Characterization of saponin foam from Saponaria officinalis for food applications

Soapwort (Saponaria officinalis) is a natural source of saponins, which are known for their surface-active properties and ability to form metastable foams. The properties of saponin extract from soapwort have not been well characterized. This study examines the chemical and physical properties of soapwort extract as well as its foaming behavior under food relevant conditions. We show that the extract produces metastable solid-like foams, with high foam capacity and stability. Further, the surfactant has a higher critical micelle concentration (CMC) than other natural sources, and shows some ionic character, although changes in pH only slightly affect its behavior. For a comprehensive understanding, the foaming properties were analyzed in the presence of other molecules commonly used in food systems. The presence of sodium chloride, sucrose, ethanol, and low pH was found not significantly to affect foam properties. Addition of heat increases the foam capacity, whereas ethanol at high concentrations is unfavorable. The extract presents a promising alternative surfactant for foams and other dispersions in diverse food systems.