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 papersMeasuring and modelling how foods flow, deform, break and transfer heat: rheometry of fluids and gels, viscoelasticity, texture profile analysis, and thermal, electrical and optical properties. Agricultural Engineering's engineering-properties-biomaterials covers size, shape, density and friction of grains and produce; this subject goes deeper into processed foods and their measurement.
In the exams: ICAR AIEEA-PG Code 18 Units I–II (physical properties of foods; engineering properties of food materials); ICAR AICE 37 Unit 5 (rheology of dairy foods)
ICAR AIEEA-PG / PGS — Code 18 Food Science Technology
Unit I names physical properties of foods and properties of colloidal systems, gels and emulsions; Unit II names engineering properties of food materials. MCQs test definitions (true, apparent and bulk density, porosity, thermal diffusivity), flow behaviour classes and models, thixotropy, viscometer types, TPA parameters, CIELAB axes, dielectric properties and glass transition.
How our questions for ICAR AIEEA-PG / PGS spread across the units of Physical Properties, Rheology & Texture of Foods. Difficulty: 16 easy, 43 medium, 8 hard.
| Texture: texture profile analysis and empirical texture tests | 9 | |
| Physical properties of foods: density, porosity and particle size distribution | 8 | |
| Fundamentals of rheology: stress, strain and viscosity | 7 | |
| Rheology of doughs and dairy gels | 6 | |
| Colour measurement: CIE L*a*b* and colour difference | 6 | |
| Thermal properties: specific heat, thermal conductivity and diffusivity of foods | 5 | |
| Newtonian and non-Newtonian fluids: power-law, Herschel-Bulkley and Casson models | 5 | |
| Rotational and capillary viscometry | 5 | |
| Viscoelasticity: creep, stress relaxation and oscillatory rheology | 5 | |
| Time-dependent flow: thixotropy and rheopexy | 4 | |
| Electrical and dielectric properties of foods | 4 | |
| Glass transition and state diagrams | 3 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
The volume mean diameter d43 compared with the Sauter mean d32 for a broad distribution is
B. larger, because it weights large particles more
d43 = Σnd⁴/Σnd³ gives more weight to large particles than d32 = Σnd³/Σnd².
Further reading: Sahin and Sumnu, Physical Properties of Foods
A food has k = 0.50 W/m K, ρ = 1,050 kg/m³ and cp = 3,600 J/kg K. Its thermal diffusivity is closest to
D. 1.32 × 10⁻⁷ m²/s
α = k/(ρcp) = 0.50/(1,050 × 3,600) = 1.32 × 10⁻⁷ m²/s. Using cp in kJ gives a value 1,000 times too large; the other two rearrange the formula wrongly.
Further reading: Singh and Heldman, Introduction to Food Engineering
Milk has dynamic viscosity 2.0 mPa s and density 1,030 kg/m³. Its kinematic viscosity is closest to
C. 1.94 mm²/s
ν = μ/ρ = 0.002/1,030 = 1.94 × 10⁻⁶ m²/s = 1.94 mm²/s (cSt). 2.06 multiplies; 515 inverts; 0.002 confuses units.
Further reading: Steffe, Rheological Methods in Food Process Engineering
A purée follows τ = Kγ̇ⁿ with K = 10 Pa sⁿ and n = 0.4. Its apparent viscosity at 50 s⁻¹ is closest to
B. 0.96 Pa s
η = Kγ̇^(n−1) = 10 × 50^(−0.6) = 0.96 Pa s. 47.8 Pa s is the shear stress; 2.09 uses exponent −n; 0.24 is the value at 500 s⁻¹.
Further reading: Steffe, Rheological Methods in Food Process Engineering
Thixotropy differs from shear-thinning in that thixotropy
D. depends on the duration of shearing
Shear-thinning is an immediate response to shear rate; thixotropy is time-dependent at a given rate.
Further reading: Rao, Rheology of Fluid, Semisolid, and Solid Foods
Single-point readings from a spindle ('Brookfield-type') viscometer on a non-Newtonian sauce are
B. comparable only under identical test conditions
The shear rate is undefined for non-Newtonian samples, so readings are empirical apparent viscosities.
Further reading: Steffe, Rheological Methods in Food Process Engineering
A gel has G′ = 1,200 Pa and G″ = 150 Pa. Its loss tangent is
D. 0.125
tan δ = G″/G′ = 150/1,200 = 0.125, mainly elastic. 8.000 inverts the ratio; 1,350 adds the moduli.
Further reading: Rao, Rheology of Fluid, Semisolid, and Solid Foods
The Maxwell model consists of
D. a spring and dashpot in series
Series spring–dashpot (Maxwell) represents a viscoelastic liquid; parallel (Kelvin–Voigt) a viscoelastic solid.
Further reading: Rao, Rheology of Fluid, Semisolid, and Solid Foods
The extensograph measures
B. resistance and extensibility of rested dough
Dough is stretched to rupture after resting; the curve gives resistance, extensibility and energy.
Further reading: Bourne, Food Texture and Viscosity
A tomato paste has a* = 30 and b* = 24. Its chroma C* is closest to
D. 38.4
C* = √(30² + 24²) = 38.4. 54.0 adds; 6.0 subtracts; 1.25 is the a*/b* ratio.
Further reading: Sahin and Sumnu, Physical Properties of Foods
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