Oil recovery and lecithin production using water degumming sludge of crude soybean oils

BACKGROUND: Wet gums produced during aqueous degumming of crude soybean oils are currently processed to produce lecithin or added to meals to increase their nutritive value for animal feed. Oils occluded in these gums are generally not recovered or processed. In this work, three methods to recover occluded oil and obtain lecithin from wet gums were assayed: direct extraction of oil with cold acetone (Method I), extraction after water elimination under vacuum (Method II) and by solvent partition with hexane/ethanol (Method III). RESULTS: Higher oil yields (up to 588 g kg(-1) of occluded oil) were obtained when water was eliminated before extraction (Methods 11 and 111). No significant differences were observed in lecithin yields between three methods (720-807 g kg(-1) of dried gums). Recovered oils had acidity = 16.7-21.7 g kg(-1) as oleic acid, TOTOX (total oxidation) values <= 8.82, unsaponifiable matter = 9.0-12.1 g kg(-1), and Phosphorus = 87-330 mg kg(-1). Lecithins obtained by Methods I, II and III hexane phase had the same purity level (610-691 g of total measured phospholipids kg(-1)). CONCLUSIONS: The occluded oil in soybean wet gums can be recovered, with quality and stability indexes compatible with their reinsertion in the productive process, by water elimination and extraction with acetone. Lecithins can be obtained with different phospholipid composition and diverse application fields. (c) 2008 Society of Chemical Industry