Agricultural/Bioengineering Food Processing Unit Operation 4

Question 1

In a continuous screw conveyor used to move grain, doubling the screw pitch while keeping rotational speed constant will:

Accepted Answer

Double the conveying capacity

Answer

Conveyor capacity is directly proportional to pitch distance; doubling pitch moves twice the material per revolution at the same RPM.

Question 2

The F₀ value in thermal process calculation represents:

Accepted Answer

The time in minutes at 121.1°C (250°F) that delivers an equivalent lethal effect to the actual process

Answer

F₀ is the equivalent processing time at the reference temperature of 121.1°C, integrating the lethal effect of the actual time-temperature profile.

Question 3

Which mechanism dominates heat transfer in a can of solid-pack tuna during retort processing?

Accepted Answer

Conduction from the can wall through the product

Answer

Solid-pack tuna has no free liquid, so heat must conduct slowly through the dense fish tissue from the container wall to the thermal center.

Question 4

A food plant evaporator operates as a triple-effect system. Compared to a single-effect evaporator with the same evaporation duty, steam economy is approximately:

Accepted Answer

Three times better (uses ~1/3 the steam)

Answer

In a triple-effect evaporator, steam from one effect heats the next, so roughly 1 kg of steam can evaporate ~3 kg of water, tripling steam economy.

Question 5

In size reduction of grains, Rittinger's law states that energy required is proportional to:

Accepted Answer

The new surface area created during grinding

Answer

Rittinger's law applies to fine grinding and holds that energy input is proportional to the new surface area generated during comminution.

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Food Processing Unit Operation 4