ICAR AICE-JRF/SRF (PhD) — Food Processing Technology, Food Safety & Quality, Processing and Food Engineering · India · ICAR through the National Testing Agency
Original practice questions written to the published syllabus · not past papersDesigning and validating heat processes that make food safe and shelf-stable: microbial death kinetics, heat penetration, process calculation by the general and formula methods, retorts and aseptic systems, and the regulatory framework for low-acid canned foods. Agricultural Engineering's food-dairy-engineering introduces D, z and F; this subject teaches the full process-establishment practice.
In the exams: GATE XE-G Section 3 (thermal processing) and Section 4 (thermal sterilisation); ICAR AIEEA-PG Code 18 Unit II (thermobacteriology, sterilisation); ICAR AICE 35.a Unit 2 (process time evaluation for canned products)
ICAR AICE-JRF/SRF (PhD) — Food Processing Technology, Food Safety & Quality, Processing and Food Engineering
35.a Unit 2 names thermal processing and process time evaluation for canned products, process optimisation and aseptic canning; 35.a Unit 1 names aseptic preservation; 35.b covers microbiological aspects of sterilisation and UHT. Expect general-method and formula-method reasoning, optimisation for quality (cook value, z of quality factors), particulate aseptic processing and regulatory concepts.
How our questions for ICAR AICE-JRF/SRF spread across the units of Thermal Processing & Canning Technology. Difficulty: 7 easy, 48 medium, 23 hard.
| Thermal death kinetics: D value, z value and the thermal death time curve | 8 | |
| Process calculation: Ball's formula method | 7 | |
| Regulatory control of low-acid canned foods and process authorities | 7 | |
| Heat penetration tests and cold-spot determination | 6 | |
| Can making, double seams and seam evaluation | 6 | |
| Retort types: still, rotary, hydrostatic and continuous | 6 | |
| Retort pouches and flexible containers | 6 | |
| Aseptic processing and packaging | 6 | |
| Process calculation: the general method | 5 | |
| Quality optimisation: cook value and nutrient retention | 5 | |
| Lethality, F0 and the 12D concept | 4 | |
| Acid and low-acid foods; pH 4.6 and the target organism | 4 | |
| Commercial sterility and spoilage probability | 4 | |
| Pasteurisation of acid and acidified foods | 4 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
An organism has D₁₁₀ = 3.0 min and z = 10 °C. Its D at 121.1 °C is closest to
D. 0.23 min
D₁₂₁.₁ = D₁₁₀ × 10^((110 − 121.1)/10) = 3.0 × 10^(−1.11) = 3.0 × 0.0776 = 0.23 min. 38.6 min uses the wrong sign, giving a larger D at a higher temperature, which is impossible; 3.33 and 2.70 min multiply or divide by the exponent 1.11 instead of by 10 raised to it.
Further reading: Stumbo, Thermobacteriology in Food Processing
Ball's calculated process time B is 46.2 min and the retort come-up time is 10 min. The operator's process time at retort temperature is closest to
D. 42.0 min
Ball credits 42 % of come-up as effective, so Pt = B − 0.42 × CUT = 46.2 − 4.2 = 42.0 min. 36.2 min subtracts the whole come-up; 50.4 min adds the credit instead of subtracting it; 41.6 min uses 46 % instead of 42 %.
Further reading: Stumbo, Thermobacteriology in Food Processing
In Ball's formula B = fh log(jh Ih / g), if a product's fh doubles while everything else stays the same (including g), the process time B
A. doubles, because B is directly proportional to fh
fh multiplies the logarithmic term, so B is proportional to fh; a larger fh means slower heating. fh is outside the logarithm, not inside, and it is not an indicator of faster heating.
Further reading: Stumbo, Thermobacteriology in Food Processing
The inner layer of a typical retortable pouch, which forms the heat seal, is usually made of
B. polypropylene
Cast polypropylene is used as the sealant because it seals well and withstands retort temperatures. Polyester is the outer strength and print layer; aluminium foil is the barrier layer; nylon is sometimes added for puncture resistance, not sealing.
Further reading: Holdsworth and Simpson, Thermal Processing of Packaged Foods
Compared with a cylindrical can of the same volume, a retort pouch generally needs a shorter process time because
C. its thin profile shortens the heat path
The slab-like shape gives a short path to the centre, so the cold spot heats faster. Laminates do not conduct better than metal; the F₀ target is the same; contents may still heat by conduction. The heat path meant is the distance heat must travel to the cold spot.
Further reading: Holdsworth and Simpson, Thermal Processing of Packaged Foods
In an aseptic line, a flow-diversion valve after the holding tube is required to
C. send product back for reprocessing automatically if outlet temperature falls below the set point
Flow diversion ensures that product not held at the scheduled temperature never reaches the sterile filler. It is a safety device, not a flow splitter, pressure relief or dosing valve.
Further reading: Singh and Heldman, Introduction to Food Engineering
Juice HACCP rules in the United States require processors to achieve a reduction of the most resistant pertinent pathogen of at least
B. 5 log
21 CFR 120 requires a 5-log reduction of the pertinent microorganism. 12 log is the botulinum criterion for low-acid canning; 1 and 3 log are too small.
Further reading: US FDA, 21 CFR Parts 108, 113 and 114
A processor wants to improve the colour of a convection-heating vegetable soup without reducing safety. Which change is most likely to help?
C. Process at a higher retort temperature with agitation for a shorter time to the same F₀
Higher temperature and agitation give the same F₀ with less quality damage for convection products. Lowering temperature increases cooking; reducing F₀ below the safety target is unacceptable; less headspace reduces mixing and slows heating.
Further reading: Holdsworth and Simpson, Thermal Processing of Packaged Foods
The international Codex text that sets hygiene requirements for low-acid canned foods is the
D. Code of Hygienic Practice for Low-Acid and Acidified Low-Acid Canned Foods
The Code of Hygienic Practice for Low-Acid and Acidified Low-Acid Canned Foods covers scheduled processes, retort operation, containers and records. The other Codex texts cover labelling, aflatoxin and additives.
Further reading: Codex Code of Hygienic Practice for Low-Acid and Acidified Low-Acid Canned Foods
Records required for each retort load of a low-acid canned food include
D. retort temperature records, reference thermometer readings and processing times
Processing records prove the scheduled process was delivered and are reviewed before release. Commercial information is not part of process records.
Further reading: US FDA, 21 CFR Parts 108, 113 and 114
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