Use of a dual orifice die for on-line extruder measurement of flow behavior index in starchy foods Original Research Article

A new method for the measurement of flow behavior index was tested using low density polyethylene (LDPE), corn meal, and waxy and dent corn starches. A specially designed dual orifice capillary die was attached to a pilot scale twin screw extruder, enabling two flow rates to be collected at one extruder condition. The power law index was determined using a ratio of these flow rates and the known lengths and radii of the capillaries. This method provides a more accurate and time efficient determination of the power law index of extruded food materials than is currently available. Values obtained for the LDPE (n=0.47–0.67) were similar to those obtained with a capillary rheometer (n=0.49). Likewise, values measured for corn meal (n=0.34–0.58) and for waxy and dent corn starches (n=0.62–0.72 and 0.40–0.43, respectively) compared well to literature values and followed expected trends.