La granulométrie de l'aliment: Principe, mesure et obtention

Abstract

Particle size analysis is the study of the size distribution of the particles of a powdery material. This fundamental characteristic has close relationships with key-processes such as grinding, fractionation and mixing. In addition, size distribution is related to feeding behaviour and digestion of the feed particles by animals. Since the particles have irregular shapes, size measurement is defined as the diameter of the theoretical sphere whose behaviour is similar to that of the real particle. Such a sphere is called «equivalent sphere». The distribution is then fitted to theoretical laws. The fineness of the meal is described by the median diameter or the mean diameter and the heterogeneity of the distribution by the span or the standard deviation. Among the main techniques commonly used are sieving (in dry or wet conditions), laser light diffraction and imaging. These last two techniques are non invasive and fast techniques which can be used on-line. Particle size measurement depends on the texture and moisture of the granular raw materials which have to be ground. It can be controlled by grinding or fractionation parameters in order to adjust the average size and heterogeneity to nutritional purposes.