Agricultural/Bioengineering Food Processing Unit Operation 2

Question 1

In a counterflow heat exchanger used for milk pasteurization, which configuration provides the greatest thermal efficiency?

Accepted Answer

Counterflow with product and heating medium flowing in opposite directions

Answer

Parallel flow with equal flow rates

Answer

Cross-flow with baffles directing fluid perpendicular to tubes

Answer

Shell-and-tube with product on the shell side only

Question 2

The Reynolds number in a food processing pipeline is 1,800. What flow regime is present?

Accepted Answer

Laminar flow

Answer

Turbulent flow

Answer

Transitional flow

Answer

Plug flow

Question 3

Which drying method preserves heat-sensitive nutrients best while achieving very low final moisture content?

Accepted Answer

Freeze drying (lyophilization) under vacuum

Answer

Drum drying at atmospheric pressure

Answer

Spray drying with high inlet air temperature

Answer

Fluidized bed drying at 120°C

Question 4

In centrifugal separation of cream from milk, increasing the bowl speed by a factor of 2 increases the centrifugal force by a factor of:

Accepted Answer

4

Answer

2

Answer

8

Answer

16

Question 5

What is the primary purpose of blanching vegetables before freezing?

Accepted Answer

To inactivate enzymes that cause quality deterioration during frozen storage

Answer

To sterilize the product for ambient storage

Answer

To reduce the freezing point of cellular water

Answer

To increase the sugar content through starch hydrolysis

Question 6

In a rotary drum dryer processing grain, the 'critical moisture content' refers to:

Accepted Answer

The point where the drying rate transitions from constant to falling rate

Answer

The equilibrium moisture content at ambient conditions

Answer

The moisture content below which product quality degrades

Answer

The maximum moisture content allowed by food safety regulations

Question 7

A plate-and-frame filter press is operating in constant-pressure filtration. As the filter cake builds up, the filtration rate:

Accepted Answer

Decreases as resistance through the cake grows

Answer

Remains constant because pressure is maintained

Answer

Increases due to improved cake porosity

Answer

Fluctuates cyclically with cake compression