Physicochemical characterisation of the lactoperoxidase system powders: comparison of two drying techniques

A good knowledge of powder flow properties is necessary to consider industrial application of a system. Flowability is a complex combination of different parameters like size, shape or surface properties of particles. The goal of this study is to compare the impact of two drying techniques (freeze-drying and spray drying) on powder flowability in order to choose the most appropriate device. Powder is first studied at the particle level with size measurements and shape description. Then, the global behaviour is characterised by water content, water up-take and physicochemical analysis. Finally, the influences of two additives and of coating on powder flow properties have been investigated. The two powders obtained by spray and freeze-drying vary principally by the shape of the particles. Residual water content, moisturising capacity and surface properties are similar. In both cases, powder flowability is bad. Results obtained with the two additives show no improvement of powder flow properties. However, coating reduces the number of fine particles and, as a consequence, improves powder flowability with furthering particle motion.