Effect of nixtamalization on the modification of the crystalline structure of maize starch

Endosperm of nixtamalized corn was analyzed using X-ray diffraction. Relative crystallinity changed with lime concentration and steeping. Diffractograms showed peaks corresponding to V-type crystalline structures, indicating formation of complexes during cooking and steeping. Diffraction patterns of the soluble fraction showed that complexed amylose can be leached out during solubilization. While diffraction patterns of the insoluble fraction suggested that some of the formed complexes remain in this fraction. During alkali steeping, release of amylose is strongly inhibited as indicated by the pronounced decrease in the starch–I₂ absorbance of the lime treated samples compared to the lime-free treated sample. This decrease is interpreted as evidence of starch cross-linking during the nixtamalization process. Differences in starch–I₂ absorbance and in X-ray diffraction patterns of the soluble fractions suggested that lime treatment could also modified formation of amylose complexes with lipids.