| Abstract | Five processes for the aqueous and ethanolic extraction of glucosinolates from rapeseed meal, ground seed and the intact seed were evaluated. All methods were effective in the detoxification of low and intermediate glucosinolate samples but two processes, in which 3.0 min boiling was used to inactivate myrosinase., failed to fully detoxify the high glucosinolate sample. The boiling treatment maintained sulfur levels in the oil below 10 ppm while the ethanolic NaOH extraction eliminated the sulfur contamination of the oil. The aqueous extracts from the meal experiment contained a high proportion of the meal nitrogen while losses of oil and nitrogen occurred in the ground seed extractions. The diffusion extractions of glucosinolates from the intact seeds were effective in controlling these losses and the yields of oil and meal exceeded the other processes.
Other disadvantages of the meal extraction method were the long (15 h) extraction period, slow drying of the meal slurry and the dark appearance of the product. The aqueous extraction of ground seed was relatively rapid (1 h) but the drying of the wet slurry and recovery of extract solids would increase the costs of the process. Each of the three diffusion extraction processes required large quantities of solvent and 6 h for the passive diffusion of glucosinolates from the rapeseed. The most effective solvent, ethanolic NaOH, denatured the meal proteins.
All of the extracted meals contained about 20% crude fiber. Dehulling the seed after diffusion extraction or air classification of the meal would be necessary to produce a high protein, food-grade rapeseed flour. |
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