Detection of allergenic proteins in refined oils

Previously, it has been assumed that the processes involved in refining edible oils remove the proteins that might act as allergens. Researchers at the University of Florence in Italy have now developed methods for the extraction and analysis of any residual proteins in commercial samples of soy, peanut, sunflower and maize oils.

Their study, recently published in the journal Food and Chemical Toxicology, developed an optimised protein extraction method which was applied to commercial food oil samples. Extracted proteins were quantified by colorimetric assays and amino acid analysis, and preliminary tests were carried out to assess the allergenicity of the extracted proteins.

Extremely low protein content, varying from 6.5 - 19 μg/100 ml, was detected in the oils, and electrophoresis of the protein extracts allowed estimates of their molecular weights. Extracted proteins were analysed against sera derived from children allergic to soy, maize or peanut allergens, with sera from non-allergic children used as a negative control.

Proteins were present in the two commercial samples of soybean oil, the two maize oils plus the peanut oils that were analysed. There was a lack of response to the sera for soybean and maize extracts, however, results from the tests with the peanut allergic-child sera showed the presence of IgE responsive proteins.

The authors concluded by suggesting that immuno-based methods should be applied more widely to refined seed oils before it can be confidently asserted they are safe for allergic individuals.

Reference: Ramazzotti et al. 2008 Analytic investigations on protein content in refined seed oils: implications in food allergy. Food and Chemical Toxicology (article in press, available on-line 15 August 2008).