LPT 321: Meat Science (1+1)

PRINCIPLES OF FOOD PRESERVATION

• Food may be preserved by adopting any of the following measures:
• Preservation or delay of microbial decomposition
  • By keeping out microorganisms (asepsis)
  • By removal of microorganisms e.g. by filtration.
  • By hindering the growth and activity of microorganisms e.g. by low temperature, drying, anaerobic conditions or chemicals.
  • By killing the microorganisms e.g. by heating or irradiation.
• Preservation or delay of self-decomposition of the food
  • By destruction or inactivation of food enzymes e.g. by blanching.
  • By prevention or delay or purely chemical reactions e.g. prevention of oxidation by means of an antioxidant.
• Prevention of damage because of insects, animals, mechanical causes, etc.
  • The methods used to control the activities of the microorganisms usually are effective against enzymatic activity in the food or chemical reactions.
  • Methods like drying or use of low temperature, however, permit auto decomposition to continue unless special precautions are taken.
  • For example, most vegetables are blanched (heated) to inactivate their enzymes before being frozen.

Delay of microbial decomposition

• Most of the commonly employed methods of food preservation depend not on the destruction or removal of microorganisms, but rather on delay in the initiation of growth and hindrance to growth, once it has begun.
• The main factors of importance for bacterial growth in or on meat are the temperature, relative humidity, water activity, oxygen availability and the pH of the microbial environment.

Growth curve of microorganisms

Generation time

• It is the time that elapses between the formation of a daughter cell and its division into two new cells.
• The generation time shorten as conditions become more favorable and lengthen, as they become less favorable.