Diffusion extraction of rapeseed glucosinolates with ethanolic sodium hydroxide

Abstract

Glucosinolates are readily diffused from whole rapeseed by repeated extractions with ethanolic sodium hydroxide. Four 2 hr extractions or six 1 hr extractions were most efficient for the diffusion of glucosinolates with minimum losses of other seed constituents. The ethanolic sodium hydroxide treatment inhibited myrosinase activity and lowered sulfur concentration in the oil. The oil from treated seed gave a higher hydrogenation number than the oil from untreated seed. The oil content of rapeseed was not substantially affected by the diffusion extraction process. Loss of diffused solids was ca. 15%, and loss of nitrogen did not exceed 10%. Most of the nitrogen diffused from the seed was nonprotein nitrogen. The principal disadvantages of the ethanolic sodium hydroxide procedure were reduced solubility of the rapeseed proteins and the higher fiber levels in the meals. The treated seed may be suitable, after partial dehulling or air classification, for the preparation of protein concentrates.