Hull content and chemical composition of whole seeds, hulls and germs in cultivars of rapeseed (Brassica napus)

Objective: To study of the compositional breakdown of seed components between the integument and the germ and its variability according to genetic and environmental factors. Methods: The study used 19 rapeseed lots grown in two areas of contrasted agronomical potential harvested in 2011. Pure fractions of hulls and germs were mechanically separated by centrifuge impacts after freezing the seeds. Chemical composition of the whole seeds and the pure kernel and hull fractions was determined. The results were used to calculate the seed hull content. Results: Hull accounted for 18.2% of total seed content. Real oil content of the hulls (8.4% dry basis) was lower than in the literature. Hulls contained 2.9% of the oil, 11.2% of the proteins, 73% of the NDF; 80% of the ADF, 95% of the lignin and 6.0% of the glucosinolates of the whole seed. The percentage of hulls in total seed content shows low variability, although the oil and the protein content of the fractions were significantly affected by cultivar and to a lesser extent by geographic location of the crops. Conclusion: Completely dehulled seeds could result in a meal with 48.3% protein (dry basis) and low fiber content (10.8% NDF, 6.6% ADF, 0.5% ADL) but higher glucosinolate content (130% compared to defatted seeds).