Surface mechanical properties in fresh bread and during storage are greatly affected by the water plasticizing effect. However, the incidence of steaming during baking on the crust mechanical properties remains still unclear. The impact of the amount of steam (100, 200 and 400 ml) during baking on the crust features and water diffusivity was investigated. The amount of steam significantly (p < 0.05) affected the crust colour, glossiness and mechanical properties. An increase in the amount of steam led to reduced colour, failure force and failure firmness, whereas increased glossiness. Water vapour transfer rate and water vapour permeability of the bread crust significantly decreased when increasing the amount of steam applied during baking. Crust microstructure studies carried out by scanning electron microscopy and X-ray microtomography confirmed that the amount of steam greatly affected the surface starch gelatinization and also the protein-starch network. (C) 2011 Elsevier Ltd. All rights reserved.