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Ice cream bars<br />
Twin Screw <strong>Extruder</strong>: Two screws rotate in a<br />
figure 8 shaped bore. Advantages:<br />
– throughput independent of feedrate, fluctuations in<br />
production accommodated<br />
– can handle oily, sticky, or wet materials that slip in a<br />
single screw<br />
– Forward and reverse conveying allow greater pressure<br />
control<br />
– Short discharge section, less wear on machine<br />
– Larger variety of feed particle sizes possible<br />
<strong>Extruder</strong> Screw<br />
Extrusion Screw<br />
δ<br />
w<br />
B<br />
θ<br />
Channel<br />
r<br />
Central<br />
shaft<br />
Helical flights<br />
Single and Twin Screw <strong>Extruder</strong>s<br />
Single Screw <strong>Extruder</strong>s: a single screw<br />
with feed, kneading, and cooking/metering<br />
sections.<br />
– Lower capital and operating costs<br />
– Require less skill to operate and maintain<br />
Factors Effecting Nature of Extruded Product<br />
Operating conditions<br />
– Temperature<br />
– Pressure<br />
– Diameter (and shape) of the die<br />
– Shear rate<br />
Rheological properties of the food<br />
apvbaker
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