Predicting lipstick sensory properties with laboratory tests.

OBJECTIVE: Sensory perceptions and performance are important to the success of a lipstick formulation, but in vivo evaluation can be expensive and time-consuming. The goal of this work was to develop and use laboratory test methods to predict the sensory and performance properties of lipstick.

METHODS: Twelve model lipstick formulations were prepared, in which only the emollient varied, resulting in a variety of sensory and performance properties. The lipsticks were tested for sensory perceptions of spreadability, stickiness, opacity and gloss with a nine-person panel. The performance properties were evaluated with a friction test using a CETR UMT-2 tribometer, an application test using an analytical balance, a tack test using a Texture Analyser TA.XT-Plus and a colour development/retention test using photography and image analysis. The results of the laboratory tests were compared with the results of the sensory panel using statistical modelling.

RESULTS: The results of the laboratory tests correlated well with the measured sensory properties. The results of the friction test classified the lipsticks into four groups, which were termed oily, creamy, waxy and sticky; these classifications were also evident in the other laboratory test data. Surprisingly, it was found that the friction test could be used alone to predict all the measured sensory properties with statistical models. The correlation between the coefficient of friction and the measured sensory properties is explained by the balance of adhesive and cohesive properties of the lipstick. These properties are influenced by the emollient and affect the application properties and resulting film.

CONCLUSION: The emollient has a significant effect on the sensory and performance properties of a lipstick, which can be predicted with the developed laboratory tests. Furthermore, the friction test can be used to sufficiently predict four important lipstick sensory attributes: spreadability, stickiness, opacity and gloss. Using the methods presented here, lipstick formulations may be more rapidly developed and optimized.