-The transition to local and organic agriculture in the face of climate change is leading to significant variability in agricultural products and a major challenge in managing industrial processing. Plant grains, particularly cereals and legumes, are the focus of many approaches to support the transition to plant-based proteins. Before being consumed, these seeds normally undergo soaking and cooking operations that are still poorly studied, especially by integrating the factor of physical variability of the material. Plant grains characteristics, with their dense episperm and rigid tissues, make water absorption difficult. As a granular material, the impact of morphological diversity of grains (size, shape, color, texture...) in one population on processing behavior has to be investigated. The objective of the present study is to develop several specific analytical methods to describe the dispersion of characteristics of different plant grains, in the dry native form, after hydration and after cooking. The specific analytical methods concern the measurement of color (CIELAB colorimeter), shape (caliper), and texture (texturometer) characteristics. The proposed methods have been tested to be discriminating, with statistical analysis to define the minimum number of grains needed to describe the diversity of the whole population. Results are discussed in relation to the literature on grain variability.