FOOD PRESERVATION AND ITS DIFFERENT TECHNIQUES

1. KUVEMPU UNIVERSITY
Department of Biotechnology
Sahyadri Science College , Shivamogga
GUIDE:
DR.PALLAVI. M
Lecturer,
Dept. of Biotechnology
Sahyadri Science College
Shivamogga
BY:
Mohammed Faizan
I M.Sc, I Semester
Sahyadri Science College
Shivamogga
Seminar Topic : “FOOD PRESERVATION TECHNIQUES”

2. CONTENTS
INTRODUCTION
DEFINITION
FOOD PRESERVATION TECHNIQUES
1.DEHYDRATION(DRYING OR DESICCATION)
2.USE OF CHEMICAL PRESERVATIVE& ADDITIVE.
3.PRESERVATION BY USE OF LOW TEMPERATURE.
4.PRESERVATION BY USE OF HIGH TEMPERATURE.
5.PRESERVATION OF FOOD BY CREATING ANAEROBIC CONDITIONS.
6.FOOD PRESERVATION BY RADITION.
CONCLUSION
REFERENCE

3. FOOD PRESERVATION
Food preservation is the process of treating and handling food to
stop or greatly slow down spoilage [ loss of quality , edibility or
nutritive value] caused or accelerated by micro-organisim.

4. ADVANTAGES OF FOOD PRESERVATION
• Increase the shelf life of food.
• Make the seasonal food available through out the year
• Add variety to the diet .
• Save time by reducing preparation time and energy
• Stabilizes prices of food.
• Increase the availability of food – improve the nutrition
of the people.

5. TECHNIQUES FOR FOOD PRESERVATION
1.DEHYDRATION(DRYING OR DESICCATION)
a)SUNDRYING b) SMOKING c) MECHNICAL DRYING
d) SALTING e) PICKLING f) ADDING SUGARS g) LYOPHILIZATION
2.USE OF CHEMICAL PRESERVATIVE& ADDITIVE.
a) CITRIC ACID b) BENZOIC ACID & ITS SALTS c) SORBIC ACID & ITS SALTS
d) ACETATES e) SULPHUR DIOXIDE & SULPHITES e) ANTIBIOTICS f) ANTIOXIDANTS
3.PRESERVATION BY USE OF LOW TEMPERATURE.
a) CELLAR STORAGE b) REFRIGERATION c)FREEZING
4.PRESERVATION BY USE OF HIGH TEMPERATURE.
a) PASTEURISATION b) BOILING c) CANNING
5.PRESERVATION OF FOOD BY CREATING ANAEROBIC CONDITIONS.
a) VACCUM FILLING b) MODIFIED ATMOSPHERE PACKAGING
6.FOOD PRESERVATION BY RADITION.

6. 1. DEHYDRATION
(DRYING OR DESICCATION)
• Removal of water from the food.
• Food containing 10% or less of free moisture are not
subjected to spoilage by microbes – unable to grow .
• Dehydrated food → keep in air -tight containers- not
exposed to fluctuations in humidity.

7. a).SUNDRYING
• Heat from Sun is used for drying.
• Materials prepared by suitable methods are placed
on shallow trays in sunlight.
e.g. Raw Mango, Raisins, Dates , Figs, Tapioca chips ,
Bitter gourd & Chilly “kondattams” , Pappad , Fish,
Meat, Prawns, Grains etc.

8. b).SMOKING
Food dried by exposing them to smoke by burning special
wood - mahogany, apple, walnut etc.
• Heat from smoke helps in removal of moisture .
• Exposure to smoke imparts a characteristic flavour.
• Certain bactericidal substances may be formed during
smoking ( formaldehyde, phenols, cresols) and this also
helps in preserving the food to a limited extent.
E.g. – Fish, Meat.

9. c). MECHANICAL DRYING
• Temperature and humidity are controlled
• Products with superior quality, better
colour, correct texture and right flavour can
be obtained.
i) Dehydrators
Food materials are spread in thin layers
on metal trays and inserted in the dehydrator
and dried by heat.
E.g. - Pappad, Green peas, Potato, Jack fruit
etc.

10. ii) Roller dryers
• Finely ground wet suspension of food is spread as a thin
layer on a revolving drum which is heated.
• Dry powder is then scrapped off and packed.
iii) Spray dryers
• Food in the form of a liquid or a finely ground
suspension is pumped through a fine jet and falls as a fine
spray into a chamber through which hot air is circulated.
• The fine droplets of the liquid quickly lose their
moisture by evaporation and fall on the floor of the
chamber as a fine powder.
e.g. Instant coffee, tea, milk powder, gelatin etc.

11. d). SALTING
• Binding moisture by addition of salt –
prevents growth of microbes
• Salt produces high osmotic pressure and
causes destruction of microorganisms by
plasmolysis.
• Dry salting is used in the preservation of
Tamarind
Raw mango
Fish
Meat etc.

