Home About My Account Join Renew Contact Careers

DisplayTitle

Stochastic study of flow and expansion of starch-based melts during extrusion – Model development and validation
P. H. Manepalli (1), H. Dogan (1), J. Mathew (2), S. ALAVI (1). (1) Kansas State University, Manhattan, KS, U.S.A.; (2) FritoLay Research & Development, Plano, TX, U.S.A.

Variability in extrusion parameters like moisture content and screw speed lead to the variability in output and results in inconsistency of the product. Stochastic modeling helps in studying the impact of variability of these parameters on the variations in the end product, which helps in better control of the process. Data acquisition system (DAQ) was used to capture the uncertainty in input parameters. A mechanistic model was developed to predict the flow behavior of the melt inside the extruder and bubble growth dynamics in starch-based melts using mass, heat and momentum transfer equations. The model was integrated with a stochastic interface for input of randomly generated process data based on experimentally obtained distributions and output of simulated distributions of end-product properties such as expansion ratio (ER). Corn-meal based corn curls were made using a pilot-scale twin screw extruder and they were used to validate the mechanistic model. The process data were measured at different in-barrel moisture contents (16-24% wet basis) and different screw speeds (250-400 rpm). Different process parameters such as specific mechanical energy (173.89-336.34 kJ/kg), die temperature (107.8-150.7 0C), die pressure (400-1275 kPa) and product characteristics such as ER (3.21-20.46), bubble radius(265-800 microns) and open cell fraction (0-0.34) obtained from the mechanistic model were validated with the experimental results. Variation of 5% in in-barrel moisture content caused 12.16% variation in ER whereas the 5% variation of screw speed resulted in the variation of only 2.94% in ER. This shows that the control of in-barrel moisture content is very important in improving the consistency of the product.

View Presentation