Lignin derivatives stabilizing oil-in-water emulsions: Technological aspects, interfacial rheology and cytotoxicity

The emulsifier ability to stabilize oil-in-water emulsions of two industrial lignins (calcium lignosulfonate and kraft lignin) were evaluated and compared with whey protein isolate that is a widely used emulsifier, as well as their cytotoxic effect in Caco-2 and HT-29 cell lines. The surface activity of calcium lignosulfonate (LG) and kraft lignin (LA) was evidenced by the reduction of interfacial tension between oil-water phases, and interfacial activity was lower and presented a faster decrease than those obtained for whey protein. This behavior was associated to the great driving force promoted by the high number of hydrophobic groups on the lignins. The emulsions with lignins presented smaller diameter (0.717 mu m) and higher zeta potential than emulsion produced with WPI (1.065 mu m). In addition, WPI emulsions were the most unstable after 28 days of storage. Among lignins, emulsions with kraft lignin were the most stable due to differences in the functional groups on these lignins. The cytotoxicity of lignins towards HT-29 and Caco-2 cells showed a dose-response relationship, determining non-cytotoxic concentrations for emulsifiers that can produce stable emulsions. In order to encourage the industries to use these lignins in polymeric form, these results present the safety level for both lignins capable of producing a stable emulsion, in addition to presenting characteristics of these two biopolymers that will influence the different applications.