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)