Plant hardening process

Raffinose occurs only at low concentrations in the leaves of plants, but accumulates in the storage organs during the process of development. It has been generally observed that the level of raffinose increases as the tissue loses water this 108-1i3,u6-m js a characteristic feature of maturation of seeds and the hardening process of winter-hardy plants. The hardiness of several plants towards desiccation and elevated temperature may be compared to the property of frost resistance.125-134 When the heat resistance reaches a maximum in the summer, the frost resistance is at its minimum. 

The hardening process is carried out predominantly in batch equipment. Some continuous plants are in use (Hastert, 1981) but they are suitable mainly for long runs of single melting points from vegetable oils for which extended catalyst life is attainable. 

The formation of mineral coal is not an instantaneous process, but is an extremely lengthy one, spread over an extended period. Millions of years ago, when the temperature was moderate and rainfall was heavy, vegetation was quite thick, especially in the low-lying areas of the Earth. Coal-forming plants probably grew in swamps, and as the plants died, their debris gradually formed a thick layer of matter on the swamp floor. Over a prolonged period, this matter hardened into a substance called peat. The peat deposits became buried under sand or other mineral matter. As the mineral matter accumulated, some of it turned... 

The black product was extracted with water and the sodium carbonate in it was recovered by concentration and crystallization. The residue, chiefly calcium sulfide, known as galigu, was dumped on land and created an environmental nuisance for many years because it never hardened. The process was invented by N. Leblanc in France in 1789, in response to a competition organized by the French Academy of Sciences. Operation of the first factory was delayed for several years because of the French Revolution. The process was operated widely until it was progressively superseded by the Ammonia-soda process in 1872. But it was still in use in Bolton, UK, until 1938, and the last plant in Europe closed in 1992. See also Black ash. 

Ozone is a pungent pollutant. It causes eye irritation and at high levels can be lethal. Plant life suffers when exposed to even relatively low concentrations of ozone, and it causes rubber to harden and turn brittle. To protect tires from ozone, manufacturers have incorporated paraffin wax, which reacts preferentially with the ozone, sparing the rubber. As we ll see in Section 17-4, ozone is also formed by natural processes in Earth s stratosphere, where it filters out as much as 95 percent of the sun s ultraviolet rays. So, at Earth s surface, ozone is a harmful pollutant, while 25 kilometers straight up it serves as a sunscreen and is vital for the good health of all living organisms. 

In neither process is it commercially feasible to produce a dehydrated juice without the addition of a drying aid, although 100% orange juice has been produced with the continuous vacuum belt dehydrator (42,A3). This product is extremely hygroscopic and very temperature sensitive. As a result, the product "cakes" or hardens if exposed to moist air or to temperatures much above 24°C. The product is also subject to browning if not stored at refrigerated temperatures. Dehydrated citrus juices are produced on a vacuum belt dryer at Crystals International, Plant City, Florida, and are items of commerce. 

Lipids are constituents of plants and animals that are characteristically insoluble in water. Fats and oils are lipids that are triesters formed by reaction of the triol glycerol with long-chain saturated or unsaturated acids called fatty acids. The common acids in fats and oils have an even number of carbons (for example, stearic acid has 18 carbons), and, if unsaturated (for example, oleic acid), they have the Z configuration (Table 15.1 lists the fatty acids, with their common names). Hydrogenation of oils, which have a high percentage of unsaturated acids, converts them to solid fats in a process called hardening. 

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