Natural and physical preservative systems
Natural and physical preservation can be considered as a preservative system that utilizes physical preservatives, e.g. pH, natural antimicrobial agents or antimicrobial formulation components. This chapter describes the various alternatives and their applications and limitations as a means of achieving preservation. During the manufacture of non-sterile pharmaceuticals, cosmetics and toiletries and during subsequent use, the product is exposed to a variety of microbial contaminants. For pharmaceuticals, cosmetics and toiletries, temperature is not a common form of preservation because it is impracticable to store most formulations at sufficiently low temperatures to prevent microbial growth. Packaging can be classed as a preservative mechanism in that it can act as a chemical, physical and biological barrier to the outside environment. Heat can also be used during processing for a variety of formulations, e.g. oral liquids and skin creams. The other major disadvantage for filtration is that it gives no residual protection to the formulation.