Factors Influencing Microbial Growth in Food ◾ 71
excessive microbial growth rendering food undesirable for consumption (see Chapter 19). Foods
of animal origin are rich in protein, which is degraded by proteolytic enzymes produced by pseudomonads, Enterobactericeae, and lactic acid bacteria, rendering spoiled food. Small molecules,
such as glucose, lactate, and free amino acids, regulate growth of these microorganisms in these
foods. Spoilage of fruits and vegetables depends on the pectinolytic activity (enzymes involved
are pectin lyases, pectate lyase, polygalacturonase, pectin methylesterage) of members of the
Pseudomonadaceae and Enterobactericeae families resulting in enzymatic browning, off-flavor, and
texture breakdown. Production of these enzymes is regulated by QS; thus chemicals (i.e., garlicextract plant-derived p-coumaric acid) that inhibit QS can be used to control bacterial growth in
foods. Another strategy to control pathogen or spoilage bacterial growth in food would be to add
QS compounds in foods to create a false sense indicating there are already too many bacteria present in food; thus growth can be ceased. 12
Conclusion
The physical and chemical environments control microbial growth within the growth range
mainly by influencing their metabolic process associated with synthesis of energy and cellular
components. Beyond the growth range, these factors, either individually or in combination, can
be used to control microbial growth and even to destroy them. Actual growth is accomplished
through the metabolism of various nutrients present in a food. The processes by which the food
nutrients are transported inside the microbial cells and then metabolized to produce energy, cellular molecules, and byproducts are briefly discussed in Chapter 8.
Adaptation
survival
Sporulation
Biofilm formation
Autoinducer
(AI)
Bacteria
Virulence gene
expression
N-acyl homoserine lactone
N
O
O
H
R
Spoiled
bell pepper
Figure 6.2 (See color insert.) Bacterial quorum sensing network and adaptation strategy on
food. Bacteria secrete an autoinducer (Ai), such as N-acyl homoserine lactone, to communicate
with others in response to a changing food environment.
excessive microbial growth rendering food undesirable for consumption (see Chapter 19). Foods
of animal origin are rich in protein, which is degraded by proteolytic enzymes produced by pseudomonads, Enterobactericeae, and lactic acid bacteria, rendering spoiled food. Small molecules,
such as glucose, lactate, and free amino acids, regulate growth of these microorganisms in these
foods. Spoilage of fruits and vegetables depends on the pectinolytic activity (enzymes involved
are pectin lyases, pectate lyase, polygalacturonase, pectin methylesterage) of members of the
Pseudomonadaceae and Enterobactericeae families resulting in enzymatic browning, off-flavor, and
texture breakdown. Production of these enzymes is regulated by QS; thus chemicals (i.e., garlicextract plant-derived p-coumaric acid) that inhibit QS can be used to control bacterial growth in
foods. Another strategy to control pathogen or spoilage bacterial growth in food would be to add
QS compounds in foods to create a false sense indicating there are already too many bacteria present in food; thus growth can be ceased. 12
Conclusion
The physical and chemical environments control microbial growth within the growth range
mainly by influencing their metabolic process associated with synthesis of energy and cellular
components. Beyond the growth range, these factors, either individually or in combination, can
be used to control microbial growth and even to destroy them. Actual growth is accomplished
through the metabolism of various nutrients present in a food. The processes by which the food
nutrients are transported inside the microbial cells and then metabolized to produce energy, cellular molecules, and byproducts are briefly discussed in Chapter 8.
Adaptation
survival
Sporulation
Biofilm formation
Autoinducer
(AI)
Bacteria
Virulence gene
expression
N-acyl homoserine lactone
N
O
O
H
R
Spoiled
bell pepper
Figure 6.2 (See color insert.) Bacterial quorum sensing network and adaptation strategy on
food. Bacteria secrete an autoinducer (Ai), such as N-acyl homoserine lactone, to communicate
with others in response to a changing food environment.