preservation by heat process principles of food preservation

1. Food Preservation
Practical
Assignment

2. Subject: industrial methods of food
preservation
Topic: preservation by heat process
 Principles of heat preservation
 Pasteurization and sterilization
By Maher Fatima
Pasteurization:

3. Pasteurizationisthe processofheating food, specificallyliquids, toa specific
temperature to slow microbial growth in the food. Pasteurization requires
rapidlyheating theliquid toa specific temperature
for a specified time, followed by rapid cooling and
thensealing. Thisprocesskills the heat susceptible
organisms and their spores. When pasteurizing a
liquid, thesaid liquid isheated tobelow theboiling
temperatureandthenrapidlycooled. For example,
milk would be heated at the temperature of 145°F
(63°C) for 30 minutes. Therearetwotypesofheating processesused for milk
under pasteurization: High-temperature, short-time(HTST) and Ultra-high
temperatureprocessing(UHT). InHTST, milkispassed through metalpipes
that is surrounded by hot water and heated to 72°C (161°F) for 15 seconds.
The milk is then cooled and sealed. In UHT, milk is maintained at a
temperature of 138°C (280°F) for a minimum of two seconds. UHT allows
milks to last longer, approximately two to three months.
Sterilization:
Sterilization refersto the processof eliminatingall
forms of bacteriafrom any product. Sterilizationis
not limited toonly liquidsbut canalsorefer tosolid
surfaces, fluids, medications, etc. The process of
sterilization kills all forms of microbial life,
including fungi, spores, viruses and bacteria.
Sterilizationisdoneusing variousmethodssuch as
applying heat, irradiation, chemicals and applying high pressure. Appert
would cookfood to a high temperature, coolit and thensealed thefood in air
tight bottles that allowed the food to be preserved for long periods of time
without spoiling. This process was later adapted for canned foods. In order
to sterilize milk, it would be heated to a high temperaturethat would kill all
the bacteria present in the milk. Once all the bacteria are killed, the milk is
then sealed in air tight containersand cartons. Sterilizationallowsfood and
liquids to be preserved for long periods of time.

4. Principles of Food Preservation:
Prevention or delay of microbial decomposition.
1. By keeping out microorganisms – asepsis
Asepsis isthe stateof being free from disease-causingmicro-organisms
(such as pathogenic bacteria, viruses, pathogenic fungi, and parasites).
2. By removal of microorganisms – filtration
Removal of microorganismsisnot veryeffectivein food preservation, but
under special conditions it may be helpful in reducing the number of
microorganisms. Removal may be accomplished by means of
centrifugation, filtration, trimming, cleaning, and washing.
3. By hindering the growth and activity of
microorganisms - low temperature, drying.
Drying inhibits the growth of bacteria, yeasts, and mold through the
removal of water.
4. By killing the microorganisms - heat or radiation.
Improves the safety and extends the shelf life of foods by reducing or
eliminating microorganisms and insects. Like pasteurizing milk and
canning fruits and vegetables.
 How to kill Microbes?

5. High Pressure Processing:
A method of preserving food that involves food to intense pressures to kill
microbes, such as yeasts, bacteria and moulds, while maintaining the fresh
qualities of the food.