Phytochemical content of roasted seeds of three white mustard (Sinapis alba L.) varieties differing in their glucosinolate and erucic acid content

White mustard (Sinapis alba L.) seeds differing in fatty acid and glucosinolate composition were tested. The varieties included Nakielska, a high erucic and high glucosinolate type, as well as two new white mustard varieties: Bamberka, with reduced levels of erucic acid, and Warta, with reduced levels of both glucosinolates and erucic acid. The secondary metabolite (phenolic compound) content was tested in extracts from the unroasted seeds and from seeds roasted at 140 degrees C, 160 degrees C and 180 degrees C for 15 min. We found that the improved mustard varieties had significantly higher fat content. Bamberka contained twice the level of free phenolic compounds of Nakielska, while the Warta variety had as much as 7.5 times more free phenolics. The qualitative and quantitative profiles changed depending on how the extracts were prepared. The crude extracts contained mainly sinapine. However, after acid and alkaline hydrolysis, three compounds dominated: sinapin, trans-sinapic acid, and methyl ester of sinapic acid. Principal component analysis showed that trans-sinapic acid (highly correlated with reducing power) and the methyl ester of sinapic acid (highly correlated with DPPH) were mainly responsible for the antioxidant properties. The higher the roasting temperature, the less was observed of phenolic compounds. The largest decreases were 17%, 28%, and 41 % for the Nakielska, Warta, and Bamberka varieties, respectively.