ICAR AIEEA-PG / PGS — Code 18 Food Science Technology · India · ICAR through the National Testing Agency
Original practice questions written to the published syllabus · not past papersBuilding and using models of food processes: kinetic models of quality and microbial change, numerical solution of heat and mass transfer, computational fluid dynamics, multi-objective optimisation, data-driven and machine-learning models, and digital twins of food plants.
In the exams: PhD research; ICAR AIEEA-PG Code 18 Unit II (system analysis, automation and online data acquisition)
How our questions for ICAR AIEEA-PG / PGS spread across the units of Food Process Modelling, Simulation & Optimisation. Difficulty: 6 easy, 10 medium, 0 hard.
| Modelling simultaneous heat and mass transfer in drying and frying | 5 | |
| Kinetic modelling of quality, nutrient and microbial changes | 4 | |
| Modelling heat transfer in thermal processing | 4 | |
| Types of models: empirical, mechanistic and data-driven | 3 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A food slab of half-thickness 0.01 m (k = 0.5 W/m·K) is cooled with h = 20 W/m²·K. What is the Biot number, and is a lumped model adequate?
B. 0.4; no, internal gradients matter
Bi = hL/k = 20 × 0.01/0.5 = 0.4, above about 0.1, so internal temperature gradients cannot be ignored. 40 inverts k/h; 0.04 uses L = 0.001 m; a value below 1 is not the lumped criterion.
Further reading: Tijskens, Hertog and Nicolaï, Food Process Modelling
Which type of model is derived from conservation laws and transport equations?
B. Mechanistic (white-box)
Mechanistic models use physical, chemical and biological laws; empirical models fit observed data.
Further reading: Tijskens, Hertog and Nicolaï, Food Process Modelling
What is the Fourier number for α = 1.4 × 10⁻⁷ m²/s, t = 1800 s and L = 0.02 m?
C. 0.63
Fo = αt/L² = 1.4 × 10⁻⁷ × 1800/0.0004 = 0.63. 0.0126 forgets to square L; 6.3 and 0.13 slip factors.
Further reading: Tijskens, Hertog and Nicolaï, Food Process Modelling
Using the Ratkowsky model √μ_max = b(T − T_min) with b = 0.03 and T_min = −2 °C, what is μ_max at 8 °C?
B. 0.09 h⁻¹
√μ = 0.03 × (8 + 2) = 0.30, so μ = 0.30² = 0.09 h⁻¹. 0.30 forgets to square; 0.18 uses T − T_min = 6; 0.0009 squares b only.
Further reading: McKellar and Lu, Modeling Microbial Responses in Food
A Weibull survivor curve has shape parameter p = 0.6. What shape does it show?
B. A concave curve with tailing
p < 1 gives tailing; p > 1 a shoulder; p = 1 log-linear.
Further reading: McKellar and Lu, Modeling Microbial Responses in Food
A spore has D₁₂₁ = 4.0 min and z = 10 °C. What is D at 125 °C?
A. 1.59 min
D = 4.0/10^((125 − 121)/10) = 4.0/2.51 = 1.59 min. 1.60 uses a linear 40% reduction; 0.40 applies a full z step; 10.0 multiplies.
Further reading: McKellar and Lu, Modeling Microbial Responses in Food
What is the role of a secondary model in predictive microbiology?
B. Linking primary-model parameters to conditions
Primary models describe curves; secondary models link parameters to temperature, pH, a_w; tertiary models are software.
Further reading: McKellar and Lu, Modeling Microbial Responses in Food
Where is the slowest-heating zone of a liquid heated by natural convection in a still can?
A. Near the bottom of the container
Hot liquid rises along the wall and cooler liquid collects lower down, at about 10–15% of height from the base.
Further reading: Singh and Heldman, Introduction to Food Engineering; Datta, Biological and Bioenvironmental Heat and Mass Transfer
Why are cook values calculated with a z value of 20 to 40 °C or more rather than 10 °C?
C. Quality is less temperature-sensitive than spores
Quality degradation has lower activation energy, hence higher z.
Further reading: Singh and Heldman, Introduction to Food Engineering; Datta, Biological and Bioenvironmental Heat and Mass Transfer
A Page model MR = exp(−ktⁿ) has k = 0.01 min⁻ⁿ and n = 1.2. What is MR after 60 min?
D. 0.26
60^1.2 = 136.1; MR = exp(−0.01 × 136.1) = 0.26. 0.55 uses n = 1 (exp(−0.6)); 0.74 uses t^0.5; 0.01 confuses MR with k.
Further reading: Datta, Biological and Bioenvironmental Heat and Mass Transfer
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