Effect of a novel drying method based on supercritical carbon dioxide on the physicochemical properties of sorghum proteins

Abstract: Nafisa Sadaf¹, Arda Tuhanioglu¹, Navam Hettiarachchy¹, and Ali Ubeyitogullari^1,2*
1Department of Food Science, University of Arkansas, Fayetteville, AR 72704, USA
 ²Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville,
 AR 72701, USA

Food manufacturers face several problems with processing plant-based proteins due to their limited functionality. The demand for novel and sustainable approaches for generating plant proteins is on the rise. Sorghum, as a potential crop that can withstand climate change due to its drought resistance, is under-utilized. Therefore, the research aimed to use supercritical carbon dioxide (SC-CO_²) drying as a novel and sustainable approach to generate sorghum protein concentrates/isolates with enhanced functional properties. Sorghum protein extracts obtained from white whole-grain sorghum flour were dried in two ways, namely, freeze-drying and SC-CO₂ drying. This is one of the first studies using SC-CO₂ to dry sorghum proteins. The collected proteins were characterized for their protein surface hydrophobicity, viscosity, chemical interactions, emulsifying activity index (EAI), protein solubility, microstructure, and x-ray diffraction (XRD) patterns. The surface hydrophobicities of the freeze-dried and SC-CO₂-dried proteins were similar. The emulsifying activity of freeze-dried protein powders (40.6) was better than that of SC-CO₂-dried protein powder (29.8). However, the solubility of SC-CO₂-dried proteins was higher than that of freeze-dried proteins in most of the pHs investigated. The SC-CO₂-dried proteins had significantly higher porosity compared to the freeze-dried ones. The bulk and tapped densities of the SC-CO₂-dried proteins (0.29 and 0.30 g/cm³, respectively) were significantly lower than that of freeze-dried ones (0.40 and 0.50 g/cm³, respectively) . The XRD patterns indicated that the SC-CO₂-dried proteins had lower crystallinity than the freeze-dried proteins. Overall, the proposed SC-CO₂ drying method has the potential to generate porous protein powders with improved solubility that can be used in developing functional foods.

Protein and co-products devision