Degumming 26 chlorophyll

Fats and Oils. The oxidation of fats and oils in food products can be prevented by the addition of citric acid to chelate the trace metals that catalyze the oxidation. Citric acid is also used in the bleaching clays and the degumming process during oil refining to remove chlorophyll and phosphohpids (59—63). 

A typical fat refining plant (Alfa-Laval process) for the acid washing of fats and oils is illustrated in Fig. 36.8.8 The triglyceride is degummed to remove phosphatides and other impurities such as mucilage, proteinaceous matter, and trace metals by acid washing with citric or phosphoric acids, and then is sent to a bleaching plant where it is dehydrated and treated with an activated clay for the removal of color bodies, heavy metals, chlorophyll, and polyethylene (Fig. 36.9).6... 

Alkali-refined oil, or specially degummed crude oil. Is bleached in preparation for hydrogenation or deodorization (including steam refining). Bleaching is an adsorption process in which surface-active clay is suspended in the oil under appropriate conditions to adsorb compounds that are sufficiently polar to be attracted to the active sites of the surfaces of clay particles. The compounds involved are soaps, oxidative breakdown products (Ney, 1964 Pardun eta/., 1968), and also colored compounds such as the chlorophylls, and to a minor extent, phosphatides and the carotenoids. The last are responsible for most of the reddish-yellow color that predominates in the oil, but which is far more efficiently removed by heat breakdown during hydrogenation or deodorization than by adsorption on bleach-... 

The membrane separation process was initially conducted in degumming vegetable oil and then was adapted for the recovery of carotenoids. Dense polymeric membranes are employed in this system and are very effective in the separatirm of xanthophylls, phospholipids, and chlorophyll, with retention of 80-100 %, producing an oil rich in carotenes [72,73]. This process, however, requires an additional step of hydrolysis or transesterification. Chiu, Coutinho, and Gruigalves examined the membrane technology as an alternative to concentrate carotenoids from crude palm oil in detriment of ethyl esters. A flat sheet polymeric membrane constituted by polyethersulfone was used and obtained a retention rate of 78.5 % [74]. Damoko and Cheryan obtained similar results using nanofiltration with 2.76 MPa and 40 °C in red palm methyl esters [75]. Whereas Tsui and Cheryan combined ultraiiltration with nanofiltration to separate zein and xanthophylls from ethanolic com extract [76]. 

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