Oil Extraction and Processing Questions and Answers

Answer: A

Correct answer: Both Statement I and Statement II are correct

Both are true and the second explains the first. Physical refining removes free fatty acids by steam distillation under vacuum, in effect combining the acid removal with deodorisation, so no alkali is used and no soap is formed.

Alkali refining instead reacts the acid with caustic soda to form soaps, which are centrifuged off as soapstock - a low-value stream requiring its own handling, and one that carries neutral oil away with it. Physical refining therefore gives a better yield, but it demands a well-degummed feed, since phosphatides survive the distillation and would darken the oil.

Answer: B

Correct answer: Statement I is incorrect but Statement II is correct

The second statement is sound as far as it goes: a thinner flake does shorten the diffusion path. But "always" makes the first statement false.

Below about 0.25 to 0.3 mm the flake loses its mechanical integrity, breaking into fines that blind the percolation bed and stop the miscella draining through it. Extraction then gets worse, not better, and the miscella carries solids that must be removed downstream. Flake thickness is an optimum rather than a minimum - a good illustration of a variable that helps up to a point and then reverses.

Answer: C

Correct answer: 2, 1, 4, 3

Cleaning and dehulling come first: foreign matter must be out before the seed reaches rolls, and hulls before the feed is enriched. Flaking follows, rupturing the cells and reducing the material to thin flakes.

Cooking or conditioning comes next, coagulating protein, thinning the oil and setting the moisture, so that the flakes arrive at the press or extractor in the condition each requires. Extraction itself is last. Note that cooking follows flaking rather than preceding it - conditioning a thin flake is quick and uniform, whereas heating whole seed would be neither.

Answer: D

Gums must go first because they interfere with every later step, then the free acids, then the colour, and deodorisation finishes the oil. Winterisation, where it is needed at all, follows deodorisation as the final step.

Answer: A

Correct answer: 2, 1, 3, 4

The order describes countercurrent contact. Flakes enter at one end; fresh solvent enters at the other, so the cleanest solvent meets the most nearly exhausted flakes.

That is what drives the residual oil below one per cent: the last traces face a solvent with almost no oil in it, and the concentration difference remains large to the very end. The miscella, richest in oil, leaves at the fresh-flake end. Solvent is then recovered from it by distillation and returned. Feeding fresh solvent to fresh flakes instead would waste the driving force where it is least needed.

Answer: B

Correct answer: 1, 2, 3, 4

The chain is strictly causal. Damp storage supplies the water that hydrolysis needs, and the seed's own lipase splits triglycerides into free fatty acids and glycerol.

Higher acidity means the neutralisation stage must remove more acid, so more alkali is dosed. Refining loss rises accordingly, and neutral oil loss rises with it - excess alkali saponifies some of the oil itself and more is entrained in the soapstock. Each step follows from the one before, and the whole cost is incurred in the refinery for a fault committed in the store.

Answer: C

Correct answer: 1, 2, 3, 4

The order follows the chemistry of deterioration. Hydrolysis comes first, and often before processing: water and lipase split triglycerides, raising free fatty acids.

Oxidation then begins with hydroperoxides, measured by peroxide value - the primary stage. Those decompose into aldehydes and ketones, measured by anisidine value - the secondary stage. It is those secondary products that carry the rancid odours and flavours, so sensory rejection comes last. The sequence explains why peroxide value alone is not enough: it can fall as the oil worsens, once decomposition outpaces formation.

Answer: D

Correct answer: Only three

The first three are right. Degumming removes phospholipids, neutralisation removes free fatty acids, and bleaching removes colour pigments together with traces of metals and residual soaps.

The fourth is wrong. Deodorisation removes volatile odour and flavour compounds by steam distillation under vacuum; waxes and high-melting glycerides are removed by winterisation, a chilling and filtration step. The two are easily confused because both come late in the refinery, but one works by volatility and the other by crystallisation.

Answer: A

Correct answer: Only three

The first three are correct. Dehulling raises the oil content of the feed by removing near-oil-free material; flaking ruptures the cells and shortens the diffusion path; and cooking thins the oil, coagulates protein and sets the moisture.

The fourth is wrong. Cleaning removes stones, straw, dust and metal - foreign matter that would damage the rolls or contaminate the meal. Free fatty acids are removed much later, in neutralisation, and no preparation step touches them; cooking in fact prevents their formation by denaturing lipase.

Answer: B

Correct answer: Only three

Three of the pairs hold. Free fatty acid content measures hydrolytic deterioration, peroxide value the primary stage of oxidation, and iodine value the degree of unsaturation.

The fourth is wrong. Saponification value is the mass of potassium hydroxide needed to saponify one gram of oil, and it reflects the average molecular weight of the fatty acids - high for short-chain oils such as coconut, low for long-chain ones. It says nothing about waxes, which are determined separately and removed by winterisation.