Rapeseed press cake, a co-stream from oil pressing, is a promising source of food quality protein. In July 2014, rapeseed protein was approved for marketing in the EU as a novel food ingredient. The press cake contains 36-40% protein, 35% carbohydrates and lignin, oil and ash as its main chemical components. Majority of the protein is stored in protein bodies inside the kernel cells. These cells are in turn surrounded by cell walls composed of a strongly interconnected network of cellulose, xyloglucan, xylan and pectic polysaccharides.
In the study by Rommi et al. (2014), cell wall and pectin-degrading enzyme preparations were used to enhance protein release from rapeseed press cake. Rapeseed press cakes from cold pressing of intact Brassica rapa and partially dehulled Brassica napus seeds were treated with pectinolytic (Pectinex Ultra SP-L), xylanolytic (Depol 740L) and cellulolytic (Celluclast 1.5L) enzyme preparations. Pectinex caused effective disintegration of the kernel cell walls through hydrolysis of pectic polysaccharides and glucans, and increased protein extraction by up to 1.7-fold in comparison to treatment without enzyme addition. Accordingly, 56% and 74% of the total protein was extracted from the intact and dehulled press cakes. Light microscopy of the press cakes suggested that pectins were present also inside the kernel cells where they were co-localized with proteins. Enzymatic hydrolysis of these intracellular pectins as well as deconstruction of kernel cell walls was concluded to relate with enhanced protein release.
For more information:
Rommi, K., Hakala, T.K., Holopainen, U., Nordlund, E., Poutanen, K., Lantto, R. (2014). Effect of Enzyme-Aided Cell Wall Disintegration on Protein Extractability from Intact and Dehulled Rapeseed (Brassica rapa L. and Brassica napus L.) Press Cakes. J Agric Food Chem, 62(32), 7989-97. doi:10.1021/jf501802e.
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