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This aim of this study is to prepare four novel oil-in-water creams from 100% naturally sourced oil ingredients such as jojoba, baobab and coconut oil, and compare the effect of the oils on the physico-chemical properties of the creams and their short- and long-term stability. Four 100 g each oil-in-water active containing creams and their controls (without the active ingredient) were formulated and stored in eight separate glass jars. The short-term stability of the creams was assessed via phase separation resistance, pH, microscopic size analysis, globule size, zeta potential, conductivity and microbial challenge evaluation after 8, 14 and 28 days, under three different storage temperature conditions (4 &deg, C, 25 &deg, C and 40 &deg, C) and at ambient relative humidity. Model creams IA, IB, IIA, and IIB containing 1:1 of jojoba and baobab oil mix, all had good shelf-life or stability at the end of the 28 days after storage at 4 &deg, C, compared to models IIIA, IVA and pairs. The long-term stability of creams stored at 25 &deg, C for 28 days, was subsequently assessed using the Dynamic Vapor Sorption system. Model creams IB, IIB, IA and IIA showed the lowest percentage moisture loss or change in mass during a period of desorption steps. Therefore, the creams containing a mixture of jojoba and baobab oils are capable of retaining moisture easily for an extended period of time when compared to the creams containing jojoba and coconut oil or baobab and coconut oil combinations, thus they were proven to be the best products in terms of stability and quality. The stability ranking of the creams using the novel DVS method was in congruence with the results from the short-term stability experiments. This novel DVS method can, therefore, be generically applied in the cosmetic, food and pharmaceutical industries for the evaluation of the long-term stability of semisolids.

The sensory properties of cosmetic products can influence consumers’ choice. The accurate correlation of sensory properties, such as skin hydration, with the material properties of the formulation could be desirable. In this study, we aimed to demonstrate a new method for the in vitro measurement of the refractive indices (RIs) of turbid creams. The critical wavelength of each cream was obtained through direct measurement using a sun protection factor (SPF) meter, the wavelength value was then applied in the Sellmeier equation to determine the RI. The results obtained from the in vitro skin hydration measurement for each cream correlated with their RI values. This suggests that RI measurements could be a useful predictive tool for the ranking of creams in terms of their skin hydration effects.

As the popularity of a cosmetic product on the market extensively depends on consumers&rsquo, perception, it is important for the sensory evaluation to be accurate during the product developmental stage. The focus of this study was to develop a generic method for the quantitative assessment of the sensory attributes of cosmetic creams. Four 100 g oil-in-water (O/W) model creams, containing loaded niosomes and their baselines (without niosomes), were formulated. Quantitative sensory evaluation of the formulated oil-in-water products were performed in three different stages: (a) appearance&mdash, pourability (b) pick-up&mdash, firmness and elasticity/stretchability (c) rub-out&mdash, spreadability and stickiness, using rheological measurements. All measurements were carried out at skin temperature, 32 &plusmn, 1 &deg, C, and a relative humidity (RH) of 33%. The quantitative analysis showed all cream models exhibited shear-thinning, non-Newtonian behavior. Rheological parameters from the yield stress, amplitude sweep and frequency sweep tests were found to provide realistic correlations for the sensory characteristics of pourability and spreadability, firmness, elasticity/stretchability and stickiness, respectively. This novel quantitative assessment method of the sensory characteristics of a cream proved to be highly effective and can be universally applied.