An innovative approach for cold plasma modification on starch via gas-liquid discharge system: Structural changes and...

Cold plasma via gas-liquid discharge systems (GLP) and gas-solid discharge systems (GSP) were conducted on mung bean starch under different input power (50, 60, 70 W) and exposure duration (1, 3, 5 min), and the structural changes and physicochemical properties of starch were investigated, in comparison with the gas-solid discharge systems (GSP). Results indicated that amylose content gradually decreased for GSP-treated samples when the treatment power and duration increased, while that of GLP-treated samples decreased sharply. The GLP-treated starch suspensions exhibited lower pH and higher conductivity compared with GSP, indicating greater production of acidic compounds from liquid-mediated plasma. X-ray diffraction and Fourier-transform infrared spectroscopy revealed that double-helix structures and crystallinity were disrupted, accompanied by a greater reduction in gelatinization enthalpy for GLP-treated samples. In contrast to GSP, larger extent of increase in solubility, as well as considerable reduction in swelling power was observed for GLP-treated samples. The overall pasting viscosity of GSP-treated starch gradually declined with the increment of plasma intensity, while those of GLP exhibited almost no typical pasting profile with quite lower viscosity. GLP treatment could mainly involve the generation of plasma species within the gaseous phase and post-discharge reactions by liquid-mediated plasma within the solutions. This study would provide theoretical foundation for developing an innovative starch modification approach based on gas-liquid discharge system.