Food Processing Unit Operation Flashcards
7 cards from real Agricultural/Bioengineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Food Processing Unit Operation flashcards as text
In a continuous screw conveyor used to move grain, doubling the screw pitch while keeping rotational speed constant will:
Answer: Double the conveying capacity
Conveyor capacity is directly proportional to pitch distance; doubling pitch moves twice the material per revolution at the same RPM.
The F₀ value in thermal process calculation represents:
Answer: The time in minutes at 121.1°C (250°F) that delivers an equivalent lethal effect to the actual process
F₀ is the equivalent processing time at the reference temperature of 121.1°C, integrating the lethal effect of the actual time-temperature profile.
Which mechanism dominates heat transfer in a can of solid-pack tuna during retort processing?
Answer: Conduction from the can wall through the product
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.
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:
Answer: Three times better (uses ~1/3 the steam)
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.
In size reduction of grains, Rittinger's law states that energy required is proportional to:
Answer: The new surface area created during grinding
Rittinger's law applies to fine grinding and holds that energy input is proportional to the new surface area generated during comminution.
During evaporative concentration of fruit juice, boiling point elevation (BPE) causes the juice to:
Answer: Boil at a higher temperature than pure water at the same pressure
Dissolved solutes (sugars, acids, minerals) elevate the boiling point above that of pure water at the same pressure, requiring more energy to evaporate.
What is the primary advantage of using a scraped-surface heat exchanger (SSHE) for processing high-viscosity foods like tomato paste?
Answer: It continuously removes the product film from the heat transfer surface, preventing burn-on and maintaining high heat transfer rates
Rotating blades scrape the viscous product off the heated wall, preventing fouling and maintaining the thin boundary layer needed for efficient heat transfer.