Quinoa starch particles as a new technology to stabilize and encapsulate lipophilic components using a Pickering route
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Presented by: Audrey Maniere
In the cosmetic area, new pathways in formulation lead to breakthrough innovations in texture, tolerance and sustainability aspects. The use of particles to stabilize emulsions, labelled Pickering emulsions, has been extensively studied over the years but this approach is not yet widely implemented by cosmetic formulators for various reasons related to material features, the process of use or unwanted side effects.
Quinoa starch is a cutting-edge material acting as a new ingredient platform delivering several functionalities with a surfactant-free approach. Compared to most starches, it has a very small granule size of 1–2 µm and through chemical or physical modification, starch granules can be made more hydrophobic, which gives it a higher affinity for the oil/water interface than its native counterpart. In addition, thanks to gelatinization properties of the starch, particles swell and fuse at the interface to produce a barrier. Thereby, quinoa starch particles are not only suitable to form Pickering emulsions but also to create core-shell structures for micro-encapsulation purposes, while inducing a very soft and powdery skin feel. Although academic papers have been already published on quinoa starch stabilized emulsions, studying the influence of hydrophobic modification or particle concentration as a proof of concept, it was not carried out in a real cosmetic formulation environment.
The aim of this work was to evaluate the potential of a chemically modified quinoa starch as emulsifier, by investigating the relationships between its physico-chemical features and performances, and also assessing its behavior in cosmetic OW emulsions.
First, to identify critical parameters affecting the performance of the material, different pilot batches of modified quinoa starch powders were deeply characterized by chemical analysis and physico-chemical techniques such as electronic microscopy, particle size, DSC or wettability measurements. Then, cosmetic emulsions stabilized with modified quinoa starch were formulated at different scales and its microstructures with others traditional ingredients like gelling agent and surfactants were explored. In parallel, the created emulsions were evaluated on sensorial, tolerance, moisturizing effect, and visual benefits on skin compared to surfactant-based emulsions.
Our results indicated that the starch degree of substitution measured by NMR-H was strongly correlated to the hydrophobicity of the particles, easily recognized by a shift in gelatinization temperature. This impacted consequently the emulsifying properties, in addition to more complex parameters such as residuals content which can prevent a homogenous grafting. Moreover, the drying method affected drastically the aggregation of the powder highlighting the importance of the particles individualization for efficient interface absorption. Furthermore, confocal microscopy pictures showed that the idealized model involving a monolayer of starch surrounding droplets was not always achieved and the particles were weakly flocculated to some extent, depending on the compositions. Formulation routes investigations emphasized the interest of hybrid particle/surfactant system which enables obtaining thinner simple emulsions, and on the top of that, highly stable multiple WOW emulsions. Globally, the emulsions exhibit unique powdery and evanescent sensory signature while providing less irritating impact than classical ones.
In addition to better understand the key factors affecting the stability of Pickering emulsions, we showed that the modified Quinoa starch particles have to be finely tuned to fit with the cosmetic expectations. Once set up, we easily produced at laboratory and pilot scale, highly stable emulsions with unique attributes leading to new sensorial and mild products. What is more, this technology shows abilities to create a sealed barrier which will allow the encapsulation of oily component opening many possibilities of additional applications.
Quinoa starch is a cutting-edge material acting as a new ingredient platform delivering several functionalities with a surfactant-free approach. Compared to most starches, it has a very small granule size of 1–2 µm and through chemical or physical modification, starch granules can be made more hydrophobic, which gives it a higher affinity for the oil/water interface than its native counterpart. In addition, thanks to gelatinization properties of the starch, particles swell and fuse at the interface to produce a barrier. Thereby, quinoa starch particles are not only suitable to form Pickering emulsions but also to create core-shell structures for micro-encapsulation purposes, while inducing a very soft and powdery skin feel. Although academic papers have been already published on quinoa starch stabilized emulsions, studying the influence of hydrophobic modification or particle concentration as a proof of concept, it was not carried out in a real cosmetic formulation environment.
The aim of this work was to evaluate the potential of a chemically modified quinoa starch as emulsifier, by investigating the relationships between its physico-chemical features and performances, and also assessing its behavior in cosmetic OW emulsions.
First, to identify critical parameters affecting the performance of the material, different pilot batches of modified quinoa starch powders were deeply characterized by chemical analysis and physico-chemical techniques such as electronic microscopy, particle size, DSC or wettability measurements. Then, cosmetic emulsions stabilized with modified quinoa starch were formulated at different scales and its microstructures with others traditional ingredients like gelling agent and surfactants were explored. In parallel, the created emulsions were evaluated on sensorial, tolerance, moisturizing effect, and visual benefits on skin compared to surfactant-based emulsions.
Our results indicated that the starch degree of substitution measured by NMR-H was strongly correlated to the hydrophobicity of the particles, easily recognized by a shift in gelatinization temperature. This impacted consequently the emulsifying properties, in addition to more complex parameters such as residuals content which can prevent a homogenous grafting. Moreover, the drying method affected drastically the aggregation of the powder highlighting the importance of the particles individualization for efficient interface absorption. Furthermore, confocal microscopy pictures showed that the idealized model involving a monolayer of starch surrounding droplets was not always achieved and the particles were weakly flocculated to some extent, depending on the compositions. Formulation routes investigations emphasized the interest of hybrid particle/surfactant system which enables obtaining thinner simple emulsions, and on the top of that, highly stable multiple WOW emulsions. Globally, the emulsions exhibit unique powdery and evanescent sensory signature while providing less irritating impact than classical ones.
In addition to better understand the key factors affecting the stability of Pickering emulsions, we showed that the modified Quinoa starch particles have to be finely tuned to fit with the cosmetic expectations. Once set up, we easily produced at laboratory and pilot scale, highly stable emulsions with unique attributes leading to new sensorial and mild products. What is more, this technology shows abilities to create a sealed barrier which will allow the encapsulation of oily component opening many possibilities of additional applications.