12. e). PICKLING
• A very common food preservation technique
• Right amount of salt, chilly, turmeric , asafoetida , oil.
Vinegar etc. used in pickling helps to preserve food.
• A layer of oil on top - prevents the growth of moulds
and yeasts by preventing exposure to air.

13. f). Adding sugar
• High concentration of sugar binds moisture in the
food – water is unavailable for microbes to grow .
e.g: Jam
Jelly
Marmalade (using orange)
Sweetened condensed milk.

14. g) Freeze Drying (Lyophilization)
• Food is preserved by rapid freezing and dehydration of the
frozen material under high vacuum.
• Food is preserved in its natural state - no loss of texture
/flavour
• Food is packed in plastic or Aluminium foil packets in an
atmosphere of Nitrogen Used for the preservation of
• Meat
• Poultry
• Sea foods
• Fruits
• Vegetables.

15. 2. USE OF CHEMICAL PRESERVATIVES &
FOOD ADDITIVES
• Food additive- a substance or mixture of substances
added to food
• Preservatives
• Colours
• Flavouring agents
• Antioxidants
• Emulsifying & stabilizing agents
• Antibiotics etc.

16. CHEMICAL PRESERVATION
• A food additive - arrest or prevent spoilage by microbes
I)Citric acid:
• To increase acidity and prevent mould growth - fruit squash,
jams, jellies
• To flavour extracts, candies
• To adjust pH to 5 – Fish
• To prevent discolouration - Crab meat
• As a dip to delay browning – sliced Peaches.

17. ii) Benzoic acid & its salts
• Effective to inhibit the growth of bacteria, yeasts &
moulds Sodium benzoate is used in
• Jams
• Jellies
• Carbonated beverages
• Fruit juices etc.

18. iii) Sorbic acid & its salts
(Calcium, Sodium & Potassium salts)
• Effective against moulds, yeasts and many bacteria.
• Used as a direct antimicrobial additive in foods
• As a spray, dip or coating on packaging materials
• To prevent refermentation and souring of wine –A
combination of 225 ± 25 mg Potassium sorbate and a 30 ± 10
mg free SO2 prevent refermentation and souring of wine.
Widely used in bakery & confectionary products – Cakes,
Fillings for chocolate, Cheese, Beverages, Dried, fruits Bread
Fruit juice , Jellies , Jams etc.

19. iv) Acetates - derivatives of Acetic acid
• Vinegar (4% Acetic acid), Sodium diacetate More effective
against yeasts and bacteria than moulds.
• Vinegar is used in pickles, Mayonnaise etc.
• Sodium diacetate is used in cheese spreads
• As a treatment for wrappers for butter .

20. v) Sulphur dioxide & sulphites
(Potassium and sodium metabisulphite)
• SO2 – used to treat drying fruits, molasses
• Sulphites – added to wine as preservative Potassium
metabisulphite is used in canning

21. vi) Antibiotics- Aureomycin (Chlortetracyclins),
Terramycin (Oxytetracyclins), Chloromycetin
(Chloramphenicol)
• Inhibit protein synthesis Used to length storage time at
chilling temperatures – meat, fish, poultry etc.
vii) Antioxidants
Used to prevent oxidation of fats and oils which causes
rancidity (Development of unpleasant odour)
Eg;
Butylated Hydroxy Anisole (BHA) Butylated Hydroxy
Toluene(BHT)

22. 3. PRESERVATION BY USE OF LOW TEMPERATURE
• Microbial growth and enzyme reaction are retarded in
foods stored at low temperature.
a)Cellar storage (Temperature about 15 ° C)
• Storage in cellars(underground rooms) slows down the
decomposition.
• Can be stored for limited periods during winter months. Eg
- Root crops ,Potato ,Onion, Apple, Cabbage
b)Refrigeration or Chilling treatment (Temperature 0 °C – 5 C)
• Retard the growth and metabolic activities of microbes
• Can be stored for a few days
• Fruits, Vegetables ,Meat, Poultry , Milk , Fish ,Egg ,Prepared
Food.

23. c) Freezing (Temperature, - 18 °C to – 40 ° C)
• The growth of microbes and enzyme activity are reduced
to the minimum.
• Can be stored for long periods – a few weeks to months .
• Before freezing, vegetables are given blanching (mild heat
treatment, above 80 °C)to inactivate the enzymes .
Quick freezing – at temperatures between -18 °C to – 34 ° C
for 30 minutes or less
• Maintain the identity and freshness when they are
thawed(brought to room temperature) because very small
ice crystals are formed during quick freezing.
Eg; Vegetables ,Fruits (Strawberry) ,Meat, Sea foods,
Mushrooms etc.

