ASTM E640 − 06 Preservatives in Water-Containing Cosmetics

Scope:

This test method should be performed to establish whether a preservative or preservative system can be utilized to preserve water-containing cosmetics. Routine microbiological procedures are used to determine the antimicrobial activity of preservatives in formulations.

Procedure

The bacterial cultures are grown on the proper slants using a sterile inoculum.  The development from each culture is transferred into tubes of lasting loops. The yeast cultures are harvested and suspension is adjusted with sterile saline. Serial dilutions of the challenge inocula are prepared ahead of time. Lethean agar is used to duplicate the plates. Bacteria and yeast are incubated. The test is prepared by weighing 20 g aliquots substance into appropriate glass jars. The diluted test samples are plated in the bacteria and fungi recovery agars. Gram staining is used to identify bacteria. Infected samples are tested at regular intervals. Inoculated samples are tested at a minimum interval.

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Data

Percentage Reduction = Inoculum Count – Sample Count × 100 Inoculum Count

Specimen size

Test microorganisms or equivalent species may be used as per standard requirements. 

Results

If the inoculum counts are within the specified ranges, the test is declared valid.