Contribution of Phospholipid Pyrrolization to the Color Reversion Produced during Deodorization of Poorly Degummed Vegetable Oils

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Abstract
The Ehrlich reaction was optimized to determine the formation of pyrrolized phospholipids in edible oils in an attempt to understand the color reversion produced during the deodorization of poorly degummed edible oils. The procedure consisted of the treatment of the oil with p-(dimethylamino)benzaldehyde in tetrahydrofuran/2-propanol at a controlled acidity and temperature and the spectrophotometric determination of adducts produced. The extinction coefficient of Ehrlich adducts was calculated by using 1-[1-(2-hydroxyethyl)-1H-pyrrol-2-yl]propan-1-ol (1) as a standard and was 15 300 M-1 cm-1. The response was linear and reproducible within the range of 0.334−48.6 μM of compound 1. When the assay was applied to a soybean oil treated with 100−1000 ppm of phosphatidylethanolamine and submitted to deodorization, the formation of pyrrolized phospholipids was observed at the same time that the disappearance of the phospholipid and the oil darkening were produced. The main changes were observed during the first steps of the deodorization process, when the oil was heated between 80 and 160 °C. During the initial heating of the oil until achieving 200 °C, oil darkening, phosphatidylethanolamine disappearance, and pyrrolized phospholipid formation were correlated, therefore suggesting a contribution of phospholipid pyrrolization to the oil darkening produced. Keywords: Carbonyl-amine reactions; nonenzymatic browning; oil degumming; oil deodorization; oil refining; phospholipid analysis; phospholipid modification; pyrrole derivatives; pyrrole polymerization