Effect of resistant starch on the physical properties and structure of wheat gel at different heating temperatures

The physical properties of resistant starch (RS) are similar to those of dietary fiber; thus, RS is often added to food products to provide the same health benefits as dietary fiber. In this study, four types of RS were mixed with wheat flour, and gels were prepared. RS-2, high amylose corn starch (HACS), was used alongside three types of RS-4: phosphate cross-linked tapioca starch (XLTS) and low- and high-hydroxypropylated phosphate tapioca starch (LHTS and HHTS, respectively). The flour suspension (16.7 w/w %) consisted of a mixture of medium wheat flour (1:1 mixture of low- and high-gluten wheat flour) and RS, combined in a 95:5 ratio. The suspension was heated at either 90 or 120 °C. The control sample consisted of wheat flour only. Compressive analysis, texture analysis, microscopic observations, RS measurements, and thermal properties analysis were performed. The gel made with HACS was soft after heating at 90 °C, and this gel showed the highest RS content. Additionally, the control and HACS gels had increased RS content when heated at 120 °C. In contrast, while the physical properties of the RS-4 mixed gels (XLTS, LHTS, and HHTS) changed upon heating, the RS content did not increase in the gels heated at 120 °C. Therefore, the RS-4 mixed gels may inhibit wheat starch aging during retort cooking. These results indicate that mixing HACS into flour is the most effective way to increase the RS content in a water-dispersed flour system with high-moisture content, with higher heating temperatures facilitating this process.