Oil technology

Abstract

The processing of oilseeds and oil-bearing fruits becomes more and more important because an increasing number of people need more and more oil for human nutrition and also for technical applications. In general, three different methods for the extraction of oil are conceivable: (1) pressing, (2) extraction by solvent, and (3) a combination of pressing and extraction by solvent. The efficiency of these methods can be improved with the assistance of enzymes or carbon dioxide. Pressing is a very old method which nowadays is most widely displaced by the use of solvent which is more efficient, especially for oilseeds with lower oil contents such as soybeans. Seeds with higher oil contents are pre-pressed before extraction by solvent. For the production of high-quality virgin oils, only pressing by a screw press and purification by sedimentation, filtration, or centrifugation is allowed. Because of the extensive extraction process in large facilities which results in the extraction and the formation of undesired compounds in the raw oil, making it unusable for human nutrition or technical applications, a comprehensive purification by a refining process of the raw oil is inevitable. The chapter describes the different methods of oil processing and the different requirements necessary for the production of high-quality vegetable oils in large oil mills, and also in small and medium-sized facilities. Difficulties arising from both methods are also discussed. The chapter discusses the different aspects of oil pro-cessing from the pretreatment of the raw material via extraction by pressing or sol-vent extraction to the purification by filtration, sedimentation, or refining. The different steps of the refining process, degumming, chemical or physical refining, bleaching, and deodorization are described. The influence of different steps of pro-cessing on the oxidative stability of the oil is the subject of the chapter. Last but not