Preservation of solubilized and emulsified systems II: Theoretical development of capacity and its role in antimicrobial activity of chlorocresol in cetomacrogol-stabilized systems.

The preservation of solublized and emulsified disperse systems against microbial spoilage depends on the free (unbound) preservative concentration in the aqueous phase and the capacity of the system. The capacity may be defined as the system's ability to resist losses in free preservative concentration. The theory of capacity is developed quantitatively for solubilized and emulsified systems containing the preservative chlorocresol stabilized by the nonionic surfactant cetomacrogol. Equations are derived for solubilized systems that relate capacity to surfactant concentration and the interaction between the surfactant and the preservative. Additional terms are included in the equations to account for the effects of the oil phase on the capacity of oil-in-water emulsions.