Rapid methods for predicting the appearance of turbidity in sunflower oil and their comparison with cold tests

Two rapid turbidimetric methods have been applied to determine the content of wax in refined and refined‐bleached sunflowerseed oils in the range of 0 to 120 ppm. Synthetic wax‐oil mixtures were prepared to construct calibration plots. Turbidimetric results were compared with visual evaluation of these mixtures as well as of the industrial oils by an expert panel, during 2 wk, under cold‐test (0°C) and tempering (15°C) conditions. Based on the standard AOCS cold‐test, the visual turbidity threshold of these Argentine oils was under 40 ppm, a value significantly lower than that found in European cultivars. Also, while both types of industrial oils passed the cold‐test, the refined oil developed cloudiness after tempering for 14 d, whereas the refined‐bleached oil remained transparent. Because the calibration plots showed that the turbidity difference values, given by these fast methods, corresponded to wax contents that caused visible turbidity but fell into the nonsensitive region of the instrument, a simple standard addition technique was used to extend their sensitivity to these low wax contents. With this improvement, oils that contained more than 40 ppm of wax by fast turbidimetry, which can be expected to develop cloudiness on storage in the winter season, can be promptly identified, thus allowing any desired corrective action.