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|Title:||Solute-Polymer States of Water and the Physico-Chemical Properties of Food Model Systems (Crystallinity, Sorption, Hysteresis, Starch)|
|Department / Program:||Food Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Food Science and Technology|
|Abstract:||The objective was first to study physico-chemical properties of solute-polymer mixtures as related to water binding, solute content and water activity (a(,w)). It was hypothesized that these properties were due to the presence of solute (SOL) and polymer (POL) water. The second objective was to develop a non-invasive analytical method for SOL and POL.
Interactions in freeze dried systems were found in sucrose-starch, NaCl-starch and sucrose-protein mixtures over the intermediate moisture range of a(,w). Interactions for sucrose-starch and NaCl-starch were determined by the reduction in water sorption from the expected values. Interacted solutes rose sharply with increasing solute-starch ratio to a maximum and decreased to zero with further increase. Interaction was highest at saturation a(,w) and higher in gelatinized than raw starch. Less interaction was found on desorption. In contrary, sucrose protein interactions resulted in higher water sorption than expected, i.e., they increased the water binding by the proteins.
The crystallinity of waxy maize starch and sucrose by X-ray diffraction was found accurate. (1) Starch crystallinity increased with increasing a(,w) and moisture content. In gelatinized starch, a critical moisture content was required for recrystallization. Crystallinity hysteresis loop was over the same a(,w) range as water sorption hysteresis. On desorption, sucrose present caused a sharp decrease in starch crystallinity at 0-10% sucrose while, at higher sucrose content, the crystallinity increased. (2) Sucrose crystallinity in a mixture was about 80% at 0.33 and 0.75 a(,w) and 50% at 0.84 a(,w) on absorption. However, on desorption, all samples showed zero crystallinity. Moisture hysteresis for sucrose and waxy maize starch was insignificant. Sucrose-starch mixtures showed marked hysteresis, only at a(,w) below 0.86, the saturation a(,w) for sucrose. Hysteresis showed a close linear correlation with the amount of amorphous sucrose present.
('1)H pulsed NMR was used to characterize the quantify SOL and POL in mixtures of sucrose and starch. T(,1) relaxation time increased with increasing sucrose content and a(,w). Model equations were developed for calculating SOL and POL from T(,1) and a(,w). These values showed high correlations (R('2) > 0.97) with SOL and POL from sorption data, validating the method.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.
|Date Available in IDEALS:||2014-12-15|
This item appears in the following Collection(s)
Dissertations and Theses - Food Science and Human Nutrition
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois