BARU OIL/WATER INTERFACIAL PROPERTIES: INFLUENCE OF IONIC FORCE AND PH

The oil extracted from baru seeds is rich in bioactive compounds, and can be an interesting ingredient for industries. This study aims to evaluate the interfacial properties, which are directly related to the kinetic stability of the emulsions, of the baru oil/aqueous solution, as a function of ionic strength (0, 100 and 200 mM NaCl) and pH (6, 7 and 8), at 25 °C. Tween 80 was used as emulsifier. Interfacial measurements were performed using the pendant drop tensiometer PAT-1. After reaching the equilibrium time, the viscous and elastic modules, and the phase angle (ɸ) were obtained. The presence of oil's surface-active molecules (such as free fatty acids) was observed by the decay profile of the interfacial tension, in the absence of the tween 80 and NaCl. The interfacial activity increased with the addition of NaCl and increasing pH. The equilibrium interfacial tension varied from 1.21 to 3.4 mN.m-1. NaCl may have caused the partial loss of hydration of the hydrophilic group of tween 80, which alters the interfacial film.1 In addition, the polar carboxylic acids present in baru oil may have migrated to the interface. The interfacial layer presented a low dilatational viscoelasticity and a predominance of an elastic behavior (ɸ < 12°). Therefore, the use of baru oil in systems formulated with tween 80 and NaCl is associated with good rheological properties of interface with potential application in the food, cosmetic and pharmaceutical industries.