Refining Vegetable Oils: Chemical and Physical Refining

This review presents recent technologies involved in vegetable oil refining as well as quality attributes of crude oils obtained by mechanical and solvent extraction. Usually, apart from virgin oils, crude oils cannot be consumed directly or incorporated into various food applications without technological treatments (refining). Indeed, crude oils like soybean, rapeseed, palm, corn, and sunflower oils must be purified or refined before consumption. The objective of such treatments (chemical and physical refining) is to get a better quality, a more acceptable aspect (limpidity), a lighter odor and color, longer stability, and good safety through the elimination of pollutants while minimizing oil loss during processing. However, the problem is that refining removes some essential nutrients and often generates other undesirable compounds such as 3-MCPD-esters and trans-fatty acids. These compounds directly influence the safety level of refined oil. Advantages and drawbacks of both chemical and physical refining were discussed in the light of recent literature. Physical refining has several advantages over chemical one.

Comparison of acid degumming methods and their influence on the formation of 3-MCPD-esters and glycidyl esters in sunflower oil deodorization

Degumming is the first stage in processing of vegetable oils, and it is aimed at removing phospholipids. The article compares the results of degumming by phosphoric and citric acids, their effects on the extraction of calcium and magnesium ions from oils, these ions being the main components of nonhydratable phospholipids. We showed the appropriateness of combining citric and succinic acids (the final content of phospholipids in oil was 0.034%, whereas it was equal to 0.048% when citric acid was used) and citric and ascorbic acids (the final content of phospholipids in oil was 0.040%). We studied the effect of acid degumming on the formation of 3-MCPD-esters and glycidyl esters. The content of glycidyl esters after degumming with citric acid and phosphoric acid was 310 g kg–1 and 200 g kg–1, respectively. After degumming with citric acid and phosphoric acid, the content of 3-MCPD-esters in the deodorized oil was 680 g kg–1 and 470 g kg–1, respectively. On the contrary, aqueous degumming does not increase the content of these esters in the deodorized sunflower oil (the content is less than 100 g kg–1) and its implementation can be recommended as one of the ways to prevent the formation of these toxic substances during deodorization.