Rheological and microstructural characterization of wheat dough formulated with high levels of resistant starch

Abstract

Fiber-enriched breads can contribute to increasing the daily fiber intake. Resistant starches (RS) are a useful resource to increase the amount of non-digestible carbohydrates while preserving as far as possible the technological quality of white bread. The effects of high concentrations of Hi-Maize (HM), a type 2 RS, in dough formulations were analyzed by farinograph, dynamic rheometric assays, texture profile analysis, and 1H-NMR relaxation measurements and related to particle size and microstructural characteristics studied by different microscopy techniques (SEM, ESEM, CLSM). Up to 30% replacement with HM was performed. Water absorption increased and development time and stability decreased when the amount of HM increased. Water mobility increased suggesting a change in water binding. The mechanical spectra indicated a prevalence of the solid-like character in all samples, but the G′ (storage modulus) vs. G″ (loss modulus) plot suggested a pronounced change in the microstructure of dough at the highest level of replacement. Dough was harder, more adhesive, and less resilient when the HM content was increased. The use of HM in the premix formulations not only diluted the gluten content but also changed the size particle distribution of starch granules by increasing the fraction with smaller sizes. Thus, more compact matrices were obtained with a noticeable disruption of the gluten network at the highest level of replacement. However, an intermediate level of RS addition (20%) still rendered a dough with satisfactory rheological properties for breadmaking.