245
Chapter 19
important Factors in
Microbial Food Spoilage
introduction
Microbial food spoilage occurs as a consequence of either microbial growth in a food or release of
microbial extracellular and intracellular (following cell lysis) enzymes in the food environment.
Some of the detectable parameters associated with spoilage of different types of foods are changes
in color, odor, and texture; formation of slime; accumulation of gas (or foam); and accumulation
of liquid (exudate, purge). Spoilage by microbial growth occurs much faster than spoilage by
microbial extracellular or intracellular enzymes in the absence of viable microbial cells. Between
initial production (such as harvesting of plant foods and slaughtered animal foods) and final consumption, different methods are used to preserve the acceptance qualities of foods, which include
the reduction of microbial numbers and growth. Yet, microorganisms grow and cause food spoilage, which for some foods could be relatively high. It is important to understand the factors associated with microbial food spoilage, both for recognizing the cause of an incidence and developing
an effective means of control.
Sequence of events
Generally, for microbial food spoilage to occur, several events need to take place in sequence.
Microorganisms have to get into the food from one or more sources; the food environment (pH,
A W , O-R potential, nutrients, and inhibitory agents) should favor growth of one or more types of
these contaminating microorganisms; the food must be stored (or abused) at a temperature that
enables one or more types to multiply; and finally, the food must be stored under conditions of
growth for a sufficient length of time for the multiplying microbial types to attain the high numbers necessary to cause the detectable changes in a food. In a heat-treated food, the microorganisms associated with spoilage either survive the specific heat treatment (thermodurics) or get into
the food following heating (as post-heat contaminants). Spoilage of a heated food by microbial
Chapter 19
important Factors in
Microbial Food Spoilage
introduction
Microbial food spoilage occurs as a consequence of either microbial growth in a food or release of
microbial extracellular and intracellular (following cell lysis) enzymes in the food environment.
Some of the detectable parameters associated with spoilage of different types of foods are changes
in color, odor, and texture; formation of slime; accumulation of gas (or foam); and accumulation
of liquid (exudate, purge). Spoilage by microbial growth occurs much faster than spoilage by
microbial extracellular or intracellular enzymes in the absence of viable microbial cells. Between
initial production (such as harvesting of plant foods and slaughtered animal foods) and final consumption, different methods are used to preserve the acceptance qualities of foods, which include
the reduction of microbial numbers and growth. Yet, microorganisms grow and cause food spoilage, which for some foods could be relatively high. It is important to understand the factors associated with microbial food spoilage, both for recognizing the cause of an incidence and developing
an effective means of control.
Sequence of events
Generally, for microbial food spoilage to occur, several events need to take place in sequence.
Microorganisms have to get into the food from one or more sources; the food environment (pH,
A W , O-R potential, nutrients, and inhibitory agents) should favor growth of one or more types of
these contaminating microorganisms; the food must be stored (or abused) at a temperature that
enables one or more types to multiply; and finally, the food must be stored under conditions of
growth for a sufficient length of time for the multiplying microbial types to attain the high numbers necessary to cause the detectable changes in a food. In a heat-treated food, the microorganisms associated with spoilage either survive the specific heat treatment (thermodurics) or get into
the food following heating (as post-heat contaminants). Spoilage of a heated food by microbial