ICAR AIEEA-PG / PGS — Code 18 Food Science Technology · India · ICAR through the National Testing Agency
Original practice questions written to the published syllabus · not past papersMicroorganisms and enzymes put to work: starter cultures, the microbiology of fermented foods, industrial fermenter design and operation, downstream recovery, and the modern biotechnology (recombinant enzymes, precision fermentation, single-cell protein) that is reshaping ingredients.
In the exams: GATE XE-G and XL-U Section 2 (fermented foods and beverages); ICAR AICE 35.a Unit 6 (food microbiology and biotechnology)
How our questions for ICAR AIEEA-PG / PGS spread across the units of Fermentation Technology & Food Biotechnology. Difficulty: 24 easy, 51 medium, 3 hard.
| Fermented dairy foods: curd, yoghurt and cheese microbiology | 8 | |
| Fermented cereal and legume foods: idli, dosa, tempeh, miso and soy sauce | 8 | |
| Fermented meat and fish products | 8 | |
| Recombinant DNA technology and GM foods | 8 | |
| Starter culture production, preservation and bacteriophage control | 7 | |
| Fermented vegetables: sauerkraut, kimchi and pickles | 7 | |
| Vinegar fermentation | 6 | |
| Precision fermentation and its regulation | 6 | |
| Production of food enzymes, organic acids, amino acids and flavours by fermentation | 5 | |
| Lactic acid bacteria, yeasts and moulds as starter cultures | 4 | |
| Single-cell protein and single-cell oil | 4 | |
| Fermenter design, aeration and agitation | 3 | |
| Downstream processing: separation and purification of fermentation products | 3 | |
| Batch, fed-batch and continuous fermentation kinetics | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which set of properties describes lactic acid bacteria?
B. Gram-positive, catalase-negative, non-spore-forming, acid-tolerant
Lactic acid bacteria are Gram-positive, catalase-negative, non-sporing and aerotolerant, and tolerate the acid they make. Spore-formers (Bacillus, Clostridium) and Gram-negative aerobes (Pseudomonas, acetic acid bacteria) are different groups.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
Which organism forms koji for soy sauce and miso?
D. Aspergillus oryzae
Koji is A. oryzae (or A. sojae) grown on a solid substrate, supplying amylases and proteases. R. oligosporus makes tempeh, P. roqueforti blue cheese, and S. cerevisiae bread and alcoholic beverages.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
What is the main advantage of direct vat set cultures over in-plant bulk starter propagation?
D. They avoid the propagation steps where phage entered
Concentrated frozen or freeze-dried cultures go straight into the vat, avoiding the mother-intermediate-bulk chain in which phage and contaminants were picked up, and giving consistent activity. They cost more per tonne, need frozen or dry storage, and still require rotation and hygiene.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
At which peptide bond does chymosin cleave κ-casein?
B. Phe105-Met106
Chymosin specifically hydrolyses the Phe105-Met106 bond of κ-casein, releasing the caseinomacropeptide and destabilising the micelles. Phe23-Phe24 is in αs1-casein and is cleaved by chymosin during ripening, not coagulation; the others are not the coagulation site.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
What is koji in the making of miso and soy sauce?
B. A mould grown on solid substrate for its enzymes
Koji is A. oryzae or A. sojae grown for two to three days on steamed rice, barley or soybean and wheat; its amylases and proteases hydrolyse starch and protein during the later fermentation. The brine, the yeasts and the lactic acid bacteria come later.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
Why is a slow fall in pH during the first hours of sausage fermentation a safety hazard?
C. Staphylococcus aureus multiplies and forms heat-stable enterotoxin
Until the pH and water activity fall, S. aureus can grow in the salted, nitrite-cured mix and form enterotoxin that later drying and cooking do not destroy. The other options misstate the hazards.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
Solid-state fermentation is used for koji and some fungal enzymes. What is its main engineering difficulty?
B. Removing heat and controlling moisture in the bed
With little free water, heat from mould respiration is hard to remove and temperature and moisture gradients form; this limits bed depth and scale. Substrates are moist, not submerged; foaming is a submerged-culture problem; koji moulds need oxygen.
Further reading: Stanbury, Whitaker and Hall, Principles of Fermentation Technology; Doran, Bioprocess Engineering Principles
Which organism produces nearly all the world's citric acid?
A. Aspergillus niger
Submerged fermentation by A. niger on molasses or glucose is the standard process. S. cerevisiae makes ethanol, L. lactis lactic acid, C. glutamicum glutamate and lysine.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
What does the international Cartagena Protocol on Biosafety regulate?
B. Transboundary movement of living modified organisms
The Protocol, under the Convention on Biological Diversity, governs the movement of living modified organisms between countries, including advance informed agreement for some. Pesticide limits, additive labelling and acidity standards are set elsewhere.
Further reading: Codex CAC/GL 44-2003 and related guidelines; Stanbury, Principles of Fermentation Technology
Which human-milk oligosaccharide, made by engineered Escherichia coli, is added to some infant formulas?
B. 2′-Fucosyllactose
2′-FL is the most abundant human-milk oligosaccharide and is produced by precision fermentation for formula. Raffinose is a legume oligosaccharide, inulin a plant fructan, and lactulose a synthetic disaccharide made from lactose.
Further reading: Codex CAC/GL 44-2003 and related guidelines; Stanbury, Principles of Fermentation Technology
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