AN ANALYTIC PROBABILITY DENSITY FOR PARTICLE-SIZE IN HUMAN MASTICATION

In previous studies the distribution of particles sizes of chewed food has been described by an empirical function. However, at the beginnin g of the chewing process, when many unbroken food particles are still present in the mixture, this function failed to give a good descriptio n. In the present study, formula: were derived to characterize the dis tribution of chewed food particles by size as a function of the number of chewing cycles. The reduction of food particle sizes was considere d to be the composite result of a selection and a breakage process. Bo th processes were described by simple functions. The probability densi ty P-n+1(x) of finding a particle of size x after n + 1 chewing cycles was computed from P-n(x) by selecting a proportion of particles of si ze y from P-n to be converted to particles of size x < y by a breakage function. Measures of central tendency-average, median and most proba ble size-were obtained as a function of the number of chewing cycles. The measures of central tendency characterize the degree of food commi nution during the chewing process and so can be used to quantify chewi ng performance. The comminution of food is described in terms of the s election and breakage functions in a convenient, efficient, analytic w ay, valid for all phases of the chewing process. (C) 1996 Academic Pre ss Limited