Chemical interactions and water barrier performance of films based on plasma-modified sorghum starch

The use of environmentally friendly technologies and renewable sources in bioplastic production offers an alternative to conventional chemical methods for modifying biopolymers and limits the formation of hazardous byproducts. Thus, this study examined how acrylic (AA) and hexamethyldisiloxane (HMDSO) plasma treatments altered the morphology and structure of sorghum starch, thereby influencing chemical interactions and molecular arrangement during film formation and determining water barrier performance. AA plasma species altered both the outer and inner layers of the granules, changing the intermolecular structural arrangement within starch molecules, whereas HMDSO plasma species altered only the granule periphery. As hypothesized, these changes promoted low chemical oxidation during sorghum starch film (F-SS) formation, favoring CC bonds within starch molecules in films containing AA- and HMDSO-plasma-modified starches (F-SSA and F-SSH) rather than C-OH interactions, thereby also enabling their binding within the crystalline fraction in F-SSH. Thus, polar sites on starch molecules were occupied by links and double helices, limiting interactions with water molecules in phenomena such as diffusion, swelling, absorbed water, and solubility. The work provides new insights into the use of plasma-modified sorghum starches as a prospect for developing packaging films for perishable foods susceptible to damage in high-humidity environments.