Characterization and Emulsifying Ability of Cassava Peels Solubilized Using Hydrothermal Treatments

Cassava peels are rich in polysaccharides but highly unexplored and underutilized, as they could be used to meet the increasing demand for clean-label foods. This study investigated the effect of temperature on the solubilization of cassava peel during hydrothermal treatment to determine the emulsifying ability of solubilized cassava peel (SCP). Subcritical water conditions were employed via hydrothermal (120-200 °C; 2 MPa) or autoclave (127 °C; 0.2 MPa) treatments to solubilize cassava peels. The composition of the SCPs was determined, and their emulsifying ability was assessed using interfacial tension and zeta potential measurements. Under the best treatment conditions (140 °C at 2 MPa [hydrothermal]; 127 °C at 0.2 MPa [autoclave]), SCPs reduced interfacial tension against soybean oil to 12.9 mN/m and 13.4 mN/m, respectively. A strengthened co-emulsifier system was developed by incorporating SCPs with <i>Quillaja</i> saponins (QS) or Tween 20 to enhance the performance. Dynamic interfacial tension and zeta potential measurements revealed synergistic interactions, showing a remarkable reduction in interfacial tension from 12.94 to 5.33 mN/m. This suggests that the SCP has a surfactant-like structure owing to its amphiphilic structure and hydrophobic chains (nonpolar region) attached to the -OH functional group (polar region). Combining a second surface-active compound or co-emulsifier results in an additive effect, reducing the interfacial tension. These findings provide novel insights into carbohydrate-saponin binding and elucidate the impact of peel composition, concentration, and hydrothermal treatment conditions on co-emulsifier system performance, which will assist in the development of emulsifiers, contributing to the advancement of clean-label food technologies, effectively replacing synthetic emulsifiers in food formulations, and offering both sustainability and functionality. A systematic investigation of processing conditions and co-emulsifier interactions provides a practical framework for developing high-performance natural emulsifiers from agricultural waste.