Relationships between oxidative stability, triacylglycerol composition, and antioxidant content in olive oil matrices.
In olive oils, relationships between oxidative stability, glyceridic composition, and antioxidant content were investigated. Lipid matrices, obtained by purification of olive and high-oleic sunflower oils, were spiked with hydroxytyrosol, alpha-tocopherol, and mixtures of them and then subjected to oxidation in a Rancimat apparatus at 100 degrees C. At the same concentration of antioxidants, induction time (IT) decreased as the unsaturation rate of the matrix increased, but only fair correlations were found with fatty acid composition. Oxidative susceptibility (OS(TAG)) was calculated as a function of the relative oxidation rate of the triacylglycerols, and a linear relationship-IT (h) = (a + b)OS(TAG)-between induction time and this parameter showed a good correlation coefficient (r > 0.990, p < 0.001). In the case of matrices with a single antioxidant, origin ordinate (a) and slope (b) can be calculated as a function of the antioxidant concentration. In matrices spiked with mixtures of hydroxytyrosol and alpha-tocopherol, a simple relationship between the coefficients a and b and the concentration of antioxidants cannot be established because additive and subtractive effects occur depending on the relative concentrations of both antioxidants. However, approximate values for these coefficients can be obtained, allowing the estimation of the oil stability. In various olive oils, an acceptable agreement was found between the IT experimentally determined and that calculated from the oil composition. These results confirmed that the Rancimat stability of olive oils mainly depends on triacylglycerol composition and concentrations of o-diphenols and alpha-tocopherol.
Instituto de la Grasa (CSIC), Avenida Padre García Tejero 4, E-41012 Seville, Spain.
Raquel
R
Mateos
Mariana
M
Trujillo
M Carmen
MC
Pérez-Camino
Wenceslao
W
Moreda
Arturo
A
Cert
D000975:Antioxidants / Q000032:analysis*; D004355:Drug Stability; D000069463:Olive Oil; D010084:Oxidation-Reduction; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000032:analysis; D010938:Plant Oils / Q000737:chemistry*; D014280:Triglycerides / Q000032:analysis*; D024502:alpha-Tocopherol / Q000032:analysis
D000975:Antioxidants; D000069463:Olive Oil; D010938:Plant Oils; D014280:Triglycerides; C005975:3,4-dihydroxyphenylethanol; D024502:alpha-Tocopherol; D010626:Phenylethyl Alcohol