ICAR AIEEA-PG: Dairy Science (group 16) and Dairy Technology (group 17) · 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 AIEEA-PG — Dairy Science (group 16)
Classification of milk microbes by growth temperature, spoilage, antimicrobial systems, grading of raw milk (SPC, MBRT, resazurin), mastitic milk, and the bacteriology of thermisation, pasteurisation, boiling, sterilisation, UHT, bactofugation and membrane filtration.
How our questions for ICAR AIEEA-PG spread across the units of Microbiology of Raw & Market Milk. Difficulty: 30 easy, 49 medium, 11 hard.
| Psychrotrophs, mesophiles, thermodurics and thermophiles | 10 | |
| 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 | |
| Sources of contamination: udder, animal, milker, equipment, water, air | 7 | |
| 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 | |
| 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.
Psychrotrophs are defined as bacteria that:
A. Grow at 7 degrees Celsius or below, whatever their optimum
The definition is ability to grow at 7 C or below; psychrophiles have optima at 15 C or below; thermodurics survive pasteurisation.
Further reading: Robinson (ed.), Dairy Microbiology Handbook
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
Psychrotroph enzymes are a problem in UHT milk mainly because they:
C. Partly survive UHT treatment
Enzymes produced in raw milk survive heat and act in storage; the bacteria are killed.
Further reading: Robinson (ed.), Dairy Microbiology Handbook
Which mastitis pathogen is classed as contagious?
A. Staphylococcus aureus
S. aureus spreads cow to cow at milking; the others are environmental.
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
The 72 degrees Celsius for 15 seconds pasteurisation standard was confirmed to inactivate which more heat-resistant pathogen?
A. Coxiella burnetii
Coxiella, the Q-fever agent, is slightly more heat-resistant than M. tuberculosis; spores survive pasteurisation.
Further reading: Robinson (ed.), Dairy Microbiology Handbook
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
Ten here, 90 in the app. The Laisha app has every practice question we have written to ICAR AIEEA-PG 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.
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