Description of internal microstructure of agglomerated cereal powders using X-ray microtomography to study of process-structure relationships

Agglomerated food powders are made from native particles which are assembled to form grains. The present investigation seeks to contribute to a better understanding of the three-dimensional internal morphology of food agglomerates (i.e. different couscous grains made from durum wheat semolina under different agglomeration process conditions) by means of microscopic methods (size, compactness) and X-ray micro-computed tomography (XMT), to bring understanding of the process-structure relationships. The three-dimensional internal morphology of food agglomerates was evaluated by means of X-ray micro-computed tomography (XMT), using a tabletop system with a resolution of several micrometers. XMT was considered to evaluate the internal porosity (or void fraction) as well as the size and spatial distribution of pores inside the grains. Closed porosity values ranged between 0.005 and 0.011. Diameter of internal pores was found to range between 13 and 155 mu m which contribute to control mainly their end-properties. The experimental results were discussed to develop a better knowledge of the process-structure relationships for food agglomerates based on wheat powders, produced by wet agglomeration process. We demonstrated that the shearing conditions during the initial mixing stage significantly contribute to the internal structure characteristics of agglomerates. The cooking treatment is found to largely improve the mechanical strength of the agglomerates. (C) 2014 Elsevier B.V. All rights reserved.