Shear Conversion of Corn Meal by Reverse Screw Elements during Twin‐Screw Extrusion at Low Temperatures

Abstract

MATERIALS & METHODSCorn meal was extruded in a twin-screw extruder to study effects of one and two reverse-screw elements on conversion at extrusion temperatures < 60°C. Significant conversion was observed across the reverse-screw elements. The conversion was due to shear alone, since thermal effect was negligible at these low temperatures. Encompassing the reverse-screw elements were four visually distinct zones characterized by the state of the material.

Twin Screw Extrusion of Pink Salmon Muscle: Effect of Mixing Elements and Feed Composition

“…Reverse screw element has a strong flow restricting effect and therefore incorporation of RSE will result TWIN-SCREW EXTRUSION 273 in higher degree of fill (Colonna er al. 1983;Yam et al 1994). This is due to the fact that larger filled length is required to develop pressure for flow of material across the reverse screw element@).…”

“…The extent of physicochemical changes during extrusion affects AD. Gelatinization, the major physicochemical change during extrusion of starch rich ingredients, is affected by temperature, moisture content, screw speed, and feed flow rate (Bhattacharya and Hanna 1987) and screw configuration (Gogoi 1994;Yam et al 1994;Owusu-Ansah er al. 1983).…”

Twin Screw Extrusion of Pink Salmon Muscle: Effect of Mixing Elements and Feed Composition

“…Reverse screw element has a strong flow restricting effect and therefore incorporation of RSE will result TWIN-SCREW EXTRUSION 273 in higher degree of fill (Colonna er al. 1983;Yam et al 1994). This is due to the fact that larger filled length is required to develop pressure for flow of material across the reverse screw element@).…”

“…The extent of physicochemical changes during extrusion affects AD. Gelatinization, the major physicochemical change during extrusion of starch rich ingredients, is affected by temperature, moisture content, screw speed, and feed flow rate (Bhattacharya and Hanna 1987) and screw configuration (Gogoi 1994;Yam et al 1994;Owusu-Ansah er al. 1983).…”

Reverse Screw Element(s) and Feed Composition Effects during Twin‐Screw Extrusion of Rice Flour and Fish Muscle Blends

“…Reverse screw elements are very strong flow restricting elements. The more severe the screw configuration due to longer RSE(s), the greater was the degree of fill (Yam et al, 1994). This is because a larger filled length is required to build up pressure for flow of material across the RSE(s).…”

Tribological Shear Conversion of Starch

“…That amount of conversion was achieved by tribological shearing (friction) of granules in the extruder if the moisture content in the starch feed was 35%. Yam et al (1994) analyzed materials along the screw channel after "dead-stop" of a steady state twin screw extrusion of corn meal with 20% moisture. They reported that up to conversion between 20 and 32% the material was obviously in a powdery state.…”

Twin Screw Extrusion of Pink Salmon Muscle: Effect of Mixing Elements and Feed Composition

“…Reverse screw element has a strong flow restricting effect and therefore incorporation of RSE will result TWIN-SCREW EXTRUSION 273 in higher degree of fill (Colonna er al. 1983;Yam et al 1994). This is due to the fact that larger filled length is required to develop pressure for flow of material across the reverse screw element@).…”

“…The extent of physicochemical changes during extrusion affects AD. Gelatinization, the major physicochemical change during extrusion of starch rich ingredients, is affected by temperature, moisture content, screw speed, and feed flow rate (Bhattacharya and Hanna 1987) and screw configuration (Gogoi 1994;Yam et al 1994;Owusu-Ansah er al. 1983).…”

Reverse Screw Element(s) and Feed Composition Effects during Twin‐Screw Extrusion of Rice Flour and Fish Muscle Blends

“…Reverse screw elements are very strong flow restricting elements. The more severe the screw configuration due to longer RSE(s), the greater was the degree of fill (Yam et al, 1994). This is because a larger filled length is required to build up pressure for flow of material across the RSE(s).…”

Tribological Shear Conversion of Starch

“…That amount of conversion was achieved by tribological shearing (friction) of granules in the extruder if the moisture content in the starch feed was 35%. Yam et al (1994) analyzed materials along the screw channel after "dead-stop" of a steady state twin screw extrusion of corn meal with 20% moisture. They reported that up to conversion between 20 and 32% the material was obviously in a powdery state.…”

Twin Screw Extrusion of Pink Salmon Muscle: Effect of Mixing Elements and Feed Composition

“…Reverse screw element has a strong flow restricting effect and therefore incorporation of RSE will result TWIN-SCREW EXTRUSION 273 in higher degree of fill (Colonna er al. 1983;Yam et al 1994). This is due to the fact that larger filled length is required to develop pressure for flow of material across the reverse screw element@).…”

“…The extent of physicochemical changes during extrusion affects AD. Gelatinization, the major physicochemical change during extrusion of starch rich ingredients, is affected by temperature, moisture content, screw speed, and feed flow rate (Bhattacharya and Hanna 1987) and screw configuration (Gogoi 1994;Yam et al 1994;Owusu-Ansah er al. 1983).…”

Reverse Screw Element(s) and Feed Composition Effects during Twin‐Screw Extrusion of Rice Flour and Fish Muscle Blends

“…Reverse screw elements are very strong flow restricting elements. The more severe the screw configuration due to longer RSE(s), the greater was the degree of fill (Yam et al, 1994). This is because a larger filled length is required to build up pressure for flow of material across the RSE(s).…”

Tribological Shear Conversion of Starch

“…That amount of conversion was achieved by tribological shearing (friction) of granules in the extruder if the moisture content in the starch feed was 35%. Yam et al (1994) analyzed materials along the screw channel after "dead-stop" of a steady state twin screw extrusion of corn meal with 20% moisture. They reported that up to conversion between 20 and 32% the material was obviously in a powdery state.…”