Agricultural/Bioengineering Agricultural/Bioengineering: Food Engineering 5

Question 1

The 'glass transition temperature' (Tg) of a food system is important because below Tg:

Accepted Answer

Molecular mobility is greatly reduced, improving stability

Answer

Below Tg, the amorphous food matrix becomes a rigid glass with very low molecular mobility, dramatically slowing diffusion-limited deterioration reactions and microbial growth.

Question 2

In the context of frying, the 'oil uptake' by a fried food product is primarily driven by:

Accepted Answer

Condensation vacuum created as steam exits and the product cools after frying

Answer

Most oil uptake occurs post-frying as the product cools: steam that had been escaping condenses, creating a partial vacuum that draws surface oil into the porous crust.

Question 3

Which analytical technique is most commonly used to determine fat content in food products by solvent extraction?

Accepted Answer

Soxhlet extraction

Answer

The Soxhlet method uses repeated cycling of an organic solvent (e.g., hexane or petroleum ether) to continuously extract fat from a dried food sample.

Question 4

The pasteurization of egg products at 60°C for 3.5 minutes is designed primarily to destroy:

Accepted Answer

Salmonella species

Answer

Liquid egg pasteurization targets Salmonella, the primary pathogen of concern in shell eggs, using the minimum time-temperature combination that achieves a sufficient log reduction.

Question 5

In food fermentation, heterofermentative lactic acid bacteria (LAB) produce lactic acid and also:

Accepted Answer

CO2 and ethanol or acetic acid as byproducts

Answer

Heterofermentative LAB use the phosphoketolase pathway, producing equimolar amounts of lactic acid, CO2, and either ethanol or acetic acid from glucose.

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Agricultural/Bioengineering: Food Engineering 5