Hydrogenation.

For many edible purposes and for some commercial applications it is desirable to produce solid fats. Many shortenings and margarines contain hydrogenated (hardened) oils as their major ingredients. The development of margarine and shortening products resulted from the invention of a successful method for converting low-melting unsaturated fatty acids and glycerides to higher-melting saturated products. The process consists of the addition of hydrogen in the presence of a catalyst to the double (unsaturated) bonds.

Limited use was made of this hydrogenation technology in Europe; the greatest potential use for the process lay in the United States, where a vast production of cottonseed oil, a by-product of the Southern cotton industry, awaited developments that would permit its conversion to a plastic fat. The hardening of cottonseed oil in the early 1900s gave birth to the shortening industry. Practical hydrogenation then spread to all countries where margarines and shortenings are produced from liquid oils.

In commercial practice, hydrogenation is usually carried out with vigorous agitation or hydrogen

dispersion with a narrow range of catalyst in a steel pressure-reaction vessel. The ordinary ranges of temperature and pressure are from 1000 to 2000 C and from atmospheric pressure to 42 kilograms per

square centimetre, respectively. After hydrogenation, the hot oil is filtered to remove the metallic catalyst for either reuse or recovery.

Exercise 2. Translate the following word-combinations.

Tank refining, a steel pressure-reaction vessel, a conversion to a plastic fat, the hardening of cottonseed

oil, a light re-refining with chemicals, free fatty acids, water washing, a successful method for converting

fatty acids to other products, vigorous agitation, a dry filter-aid material, clarification by settling.

Exercise 3. Answer the questions.

1. Why is it necessary to refine oils?

2. What types of refining are practised?

3. What refining method is the most effective?

4. What refining method is used in Ukrainian refineries? 5. What operations are carried out after refining?

6. What is the purpose of hydrogenation? 7. What equipment is necessary for it?

Exercise 4. Complete each sentence with a word or phrase from the box.

continuous refining system re-refining steel pressure-reaction vessel

further processing shortenings

1. Many ___ and margarines contain hardened oils as their major ingredients. 2. In the ___ the emulsion is separated with centrifuges.

3. A light ___ with caustic soda is necessary to improve oil colour.

4. In commercial practice hydrogenation is usually carried out in a ___. 5. Most cold-pressed oils can be used in food products without ___.

Exercise 5. Checking facts and ideas. Decide if these statements are true or false.

1. All cold-pressed oils cannot be used in food products without further processing.

2. The centrifuge is the main machine both in batch refining and in a continuous refining system.

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3. The term degumming is called so because during refining some gums are added into the oil emulsion and they are removed after the emulsion heating.

4. After refining the fat is usually washed with water to remove any impurities. 5. The oil drying may be done in a vacuum only.

Exercise 6. Match the terms on the left with the statements on the right.

Degumming

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