Agricultural/Bioengineering Agricultural/Bioengineering: Dairy Engineering 4

Question 1

When sizing a cooling system for a raw milk receiving tank, which parameter is most critical for preventing microbial growth?

Accepted Answer

Achieving 4°C within 2 hours of milking to slow mesophilic bacterial growth

Answer

Grade A PMO standards require raw milk be cooled to ≤4.4°C (40°F) within 2 hours to inhibit mesophilic pathogens while preventing freezing.

Question 2

In lactose crystallization for the production of lactose monohydrate powder, what is the primary role of the 'seed' crystals added to the supersaturated lactose solution?

Accepted Answer

Seeds provide nucleation sites to initiate controlled crystal growth and prevent amorphous solidification

Answer

Seeding with fine lactose crystals provides nucleation sites that direct crystal growth in a controlled manner, producing uniform α-lactose monohydrate crystals rather than a glassy amorphous mass.

Question 3

A cheesemaker notices that the curd is too soft and not cutting cleanly after rennet addition. Which corrective action is most appropriate?

Accepted Answer

Extend the coagulation time or increase the CaCl₂ dose to achieve a firmer gel before cutting

Answer

Soft curd indicates incomplete coagulation; extending set time or adding CaCl₂ strengthens the gel network before cutting, preventing curd shattering and fat losses in whey.

Question 4

What is the purpose of standardizing fat content in milk before processing into a product like 2% reduced-fat milk?

Accepted Answer

To comply with legal compositional standards and deliver consistent product to consumers

Answer

Standardization blends cream and skim milk streams to achieve the legally defined fat content (2.0% for reduced-fat milk) required by FDA standards of identity.

Question 5

In an ice cream mix formulation, what is the primary function of an emulsifier such as mono- and diglycerides?

Accepted Answer

They promote partial coalescence of fat globules during freezing, improving overrun stability and texture

Answer

Mono- and diglycerides displace milk proteins from fat globule surfaces, promoting controlled partial coalescence that creates a fat network supporting air bubbles and giving ice cream its characteristic body.

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Agricultural/Bioengineering: Dairy Engineering 4