Colorimetric test application to the efficiency and shelf-life assessments of olive oil, sunflower oil and their blend used for frying frozen and fresh foods

Abstract

The frying-life of olive oil, sunflower oil and a their homogeneous blend used in 40 repeated and discontinuous frying of different food, mostly precooked and frozen foods, were comparatively determined by using the qualitative color test “Fritest” and color developed at 500 nm using this test (A₅₀₀). These measurements were significantly correlated (p< 0.001) to polar material, oligomer content and other thermaloxidation parameters The color selected to discard the oil -3 crosses- corresponds to A₅₀₀ of 0.35 and to 25 % polar material and 10-15 % of oligomers. The shelf life (< 3 crosses or A₅₀₀< 0.35) was 32 frying for olive oil, 22 fryings for sunflower oil, and 26 for their blend. The oil efficiency was assessed taking into account the weight decrease of foods, the oil loss, and the amount of food fried (kg food/L oil used) before oil discarding taking into account A₅₀₀< 0,35 o A₅₀₀< 0,4 cut-points. Olive oil presented a better efficiency (3.1 kg/L) than the sunflower oil and the blend (2.23 and 2.64 kg/L, respectively). Results suggest (i) the validity of the “Fritest” for a rapid evaluation of the alterations of different oils; (ii) the better efficiency and the longer shelf-life of olive oil than sunflower oil and the blend when frying different foods mostly pre-cooked and frozen foods.