44 PRESERVATIVES


several strains of bacteria to different combinations of fabrics. This is demonstrated by comparing biofilm


formation of P. aeruginosa on PET fibres (as seen in Figure 4) vs viscose fibres (Figure 5). It is clearly shown that bacteria have expanded into a biofilm, coating the viscose fibres completely. At the same time, the PET remained mostly cleaned. The same study was repeated with several microbial strains, to show similar results with S. aureus, E. coli and others. Based on these findings, we can now


conclude that the preservation challenge of wet wipes has more complexity than was assumed in the past. There is a clear need to find a solution that can deal with both obstacles – the formula, and the fabric. The goal was to create a solution that will


address and solve the challenges described above, but also to take into account the industry’s requirements. It should be easy to incorporate in the wet wipes’ production, answering the need for a clean label and of course being safe for baby care.


The ultimate solution The proposed platform shared here is an integrative solution that addresses all these aspects. Obviously, no one component can achieve such a task. Therefore, building a dual-efficacy solution will come from a careful selection of components which will work together. The first key component is zinc acetate.


This highly hydrophilic ingredient is demonstrating high water-solubility. It is known to have a favourable safety profile - it is GRAS listed and also used as a food additive, as it has an E number (E650). It is not pH-dependent, is within the pH window of interest for wet-wipes applications and comes in a form of a white powder. In the personal care segment, it can be


found in oral care products and in sensitive skin applications, such as anti-acne treatments and skin cleansers. The next key component is maltol. This


is a naturally occurring organic compound found in several plants. It is not very common in personal care, but is used in fragrances as a masking agent, and has already been identified by Sharon Laboratories in the past


Figure 5: Comparing biofilm formation of P. aeruginosa on viscose fibres


as a promising ingredient for incorporation as part of preservation systems. Maltol is used primarily as a flavour


enhancer (as a food additive E636), found in the bark of larch tree, Katsura tree (Cercidiphyllum japonicum), in pine needles, and more. It is also used as intermediate in the pharmaceutical industry. It comes as a white crystalline powder, has an EWG score of 1, is GRAS approved and found in Cosing, has good solubility in water and can be characterised as hydrophilic. In the proposed solution for wipes, maltol is used as an anti- biofilm component. To create an ever more robust system, a safe, yet mild preservative from the segment of organic acids is introduced, such as sodium benzoate. The impact of such a robust system


showing full control of microbial contamination can be observed by means of a challenge test, which is the standard method for the evaluation of a preservative systems. The good challenge test results that can be seen in Figure 6 are just one example of the many challenge test performed with this wipe preservation system, at a level of use of 0.7%. No additional preservatives or EDTA were added to the formula. The decision was to do a set of challenge tests at pH 5.5, which is at the high point of the spectrum when it comes to wipes, where often pH of 4.5 or 5 is common. By taking it to the highest level, we demonstrate that the efficacy of this system is not driven by means


E.coli■ S.aureus■ P.aeruginosa■ C.albicans■ A. niger■ 1.5


6 5 4 3 2 1


0 1 0.5 0


of reducing the pH of the formula, which of course can only reinforce it further. In this study however, good challenge test


results are not sufficient – as our goal was also to contain the biofilm. The impact of the antibiofilm can be seen in Figure 7, when the efficacy of preservation is measured with and without the maltol, acting as anti-biofilm. A full platform was designed based on


the understanding of the above-mentioned components, used in an optimised process and ratios, depending on the wet wipe producers’ needs and requirements, such as pH preference, viscose fabric composition and more. This patented flexible platform includes several options, each designed to answer a different need. All the systems created by this rational


design provide high efficacy protection at a level of use of 1% and below, with no need for additional boosters, solvents or other preservatives. The systems offer broad-spectrum


protection, with dual protection due to the unique anti-biofilm mechanism, while supporting consumers’ desire for a clean label, a high safety profile and an environmentally friendly composition which is readily biodegradable. The environmental aspect is a growing


concern in the wipes industry, as the companies continue to search for green fabric alternatives, and global regulatory aspects are starting to emerge with regard to plastic.


The preservation systems described here


are expanding even beyond viscose fibres and have the ability to answer the same need for manufacturers working with pulp based wipes, which is an already growing segment, and has similar preservation obstacles.


Conclusion In conclusion, we find that identifying the real and hidden obstacles of wet wipes composition are the key to understand the preservation challenge. With this new understanding we now have


the keys to unlock the door and bring new preservation systems designed specifically for the unique and challenging industry of wet wipes.


PC


No treatment Figure 6: Challenge test results for wipe preservation system PERSONAL CARE February 2022


Hydrophilic preservative


Figure 7: Impact of anti-biofilm formation www.personalcaremagazine.com


Hydrophilic preservative+


anti-biofilm agent


O.D.


Inoculum Day 2


Day 7


Day 14


Day 21


Day 28


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