Evaluation of Correlation Between Rheological Characteristics and Consumer Sensorial Perception

Fu Chen, Seher Ozkan, Germain Pucetti, and William Prosise

Ashland Specialty Ingredients, Corporate Research Center, Bridgewater, NJ

INTRODUCTION

It is a continuing endeavor in the oral care industry to attempt to replace subjective consumer sensorial testing with concrete and quantifiable analytical testing techniques. The purpose of this study was to seek potential correlations between toothpastes’ complex rheological characteristics and general consumer perception results during and after brushing. It is envisioned that this might serve as a potential guide for future toothpaste formulation design, based on rheology.

Six commercial toothpastes were evaluated in this study. For rheology evaluations, full and 1:1 and 2:1 water dilutions of toothpastes were characterized using dynamic oscillatory flow, steady torsional flow, continuous shear rate ramp, and compression / extension tests without suppressing wall slip. Diluted formulations were centrifuged and their supernatants’ static surface tension values measured. Shear and extensional viscosity indexes were also characterized by a microcapillary rheometer. For the sensory evaluation segment, 25 untrained panelists were recruited and asked to brush their teeth with commercial toothpastes. Sensory parameters covered perception both during brushing and after brushing, scored by panelists on a 1 to 5 scale. All results were correlated using principle component analysis (PCA) to map the relationships between toothpastes’ rheological characteristics and consumer sensorial perception.

METHODS

RESULTS

Rheology profiles and large amplitude oscillatory flow (LAOS) finger print of 6 commercial toothpaste

Sensory test results before and after brushing

CONCLUSIONS

PCA analysis of correlation between sensory results and toothpaste rheology. a: Thinning ratio of frequency sweep, complex viscosity at w=100rad/s (full formulation vs. 1:1 dilution; b: Thinning ratio of shear viscosity at 1s-1 (1:1 vs. 2:1); c: Cohesive

work; d: Compressive work; f: Shear viscosity at 100s-1 (1:1); h: Strain sweep, tand at 0.1% stra; j: Strain sweep, tand at 100% stra; m: Frequency sweep, tand at w=1rad.

PCA results showed that chalkiness of toothpaste is positively correlated with Strain sweep, tand at 100% stra; Foaming is weakly correlated with cohesive work; Grittiness is weakly correlated with compressive work; and pastiness is also weakly correlated with compressive work. However, due to the low number of samples, more work needs to be done to find more significant correlations. Finally, the large error in sensory results might be reduced by employing trained panelists. This might also result in more significant correlations

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Chalkiness Pastiness Grittiness Body Sliminess Foaming Change in thickness feel

Burning sensation Cooling sensation Slippery feel Clean teeth feel Clean mouth feel Overall Flavor Strength

Colgate Optic White Crest Pro Health Colgate Total Advanced Crest 3D White Arm & Hammer Adv. White Colgate 2in1 During Brushing After Rinsing