
system by regulatory authorities. Impediments to its more widespread use
are discussed in detail in Chapter 10.
THE CURRENT ROLE OF CRITERIA
IN MICROBIOLOGICAL CONTROL IN FOODS
Microbiological criteria in one form or another have been in existence
in the United States since the early part of this century. The more prominent
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52 EVALUATION OF THE ROLE OF MICROBIOLOGICAL CRITERIA
microbiological standards formulated and enforced by federal regulatory
agencies are those for milk, water, shellfish, and egg products. Other
standards exist for aflatoxins, scombroid toxin, paralytic shellfish toxin
in specific foods, and defect action levels for specific foods. The enforce-
ment of these standards has contributed to significant improvements in
the microbiological safety and quality of these products. At the federal
level no formal microbiological standards exist for other foods. Despite
this lack, existing laws provide sufficient authority for the removal from
the marketplace of products with microbiological conditions that pose a
threat to health. Therefore, "implied" microbiological standards do exist.3
Even in the absence of a threat to health, existing federal laws provide
sufficient authority for seizure of products if there is direct or indirect
evidence that a product is contaminated with filth, e.g., seizure of tree
nuts contaminated with E. cold and seizure of raw shrimp contaminated
with salmonellae. In the latter case, seizure is based not on a health hazard,
but on the premise that the presence of salmonellae is indicative of in-
sanitation in the processing of the shrimp. Federal laws also give sufficient
authority for seizure of products for aesthetic reasons. If GMPs were held
to have the force of law, they could provide authority to the FDA to use
microbiological criteria therein in the assessment of good manufacturing
practices. However, with few exceptions, umbrella GMPs are inadequate
for such purposes as they lack precise, achievable standards (U.S. v. An
Article of Food, 19721.
Thus, at the federal level, though limited use has been made of formal
standards, the law has nevertheless provided adequate authority for seizure
of foods known to present health hazards. A detailed discussion of the
current status of microbiological criteria and their legislative bases is
3Section 402(a)(1) of the Food, Drug and Cosmetic Act (U.S. Congress, 1980) specifies that
a food that bears or contains any poisonous or deleterious substance that may render it injurious
to health is deemed to be adulterated. Pathogens or their toxins may be considered as deleterious
or poisonous substances, respectively. However, the presence of certain pathogens in any number
in a food available to consumers must not be tolerated (e.g., Shigella dysenteriae, Vibrio cholerae
O-1); the mere presence of certain others is not hazardous although high populations of them
would be (e.g., C. perfringens, B. cereus). Section 402 (a)(1) does not make this distinction.
Accordingly, microbiological criteria become useful in interpreting this section of the act as they
specify the pathogen or toxin of concern, the analytical method by which they may be detected,
the sampling plan for obtaining the food to be analyzed, and the level of population of a pathogen
or concentration of toxin that must not be exceeded. Nevertheless, in the absence of such criteria
"implied" standards for pathogens do exist by the very nature of the wording of Section 402(a)(1),
and have been enforced by the FDA when in its judgment a direct health hazard exists, i.e., a
food contains a deleterious agent that may render it injurious to health. Thus, microbiological
criteria provide a means for interpreting the provisions of 402(a)(1) as it pertains to pathogens.
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INTRODUCTION
53
presented in Chapter 8. Microbiological criteria adopted by state, county,
and local health agencies are also included in this review. Twenty-five
states have microbiological criteria, usually guidelines, for one or more
foods (Wehr, 19821.
Microbiological quality standards have recently been proposed by the
FDA. These standards do not purport to have any relationship to safety.
As yet, none has been adopted. For further discussion of microbiological
quality standards, see Chapter 2.
