This document provides an overview of food processing and preservation. It discusses why foods are preserved, common preservation methods like canning, drying, salting, and freezing. It also explains key unit operations in food processing like blanching, pasteurization, chilling, and freezing. The document aims to introduce students to the basic concepts and principles of food processing and preservation.

1. Food Processing and Preservation
Course No: FET 227
Presented By
Mohammad Afzal Hossain,
Faculty,
Dept. of Food Engineering and Tea Technology

3. Introduction
I want eat a mango in
winter season? Is it
possible? Why not ! it is possible

4. Food Preservation Introduction
How it is possible?
I will tell you how it is
possible

5. You know that mango cold
drinks available in all
season
Some food like
mango pickle is also
available throughout
the year.

6. How does it not spoil when
stored for much time?

7. Do You know that how the
food is Preserved?

8. Food Preservation
Food Preservation is a process in which
Food and vegetables are prevented from getting
spoilt
The color, test, and nutritive values of food is also
preserved
Food products lasts for a long period of time:
Shelf life of food product is increased

9. So, we can defined Food
Preservation as:
Retaining food over a period of time without
being contaminated by pathogenic organisms
or chemicals and without losing its colour,
texture, flavour and nutritious value.
Food Preservation usually involves preventing
the growth of bacteria, fungi and other
microorganisms, as well as retarding the
oxidation of fats which causes rancidity.

10. Why to preserve foods?
Why should we preserve
foods? I will explain it

11. Types of foods
Food Types
Perishable Semi Perishable Shelf Stable
Fruits Milk Cheese, Some
ready foods
Grains

12. Food types
 Perishable
- Lasts for less time 2 days to 1 week
- Example: Fruits, milk, vegetables, meat
 Semi perishable
- Lasts for around 2 months and are processed
- Example: Ice-cream, cheese, bread, cake, pastries
 Shelf Stable
- Has longer shelf Life more than 6 months
- Example: Food grains

13. Why to preserve food?
If we are able to preserve foods, we enjoy
any kind of foods in any season
We eat food even it is not
available in our areas
We can store our food easily and
without worries

14. Explanation of previous slide
We enjoy any kind of food in any season and different
types. Such as
 Mango juice
 Mango pulp
 Mango pickle
 Raw mango powder etc

15. Principles of Food Preservation
1. Inhibit the growth and activity of Microorganisms
-Asepsis(to keep out microorganisms)
-Removal of microorganisms
-Stopping the growth and activity of microorganisms
(low temperatures, drying or chemicals)
-Destruction of MO(heating or radiation)

16. Principles of Food Preservation(contd.)
2. Protecting against self decomposition of food
-Inhibit the activity of Endogenous Enzyme
(Phenolase)
-Delay or inhibit chemical reactions(Non-enzymatic
browning)
3. Protection from invasion and spoilage by insects and
rodents
4. Protection against losses by mechanical causes

17. Importance of Food Preservation:
Important and vital in the Food industry due to a
number of -
social,
psychological, and
health factors
 Increases the shelf life of food
 Retain the quality of food – colour, texture, flavour
& nutritional value
 Increases food supply
 Adds variety to the food
 Decreases wastage of food
 Make foods available throughout the year

18. Food Preservation Methods
 Preservation methods vary according to
--------the food items, and
--------quantity of the items to be preserved
Principles of Food preservation can be broadly
classified into two types:
1) Bactericidal methods
2) Bacteriostatic methods

19. Bactericidal methods:
Most of the microorganisms are killed
Examples are-
o cooking,
o canning,
o pasteurization,
o sterilization,
o irradiation etc.

20. Bacteriostatic Methods:
Based on prevention of multiplication of
microorganisms
May be achieved by
----removal of water
----use of acids, oils or spices
----keeping the foodstuff in low temperature
Methods based on this principles are
----Drying,
----freezing,
----pickling,
----salting, and
----smoking.

