COMPARISON OF SIEVING AND LASER DIFFRACTION FOR THE PARTICLE-SIZE MEASUREMENTS OF RAW-MATERIALS USED IN FOODSTUFF

The measurement of particle size and distribution are of paramount imp ortance in assessing feed pellet quality. For many years, dry sieving has been used to characterise the particle size distribution but this technique is time-consuming and has not been modernised. Other particl e sizing methods, more modern, have been developed, such as methods ba sed on light scattering measurements. The laser diffraction technique (based on Fraunhofer diffraction theory) was compared to sieving, the standard procedure. The discrepancies between the two methods seemed t o be attributable to particle shape factors which were dependent on th e size fractions examined. The laser diffraction method thus gave suff icient accuracy when applied to products with a small range of particl e size.