Oil Extraction and Processing Questions and Answers

Answer: C

Correct answer: 0.3 per cent

Express the absolute pressure as a fraction of atmospheric:

\[ \frac{3}{1013} \times 100 = 0.296\% \approx 0.3\% \]

So the deodoriser works at roughly three-thousandths of atmospheric pressure. That depth of vacuum is what makes the process possible: it lowers the boiling points of the free fatty acids and odour compounds enough that they can be steam-stripped at a temperature the triglycerides themselves survive, typically 240 to 260 degrees Celsius.

Answer: D

Correct answer: 14 kg

The total loss divides into the acid actually removed and the neutral oil lost with it:

\[ 38 - 24 = 14\ \mathrm{kg} \]

That 14 kg is the real cost of alkali refining. Neutral oil is lost by saponification from the excess alkali and by entrainment in the soapstock, so refining loss always exceeds the acidity by a margin - here by more than half again. Reducing it is the standing objective of refinery practice, and avoiding it altogether is the argument for physical refining.

Answer: A

Running continuously it consumes \( 22 \times 24 = 528 \) kWh a day, and \( 528/12 = 44 \) kilowatt hours per tonne. Pressing is energy intensive, which is part of the argument for extracting low-oil seeds directly with solvent.

Answer: B

Correct answer: 83.3 per cent

The phosphatides present are 1.8 per cent of the charge:

\[ 0.018 \times 1000 = 18\ \mathrm{kg} \]

and the recovery is what was collected over what was there:

\[ \frac{15}{18} \times 100 = 83.3\% \]

The shortfall is the non-hydratable phosphatides, chiefly calcium and magnesium salts of phosphatidic acid, which water alone will not swell. Acid degumming with phosphoric or citric acid is used where those must be removed too, since any left behind darken the oil during deodorisation.

Answer: C

Correct answer: Both Statement I and Statement II are correct

Both are true and the second is the reason for the first. A bed of flakes carrying forty per cent oil releases so much liquid that the miscella cannot percolate through it: the bed floods, drainage stops and extraction becomes very slow.

Pressing first takes the oil content down to something like 15 to 20 per cent, leaving a cake that behaves properly in the extractor. That is pre-press solvent extraction, the standard route for groundnut, sunflower, rapeseed and copra. Low-oil seeds such as soybean at 20 per cent go directly to solvent without a press.

Answer: D

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

The second statement gives the real mechanism: rolling ruptures the oil-bearing cells and reduces the thickness to a fraction of a millimetre, so the solvent has only a very short path to diffuse in and the dissolved oil a short path out.

The first statement is false, and physically impossible - flaking is a mechanical operation that changes shape only, and nothing is added or removed, so the oil content of the material is exactly what it was. It is the accessibility of the oil that improves, not the quantity of it.

Answer: A

Correct answer: Both Statement I and Statement II are correct

Both are true and the second explains the first, on two counts. Hulls carry almost no oil, so removing them concentrates the oil in the feed - more oil handled for the same plant throughput, which is the capacity gain.

Hulls are also absorbent and would soak up oil during processing, carrying it out in the cake. Removing them therefore raises the yield as well. The hulls are not wasted: they are usually burned for steam or blended back into low-protein feed, so dehulling costs little beyond the equipment.

Answer: B

The chemistry in the second statement is exactly why the first fails: a badly oxidised oil can show a low peroxide value because the peroxides have already decomposed. Anisidine value or a sensory panel is needed alongside it.

Answer: C

Correct answer: Both Statement I and Statement II are correct

Both are true and the second is the reason for the first. Deodorisation must strip free fatty acids, aldehydes and ketones that are only sparingly volatile, and at atmospheric pressure the temperature needed would decompose the oil, darken it and generate trans isomers.

Working at a few millibars absolute lowers the volatiles' boiling points enough that stripping steam removes them at 240 to 260 degrees Celsius, which the triglycerides survive. The vacuum is not an economy of steam but the condition that makes the process possible at all.

Answer: D

Correct answer: Both Statement I and Statement II are correct

Both are true and the second is the mechanism. Rice bran contains a very active lipase, and milling ruptures the cells so that enzyme and oil are brought together for the first time.

Hydrolysis then proceeds at a rate no other common oilseed approaches - several per cent of free fatty acid a day is usual. Since every point of acidity must be neutralised and neutral oil is lost with it, bran left standing quickly becomes uneconomic to refine for food use. Prompt extraction, or stabilisation of the bran by heat to denature the enzyme, is the answer.