Fundamental Food Microbiology, Third Edition - Fuad Fathir

CONTROL BY ANTIMICROBIAL PRESERVATIVES 499
others have not been used directly as preservatives. Although many of them have
been unknowingly consumed through foods without any adverse effects (such as
bacteriocins of many lactic acid bacteria), they probably have to be tested for safety
and regulatory approval before use in foods.
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II. OBJECTIVES
Antimicrobial chemicals are used in food in relatively small doses either to kill
undesirable microorganisms or to prevent or retard their growth. They differ greatly
in the abilities to act against different microorganisms (broad spectrum). Some are
effective against many microorganisms, whereas others are effective against either
molds and yeasts or only bacteria (narrow spectrum). Similarly, some compounds
are effective against either Gram-positive or Gram-negative bacteria, or bacterial
spores, or viruses. Those capable of killing microorganisms are designated as germicides
(kill all types), fungicides, bactericides, sporicides, and viricides, depending
on their specificity of killing actions against specific groups. Those that inhibit or
retard microbial growth are classified as fungistatic or bacteriostatic. However, under
the conditions in which most antimicrobials are used in foods, they cannot completely
kill all the microorganisms or prevent their growth for a long time during
storage. They can also cause injury.
III. INFLUENCING FACTORS
Several factors need to be considered in evaluating the suitability of an antimicrobial
agent as a food preservative, 1–5 based on their antimicrobial properties,
suitability for application in a food, and ability to meet regulatory requirements. As
regards antimicrobial properties, a compound that kills (-cidal) instead of controlling
growth (-static) is preferred. Similarly, a compound with a broader antimicrobial
spectrum is more suitable for application in foods so that it is effective against many
types of microorganisms important in foods (namely, molds, yeasts, bacteria, and
viruses), as compared with one that has a narrow spectrum. Also, a compound
effective not only against vegetative cells but also against spores is preferred. Finally,
it should not allow development of resistant strains. Most compounds do not meet
all these requirements. Many times, more than one compound is used in combination
to increase the inhibitory spectrum. In addition, food environments may restrict
growth of many types of microorganisms. Under such circumstances, a preservative
that can effectively control the growth of the microorganisms of concern can be used
alone.
To be suitable for application in a food, a compound should not only have the
desired antimicrobial property but also not affect the normal quality of a food
(texture, flavor, or color). It should not interact with food constituents and become
inactive. It should have a high antimicrobial property at the pH, A w, Eh, and storage
temperature of the food. It should be stable during the storage life of the food.
Finally, it should be economical and readily available.