24. 4. PRESERVATION BY USE OF HIGH
TEMPERATURE
• Most reliable and safest method
• High heat coagulate proteins and inactivate the enzymes
of microbes → destruction
a)Pasteurisation (Temperature below 100 °C)
• Brief exposures to moderately high temperatures to
reduce the number of viable microorganisms and kill the
pathogenic microorganisms.
• Used where drastic heat treatment may cause
undesirable changes in the food
• Usually supplemented by other methods – sudden
cooling and keeping in refrigeration to prolong shelf life.

25. i) High Temperature Short Time (HTST)
Milk is heated to 72 °C for 15 seconds and rapidly cooled
to 10 °C and kept under refrigerated conditions – inhibits the
growth of organisms that may have survived.
ii) Low Temperature Long Time (LTLT)
Milk is heated to 62.8 °C for 30 minutes followed by sudden
cooling to 10 °C and kept under refrigerated conditions.

26. USES OF PASTEURISATION
• Beer
• Fruit juices
• Aerated drinks
• Dried fruits –Raisins , Apricots, Dates etc.
• Grape wine –pasteurized at 81 °C - 85 °C for 1 minute
• Grape juice at 76.7 °C for 30 minutes.

27. b)Boiling( Temperature 100 °C)
• Kills the vegetative cells and spores of yeasts and moulds
• Kills only the vegetative cells of bacteria.
• Cooked food can be preserved from 12 – 24 hrs at room
temperature, esp. on winter months.
• Cooking of rice
• Vegetables
• Milk
• Meat
• Fish

28. c)Canning( Temperature above 100 °C;
Steam under pressure , 121 °C)
• Discovered by Francois Nicolas Appert (1809) –
Appertization.
• Most widely used method
• Exposure to high temperature for longer periods – kill
endospore -forming bacteria. Steam under
pressure(Pressure cooker or autoclave)
• Most effective method – kills vegetative cells and spores
• Heating to high temperature is followed by rapid cooling

29. CANNING PROCESS
i) Cleaning – Select high quality materials and clean –fresh
vegetables, fruits, meat etc.
ii) Blanching – in hot water or in steam – kills microbes, fixes
natural colour , removes air within product and inactivates
enzymes.
iii) Filling of cans or jars –Hot food is filled into cans
(tin cans →made of tin –coated steel, glass containers, flexible
pouches, plastic bags.
Aluminium cans → used only for products that do not require
high vacuum or high temperature processing such as beer,
frozen fruits and juice concentrates, cheese etc.)

30. iv) Autoclaving
• Cans → steam under pressure
• Duration depends on load - more time for heavily loaded.
• Non-acid foods →116 -121 °C at lbs/psi pressure for 1 -2
hours.
• Meat require more time • Acid foods require only
immersion of cans in boiling water
v) Cooling
• Autoclaved cans are immediately cooled → prevent
undesirable changes in texture and flavour due to
overcooking.

31. 5. PRESERVATION OF FOOD BY CREATING
ANAEROBIC CONDITIONS
Prevent the growth of aerobes
a) Vacuum filling- food materials are packed in impermeable plastic
material and the air is sucked out to create vacuum. Used for Nuts-
to reduce loss of flavour due to oxidation Meat Cheese etc.
b) Modified atmosphere packaging
• Enclosure of food in a package in which the atmosphere is
changed by altering the proportions of Carbon dioxide, Oxygen,
Nitrogen ,watervapour and trace gases.
• Retards microbial and biochemical activity.
• Salad crops are packaged in sealed bags with an atmosphere
modified to reduce Oxygen concentration and increase carbon
dioxide concentration.
• Can be used to increase the shelf life of bacon, red meat, poultry,
vegetables etc.

32. 6. FOOD PRESERVATION BY RADIATION
• Approved only in a very limited way.
• Mainly used for spices and condiments
• Reduces the number of microbes and insects – replaces the
chemicals used for this purpose.
• Inhibits sprouting in Potato, Onion, Garlic etc.
• Delays ripening in Banana, Avocado, Papaya, Guava etc.
• UV rays are the most widely used – for the treatment of water
for beverage and knives for slicing bread, sanitizing eating
utensils etc.
• Gamma rays are also used.
• Irradiated food materials – meat, fish, poultry etc. can be
stored at room temperature without spoilage.

33. CONCLUSION
Food preservation has been pivotal to our society since
the beginning.
Preservation has come from simple processes such as
salting, to more complex preserving methods such as
irradiation and chemical additives.
Looking intothe future, High Pressure Preservation seems
to be the next logical step.

34. REFERENCES
• Adams, M.R., and Moss, M, O., 2008. Food Microbiology, third
edition. RSC publication, UK.
• Ray, B., Fundamental Food Microbiology, third edition, 2004.
CRC press.
• Jay, J.M., Loessner, M.J., and Golden, D.A., Modern Food
Microbiology, seventh edition, 2005. Springer.
• Rahman, M.S., Handbook of Food Preservation, second edition,
2007. CRC press.