Microbiological criteria have long been used by industry to assess the
microbiological safety and quality of its products, for in-process moni-
toring, and for microbiological inspection of raw ingredients. Generally,
these criteria are internally generated and proprietary, though some com-
panies publish the microbiological criteria relating to their finished prod-
ucts for sales promotion purposes. Microbiological criteria are also used
by industry in connection with purchase specifications. These criteria are
included in purchase contracts between vendors and purchasers of prod-
ucts. Industry "standards" exist for certain raw materials, the best ex-
amples being the National Food Processors Association standards for
sporeforming bacteria in sugar and starches and the National Soft Drink
Association standard for the presence of yeasts, molds, and bacteria in
sugar.
CONSIDERATIONS IN ESTABLISHING CRITERIA
The establishment of a meaningful microbiological criterion is not a
simple process. In 1964, the Food Protection Committee of the National
Research Council proposed three basic principles for setting a microbio-
logical criterion (NRC, 19641. These principles were that microbiological
criteria for foods should: (1) accomplish what they purport to do, i.e.,
reduce public health hazards; (2) be technically feasible, i.e., attainable
under conditions of good commercial practice; and (3) be adminstratively
feasible.
Difficult questions must be answered before a useful microbiological
criterion can be established. For example, what foods should be subject
to microbiological criteria and on what basis? What contaminants should
be specified (pathogens, indicator organisms, toxins, etch? What limits
should be placed on the presence of each contaminant? How large a sample
of each food should be examined and by what method? The most com-
prehensive discussion of these questions on the international level is pro-
vided by the International Commission on Microbiological Specifications
for Foods (ICMSF, 1985) and the Codex General Principles for the Es-
tablishment and Application of Microbiological Criteria for Foods (see
Appendix B).
OCR for page 54
54 EVALUATION OF THE ROLE OF MICROBIOLOGICAL CRITERIA
THE CURRENT REPORT
This book is the result of the Subcommittee on Microbiological Cr~-
ter~a's examination of the value of microbiological criteria in the control
of food quality and safety. The subcommittee tried to bring the uses of
microbiological criteria into perspective with respect to their place in a
total program for microbiological control of foods in the United States.
The book contains chapters on the purpose of microbiological criteria and
definitions of terms used in relation to them, on factors that influence the
selection of foods to be considered for criteria, on the selection of mi-
croorganisms as components for criteria, on the selection of sampling
plans, and on the action to be taken when a criterion is exceeded. Foods
of several major commodity groups are identified as appropriate candidates
for microbiological criteria on the basis of recognized problems related
to safety and quality. Finally, plans of action are presented for imple-
mentation of the HACCP system and development of meaningful micro-
biological criteria. The subcommittee's responses to specific questions
raised by the sponsoring agencies and the general recommendations of
the subcommittee are presented in sections devoted to those purposes.
REFERENCES
APHA (American Public Health Association)
1971 Proceedings of the 1971 National Conference on Food Protection. Washington, D.C.:
U.S. Department of Health, Education and Welfare, Public Health Service, Food and
Drug Administration.
CDC (Centers for Disease Control)
1981 Foodborne Disease Outbreaks. Annual Summary 1979. Issued April 1981. Atlanta:
U.S. Department of Health and Human Services, Public Health Service, Centers for
Disease Control.
ICMSF (International Commission on Microbiological Specifications for Foods)
1985 Microorganisms in Foods. 2. Sampling for microbiological analysis: Principles and
specific applications. 2nd Ed. In preparation.
Kautter, D. A.
1964 Clostridium botulinum type E in smoked fish. J. Food Sci. 29:843-849.
NRC (National Research Council)
1964 An Evaluation of Public Health Hazards from Microbiological Contamination of
Foods. Food Protection Committee. Washington D. C.: National Academy of Sciences-
National Research Council.
U.S. Congress
1980 Federal Food, Drug and Cosmetic Act, as amended. Washington, D.C.: U.S. Gov-
ernment Printing Office.
U.S. v. An Article of Food
1972 Pasteurized whole eggs, 339 F. Supp. 131 (N.D. Gal, 1972).
Wehr, H. M.
1982 Attitudes and policies of governmental agencies on microbial criteria for foods-an
update. Food Technol. 36(9):45-54, 92.
Representative terms from entire chapter:
microbiological control
