Abstract
The main objective of the present work is the investigation of a new method for starch hydrolysis. For this, we proposed the acid hydrolysis under the action of an external electric field, able to develop a faster reaction than the conventional one. Corn starch with 18% amylose was subjected to a fixed voltage, varying the external electric field application time and the number of cycles. Morphology, crystallinity, and thermal stability of the starches were investigated by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS). The results showed that the acid hydrolysis coupled with an external electric field allows a significant reduction in hydrolysis time, due to the orientation of the electrolyte ions. Cavities were observed at the surface of hydrolyzed starches after treatment. However, the principal feature is related to the increase of the granule crystallinity with increasing hydrolysis time. The results suggest that the starches treated by this new method are interesting candidates for application in the food industry if greater gelatinization resistance is required.
Highlights
Corn starch is an abundant biocompatible granular polysaccharide found in nature, extensively used in food industry,[1] adhesives,[2] pharmaceutical,[3] and waste treatment,[4] among others
An acid works on the starch granule surface prior to entering the inner region of starch,[13] which means that the desirable effect in starch granules can be adjustable by the acid characteristics and hydrolysis time, for example.[14,29,30,31]
The acid hydrolysis coupled with external electric field application allows an oriented ion migration and a consequent hydrolysis time reduction
Summary
Corn starch is an abundant biocompatible granular polysaccharide found in nature, extensively used in food industry,[1] adhesives,[2] pharmaceutical,[3] and waste treatment,[4] among others. Its semi-crystalline structure consists mainly of polymer chains of amylose and amylopectin associate by hydrogen bonds, forming a radial structural arrangement of crystalline and amorphous areas. The internal organization of starch is due to its radial growth around a hilum (center of the granule). This characteristic can be observed through the ability of birefringence of the material with the exhibition under polarized light of what is known as Maltese cross.[8] The crystalline regions of the starch granule originate mainly from the amylopectin, the linear parts of these branched chains, which are arranged in a double helical manner.
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