Oil Extraction and Processing Questions and Answers

Answer: A

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason explains the suitability. Alkali refining loses neutral oil in two ways - saponification by excess alkali and entrainment in the soapstock - and both scale with the quantity of soap formed, so a high-acid oil loses a great deal.

Physical refining strips the acids by steam distillation instead, forming no soap and therefore entraining no oil, and the distillate is itself saleable. The gain grows with acidity, which is why the route is chosen for palm and rice bran oils in particular. It does demand thorough degumming first.

Answer: B

Correct answer: 1 and 2 only

The first two are correct. Flaking ruptures the oil-bearing cells and shortens the diffusion path; cooking thins the oil, coagulates protein and sets the moisture for pressing.

The third reverses dehulling's effect. Hulls carry almost no oil, so removing them raises the oil content of what goes forward - the feed is richer and the plant handles more oil for the same throughput. It also reduces the oil absorbed by hulls during processing, so both yield and capacity improve.

Answer: C

Correct answer: 1 and 2 only

The first two are right. Degumming removes phospholipids by hydrating them and centrifuging them out; bleaching removes colour pigments together with residual soaps and traces of metal, adsorbed onto activated earth and filtered off.

The third names the wrong step. Deodorisation strips volatile odour and flavour compounds by steam distillation under vacuum. Waxes are removed by winterisation, a chilling and filtration step, which works by crystallisation rather than volatility - a quite different mechanism for a quite different impurity.

Answer: D

Correct answer: 1 and 2 only

The first two are correct. Hexane is the usual commercial solvent, chosen for its selectivity for oil, low boiling point and ease of recovery; and countercurrent contact keeps a concentration difference at every stage, fresh solvent meeting the most nearly exhausted flakes.

The third misnames a stream. Miscella is the oil and solvent solution leaving the extractor and going to distillation. The spent meal is the solid, which goes to a desolventiser-toaster to have its residual hexane driven off before becoming animal feed.

Answer: A

Correct answer: 1 and 2 only

The first two are correct. Free fatty acid content records hydrolysis of the triglycerides, and iodine value measures unsaturation by the mass of iodine adding across the double bonds.

The third is wrong on the chemistry. Hydroperoxides are unstable and decompose into aldehydes and ketones, so peroxide value rises, peaks and then falls as oxidation proceeds. A low reading is therefore ambiguous, and anisidine value is measured alongside it to distinguish a fresh oil from a thoroughly deteriorated one.

Answer: B

Correct answer: A-2, B-1, C-4, D-3

Each step removes a different class of impurity, and each works by a different mechanism. Degumming hydrates the phospholipids so they separate as a distinct phase. Neutralisation reacts free fatty acids with alkali, throwing them out as soapstock.

Bleaching adsorbs colour pigments, residual soaps and trace metals onto activated earth. Winterisation crystallises waxes and high-melting glycerides by chilling and filters them off. Reading the mechanism - hydration, reaction, adsorption, crystallisation - is a surer route through this pairing than trying to recall the list.

Answer: C

Correct answer: A-2, B-1, C-4, D-3

Each stream identifies its own process. Miscella is oil dissolved in solvent, so it can only come from solvent extraction. Soapstock contains soaps, so it can only come from alkali neutralisation.

Spent earth is used adsorbent, so it comes from bleaching. Cake is the pressed solid, so it comes from mechanical pressing. The composition of each stream names its origin without any need for memorisation - a useful check whenever a question lists refinery by-products.

Answer: D

Correct answer: A-2, B-1, C-4, D-3

The four indices measure four unrelated things. Free fatty acid records hydrolytic deterioration; peroxide value records primary oxidation, the hydroperoxide stage.

Iodine value measures unsaturation, being the mass of iodine adding across the double bonds. Saponification value measures the mean molecular mass of the fatty acids: it is the alkali needed per gram of oil, so short-chain oils such as coconut give high figures around 255 and long-chain ones around 190. Two of the four report deterioration and two report composition, which is the quickest way to halve the problem.

Answer: A

Correct answer: A-2, B-1, C-4, D-3

The figures rank by how the oil is removed. A ghani presses batchwise at low speed and leaves about 12 per cent - the least efficient. A screw press develops far higher pressure continuously and leaves about 7 per cent.

Both are limited by compression itself, which cannot empty a cellular material. The two solvent routes dissolve the oil instead and reach well under 2 per cent: about 1.5 per cent for direct extraction, and about 0.8 per cent after pre-pressing, the pressed cake extracting more completely than whole flakes of a high-oil seed.

Answer: B

Correct answer: Deodorisation

Deodorisation is a refining step, and the last of them: it strips volatile flavour and odour compounds from the extracted oil by steam distillation under high vacuum.

The other three act on the seed before any oil has been obtained. Cooking thins the oil and sets the moisture, dehulling removes the hull, and flaking ruptures the cells. The division is worth holding onto - preparation makes the oil accessible, refining makes the recovered oil fit for use, and no step belongs to both.