21. Techniques of Food Preservation
 Physical
 Chemical
Physical
--freezing and canning(rely on killing
the microorganisms or at least stopping
the their growth for long enough)
--drying, gamma irradiation, exposure to
ultraviolet or high intensity white light,
ultra high pressure and filtration

22. Chemical
 Preservatives
 Work either as:
 Direct microbial poisons or,
 Reducing the pH to a level that prevents the growth of
MOs
#Chemicals used today are:
1. Nitrates and Nitrites
----to preserve meats
2. Sulphites
----to prevent the browning of fruits and vegetables,
----to prevent fungal spoilage

23. Common food preservation
methods:
 Bottling and canning
 Pickling
 Drying
 Salting
 Vacuum packing
 Cooling and freezing
 Waxing
 Pasteurization
 Boiling
 Smoking

24. Bottling and canning
Bottling and canning are processes of
preserving food by heating and then
sealing it in an airtight container.
The food is boiled to kill
microorganisms and then sealed to
prevent other microorganisms from
getting in.

25. Bottling Canning

26. PICKLING
Pickling food in vinegar or other acids, makes
it difficult for microorganisms to live.
Commonly pickled food include onions,
parkias, soya beans and chillies.
Sugar can also be used in pickling fruits such
as nutmegs, mangoes and cherries.

27. The concentrated sugar solution used draws
water from the fruit thus preventing the
growth of microorganisms.

28. Drying
A lot of food is preserved by drying under the
sun.
Drying removes most water from food. Most
bacteria die or become inactive when the
food is dried.

29. Anchovies and dried chillies are examples of dried
food

30. A lot of fruits such as raisins, guavas
and papayas can be eaten dried.

31. Salting
Salting is an age-old way of preserving
food. The salt draws out moisture and
prevents microorganisms from
growing. In this process, food such as
fresh fish are gutted, washed and
coarse salt is rubbed into it.

32. A lot of our local foods are
preserved by salting process.

33. Vacuum Packing
Vacuum packing keeps food by sucking
air out from its packaging.
Food is thus prevented from spoiling
because there is no air.

34. Vacuum packing is commonly used for storing
nuts, sliced fish, pickled and dried fruit.

35. Cooling and Freezing
Cooling and freezing are the most
common forms of food
preservation.

36. Cooling slows down the action of
microorganisms, thus it takes longer
to spoil. It allows fruit from different
parts of the world to appear on our
supermarket shelves.(0 to -40 C)
At freezing temperature,
microorganisms become inactive,
thus food cannot spoil when it is
frozen. (-18 0 C)

37. Food like meat, fruit and vegetables are kept in
the refrigerator.

38. Waxing
Waxing of fruit and vegetables is also common. Apples,
oranges, eggplants and tomatoes are dipped into liqiud
wax to prevent growth of fungi and loss of moisture.
Waxed fruit need to be washed thoroughly or peeled before
eating.

39. Pasteurization
Pasteurization means heating food to a
certain temperature for some time
followed by rapid cooling. Heating at
such high enough temperature kills
most bacteria. However, it does not
affect the taste and nutritional value of
the food.

40. Fresh milk, yoghurt drink and juices are
pasteurized to make them last longer.

41. Boiling
As food is heated and cooked, the heat kills the
microorganisms,
Boiling kills most bacteria. However, those not affected by
heat will grow when the conditions are suitable.
Boiling kills bacteria

42. Smoking
Smoking is the process of drying food with
smoke for a long period of time. This
method is mainly used for fish, meat and
fruit such as banana.
The drying effects of smoke and the chemicals
produced from the smoke help to preserve
the food.
Smoked banana smoked meat

43. Food Processing
 Food processing is the set of methods and techniques
used to transform raw ingredients into food or to transform
food into other forms for consumption by humans or
animals either in the home or by the food processing
industry. Food processing typically takes clean, harvested
crops or slaughtered and butchered animal products and
uses these to produce attractive, marketable and often
long-life food products. Similar process are used to produce
animal feed.

