Physical, Chemical and Biological Properties of Native and Modified Starch in Corn and Wheat

This study was conducted in the food science department, Faculty of Agriculture, Tikrit University in which the starch was extracted in lab from the yellow corn and wheat flour. The composition of the chemical components, moisture, protein, lipid, carbohydrate, and ash content were compared for those starch. The extracted starch  were modified with a view to produce resistant starch RS using three methods which were : physical- based modification including hot plate, water bath, and autoclave, chemical-based modification including oxidation, acetylation, acid, and alcohol, and finally enzymatic-based modification using α-amylase. The physical, chemical, and microscopic characteristics were studied for both the natural and modified starch from corn and wheat in addition to the percentage of starch granules. The modification by acid showed a highest value of small starch granules in corn and wheat which were (30.6 and 19.76 %) respectively, while the modification by oxidation presented a maximum portion of large granules from corn about (88.18%) and for wheat, the modification by enzyme showed a high percentage close to (91.09 %)  of large granules. Acetylation-based modification method revealed a high value for linking capability with water molecule and viscosity for corn and wheat. Moreover, the solubility and swelling values were studied for natural and modified starch granules of corn and wheat in which the modification by acid and enzyme displayed a highest solubility at 90°C while modification by oxidation revealed a maximum value of swelling for both corn and wheat. Chemical characteristics of natural and modified starch from corn and wheat were also studied by measuring amylose and amylopectin amount. Autoclave-based modification gave a maximum value of amylose for corn and wheat which were (35.52 and 32.94 %) respectively while the modification by oxidation and a cetylation showed a highest value of amylopectin among others. X-Ray diffraction (XRD) tests were implemented and displayed obvious differences in peaks and intensity of beam diffraction for natural and modified of corn and wheat.