Oil Extraction and Processing Questions and Answers

Answer: A

Correct answer: Winterisation

Cloudiness on chilling is the signature of waxes and high-melting glycerides crystallising out. Winterisation is the step that prevents it: the oil is cooled slowly, the crystals are allowed to grow, and they are filtered off, so the oil stays clear at refrigerator temperature.

Sunflower oil is particularly prone to it because the seed coat carries appreciable wax. The other steps address quite different impurities - phospholipids, free fatty acids and colour respectively - and none of them removes anything that crystallises.

Answer: B

Correct answer: Direct for the soybean, pre-press for the groundnut

The oil content decides the route. Soybean at 20 per cent goes directly to solvent extraction: the flakes hold their structure, the bed drains, and residual oil below one per cent is reached in a single stage.

Groundnut at 45 per cent would flood the extractor, releasing so much oil that the bed will not percolate. It is therefore pressed first to about 15 to 20 per cent and the cake then solvent extracted. Pressing alone would leave 5 to 8 per cent oil behind in both, and pre-pressing the soybean would add a stage for no gain.

Answer: C

Correct answer: The temperature needed will damage the oil

Deodorisation strips compounds that are only sparingly volatile. Without the vacuum their boiling points are far higher, so the oil would have to be taken well above the 240 to 260 degrees Celsius it can tolerate.

At those temperatures the triglycerides decompose, the oil darkens badly and trans isomers are formed - the oil is damaged rather than refined, and the volatiles are removed less completely, not more. The vacuum is not an economy measure; it is the condition that makes stripping possible at a survivable temperature.

Answer: D

Correct answer: miscella

Miscella is the solution of oil in solvent leaving the extractor, typically 25 to 30 per cent oil in hexane. It goes to a distillation train where the solvent is evaporated and condensed for reuse, leaving crude oil.

The other three belong elsewhere in the process: soapstock is the soap-rich stream from alkali neutralisation, gums are the phospholipids removed in degumming, and foots is the sediment settling from crude oil on standing. Only miscella contains solvent, which is enough to identify it.

Answer: A

Correct answer: degumming

Degumming is the hydration step. Water is mixed into the warm crude oil so that the hydratable phosphatides swell, become insoluble in the oil, and separate as a distinct phase that a centrifuge can throw out.

It comes first in the refinery because the gums would otherwise foul later stages and darken the oil during deodorisation, and because the recovered stream is saleable as lecithin. Bleaching removes colour with adsorbent earth, winterisation removes waxes by chilling, and deodorisation strips volatiles under vacuum - three later steps with three different mechanisms.

Answer: B

Correct answer: winterisation

Winterisation cools the oil slowly so that waxes and high-melting glycerides crystallise, allows the crystals time to grow to a filterable size, and removes them by filtration.

The name comes from the original test of leaving oil out in winter to see whether it clouded. Sunflower and rice bran oils need it most, their seed coats carrying appreciable wax. The other three steps act on quite different impurities - free fatty acids, colour and phospholipids - and none of them removes anything that crystallises on chilling.

Answer: C

Correct answer: cake

Cake is the pressed solid leaving an expeller or ghani, still holding 5 to 8 per cent oil because compression cannot squeeze a cellular material dry.

That residual is exactly why the cake is so often solvent extracted afterwards, the resulting meal going to animal feed for its protein. The other terms belong elsewhere: soapstock comes from neutralisation, miscella is the oil-and-solvent solution from an extractor, and meal fines are the small particles carried out of an extraction bed.

Answer: D

Correct answer: soapstock

Soapstock is the heavy phase separated after alkali neutralisation. It contains the soaps formed from the free fatty acids together with entrained neutral oil, some phosphatides and water.

The entrained oil is what makes it a loss rather than merely a by-product, and it is why total refining loss always exceeds the acidity removed. Soapstock is usually acidulated to recover the fatty acids for soap or feed. Producing none of it at all is the standing argument for physical refining, which strips the acids by distillation instead.

Answer: A

Correct answer: Pre-press then solvent, as 42 per cent floods an extractor

The recovery column settles the first half: pre-press then solvent gives 98.5 per cent, above direct solvent at 97 and far above the two pressing routes.

The second half is the reason direct solvent is not chosen here despite its own good figure. A material carrying 42 per cent oil releases so much liquid that the bed floods and the miscella will not percolate, so the 97 per cent in the table could not actually be achieved on this seed. Pressing first brings the oil down to 15 to 20 per cent, leaving a cake the extractor can handle.

Answer: B

Correct answer: Bran must be stabilised within hours

Read the rate rather than the levels. Acidity rises from 1.5 to 4.0 per cent in the first day alone, and by day three at 8.5 per cent the bran is already poor for edible use.

Since the damage is largely done inside twenty-four hours, any useful intervention must come within hours of milling - either immediate extraction, or heat stabilisation to denature the lipase that milling has released. A week's storage is plainly not acceptable, the bran does not improve, and the table shows storage time to be the controlling variable.