GATE — Life Sciences (XL), Section U Food Technology · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papers
10worked here, free
25written to this exam in this subject
14syllabus 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 25 questions fall
How our questions for GATE spread across the units of Food Chemistry II: Pigments, Flavours, Vitamins, Minerals, Enzymes & Browning. Difficulty: 11 easy, 14 medium, 0 hard.
Pigments: chlorophylls, carotenoids, anthocyanins, betalains, tannins and myoglobin
3
Flavour chemistry: terpenes, esters, aldehydes, ketones and sulphur compounds
3
Food enzymes: specificity, kinetics, inhibition and coenzymes
3
Flavour generation during processing, fermentation and maturation
2
Vitamins: stability during processing and storage
2
Endogenous enzymes in raw materials: lipoxygenase, polyphenol oxidase, peroxidase and pectinases
2
Industrial enzymes in food processing
2
Maillard reaction and caramelisation
2
Colour changes during processing and storage
1
Taste: sweet, sour, salty, bitter and umami compounds
1
Minerals in foods and their chemistry
1
Enzymatic browning and its control
1
Acrylamide and other process contaminants from browning
1
Phenolic compounds and natural antioxidants
1
10 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.
The maximum rate when the enzyme is fully saturated with its substrate
The concentration of enzyme needed to convert all substrate
The temperature at which the enzyme is half inactivated
The substrate concentration at which the rate is half of Vmax
Answer and working
D. The substrate concentration at which the rate is half of Vmax
Km is [S] at v = Vmax/2; a low Km means high affinity.
Further reading: Handbook of Food Enzymology
6 · Food enzymes: specificity, kinetics, inhibition and coenzymes · medium
An enzyme has Vmax = 100 units and Km = 2 mM. What is the rate at 6 mM substrate?
300 units
33 units
75 units
50 units
Answer and working
C. 75 units
v = 100 × 6/(2 + 6) = 75. 50 units is the rate at [S] = Km.
Further reading: Handbook of Food Enzymology
7 · Food enzymes: specificity, kinetics, inhibition and coenzymes · medium
How does a competitive inhibitor change the kinetic constants?
Lowers both Km and Vmax by the same factor
Leaves both Km and Vmax unchanged but slows binding
Lowers Vmax while Km stays exactly the same as before
Raises apparent Km; Vmax unchanged
Answer and working
D. Raises apparent Km; Vmax unchanged
Competitive inhibition is overcome by high [S], so Vmax is unchanged; Km(app) = Km(1 + [I]/Ki).
Further reading: Handbook of Food Enzymology
8 · Endogenous enzymes in raw materials: lipoxygenase, polyphenol oxidase, peroxidase and pectinases · medium
Which enzyme causes the beany flavour of soy milk?
Pectin methylesterase
Polyphenol oxidase
Lipoxygenase
Alliinase
Answer and working
C. Lipoxygenase
Lipoxygenase oxidises linoleic and linolenic acids; hydroperoxide breakdown gives beany volatiles. Grinding in hot water prevents it.
Further reading: Handbook of Food Enzymology
9 · Industrial enzymes in food processing · medium
Which enzyme converts glucose to fructose in high-fructose syrup manufacture?
Fungal glucoamylase
Immobilised glucose isomerase
Thermostable α-amylase
Bacterial pullulanase
Answer and working
B. Immobilised glucose isomerase
α-Amylase liquefies, glucoamylase saccharifies, pullulanase debranches, and isomerase converts glucose to fructose.
Further reading: Handbook of Food Enzymology
10 · Maillard reaction and caramelisation · easy
The Maillard reaction occurs between:
Reducing sugars and amino groups
Fatty acids and oxygen
Sucrose and water only
Phenols and oxygen with PPO
Answer and working
A. Reducing sugars and amino groups
Carbonyl groups of reducing sugars react with amino groups of amino acids and proteins.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
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