Effect of Combined Germination-Fermentation Treatment on the Structure and Physicochemical Properties of Foxtail Millet Starch

To investigate the effects of combined germination-fermentation treatment on structural and physicochemical properties of foxtail millet starch. Starch was extracted from Changzagu 466 using an alkaline extraction method. Changzagu 466 was first germinated and then fermented by Weissella cibaria. Properties such as amylose content, molecular weight, morphology structure, granule size, short-range ordered structure, pasting properties, and thermal properties of starch from foxtail millet were analyzed. The results showed that the combined germination-fermentation treatment resulted in a significant decrease (P<0.05) in its total starch content of foxtail millet. Obvious cracks appeared on the surface of starch granules, and more granules appeared to large and deep pores on the surface, which destroyed the integrity of the granules. This significantly reduced (P<0.05) starch particle size and increased starch crystallinity and the degree of starch ordering. The combined germination-fermentation treatment resulted in foxtail millet starch with higher amylose content (24.53%), setback viscosity (2754 cP), pasting temperature (76.9 ℃), ∆H (11.3 J/g), and Tc (79.0 ℃), but lower peak viscosity (4593 cP) and breakdown viscosity (2926 cP) compared to germination alone. In conclusion, the combined germination-fermentation treatment had a significant effect on the structure, pasting characteristics, and thermodynamic properties of foxtail millet starch. Compared to the germination treatment alone, foxtail millet starch subjected to the combined germination-fermentation treatment had better anti-digestion, anti-swelling force, heat resistance and shear resistance. The results of this study would provide a theoretical basis for the development of whole foxtail milllet.