PRESERVATIVES
100 90 80 70 60 50 40 30 20 10 0
12 9 7 6 5 4 3 0 2 7 14 Days Figure 1: Challenge test results against Staphylococcus aureus.
Materials and methods Twelve different oil-in-water emulsions have been formulated in the laboratory with the general composition shown in Table 1. The emulsifier concentration has been chosen according to the recommendations provided in the suppliers’ product documentation. The type of emulsifiers and respective use concentrations are shown in Table 2. In cases where the emulsifier blend already contains fatty alcohol as one of the components, the amount of fatty alcohol in the core formulation has been reduced accordingly to end in all cases with a total concentration of 4% fatty alcohol in the final formulation. The acidity of all formulations has been adjusted to pH 5.3 in order to exclude the influence of a variable pH on the antimicrobial
21 1 28 Days Figure 2: Challenge test results against Pseudomonas aeruginosa.
performance of the organic acids. A standard procedure has been employed to emulsify the water and the oil phase in a hot-hot process. The stability of the emulsions has been assessed by storage at room temperature, 4˚C and 40˚C over a period of three months as well as freeze-thaw-cycles. The stability tests demonstrated sufficient stability for all twelve emulsions. The droplet size and distribution has been checked under a microscope.
Microbiological challenge tests according to the European Pharmacopoeia 3 have been performed with all emulsions. Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 9027), Escherichia coli (ATCC 8739), Candida albicans (ATCC 12231) and Aspergillus
brasiliensis (ATCC 16404) were used as microorganisms in this single inoculation test protocol. The plate counts have been performed after 2, 7, 14 and 28 days after inoculation. Plate counts at time zero resulted in between 250,000 and 1,250,000 colony forming units per gram (cfu/g). A typical graph of the results of a single inoculation challenge test will show the reduction of the total number of microorganisms expressed as the logarithmic number of colony forming units, starting with the plate count at time zero. For the display of challenge test results in Figures 1-5 the relative logarithmic reduction is shown, with the plate count at time zero set as 100%. When the plate count at time zero is 1,000,000 cfu/g = 100% (log cfu/g=6), a plate count of
10 8 11
100 90 80 70 60 50 40 30 20 10 0
9
12 10 8 7 6 5 4 3 0 2 7 14 21 1 28 11
100 90 80 70 60 50 40 30 20 10 0
12 9 1 110 8 7 6 5 4 3 0 2 7 14 Days Figure 3: Challenge test results against Escherichia coli. 21 1 28 Days Figure 4: Challenge test results against Candida albicans. February 2016 PERSONAL CARE 61
100 90 80 70 60 50 40 30 20 10 0
9 1 110 8
7 6 5 4 3 0 2 7 14 21 1 28
12
Remaining log cfu/g (%)
Remaining log cfu/g (%)
Remaining log cfu/g (%)
Remaining log cfu/g (%)
Emulsifier (see Table 2)
Emulsifier (see Table 2)
Emulsifier (see Table 2)
Emulsifier (see Table 2)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76
