GATE — Engineering Sciences (XE), Section G Food Technology · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papersProcessed products from fruits and vegetables: juices and concentrates, jams, jellies and marmalades, pickles, sauces and ketchup, dried and frozen products, canned products and minimally processed produce, with pectin chemistry and by-product recovery. Packhouse and storage engineering are in Agricultural Engineering's post-harvest-horticultural-crops.
In the exams: GATE XE-G Section 3 (fruits and vegetables processing; pectin from fruit wastes); ICAR AIEEA-PG Code 18 Unit III; ICAR AICE 35.a Unit 2
GATE — Engineering Sciences (XE), Section G Food Technology
Section 3 names fruits and vegetables processing (juice, jam, jelly, marmalade, squash, candies, tomato products, potato chips, pickles) and pectin from fruit waste. Expect short reasoning items on pectin gelation (HM versus LM, pH and sugar), hot versus cold break, cloud loss and PME, blanching indicators, and numerical-answer mass balances: juice concentration, tomato paste yield, dried-fruit yield, RTS or squash formulation and syrup strength for a target cut-out Brix.
GATE — Life Sciences (XL), Section U Food Technology
Same Section 3 content as XE-G. Science graduates meet the same product and pectin questions, often framed through chemistry (galacturonic acid, degree of esterification, egg-box model, chlorophyll to pheophytin, anthocyanin colour) and microbiology (lactic fermentation of sauerkraut and pickles, spoilage of juices).
How our questions for GATE spread across the units of Fruit & Vegetable Processing Technology. Difficulty: 30 easy, 57 medium, 12 hard.
| Preparation for processing: washing, peeling, cutting and blanching | 8 | |
| Fruit juices: extraction, clarification, concentration and packaging | 8 | |
| Pectin chemistry and gel formation | 8 | |
| Canning of fruits and vegetables | 8 | |
| By-product utilisation: pectin, peel and pomace | 8 | |
| Composition and processing quality of fruits and vegetables | 7 | |
| Squashes, cordials, nectars and ready-to-serve beverages | 7 | |
| Jams, jellies, marmalades and fruit preserves | 7 | |
| Pickles, chutneys and sauces | 7 | |
| Tomato products: juice, puree, paste and ketchup | 7 | |
| Dehydrated and frozen fruits and vegetables | 7 | |
| Minimally processed fresh-cut produce | 6 | |
| Potato products | 6 | |
| Candied fruits | 5 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Lye peeling of peaches removes the skin by
A. Hot alkali dissolving the pectin under the skin
Hot sodium hydroxide attacks the pectic material under the skin so the skin washes off; the fruit is then rinsed and often dipped in weak acid. Abrasion, steam-flash and flame peeling are separate methods used for other crops.
Further reading: Fellows, Food Processing Technology
100 kg of RTS beverage must contain 10% juice, 10% TSS and 0.3% acidity as citric acid. The juice used has 10 °Brix and 1.0% acidity. Ignoring the soluble solids contributed by added acid, how much sugar must be added?
C. 9.0 kg
The 10 kg of juice brings 10 × 0.10 = 1.0 kg of soluble solids. The beverage needs 100 × 0.10 = 10 kg, so sugar = 10 − 1 = 9.0 kg. 10 kg ignores the juice's own solids; 1.0 kg is the solids from juice; 8.0 kg double-counts them.
Further reading: Girdhari Lal, Siddappa and Tandon, Preservation of Fruits and Vegetables
High-methoxyl pectin is defined as pectin with a degree of esterification
B. Above 50%
HM pectin has DE above 50% and LM pectin below 50%. Pectic acid has essentially no ester groups. Commercial HM pectins span a range of DE above 50%, not only above 90%.
Further reading: May, Industrial pectins, Carbohydrate Polymers
Sucrose crystals form in a stored jam. The most likely processing fault is
B. Too little inversion
Insufficient inversion, for example from low acid or very short boiling, leaves too much sucrose, which crystallises. Long boiling and high acid increase inversion, and excess pectin affects firmness, not crystallisation.
Further reading: Girdhari Lal, Siddappa and Tandon, Preservation of Fruits and Vegetables
Canned sweet corn shows black staining on the inside of the can. The lacquer that prevents this contains
D. Zinc oxide
Sulphur released from proteins forms black iron or tin sulphide; sulphur-resistant C-enamel contains zinc oxide, which forms white zinc sulphide instead. The other substances are not lacquer components.
Further reading: Fellows, Food Processing Technology
Canned pears with a pH close to 4.6 are processed in boiling water after citric acid is added to the syrup. This practice is called
A. Acidification
Adding acid to bring a borderline fruit clearly below pH 4.6 is acidification; it makes a boiling-water process adequate. Exhausting removes air, syneresis is gel weeping, and inversion is hydrolysis of sucrose.
Further reading: Fellows, Food Processing Technology
Grapes for raisins are dipped in an alkaline emulsion of oils before drying to
B. Crack the waxy bloom and speed drying
The dip disrupts the waxy cuticle so water escapes faster. Golden colour comes from sulphuring, the dip is not a coating for stickiness, and it does not reliably inactivate enzymes.
Further reading: Fellows, Food Processing Technology
Potatoes for chips (crisps) should have
A. High dry matter and low reducing sugars
High dry matter gives yield and crisp texture with less oil uptake; low reducing sugars limit Maillard darkening and acrylamide. High sugars give dark, bitter chips, and high water gives soggy, oily chips.
Further reading: Talburt and Smith, Potato Processing
Potatoes stored at 4 °C give dark chips. The reason is
B. Cold-induced sweetening raises reducing sugars
Below about 8–10 °C, starch breakdown to sugars outpaces their use, so glucose and fructose accumulate and brown during frying. Starch granules remain, asparagine levels are not the main change, and dry matter is not lowered by water uptake.
Further reading: Talburt and Smith, Potato Processing
Mango processing waste is valued because mango kernels yield
C. A fat used in confectionery fat blends
Mango kernel fat has a fatty acid profile suited to confectionery fat blends. Proteases come from pineapple or papaya, d-limonene from citrus peel, and pectin from mango peel still needs sugar and acid if it is HM pectin.
Further reading: May, Industrial pectins, Carbohydrate Polymers
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