Plasma-activated water (PAW) and annealing for the modification of potato starch: Effects on sorption isotherms, thermodynamic and gelatinization kinetics of potato starch

Chemical modifications of starch can be laborious and often require significant amounts of chemicals and solvents. Therefore, it has become use of modifications like plasma-activated water (PAW), which is considered an environmentally friendly technology. The aim of this study was to evaluate the effect of PAW, alone or combined with annealing (ANN) on the techno-functional properties, sorption isotherms and thermodynamic characteristics of potato starch. PAW was generated by subjecting distilled water to a corona discharge with a voltage of 15 kV and a fixed frequency of 5 kHz for 1 min. ANN was obtained by incubating starch with distilled water (DW-ANN) or PAW (PAW-ANN) for 4 h at 55 °C. The moisture sorption and the thermodynamic properties of the potato starch were determined using a dynamic vapor sorption analysis method at temperatures of 25, 35 and 45 °C. The sorption kinetic was then modelled using the GAB model. Results showed that the equilibrium moisture content of PAW-ANN and DW-ANN samples was significantly lower than that of native and PAW. Variations in binding sites and agglomeration led to changes in specific surface area (SA), mono layer (Mo) and sorption enthalpy (qst), changes in entropy (△S), and Gibbs free energy (△G). Moreover, for these samples, a significant reduction (p < 0.05) in swelling power, solubility, light transmittance (T %) and syneresis (%) was observed when potato starch was treated with PAW-ANN and DW-AANN. The combined PAW-ANN proved to be a promising technique for modifying starch and altering the kinetics of water sorption-desorption, hydration and rheological properties at different temperatures without the use of enzymes, acids or crosslinking agents, demonstrating its potential to improve starch stability.