Abstract: In order to study the effect of co-fermentation of dough by Pediococcus acidilactici and Saccharomyces cerevisiae on the structural and physicochemical properties of wheat starch, starch was extracted from sourdough co-fermented with the two strains for 0, 6, 24 and 42 h and evaluated for physicochemical and structural properties such as solubility, swelling potential, and pasting characteristics. The results showed that the co-fermentation increased the starch content, solubility, swelling potential, and transparency. Scanning electron microscopy (SEM) and particle size analysis showed that the co-fermentation resulted in more serious surface erosion of starch than did pure culture fermentation by S. cerevisiae, and decreased the particle size by 1.19 μm. Infrared spectroscopy and crystal structure analysis showed that fermentation neither resulted in the production of new functional groups nor changed the crystal structure of wheat starch; however, the co-fermentation increased the crystallinity of starch by 2.15% and the thermal stability by 3.70 J/g compared with pure S. cerevisiae fermentation. The pasting characteristics indicated that the co-fermentation hindered the short-term aging of starch and promote the development of the gel network structure of starch granules. In summary, the co-fermentation was more likely to change the structure and physicochemical properties of starch than S. cerevisiae fermentation of. Therefore, the co-fermentation could effectively improve the properties of wheat starch, thus improving the food quality.

Key words: fermentation, wheat starch, structural properties, physicochemical properties