Extending crispness : a systematic approach to controlling water migration in bread

Crispness is one of the most important sensory characteristics of crispy bread, because consumers associate crispness with freshness, wholesomeness, and quality. This sensory sensation, however, is lost within a few hours after baking, because of a fast water uptake of the crust. Therefore, the aim of this thesis was to systematically determine the mechanisms that lead to the fast loss of crispness and to reveal the parameters that are key for crispness retention. We showed that the crust acts as a barrier for water migration, causing water accumulation in the crust. Reducing this barrier property by increasing the water vapor permeability of the crust to an optimal value of 8 × 10–9 g/(m s Pa) resulted in breads with crispness retention that was more than eight times longer. These breads had either channels or cracks in their crust. Despite the changes of the crust properties, these breads had similar crumb softness retention compared to standard breads. The properties of the crumb also affected the water uptake of the crust, but less so than the properties of the crust. Bread containing a crumb with a lower water vapor permeability had a significantly longer crispness retention. Based on these findings, we propose a model that provides a comprehensive view of crispness loss and concluded that the increase in crust permeability is the best way to create breads with a noticeably longer crispness retention.