Correlation between free fatty acids of vegetable oils evaluated by rapid tests and by the official method

The quantity of free fatty acids (FFA) provides important information about the hydrolytic rancidity in continuous deep-fat frying processes. The official method for the determination of FFA, based on titration, is slow and requires a trained analyst. FaSafe™ kits provide simple alternatives to colorimetrically measure the FFA content. They are fast, require less material, reagents and samples, and occupy smaller areas. The present study was designed to correlate the results obtained using the official AOCS method (Ca 5a-40) with those obtained using these kits. Linear regression and ANOVA tests were used for validation of the model and the comparison of averages, respectively. Samples of olive oils (n=40), crude and degummed vegetable oils (n=10), and refined oils (n=16) were analysed. The presence of colour in crude and degummed oils probably interfered with the value of the results obtained with the kits. For other samples, correlation equations were established: y=0.86x+0.05 (olive oils) and y=0.96x+0.01 (refined and olive oils), with a correlation coefficient of 0.99 for each. There was no statistically significant difference between the average values obtained by the two methodologies for either refined oils or olive oils.