Physical quality of feed was affected by starch source, screw configuration and steam injection into the barrel. Potato starch gave the highest pellet durability, water stability and hardness. Screw configuration LRLR gave the highest durability, water stability and hardness. Likewise, no steam injection in the barrel gave the highest durability, water stability and hardness. The results also showed that image analysis discriminated among the feeds. Contrast and brightness changed with starch source, but was not affected by other processing parameters such as screw configuration and steam injection. Image analysis alone cannot be used to describe the physical quality such as durability or hardness but it can help explain the process undergone during extrusion, which might explain in part about the physical quality.
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