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 thermodynamic purpose of using a multi-effect evaporator rather than a single-effect evaporator for milk concentration?
Answer: Each additional effect uses the vapor from the preceding effect as heating steam, dramatically reducing total steam consumption per kg of water evaporated
In a multi-effect evaporator, vapor generated in effect 1 serves as heating medium in effect 2 (at lower pressure/temperature), so a 5-effect unit requires only ~1/5 the steam of a single-effect unit for equal evaporation.
During Cheddar cheese aging, what biochemical reaction is primarily responsible for the development of sharp flavor notes?
Answer: Proteolysis by residual rennet and starter enzymes releasing bitter peptides and free amino acids
Proteolysis breaks down casein into peptides and free amino acids; further catabolism produces volatile compounds (e.g., short-chain fatty acids, sulfur compounds) that define sharp Cheddar flavor.
What is the function of the flow diversion valve (FDV) in an HTST pasteurization system?
Answer: It diverts under-pasteurized milk back to the raw milk balance tank if the required holding temperature is not achieved
The FDV is a safety device that continuously monitors holding tube temperature and automatically diverts forward flow back to the raw side if temperature falls below the legal minimum (72°C/15 s).
In whey protein concentrate (WPC) production, what role does ultrafiltration (UF) play?
Answer: UF removes lactose and minerals through the membrane while retaining whey proteins in the retentate
UF membranes (~10 kDa MWCO) retain whey proteins (β-lactoglobulin, α-lactalbumin, ~15–18 kDa) in the retentate while lactose, salts, and water permeate, producing WPC80 at ~80% protein on a dry basis.
A dairy engineer is designing the holding tube for an HTST system. If the legal minimum hold time is 15 seconds and the pump delivers milk at 20 L/min, what minimum tube volume is required?
Answer: 5.0 liters
Volume = flow rate × time = (20 L/min) × (15 s ÷ 60 s/min) = 5.0 L; the tube must hold at least 5.0 L to guarantee every particle is held for 15 seconds.
What is the primary reason that whey protein denaturation during milk pre-heat treatment (e.g., 90°C/5 min for yogurt) improves yogurt texture?
Answer: Denatured β-lactoglobulin associates with κ-casein on micelle surfaces, increasing water-holding capacity and gel firmness
Upon denaturation, β-lactoglobulin unfolds and covalently links to κ-casein via disulfide bonds, anchoring denatured whey proteins to micelles and creating a denser network that holds water and resists syneresis.
In the context of milk powder production, what is meant by 'instant' or 'agglomerated' powder and why is it produced?
Answer: Instant powder consists of porous clusters of primary particles produced by rewetting and re-drying, improving wettability and dispersibility in water
Agglomeration rewets fine spray-dried particles so they stick together into larger, porous clusters; the increased porosity and capillary action allow water to penetrate quickly, dramatically improving wettability.