M. Azad Emin

Influence of medium-chain triglycerides on expansion and rheological properties of extruded corn starch.

Enhancement of product properties of extruded starch based products can be achieved by incorporating health promoting oil into the matrix. In order to achieve a preferably high expansion with a homogeneous pore structure, the expansion mechanisms have to be understood. In our study, we applied a customized twin-screw extruder set up to feed medium-chain triglycerides after complete gelatinization of corn starch, minimizing its effect on the starch gelatinization. Despite the fact, that the addition of up to 3.5% oil showed no influence on the extrusion parameters, we observed a three-fold increase in sectional expansion. Longitudinal expansion was less affected by the oil content. Rheological properties of the gelatinized starch were measured using an inline slit die rheometer. In addition to shear viscosity, we presented a method to determine the Bagley pressure, which reflects the elongational properties of a fluid. We were able to observe an increase in the Bagley pressure from about 25 bar up to 35-37 bar due to the addition of oil.

Characterization of Mixing in Food Extrusion and Emulsification Processes by Using CFD

In this contribution, local flow of complex food matrices in an extrusion (i.e. twin screw extruder) and high-pressure homogenization processes (i.e. in micro-structured nozzles) were simulated by ANSYS POLYFLOW® and ANSYS FLUENT® respectively. In extrusion process, the efficiency of dispersive mixing of food-grade triglycerides of Newtonian behaviour in rheologically complex plasticized starch matrices was evaluated. Simulation results were validated quantitatively by experimental data. Furthermore, in order to understand the local mixing behaviour and its influence on the local temperature distribution within the homogenization nozzle, the flow conditions in the simultaneous Emulsification and Mixing (SEM)-nozzle were simulated by the average Navier-Stokes equations using the RNG-k-e turbulence model. Based on the results, the kinetics of the cooling effect, which can significantly reduce the coalescence of droplets, could be estimated.

Food Process Engineering Research and Innovation in a Fast Changing World: Paradigms/Case Studies

Part II concentrates on insights gained from model-based numerical simulation offering an improved understanding of underlying mechanisms and – based on this – technical innovations. Two examples from ongoing research emphasize the need to use basic chemical engineering tools in food process engineering and product development research. Specific emphasis is given to material characterization, modern equipment design techniques, and numerical simulation tools. The examples cover the design of new homogenization valves for emulsification and dispersion applications and the design of food extruders for the stabilization and encapsulation of lipophilic bioactive components, as utilized for the manufacture of functional foods.