Insights into the starch and proteins molecular structure changes of foxtail millet sourdough: Effect of fermentation from grains of cereal to pre-meal.

ABSTRACT

This study investigated the effects of foxtail millet sourdough fermentation time (0, 8, 16, and 24 h) on the protein structural properties, thermomechanical, fermentation, dynamic rheological, starch granules crystalline regions molecular mobility, and starch microstructural characteristics. The fermentation led to a significant increase in the concentration of free amino acids from protein hydrolysis. Fourier transform infrared spectroscopy (FTIR) revealed changes in protein secondary structure and the presence of functional groups of different bioactive compounds. The result of thermomechanical properties showed a significant increase in the stability (0.70-0.79 min) and anti-retrogradation ability (2.29-3.14 Nm) of lactic acid bacteria (LAB) sourdough compared to the control dough, showing a wider processing applicability with radar profiler index. In contrast, sourdoughs with lower tan δ values had higher elasticity and strength. Scanning electron microscopy showed that the surface of the starch appeared from smooth to uneven with patchy shapes and cavities, which declined the crystallinity from 34.00 % to 21.57 %, 23.64 %, 25.09 %, and 26.34 % respectively. Fermentation changed the To, Tp, Tc, and ΔH of the starch. The results of the study will have great potential for application in the whole grain sourdough industry.