Influence of the emollient on emulsions containing lamellar liquid crystals: from molecular organization towards applicative properties

Abstract

OBJECTIVE: The sensory perception of cosmetic emulsions is complex as it is governed by an important number of parameters like the choice of raw materials, their interactions, the structural organisation of the system, etc. The aim of the present work was to go further in the interpretation of the emollient-surfactant interactions, towards the emulsions applicative properties. For this purpose, two systems containing liquid crystals of the lamellar type were formulated, differing only in the selected emollient. METHODS: First, the liquid crystals types were checked using different tools like the optical microscopy under the bright and polarized light, the wide-angle X rays diffraction and, finally, thermogravimetric analysis. Next, two sensory attributes, namely compression force and difficulty of spreading, were evaluated by a sensory panel. In addition to that, complementary instrumental characterizations (flow tests, textural analysis and contact angle measurements) were performed in order to understand how the panel could discriminate the products. RESULTS: The results showed that isohexadecane emollient induces the a-gel structures, while caprylic capric triglycerides favour the formation of the lamellar liquid crystals near to a-gel. For the compression force, the results point out that there is no direct interaction between the oil phase and the skin. For this attribute, depending on its chemical structure, emollient impacts the human perception only by changing the lamellar phase type. Concerning the difficulty of spreading, both the emulsion structure and the emollient properties should be considered. Immediate perception is impacted by the emulsions destruction, making the droplet roll one on each other. Then, once the droplets monolayer is disrupted, the emollient comes into direct contact with the skin. In this case, the perception is governed by the direct affinity of the emollient with the skin, nonpolar emollients being easier to spread if compared to polar ones. CONCLUSION: The sensory perception is guided not only by the choice of the raw materials but also by their interactions. It was shown that the chemical structure of the emollients affected the molecular organization of liquid crystals present in the emulsion and, consequently, directly or indirectly its sensory perception.

Sensory perception of textural properties of cosmetic Pickering emulsions

“…2). The important SD for the obtained results is usual for the sensory analysis inherent to differences in assessors evaluation [26][27][28][29]. Despite the identic water quantity in all the samples, the panel could statistically discriminate the products.…”

“…The sensory analysis is essential when developing products with further applicative interest. It was largely described for cosmetic raw materials and emulsions , but only a few results were given for Pickering emulsions. Marto et al .…”

“…The sensory analysis is essential when developing products with further applicative interest. It was largely described for cosmetic raw materials and emulsions [24][25][26][27][28][29], but only a few results were given for Pickering emulsions. Marto et al [4] evaluated the textural properties of the Starch-based emulsions using a simple sensory questionnaire in which the basic characteristics, that is texture and skin feel, were evaluated by the volunteers.…”

Stabilization of vitamin C in emulsions of liquid crystalline structures

“…It comes from crystallization of the fatty chains of mixed cetyl alcohol and Polysorbate 60. The position of the unique Bragg peak is typical the hexagonal packing of hydrophobic chains [Savic et al, 2011;Oliveira et al, 2013;Wunsch et al, 2015;Terescenco et al, 2018c]. This phase has been called -gel (or rotator phase, or L).…”

Sensory evaluation in the personal care space: A review

“…These methods are at the discretion of the researcher and should be chosen to fit the study objectives, resources, and sample products.As with food and beverage, the sensory perception of personal care products is based not only on the ingredients or raw materials, but on the potential synergies and/or opposing effects they may produce. This concept was demonstrated byTerescenco et al (2018) in a study on sensory perception of emulsions containing different emollients. The differing emollients lead to differences in the sensory perception of the products related to the force needed to compress the sample between the fingers (pick up modality) and the difficulty of spreading the emulsion over the skin (rub out modality; Terescenco et al, 2018).…”