Preservation
The key principles for the preservation of food are to slow down the multiplication of bacteria or kill it
completely. Some food preservation techniques such as pasteurization destroy foods enzymes that cause
food discoloration.
With food being an intrigue part of human existence the preservation of food is one of the oldest
technologies used by man whether it is ancient man drying meat or the Chinese fermenting vegetables 5000
years ago. Below is a list and summary on each of the preservation methods used today. There is also the
opportunity for you to complete your own summary including a substantial written response.
 Refrigeration and freezing
 Canning
 Dehydration
 Freeze-drying
 Salting
 Pickling
 Pasteurizing
 Fermentation
 Chemical preservation
Refrigeration and Freezing
 Refrigeration and freezing are the world’s most popular form of food preservation in use.
Refrigeration works through the slowing of bacterial growth by slowing bacterial growth food items
shelve life can be extended from a few hours to between 6-9 days depending on the food item. The
principles behind freezing are to stop bacterial growth altogether through the reduction in
temperature the bacteria in food become inactive. It is important to note that this only makes the
bacteria inactive while frozen and when food is defrosted bacteria become active once again.
 Refrigeration and freezing has very minimal effects on the taste and texture of food items such as
meat, seafood, fruits and vegetables however without proper preparation most fruit items are
unsuitable for freezing as the fruits structure expands reducing its capacity to retain it natural form
causing it to become mushy when defrosted reducing it appearance and texture.
Canning
 Canning in general is one of the oldest methods of preservation. You are said to be canning when
food items that have be sterilized through boiling are sealed in a container. The boiling process can
take place either in the can or before it is place in the can and sealed preventing any bacterial growth.
With the food items now being sterile they will remain safe for consumption until opened exposing
the bacteria to oxygen which will enable the bacteria to start to multiply again. Hence the notice on
most canned items to “refrigerate after opening”.
 In general we think of “cans” as being metal however they can be any suitable sealable container
such as glass jars for preserves and jams or through the use of technology we can now seal liquids or
solids in foil and plastic containers such as milk and soups through the sterilizing process of UHT
Ultra high temperature pasteurization.
 Refrigeration and freezing are the preferred methods of preservation over canning as the process
adversely alters the taste, appearance and texture of the item.
Dehydration
 Dehydration or drying food items through the removal of liquid has been used for over 5000 years.
Preservation through drying is the process of removing liquid either by natural air hung or sun dried,
or commercial versions including conventional heat drying, vacuum drying, osmotic or freeze
drying.
 Food preservation technology of dehydration has enabled society to move beyond just canning food
items. With dehydration and now freeze drying, complete meals are now able to be prepared with
only water such items include mash potato, soups and pasta dishes. This has even wider
ramifications on the world’s population with developing countries having access to items such as
powdered milk and baby formulas. Combined with clean drinking water the health benefits of these
products are significant in developing countries and aid in convenience in developed countries.
Freeze drying
 Freeze-drying is the form of drying that removes all moisture from the food items in which the
frozen ice is sublimated into vapor. This has a positive effect on the food items taste when rehydrated
with freeze dried products tasting closer to the original item then normal methods of hydration.
 Freeze drying is most commonly used in the production of instant coffee fruit items and dairy
products including infant formulas.
Salting and Pickling
 Salting and pickling are ancient preservation techniques. The salt aids in drawing out moisture
creating an environment inhospitable to bacteria. If salted in cold weather slowing bacterial growth
while the moisture is removed salted meat can last for years this process is referred to as pickling.
Pasteurizing
 Using the internet research and list the steps in the process of pasteurization.
Fermentation
 Using the resource from:
Burnett-Fell, B., Ferrie, S., Wootton, M., Dengate, H., Evans, K., Baines, S., et al. (2009). Food
technology in action. Milton: John Wiley & Sons Australia Ltd.
Research fermentation and anyalising the chemical alteration during this process and what inpact this
has on the preservation of the food item.
Chemical preservation
 Write a substantial response on chemical preservation including the use of Irradiation, Pascalization
and Ozonation preservation methods.
Preservation Principle
Dehydration of moisture
Increasing temperature
Decreased temperature
Cryvac
Chemical preservation
Irradiation
Effect on bacteria
Preservation technique
Bibliography
Burnett-Fell, B., Ferrie, S., Wootton, M., Dengate, H., Evans, K., Baines, S., et al. (2009). Food technology
in action. Milton: John Wiley & Sons Australia Ltd.