FSSAI Food Analyst Examination (and Junior Analyst Examination) · India · Food Safety and Standards Authority of India
Original practice questions written to the published syllabus · not past papersThe chemistry a food scientist uses every day: bonding, acids and bases, buffers, organic functional groups and reaction mechanisms, chemical kinetics and thermodynamics, and the physical chemistry of solutions, surfaces and colloids. Students who take GATE XL (Life Sciences) sit a compulsory chemistry section alongside the Food Technology section.
In the exams: GATE XL-P (compulsory chemistry section for XL candidates who choose XL-U Food Technology); background for ICAR AIEEA-PG Code 18 Unit I
How our questions for FSSAI Food Analyst Examination spread across the units of Chemistry for Food Science (General, Organic & Physical). Difficulty: 7 easy, 10 medium, 1 hard.
| Stoichiometry, concentration units and solution preparation | 7 | |
| Electrochemistry and redox potential | 3 | |
| Stereochemistry and optical activity | 2 | |
| Coordination chemistry and metal ions in foods | 2 | |
| Atomic structure, periodicity and chemical bonding | 1 | |
| Acids, bases, pH, buffers and the Henderson-Hasselbalch equation | 1 | |
| Chemical equilibrium and solubility | 1 | |
| Colligative properties: freezing-point depression, boiling-point elevation and osmotic pressure | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
How does isotope-ratio mass spectrometry detect cane sugar added to a fruit juice?
A. C4 plants such as cane fix carbon with a different ¹³C/¹²C ratio from the C3 fruit
Plants using the C4 pathway (cane, maize) discriminate less against ¹³C than C3 plants (most fruit), so their sugars have a measurably higher ¹³C/¹²C ratio. Both contain ¹⁴C from the atmosphere; sucrose is the same molecule whatever its source; deuterium ratios are used too, but they shift, not vanish.
Further reading: Atkins' Physical Chemistry; Fennema's Food Chemistry
A 10.0 g sample of juice needs 12.0 mL of 0.1 N NaOH to reach the phenolphthalein end point. What is its titratable acidity as anhydrous citric acid (meq. factor 0.064)?
D. 0.768%
Acidity = V × N × meq × 100/mass = 12.0 × 0.1 × 0.064 × 100/10 = 0.768%. 1.080% uses the lactic acid factor (0.090); 7.680% forgets to divide by the 10 g sample mass; 0.077% slips the decimal point by a factor of ten.
Further reading: Nielsen, Food Analysis; Housecroft and Sharpe, Inorganic Chemistry
What is the normality of a 0.5 M sulphuric acid solution when used as an acid in neutralisation?
C. 1.0 N
H₂SO₄ supplies two protons per molecule, so 1 mol = 2 equivalents and 0.5 M = 1.0 N. 0.5 N treats it as monoprotic; 0.25 N divides by 2 instead of multiplying; 2.0 N doubles twice.
Further reading: Nielsen, Food Analysis; Housecroft and Sharpe, Inorganic Chemistry
Why is sodium hydroxide not used as a primary standard?
D. It absorbs water and carbon dioxide from the air
Solid NaOH is hygroscopic and reacts with atmospheric CO₂ to form carbonate, so its weighed mass does not give its true amount; its solutions are standardised against potassium hydrogen phthalate. It is cheap, reacts instantly with acids, and has a low molar mass (40 g/mol), which is itself a disadvantage, not an advantage.
Further reading: Nielsen, Food Analysis; Housecroft and Sharpe, Inorganic Chemistry
In the Mohr titration for salt, what signals the end point?
A. A red-brown silver chromate precipitate after all chloride has precipitated
Silver chloride (less soluble) precipitates first; once chloride is used up, the first excess of Ag⁺ forms red-brown Ag₂CrO₄ with the chromate indicator. The white AgCl precipitate forms throughout, so it does not mark the end point; starch-iodine and phenolphthalein belong to other titrations.
Further reading: Atkins' Physical Chemistry; Fennema's Food Chemistry
A sucrose solution of 0.05 g/mL in a 2 dm polarimeter tube gives an observed rotation of +6.65°. What is the specific rotation?
B. +66.5°
[α] = α/(l·c) = 6.65/(2 × 0.05) = +66.5°. +133° divides only by the concentration and forgets the 2 dm tube length; +3.3° divides only by the length; +6.65° reports the observed rotation as if it were the specific rotation.
Further reading: Clayden, Greeves and Warren, Organic Chemistry; Fennema's Food Chemistry
How does chiral gas chromatography help detect undeclared synthetic flavour in a product labelled as natural?
C. Biosynthesis tends to give one enantiomer, synthesis a racemate
Biosynthesis by enzymes typically gives an excess of one enantiomer; chemical synthesis without a chiral catalyst gives a racemate. A chiral stationary phase separates the enantiomers so their ratio can be compared with authentic references. Racemates show no net rotation; natural flavours are often chiral; chiral columns separate by stereochemistry.
Further reading: Clayden, Greeves and Warren, Organic Chemistry; Fennema's Food Chemistry
Which titrant is used in the iodometric determination of the peroxide value of fats?
D. Sodium thiosulphate
Hydroperoxides oxidise iodide to iodine, which is titrated with standard sodium thiosulphate using starch indicator. Silver nitrate is for chloride, EDTA for metal ions, KOH for acid and saponification values.
Further reading: Nielsen, Food Analysis; Housecroft and Sharpe, Inorganic Chemistry
How many donor atoms does EDTA use when binding a metal ion in a typical 1 : 1 complex?
A. 6
EDTA is hexadentate: two amine nitrogens and four carboxylate oxygens. It forms 1 : 1 complexes with most divalent and trivalent ions, the basis of complexometric titrations.
Further reading: Nielsen, Food Analysis; Housecroft and Sharpe, Inorganic Chemistry
Which indicator is used in the EDTA titration of water hardness?
A. Eriochrome Black T
Eriochrome Black T forms a wine-red complex with Ca²⁺ and Mg²⁺ and turns blue when EDTA has bound all the metal, at pH about 10. Phenolphthalein is an acid-base indicator, starch detects iodine, and chromate is the Mohr indicator.
Further reading: Nielsen, Food Analysis; Housecroft and Sharpe, Inorganic Chemistry
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