Quality evaluation of cold pressed sunflower oils by sensory and chemical analysis

A quantitative descriptive analysis (QDA (R)) was developed to characterize the sensory quality of a set of 14 cold pressed sunflower oils present on the Italian market. The oils' chemical quality (free acidity, peroxide value, oleic acid, linoleic acid and volatile profile) was also defined. Eighteen sensory descriptors, selected by a trained panel, allowed for thorough profiling of the specimens. Some of the oils were characterized by dominant positive sensory notes typical of cold pressed sunflower oils (sunflower seeds and nutty), some by mild notes of refined sunflower oils, while others by negative sensory attributes (especially rancid/fried oil). The volatile profiles of the samples (by solid phase microextraction - gas chromatographic analysis, SPME-GC) were well in agreement with the data provided by the sensory judgment: the samples characterized by olfactive and retro-olfactive notes of sunflower seeds evidenced many terpenic compounds that were practically absent in oils judged as mild ones (similar to neutral refined sunflower oils). Moreover, the samples defined as defective for the presence of rancid/fried oil negative attribute, showed higher amounts of the E-2-heptenal, a volatile aldehyde marking lipid oxidation. Practical applications: The QDA (R) developed in this work is useful for characterization of the sensory quality of commercial cold pressed sunflower oils. The sensory quality appears to discriminate between genuine cold pressed sunflower oils, characterized by positive peculiar notes, and mild samples more similar to the neutral refined sunflower oils or defective samples. The study of the volatile profiles confirms the suitability of the proposed sensory descriptors, while the analysed chemical parameters give an interesting picture of the quality of the commercial sunflower oils, sold as cold pressed.