Date of Award


Degree Type


Degree Name

Master of Science (MS)


Food Science

Committee Chair

Lisa Mauer

Committee Member 2

Owen Jones

Committee Member 3

Osvaldo Campanella

Committee Member 4

Corey Scott


The development of crystallinity caused by amylopectin retrogradation has been correlated to staling in baked goods. Different amylopectin crystal polymorphs have been found in starches from different botanical sources and in amylopectin crystallized in different conditions. The amount of water in each polymorph has been documented. However, the molecular mechanism involved in bread staling and the role and distribution of water during starch retrogradation are still debated. The objective of this study was to determine whether water is incorporated into or expelled from amylopectin as crystal structures form during retrogradation using moisture sorption techniques and model starch, starch:gluten, and wheat flour systems. The types of starch used included A-type amylopectin (corn), wheat, and corn starches and B-type potato and 70% amylose corn starches. Suspensions (5% w/w solids) of starch, 7:1 starch:gluten, and wheat flour were heated to fully gelatinize the starch (excluding 70% amylose corn which was only partially gelatinized), frozen, and freeze-dried to make amorphous matrices. Moisture sorption profiles of the dried samples were collected from 5-95% relative humidity (RH) at 25°C using a SPSx-1μ Dynamic Vapor Sorption Analyzer. To capture the retrogradation event, samples were also monitored at 95%, 92.5%, and 90% RH. Powder X-Ray diffraction (PXRD) was then used to determine the crystal type formed after retrogradation. In all model systems, water was expelled from the amylopectin crystals formed during retrogradation in the moisture sorption analyzer. Overall, retrogradation increased as %RH increased. Additionally, the presence of gluten increased the amount of water present in the samples after retrogradation compared to the starch only models. At 95%RH, the PXRD data indicated that A-type starch retrograded into the A-type pattern and B-type starch retrograded into the B-type pattern. These results offer further knowledge into the role of water in amylopectin retrogradation and the relationship between starch type, the presence/absence of gluten, environmental RH (aw), moisture sorption prior to retrogradation, and water redistribution during retrogradation.