Agricultural/Bioengineering Agricultural/Bioengineering: Food Engineering 3

Question 1

High-pressure processing (HPP) of food at 600 MPa is most effective at inactivating:

Accepted Answer

Vegetative bacteria and most viruses

Answer

HPP at commercial pressures (400–600 MPa) effectively inactivates vegetative bacteria, yeasts, and molds but is largely ineffective against bacterial spores and prions.

Question 2

Water activity (aw) of 0.85 represents the approximate lower limit for growth of:

Accepted Answer

Most spoilage bacteria

Answer

Most spoilage bacteria require aw above 0.91–0.95, while 0.85 is near the lower limit for the most salt-tolerant bacteria.

Question 3

In freeze-drying, the primary drying stage involves:

Accepted Answer

Sublimation of ice directly to vapor under vacuum

Answer

Primary drying in freeze-drying removes ice by sublimation — the direct solid-to-vapor phase transition — under high vacuum and controlled low temperature.

Question 4

The emulsifying capacity of soy protein isolate is mainly attributed to its:

Accepted Answer

Amphiphilic structure with both hydrophilic and hydrophobic regions

Answer

Soy proteins stabilize emulsions by adsorbing at the oil-water interface due to their amphiphilic structure, which has both water-loving and fat-loving regions.

Question 5

Which packaging atmosphere modification is used to slow ripening and extend shelf life of fresh-cut produce?

Accepted Answer

Reduced O2 and elevated CO2

Answer

Modified atmosphere packaging for fresh-cut produce uses low O2 (2–5%) and elevated CO2 (5–10%) to reduce respiration rate and microbial growth.

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Agricultural/Bioengineering: Food Engineering 3