Effects of sourdough on improving the textural characteristics of microwave-steamed cake: A perspective from dielectric properties and water distribution.

A sourdough combined with microwave heating method was adopted to make steamed cake (SSC), the dough yield, fermentation time and additive amount of sourdough were optimized by Response Surface Methodology (RSM) to obtain microwave-steamed cake (MSSC) with high-quality attributes and then the potential mechanism of sourdough on the improvement of the MSSC texture was investigated. The addition of sourdough with the optimized parameters could greatly improve the specific volume, porosity, hardness, and chewiness of MSSC, which was mainly related to changes in dielectric properties and water distribution. The results of dielectric properties confirmed that sourdough increased the dielectric properties of the system during microwave heating, affecting the microwave heating characteristics. And the changes of water states and distribution by T2 relaxation analysis showed that sourdough restricted water mobility during heating and facilitated the retention of water trapped in MSSC. Additionally, the scanning electron microscopy (SEM) images indicated that sourdough weakened the gluten network structure, and triggered a looser and smoother microstructure. PRACTICAL APPLICATION: Steamed cake (SSC) is one of the most popular fermented foods in China, while its commercial development is greatly limited by the drawbacks of traditional steam heating. In recent years, the applications of microwave heating and sourdough in cereal-based foods processing have gained more and more interest. However, there is little information about the application of sourdough combined with microwave heating in SSC production. This study revealed that sourdough addition increased the specific volume, porosity, texture, and consumer preference of MSSC, providing a natural, high-efficiency, and easy-to-operate means for the fabrication of high-quality fermented foods.