Glucosinolate Levels in Canola
Glucosinolates contain both sulphur and nitrogen
Normal concentration can be 14 – 24 µmol/g dry leaves, and 55 – 115 µmol/g dry seeds. When present at too high a concentration in the oilcake affects thyroid function and causes goiters in monogastric animals. In poultry, glucosinolates cause other nutritional disorders.
The selection work carried out in the 1980’s and 1990’s have reduced the glucosinolate content more than five-fold and expanded the market for oilseed rape oil cake. Cultivars with remarkably low glucosinolate levels of 8 -15 μmol per g of seed are recently found in Poland. Breeding efforts are ongoing on for further reduction of glucosinolate content.
In the plant, glucosinolates plays an important role in defense mechanism of crop against pests and diseases. In the human body, consumption of Brassica species has been linked with reduced risk of cancers associated with the ability of the glucosinolate hydrolysis products to activate protective mechanisms within the body.
The sulphur input tends to increase the glucosinolate content but the current "00" varieties with very low glucosinolate content avoid this problem and optimal sulphur fertilisation ensures that it remains below critical levels. The effect of sulphur fertilisation is lower than the effect of the variety or the site.
