The role of particle size distribution of suspended solids in defining theflow properties of milk chocolate

The flow characteristics of molten milk chocolate, like most dense suspensi ons, an a function of the maximum packing fraction (phi(m)) of the suspende d solids. Milk chocolates were prepared from mixtures of two relatively nar row coarse (d(4,3) = 17 mu m) and fine (d(4,3) = 8.5 mu m) size distributio ns of non-fat solids to contain 0, 25, 50, 75, and 100% of the coarse compo nent. Solids bed density (a measure of maximum packing fraction) correlated with the apparent viscosity of milk chocolates (r = -0.98). The highest va lue for solids bed density and lowest value for apparent viscosity were mea sured for size distributions with 75% of solids from the coarse fraction. C asson yield value correlated with d(4,3) (r = -0.98) and specific surface a rea (r = 0.93). The maximum packing fraction of binary mixtures of two dist inct sizes of non-fat chocolate solids attained a maximum value for a speci fic volume ratio of the components. The maximum in phi(m) corresponded with the minimum viscosity in molten chocolate at a given solids volume concent ration.