Unraveling of the Fishy Off-Flavor in Steam-Treated Rapeseed Oil Using the Sensomics Concept

Abstract

The sensomics concept was applied to two steam-treated rapeseed oils, one eliciting a fishy off-flavor (OF) and the other the desired aroma attributes (PC = positive control). After screening the most important odorants via comparative aroma extract dilution analysis, identification experiments and quantitation via stable isotope dilution analysis (SIDA) using gas chromatography−mass spectrometry (GC-MS) were performed. Only five compounds differed in their concentrations by a factor ≥5. In addition, trimethylamine with an intense fishy odor quality and first overlooked by gas chromatographyolfactometry, was only present in OF and finally characterized via ion exchange chromatography and solid phase microextraction GC-MS. For data validation, recombination experiments were performed using all odorants with OAVs ≥ 1, and excellent accordance between GS and OF and their corresponding recombinates was achieved, confirming a correct characterization of all key odorants with trimethylamine as the only odorant responsible for the fishy off-flavor.

Lipid-derived flavor and off-flavor of traditional and functional foods: an overview

“…This was particularly noticed for rapeseed/canola oil in which ammonia was generated from the breakdown of glucosinolates and/or sinapine. This was nicely demonstrated by Matheis and Granvogl (2019a) in their recent research findings. In addition, the authors (Matheis and Granvogl, 2016) also found that the main difference of key odorant between desired sensory attributes and fusty/musty off-flavor in rapeseed oils was the discrepancy of concentration of certain compounds, such as 2-and 3-methylbutanoic acid, 2-methoxyphenol, and ethyl 2-methylbutanoate.…”

Flavor of rapeseed oil: An overview of odorants, analytical techniques, and impact of treatment

“…It was shown that phosphatidylcholine can generate trimethylamine in soybean oil (Jiang et al., 2016). Thus, Matheis and Granvogl (2019a) supposed that trimethylamine was formed during the steaming process from sinapine (bearing a choline ester in the side chain analog to phosphatidylcholine) as a possible precursor. Overall, the fishy smell might be caused by the synergism of several volatile compounds, which needs further research.…”

“…Further, some odorants might also be overlapped by the solvent peak during GC analysis (Parker, 2015). Thus, the HS technique is often applied in parallel to SAFE to identify very volatile aroma‐active compounds co‐eluting with the solvent peak, for example, dimethyl sulfide and methanethiol (Matheis & Granvogl, 2019a; Ortner et al., 2016). This combination ends up with a suitable analytical approach to detect all aroma‐active compounds in food.…”

“…It includes aroma profile analysis, AEDA, SIDA, determination of odor thresholds followed by the calculation of OAVs, and aroma recombination experiments. Recently, the key odorants of rapeseed, mustard seeds, native cold‐pressed rapeseed oils eliciting the desired flavor and a musty/fusty off‐flavor, and steam‐treated rapeseed oils eliciting the desired flavor and a fishy off‐flavor were successfully elucidated by application of the molecular sensory science concept (Matheis & Granvogl, 2016a, 2016b, 2019a, 2019b; Ortner et al., 2016).…”

“…Flavor is one of the most critical criteria for customers to choose edible oils. At the same time, improper storage and processing of seeds and oils can lead to off‐flavors in rapeseed oil (fusty, musty, and rancid) (Bonte et al., 2017; Matheis & Granvogl, 2016b, 2019a, 2019b). During the past decade, more and more attention has been paid to the flavor of rapeseed oil, odorants in particular.…”