Protein/pectin (P/P) interactions can be used as an important tool to modify the microstructure of the composite systems to produce stable systems (Dickinson, 2008), because P/P complexes can show better qualities than single components (Ye, 2008). In our study, an initial P/P solution was prepared at complexation pH (pHc) using a microfluidic device adopting the flow focusing technique (Utada, 2007); such device permits a precise flow rate control of each fluid using syringe micropumps. The complex stability was investigated measuring particle size over time and using different co-focusing fluids. While P/P complex obtained using standard production techniques (manual mixing) showed precipitation and aggregations, in the case of particles obtained using microfluidic techniques results showed a significant particle size stability after 10 h after complex production. Following these results the complex formation was investigated using a buffer acetate solution to set pH at pHc to ensure the optimal conditions for the P/P complexation and, varying the flow rate. Best results were obtained by using a P/P ratio which is slightly different from the ratio presented in Di Pierro, et al., 2013, suggesting that mixing conditions play an important role.
Another set of experiments was also run using sucrose as focusing flow to study the influence of density and others physical parameters on the extrusion stage and stability of P/P complexes. Results demonstrated that varying the flow rate of focusing flow do not significantly affect the complex size distribution.