Psychophysical and Rheological Investigation of Toothpaste Tube Squeezability: A People-Centric Approach.

In this work, toothpaste tube squeezability was tested by three different methods: assessment by a human panel, a tactile glove, and several purely instrumental tests. The panelists characterized squeezability in terms of the acceptability of the product. The tactile glove was utilized to determine the maximum grip forces (G_F) applied by the same panelists during their assessment. The instrumental tests consisted of emulative tests by a squeezing device and rheological tests. Along with commercial pastes, a series of samples were deliberately formulated and tested, and covered a wide range of squeezability rates of 0.07-2.31 cc/s. The study showed that it is possible to predict human sensory perception using either an emulative squeezing instrument or the rheological measurements of the pastes. The study also suggests that human perception of acceptable squeezability includes not only its low limit (pastes being hard to squeeze) but also its upper limit (pastes perceived as too runny) which may also be related to the inability of the paste to retain its shape on the brush. Based on this study consumer-acceptable ranges of rheological and squeezability parameters were defined. These results are expected to be useful, especially for oral/personal care product developers.