PRESERVATIVE EFFICACY TESTING METHOD 417 Table III Statistics Data Comparing D-Values in Preserved and Unpreserved Powders Microorganism F-value Critical F-value Staphylococcus aureus 10. 54417 5.59146 Pseudomonas aeruginosa O. 131475 4.964591 Candida albit•ns 217.5148 5.117357 critical F-value of 4.96 (Table III). However, in Figure 6, one can observe that the curves constructed for the tests with preservative presented a steeper slope (i.e., faster die-off) than the ones for the tests without preservative. Such behavior can also be seen for S. aureus and C. albicans (Figures 6 and 7). LogCFU/õ 5 1- 0 0 $ Time (days) a Lag CFUIg Time (days) Log CFU/g o 5 Log CFUlg 7- 6- •) 15 3) 2• 3) 0 5 10 15 39 25 3:) Time (days) Time (days) c d Figure 6. Survival curve of bacteria in the sample with preservative (P) and without preservative (NP). (a) S. aureus, sample P. (b) S. aureus, sample NP. (c) P. aeruginosa, sample P. (d) P. aeruginosa, sample NP.

418 JOURNAL OF COSMETIC SCIENCE Log CFU• 7 0 5 10 15 Time (days) a I-7:1 Log CFU/g 7 o o 5 10 15 33 25 33 Time (days) Log CFU/g Log CFU/g '1 7- 0 5 10 15 2) 25 3D 0 5 10 15 2) 25 3D Time (days) Time (days) c d Figure 7. Survival curve of fungi in the sample with preservative (P) and without preservative (NP). (a) C. a/bicam, sample P. (b) C. a/bicam, sample NP. (c) A. ,iger, sample P. (d) A. ,iger, sample NP. One exception was noted in the curves for A..iger (Figure 7) that presented similar behavior for both treatments. These data indicate that the preservative in the powder was not effective against this organism. The same behavior can be noticed in Table II. The D-value average and the analysis of variance could not be calculated because of the low correlation coefficients. The results obtained against S. aureus in both samples (with and without preservative) indicated that the antimicrobial activity was effective according to the US and the Japanese pharmacopoeia requirements (6,9). However compared to the British and Eu- ropean pharmacopoeias (7,8) and the CTFA (10) requirements, just the preserved sample