Combinatorial effect of fermentation and drying on the relationship between the structure and expansion properties of tapioca starch and potato starch.

Naturally fermented and sundried tapioca starch is reportedly the traditional material for polvilho azedo and the primary ingredients of gluten-free food items in Brazil. This study aimed to investigate starch structure and expansion rate, high rate is acclaimed in baking application, changes of tapioca starch and potato starch during combinatorial fermentation and drying. The rate of expansion changed from 3.37 mL/g in native tapioca starch to 3.71 mL/g in fermented oven-dried tapioca starch and 6.97 mL/g in fermented sun-dried tapioca starch, while potato starch sample displayed lesser expansion on all treatments. Rapid viscosity analysis, size-exclusion chromatography, X-ray diffraction (XRD), and attenuated total reflectance fourier transform infrared (ATR-FTIR) and electron paramagnetic resonance spectrometry (EPR) were performed to determine the structure and investigate its relationship with the expansion rate. Fermentation attacked amorphous area and cleaved glycosidic bonds. Sunlight exposure facilitated complex interactions, and crosslinking increased the molecular weight distribution (MWD) in fermented sun-dried potato starch and led to depolymerization in tapioca starch. EPR revealed an initial free radical distribution in both starches, and our results show that intensity changes in tapioca starch are essential for a high expansion capacity.