The compositional and structural complexity of sorghum protein ingredients drives their interfacial behavior

Plant-based proteins have emerged as sustainable emulsifiers as they may produce stable emulsions by forming a viscoelastic layer at the oil-water interface; however, their interfacial behavior remains insufficiently explored. The present work investigates the rheological behavior of interfacial films formed from aqueous suspensions of different sorghum protein ingredients. The effects of protein concentration and high-pressure homogenization (HPH) on the interfacial properties were also assessed. Interfacial layers were formed by adsorption of the protein ingredients' components at the oil-water interface, and subsequently subjected to oscillatory dilatational deformation experiments. The films showed viscoelastic to strongly elastic behavior, with the ingredient concentration and HPH pre-treatment affecting the elastic modulus, which was further underpinned by representing the data as Lissajous plots. Importantly, the presence of endogenous lipids in sorghum protein ingredients largely influenced the interfacial film composition and structure, notably decreasing their mechanical resistance and elasticity.