Interactions and antioxidant stability of sesamol in dry-emulsions

Dry emulsions prepared from saccharose (SAC), Labrafil ® M 1944 CS, sesamol (SEOH), and hydroxypropylmethylcellulose (HPMC) or sodium caseinate (SC) by grinding or dissolution, and different desiccation techniques (spray (SD)- or freeze (FD)-drying, or heating at 60 °C) were investigated to determine possible interactions between mixture components. The goal of this study was to determine the best formulation which will regenerate perfectly, after water dilution of dry emulsions, the initial liquid emulsion with the same characteristics that before drying. The morphological state of SAC and dry emulsions were determined by scanning electron microscopy analysis (SEM) analysis. Glass transition temperature, and melting (endothermic), decomposition (endothermic), oxidation (exothermic) peak temperatures and enthalpies were measured by differential scanning calorimetry (DSC). The antioxidant activity of emulsions was evaluated through their ability to reduce 1,1-diphenyl-2-picrylhydrazil (DPPH) free radical. SEM analysis showed that SD-prepared, SC-containing dry emulsions formed better spherical particles with smooth surface at about 5 μm diameter as compared to emulsion containing HPMC. These former emulsions also showed more thermal stability by DSC. The combined results of the three analytical techniques emphasized the importance of the dry emulsion process regarding the efficiency and the thermal stability of antioxidant substances. A specific physical and/or chemical combination (such as hydrogen bond) sufficiently stable, at about 150 °C, could be suggested when the technique used for dry emulsion preparation was SD. After water dilution, this dry emulsion obtained from quaternary mixture: SAC, Labrafil ® , SEOH and SC, will regenerate the initial liquid emulsion with the same characteristics that before drying.