Quantification and Partial Characterization of the Residual Protein in Fully and Partially Refined Commercial Soybean Oils
2011
Rigby, Neil M. | Sancho, Ana I. | Salt, Louise J. | Foxall, Rob | Taylor, Steve | Raczynski, Ana | Cochrane, Stella A. | Crevel, Rene W.R. | Mills, E.N Clare
A method has been developed to determine residual protein in refined oils, a potential trigger of allergic reactions. High-pH bicarbonate or borate buffers were found to be the most effective extractants, residual oil protein comprising a mixture of proteins of Mr 6000−100000. Extracted protein could be quantified with superior precision using 3-(4-carboxybenzoyl)quinolone-2-carboxaldehyde (CBQCA). Residual protein content determined in a set of oils using the borate extraction−CBQCA assay was positively correlated with contents determined using a bicarbonate−total amino acid analysis method. Oil refining substantially reduced the oil protein content determined by the borate−CBQCA assay with neutralized/refined, bleached, and deodorized (fully refined) oils containing 62−265 ng/g oil, whereas crude un-degummed oils contained 86000−87900 ng/g of protein. These analyses and published data on cumulative threshold doses for soybean suggest that even the most sensitive individuals would need to consume at least 50 g of highly refined oil to experience subjective symptoms.
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