Effect on Physical and Thermal Properties of Corn Starch Treated by Energetic N₂ Extracted From Glow Discharge Plasma

Abstract

In a typical nitrogen glow discharge plasma, a large number of energetic neutrals, N₂, are generated inside the cathode sheath. In this work, we are presenting a technique for the extraction of this energetic N₂ for the treatment of starch. The energetic neutrals N₂ were generated by the application of −500 V on a transparent cathode. On reaching the cathode, N₂^+ ions are absorbed; however, it is transparent to energetic N₂ neutrals molecules generated inside the sheath by charge exchange collisions, as the energetic N₂ neutrals are unaffected by the electric field and pass through the transparent cathode. The sample for treatment was placed below the transparent cathode and thus exposed to the energetic N₂ neutrals extracted from glow discharge plasma for a duration of 30 min. The impact of energetic N₂ neutral extracted from glow discharge plasma results in modification of physical and thermal properties of corn starch (maize starch). The physicochemical and morphological properties of treated and untreated samples were studied. The surface roughness of the plasma-treated corn starch increased significantly in comparison to the untreated sample. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) spectra confirmed that there is a considerable reduction in the semicrystalline nature and the polymer structure morphology of the corn starch. Scanning electron microscope (SEM) micrographs of samples show a substantial change in surface morphology and in size of the grains between the plasma-treated and untreated corn starch samples. The room-temperature thermal properties of the plasma-treated corn starch samples are measured using differential scanning calorimetry (DSC). The results confirm that the starch treated with energetic N₂ molecules has a lower gelatinization temperature and could be applied in food processing industries.