Effects of dry heat treatment temperature on the structure of wheat flour and starch in vitro digestibility of bread

The effects of the dry heat treatment (DHT) temperature (20, 50, 100, 150, 200 degrees C) on the structure of wheat flour and on the texture and in vitro starch digestibility of breads were investigated. X-ray diffraction and FIR showed that increasing temperatures produced reduction of the hydrated starch structures, increased crystallinity and molecular order of starch chains, and had important effects on the gluten secondary structure. High treatment temperatures produced significant reductions in rapidly digestible starch (RDS) (5321% at 20 degrees C, 22.24% at 200 degrees C), and the slowly digestible starch fraction tended to increase (26.12% at 20 degrees C, 31.48% at 200 degrees C). On the other hand, bread hardness showed a significant increase from 1125 N at 20 degrees C to 49.53 N at 200 degrees C, the latter value being similar to that reported for bread crusts. Principal component analysis results showed that the flour and bread characteristics were drastically changed by the DHT, with 100 degrees C representing a critical temperature. Below 100 degrees C, breads showed textural characteristics dose to that of the control bread, with reduced RDS fractions, while at temperatures above 100 degrees C, hardness was boosted. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study found that the dry heat treatment temperature has significant effects on the structure of wheat flour, bread texture, and starch digestibility. Higher temperatures decrease hydrated starch structures, increase crystallinity, and impact gluten secondary structure. High treatment temperatures result in reduced rapidly digestible starch and increased slowly digestible starch fractions.