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STRUCTURAL AND FUNCTIONAL PROPERTIES OF ENZYMATICALLY MODIFIED SLOW DIGESTING α-GLUCANSSarah G Corwin (9193664) 12 October 2021 (has links)
<p>Moderating glycemic response to foods is important for the
potential to control or prevent hyperglycemia-related diseases, such as
diabetes and cardiovascular disease. The importance of slowly digestible
carbohydrates (SDC) lies in their health effects: moderated blood glucose
response, and a potential for increased satiety and reduced intake, and weight
management. The research presented is on structural properties of novel, mostly
soluble, a-glucans
(glucose-containing oligomers and polymers with different linkage types and
combinations) that are required for slow yet full digestion, and how they
behave in food systems. Up to this point, little has been known regarding what
structural properties of glucose-containing carbohydrates result in slow
digestion, although starch structure has been well investigated and it is known
that raw starch has a slowly digestible property. In addition to the
structure-function aspect of the thesis work, this research contributes
information about how a-glucan SDCs can be incorporated into food products that
undergo heat treatment in the presence of moisture. The a-glucans maintain their
SDC property while raw starch is gelatinized and becomes rapidly digestible.
The rate of hydrolysis of a large number of novel a-glucans was studied using
a simulated upper gastrointestinal in vitro digestion utilizing porcine pancreatic
α-amylase and α-glucosidases from the rat intestine, and a subset was then
evaluated in a crossover design clinical trial with blood glucose monitoring.
Linkage and molecular weight analysis using gas chromatography of partially
methylated alditol acetates and multi-angle light scattering and refractive
index (MALS-RI) detection at time points during in vitro digestion were used to
elucidate the relative rate of digestion of different linkage types in new and
known a-glucan
carbohydrates. Rheological, turbidity, and SLS and DLS analyses were used to
examine ingredient interaction between novel, enzymatically-modified α-glucans
with slow digesting properties found most promising for inclusion in food
products. A model nutritional beverage system was utilized containing proteins
and salts. It was found that solvent and ion concentration of solutions were
important for dictating aggregation formation with highly branched alternans
and oligosaccharides in solution alone, or in the presence of soluble protein
aggregates. Further, salts in solution proved to influence rheological and
turbidity measures of all four α-glucans examined in the model system,
indicating they may affect aggregation and structural conformation of such
large carbohydrates. However, only tapioca maltodextrins showed in vitro rate
of digestion affected by aggregation.</p><p></p>
<p>These results show the chemical and molecular properties of
modified carbohydrates that contribute to slow digestion rate, which is
informative to develop improved or new SDCs, as well as how these novel SDCs interact
with other ingredients within a model beverage system, informing applications
for the food industry.</p>
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