Extrusion Flashcards
Extrusion cooking
a short-time process in which food material is cooked by a combination of temperature, moisture, mechanical shear, and pressure, as it is forced through a die
Die
a plate with a restricted opening used to form the extrudates (shapes)
Extruder
a complete processing unit that mixes, cooks, forms, and shears all in one process allowing formulations and conditions to be changed in-stream
Advantages of extrusion
higher throughput, continuous unit operation
lower processing costs
shorter cooking time
reduces/eliminates microorganisms
minimizes flavour and nutrient losses
Extruder Applications
Ready to eat breakfast cereals
snackes and confectionary products
infant foods
pet food
pasta
co-extruded products
Types of extruder
Single screw and twin screw
Single screw extruder
lower capital and maintenance costs
poorer thermal transfer
high throughput
Twin screw extruder
higher capital costs
enhanced mixing and flow
wider range of control
able to accommodate 2 different types of ingredients at once
3 zones of an extruder
feed/mixing zone, cooking zone, and high pressure/forming zone
Mixing/feeding zone
Raw ingredients are added and mixed by the screws
Cooking zone
dough is subjected to heat
High pressure/forming zone
mix will be pushed through a die and take that shape (may also expand)
Materials low in proteins (high in starch) expand ______ to produce _____ dense products
greatly, less
Materials high in protein (low in starch) expand _____ to produce ______ dense product
less, more
How does moisture content affect extrusion
Low moisture = increased expansion
High moisture = artificial meats
