Dielectric barrier discharge and radio-frequency plasma effect on structural properties of starches with different amylose content

Abstract

Abstract The effect of the dielectric barrier discharge atmospheric (DBD) and radio-frequency (RF) cold plasma treatment on the morphology, helical order, and structural stability of starches with different amylose content (30, 50, & 70%) was investigated. The cavities formed after RF plasma treatment allowed the active species to modify the internal structure of the granule, probably reaching its center and expanding to the periphery, where the amorphous regions were damaged and gradually removed by the treatment, increasing the amylose helix order and thermal stability of starch molecule as suggested by the SEM, FTIR, DSC, and TGA analysis. In contrast, DBD treatment promoted a thicker coating deposition and HMDSO functional groups inclusion, which increased both the granular interaction and the decomposition temperature. Overall, active species of HMDSO plasma generated in RF and DBD reactors modified mainly the amylose chains in a distinctive way, favoring the ordering or stability of starch molecules, respectively. These findings could be useful when looking for potential applications in the food industry or in other fields like semiconductors. Industrial relevance Atmospheric pressure dielectric barrier discharge (DBD) and radio-frequency (RF) plasma are sustainable and quick methods to modify the structural properties of corn starch. After short-time treatments (10\u202fmin) both reactors change the granule surface (HMDSO coating and holes), which resulted in structural changes at different extent, such as increase of helical order and high thermal stability. These results showed that the DBD and RF treatments are suitable methods to obtain starches with high resistance to gelatinization (≈91\u202f°C), especially those with high amylose content; however, due to their distinctive properties, they could have different end uses. DBD treated starch with HMDSO chemical group incorporation could be used in the paper, packaging, and electronic industry. Although HMDSO plasma is not yet approved for food industry, the results of FTIR confirmed that RF plasma treatment does not incorporate new elements in the starch molecules but only promoted interactions between them. Therefore, HDMSO plasma treatment could be considered as a safe and chemical-residue free technique useful to modify starches, which can be explored in food matrices development. Furthermore, they could be employed in an industrial food process that involves the use of high temperature.