GATE — Life Sciences (XL), Section U Food Technology · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papersThe newer ways to make food safe or change its structure with less heat damage: high-pressure processing, pulsed electric fields, ohmic, microwave and radio-frequency heating, irradiation, UV, cold plasma and ultrasound — their mechanisms, equipment, validation and regulatory status.
In the exams: GATE XE-G Section 3 (irradiation, hurdle technology); ICAR AICE 35.a Unit 1 (non-thermal and alternate-thermal technologies); ICAR AIEEA-PG Code 18 Unit III (irradiation, microwave processing)
GATE — Engineering Sciences (XE), Section G Food Technology
Section 3 names irradiation and hurdle technology among processing principles. Expect questions on irradiation dose ranges and purposes, units, D10 calculations, and the principles of HPP, PEF and microwave heating within hurdle-based preservation.
GATE — Life Sciences (XL), Section U Food Technology
Same as XE-G; questions often link mechanisms to microbiology — why spores resist, how membranes are damaged.
How our questions for GATE spread across the units of Novel & Non-thermal Food Processing Technologies. Difficulty: 12 easy, 14 medium, 3 hard.
| High-pressure processing: principles, equipment and microbial inactivation | 7 | |
| Food irradiation: dose, sources, effects and labelling | 5 | |
| Microwave and radio-frequency heating | 4 | |
| Ultraviolet light and pulsed light | 4 | |
| Why non-thermal processing: quality and consumer drivers | 3 | |
| Pulsed electric fields | 3 | |
| Ohmic heating | 3 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
The weakness shared by most non-thermal methods is their limited effect on
C. bacterial spores
Spores resist pressure, PEF, UV and most other non-thermal treatments; low-acid shelf-stable foods still need heat.
Further reading: Sun (ed.), Emerging Technologies for Food Processing
The isostatic principle in HPP means that
D. pressure is uniform throughout the product
Pressure is transmitted instantly and evenly, unlike heat, so there is no cold spot.
Further reading: Zhang and others, Nonthermal Processing Technologies for Food
A water-based product at 5 °C is pressurised to 500 MPa. Taking adiabatic heating as 3 °C per 100 MPa, its temperature under pressure is about
C. 20 °C
Rise = 3 × 500/100 = 15 °C, so 5 + 15 = 20 °C. 8 °C counts only 3 °C; 50 °C uses 10 °C per 100 MPa.
Further reading: Zhang and others, Nonthermal Processing Technologies for Food
Field strengths used for PEF pasteurisation of juices are typically about
B. 15–40 kV/cm
Lower fields (about 0.5–3 kV/cm) permeabilise plant tissue; higher fields kill bacteria.
Further reading: Zhang and others, Nonthermal Processing Technologies for Food
PEF pre-treatment of potatoes for French fries is done mainly to
B. soften tissue for easier cutting and less oil uptake
Low-field permeabilisation softens tubers, gives cleaner cuts and lowers oil uptake.
Further reading: Zhang and others, Nonthermal Processing Technologies for Food
A soup with conductivity 1.5 S/m is heated ohmically at 1,500 V/m (ρ = 1,050 kg/m³, cp = 3,800 J/kg K). Its heating rate is about
D. 0.85 K/s
q = σE² = 1.5 × 1,500² = 3.38e+06 W/m³; dT/dt = q/(ρcp) = 0.85 K/s. 0.085 and 8.5 are factor-of-ten slips; the last uses E instead of E².
Further reading: Datta and Anantheswaran, Handbook of Microwave Technology for Food Applications
Domestic microwave ovens operate at
B. 2,450 MHz
2,450 MHz is standard; 915 MHz industrial; 13.56 MHz is an RF band.
Further reading: Datta and Anantheswaran, Handbook of Microwave Technology for Food Applications
Radio-frequency heating is preferred over 2,450 MHz microwaves for tempering large frozen blocks because RF
A. penetrates deeper
Longer wavelengths of RF give deeper, more uniform heating of large blocks.
Further reading: Datta and Anantheswaran, Handbook of Microwave Technology for Food Applications
The unit of absorbed radiation dose is the
A. gray
1 Gy = 1 J/kg; becquerel measures radioactivity.
Further reading: Codex CXS 106-1983, General Standard for Irradiated Foods
The radioactive isotope most used for food irradiation is
A. cobalt-60
Co-60 emits gamma rays of 1.17 and 1.33 MeV; Cs-137 is used less.
Further reading: Codex CXS 106-1983, General Standard for Irradiated Foods
Ten here, 29 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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