title: Mobility and distribution of water in cassava and potato starches by 1H and 2H NMR.
abstract: Mobility and distribution of water in cassava (rainy and drought crops) and potato starches were studied by solid state and NMR relaxometry as a function of H(2)O and D(2)O contents ranging from 0 to 44% (dry basis). Measurements of relative mobility derived from (2)H solid state NMR were based on relative area and line shape analysis. The narrow peak (mobile component) started to show at 5% and increased with increasing D(2)O content. This increase in mobile fraction was accompanied by a line narrowing. The mobile fractions of deuterons reached a >98% level above 15% D(2)O, which is well below the water holding capacity of starch ( approximately 27%) and the previously assigned "glassy-rubbery transition point" (24.3%; Jouppila, K.; Roos, Y. H. The physical state of amorphous corn starch and its impact on crystallization. Carbohydr. Polym. 1997, 32, 95-104). This reconfirms the liquidlike nature of water in the so-called glassy state of starch granules. The plasticization effect of water on starch chains was observed at 14-17% for cassava and potato starches as indicated by the T(1) minimum. This, however, did not seem to relate to the difference observed in swelling among the starches studied.
authors.affiliation: Food Science Department, University of Massachusetts, Amherst, Massachusetts 01003.
authors.forename: Pathama
authors.initials: P
authors.lastname: Chatakanonda
authors.forename: Leonard C
authors.initials: LC
authors.lastname: Dickinson
authors.forename: Pavinee
authors.initials: P
authors.lastname: Chinachoti
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D009682:Magnetic Resonance Spectroscopy; D002365:Manihot / Q000737:chemistry*; D011198:Solanum tuberosum / Q000737:chemistry*; D013213:Starch / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D013213:Starch