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 papersThe four constituents that make up most of any food and how they behave during processing and storage: water and its mobility, sugars and starch, proteins and their functional properties, and lipids and their oxidation.
In the exams: GATE XE-G and XL-U Section 1 (carbohydrates, proteins, lipids); ICAR AIEEA-PG Code 18 Unit I; ICAR AICE 35.b Unit 5 (emulsions, foams, gels, functional properties)
ICAR AIEEA-PG / PGS — Code 18 Food Science Technology
Unit I names general chemistry of food constituents, physical properties, colloidal systems, gels and emulsions, physicochemical changes during processing and storage, and metabolism of the macronutrients. MCQs test definitions and classification: Osborne fractions, reducing and non-reducing sugars, HM and LM pectin, aw limits for microbes, antioxidant classes and the meaning of PV, IV, SV and AV.
How our questions for ICAR AIEEA-PG / PGS spread across the units of Food Chemistry I: Water, Carbohydrates, Proteins & Lipids. Difficulty: 28 easy, 48 medium, 5 hard.
| Food proteins: classification and sources | 9 | |
| Monosaccharides, disaccharides and oligosaccharides | 8 | |
| Water in foods: structure, bound and free water, sorption isotherms and water activity | 7 | |
| Cellulose, pectic substances, gums and dietary fibre | 7 | |
| Post-mortem changes and tenderisation of muscle proteins | 7 | |
| Lipids: classification, structure and nomenclature | 7 | |
| Amino acids, peptides and protein structure | 6 | |
| Lipid oxidation: autoxidation, photo-oxidation, rancidity and antioxidants | 6 | |
| Hydrolytic rancidity and thermal polymerisation of frying oils | 6 | |
| Starch: structure, gelatinisation, pasting and retrogradation | 5 | |
| Protein denaturation and functional properties: solubility, gelation, emulsification and foaming | 4 | |
| Physical properties of fats: crystallisation and polymorphism | 4 | |
| Chemical and physical changes in macronutrients during processing | 4 | |
| Glass transition and molecular mobility | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which group of microorganisms can grow at the lowest water activity?
B. xerophilic moulds and osmophilic yeasts, down to about aw 0.61
Xerophilic moulds and osmophilic yeasts are the most tolerant, growing to about 0.61. Most spoilage bacteria need above about 0.90; Salmonella needs about 0.93 or more; lactic acid bacteria are not the low-aw limit.
Further reading: Damodaran and Parkin, Fennema's Food Chemistry
Waxy maize starch contains
C. almost no amylose, being nearly all amylopectin
Waxy starches are mutants with almost no amylose. Normal maize is about 25 % amylose; high-amylose types reach 50–70 %.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
Loss of birefringence (the Maltese cross) when starch granules are heated in water indicates
C. gelatinisation
Gelatinisation melts crystalline order, so birefringence disappears. Retrogradation is re-association on cooling; dextrinisation is dry-heat breakdown; syneresis is weeping of liquid from a gel.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
Pectin with a degree of esterification of 35 % is classified as
D. low-methoxyl pectin
The dividing line is 50 % esterification; 35 % is low-methoxyl. Protopectin is the insoluble parent form in unripe fruit.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
Which of these amino acids is essential for adult humans?
A. Lysine
Lysine is one of the nine essential amino acids (His, Ile, Leu, Lys, Met, Phe, Thr, Trp, Val). Alanine, glutamic acid and serine can be synthesised.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
The covalent cross-link between two cysteine residues that is important in gluten and in egg-white gels is a
C. disulphide bond
Oxidation of two cysteine thiol groups forms an S–S disulphide bond. Peptide bonds join the backbone; hydrogen bonds are non-covalent; glycosidic bonds join sugars.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
In the Osborne classification, proteins soluble in about 70 % aqueous ethanol are called
A. prolamins
Prolamins (gliadin, zein, hordein) dissolve in aqueous alcohol. Albumins dissolve in water, globulins in dilute salt, glutelins in dilute acid or alkali.
Further reading: Belitz, Grosch and Schieberle, Food Chemistry
In autoxidation of lipids, the propagation step is
D. ROO• + RH → ROOH + R•
Propagation transfers the radical: a peroxyl radical takes hydrogen from another lipid, forming a hydroperoxide and a new alkyl radical. The first equation is initiation, the third termination, the fourth hydroperoxide decomposition.
Further reading: Frankel, Lipid Oxidation
The free fatty acid content of an oil, expressed as % oleic acid, is approximately equal to
A. acid value divided by 1.99
FFA (% oleic) ≈ AV/1.99, from 56.1 (KOH) and 282 (oleic acid): 282/(56.1 × 10) ≈ 0.503 = 1/1.99. Saponification and iodine values measure other things.
Further reading: deMan and others, Principles of Food Chemistry
Acrylamide forms in fried and baked foods mainly from
B. asparagine and reducing sugars at high temperature and low moisture
Acrylamide is a Maillard-related product of free asparagine with reducing sugars above about 120 °C in dry conditions. Boiling, freezing and refrigeration do not form it.
Further reading: Damodaran and Parkin, Fennema's Food Chemistry
Ten here, 81 in the app. The Laisha app has every practice question we have written to ICAR AIEEA-PG / PGS 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.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
An AI operating system for agriculture: free guides, manuals and tools written for every country.