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A twin‐screw extruder for oil extraction: I. Direct expression of oleic sunflower seeds
Author(s) -
Dufaure Corinne,
Leyris Juliette,
Rigal Luc,
Mouloungui Zéphirin
Publication year - 1999
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-999-0206-0
Subject(s) - sunflower oil , extraction (chemistry) , screw press , sunflower , pressing , oleic acid , plastics extrusion , water content , chemistry , materials science , sunflower seed , moisture , food science , solvent , pulp and paper industry , chromatography , agronomy , composite material , biochemistry , biology , geotechnical engineering , engineering
Lipids are traditionally removed from seeds by mechanical crushing and solvent extraction. During the mechanical crushing process the oilseed is cleaned, cracked, flaked, and cooked before entering a mechanical screw press. Seventy‐five percent of the oil of sunflower seeds can be extracted by crushing, and the fatty cake then contains about 15% of oil. The oil levels remaining in the cake can be reduced to less than 2% by solvent extraction. However, the crude oil has to be refined as it contains many impurities and approximately 600 ppm phosphorus. A new process, in which sunflower seeds are pressed in a twin‐screw extruder, is examined here. The screw profile was first optimized. Oleic sunflower seeds were crushed and 80% of the oil was removed. The resultant oil was of good quality, with acid numbers below 2 mg KOH/g of oil and total phosphorus contents of about 100 ppm. The influence of pressing temperature and of fresh seed moisture content was determined. High pressing temperature and low moisture content improved oil extraction. The quality of the meal was examined through the solubilization of its proteins in alkaline water at 50°C. The fatty meal proteins remained quite soluble, and therefore one can assume that they were still relatively close to their native conformation. The pressing of oleaginous material in a twin‐screw extruder provides a new option to traditional processes.