Preparation, structure and stability of sodium caseinate and gelatin micro-particles

Protein particles are promising candidates for texturing food products and can be produced in several ways. Here, we produced protein particles using a two-step emulsification method. This method is suitable to change the size of the particles and to control the protein concentration inside the particles. In this study, we prepared protein particles from two different protein sources, sodium caseinate (NaCas) and gelatin, that are gelled by acidification and cooling, respectively. The size and the internal protein concentration of the particles, their stability against heating and pH changes were studied. Although similar emulsification conditions were used to prepare the particles, NaCas particles were found to be 10 times smaller (average diameter 400 nm) than the gelatin particles (average diameter 4 µm). The internal protein concentration of the NaCas particles (16.8% w/w) is approximately twice as high compared to that of gelatin particles (7.6% w/w) (using an initial protein concentration of the solution of 10% (w/w)). The NaCas particle dispersions were found to be stable between pH 3 and pH 4. The particles disintegrated at pH values further away from the iso-electric point. Upon heating the dispersions at 90 °C, the NaCas particles were shown to be heat stable. Dispersions of gelatin particles were stable against aggregation at all pH values studied, except at pH 6, while the particles melted above 40 °C. Swelling of both particles was observed for both acidic and alkaline pH values. We conclude that emulsification method is robust for different protein sources used.