Modifications of starch and its characterizations

Starch is a glucose homopolysaccharide that plays a significant role in many human activities, including nutrition, medicine, and manufacturing. It can be separated from potatoes, maize, wheat, and rice and may be found in the grains, fruits, roots, and tubers of plants. Linear amylose is made of α-d-glucopyranose units joined together by α(1→4)-glycosidic bonds while branching amylopectin is made of α-d-glucopyranose units joined by α(1→6)-glycosidic bonds; both make up starch. When sterilized, microwaved, or stored in a refrigerator, starch must withstand a variety of process conditions. Like resistant starch or branched amylopectin, starch should also have high bioavailability. Modified starches have been specifically developed to overcome the disadvantages of native starch when stored at low temperatures. The complex structure and low water solubility of native starch limited its application in the medical and industrial sectors. Thermal, freezing and thawing, radio-thermal, high-pressure, annealing, pulsed electric field treatment, and ultrasonic as well as chemical modifications such as etherification, oxidation, cationization, esterification, graft polymerization, and cross-linking on the α-d-glucopyranosyl units have been found to change the polarity, linearity, and surface properties of the molecular chains. The thermal and freeze-thaw stability, solubility, viscosity, swelling power, water binding capacity, enzymatic digestibility, and gelling ability of starch have all been improved as a consequence of the structural modifications. The reactivity of starch toward water, oil, acids, enzymes, and other chemical species is changed by exposing its reactive functional groups followed by physical or chemical treatment. All these modifications resulted in some groundbreaking improvements in starch reactivity, functionality, and applications in a variety of areas. This chapter addresses current advances in starch modifications and their different characterizations from this viewpoint.