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Chapter 4
normal Microbiological
Quality of Foods and
its Significance
introduction
Although many types (genera, species, strains) of microorganisms are present in nature, under
normal conditions, a food generally harbors only a few types. These types include those that are
naturally present in raw foods (which provide the ecological niche) and those that enter from outside sources to which the foods are exposed from the time of production until consumption. The
relative numbers (population level) of a specific type of microorganism initially present (without
growth) in a food depend on the intrinsic and extrinsic conditions to which the food is exposed.
If growth occurs, the predominant types will be the ones for which the optimum growth condition is present in the food. This aspect is discussed in Chapter 6. The objective of this chapter
is to develop an understanding of the microbial types (and their levels where possible) that can
be expected under normal conditions in different food groups. It has to be recognized that the
microbial load in a food results from initial contamination from different sources and growth of
the contaminants before testing; normally, it is difficult to separate the two.
Raw and Ready-to-eat Meat Products
Following slaughter and dressing, the carcasses of animals and birds contain many types of microorganisms, predominantly bacteria, coming from the skin, hair, feathers, gastrointestinal tract,
and so forth; the environment of the feedlot and pasture (feed, water, soil, and manure); and the
environment at the slaughtering facilities (equipment, air, water, and humans). Normally, carcasses
contain an average of 10 1–3 bacterial cells/in 2 . Different enteric pathogens, Salmonella, Yersinia
enterocolitica, Campylobacter jejuni, Escherichia coli, Clostridium perfringens, and Staphylococcus
aureus, both from animals or birds and humans, can be present, but normally at a low level.
Chapter 4
normal Microbiological
Quality of Foods and
its Significance
introduction
Although many types (genera, species, strains) of microorganisms are present in nature, under
normal conditions, a food generally harbors only a few types. These types include those that are
naturally present in raw foods (which provide the ecological niche) and those that enter from outside sources to which the foods are exposed from the time of production until consumption. The
relative numbers (population level) of a specific type of microorganism initially present (without
growth) in a food depend on the intrinsic and extrinsic conditions to which the food is exposed.
If growth occurs, the predominant types will be the ones for which the optimum growth condition is present in the food. This aspect is discussed in Chapter 6. The objective of this chapter
is to develop an understanding of the microbial types (and their levels where possible) that can
be expected under normal conditions in different food groups. It has to be recognized that the
microbial load in a food results from initial contamination from different sources and growth of
the contaminants before testing; normally, it is difficult to separate the two.
Raw and Ready-to-eat Meat Products
Following slaughter and dressing, the carcasses of animals and birds contain many types of microorganisms, predominantly bacteria, coming from the skin, hair, feathers, gastrointestinal tract,
and so forth; the environment of the feedlot and pasture (feed, water, soil, and manure); and the
environment at the slaughtering facilities (equipment, air, water, and humans). Normally, carcasses
contain an average of 10 1–3 bacterial cells/in 2 . Different enteric pathogens, Salmonella, Yersinia
enterocolitica, Campylobacter jejuni, Escherichia coli, Clostridium perfringens, and Staphylococcus
aureus, both from animals or birds and humans, can be present, but normally at a low level.