The Role of Molecular and Structural Characteristics of Starch, Hydrocolloids, and Gluten in Bread In Vitro Digestibility

Abstract

Starch is one of the leading nutritional carbohydrates in the human diet; its characteristics, such as digestion rate, depend on molecular structure, and in particular, the molecular composition, type and length of amylopectin chains, which are known to present a parabolic behavior with respect to digestion rate. Amylopectin with a higher density of small branches (Chains A) and those abundant in long chains (B2/B3) often present a marked resistance to digestion and could be a challenge in bread production since both fermentation and digestion could be further modulated in the presence of hydrocolloids or gluten. The objective of this work was to analyze different mixtures of starches (rice, potato, and corn) with hydrocolloids (guar and xanthan gum) and vital gluten to understand the relationship between chain length and molecular characteristics with respect to speed of digestion and glycemic index, and their incorporation into a bread loaf at 50 and 100% wheat flour substitution. A Plackett–Burman design was used to design the mixtures. Mixtures were characterized in terms of amylose/amylopectin content, fast, slow, and resistant (SDS, RS) starch digestion fractions, in vitro glycemic index, molecular weight (Mw), radius of gyration (Rz) of amylopectin, chain length distribution, and textural analysis. In the bread, a tendency to increase the SDS was observed when the mixtures included rice or potato, which can be related to the relationship between Mw and size and the prevalence of B2 and B3 chains. The Rz and RS content were related to average chain size and amylose content. The use of vital gluten was a determinant in achieving volume and textural characteristics in the final products and significantly affected the proportions of SDS and RS. By combining the molecular characteristics of starch with hydrocolloids, we can obtain food ingredients for specific applications, such as gluten-free products.

Keywords

• bread
• amylopectin
• glycemic index
• hydrocolloids