ICAR AIEEA-PG — Agricultural Engineering & Technology (Major Subject Group 10) · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersUnit operations of food and milk plants: balances, fluid flow, heat exchange, thermal processing, evaporation, separation, freezing and hygienic design.
In the exams: GATE AG Section 7 (~9 marks a year 2019–26; thermal processing in all 8 papers); ICAR AICE subject 38; ICAR AIEEA-PG Unit VI; NCEES PE processing
ICAR AIEEA-PG — Agricultural Engineering & Technology
Unit VI MCQs cover processing and dairy operations at definition level: HTST and LTLT conditions, the phosphatase test, regeneration, types of heat exchangers, evaporators and driers, homogenisation purpose, membrane classes, freezing methods and CIP sequence, with short direct calculations.
How our questions for ICAR AIEEA-PG spread across the units of Food & Dairy Engineering. Difficulty: 33 easy, 10 medium, 0 hard.
| Material and energy balances | 5 | |
| Thermal processing kinetics: D, z and F values | 5 | |
| Pasteurisation: HTST and LTLT | 4 | |
| Evaporation: single and multiple effect | 4 | |
| Freezing and Plank's equation | 4 | |
| Fluid flow in food plants: pumps, pipes and rheology | 3 | |
| Spray and drum drying | 3 | |
| Centrifugation and cream separation | 3 | |
| Filtration and membrane processes: MF, UF, NF and RO | 3 | |
| Cleaning-in-place and sanitary design | 3 | |
| Heat exchangers: plate, tubular and scraped-surface | 2 | |
| UHT processing and sterilisation | 2 | |
| Homogenisation | 2 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
HTST and UHT processes preserve quality better than long, lower-temperature processes of equal lethality because
A. Quality attributes have larger z values than bacterial spores
A larger z means a slower increase in rate with temperature. Raising temperature accelerates spore death (z ≈ 10 °C) much more than quality loss (z typically 25–50 °C), so short hot processes win.
Further reading: Singh and Heldman, Introduction to Food Engineering
A first-order death rate constant k = 0.0921 s⁻¹ corresponds to a D value of
A. 25 s
D = 2.303/k = 2.303/0.0921 = 25.0 s. 1/k = 10.9 s is the time for a 1/e reduction, not a decimal reduction. 2.5 s uses 0.2303 instead of 2.303.
Further reading: Singh and Heldman, Introduction to Food Engineering
The classical minimum time–temperature combination for HTST pasteurisation of milk is
D. 72 °C for 15 s
HTST is 72 °C for 15 s and LTLT 63 °C for 30 min (Codex and most national codes; local law may add margins). 135 °C for seconds is UHT.
Further reading: Codex CXC 57-2004
If the milk temperature at the end of the holding tube falls below the legal set point, the
A. Flow diversion valve returns the milk to the balance tank
The recorder-controller at the holding-tube outlet actuates the flow diversion valve, sending under-processed milk back for reprocessing.
Further reading: Singh and Heldman, Introduction to Food Engineering
Evaporators for milk operate under vacuum mainly to
C. Lower the boiling temperature and protect heat-sensitive components
Lower pressure lowers boiling point, reducing heat damage such as browning and protein denaturation, and increases the temperature difference available.
Further reading: Singh and Heldman, Introduction to Food Engineering
The main purpose of homogenising market milk is to
A. Reduce fat globule size so that a cream layer does not form
Smaller globules rise far more slowly (Stokes' law), preventing creaming during shelf life. Homogenisation does not kill organisms or change fat content.
Further reading: Bylund, Dairy Processing Handbook
In constant-pressure cake filtration with negligible medium resistance, 1 m³ of filtrate is collected in 10 min. The time to collect 3 m³ is
C. 90 min
Time is proportional to V² when medium resistance is negligible: 10 × 3² = 90 min. Linear scaling gives 30 min. 270 min uses V³; 17.3 min inverts the relation (t ∝ √V).
Further reading: Earle, Unit Operations in Food Processing
Rapid freezing gives better texture in thawed fruit and vegetables than slow freezing because it forms
B. Many small ice crystals, largely inside cells
Fast freezing gives many small crystals with less cell damage and drip; slow freezing gives large extracellular crystals that rupture tissue.
Further reading: Singh and Heldman, Introduction to Food Engineering
Individually quick frozen (IQF) peas are usually produced in a
D. Fluidised-bed freezer
Upward cold air suspends small particles so each freezes separately and fast. Plate freezers suit flat blocks; scraped-surface freezers are for ice-cream mix.
Further reading: Singh and Heldman, Introduction to Food Engineering
Which feature is contrary to hygienic design of food-contact pipework?
C. A long dead-leg branch where product stagnates
Dead legs are not reached by CIP flow and harbour micro-organisms. The other features are recommended by EHEDG, 3-A and ISO 14159 principles.
Further reading: EHEDG Guidelines; 3-A Sanitary Standards
Ten here, 43 in the app. The Laisha app has every practice question we have written to ICAR AIEEA-PG in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
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