This article presents a bibliographic and experimental study of the quality of vegetable oils, including walnuts oil, using fluorescents spectra. Pigments are the most important cause of food color. Each pigment has an absorption spectrum with peaks at characteristic wavelengths. Absorbance or absorbance ratios at those wavelengths can be used to estimate pigment concentrations. It is known that the tocopherols and carotenoids affect the oxidative stability of the oil, while the chlorophyll is in charge of photo–oxidation. The article includes some results on stability assessment of walnut cold pressed oil by calculating Photometric color index (PCI), Lovibond method approved by AOCS. This indicator allows us to compare quickly the influence of different processing methods and storage conditions of walnuts oils.