ICAR AIEEA-PG / PGS Extrusion & Texturisation Technology: practice questions

1 · Principles of extrusion cooking · easy

Extrusion cooking is best described as a

1. low-temperature long-time process
2. freezing process
3. fermentation process
4. high-temperature short-time process

2 · Principles of extrusion cooking · medium

In many cooking extruders, most of the heat comes from

1. electric heaters mounted inside the hollow screw shaft
2. microwave sources in the barrel
3. viscous dissipation of mechanical energy
4. radiation from the die

3 · Principles of extrusion cooking · medium

Forming (cold) extrusion differs from cooking extrusion in that it

1. always operates above 150 °C
2. produces only expanded snacks with very high porosity
3. shapes without significant cooking or expansion
4. needs no die

4 · Single-screw extruders: flow and pressure · medium

Grooved barrels are used in single-screw food extruders to

1. prevent slip at the barrel wall
2. heat the material by radiation
3. separate fat from the melt
4. reduce die pressure

5 · Twin-screw extruders: configuration and screw elements · medium

Food twin-screw extruders commonly have length-to-diameter ratios of about

1. 2–4
2. 200–400
3. 0.2–0.4
4. 20–40

6 · Starch transformations during extrusion · easy

At the low moisture of extrusion, starch granules are transformed mainly by

1. swelling of granules in excess water, as in a sauce
2. fermentation by yeasts
3. freezing and thawing
4. shear and heat disrupting and melting them

7 · Starch transformations during extrusion · medium

Vitamins are usually added to extruded cereals

1. after extrusion, by spraying or coating
2. before extrusion, so that they survive the barrel heat
3. only in the die
4. never

8 · Protein texturisation: low-moisture and high-moisture extrusion · medium

Fibrous structure in extruded plant proteins is fixed mainly by

1. ionising radiation
2. adding meat fibres
3. disulphide and non-covalent bonds after alignment
4. freezing the extrudate rapidly in liquid nitrogen after cutting

9 · Protein texturisation: low-moisture and high-moisture extrusion · easy

Rehydrated TVP typically absorbs water equal to about

1. one-tenth of its weight
2. ten times its weight
3. two to three times its weight
4. none of its weight

10 · Pasta and cold-forming extrusion · easy

Dried pasta is dried to a final moisture of about

1. 30 %, the dough moisture before drying
2. 50 %, to keep it soft in the pack
3. 0 %, removing every trace of water
4. 12 %