Pasteurization,as noted in Chapter 1, uses heat to kill pathogens and reduce
the number of food spoilage microorganisms in foods and beverages. Examples
are pasteurized milk and juice.
Sanitationis the treatment to remove or lower microbial counts on objects
such as eating and drinking utensils to meet public health standards. This is usu-
ally accomplished by washing the utensils in high temperatures or scalding
water and disinfectant baths. Bacterostatic, fungistatic, and virustastic agents—
or any word with the suffix -static or -stasis—indicate the inhibition of a partic-
ular type of microorganism. These are unlike bactericides or fungicides that kill
or destroy the organism. Germistatic agents include refrigeration, freezing, and
some chemicals.
Microbial Death Rates
Microbial deathis the term used to describe the permanent loss of a microor-
ganism’s ability to reproduce under normal environmental conditions. A tech-
nique for the evaluation of an antimicrobial agent is to calculate the microbial
deathrate. When populations of particular organisms are treated with heat or
antimicrobial chemicals, they usually die at a constant rate.
The effectiveness of antimicrobial treatments is influenced by the number of
microbes that are present. The larger the population, the longer it takes to destroy
it. The different variations of certain microorganisms influence death rate because,
for example, endospores are difficult to kill.
Environmental influences, such as the presence of blood, saliva, or fecal mat-
ter, inhibits the action of chemical antimicrobials. Time of exposure to heat or
radiation is also important. Many chemical antimicrobials need longer exposure
times to be effective in the death of more resistant microorganisms or endospores.
Action of Antimicrobial Agents
There are two categories that chemical and physical antimicrobial agents fall
into: those that affect the cell walls or cytoplasmic membranes of the microor-
ganism and those that affect cellular metabolism and reproduction. As stated in
Chapter 4, the cell wall is located outside the microorganism’s plasma mem-
CHAPTER 6 Microbial Growth and Controlling It^113