Impact of conventional and emerging protein denaturation methods on the properties of electrospun fibers

Denaturation methods used before electrospinning can generally be classified into two groups: traditional methods such as pH adjustment, temperature treatments, and organic solvents; and emerging technologies, including microwave, high hydrostatic pressure (HHP), ultrasound, and ozone. Numerous studies have explored protein denaturation using traditional methods and their effects on protein properties. However, this study specifically highlights the role of these denaturation methods in shaping the properties of electrospinning solution from proteins (with a focus on soy protein isolate (SPI)) and the resulting electrospun fibers, delving deeply into the underlying mechanisms. This review provides an in-depth discussion of both traditional and novel protein denaturation methods before electrospinning, despite the limited number of studies on novel approaches. For most food proteins, acidic solutions generally exhibit lower surface tension and conductivity, but higher viscosity compared to alkaline solutions. pH exhibited a greater influence than the temperature on the solution viscosity, which in turn affected the resulting fiber morphology. Microwave treatment is preferred over conventional heat treatment for preparing electrospun nanofibers, as it offers higher energy and time efficiency while having a greater impact on fiber characteristics. Ozone pretreatment led to higher electrical conductivity by increasing protein solubility at acidic pH, producing smaller aggregates, and improving the morphology of the resultant electrospun fibers compared to ultrasound pretreatment. HHP pretreatment enhanced the characteristics of both fiber-forming solutions and the nanofibers of SPI-Polyvinyl alcohol (PVA) mixture by increasing viscosity, reducing surface tension, and promoting a more tangled structure in the SPI-PVA solution.