Effect of pulsed electric field on structural properties and digestibility of starches with different crystalline type in solid state

Effect of pulsed electric field (PEF) on the structural properties of representative starches with different crystalline type, wheat starch for type A, potato starch for type B, and pea starch for type C, were investigated with polarized light microscopy (PLM), X-ray diffractometry (XRD), attenuated total internal reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, solid-state nuclear magnetic resonance (SSNMR) spectroscopy, small-angle X-ray scattering (SAXS), and gel permeation chromatography (GPC) to understand whether PEF could be applied directly in starchy foods. The results showed that PEF could change the structure of all three types of starch, especially potato starch; the birefringence, represented by Maltese cross in polarized microscopic observation changed slightly; XRD and SSNMR spectra demonstrated PEF did not change the crystalline type of starch granules. However, relative crystallinity variations happened at some points of electric field intensity (EFI). Increasing with the EFI, a bigger variation of R-1045/1022 happened in potato starch than in wheat starch and pea starch, as illustrated by ATR-FTIR. Significant influences of PEF on the scatter structure and fractal dimension of self-similar structures were observed for wheat starch and potato starch, but not for pea starch. The GPC suggested that molecular weight distribution changed for all the three starches. And in vitro tests showed that PEF changed significantly (P < 0.05) the digestibility of starches, especially wheat starch and potato starch.