Deodorisation process

Crude palm oil is rich in minor components such as carotenoids, tocopherols, tocotrienols, sterols, phospholipids, triterpene alcohols, squalene, aliphatic alcohols and aliphatic hydrocarbons (Goh et al. 1985). The major components of interest are the carotenes, tocopherols, tocotrienols, sterols and squalene (Table 3.10). Carotenes and tocopherols are antioxidants and stabilise the oil against oxidation. During refining, the bleaching and steam deodorisation processes partially remove some of these valuable components. The amounts retained in the refined oils depend on the conditions of refining. 

Devulcanising rubber can result in products that have bad odours, and this has been addressed in this system by the use of a novel deodorisation process that involves the injection of high-pressure water into the extruder. Odour-producing compounds are trapped in the high-pressure water vapour and removed via vents. 

Finally, the oil undergoes a number of refining processes to produce a purified oil. These refining processes may include degumming, in which phospholipids are removed as gums in a hydration process neutralisation and washing to remove free fatty acids, trace metals and other water solubles oxidation and deodorisation to remove by-products and polishing to remove trace oil insolubles. 

The main component of the tocopherol mixture is a-tocopherol which makes up 95% of the total. The other 5% of the mixture consists of (J>- and y-tocopherols. All tocopherols occur in the free (non-esterified) form. The vitamin E(mg) PUFA(g) ratio in olive oil is approximately 1.8. In countries with a high annual per capita consumption, a significant percentage of the daily requirement for vitamin E is covered by olive oil. Refined, bleached, and deodorised olive oils have markedly reduced tocopherol content because of losses during processing. 

Tocopherols and squalene are eliminated when the olive is processed. Deodorisation sludges are rich in squalene and can be used as a source of this hydrocarbon for industrial purposes. Squalene losses are accompanied by formation of squalene isomers. 

Bleaching is achieved by adsorption on activated bleaching clays (sorbents of the aluminium silicate type) or in combination with other adsorbents (such as activated carbon, also known as activated charcoal) to remove oil soluble pigments (such as carotenoids and chlorophylls), residual phosphoHpids, and eventually soap residues resulting from the deacidification process. Volatile substances are removed by deodorisation via steam distillation under reduced pressure. The volatile compounds are mainly responsible for the unpleasant smeU and aftertaste of cmde oil, so this process provides organoleptically neutral, indifferent oils. 

Polymerisation refers to processes in which the overall composition of a compound does not substantially alter, but the molecular weight increases by a multiple of the weight of the monomer. Polymers usually arise when a system can create free radicals. Therefore, polymerisation reactions usually accompany isomerisation reactions and the formation of cyclic fatty acids under extreme heating. In the fully refined (and thus also deodorised) edible oils, polymers represent several tenths of a percent, but their content increases during heating. Oils with a polymer content of more than 10% are not recommended for use. 

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