A comparison between sieving and optical scanning for the determination of particle size distributions obtained by mastication in man.

Mixtures of particles of different sizes, as obtained after chewing, were analysed. Coarse, medium and fine mixtures of particles of an artificial (Optosil) test food were used. Mixtures of Optosil particles of known form and size (half-cubes) were used to validate the analytical methods. The results of both methods were described by particle size distributions based on the volume of the particles. Complete agreement between methods was found for the mixtures of half-cubes. In order to determine the median particle size by volume from the results of optical scanning an assumption on the form of the chewed particles had to be made. Using the assumption that, on average, the particles resemble spheres a slight overestimate of the median particle size was obtained for scanning as compared to sieving. It can be concluded that, although different aspects of the fragmented particles are measured, sieving and optical scanning are both adequate methods for quantifying mixtures of chewed food particles and yield similar results for the degree of particle size reduction.