Impact of drying techniques on the physicochemical, structural, thermal, techno-functional, rheological properties, and in vitro digestibility of sesame protein isolate

Abstract

Sesame protein isolate (SPI) is emerging as a valuable plant-based protein with promising nutritional and functional properties. This study examined the influence of three drying techniques—hot air drying (OD), spray drying (SD), and freeze-drying (FD)—on the physicochemical, structural, thermal, techno-functional, rheological properties, and in vitro digestibility of SPI. While proximate composition remained unchanged, notable variations were observed in particle size, zeta potential, FTIR spectra, free sulfhydryl (–SH) groups, and surface hydrophobicity (H₀), reflecting conformational modifications. OD-PI exhibited the highest denaturation temperature (81.83 °C) and lowest enthalpy (28.86 J/g). SD-PI demonstrated superior functional traits, including emulsion capacity (29.91 %), stability (64.83 min), foaming capacity (127.78 %), stability (47.78 %), water-holding capacity (1.81 %), and rheology, attributed to its small particle size (4.51 μm) and high solubility (72.62 %). FD-PI showed the greatest –SH and H₀ values. Importantly, SD-PI displayed enhanced digestibility, establishing spray drying as the most effective method for producing high-quality SPI for food applications.