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The main objective of this project is to study structural and physico-chemical properties of cassava starch with more advanced and complicate techniques including heating stage microscopy, X-ray diffraction, Dynamic Mechanical Analysis (DMA) and Nuclear Magnetic Resonance (NMR). Four starch samples extracted from roots grown with different growth conditions (planted with and without water stress) and harvested at different time (6 and 12 months) were used in this study. |
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When observed under the light microscope, the capability (rate and extent) of granule-water interaction of cassava starch during heating was various depending on environmental growth condition. Cassava roots grown without water stress provided starch granules with higher water uptake capability. All starch samples however had the same polymorph which were ``A" type. Further examination of starch structure and properties by DMA and NMR will be conducted.
Starch is used as a functional ingredient during the manufacture of food and other industrial products, to control or improve properties of the finished item. To achieve the desired properties most starches are chemically modified to withstand the processing environment or to alter specific functional characteristics of the starch. However, recent consumer driven trends in production and utilization of starches point to a growing interest in new product development that does not involve chemical modification. |
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This project explores the possibility of extending the functionality of cassava starch through physical modification by ball-milling under the anhydrous condition. Native starch with the granule size in range of 9 to 30 m and the center at 15 and 21m after milling became smaller; the distribution of particle less than 6 m increased from 2.20% of native starch to 41.93% for 120-min ball-milled starch.
Crystal structure of starch granules was lost as ball milling time increased. Scanning electron microscopy revealed that ball-milling caused starch granules to be broken, resulting in a change in thermal properties of starch. Ball-milled treated starch exhibited higher water holding capacity and solubility when incubated at 35 to 95C.
This might due to an explosion of hydroxyl groups in damaged starch granules caused by ball-milling. Treated starch, however, had a significant decrease in paste viscosity and pasting temperature as determined by Rapid Visco Analyzer and Brabender Viscoamylograph. No endothermic peak of gelatinization was observed when |
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