Abstract

This reports the first detection of chemical heterogeneity in octenyl succinic anhydride modified single starch granules using a Fourier transform infrared (FT-IR) microspectroscopical technique that combines diffraction-limited infrared microspectroscopy with a step size that is less than the mask projected spot size focused on the plane of the sample. The high spatial resolution was achieved with the combination of the application of a synchrotron infrared source and the confocal image plane masking system of the double-pass single-mask Continuμm^® infrared microscope. Starch from grains such as corn and wheat exists in granules. The size of the granules depends on the plant producing the starch. Granules used in this study typically had a median size of 15 μm. In the production of modified starch, an acid anhydride typically is reacted with OH groups of the starch polymer. The resulting esterification adds the ester carbonyl (1723 cm⁻¹) organic functional group to the polymer and the hydrocarbon chain of the ester contributes to the CH₂ stretching vibration to enhance the intensity of the 2927 cm⁻¹ band. Detection of the relative modifying population on a single granule was accomplished by ratioing the baseline adjusted peak area of the carbonyl functional group to that of a carbohydrate band. By stepping a confocally defined infrared beam as small as 5 μm × 5 μm across a starch granule 1 μm at a time in both the <i>x</i> and <i>y</i> directions, the heterogeneity is detected with the highest possible spatial resolution.

Stokes vector based polarization resolved second harmonic microscopy of starch granules

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Second harmonic generation microscopy investigation of the crystalline ultrastructure of three barley starch lines affected by hydration

Richard Cisek, Danielle Tokarz, Martin Steup, Ian J. Tetlow, Michael J. Emes, Kim H. Hebelstrup, Andreas Blennow, and Virginijus Barzda
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Selective observation of starch in a water plant using optical sum-frequency microscopy

Yoshihiro Miyauchi, Haruyuki Sano, and Goro Mirzutani
J. Opt. Soc. Am. A 23(7) 1687-1690 (2006)

Parallel confocal detection of single molecules in real time

Paul M. Lundquist, Cheng F. Zhong, Peiqian Zhao, Austin B. Tomaney, Paul S. Peluso, John Dixon, Brad Bettman, Yves Lacroix, Deborah P. Kwo, Etienne McCullough, Mark Maxham, Kevin Hester, Paul McNitt, Donald M. Grey, Carlos Henriquez, Mathieu Foquet, Stephen W. Turner, and Denis Zaccarin
Opt. Lett. 33(9) 1026-1028 (2008)