Determination of cyanide in whole seeds and brans of linseed (Linum usitatissimum Linn) by molecular spectrophotometry

The addition of linseed ( Linum usitatissimum Linn) in the diet, as a functional food, has increased over the years. However, it possesses cyanogenic glycosides. This study aimed to quantify and compare cyanide concentration in whole seed and bran of brown and golden types to establish a safe limit of intake. Three commercial labels, from brown and golden whole seed types (Ab, Ag, Bb, Bg, Cb and Cg), and six commercial labels of brown and golden bran (1b, 2g, 3g, 4b, 5g, and 6b), were selected, totalizing twelve samples. Total cyanide concentration was quantified by a colorimetric method employing alkaline picrate, after acid hydrolysis. The whole seed cyanide values were between 348.4 and 473.20 µg/g and the bran cyanide values were between 459.53 and 639.35 μg/g. The analyzed bran presented increased cyanide concentrations than the whole seeds with no differences between brown and golden types. Food able to produce cyanide less than 90 µg/kg body weight, daily, is considered secure for consumption. Considering this limit and analyzed samples, it is safe to eat approximately two tablespoons of seeds or one tablespoon of bran. These results point out the importance of cyanide amount daily intake information to be in linseed packaging, to ensure secure consumption.