Organisation of the external region of the starch granule as determined by infrared spectroscopy

Attenuated total reflectance–Fourier transform infrared (ATR–FTIR) was used to study the external regions of starch granules. Native starches (wheat, potato, maize, waxy maize and amylomaize) were analysed and compared to gelatinised and acid-hydrolysed starches. The IR spectra of potato and amylomaize starches were closer to that of highly ordered acid-hydrolysed starch than the other starches. FTIR was not able to differentiate between A- and B-type crystallinity so the difference observed between starches was not related to this factor. The variation between starch varieties was interpreted in terms of the level of ordered structure present on the edge of starch granules with potato and amylomaize being more ordered on their outer regions. This could explain the high resistance of both these starches to enzyme hydrolysis.