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 papers
7worked here, free
23written to this exam in this subject
13syllabus units
What this subject covers
The minor constituents that decide colour, flavour and nutritional value, the enzymes that act in raw and processed food, and the browning reactions — enzymatic and non-enzymatic — that every food technologist must control or exploit.
In the exams: GATE XE-G and XL-U Section 1 (pigments, flavours, enzymes, browning); ICAR AIEEA-PG Code 18 Unit I (food flavours); ICAR AICE 35.a Unit 7 (flavour chemistry technology)
Pigments: chlorophylls, carotenoids, anthocyanins, betalains, tannins and myoglobin
Colour changes during processing and storage
Flavour chemistry: terpenes, esters, aldehydes, ketones and sulphur compounds
Taste: sweet, sour, salty, bitter and umami compounds
Flavour generation during processing, fermentation and maturation
Vitamins: stability during processing and storage
Minerals in foods and their chemistry
Food enzymes: specificity, kinetics, inhibition and coenzymes
Endogenous enzymes in raw materials: lipoxygenase, polyphenol oxidase, peroxidase and pectinases
Industrial enzymes in food processing
Enzymatic browning and its control
Maillard reaction and caramelisation
Acrylamide and other process contaminants from browning
Phenolic compounds and natural antioxidants
Where the 23 questions fall
How our questions for ICAR AICE-JRF/SRF spread across the units of Food Chemistry II: Pigments, Flavours, Vitamins, Minerals, Enzymes & Browning. Difficulty: 1 easy, 7 medium, 15 hard.
Colour changes during processing and storage
3
Flavour generation during processing, fermentation and maturation
3
Acrylamide and other process contaminants from browning
3
Flavour chemistry: terpenes, esters, aldehydes, ketones and sulphur compounds
2
Food enzymes: specificity, kinetics, inhibition and coenzymes
2
Industrial enzymes in food processing
2
Phenolic compounds and natural antioxidants
2
Taste: sweet, sour, salty, bitter and umami compounds
1
Vitamins: stability during processing and storage
1
Minerals in foods and their chemistry
1
Endogenous enzymes in raw materials: lipoxygenase, polyphenol oxidase, peroxidase and pectinases
1
Enzymatic browning and its control
1
Maillard reaction and caramelisation
1
7 practice questions, worked
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
1 · Flavour chemistry: terpenes, esters, aldehydes, ketones and sulphur compounds · hard
What causes the 'skunky' light-struck flavour of beer in clear bottles?
Dimethyl sulphide released by the malt during light exposure in the brewhouse
3-Methyl-2-butene-1-thiol from photodegraded hop iso-α-acids
Diacetyl produced by bacteria growing in bottles exposed to the sun
Hydrogen sulphide formed by yeast autolysis under bright light
Answer and working
B. 3-Methyl-2-butene-1-thiol from photodegraded hop iso-α-acids
Riboflavin photosensitises cleavage of iso-α-acids; the side chain combines with a sulphur source to give the thiol. Brown glass blocks the active wavelengths.
Further reading: Reineccius, Flavor Chemistry and Technology
2 · Flavour chemistry: terpenes, esters, aldehydes, ketones and sulphur compounds · medium
What does gas chromatography-olfactometry add to GC-MS analysis of aroma?
A trained assessor sniffs the effluent to find which peaks actually smell
It converts non-volatile tastants into volatile derivatives
It measures the molecular mass of each volatile compound exactly
It removes the need for any column, separating compounds by smell alone
Answer and working
A. A trained assessor sniffs the effluent to find which peaks actually smell
Many volatiles are odourless at their concentration; sniffing the effluent pinpoints the odour-active ones.
Further reading: Reineccius, Flavor Chemistry and Technology
3 · Flavour generation during processing, fermentation and maturation · medium
In Strecker degradation, an amino acid reacts with an α-dicarbonyl to give:
An aldehyde with one carbon fewer than the amino acid
An ester formed between the amino acid and ethanol
A glycosylamine identical to the Amadori product
A ketone with two more carbons than the original amino acid
Answer and working
A. An aldehyde with one carbon fewer than the amino acid
The amino acid is deaminated and decarboxylated to a Strecker aldehyde; the dicarbonyl becomes an aminoketone that forms pyrazines.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
4 · Vitamins: stability during processing and storage · hard
Vitamin C in a juice degrades by first-order kinetics with k = 0.02 per day. What is its half-life?
About 50 days
About 14 days
About 0.35 days
About 35 days
Answer and working
D. About 35 days
t½ = ln 2/k = 0.693/0.02 ≈ 34.7 days. 50 days uses 1/k; 14 days uses 0.693 × 20 = 13.9 by misapplying k.
Further reading: Fennema's Food Chemistry
5 · Industrial enzymes in food processing · hard
Which lipases allow structured lipids to be made by interesterification?
Lipoxygenases that oxidise the fatty acids
Lipases that act only at the sn-2 position of phospholipids
Non-specific lipases that randomise all three positions
sn-1,3-specific lipases
Answer and working
D. sn-1,3-specific lipases
1,3-specific lipases exchange fatty acids at the outer positions, keeping the sn-2 acid, as in human-milk-fat substitutes.
Further reading: Handbook of Food Enzymology
6 · Acrylamide and other process contaminants from browning · medium
How does IARC classify acrylamide?
Group 1, carcinogenic to humans with sufficient evidence
Group 2A, probably carcinogenic
Not evaluated by IARC
Group 3, not classifiable at all
Answer and working
B. Group 2A, probably carcinogenic
IARC placed acrylamide in Group 2A in 1994.
Further reading: IARC Monographs Volume 60
7 · Phenolic compounds and natural antioxidants · hard
Why do in vitro antioxidant assays such as DPPH not predict performance in a food?
They measure only vitamin C and ignore phenolics
They require the antioxidant to be a protein
They overestimate all antioxidants by exactly a factor of ten
They test radical chemistry in solution, not the food matrix
Answer and working
D. They test radical chemistry in solution, not the food matrix
Partitioning, interfaces, metals and oxygen in real foods decide efficacy; storage tests or Rancimat induction periods are used.
Further reading: Fennema's Food Chemistry
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