Date Published: January 12, 2012
Author(s): Kornsulee Ratanapariyanuch, Robert T Tyler, Youn Young Shim, Martin JT Reaney.
Large volumes of treated process water are required for protein extraction. Evaporation of this water contributes greatly to the energy consumed in enriching protein products. Thin stillage remaining from ethanol production is available in large volumes and may be suitable for extracting protein rich materials. In this work protein was extracted from ground defatted oriental mustard (Brassica juncea (L.) Czern.) meal using thin stillage. Protein extraction efficiency was studied at pHs between 7.6 and 10.4 and salt concentrations between 3.4 × 10-2 and 1.2 M. The optimum extraction efficiency was pH 10.0 and 1.0 M NaCl. Napin and cruciferin were the most prevalent proteins in the isolate. The isolate exhibited high in vitro digestibility (74.9 ± 0.80%) and lysine content (5.2 ± 0.2 g/100 g of protein). No differences in the efficiency of extraction, SDS-PAGE profile, digestibility, lysine availability, or amino acid composition were observed between protein extracted with thin stillage and that extracted with NaCl solution. The use of thin stillage, in lieu of water, for protein extraction would decrease the energy requirements and waste disposal costs of the protein isolation and biofuel production processes.
Brassica spp. oilseeds are grown throughout the world as sources of vegetable oil and protein-rich animal feed (Henriksen et al. 2009). According to statistical data from the Canada Grains Council (2011), the average annual production of Canadian canola over the period 2001-2010 was 9.2 million tonnes, and the Canadian oilseed crushing industry produced an average of 2.1 million tonnes of canola meal annually between 2001-2010. Commercial oilseed extraction may include solvent extraction, mechanical expeller-press extraction, or combinations of mechanical and solvent extraction to produce oil and meal. Canola meal is the portion remaining after extraction of oil from canola seed and it is widely used as a protein source in poultry, swine, beef, and dairy cattle feeds because of its excellent amino acid profile (Hickling 2011).
The composition of TS was reported separately (Ratanapariyanuch et al. 2011). In brief, stillage contained a number of organic and inorganic constituents that constituted a solution with about 3% dissolved matter. Our original hypothesis was that some of the dissolved constituents might either alter the efficiency of protein extraction or affect the quality of the extracted protein. Neither the efficiency of protein extraction nor the quality of protein was affected by the whole stillage. Therefore, we did not have reported the effect of individual components of the stillage on protein yield and quality. In this study, the relative efficiencies of protein extraction using TS and NaCl solution were used to determine the effect of these solutions. In addition, SDS-PAGE of extracted protein, amino acid sequences of tryptic peptide fragments of extracted protein, digestibility, and lysine availability of extracted protein were compared for protein extracted using TS and NaCl solution.
The authors declare that they have no competing interests.