The microbiological effects of different processing factors applied in the
food industry will be discussed as they arise elsewhere in the text,
principally in Chapter 4.
Although it is often convenient to examine the factors affecting
microbial growth individually, some interact strongly, as in the relation-
ships between relative humidity and water activity aw, and gaseous
atmosphere and redox potential. For this reason, in the following
discussion, we have not been over zealous in discussing individual factors
in complete isolation.
3.2 Intrinsic Factors (Substrate Limitations)
3.2.1 Nutrient Content
Like us, micro-organisms can use foods as a source of nutrients and
energy. From them, they derive the chemical elements that constitute
microbial biomass, those molecules essential for growth that the organ-
ism cannot synthesize, and a substrate that can be used as an energy
source. The widespread use of food products such as meat or casein
digests (peptone and tryptone), meat infusions, tomato juice, malt
Table 3.1 Factors affecting the development of microbial associations in food
Intrinsic Factors
Nutrients
pH and buffering capacity
Redox potential
Water activity
Antimicrobial constituents
Antimicrobial structures
Environmental factors
Relative humidity
Temperature
Gaseous atmosphere
Implicit factors
Specific growth rate
Mutualism
Antagonism
Commensalism
Processing factors
Slicing
Washing
Packing
Irradiation
Pasteurization
Chapter 3 23