Food Preservation
Kaltham Al-Kuwari
Science
7D
Two basic ideas behind Food
Preservation
The basic idea behind food preservation is usually either of these
two:
- To slow down the activity of disease-causing bacteria
or
- To kill the bacteria all together
5 different ways food can be preserved
By keeping food at low
temperature:
Refrigeration and
Freezing are probably
the most popular forms
in food preservation
today.
In refrigeration, the
bacterial action on the
food is slowed down; it
takes a week or two to
spoil.
In freezing, bacterial
action on the food is
stopped. Bacteria are
completely inactive if
frozen.
1
By Drying:
Dehydration is one of the
5 ways you can
preserve the food.
Dried fruits, potatoes in a
box, dried vegetables,
powdered milk, pasta,
powdered soups,
powdered sauces, and
powdered meat you see
in the grocery store are
dehydrated products.
When foods are dried,
bacteria will become
inactive.
2
3
By adding substances called preservatives:
Substances that are used for preserving food are called preservatives.
Sugar, salt, spices, saltpeter, and vinegar are examples of
preservatives.
- Salting is an old preservation technique. The food covered by salt
does not spoil because bacteria cannot thrive in salty environment.
Salt makes the moisture in food is also drawn out by salt. Anything
that’s salted will post probably last for a year.
- Pickling has been used in the past to preserve meat, fruits and
vegetables. Today, it is used to make pickles. Preservative qualities
of vinegar and salt are combined to produce pickles, they inhibit the
growth of bacteria.
4
By Sterilization:
It is a good idea to heat up
the food because heat is a
good way to kill bacteria
and preserve the food.
When that is done, it is
called sterilization.
Canned goods are most often
preserved foods in jars
that have been sterilized.
5
By excluding air:
Foods kept in places where air
can’t reach them are more
likely to last long. It’s
lasting long by excluding
air.
Canning is one of the famous
examples of excluding air.
Many foods can be canned.
The Canning process has
been used since 1825. The
food in the can must be
boiled to kill the bacteria
and the can must be sealed.
When the food is in the can,
it doesn’t spoil because it is
completely free from living
germs.
Preservation Effects
Permitted less nomadic travels.
Communities, civilizations established.
Expeditions were extended in time and routes.
Increasing populations had better supplies of
foods.
Helped eliminate food borne diseases,
Supplies could last throughout seasons,
extending life expectancies.
Preservation Methods
Five main ways to preserve foods and remove
microorganisms:
– Chemicals
– Drying
– Refrigeration
– Canning
– Radiation
The last three methods are current practices, developed and
modified in the last two centuries.
Early Methods
The early methods of brewing, baking, and winemaking created
products that allowed trades and commerce.
Storage of grains added tetracycline to the diets, which probably helped
resist many diseases and infections.
The preserved products also introduced proteins and vitamins into the
diets.
Pompeii- jars of fruit preserved in honey.
Rome- first preserved ham
Vikings laid fish in the riggings of their ships to let sea wind dry their
fish.
Early North American Indians - pemmican
– Remove fat, cook meat, then grind fat and meat into a paste.
– Prevented deterioration.
– Important for fur traders during the 17th , 18th , 19th centuries.
New stoneware developed during the 16th centuries
– Could stand high temperatures 1200-1400°C
Food Preservation Shift
During the 17th and 18th centuries, new ingredients were
being created.
Imported spices and sugars increased the variety of foods.
The 18th century created a shift in food preservation from
a necessity for survival to a desire for delicacies.
1735- botulism first recognized (from sausage use)
Food preservation methods used were not effective
enough for long term use.
Better methods were needed for safer food consumption.
Switch from primitive methods used to flavor foods to
newer scientific techniques that removed life from
food.
Preservation Today
Freeze-drying used for military and space
expeditions.
– Foods subjected to high pressures
– Expensive but highly effective.
Radiation used frequently
HTST – (High Temperature Short Time
process)
New food borne pathogens being discovered.
Greater need for safer home and commercial
preservation methods.
Clostridium botulinum – most famous
microorganism in food industry.
Listeria monocytogenes – recent pathogen
Many domestic processes:
- Canning
- Freezing
- Blanching
Or
Preserving with sugars:
- Jams, jellies, preserves,
marmalades, butters
or
Oven or sun drying
BIBLIOGRAPHY
http://science.howstuffworks.com/innovation/edible-innovations/food-preservation.htm
http://static.ddmcdn.com/gif/food-preservation-ch.jpg
http://www.whatscookinglehighvalley.com/wp-content/uploads/2011/11/18_4_orig.jpg
http://beth811.hubpages.com/hub/Process-Methods-in-Preserving-Foods
http://salestores.com/stores/images/images_747/T12G.jpg
http://schoolworkhelper.net/wp-content/uploads/2011/08/food-preservation-freezing.jpg
http://www.magazine.ayurvediccure.com/wp-content/uploads/2008/12/dryfruits.gif
http://sp.life123.com/bm.pix/introduction-to-the-home-canning-process-1_jars-withpreserves.s600x600.jpg
 THANK YOU 
 KALTHAM AL-KUWARI 