Optimization of analytical methods for the assessment of the quality of fats and oils used in continuous deep fat frying

Abstract

Frying oils with different alteration degrees were collected from continuous frying systems at various Spanish companies. These samples were used to evaluate the applicability, repeatability and capability of a number of methods to discriminate between samples of different degrees of oxidation. The objective of this work was to find complementary methods to the acid value determination for the routine quality control of the frying oils used in these companies. The optimization of the dielectric constant determination was accompanied by a clear variability improvement. However, except for the TBA value, the methods assayed showed lower variability. In addition, TBA value determination was discarded because this parameter showed insufficientsensitivity to discriminate between oil samples with different degrees of oxidation. Relationships between the alteration parameters determined in the frying media showed significant correlations between the acid value and several different oxidation parameters, such as the p-anisidine value, dielectric constant, lipid UV absorption and polymerized triacylglycerol content. Thus, since the acid value exclusively evaluates the hydrolytic alteration, these parameters give complementary information because they evaluate the thermoxidative alteration.