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Chapter 6
Factors influencing
Microbial Growth in Food
introduction
The ability of microorganisms (except viruses) to grow or multiply in a food is determined by
the food environment as well as the environment in which the food is stored, designated as the
intrinsic and extrinsic environments of food, respectively. It is not possible to study the influence
of any one factor on growth independently as the factors are interrelated. Instead, the influence
of any one factor on different levels of growth is compared keeping other factors unchanged. The
influence of these factors is discussed here.
intrinsic Factors or Food environment
The intrinsic factors of a food include nutrients, growth factors, inhibitors (or antimicrobials),
water activity, pH, and oxidation–reduction potential. The influence of each factor on growth is
discussed separately. But, as indicated previously, in a food system, the factors are present together
and exert effects on microbial growth in combination, either favorably or adversely.
Nutrients and Growth
Microbial growth is accomplished through the synthesis of cellular components and energy. 1 The
necessary nutrients for this process are derived from the immediate environment of a microbial
cell and, if the cell is growing in a food, receives its nutrients from the food. These nutrients
include carbohydrates, proteins, lipids, minerals, and vitamins. Water is not considered a nutrient,
but it is essential as a medium for the biochemical reactions necessary for the synthesis of cell mass
and energy. All foods contain these five major nutrient groups, either naturally or added, and the
amount of each nutrient varies greatly with the type of food. 2 In general, meat and fish are rich
in proteins, lipids, minerals, and vitamins but poor in carbohydrates. Foods from plant sources
Chapter 6
Factors influencing
Microbial Growth in Food
introduction
The ability of microorganisms (except viruses) to grow or multiply in a food is determined by
the food environment as well as the environment in which the food is stored, designated as the
intrinsic and extrinsic environments of food, respectively. It is not possible to study the influence
of any one factor on growth independently as the factors are interrelated. Instead, the influence
of any one factor on different levels of growth is compared keeping other factors unchanged. The
influence of these factors is discussed here.
intrinsic Factors or Food environment
The intrinsic factors of a food include nutrients, growth factors, inhibitors (or antimicrobials),
water activity, pH, and oxidation–reduction potential. The influence of each factor on growth is
discussed separately. But, as indicated previously, in a food system, the factors are present together
and exert effects on microbial growth in combination, either favorably or adversely.
Nutrients and Growth
Microbial growth is accomplished through the synthesis of cellular components and energy. 1 The
necessary nutrients for this process are derived from the immediate environment of a microbial
cell and, if the cell is growing in a food, receives its nutrients from the food. These nutrients
include carbohydrates, proteins, lipids, minerals, and vitamins. Water is not considered a nutrient,
but it is essential as a medium for the biochemical reactions necessary for the synthesis of cell mass
and energy. All foods contain these five major nutrient groups, either naturally or added, and the
amount of each nutrient varies greatly with the type of food. 2 In general, meat and fish are rich
in proteins, lipids, minerals, and vitamins but poor in carbohydrates. Foods from plant sources