Abstract
The objective of this paper was to study the parameters of an extraction process of protein from castor bean cake by solubilisation in alkaline medium. Initially, the castor bean cake was ground, sieved and submitted to chemical analyses in order to determine its composition. The protein extraction was carried out in laboratory scale, under the following conditions: stirring speed of 400 or 600 rpm, temperature of 30 or 50 °C and cake/NaOH solution-ratio of 10 or 20 %, at constant pH = 9. The separation of the supernatant (extract) from the solid insoluble residue was done by centrifugation (4,000 rpm). The extracted protein yields were calculated and the chemical composition of both the freeze-dried extracts and dehydrated (40 °C/24 h) residues were determined. The composition of the castor bean cake was:39.3 ± 0.6 % protein; 9.2 ± 0.1 % moisture; 11.9 ± 0.0 % ash and 2.8 ± 0.5 % lipids. Higher protein yields (25.3 %) during the protein extraction process were observed when using lower cake-solution ratio (10 % at 400 rpm and 50 °C). That yield increased to 27.3 % when the solid insoluble residue was washed out with pure water and centrifuged again. The protein content of the freeze-dried extracts varied between 56.9 ± 0.7 (400 rpm, 20 % cake and 30 °C) and 64.8 ± 0.7 % (400 rpm, 20 % cake and 50 ºC, with residues washing), allowing to consider this product as a protein concentrate. Besides, the protein content of the dehydrated residues ranged from 32.4 ± 0.2 % (400 rpm, 20 % cake and 50 °C, with residue washing) to 35.3 ± 1.3 % (600 rpm, 20 % cake and 50 °C). The electrophoresis analyses of the extracted protein with bands between 37 and 51 kDa and between 19 and 29 kDa suggested that this can be a good raw material in the biodegradable film technology.
