Deuterium nuclear magnetic resonance studies of potato starch hydration.
Deuterium Nuclear Magnetic Resonance (NMR) measurements at 4.7 Tesla were used to study the hydration properties of potato starch suspensions as a function of the starch-to-water ratio. The deuterium NMR spectrum of potato starch suspensions consisted of a relatively tall, single Lorentzian (D2O) peak and a resolved doublet ('powder' pattern) of about 1 kHz quadrupole splitting and low amplitude. The deuterium NMR transverse relaxation rate (R*2) was measured for the single Lorentzian, deuterium oxide peak; this rate increased with increasing starch-to-water ratio. Deviations of such R*2 dependences from linearity were observed only at high ratios of starch-to-water, above approximately 40% solids. In addition to the 'free' or bulk population (which has a very fast rotational correlation time of 5 ps), a second population of water weakly sorbed on the starch granule surface was monitored and found to be in fast exchange with the bulk water; this second water population has a rotational correlation time of 17 ps at 298 K, only about three times slower than that of bulk water. Additionally, a third population of slowly exchangeable water is present, which is "anisotropically bound" and has a highly restricted motion within the potato starch granule structure; well-defined quadrupole splittings are observed from this latter population of water in potato starch. Potato starch exhibits unique hydration properties that have not been found in cereal starches.
Yakubu
P I
PI
University of Illinois, College of Agriculture, Department of Food Science, Urbana 61801.
Baianu
I C
IC
Orr
P H
PH
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003903:Deuterium; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011198:Solanum tuberosum; D013213:Starch / Q000737:chemistry*
D013213:Starch; D003903:Deuterium