A multi-benefit ingredient for preservation and silicone-free emulsions

Inolex

7 December 2021

A multi-benefit ingredient for preservation and silicone-free emulsions

On the surface, preservatives and silicones have little in common besides famously being targets of the ‘free-from’ and clean beauty movements. Both share consumer scrutiny over concerns of human safety and environmental impact, but from a formulation perspective they generally do not have common functions or performance benefits. As the ingredient toolbox continues to change in response to consumers, retailers, and legislators, opportunities arise for multi-benefit ingredients that address more than one unmet need in formulation design.

The multifunctional challenge

The alternative preservation category, comprised of multifunctional ingredients that replace controversial preservatives like methylparaben or methylisothiazolinone (MIT), has seen a surge in the past decade. Ingredients of choice include caprylyl glycol or ethylhexylglycerin, often paired with a fungicide like sodium benzoate. While effective, safe and consumer accepted, these ingredients are all or mostly petroleum-derived and their multifunctional benefit is often common, e.g. skin conditioning, and supplemented by other ingredients in the formulation. While addressing a significant unmet need for safe and effective preservation, the need for enhanced sustainability is unaddressed and other unmet formulation needs require additional new ingredients to resolve.

The solution: Microbial control meets silicone replacement

Methylheptylglycerin (Lexgard® MHG Natural MB) is an novel, patent-pending chemistry with two distinct benefits:

– Microbial growth inhibition
– Emulsion anti-soaping

This medium chain glyceryl ether is 100% biobased from sustainably sourced feedstocks, readily biodegradable, designed and manufactured with green chemistry, and COSMOS and NATRUE approved. In formulation, it has the unique ability to provide high value benefits in both preservation and emulsion aesthetics, eliminating the need for controversial preservatives and silicones with only one ingredient.

Natural cosmetic preservation effect

Lexgard® MHG Natural MB protects formulations from microbial growth as part of a complete preservation approach that follows the industry convention of Hurdle Technology. This convention uses multiple barriers in formulation and manufacturing to create an environment that is inhospitable to microorganisms, thus preventing their survival and proliferation.

Lexgard® Natural MHG MB is a primary bacteriostatic component providing effective inhibition of bacteria and yeast growth in formulation. Efficacy was demonstrated at a use level of 0.5 – 1.5% (w/w) in multiple formulation types including emulsions, surfactant-based systems, and wipes or sheet mask juice formulations. Efficacy in all of these formulations is defined as meeting the Pass criteria for the S. aureus (bacteria), E. coli (bacteria), P. aeruginosa (bacteria), and C. albicans (yeast) according to the following industry standard preservative efficacy test methods: PCPC, EP-A, and USP51. Broad spectrum preservation effects are possible when Methylheptylglycerin is combined with the fungistatic component Caprylhydroxamic Acid. This combination (Spectrastat™ MHG Natural MB) is a cold processable liquid that is effective from pH 4 - 8.

Natural anti-soaping in emulsions

Methylheptylglycerin helps to reduce or eliminate the soaping or whitening effect often seen during the rub-in phase of emulsion application. It has been shown to reduce or eliminate soaping/whitening in anionic, nonionic, and cationic oil-in-water (O/W) emulsion bases. Traditionally silicones, specifically dimethicones, are used to reduce or eliminate this effect. With Lexgard® MHG Natural MB, formulations that are 100% natural and/or silicone-free with expected superior in-use aesthetics are now possible.

The anti-soaping effect of Lexgard® Natural MHG MB was demonstrated in a cationic emulsion using a graded visual evaluation. The test articles were applied to the volar forearm. Images were collected at the following swipe endpoints: 4, 8, and 12 swipes and then provided to graders for evaluation. The graders scored the amount of soaping in each image on a scale of 0 – 5 where 0 indicates No Soaping and 5 indicates High Soaping.

The following test articles were included in the study: emulsion with 2% (w/w) Lexgard® MHG Natural MB (natural anti-soaping); emulsion with 0.5% (w/w) dimethicone 20cSt (silicone anti-soaping); emulsion with 5% (w/w) dimethicone 20cSt (positive control); emulsion with no anti-soaping agent (negative control). The natural anti-soaping emulsion with 2% (w/w) Lexgard® MHG Natural MB showed less soaping than the silicone anti-soaping emulsion at both the 4 swipes and 8 swipes endpoints. At the 12 swipes endpoint, no soaping was observed with the natural anti-soaping lotion containing Lexgard® Natural MHG MB. This result was statistically equivalent to the positive control with 5% (w/w) dimethicone 20cSt and the silicone anti-soaping emulsion with 0.5% (w/w) dimethicone 20cSt.

The soaping effect was also evaluated by visual graders in an ultra-high soaping anionic emulsion. In this evaluation, a 20 swipes endpoint was added due to the ultra-high soaping quality of the base emulsion. At the 20 wipes endpoint, no soaping was observed with the emulsion containing 2% (w/w) Lexgard® Natural MHG MB while the 2% (w/w) dimethicone 20cSt emulsion still showed a visible soaping effect.

Lexgard® MHG Natural MB is a new innovation in medium chain glyceryl ethers that brings an ingredient to the industry that contains 100% biobased content from sustainably sourced feedstocks, designed and manufactured with green chemistry, and delivers multiple functional formulation benefits in one ingredient. This ingredient advances the industry forward by providing a route to sustainable and natural formulation in two high need areas from one ingredient: microbial control and silicone replacement.

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