Powder mixing is one of the most common unit operations in industries handling powders. However, due to a lack of scientific knowledge on the behavior of powders inside a mixer, the optimization of a powder mixing step typically involves an experimental lab work in order to be transposed to a larger scale. To simplify this huge work, improving our understanding of the mixing dynamics remains some of the main industrial issues. In this work, the mixing dynamics of an easy flowing powder made of lactose and couscous have been studied in the Turbula (R) mixer T2F. According to process parameters, we focused on the definition of mixing modes and we sought to identify the main mixing and segregation mechanisms at play for each mode, based on the analysis of mixing kinetics and autocorrelation functions. This work is a first step toward the definition of scale-up laws. The ultimate aim is to build predictive models to determine process parameters for obtaining the desired quality of mixing according to powder characteristics, flow properties and industrial constraints. (c) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.