Impacts of the baking heating rate on the water mobility, starch microstructure and mechanical properties of degassed crumb during staling

Abstract In this study, the impacts of different heating rates (HRs) from 6 to 40 °C/min were investigated in terms of the 1H proton water mobility, starch microstructure, texture, soluble amylose (AM), amylopectin (AP) retrogradation and AM crystallization during staling. A degassed breadcrumb baked in a miniaturized baking system was used to ensure better time-temperature control during baking. Proton nuclear magnetic resonance (1H NMR) data showed that the evolution of the proton T2 relaxation time decreased with increasing HR during staling. The amount of soluble AM, AP retrogradation degree, AM crystallization degree and crumb firmness tend to increase at higher HR. Environmental scanning electron microscopy (ESEM) observations showed that most starch granules in crumbs treated at higher HR exhibited strong deformation and disruption. These results confirmed that the increase in crumb firmness during staling with increasing HR was related to a higher level of starch disruption. This yielded a higher degree of separation between the AM and AP, which resulted in more pronounced water trapping in the starch crystals. The resulting dehydration of the matrix (gluten network, with AM gel surrounding of starch granules) yielded a loss in crumb softness, and crumb baked at higher HR tended to have a firmer texture and faster staling.