1. PRESENTATION ON
“Preservatives”

2. Definition:
Preservatives are those chemicals which used alone or in combination to prevent the growth of microorganisms in solution.
On the other hand, Preservatives are substances which prolong the shelf-life of foodstuffs by protecting them against deterioration caused by microorganisms. The preservatives are one of the 26 major additives categories that are used in the food processing.

3. Examples: Common antimicrobial preservatives include-
Sorbic acid and its salts,
Benzoic acid and its salts,
Calcium propionate, sodium nitrite, sulfites and disodium EDTA.
Antioxidants include BHA, BHT, TBHQ and propyl gallate.
Other preservatives include ethanol and methylchloroisothiazolinone.

5. Why preservatives are important?
Since foods are an excellent source of nutrients for the growth of microorganisms, causing problems such as
Bad taste,
Unpleasant smell and
Poor appearance
The preservatives aim at altering those conditions where microorganisms grow and prevent their growth.
The main purpose of preservatives is to maintain the safety of food for human consumption, retain its nutritional value and its overall quality. 

6. Mechanism Preservatives work in one of three ways.
They can prevent growth of microorganisms by creating an environment hostile to them.
They can block the process of oxidation that causes foods to turn rancid.
They can inhibit the enzymatic processes that cause a food to ripen after it is harvested.

7. General types There are three types of preservatives;
Antimicrobials which inhibit the activity or growth of microorganisms and moulds,
Antioxidants which are used to prevent the oxidation of vitamins, minerals and lipids of foods, and
Antibrowning agents which prevent both enzymatic and non enzymatic browning of foodstuffs. 

8. Types of Preservatives in Pharmaceutical Chemistry
Benzoic Acid
Benzoic acid and its salts inhibit the growth of bacteria, yeast and mold. It is used in chemically based ointments to treat fungal diseases, such as athlete's foot, ringworm. A 0.1 percent concentration of benzoic acid is used in pharmaceutical applications. It is used as an antiseptic in mouthwashes and lotions.
Salicylic Acid
Salicylic acid is found as a fluffy powder or as white crystals. It is used as a preservative in food for its antimicrobial properties. Salicylic acid is toxic in large quantities.

9. Cresol
It inhibits the growth of numerous pathogenic organisms and is a powerful germicide and antiseptic percent concentration of cresol is used in pharmaceutical chemistry .short-term exposure to the substance causes throat irritation, nasal constriction and other respiratory tract irritation. P-cresol, m- cresol and o-cresol are possible human carcinogens (cancer causing substances).
Cetrimide
It is a popular preservative for its antimicrobial properties. Cetrimide affects and disrupts the cellular functions of microorganisms, rendering them ineffective. It is used in pharmaceutical chemistry as an antistatic agent, detergent sanitizer, softener for paper products and textiles.

10. Examples of preservatives in pharmaceutical preparation
Preservatives in solution:
Preservatives in suspension
Perservatievs in Emulsion
Alcohol. e.g. Ethanol(> 10%)
Acids. e.g. Benzoic acid(0.1 % to 0.5%)
Esters. e.g. Parabens up to about 0.2%.
Quaternary Ammonium Compounds.
e.g. Benzalkonium chloride( %).
Benzalkonium chloride ; ( ) %
Disodium edentate ; 0.1 %
Propyleneglycol ; (5-10) %
sorbic acid
boric acid;

11. Advantages
Enhanced Flavor and Appearance: Food preservatives which help to maintain flavor are sulphities, sulphur dioxide, and tocopherols.
Inhibits microbial growth & autolytic enzymes.
Retains most nutrients.
Process does not destroy nutrients.
Increases salt and sugar content of food.
Destroys microorganisms.
Chemical preservatives Prevent microbial growth

12. Disadvantages:
Can cause loss of some nutrients, particularly thiamin & vitamin C.
Sulphur dioxide is sometimes added to dried fruits to retain vitamin C, but some individuals are sensitive to this substance.
Blanching of vegetables prior to freezing causes loss of some B- Group vitamins and vitamin C.
Preservatives Can Have Allergic Consequences :The food additives BHA and BHT have inconclusively been linked to cancer and carcinogenic activity.
Some modern synthetic preservatives have been shown to cause respiratory or other health problem. For example sulfites are commonly used in wines and some dried fruits or vegetables and are known as possible irritants to people with asthma.

13. THANKS TO ALL.....