Preservatives

PRESERVATIVES

1) Preservatives are used for prevention or retardation of the growth of micro organisms in a preparation.
2) Amount of preservatives need not be calculated. Preservatives are widely used at low concentrations of cosmetic formulations.
3) Certain preparations do not require preservatives like powders and preparations with high concentration.
4) A minimum of 5% moisture is required for growth of micro organism. Optimum PH for growth of organisms is 2-8.5. Osmotic pressure and presence of preservatives, presence of nutrients etc all affect the growth of microbes in a preparation. Molds, yeasts and bacteria can all grow in cosmetic preparations.

Molds : Molds grow best at room temperature 25-30C, and at a pH of 2 to 5.55.
They do not grow at pH more than 7 and high osmotic pressure. They cannot grow conveniently under light.

Eg: Penicillin, rhizopus, Mucur, Aspergillus.

Yeasts : Yeasts cannot manufacture their food. Therefore they require
fermentable sugars. Optimum pH for yeasts is 2.2 to 8 but prefer acidi PH, room temperature is convenient for them any they require high amount of oxygen.
Eg : Sacromyces, Candida

Bacterial : Optimum temperature for bacteria is around 37 C. The best is in a
pH 7.2 to 7.6 any need 7 to 10% cent of moisture for growth.

Eg: Pseudomonas, Aerobacter, B.subtilis, E.coli, Staphv.citrus.

Based on the type of micro organism which can be present the preservative should be selected.