44. Food ProcessingFrom Farm To Table
?
Whey protein, a by-product
of cheese manufacturing, is
used in energy bars and drinks!

45. Aims of Food Processing
1. To extend the shelf life to allow time for distribution,
sales and home storage.
2. To increase variety in the diet by providing a range of
attractive flavours, colours, aromas and textures in food
(collectively known as eating quality, sensory
characteristics or organoleptic quality); .
3. To provide the nutrients required for health (termed
nutritional quality of a food).
4. To generate income for the manufacturing company.

46. © afzal.fet@gmail.com 46
Careers in Food Processing
 Job Titles:
 Process Engineer
 Engineer
 Employers:
 Food processors
 Ingredient
manufacturers/suppliers
 Academia (Higher Education)
 Contract research
laboratories/development
firms
 Self-employed/Consultant
 Responsibilities:
 Process design
 Bench-top process
development
 Testing
 Plant scale-up
 Commercialization
 Troubleshooting

47. Food Processing divided into:
 Unit operations combination of procedures to
achieve the intended changes to the raw materials.
 Unit operations are grouped together to form a
process. The combination and sequence of
operations determines the nature of the final
product.

48. Food Processing
 Examples of food processing methods include:
 Chopping
 Mixing
 Homogenizing
 Cooking
 Pastuerizing
 Blanching
 Spray-drying
 Frying
 Baking
 Packaging
 Addition of gas such as air entrainment for bread or
gasification of soft drinks

49. Dehydration
 Dehydration (or drying) is defined as ‘the application
of heat under controlled conditions to remove the
majority of the water normally present in a food by
evaporation’ (or in the case of freeze drying by
sublimation).
 The main purpose of dehydration is to extend the shelf
life of foods by a reduction in water activity This
inhibits microbial growth and enzyme activity, but the
processing temperature is usually insufficient to cause
their inactivation.

50. Dehydration
 Drying causes deterioration of both the eating quality and
the nutritional value of the food.
 Examples of commercially important dried foods are
coffee, milk, raisins, and other fruits, pasta, flours
(including bakery mixes), beans, nuts, breakfast cereals,
tea and spices.
 There are a large number of factors that control the
rate at which foods dry, which can be grouped into the
following categories
 processing conditions
 nature of the food
 drier design.

51. Blanching
 Blanching serves a variety of functions, one of the
main ones being to destroy enzymatic activity in
vegetables and some fruits, prior to further processing
by heat. As such, it is not intended as a sole method of
preservation but as a pre-treatment which is normally
carried out between the preparation of the raw
material and later operations (particularly heat
sterilisation, dehydration and freezing.
 Blanching is also combined with peeling and/or
cleaning of food, to achieve savings in energy
consumption, space and equipment costs

52. Blanching
 A few processed vegetables, for example onions and green
peppers, do not require blanching to prevent enzyme
activity during storage, but the majority suffer considerable
loss in quality if blanching is omitted or if they are under-
blanched.
 To achieve adequate enzyme inactivation, food is heated
rapidly to a pre-set temperature, held for a pre-set time and
then cooled rapidly to near ambient temperatures.
 The factors which influence blanching time are:
• type of fruit or vegetable
• size of the pieces of food
• blanching temperature
• method of heating.

