Author
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Himmelsbach, David |
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Meadows, Frederick |
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Submitted to: US Japan Nutritional Research Panel
Publication Type: Abstract Only Publication Acceptance Date: 3/20/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Proton high-resolution magic-angle spinning (**1H HR MAS) NMR spectroscopy was used to determine the alpha-(1-4)/alpha-(1-6) branching ratio in rice starch. Both isolated starches and starches in rice flour were investigated. The branching ratio was determined by division of the sum of the integrals of the linear alpha-(1-4), branched and non-reducing terminal lproton signals by the integral of the signal due to the anomeric proton of the alpha-(1-6) branch alone. The **1 HR MAS experiments were conducted using both a wide bore 300 MHz NMR system with a modified CP/MAS probe and a narrow bore 500 MHz NMR system using a **1H/**13C gradient HR MAS probe. Both MAS systems provided increased signal/noise over the comparable solution NMR method, but with reduced resolution. It is shown from this work that a 300 MHz NMR system provides sufficient signal/noise to make accurate determinations of the branching ratio in the case of in situ starches. It also avoids the loss of signal to sidebands that are generated at higher field strengths. Two-dimensional correlation spectroscopy (COSY) and heteronuclear single quantum coherence (HSQC) experiments were used to confirm assignments and are being used to investigate further interactions between proteins and lipids with starch in rice flour. The method provides an accurate alternative to the determination of apparent amylose that is subject to interference by long linear chains in amylopectin and requires correction for the presence of lipids. It has the potential of becoming the primary method for calibration of other measurement systems for this quality parameter. |
