Oils Fats and Soaps Questions and Answers

Answer: A

The glycerol backbone carries three ester linkages, and hydrolysing them gives glycerine and the free acids. Everything else in the industry follows from that structure. Hydrolysis and esterification are the two basic reactions.

Answer: B

Both are triglycerides and the distinction is only whether the material is liquid or solid at room temperature. The state follows from the chain length and the degree of unsaturation. Palm oil is solid in Europe and liquid in the tropics.

Answer: C

Both are true and the reason gives the cause: a cis double bond puts a kink in the chain that prevents close packing, which is why unsaturated oils stay liquid to much lower temperatures. Trans isomers pack almost as well as saturated chains.

Answer: D

Pressing alone leaves too much oil in the cake when the seed contains under about twenty-five per cent. High oil seeds are usually pre-pressed and then solvent extracted to recover the remainder. Hexane is recovered and recycled in the plant.

Answer: A

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

The refining sequence removes a different class of impurity at each step, in the order the processing requires. Degumming takes out the phosphatides, which would otherwise settle as a sludge in storage and interfere with the later steps. Neutralisation removes the free fatty acids as a soapstock. Bleaching adsorbs the colour bodies onto activated clay. And deodorisation strips the volatile compounds carrying odour and flavour.

Answer: B

Gums would otherwise interfere with every later step and soap would foul the bleaching earth. Deodorisation comes last because it is the most demanding of the four in energy and vacuum. Reversing any pair of the steps causes trouble downstream.

Answer: C

Volatile aldehydes and ketones are stripped at low pressure and around two hundred and forty degrees. The vacuum is essential because the temperature would otherwise damage the oil itself. Steam acts as the stripping agent throughout.

Answer: D

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

Both are true and the reason gives the necessity. The odour compounds are present at parts per million and are stripped with steam, and at atmospheric pressure the temperature required would oxidise the oil, form trans isomers and darken it. Reducing the pressure to a few millibars lets the same stripping be done around 240 to 260 degrees, which the oil survives.

Answer: A

Correct answer: the degree of unsaturation

Iodine adds across carbon-carbon double bonds, so the mass of iodine taken up by a hundred grams of oil measures how many such bonds it contains. A high value means a highly unsaturated oil - liquid, more readily oxidised and more prone to rancidity - and hydrogenation is measured by the fall in the value as the bonds are saturated.

Answer: B

These four numbers characterise a fat between them and appear on every specification. Each is determined by a titration, and confusing them leads to quite wrong conclusions about a sample. A specification usually quotes all four together.