Application of non-destructive fast methods for quality assessment of sunflower oil

The sunflower oil is pressed from the seeds of the sunflower plant (Helianthus annuus). It contains high amounts of the essential fatty acid, linoleic acid. Sunflower oil is commonly consumed in foods. The quality of sunflower oil depends on the quality of the sunflower seeds to be processed, the storage conditions of the seeds before pressing and the refining conditions. The standard chemical methods used to determine the chemical content of the oils are usually time-consuming,labor-intensive and expensive. Therefore, we have tested four physical methods measuring refractive indices and their dispersion curves, color parameters, UV-VIS spectroscopic and fluorescence spectra that are related to the chemical structure and composition of the sunflower oils. The refractive indices of the samples were measured using a laser refractometer at wavelengths of 405 nm, 447 nm, 532 nm and 656 nm. The dispersion curves and the dispersion parameters were approximated using one-term Sellmeier model. The color parameters were obtained using a Lovibond PFX 880 spectrophotometer. The values for the refractive indices were compared to these, obtained by a standard method using the Abbe refractometer. These methods are fast, easy to perform and do not require any additional chemical agents. Four groups of sunflower oils – cold pressed, oil with added antioxidants and commercially refined and nonrefined sunflower oil, were investigated.