Testing and Developing a Sugar-derived Surfactant Blend for Delicate Skin

Jul 1, 2014 | Contact Author | By: Luigi Rigano, PhD, and Nicola Lionetti, Rigano Industrial Consulting and Research, Milan, Italy; Adriana Bonfigli, PhD, ISPE Srl, Milan, Italy; Giambattista Rastrelli, PhD, Kalichem Italia Srl, Botticino Sera, Brescia, Italy; and Andrea Baratto, Unifarco Srl, Santa Giustina, Belluno, Italy
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Title: Testing and Developing a Sugar-derived Surfactant Blend for Delicate Skin
sustainablex surfactantx olivex coconutx mildx amino acidx
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Keywords: sustainable | surfactant | olive | coconut | mild | amino acid

Abstract: Vegetable-derived, mild and sustainable skin cleansing ingredients are in demand, and this has led to the development of new detergent structures. Described here is a combination of two mild surfactants that fulfils these requirements using the concept of “interrupted soap” to impart mildness. Studies to verify the functional, sensorial and mild characteristics of the new blend are detailed.

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L Rigano et al, Testing and Developing a Sugar-derived Surfactant Blend for Delicate Skin, Cosm & Toil 129(6) 30-41 (Jul/Aug 2014)

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New approaches to skin cleansing are gaining interest, and modern concepts for wellness respect the body’s and skin’s equilibrium, along with the environment—hence, the wide success of natural ingredients. This has led to the development of new detergent structures for improved benefits. To develop a new, wellness-inspired raw material, the authors began their search with vegetable oils, waxes and vegetal actives.

Choices of vegetable-derived, eco-friendly and mild surfactants are abundant, but, unfortunately, often do not match the level of functionality and exhibit the desirable sensory characteristics of synthetic ingredients. Further, many are incompatible with polymers, conditioning ingredients and traditional surfactants. They also have difficulty in reaching high viscosity values or, in some cases, even reaching a minimum viscosity. There are also too few options for transparent formulae. From a sensory standpoint, the main issues with vegetable-derived and mild surfactants are their foam quality, quantity and stability—key sensory factors for consumers. So, to guarantee a product’s shelf-life and preserve its sensory characteristics, the authors’ search was extended to other ingredient categories.

Beginning with olive and coconut oil fatty chains, sugars from fruits and amino acids, years of systematic trials culminated in a combination of specialized amino acid-fructoside surfactants: olivoyl/cocoyl fructoside (a non-ionic) and sodium olivoyl/cocoyl tetra amino acid (an anionic). This paper will describe the basis for this combination and detail tests conducted to verify the functional, sensorial and mildness characteristics.

Non-ionic/Anionic Blend

Non-ionic portion: The lipid structures of olivoyl/cocoyl fructosides are made up of the natural chain blends present in olive and coconut oils. Olive oil was selected for its high amount of mono-unsaturated fatty acids (75%) and because it is well-known for its compatibility with the human body. Moreover, its lipid moiety contributes emollient effects, normalizing and protecting skin. Coconut oil, also widely used for its emollient properties, has been found to moisturize atopically dermatitic skin while also removing Staphylococcus aureus. This effect is probably due to its lauric acid, which is known to kill bacteria and fungi.

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Table 1. Rank sum obtained for each test sample

Table 1. Rank sum obtained for each test sample

The rank sums obtained for each sample; the greater the value, the better the performance

Table 2. Paired comparison between rank sums for hair brightness

Table 2. Paired comparison between rank sums for hair brightness

On the basis of this calculated LSD value, at a 0.05 α-risk level, a paired comparison between the rank sums of the samples was performed. Results are shown here.

Table 3. Paired comparison between rank sums for hair softness

Table 3. Paired comparison between rank sums for hair softness

On the basis of this calculated LSD value, at a 0.05 α-risk level, a paired comparison between the rank sums of the samples was performed. Results are shown here.

Figure 1. Chemical structure of the non-ionic olivoyl/cocoyl fructoside

Figure 1. Chemical structure of the non-ionic olivoyl/cocoyl fructoside

To achieve mildness while retaining high efficiency in terms of foaming capacity, compatibility and ease of thickening, the authors engineered hydrophilic heads by esterifying the fatty acid chains with the molecules of fructose.

Figure 2. Chemical structure of sodium olivoyl/cocoyl tetra amino acid

Figure 2. Chemical structure of sodium olivoyl/cocoyl tetra amino acid

Four amino acids were finally selected and tested as possible chain extenders: valine (non-polar), alanine (non-polar), threonine and glycine (both polar). These four belong to the standard amino acid family; threonine and valine specifically are essential amino acids.

Figure 3. Four amino acids selected for the hydrophilic heads

Figure 3. Four amino acids selected for the hydrophilic heads

Four amino acids were finally selected and tested as possible chain extenders: valine (non-polar), alanine (non-polar), threonine and glycine (both polar). These four belong to the standard amino acid family; threonine and valine specifically are essential amino acids.

Figure 4. Foam height values and stability for the OF blend with each surfactant

Figure 4. Foam height values and stability for the OF blend with each surfactant

Foam height values at T0 and T1 (columns) and stability (yellow line) for the new OF blend with each surfactant: a) SLES, b) DCA, c) DLS, d) CG and e) PGC

Figure 5. Foam height values and their stability for surfactants from the foam tests, and ternary mixtures

Figure 5. Foam height values and their stability for surfactants from the foam tests, and ternary mixtures

Foam height values at T0 and T1 (columns) and its stability (yellow line) for surfactants from the foam tests, and ternary mixtures with SLES at 60% as the primary surfactant, and OF and other surfactants as secondary surfactants at 20% each

Figure 6. Behavior of a 14% active solution with increasing amounts of sodium chloride

Figure 6. Behavior of a 14% active solution with increasing amounts of sodium chloride

The viscosity behavior of the new blend with increasing amounts of NaCl; results with the other two salts, MgCl2 and CaCl2, are not reported due to compatibility issues

Figure 7. Performance of five different thickeners tested at different percentages

Figure 7. Performance of five different thickeners tested at different percentages

The performance of other thickening ingredients were also evaluated, the results of which are reported here.

Figure 8. Viscosity values for compared surfactants in a binary system

Figure 8. Viscosity values

Viscosity values for the compared surfactants (14% active) in a binary system with OF at different ratios

Figure 9. Viscosity values for compared surfactants in ternary mixtures

Figure 9. Viscosity values for compared surfactants in ternary mixtures

Viscosity values for the compared surfactants (14% active) in ternary mixtures with SLES at 60%, and OF and other surfactants at 20% each

Figure 10. TEWL values before and after washing

Figure 10. TEWL values before and after washing

TEWL values before and after washing with the two solutions and with tap water

Figure 11. pH values before and after washing

Figure 11. pH values before and after washing

pH values before and after washing with the two solutions and with tap water

Figure 12. Skin redness, a* value, before and after washing

Figure 12. Skin redness, <em>a*</em> value, before and after washing

Skin redness, a* value, before and after washing with the two solutions and with tap water

Figure 13. Q value for SLES, OF and their combination

Figure 13. Q value for SLES, OF and their combination

Similar to the previous tests, the results of the Het-Cam test show the OF blend improved the effect of SLES on the skin.

Footnotes [Rigano 129(6)]

a Olivoil Fruttoside (INCI: Sodium Olivoyl/Cocoyl Aminoacids Fructoside (and) Water (aqua)), Kalichem Srl

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