Valorisation of bread surplus as ingredients: impact of milling on bread powders properties

Unsold bread in bakeries represents a significant amount of food waste in France. While surplus bread valorisation by fermentation has been widely studied, only few works has been done on their use as powders as food ingredients. The aim aims of this work is are to study the impact of milling conditions of surplus bread on the properties of surplus bread powders using a powder engineering approach. It also seeks to describe the relationships between the powders properties of these powders and to discuss the fracture mechanisms of the bread matrix during the milling process. In this study, French “baguettes tradition type” were milled using a stone mill or a cutting mill, under different conditions to study the influence of the settings of each mill. The results demonstrated that bread powder produced on stone mill are finer (d 50 = 187 μm) than bread powder produced on cutting mill (d 50 = 339 μm). The linear effect of rotation speed and the millstone gap on bread powder properties were high. A positive non-linear correlation was used to discuss the relationships between the particles sizes distribution and powder poured bulk density. The hydration properties of bread powders partly depends on the milling conditions of surplus bread.