DIRECT MEASUREMENT OF LIP PRESSURE WHEN INGESTING SEMI-LIQUID FOOD

A spoon sensor to measure lip pressure when slurping liquid food was developed. Several sheet‐type sensors of 3 mm diameter were aligned along the back‐center line of the bowl of a spoon, at intervals of 5 mm and the lip pressure was evaluated while average adults ingested five samples of semi‐liquid foods with varying viscosities. Samples with greater viscosity required correspondingly greater lip pressure and maximum force, as well as a greater impulse or time integral of the force detected by a single sensor. The sum of the force, the impulse, duration and velocity using pressure data from a sequence of four sensors were calculated. Thicker samples required greater force and impulse, and longer duration, but lower velocity. The test subjects slurped semi‐liquid foods differently, adapting to viscosity. Mechanoreceptors in the lips may play an important role in the discrimination of food viscosity.