Abstract: Sorghum starch, as a highly promising natural resource, often faces limitations in its applications due to inherent functional deficiencies. In this study, vacuum cold plasma technique was employed to modify sorghum starch using nitrogen (N2) or argon (Ar) as the atmosphere gas at different discharge powers of 400 and 700 W. The effects of different gas types and discharge powers on the multiscale structure, physicochemical properties, and gel characteristics of the starch were systematically investigated. The results indicated that plasma treatment induced surface etching of starch granules, depolymerization of molecular chains, and partial crosslinking reactions. The amylose content exhibited a nonlinear trend of initially increasing and subsequently decreasing (the N2 group: 35.08%–36.19%; the Ar group: 33.26%–36.19%). The relative crystallinity significantly decreased from 15.65% in the control group to 11.33% (the N2 group) and 13.03% (the Ar group). In terms of functional properties, the modification treatment reduced the thermal stability but significantly improved solubility and water-holding capacity of the starch. Low-field nuclear magnetic resonance (LF-NMR) analysis revealed that plasma modification enhanced the binding energy between water molecules and the starch matrix, promoting the formation of a denser and more uniform network structure within the gel. The modification significantly reduced gel hardness, and the Ar-treated group offered unique advantages in maintaining gel elasticity. This study elucidates the modification mechanism of cold plasma treatment on sorghum starch, providing a theoretical basis for expanding its application in the field of green food processing.

Key words: sorghum starch; cold plasma; modification; structure; gel characteristics