* Product are tested using cultures of microorganisms like *Aspergillus niger, Candida albicans, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa.*
* a. Cultures of microorganisms like Aspergillusniger, Candida albicans, Escherchia coli and Pseudomonas aeruginosa, each containing about 10,000 – 10,00,000 organisms per ml are selected.
* b. Three to four samples of each preparation are taken in sterile test tubes and inoculated with few ml of each culture separately.
* c. They are incubated at 20 - 25°C for a period of 28 days and are observed weekly for the appearance of turbidity.
* d. No growth of microorganisms indicates that the preservative is totally effective.