Analysis of canolol (4-vinylsyringol) and its derivatives in rapeseed oil and sidestreams

Canolol (4-vinyl-2,6-dimethoxyphenol) was first discovered in the early 2000s, although its exact relationship to sinapinic acid in rapeseed was initially unclear. It is now known that 4-vinylsyringol is formed from sinapinic acid, which is one of the most important phenolic compounds in rapeseed. Sinapinic acid exists in various forms, including free acid, bound to glucose or choline esters, the latter of which is called sinapine. During the processing of rapeseed into oil, sinapic acid and sinapines are released and partially degraded, resulting in the formation of 4-vinylsyringol. Chemically, 4-vinylsyringol can be synthesized by decarboxylation of sinapinic acid, which is interesting for the food industry due to its flavors and antioxidant properties. Vinyl syringol also has biological effects such as anti-mutagenic, anti-inflammatory, and anti-cancer effects. It is also used as a starting material for epoxy compounds in technology, which are more environmentally friendly than conventional alternatives such as bisphenol A. During the processing of rapeseed, 4-vinylsyringol is mainly produced at high temperatures, where it occurs in oil and by-products in the form of monomers, dimers, and trimers. Dimerization occurs by radical coupling or photochemical reactions, whereby the formation of trimers is only observed in small quantities. Identification is mainly carried out by mass spectrometry and NMR, whereby the structures of monomers, dimers, and trimers are characterized. Extraction methods such as liquid-liquid, solid-liquid, and solid-phase extraction are used for quantification, whereby modern techniques such as supercritical fluid extraction are increasingly being used. Chromatographic methods, in particular HPLC with UV detection or mass spectrometry, enable the separation and analysis of phenols. The formation and occurrence of 4-vinylsyringol depend strongly on the processing conditions, in particular temperature, neutralization, and refining processes. During refining, many phenols are transferred to distillates, leading to enrichment, while they remain in the final product only in small amounts. Metabolome analysis shows that the concentration of precursors such as sinapinic acid varies in different countries, which influences the potential formation of 4-vinylsyringol.