Abstract
Canolol (2,6-dimethoxy-4-vinylphenol, 4-vinylsyringol), which is formed by thermally initiated CO2 splitting off from sinapic acid, possesses a high antioxidant potential. Furthermore different positive physiological properties are described. Due to rapeseed’s high content of phenolic acids, particularly sinapic acid, it is obvious to produce canolol as by-product of rapeseed processing. Roasting of rapeseed meal or cake in a fluidized bed followed by extraction with supercritical carbon dioxide of the formed canolol represents a production procedure which not impairs the commercial oil mill process. This article summarizes results from the roasting process with rapeseed meal and cake in fluidized bed equipments of different design and size showing that it is a suitable technique to transform sinapic acid into canolol. The achieved canolol contents are at 500 mg/kg in minimum, if the material is rapidly cooled-down after reaching the optimal temperature of 165 °C. Further roasting leads to a fast reduction of the canolol content. In addition it could be observed, that the sinapic acid content is not decreasing in the same amount as the canolol content increases. Sinapic acid seems to be “reproduced” during roasting. The reaction mechanisms of the described phenomena are not known.
Highlights
In comparison to the most other kinds of oilseeds rapeseed contains considerably more phenolic acids (Naczk, 2002), existing in free, esterified or insoluble bounded form
To intensify the roasting process the reactor was equipped with an electric trace heating system
The present investigation shows that this is valid for roasting of rapeseed meal or cake in a fluidized bed (Fig. 6)
Summary
In comparison to the most other kinds of oilseeds rapeseed contains considerably more phenolic acids (Naczk, 2002), existing in free, esterified or insoluble bounded form. An ester of sinapic acid and choline, is the main compound of the esterified phenolic acids, and in the literature contents between 0.6 and 2.5% are described (Baumert et al, 2005; Fenwick and Hoggan 1976; Müller et al, 1978). Artz et al (1986) showed that the phenolic compounds are mainly localized in the cotyledons, whereas in the hulls only traces exist. Similar results for the distribution of sinapine in rapeseed were found by Krygier et al (1982) and Matthäus (1998)
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