ICAR AICE-JRF/SRF (PhD): Dairy Chemistry, Dairy Microbiology, Dairy Technology, Dairy Engineering · India · NTA for ICAR
Original practice questions written to the published syllabus · not past papersWhere milk bacteria come from, how they grow and spoil milk, and how processing changes the count.
In the exams: ICAR AICE subject 36 Unit 3; ICAR AIEEA-PG group 16 (classification by growth temperature, spoilage, grading of raw milk, bacteriological aspects of processing)
ICAR AICE-JRF/SRF (PhD) — Dairy Microbiology (subject 36, Unit 3)
Microbiological quality of milk: sources of contamination, psychrotrophs and their heat-stable enzymes, spoilage, natural antimicrobials, mastitis organisms, grading, the effect of cooling and heat treatments including D, z, B* and C*, bactofugation and microfiltration, biofilms and post-pasteurisation contamination.
How our questions for ICAR AICE-JRF/SRF spread across the units of Microbiology of Raw & Market Milk. Difficulty: 15 easy, 49 medium, 24 hard.
| Psychrotrophs, mesophiles, thermodurics and thermophiles | 9 | |
| Microbiological grading of raw milk: SPC, MBRT and resazurin tests | 9 | |
| Bacteriology of thermisation, pasteurisation, boiling, sterilisation and UHT | 9 | |
| Microbial spoilage: souring, curdling, gassiness, ropiness, proteolysis, lipolysis | 8 | |
| Natural antimicrobial systems in raw milk; the lactoperoxidase system | 7 | |
| Microflora of mastitic milk | 7 | |
| Effect of chilling and storage on raw milk flora | 7 | |
| Bactofugation and microfiltration for bacteria removal | 7 | |
| Post-pasteurisation contamination | 7 | |
| Sources of contamination: udder, animal, milker, equipment, water, air | 6 | |
| Psychrotroph enzymes and their survival of heat treatment | 6 | |
| Biofilms in milking and processing equipment | 6 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
The laboratory pasteurisation count is made by heating the sample at about:
D. 62.8 degrees Celsius for 30 minutes
62.8 C for 30 min simulates batch pasteurisation; 80 C for 10 min is for spore counts.
Further reading: Walstra, Wouters and Geurts, Dairy Science and Technology
The heat-stable alkaline metalloprotease of Pseudomonas fluorescens is often called:
B. AprX
AprX is the Pseudomonas protease; PrtP is a lactococcal cell-envelope proteinase.
Further reading: Walstra, Wouters and Geurts, Dairy Science and Technology
What does the activated lactoperoxidase system require to be added to milk?
C. Thiocyanate and a source of hydrogen peroxide
Codex procedure adds thiocyanate and sodium percarbonate as a peroxide source.
Further reading: Robinson (ed.), Dairy Microbiology Handbook
Why is lactoferrin's antibacterial effect limited in cow milk?
A. Its concentration is low and citrate competes for iron
Cow milk has little lactoferrin, and citrate makes iron available to bacteria.
Further reading: Robinson (ed.), Dairy Microbiology Handbook
Under the international standard, the plate count of milk is incubated at:
C. 30 degrees Celsius for 72 hours
ISO uses 30 C for 72 h; US methods use 32 C for 48 h.
Further reading: Robinson (ed.), Dairy Microbiology Handbook
In the methylene blue reduction test, a longer reduction time indicates:
A. Better quality milk
Fewer active bacteria lower the redox potential more slowly.
Further reading: Robinson (ed.), Dairy Microbiology Handbook
A raw milk count rises from 1,000 to 16,000 cfu per millilitre in 24 hours. What is the generation time?
D. 6 hours
16-fold = 4 generations in 24 h, so g = 6 h. 4 is the number of generations.
Further reading: Walstra, Wouters and Geurts, Dairy Science and Technology
Bactofugation of cheese milk mainly prevents:
B. Late blowing by Clostridium tyrobutyricum
Removing clostridial spores reduces or replaces the need for nitrate or lysozyme.
Further reading: Walstra, Wouters and Geurts, Dairy Science and Technology
Which is the main factor limiting the refrigerated shelf life of conventional pasteurised milk?
B. Post-pasteurisation contamination
Recontamination with psychrotrophs usually decides shelf life.
Further reading: Walstra, Wouters and Geurts, Dairy Science and Technology
In-container sterilisation of milk typically uses about:
B. 110 to 120 degrees Celsius for 10 to 20 minutes
UHT uses 135-150 C for seconds; pasteurisation uses 63 or 72 C.
Further reading: Walstra, Wouters and Geurts, Dairy Science and Technology
Ten here, 88 in the app. The Laisha app has every practice question we have written to ICAR AICE-JRF/SRF 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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