|M.Sc Student||Zabar Shiran|
|Subject||Microstructure of Starch Derivatives|
|Department||Department of Chemical Engineering||Supervisor||Professor Havazelet Bianco-Peled|
This research is focused on starch derivatives being used as food additives because of their physiological activity which resembles that of dietary fibers.
RS III is a derivative of starch which is resistant to enzymatic digestion in the small intestine but is fermented by the microbial flora in the colon. RSIII has health benefits such as pro-biotic effects, improving lipid and cholesterol metabolism, and reducing the risk of colon cancer.
Another interesting family of starch derivatives is complexes of crystalline amylose and fatty acids. Unsaturated fatty acids have a beneficial influence on the human body but it is hard to use them as food additives in their natural form. Complexes of amylose-fatty acids might supply a protection from oxidation and thermal treatments to those sensitive components and in addition, provide controlled release in the digestion system and to achieve a maximal absorption.
We investigated starch derivatives using two main approaches: 1) RS as food additive that encourages pro-biotical activity, 2) Starch derivative as a complex with fatty acids as transportation and drug release into the large intestine.
Various polymorphs of RSIII were produced from different plants at two incubation temperatures and with a number of melting and crystallization cycles. Amylose-fatty acids complexes were formed using two methods at three crystallization temperatures.
All starch derivatives were first characterized using X-ray diffraction and small angle x-ray scattering where an appropriate model was fitted to the experimental results in order to investigate the lamellar structure.
An enzymatic hydrolysis was performed in order to understand the factors that affect the enzymatic digestion rate of RS. The thermal stability and degree of crystallization of the amylose-fatty acid complexes were characterized using Differential Scanning Calorimeter.
The results of the first part indicated that crystallization at low temperature leads to lamellar structure and at high temperature, the structure is unorganized and the system can be described as a two phase system.
Adding cycles of melting and crystallization causes the formation of more organized crystals with larger amount of lamellas in every crystal and the overall yield is increasing.
In the second part we found that the particles are arranged in layers with periodically structure. The conformational structure of the fatty acid has a major affect on the characteristic of the formed crystal. In most of the characteristic that were examined, the crystallization temperature has no influence except crystallization at high temperature.