The results suggest that most physicochemical, thermal and functional properties of CPIs compare favourably with those of SPI and are better than those of PPI. Hence CPI may be suitable as a high-quality substitute for SPI in food applications.

-Protein rich meal is a valuable co-product of canola/rapeseed oil extraction. Seed storage proteins that include cruciferin (11S) and napin (2S) dominate the protein complement of canola while oleosins, lipid transfer proteins and other minor proteins of non-storage nature are also found. Although oil-free canola meal contains 36-40% protein on a dry weight basis, non-protein components including fibre, polymeric phenolics, phytates and sinapine, etc. of the seed coat and cellular components make protein less suitable for food use. Separation of canola protein from non-protein components is a technical challenge but necessary to obtain full nutritional and functional potential of protein. Process conditions of raw material and protein preparation are critical of nutritional and functional value of the final protein product. The storage proteins of canola can satisfy many nutritional and functional requirements for food applications. Protein macromolecules of canola also provide functionalities required in applications beyond edible uses; there exists substantial potential as a source of plant protein and a renewable biopolymer. Available information at present is mostly based on the protein products that can be obtained as mixtures of storage protein types and other chemical constituents of the seed; therefore, full potential of canola storage proteins is yet to be revealed.Keywords: Canola / rapeseed storage proteins / cruciferin / napin / protein digestibility / functional properties Résumé -Protéines de canola et de colza : fonctionnalités et nutrition. Les tourteaux riches en protéines repré-sentent un coproduit de valeur de l'extraction de l'huile de canola/colza. Dans la graine, les protéines de stockage, notamment la cruciférine (11S) et la napine (2S), dominent la fraction protéique du canola, mais des oléosines, des protéines de transfert de lipides et d'autres protéines mineures non dédiées au stockage sont également présentes. Bien que le tourteau de canola déshuilé contienne 36-40 % de protéines sur poids sec, la présence de composants non protéiques, dont les fibres, les polymères phénoliques, les phytates, la sinapine, etc. issus de l'enveloppe de la graine et des composants cellulaires rendent les protéines moins appropriées à une utilisation en alimentation humaine. Cette revue présente les connaissances actuelles en termes de valeur nutritionnelle et fonctionnelle des protéines issues des graines de canola. La séparation des protéines de canola des composants non protéiques représente un défi technique mais nécessaire pour libérer totalement le potentiel nutritionnel et fonctionnel de la protéine. Les protéines de stockage de canola peuvent satisfaire un grand nombre d'exigences nutritionnelles et fonctionnelles pour des applications alimentaires. Les macromolécules protéiques de canola offrent également des fonctionnalités requises dans les applications dépassant les seules utilisations alimentaires ; un potentiel important existe en tant que source de protéines végétales et de biopol...

Cruciferin is the major storage protein in Brassicaceae family oilseeds. The predominant cruciferin isoforms in Arabidopsis thaliana were investigated using homology modeling (HM) for their molecular structures and functional properties. The structure of Brassica napus procruciferin was used as the template for HM to determine the molecular structures and hypervariable regions. Hydrophobicity and electrostatic surface potential distribution on the intradisulfide-containing face (IA) and the interdisulfide-containing face (IE) indicated favorable interfacial and solubility properties. More heat-induced structural changes were predicted for the CruC homotrimer than for the CruA or CruB homotrimers. Structural features that facilitate flavor binding and limit proteolytic digestion were more readily observed in CruA and CruB than in CruC. On the basis of these comparative models, structural differences among cruciferin isoforms and their relevance to potential technofunctionalities were identified. This approach of functional property prediction will link protein structure to utilities and will be valuable in designing proteins for targeted applications.

Arabidopsis thaliana lines expressing only one cruciferin subunit type (double-knockout; CRUAbc, CRUaBc, or CRUabC) or devoid of cruciferin (triple-knockout; CRU-) or napin (napin-RNAi) were generated using combined T-DNA insertions or RNA interference approaches. Seeds of double-knockout lines accumulated homohexameric cruciferin and contained similar protein levels as the wild type (WT). Chemical imaging of WT and double-knockout seeds using synchrotron FT-IR spectromicroscopy (amide I band, 1650 cm(-1), νC═O) showed that proteins were concentrated in the cell center and protein storage vacuoles. Protein secondary structure features of the homohexameric cruciferin lines showed predominant β-sheet content. The napin-RNAi line had lower α-helix content than the WT. Lines entirely devoid of cruciferin had high α-helix and low β-sheet levels, indicating that structurally different proteins compensate for the loss of cruciferin. Lines producing homohexameric CRUC showed minimal changes in protein secondary structure after pepsin treatment, indicating low enzyme accessibility. The Synchrotron FT-IR technique provides information on protein secondary structure and changes to the structure within the cell.