A chemometric approach for the differentiation of sensory good and bad (musty/fusty) virgin rapeseed oils on basis of selected volatile compounds analyzed by dynamic headspace GC‐MS

Abstract

The aim of the present study was to differentiate sensory good and bad virgin rapeseed oils based on the composition of the volatile compounds by means of linear discriminant analysis (LDA). A total number of 64 compounds were detected by dynamic headspace GC‐MS and combined olfactometry with potential for sensory quality assessment either as aroma‐active compound by substance concentration or flavor property or as a non‐aroma‐active compound by correlation with the panel assessment. From this initial set of substances, 13 volatile compounds showed significant differences in the concentration between sensory good and bad oils, whereas their concentration was higher in sensory bad oils. No significant differences were found for compounds characterizing sensory good virgin rapeseed oils. Based on these 13 volatile compounds, the present work shows for the first time that LDA was able to classify a training data set of 43 samples satisfactorily according to the sensory quality. As a proof for suitability, a discriminant function was calculated and successfully used to classify samples from an additional validation sample set. Practical applications: Virgin rapeseed oils are high‐quality products on the market, which are defined above all by their sensory quality. The sensory evaluation of virgin rapeseed oils by a trained sensory panel group is time and labor consuming and sometimes the results are not reliable. Therefore, the development of an analytical method for the discrimination of sensory good and bad virgin rapeseed oils based on the determination and statistical evaluation of volatile, aroma‐active compounds is a helpful tool to support the sensory evaluation. The repeatability of the analytical method is better than the sensory evaluation, which also helps to support the work of a panel group. Additionally, the amount of work for a panel group can be reduced due to a pre‐selection by the analytical tool. The present work shows a chemometric approach to differentiate sensory good and bad quality virgin rapeseed oils on basis of 13 volatile compounds. For the first time volatile compounds have been identified that can be correlated with sensory bad virgin rapeseed oils.

Determination of Origin of Commercial Flavored Rapeseed Oil by the Pattern of Volatile Compounds Obtained via GC–MS and Flash GC Electronic Nose

“…It is noteworthy that previous researches considered sulfides (e.g., dimethyl sulfide and dimethyl trisulfide) as the important aroma compounds in the cold‐pressed rapeseed oils whereas they were rarely seen in the 33 FRO samples . Dimethyl trisulfide only existed in four samples, dimethyl sulfoxide in 17 samples, neither dimethyl sulfide nor dimethyl disulfide has been found in FRO samples in this study.…”

Micro‐organisms growing on rapeseed during storage affect the profile of volatile compounds of virgin rapeseed oil

“…Acetoin, 3‐methylbutanal and ethyl 2‐methylbutanoate were also identified as belonging to the 13 compounds with significant higher amounts in off‐flavour virgin rapeseed oils, which had been already identified in a previous study . Dimethyl sulfide, nonanal and 3‐methyl‐1‐butanol were also described for virgin rapeseed oil, although with no significant differences between sensory good and bad oils.…”

“…Although the number of samples for each group is relatively low, this result indicates that, in conspicuous rapeseeds, higher amounts of volatile compounds have been formed. A similar result was found for rapeseed oil when sensory bad oils showed a significant ( α = 0.05) higher average PA amount of volatile compounds (113.92 ± 11.37 PA) compared to the sensory good oils (98.98 ± 7.22 PA) . One reason for this finding could be that, during storage of rapeseed, ongoing metabolic processes lead to degraded lipids, amino acids and sugars, which result in volatile degradation products.…”

“…Notably, more compounds have been found in virgin rapeseed oil by Pollner and Schieberle, Gracka et al . and Bonte et al . The reasons for this are (i) the easier transfer of volatile compounds from the oil into the headspace in comparison to the seeds; (ii) the better extraction of volatile compounds from the oil by solvent assisted flavor evaporation (SAFE) or the purge‐and‐trap extraction technique compared to the SPME extraction; and (iii) the higher sensitivity of SPME combined with two‐dimensional GC compared to SPME combined with GC .…”

“…and Bonte et al . The reasons for this are (i) the easier transfer of volatile compounds from the oil into the headspace in comparison to the seeds; (ii) the better extraction of volatile compounds from the oil by solvent assisted flavor evaporation (SAFE) or the purge‐and‐trap extraction technique compared to the SPME extraction; and (iii) the higher sensitivity of SPME combined with two‐dimensional GC compared to SPME combined with GC . In addition, nonpolar aroma‐active compounds are considerably retained in oil or emulsions, making it more difficult to detect these compounds in a simple headspace analysis such as SPME.…”