DEFINITION & CONCEPT
IDEAL PROPERTIES OF PRESERVATIVES
CLASSES OF PRESERVATIVES
FACTORS AFFECTING EFFECTIVENESS OF PRESERVATIVES
GUIDELINES FOR SELECTION OF PRESERVATIVES
SOME ADVERSE AFFECTS OF PRESERVATIVES
DEFINITION & CONCEPT
Used to prevent spoilage
Reasons of spoilage:
Absence of preservative causes deterioration
Water: responsible for microbe growth
Anhydrous preparations: microbes attack
Prepn contains oils & fats: both
A. ANTIMICROBIAL AGENTS
What happens if unable to control growth of
Unable to stop multiplication
GUIDELINES FOR SELECTION OF
Identify the materials which promotes microbial
e.g. glycerin, gums, proteins, carbohydrates, cellulose.
pH i.e. some are active in acidic or basic
Partition of preservatives
Ratio of total to free preservative
Least toxic should be selected
Some Adverse Affects of
Parabens: cracked or inflamed skins
Quaternium-15: contact dermatitis, especially in those with
sensitive skin, an infant's skin
Formaldehyde: environment & health problem
Sorbic acid: allergic reactions
Euxyl K 400: contact dermatitis
Phenoxyethanol & Methyldibromoglutaronitrile
14. B. Antioxidants
Factors affecting rancidity
Classification of antioxidants
Choice of antioxidants
Ideal characteristics of antioxidants
Antioxidants used in aqueous system
Antioxidants used in non- aqueous system
Antioxidants and synergist
Antioxidants & their concentrations.
16. Factors affecting rancidity
Presence of pro-oxidants
From the above it is very clear that cosmetics
containing fats and oils must be preserved by
adding antioxidants besides antimicrobial agents. 16
17. Classification of Antioxidants
Based on chemical classes:
Organic Acids, Alcohols & Esters
Inorganic Acids & their Salts
18. Gallates Gallic acid
Color develop in presence of iron
Mixture of gallate with BHA used.
0.01 to 0.1% generally used.
Phenolic type antioxidants
19. BHA BHT
Not used alone
Generally used with gallates
Following mixture is generally
Propyl gallate 6%
Citric acid 4%
Propylene glycol 70%
Used for fatty acids & oils
No phenolic smell
Stability towards heat
0.01 to 0.1% used with
sequestering agents like citric
acid or EDTA.
Phenolic type antioxidants
21. Quinone type antioxidants
Tocopherol : natural source
Solvent extracted wheat germ oil: contains tocopherol
Not used widely due to
Their high cost,
Little usefulness in preservation of vegetable oils
Used in animal fats with synergists like citric acid,
lecithin or phosphoric acid.
22. Amine type antioxidants
Generally used in combination with other antioxidants.
23. Organic Acids, Alcohols & Esters
di- lauryl thiopropionate
di- stearyl thiopropionate
Used as antioxidants synergist and are used in combination
with other antioxidants
24. Inorganic Acids & their Salts
Phosphorous acid and salts
Phosphorous acid and salts used as
26. Choice of antioxidants
Nature of fat and/or oil
Physical form of cosmetics
pH of cosmetics
Intended use of cosmetic
Expected shelf life of cosmetics
Storage condition of product
27. Ideal antioxidants
Effective over wide range of pH
Soluble in its oxidized form
Reaction products should be colorless & odorless
28. Antioxidants used in aqueous
iso- ascorbic acid,
29. Antioxidants used in non-aqueous
34. A surfactant or surface active agent is a substance
that, when dissolved in water, gives a product the
ability to remove dirt from surfaces such as the
human skin, textiles, and other solids.
Surfactants are wetting agents that lower the surface tension of a
liquid, allowing easier spreading, and lower the interfacial tension
between two liquids.
Surface tension is an attractive property of the surface of a liquid. It
causes the surface portion of liquid to be attracted to another surface,
such as that of another portion of liquid.
Interfacial tension a phenomenon at the surface of a liquid caused by
36. Surface active agents
Widely used in shampoos, dentifrices
reduction in surface or interfacial tension
Amphiphilic in nature
37. Role of surfactants
Detergents, foaming, cleaning agents
Used in hand creams, lotions.
Fatty acid soaps, sulphuric esters (Na salts)
Substantive to protein at acid pH
Produce emulsions with acid pH
Germicidal if not inactivated by anionic.
Used with cationic
Polyoxyethylene lauryl alcohol, Polyoxyethylene stearate,
propylene glycol monostearate. 38
39. Foaming & Cleaning Agent or
Generally used in shampoos.
Detergents have molecules with one side that prefers water
(hydrophilic), and another side that prefers oils and fats (hydrophobic).
The hydrophilic side attaches to water molecules, and the hydrophobic
side attaches to oil molecules.
This action allows the oil droplets to break up into smaller droplets,
surrounded by water.
These smaller droplets are no longer stuck to the material to be
cleaned, and are washed away. 39
40. Ammonium Lauryl Sulfate:
used in many shampoos, toothpastes, and skin cleansers.
Ammonium Lauryl Sulfate + ethylene oxide = ammonium
laureth sulfate (ammonium lauryl ether sulfate)
used in shampoos as a detergent and as a thickening agent
molecules with both a polar and a nonpolar end polar
portion is hydrophilic (water-loving)
nonpolar, hydrocarbon end is hydrophobic (water-hating or
fearing) or lipophilic (oil-loving) …CH3CH2CH2CH2CH2-etc.
45. Amphoteric surfactants
Carry cationic charge in acidic media
Carry anionic charge in basic media
Form zwitterionic species at neutral media
46. Amphoteric surfactants Examples
N- alkyl amino acids:
best foaming in slightly alkaline pH
Cationic in acidic & anionic in alkaline soln
Stable in wide pH range of 2 to 12
Used in baby shampoos.
47. Anionic surfactants
Soap, alkyl sulphonates not used in shampoos.
alpha- olefin sulpohontes, alkyl sulphate are used in
Sulphosuccinates are widely used in shampoo due
to safety to the eyes.
48. Cationic surfactants
Have inferior cleaning and foaming property.
Have affinity to proteins: results in re-deposition of
dirt on hair fibre.
Irritant to eyes so limited used.
Used as additives
Alkyl trimethyl ammonium, stearyl dimethyl benzyl
49. Non- ionic surfactants
Polyglyceryl ether: widely used
No irritation to eye mucosa.
Used as main surfactants in shampoos.
Ethoxylated fatty acid, pluronics, sorbitol esters
50. Wetting agents
All surfactants have wetting properties.
Alkyl ether sulphate, alkyl aryl sulphonates