Volatile compounds and other indicators of quality for cold‐pressed rapeseed oils obtained from peeled, whole, flaked and roasted seeds

Abstract

Cold‐pressed rapeseed oil is among the most popular virgin oils. Different processing methods yield oils varying in chemical composition and oxidative stability. The experiment aimed at identifying the differences (mostly in volatiles) between rapeseed oil obtained from peeled seeds (RO) and oils obtained by three pre‐treatment methods: pressing whole seeds (WSO), flakes (FO) and roasted flakes (RFO). Volatiles were analysed using GCxGC‐ToFMS and data were processed using statistical multivariate analysis. Fatty acid composition was determined using GC‐FID. The oils’ oxidative stability was measured using peroxide value. Free fatty acids’ value, absorbance at 236 and 238 nm and chlorophyll content were also determined. Also, a sensory panel evaluation was performed. PCA was found to be effective tool for differentiating the oils on the basis of their volatile compounds. RO was most similar to WSO from the second pressing. Fatty acid composition analysis yielded differences between the experimental oils and RO. RO had the highest PV, p‐AV and Totox values. WSO from the first pressing (WSO1) had the highest oxidative stability. Sensory analysis found that WSO1 was most similar to RO. Both oils had an intense cabbage‐like and fruity odour. The study showed that the results of volatile compounds’ analysis differs from those of sensory analysis in oils comparison.Practical applications: The results demonstrate that the rapeseed oil obtained from whole seeds may have a volatile compounds composition that is similar to that of rapeseed oil obtained from peeled seeds. PCA makes it possible to differentiate between samples varying in pre‐treatment method as well as between samples subjected to the same pre‐treatment method, but obtained from a second pressing. Sensory panel performed by trained panellists may demonstrate which oils are most desirable when rated for selected attributes. The results of sensory panel may differ from those of volatile compound analysis performed with GCxGC‐ToFMS.In the current study, the volatile compounds in cold‐pressed rapeseeds oil obtained from peeled seeds with those in rapeseed oils obtained from seeds prepared with various pre‐treatment methods are compared. The obtained results are compared with those of sensory evaluation. The study shows that the results obtained by means of statistical analysis based on volatile compounds do not always correlate with those of sensory panel evaluation in oils comparison.