PRESERVATIVES A ■ B ■ Failed ■
40 35 30 25 20 15 10 5 0
S. aureus P. aeruginosa
E.coli C. albicans A. brasiliensis
35 30 25 20 15 10 5 0
S. aureus P. aeruginosa
E.coli Figures 2 and 3: Challenge test results of Evicide levulinate S without (left) and with (right) an added boosting agent
results quantitatively and statistically, and try to make valuable deductions from the findings. This is what has been dubbed at times the ‘meta-analysis’ approach – and this is what we at evident ingredients employ to assess preservation efficacy of our antimicrobials. In practice this means that we focus
not on one single challenge test result, but instead consider a statistically significant number of PETs with the same preservation, and judge the overall performance against each microorganism individually based on EP criteria. This way outliers carry less weight and overall trends become more clear. As an example, a visual representation of
the results of 33 different challenge tests with the preservative Evicide® levulinate B (active ingredients: levulinic acid, benzoic acid) is shown in Figure 1. As shown, application of Evicide levulinate
B usually gives good results in the tested formulations, though some ‘Fails’ have been recorded as well. It is indicated that the organism
A.brasiliensis is the one responsible for the largest number of failed tests and ‘B’ results. As a take-away we can learn that in some cases of difficult to preserve formulations further boosting specifically against this microorganism is necessary. When data is bundled together as shown, its careful selection is important, because the
A ■ B ■ Failed ■
100 90 80 70 60 50 40 30 20 10 0
S. aureus P. aeruginosa
E.coli C. albicans A. brasiliensis
250 200 150 100 50 0
S. aureus P. aeruginosa
E.coli Figures 4, 5 and 6: The results of bundled challenge tests in different pH ranges
www.personalcaremagazine.com July 2022 PERSONAL CARE C. albicans A. brasiliensis
data that goes in defines which conclusions can be drawn. For example, in the above figure, challenge test results based on emulsions, surfactant based formulas and water based systems were used together. In this case, even though we learn about
advantages as well as shortcomings against the specific microorganisms, no differentiation of the efficacy between those formulation types can be made. In another example we can see how
preservatives can benefit from the addition of boosting agents. Microorganism specific challenge test results (n=37) with our preservation blend Evicide levulinate S (active ingredients: levulinic acid, sorbic acid) are shown in Figure 2 Compared to the data presented above,
the well known strength of potassium sorbate against
A.brasiliensis is underlined, though the performance against bacteria
E.coli and
S.aureus is in some cases not ideal. This can be remedied through the addition
of a boosting agent such as Caprylyl Glycol (Evicide® G 8), which resulted in a significantly improved performance in the PETs analysed in our statistical approach (n=29). We can see that using meta-analysis, or
bundling of PET results gives us valuable insights into strengths and shortcomings of preservation systems. Yet it does not stop there.
A ■ B ■ Failed ■
60 50 40 30 20 10 0
S. aureus P. aeruginosa
E.coli C. albicans A. brasiliensis In the above examples, the parameter
‘preservation system’ was fixed, while the parameters ‘pH’ and ‘formulation type’ were variable. If we swap this around, some interesting general conclusions can be drawn.
Meta-analysis based on formulation types and pH ranges Interestingly, we are not limited to analysing PETs of specific preservation systems, but with a large data pool we can ask interesting questions such as: how does my preservative perform in rinse-off applications? How about limiting this question to a specific pH? Which microorganisms usually causes trouble in O/W emulsions? Figures 4-6 show results of bundled
challenge tests in different pH ranges. Since the five microorganisms commonly tested in PETs have varying optimal growth conditions in regards to pH, we were curious to see if this is reflected in the PET performance when differentiated in respect to the pH value. As a general trend it becomes apparent
that at lower pH levels, microbial contamination is fought of more efficiently in the studied challenge test sample. This is in line with the general consensus on growth conditions. In the medium level pH range 5.0-6.0, which is probably the most common among
A ■ B ■ Failed ■ C. albicans A. brasiliensis A ■ B ■ Failed ■
49
Number of Challenge Tests
Number of Challenge Tests
Number of Challenge Tests
Number of Challenge Tests
Number of Challenge Tests
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 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96
