How to use Arabic gum to stabilize emulsions? A story of proteins and polysaccharides

2^nd International Conference on Food Chemistry & Nutrition

July 24-26, 2017 Vancouver, Canada

M Atgie, O Masbernat and K Roger

CNRS, France

Posters & Accepted Abstracts: J Exp Food Chem

Abstract :

Arabic gum is a natural product issued from Acacia trees, which has been used for centuries as a stabilizer in various formulations. The origin of this hydrocolloidâ�?�?s remarkable properties remains challenging to fully elucidate, since the gum is in fact composed of several species. Arabic gum contains various proteins and polysaccharides, some of them covalently linked, which all possess different interfacial properties. In the literature, the gum was mainly divided into three main fractions: polysaccharides, glycoproteins and covalent protein/polysaccharides conjugates. These complexes are described as the good stabilizing species of the blend when formulating emulsions. However, we show that, in fact, all the species contain a protein fraction. In addition, no limited coalescence regime was observed when the â�?�?good stabilizing specieâ�? was in insufficient amounts to cover the interfaces, despite its large adsorption energy. We instead observe a slow and continuous coalescence of the emulsions, over weeks, which contrasts to the expected behaviour from pickering emulsions. We have developed methods, to separate the different species of the gum according to their size and amphiphilic property. In order to elucidate the contributions of each species to emulsion stabilization, we have coupled two types of separation methods. Emulsion-mediated separation, coupled with liquid chromatographic analysis, shows which species adsorb at the oil/water interface as a function of gum concentration, pH and salinity. We identify that an acidic pH is crucial for emulsification, which is always empirically in the case of current gum applications, but hadnâ�?�?t been rationalized before. This was confirmed with interfacial tension measurements and elucidated through SAXS measurements. We also obtained the quantitative variation of the interfaceâ�?�?s composition with the gum concentration. Most species of the gum are shown to adsorb at the interfaces, but their stabilizing properties largely vary due to differences in adsorption energies and/or steric repulsion barriers. Arabic gum must thus be viewed as a continuum of amphiphilic species with different properties (figure), which should help rationalize formulations using this original gum. Our work also opens new perspectives in the use and analysis of complex mixtures.

Biography :

Email: marina.atgie@ensiacet.fr