title: Comparison between sensory and instrumental characterization of topical formulations: impact of thickening agents.
abstract: OBJECTIVE
  Sensorial properties of cutaneous formulations are important in determining their acceptability by consumers. However, sensorial analysis is time-consuming and requires an available panel of trained assessors. Thus, this article aimed to study the impact of thickening agents on mechanical properties of creams and investigate how these measurements could correlate the sensory attributes using a combined instrumental-sensorial approach.
  
  
  METHODS
  For this purpose, eight semisolid formulations were prepared, containing in their composition different thickening agents at different concentrations. These formulations were firstly microscopically observed and then assayed through textural, rheological and spreadability measurements. Textural characterization and rheological characterization were performed during six months to assess the physical stability of the studied formulations. Finally, six sensory attributes, namely firmness, adhesiveness, cohesiveness, spreadability, consistency and adhesiveness post-application, were tested by a trained panel.
  
  
  RESULTS
  It was observed that thickening agents influence the microstructure of semisolid emulsions and also their mechanical properties. In general, an increase in the concentration of thickening agents improves the physical stability of formulations over time. Besides, textural parameters (firmness and adhesiveness), viscosity and difficulty to spread also increase. A good correlation between mechanical characterization and sensorial analysis was verified, mainly for spreadability properties.
  
  
  CONCLUSIONS
  With the obtained results, it is possible to conclude that the proposed methods for mechanical characterization can be correlated with sensorial perception obtained from volunteers, representing a faster and less expensive alternative than sensory analysis.
authors.affiliation: Laboratory of Pharmaceutical Technology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Porto, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Estanqueiro
authors.affiliation: Laboratory of Pharmaceutical Technology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Porto, Portugal.
authors.forename: M H
authors.initials: MH
authors.lastname: Amaral
authors.affiliation: Laboratory of Pharmaceutical Technology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Porto, Portugal.
authors.forename: J M
authors.initials: JM
authors.lastname: Sousa Lobo
mesh_terms: D000279:Administration, Cutaneous; D002626:Chemistry, Pharmaceutical; D003258:Consumer Behavior; D003358:Cosmetics; D004655:Emulsions; D006801:Humans; D009812:Odorants; D012212:Rheology
chemical_list: D003358:Cosmetics; D004655:Emulsions
keywords: adhesiveness; firmness; rheology; sensorial analysis; spreadability; thickeners