Agricultural/Bioengineering: Dairy Engineering 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 Agricultural/Bioengineering: Dairy Engineering flashcards as text
What is the critical difference between UHT (Ultra-High Temperature) and HTST (High Temperature Short Time) pasteurization in terms of shelf life?
Answer: UHT achieves commercial sterility for ambient shelf life of 6–9 months while HTST requires refrigeration
UHT processing (135–145°C for 2–4 s) achieves commercial sterility, eliminating spore-formers and enabling ambient storage, while HTST (72°C/15 s) only achieves pasteurization requiring cold chain.
In the context of evaporative concentration of milk, what is the significance of operating under vacuum?
Answer: Vacuum lowers the boiling point of water, enabling concentration at temperatures below 70°C to minimize heat damage
Reducing pressure inside the evaporator lowers water's boiling point (e.g., to ~50°C at ~12 kPa), allowing gentle concentration that preserves heat-labile nutrients and flavor.
What is the function of a separator (centrifuge) in a fluid dairy processing line?
Answer: It separates milk into cream and skim milk by exploiting the density difference between fat and plasma
A centrifugal separator applies g-forces up to 6,000–10,000 × g to exploit the ~100 kg/m³ density difference between fat globules and skim milk, yielding cream and skim milk streams.
In yogurt manufacturing, what is the purpose of the incubation temperature of approximately 42–45°C?
Answer: It is the optimal growth temperature for Streptococcus thermophilus and Lactobacillus bulgaricus cultures
42–45°C is the co-optimal temperature for both yogurt starter cultures, maximizing acid production rate and achieving target pH (~4.6) in 4–6 hours.
What does the Gerber method measure in dairy quality testing?
Answer: Fat content of milk by acid digestion and centrifugation in a butyrometer
The Gerber method uses sulfuric acid to dissolve non-fat components and amyl alcohol to promote fat separation, then centrifuges the butyrometer to read fat percentage directly.
In continuous butter making (e.g., Fritz process), what is the role of the working zone following churning?
Answer: It kneads and works the butter to achieve uniform moisture distribution and expel excess buttermilk
The working zone mechanically kneads the butter mass to achieve homogeneous water-in-fat emulsion structure and bring moisture to the legal maximum of 16%.
What is the significance of the 'critical control point' (CCP) in a dairy HACCP plan for fluid milk?
Answer: It is a step where a control measure can be applied to prevent, eliminate, or reduce a food safety hazard to acceptable levels
A CCP is a process step at which a control measure (e.g., pasteurization temperature) can be applied and monitored to prevent or eliminate a food safety hazard.