Starch Gelatinization and Modification

Starch is omnipresent in plant material and is the most important polysaccharide as well as storage polymer. Starch undergoes various transformations during food processing. Heating of starch in presence of water results in gelatinization which is accompanied by granule breakdown, loss of ordered structure, and loss of optical birefringence. Low temperature favors the re-association of disrupted chains of amylose and amylopectin in a process known as retrogradation. These changes are very much affected by the nature of starch and the amylose to amylopectin ratio. Therefore, it is important to study or monitor the various changes under the influence of various treatments to expand its commercial value. Starch possesses substantial nutritional, pharmaceutical, and industrial importance owing to its distinctive physical, chemical, and functional characteristics. Starch owns varied functional properties and applications in the food industry. However, the native starches lack desired functional characteristics for anticipated applications in the food industry. To increase its commercial significance, the functional properties of starch can be upgraded under the stimulus of several physical, chemical, and enzymatic techniques. Alterations in the structure of starch molecules initiated by various treatments are characterized as modifications. The starch structure is sensitive to high temperature, very high and low pH, high pressure, osmotic pressure, electric field, plasma, sonic waves, microwaves, irradiation, ozone, mechanical stress, various chemicals, and enzymes. These alterations may employ either desirable or undesirable changes in the structure and functionality of starch. Therefore, an appropriate selection of modification techniques concerning cost economics, environmental factors, and efficiency is required to attain targeted improvements in functional characteristics. A practical alternative to chemical and heat-induced alterations is non-thermal treatments that are clean, environmental friendly, more efficient, free from toxic residues, and are sustainable. These techniques are of most interest to the food scientist in the present times. Also, the structural transformations of starch caused by various methods are important to visualize the effectiveness of the process and can be studied by a range of available methods based on different principles such as microscopic, spectroscopic, differential scanning calorimetry, rheological, X-ray diffractions and chromatographic methods, etc. With the scientific and technological interventions, newer techniques for starch modification are being introduced to achieve the targeted characteristics in a simple and more practical approach.