Microscopic analysis of gluten network development under shear load—combining confocal laser scanning microscopy with rheometry

Abstract

A comprehensive in‐situ analysis of the developing gluten network during kneading is still a gap in cereal science. With an in‐line microscale shear kneading and measuring setup in a conventional rheometer, a first step was taken in previous works toward fully comprehensible gluten network development evaluation. In this work, this setup was extended by an in‐situ optical analysis of the evolving gluten network. By connecting a laser scanning microscope with a conventional rheometer, the evaluation of the rheological and optical protein network evolution was possible. An image processing tool for analyzing the protein network was applied for evaluating the gluten network development in a wheat dough during the shear kneading process. This network evaluation was possible without interruption or invasive sample transfer comparing it to former approaches. The shear kneading system was able to produce a fully developed dough matrix within 125% of the reference dough development time in a classical kneader. The calculated network connectivity values from frequency testing ranged over all samples was in good agreement with traditional kneaded wheat dough just over peak consistency.

Structure Strengthening Phenomena of Gluten Matrices under Different Stress Types

“…For all experiments, commercial wheat flours type 0 and type 00 provided by Rieper AG, Vintl, Italy were used. The composition (see Table 1) was previously analyzed [16,18,19].…”

“…Therefore, the higher protein content enabled the dough matrix to withstand deformation better and led to a stronger network. The reason for this behavior may be that stronger flours and the resulting stronger doughs tend to contain more HMWs [19]. Therefore, the strength of the secondary forces is higher due to the larger chains, and these doughs need higher shearing to stretch the gluten molecules to the maximum and cause bond scission or the opening of entanglements [32].…”

“…The evaluated shear-stressinduced structure strengthening testing method could be an additional tool to evaluate flour and dough properties in line with a conventional rheometer. With respect to the previous work of Vidal et al [16,18,19], microstructural evolution and flour properties were linked with dough processing behavior. Taking a broad overview of baking-performancedetermining attributes into account, correlations between these flour and dough properties were revealed.…”