A re-examination of the technical feasibility and economic viability of rapeseed dehulling

The recent success of dehulled sunflower meals on the French market encourages reconsideration of the possibility of applying dehulling techniques to rapeseed. Hulls account for 18-20% of rapeseed mass; they contain mostly fibres (72%, 78% and 99%, respectively of the seeds' NDF, ADF and ADL). Complete removal of these hulls would result in a high (43%) protein meal with enhanced added value. However, the technical feasibility of producing such a meal is impeded by the relatively high oil content of the hull fraction. This article presents a model of mass balance that takes account both of the purity of the "hull" and "kernel" fractions and comparisons of gross margins between conventional processing and dehulling-based processing. The value of dehulled rapeseed meal is assessed against both a range of market scenarios and the composition and price of a selection of alternative feeds. The gross margin differential favours dehulling only in periods where proteins are expensive and oil relatively cheap, as at present. Reducing the oil content of the hulls affects considerably the profitability of dehulling whereas modification of the protein content has only a modest impact. An important unknown is the effect of antinutritional factors on the final price of dehulled meals. Management of the glucosinolates residues through processing might decrease their noxiousness though the information on this is scant. Since this lack of knowledge is an impediment to the implementation of dehulling technology, research and development investments should start by addressing this question. Technical solutions could be developed to recover the oil contained in the hulls. Such solutions include expelling, aqueous extraction or tail-end dehulling after direct extraction of the seeds.