methods of food preservation intro to agriculture aaec – paradise valley spring 2015
TRANSCRIPT
Methods of Food Preservation
Intro to Agriculture AAEC – Paradise Valley Spring 2015
What is Food Preservation?
Food preservation is used to keep food from spoiling
Effects of Spoilage
Food becomes unsafe to eat
Taste, smell, color, and consistency may change
Causes of Spoilage Microbes: bacteria and other micro-
organisms Botulism, salmonella, e. coli are types of
bacterial microbes Molds (on breads or cheese) are fungi-
caused spoilage Chemicals- i.e. pesticides, spilled fuel Insects- eat on the food material Objects- fragments of the packaging
material (glass, metal or plastic)
Preventing Spoilage Must keep food from coming into contact
with the causes of spoilage. Involves the following:
Proper storage Protection from contamination removal of moisture (to slow microbe growth and
spoilage) Use of temperature extremes (Slow or prevent
spoilage) Heating food destroys most microbes Near-freezing temperatures slow microbe
activity Below-freezing temps stop microbe growth
Methods of Food Preservation Methods must retain flavor and identity
Methods include: 1. Refrigeration 2. Freezing 3. Canning 4. Pasteurization 5. Irradiation 6. Aseptic Packaging 7. Drying 8. Salting 9. Fermenting10. Pickling
Refrigeration Short term method Spoilage is slowed Used with fresh
fruits, vegetables, dairy products and meats
Most refrigeration is between 36-40 degrees F
Freezing Causes the water in foods to freeze Temperatures should be -30 degrees Works well with vegetables and
meats (proper preparation helps foods to retain natural color and flavor)
Canning Placing the food into a container,
heating to kill any microbes, and then sealing
Canned goods last up to a few years Used with many vegetables and a few
years
Pasteurization Most widely used with milk and fruit juice Involves heating the food and holding it at
a set temp. long enough to kill any microbes present
Ultrahigh-temperature pasteurization (UHTP) now being used with some milk – allows milk to be stored at room temp. for a few weeks
Irradiation Use of radiation to kill microbes in the
food Used only on a few foods Gaining acceptance as a method to
prevent spoilage
Aseptic Packaging Involves sterilizing the food and its packaging New method of preservation Often used with meats
Drying Most likely the oldest method of food
preservation Attempts to remove all traces of moisture so
that microbes cannot live Modern methods include freeze-drying Food that can be dehydrated include
Meats Vegetables Fruits Milk
Salting Use large amounts of salt to remove moisture
from foods Disadvantages
High concentration of salt in food leads to health problems
Palatability of salted foods is poor
Fermenting/Pickling Pickling
Involves changing the pH below the level of microbes- usually less than 4.2-4.8
Pickling uses vinegar (acetic acid) to lower the pH, and salt (to dehydrate the microbes)
Fermentation Involves the conversion of complex sugars into
simple compounds Uses certain yeasts and beneficial microbes to
secrete Enzymes and start the fermented process
Food that are fermented or pickled include : wines (F) bread (F) cheese (F) Sauerkraut (F) Pickles (p)