Physical degumming

The organic and natural foods markets demand nonchemically treated oils. These often are made by hard pressing the source and water degumming the oil, followed by bleaching with natural (nonchemically treated) earths and removing FFA by physical refining. 

With physical rehning, the oil is first degummed and bleached and then fed to a continuous distillation (deodorization) unit, which removes the free fatty acids (92-95%) and volatiles. The rehned oil is blended as above. Frequently, distillation is stopped before removal of all of the free fatty acids, and the oil is alkali rehned to remove the remainder of the free fatty acids. This procedure has the advantage of ehminahng oxidation byproducts and pro-oxidant metals, thus improving product stabihty. 

The use of expanders does have an impact on the quality of the oil that the integrated processor should be aware of. An interesting phenomena of the expander is that while phosphorous levels in the extracted crude oil are normally increased over traditional flake extraction (typically as much as 200 ppm as P in soybean oil), nonhydratable levels in the degummed oil are normally lower. It is postulated that partial inactivation of the lipase enzyme (blamed for conversion of nonhydratable phosphatides) occurs in the expander and, while the crude oil has a higher neutral oil loss, the quality of the degummed oil is higher. In fact, one processor reported that despite aU efforts to make a soybean oil physical refining plant function, the oil was of substandard quality until the plant installed expanders. Once installed, the plant could consistently produce a quality physical refined oil (4). 

DEGUMMING, LECITHIN PROCESSING, AND PHYSICAL REFINING PRETREATMENT... 

Caustic refining in particular does not only effectively perform the separation functions described above but is considered more forgiving in operation than alternate physical methods. If the degumming operation has been less than perfect (or is not used), alkali refining will remove the bulk of the phosphatides. If a high amount of metals, particularly calcium and magnesium, are present, these can be... 

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