GATE — Engineering Sciences (XE), Section G Food Technology · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papersThe first map of the whole field: what food is, why it deteriorates, and the families of preservation (heat, cold, drying, chemicals, fermentation, irradiation, packaging and hurdles). Each family is studied in depth later; this subject teaches the logic that connects them.
In the exams: GATE XE-G and XL-U Section 3 (processing principles); ICAR AICE-JRF/SRF 35.a Unit 1 (introductory food technology)
How our questions for GATE spread across the units of Principles of Food Science & Food Preservation. Difficulty: 4 easy, 21 medium, 9 hard.
| Preservation by heat: blanching, pasteurisation and sterilisation | 7 | |
| Preservation by removal of water: drying, concentration and intermediate-moisture foods | 6 | |
| Water activity and its relation to spoilage | 4 | |
| Preservation by chemicals, sugar, salt and smoke | 4 | |
| Preservation by irradiation | 3 | |
| Causes of food deterioration: microbial, enzymatic, chemical, physical and pest | 2 | |
| Preservation by low temperature: chilling and freezing | 2 | |
| Hurdle technology | 2 | |
| History, scope and structure of the food industry worldwide | 1 | |
| Food groups, composition and food attributes: colour, texture, flavour and nutrition | 1 | |
| Food fortification and enrichment | 1 | |
| Raw-material quality factors for processing | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Hay-like off-flavours in frozen peas that were not blanched are mainly due to:
A. Lipoxygenase activity during frozen storage
Lipoxygenase oxidises unsaturated fatty acids to volatile off-flavour compounds, even in frozen storage; blanching inactivates it.
Further reading: Fellows, Food Processing Technology
A product keeps 6 months at 30 °C. If Q10 = 2, about how long will it keep at 20 °C?
B. 12 months
Lowering by 10 °C halves the rate when Q10 = 2, doubling shelf life: 6 × 2 = 12 months. 3 months applies the factor the wrong way.
Further reading: Fellows, Food Processing Technology
The D value of a microorganism is the time at a given temperature needed to:
A. Reduce the population by 90%
D is the decimal reduction time: one log cycle, 90% reduction.
Further reading: Fellows, Food Processing Technology
What is the z value?
A. The temperature change that changes the D value tenfold
z links D to temperature; for C. botulinum spores it is taken as 10 °C.
Further reading: Fellows, Food Processing Technology
Taking D121.1 of Clostridium botulinum spores as 0.21 min, what is a 12D process at 121.1 °C?
A. 2.52 min
12 × 0.21 = 2.52 min. 25.2 min is the value at 111.1 °C (D tenfold higher); 12.0 forgets D.
Further reading: Fellows, Food Processing Technology
A product is held at 115 °C for 10 min. Taking z = 10 °C, what is the equivalent lethality F0 at 121.1 °C?
C. About 2.45 min
F0 = 10 × 10^((115 − 121.1)/10) = 10 × 10^−0.61 ≈ 2.45 min. 40.7 inverts the exponent; 10 ignores the temperature difference.
Further reading: Fellows, Food Processing Technology
1,000 kg of fruit at 85% moisture is dried to 12% moisture. What mass of dried product is obtained?
B. 170.5 kg
Solids = 150 kg; product = 150/0.88 = 170.5 kg. 150 kg ignores remaining water; 829.5 kg is the water removed.
Further reading: Fellows, Food Processing Technology
Which radiation sources does the Codex General Standard for Irradiated Foods permit?
A. Gamma rays from cobalt-60 or caesium-137, X-rays and electrons up to 10 MeV
Codex limits sources to those whose energies cannot induce radioactivity in food.
Further reading: Codex CXS 106-1983
A food absorbs 10 kGy. Treating it as water (4.18 kJ/kg K), by about how much does its temperature rise?
C. About 2.4 °C
10 kGy = 10 kJ/kg; ΔT = 10/4.18 ≈ 2.4 °C. That is why irradiation is called a cold process.
Further reading: Fellows, Food Processing Technology
Why do potatoes for crisps and chips need low reducing sugars?
D. Reducing sugars cause dark fry colour and acrylamide formation
Reducing sugars react with asparagine in the Maillard reaction during frying, darkening the product and forming acrylamide.
Further reading: Fellows, Food Processing Technology
Ten here, 34 in the app. The Laisha app has every practice question we have written to GATE 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.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
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