i
intRoDUCtion to
MiCRoBeS in FooDS
Microorganisms are living entities of microscopic size and include bacteria, viruses, yeasts and
molds (together designated as fungi), algae, and protozoa. For a long time, bacteria have been classified as prokaryotes (cells without definite nuclei) and the fungi, algae, and protozoa as eukaryotes
(cells with nuclei); viruses do not have regular cell structures and are classified separately. In the
1990s, this classification changed and will be briefly mentioned in Chapter 2. Microorganisms
are present everywhere on Earth, including in humans, animals, plants and other living creatures,
soil, water, and the atmosphere, and they can multiply everywhere except in the atmosphere.
Together, their numbers far exceed all other living cells on this planet. They were the first living
cells to inhabit the Earth more than 3 billion years ago and since then have played important roles,
many of which are beneficial to other living systems.
Among the microorganisms, some molds, yeasts, bacteria, and viruses play both desirable
and undesirable roles in our food. In this section, the importance of microorganisms in food, the
predominant microorganisms associated with food, sources from which they get into the food,
and the microbiological quality of food under normal conditions are presented in the following
chapters:
Chapter 1: History and Development of Food Microbiology
Chapter 2: Characteristics of Predominant Microorganisms in Food
Chapter 3: Sources of Microorganisms in Food
Chapter 4: Normal Microbiological Quality of Foods and Its Significance
intRoDUCtion to
MiCRoBeS in FooDS
Microorganisms are living entities of microscopic size and include bacteria, viruses, yeasts and
molds (together designated as fungi), algae, and protozoa. For a long time, bacteria have been classified as prokaryotes (cells without definite nuclei) and the fungi, algae, and protozoa as eukaryotes
(cells with nuclei); viruses do not have regular cell structures and are classified separately. In the
1990s, this classification changed and will be briefly mentioned in Chapter 2. Microorganisms
are present everywhere on Earth, including in humans, animals, plants and other living creatures,
soil, water, and the atmosphere, and they can multiply everywhere except in the atmosphere.
Together, their numbers far exceed all other living cells on this planet. They were the first living
cells to inhabit the Earth more than 3 billion years ago and since then have played important roles,
many of which are beneficial to other living systems.
Among the microorganisms, some molds, yeasts, bacteria, and viruses play both desirable
and undesirable roles in our food. In this section, the importance of microorganisms in food, the
predominant microorganisms associated with food, sources from which they get into the food,
and the microbiological quality of food under normal conditions are presented in the following
chapters:
Chapter 1: History and Development of Food Microbiology
Chapter 2: Characteristics of Predominant Microorganisms in Food
Chapter 3: Sources of Microorganisms in Food
Chapter 4: Normal Microbiological Quality of Foods and Its Significance