M Kamal Hossain, Alexander Krah, Oliver Hensel and Mamadou Diakite
Microparticulation is influenced by many factors of the hot extrusion process, including process and system parameters as well as product properties. The key aim of this study was to investigate the influence of protein concentrations (Cprotein) and process parameters on microparticulation of whey protein using the hot extrusion process. During the extrusion process, demineralized water was used to reach the desired Cprotein of 20, 25, 30 and 35% respectively. The experiments were carried out using a corotating twin-screw extruder (ZSE18HP) with an L/D ratio of 40:1 at 90°C as the maximum barrel temperature. The particle size of the microparticulate whey proteins (MWPs) was measured using laser diffractometry, and particle size distributions were calculated by Fraunhofer approximation. The colors of all extruded samples were determined using the CIE L*a*b* system. Additionally, the microscopic properties of particles were determined using a digital microscope with a high-magnification lens. The statistical analysis and data fitting were done using SPSS. Protein concentrations and showed a significant (p<0.001) influence on the particle size distribution of microparticulated whey proteins. The particle sizes of MWPs declined by raising the Cprotein up by 30%. On the other hand, the increase of screw speeds caused the particle sizes to decrease. However, 35% of Cprotein and a screw speed of 200 rpm gave us the opposite results. The particles that were d50 ≤ 5 µm and d50 ≤ 3 µm in size were observed from the screw speed range of 400 rpm to 600 rpm and 800 to 1000 rpm respectively. In terms of particle size distributions, the screw speeds of the extruder were also statistically significant (p<0.001). In conclusion, the particle size distributions in the so-called microparticulation process can be controlled through the manipulation of the Cprotein as well as the screw speed of the extruder.