Question

The extruded product usually puffs and changes texture as it is extruded because of the reduction of forces and release of moisture and heat. The extent to which it does so is known as:

• A. Residence time
• B. Expansion ratio
• C. Cooking time
• D. Cooking rate

Hint:

The expansion ratio is affected by the starch content, moisture level, and temperature of the melt. Higher starch and lower moisture usually result in higher expansion.

Answer 1

The Correct Option is B

Inside an extruder, high pressure keeps the water in the product from turning into steam, but the moment the product exits the die into normal atmospheric pressure, that water flashes into steam almost instantly, puffing the product up and giving it its light, porous texture. How much this puffing happens is measured by comparing the cross sectional area of the extruded product to the area of the die opening it came out of. This measurement of how much the product expands is called the expansion ratio.