MECASTARCH

 This mechanism, known to occur in excess water, could occur concomittantly to amylose release (which is responsible for viscosity increase in bread dough). In addition to the effect of the amylose leaching in the stabilisation of the gas cell walls, granule softening would alleviate the strain exerted on the gluten in the gas cell walls upon extension and hence contribute to delay the rupture in the gas cell walls, which governs the final crumb texture (Grenier et al., 2021 doi: 10.1016/j.tifs.2021.01.032). This investigation is part of wider research on the formation of the crumb structure and studied in Magnetic Resonance Imaging at the lab, with a contribution to the study of the microscale mechanisms governing this formation (Dedey et al., 2021 doi: 10.1016/j.jfoodeng.2021.110669). The question was “to what extent can starches compensate the role played by wheat gluten in the stabilization of GCW during baking?”
 

This research was based on structural analysis of starch (normal and waxy wheat and rice) combined to the characterisation of mechanical properties of moderately hydrated starch (elasticity and viscosity) and the morphology of starch granules emprisonned in the more or less thin gas cell walls of dough and crumb. Mechanical testing was performed through compression-relaxation test using the method developped by Laridon et al. in 2015 (doi: 10.1122/1.4922221) to estimate elasticity and viscosity. Confol Laser Scanning Microscopy combined to staining of the protein fraction by Alexa was retained for accessing in 3D the morphology of starch granules by contrast. 
This research conducted at OPAALE research unit benefited from the collaboration of BIA research unit INRAE Nantes FR - and the APEX platform (UMR PANTHER Nantes FR) and from the Marie Curie grant for the fellowship of Nanci Castanha da Silva (under grant agreement 101024420).
First results are available in the following paper (doi: 10.1038/s41598-023-39797-w, also see Figure 1) and three other scientific papers will follow. 

Figure 1. Gas cell walls in a wheat bread dough at the end of fermentation observed using label-free multi-photon microscopy. Second harmonic generation (SHG, cyan/magenta) and two-photon excitation fluorescence (TPEF, green) were combined to image, respectively, the starch granules and the gluten matrix, the two main constituents of wheat flour. Image performed at INRAE, ONIRIS, UMR703 PAnTher, APEX platform, F-44307, Nantes, France. Authorship: Nanci Castanha; Tiphaine Lucas; Laurence Dubreil

Contact : Tiphaine Lucas - Coordinator