(W1130-09-60) Temporal Dominance Sensations (TDS) for Topical Skin Products

Purpose: Topical semisolid products evoke a range of sensations when applied to the skin. These sensations can overlap temporally, and understanding the dominant sensation is valuable in establishing the correct order of assessing perceptive sensations. Temporal Dominance Sensations (TDS), a dynamic sensory methodology, investigates dominant sensations of a product during a certain period of time. In food sensory sector, TDS has been extensively employed to support product development and consumer acceptance, across food and beverage industries. However, TDS is quite a new concept to sensory panel studies with topical formulations. The aim of this study was to develop a novel TDS methodology for analysing topical gel products. For this, we used four different gels with carbomer homopolymer (Carbopol® 980P (CBP)) and hydroxyethyl cellulose (HEC). The obtained results will enable a streamlined sensory panel test which takes temporal dominance of each attribute into consideration.

Methods: The TDS analysis was performed with 46 recruited subjects (Ethics ID number: 2020/HE001995). In the first stage, the subjects were trained on the concepts in the TDS test. The selected attributes (cooling sensation and spreadability) and the sensory software program (called as Redjade) were introduced to the subjects. The attributes of TDS were determined from the built list of subjects’ perceived sensations during training period. Specifically, subjects practised applying different gel samples onto their forearm to define the skin-feel and its intensity on a 9-point scale. After the training, subjects participated in the TDS study which was run for 60 seconds per gel sample. Five gel samples with one blinded replicate were used for the test. Subjects immediately started the TDS evaluation after 25 µL of one gel sample was placed onto a marked area (19.6 cm²) of the forearm, where the gel was spread under the rhythm of metronome (60 beats/minute or 1 rotation completion/second) for 60 seconds. During the test, the subjects continuously kept identifying, selecting, and rating the intensity of the dominant sensation perceived until the test ended (at time 60).

Results: The obtained results were plotted as TDS curves showing the dominant attribute against time for each sample. Each curve (Figure 1) represents the dominance (%) as a depiction of the proportion of subjects feeling the sensation as dominant at the time. We found that all the subjects perceived spreadability as the dominant sensation (n = 46) with all examined gels, regardless of the formulation differences and dissimilar physical properties such as polymer concentration (0.25; 0.5 and 1 %), ethanol content (0 and 50 %), and yield stress values (31.8; 0.3; 139.3 and 11 Pa). Cooling sensation was also recorded for all gel samples evaluated, but at a lower magnitude. We postulate that, skin friction created due to product rubbing produces a small amount of heat, possibly leading to a reduction in cooling sensation as compared to spreadability.

Conclusion: Comparing TDS profiles of different gels, spreadability was clearly the dominant sensation during 60 seconds of gel application. TDS can be a well-suited screening method to identify attributes and their temporal placement. As compared to conventional descriptive sensory methodologies, which are time consuming and need to be repeated for each time point and perception, TDS offers comparable information, faster. This dynamic sensory technique also allows the evaluation of multiple sensorial perceptions simultaneously. When optimised, TDS can be a useful test combining the value of the static multidimensional methods and dynamic time-intensity analysis.

Figure 1. Temporal Dominance Sensations (TDS) profiles of carbomer homopolymer (Carbopol® 980P (CBP)) and hydroxyethyl cellulose (HEC) topical gels. Y-axis presents the dominance (%) as a depiction of the proportion of subjects feeling the sensation as dominant at the time. X-axis is the test time – 60 seconds in %.