Preservation of fopd by chemical method and UV

3. Preservation of food by chemical
method and UV radiation
NAME SHANZA TANVEER
ROLL NO# FA -17 BS BCH/010

4. Food preservation:
 Food preservation, is the process of treating and
handling food to stop or slow down food spoilage, loss of
quality, edibility, or nutritional value and thus allow for
longer storage.
 It prevents the food from being spoiled by the action of
enzymes and microorganism.
 There are several methods for the preservation of food
but only two methods we are discussing here.
 Chemical methods
 UV radiations

5. Principle of food preservations:
Preventing entry of microbes can be done by,
 Asepsis- packaging the food in cans or airtight containers.
 Filtration- used to filter liquids like juice water and alcoholic
beverages.
 Creating conditions by which the microbes in the food do
not grow like freezing, drying etc.

6. Food preservation by chemical
methods:
 The purpose of using a chemical agents as a preservative
is to retard food spoilage caused by microorganism.
 The use of chemical agents or preservative will prolong the
shelf life of the food even further.
 Chemicals that function to preserve the food are generally
added after the food has been processed and before it is
packaged.

7. Chemicals preservatives
Traditional chemical food preservatives
 Sugar
 Salt
Acidulates and gaseous chemical agents
 Sulphites and sulphur dioxide 0.005-0.2%
 Sorbic acid 0.05-0.2%
 Benzoic acid less than 0.1%
 Citric acid no limit

8. Procedure
 The addition of salt:
 Salt is used in brines or is directly applied to the food.
 Their effect is to increase osmotic pressure at a level which will prevent
microorganism development.
 The cell growth of the microorganism is inhibited or the organism itself
may be completely destroyed.
 Salt also cause dehydration by drawing out and tying up water from the
tissue of the food.
 The more salt used the greater the protection afforded by the food.

9. Food preservation by the addition of
sugar:
 Sugar is used to preserve fruits, either in syrup with fruit such as apples,
pears, or in crystallized form where the preserved material is cooked in
sugar to the point of crystallization and the resultant product is then stored
dry.
 Sugar is generally added in the processing of jams, jellies and sweet.
 The fruit must be boiled, after which the sugar is added in variable
amounts, depending upon the kind of fruit and the product being
prepared.
 The mixture must then continue to boil until it reaches a high level of
soluble solids, which allows for its preservation.

10. Sulphites and sulphur dioxide:
 Fruit puree can be preserved by adding 600ppm sulphur dioxide (SO2)
and sealing in drums.
 The semi-processed food can be stored for several months.
 Sulphur dioxide is used to preserve the color and increase the shelf life of
dried foods.
 There are two main methods of adding sulphur to foods - sulphuring and
sulphiting. Sulphuring is more common for fruits and sulphiting for
vegetables.
 Sulfur dioxide is also used as a preservative in manufactured meats,
sausage, and soft cheeses. In meat the flesh color is stabilized.

11. Sorbic acid:
 Sorbic acid and sodium and potassium sorbate are used to inhibit the
growth of moulds and yeasts.
 The activity of sorbic acid increases as the pH decreases.
 Sorbic acid and its salts are tasteless and odorless when used at levels
below 0.3%.

12. Benzoic acid and benzoate:
 Benzoic acid and benzoate is a stable, white, granular or crystalline powder
possessing a sweet taste.
 Benzoic acid, in the form of sodium benzoate, is a widely used food
preservative suitable for acid foods.
 It is primarily used as an antifungal agent in fruit-based and fruit beverages,
fruit products, bakery products and margarine .
 Sodium or potassium benzoate can be added to fruit products to control the
growth of mould and fungus. They are usually added to products that are
opened and not used in one go, for example fruit squash. It is not essential to
add these preservatives to products that have been properly processed or
are stored in good conditions, but they can help to extend the shelf life of
certain products..

13. Citric acid
 Most foods may be preserved by heat treatment when they
have a pH lower than 4.0.
 Citric acid is found naturally in citrus fruit. It is widely used
in carbonated drinks and as an acidifier of foods.
 It is less effective at controlling the growth of yeasts and
mould than the other acids.
 This acid is more effective than acetic and lactic acids at
inhibiting the growth of thermophilic bacteria.

14. Food preservation by UV radiations:
 Ultraviolet radiation (UV) is a nonionizing radiations.
 It is widely used in food industry to control microorganism by the use of
UV lamp.
 It is becoming a more popular technique in decreasing pathogens from
food and beverage products. This type of radiation comes from the sun,
as well as artificial means.
 Ultraviolet light is a safe and proven way to kill pathogens and extend the
shelf life of food and beverages.

15. Why it is non thermal treatment?
 UV treatment is performed at low temperature and it is
considered as non thermal disinfection method.
 Fruit juices that undergo thermal pasteurization or
sterilization tend to change color and lose some of its
aromas and vitamins during the process of heating.
 Unlike juices that are treated with UV radiations, which tend
to maintain their aroma and color.

16. Mode of action:
 Radiations with wavelength near 260 nm is absorbed
strongly by purines and pyrimidine.
 In order to kill microorganism, the UV rays must strike the
cells. UV energy must penetrates the outer cell membrane,
passes through the cell body and disrupt its DNA
preventing reproduction.

17. References:
 Ray .B , fundamental food microbiology, third edition
2004,CRC press.
 Rahman,M.S . Handbook of food preservation, second
edition 2007,CRC press.