Plasma-Activated Water Primes Black Rice Starch for Amplified Hydrothermal Modification: Structural Insights and Enhanced Digestibility.

This study evaluated the ability of plasma-activated water (PAW) to modulate black rice starch response to autoclaving. Six formulations were prepared: native starch (Native), starch treated with PAW for 30 or 60 min (P30, P60), starch autoclaved only (AC), and starch subjected to PAW for 30 or 60 min prior to autoclaving (P30AC, P60AC). PAW pretreatment intensified autoclaving-induced depolymerization, as reflected by pronounced reductions in the hydrodynamic radius (Rh) of amylose and amylopectin chains. This molecular breakdown was accompanied by a redistribution of linear glucan chains toward shorter fractions (DP 6-12 increasing to 20.17%) and a decrease in apparent amylose content (up to 16.76%). Solubility increased nearly fivefold in P60AC (31.57%), while relative crystallinity declined from 25.18% to 19.68%, indicating partial loss of ordered lamellae. Gelatinization enthalpy (ΔH) was markedly reduced to 5.32 J g- 1, and pasting viscosities were strongly suppressed. Morphological analysis revealed progressive granule swelling, with average diameter increasing from 6.89 µm (native) to 12.50 µm (P60AC), reflecting extensive structural disorganization and granule fusion induced by the combined action of PAW and autoclaving. Regarding freeze-thaw stability, combined treatments exhibited the lowest syneresis values throughout five cycles, indicating superior gel water retention capacity. The results demonstrate that PAW acts as an effective non-thermal priming step that amplifies the structural and functional impact of autoclaving on black rice starch, offering a sustainable approach for tailoring starch properties with enhanced digestibility and improved gel stability.