Modelling sorption kinetic of sponge cake crumb added with milk syrup

Sponge cake is an ideal product to be soaked with liquids, due to its porous structure; baking process causes differences in crumb features through the cake; therefore, it is important to know how these variations can affect its sorption capacity. The aim of this work was to study the relation between crumb cake structure at different levels (bottom, centre and top) and sorption characteristics when adding milk syrup. The Peleg model was the best to fit sorption data (R² > 0.9), showing that the rate constant (k₁) diminished as the cell density (r = 0.920) and gelatinisation percentage (r = 0.890) decreased, while moisture (r = -0.999) and a_w (r = -0.994) increased; cell density only correlated with gelatinisation percentage (r = 0.997); micrographs showed that the sorption rate increased as more gelatinised starch and coagulated protein were found. To optimise the sorption process, the gelatinisation degree and crumb structure (cell density and types of pores) should be considered.