53. Pasteurisation
 Pasteurization is a relatively mild heat treatment, in which
food is heated to below 100ºC. In low acid foods (pH>4.5,
for example milk) it is used to minimize possible health
hazards from pathogenic micro-organisms and to extend
the shelf life of foods for several days.
 In acidic foods (pH <4.5, for example bottled fruit) it is
used to extend the shelf life for several months by
destruction of spoilage micro-organisms (yeasts or moulds)
and/or enzyme inactivation

54. Canning
 A method of preserving food by killing all
microorganisms present in the food and then sealing
out air
 The food, container, and lid are heated until sterile
 As the food cools, the lid makes an airtight seal,
preventing contamination

55. Extrusion
 A process by which the form of a food is changed
 Such as changing corn to corn chips
 Not a preservation measure
 In this process, the food is heated, ground, and pushed
through various kinds of screens to yield different
shapes

56. Frying
 Frying is a unit operation which is mainly used to alter
the eating quality of a food.
 A secondary consideration is the preservative effect
that results from thermal destruction of micro-
organisms and enzymes, and a reduction in water
activity at the surface of the food (or throughout the
food, if it is fried in thin slices).
 The shelf life of fried foods is mostly determined by
the moisture content after frying: foods that retain a
moist interior (for example doughnuts, fish and
poultry products which may also be breaded or
battered), have a relatively short shelf life, owing to
moisture and oil migration during storage.

57. Irradiation
 Ionising radiation takes the form of Gama-rays
from isotopes or, commercially to a lesser extent,
from X-rays and electrons. It is permitted in 38
countries to preserve foods by destruction of
micro-organisms or inhibition of biochemical
changes.

58. The main advantages of irradiation are as follows:
 there is little or no heating of the food and therefore
negligible change to sensory characteristics
 packaged and frozen foods may be treated
 fresh foods may be preserved in a single operation, and
without the use of chemical preservatives
 energy requirements are very low
 changes in nutritional value of foods are comparable with
other methods of food preservation
 processing is automatically controlled and has low
operating costs.

59. Chilling
 Chilling is the unit operation in which the temperature
of a food is reduced to between 1ºC and 8ºC.
 It is used to reduce the rate of biochemical and
microbiological changes, and hence to extend the
shelf life of fresh and processed foods. It causes
minimal changes to sensory characteristics and
nutritional properties of foods and, as a result, chilled
foods are perceived by consumers as being
convenient, easy to prepare, high quality and
‘healthy’, ‘natural’ and ‘fresh’.

60. Chilling
 Chilling is often used in combination with other
unit operations (for example fermentation or
pasteurization) to extend the shelf life of mildly
processed foods. There is a greater preservative
effect when chilling is combined with control of
the composition of the storage atmosphere than
that found using either unit operation alone.

61. Freezing
 Freezing is the unit operation in which the
temperature of a food is reduced below its freezing
point and a proportion of the water undergoes a
change in state to form ice crystals. The
immobilization of water to ice and the resulting
concentration of dissolved solutes in unfrozen
water lower the water activity (aw) of the food
 Preservation is achieved by a combination of low
temperatures, reduced water activity and, in
some foods, pre-treatment by blanching.

62. The major groups of commercially frozen foods are as
follows:
• fruits (strawberries, oranges, raspberries) either whole or
pureed, or as juice concentrates
• vegetables (peas, green beans, sweet corn, spinach, and
potatoes)
• fish fillets and sea foods (cod, plaice, shrimps and crab
meat) including fish fingers, fish cakes or prepared dishes
with an accompanying sauce
• meats (beef, lamb, poultry) as carcasses, boxed joints or
cubes, and meat products (sausages, beefburgers, reformed
steaks)
• baked goods (bread, cakes, fruit and meat pies)
• prepared foods (pizzas, desserts, ice cream, complete meals
and cook–freeze dishes).

63. Packaging
 Food is packaged for many purposes.
 Some reasons are :
 containment for shipping, dispensing, unitizing in to
appropriate sizes, improving the usefulness,
 protect from microbial contamination, physical dirt, insect
invasion, light exposure, flavor pickup, flavor loss,
moisture pickup, moisture loss and physical abuse
 Food is packaged in metal cans, glass & plastic bottles,
paper & paper board, wide variety of plastic & metallic
films and combinations of these
 Packaging is done by continuous automatic machines at a
speed of 1000 units per min
 The container forming is dependent on the type of the food