The basic purpose of the thermal processing of foods is to reduce or destroy microbial activity, reduce or destroy enzyme activity, and produce physical or chemical changes to make the food meet a certain quality standard. e.g. gelatinization of starch & denaturation of proteins to produce edible food.

1. BASICS OF THERMAL
PROCESSING
Submitted By-Tanya Thakur

2. INTRODUCTION
● The development of heating process started in France during the first decade
of the 1800s by Nicholas Appert, who preserved foods in sealed glass jars in
boiling water.
● The basic purpose for the thermal processing of foods is to reduce or destroy
microbial activity, and to produce physical or chemical changes to make the
food meet a certain quality standard. e.g. gelatinization of starch &
denaturation of proteins to produce edible food.
● There are a number of types of heat processing employed by the food industry
like Blanching , Pasteurisation ,Canning ,Baking ,Roasting ,Frying etc.
● There are two main temperature categories employed in thermal processing:
Pasteurization and Sterilization.

3. BLANCHING
The primary purpose of blanching is to destroy
enzyme activity in fruit and vegetables. Functions of
blanching include:
● Reducing surface microbial contamination .
● It is utilized to preserve colour, flavour and
nutritional value.
● Softening vegetable tissues to facilitate filling
into containers .
● Removing air from intercellular spaces prior to
canning.
● There are two types of blanchers:
-Steam Blanchers
-Hot Water Blanchers

4. PASTEURIZATION
● The process was named after the French
microbiologist, Louis Pasteur, whose research in
the 1860s demonstrated that thermal processing
would deactivate unwanted microorganisms in
wine.
● Pasteurization is a relatively mild heat treatment in
which food is heated to <100°C to eliminate
pathogens and extend shelf life.
● Pasteurization is used widely in the dairy industry
and other food processing industries to achieve
food preservation and food safety.

5. STERILIZATION
● The aim of sterilization is the destruction of all
bacteria including their spores.Here, the
temperature is >100°C
● Products are kept for a defined period of time at
temperature levels required for the sterilization
depending on type of product and size of container.
● After sterilization of food canning is done which
should be ‘commercially sterile’.
● In order to reach temperatures above 100°C the
thermal treatment has to be performed under
pressure in pressure cookers, also called autoclaves
or retorts.

6. CONDITIONS AFFECTING THE GROWTH
OF MICROBES
Water
Oxygen
Requirements
Temperature
pH

7. Classification Of Microbes
● WATER - most microorganisms grow well only near pure
water activity(i.e..,around 0.98-1).Thus, drying of food or
addition of high concentration of salts and sugars is the
most popular way of preventing spoilage of food.
● TEMPERATURE-
Group Min Opt. Max.
Thermophiles 40 55 75
Mesophiles 5 37 45
Psychotrophs -3 20 30

8. ● OXYGEN REQUIREMENT-
Aerobes - Can only grow in the presence of oxygen.
Anaerobes - Can only grow in the absence of oxygen.
Facultative Anaerobes - Adaptable; grows best aerobically but can grow
anaerobically.
● pH-
GROUP pH
Low acid >5.0
Medium acid 4.5-5.0
Acid 3.7-4.5
High acid <3.7

9. CONCLUSION
● Thermal processing of foods is to reduce or destroy microbial
activity, and to produce physical or chemical changes to
make the food meet a certain quality standard.
● There are two main temperature categories employed in
thermal processing: Pasteurization and Sterilization.
● Conditions affecting the growth of microbes are
water,temperature, oxygen requirement ,pH .

10. THANK YOU