Influence of gelatin–sodium stearoyl lactylate interaction on the rheological properties of gelatin gels

Addition of surfactants to the polymer solutions induces changes in the bulk of solutions as well as at the interface due to their interactions, thus changing the properties of the systems. Therefore, investigations of these interactions have a great practical and theoretical interest. In the present study, interaction between gelatin and anionic surfactant sodium stearoyl lactylate (SSL) was investigated by different methods. Conductometry and tensiometry were applied to define a region of gelatin–SSL interaction. On the basis of these investigations: cac, defined as concentration at which SSL molecules start to form aggregates with gelatin molecules, and psp at which interaction finishes, were determined. Solutions of gelatin–SSL mixtures at characteristic mass ratios of components were prepared for detailed rheological investigations. Considering that gel formation and network stabilization is time dependent, rheological measurements were performed on gels after 2 and 6 days of storage. Rheological and viscoelastic investigations showed that the presence of SSL molecules influence gelatin ability for gel formation. Increase in SSL concentration decreases thixotropy of gelatin gels which show more viscose, fluid-like properties.