Nutritional and bioactive properties of glabrous canaryseed (Phalaris canariensis, L.) proteins

In 2015, glabrous canaryseeds were approved for human consumption by Health Canada and the FDA as a new cereal grain.Formerly, the seeds could only be used as birdseed since they were lined with inedible, hair-like silica fibers, however, the new hairless seeds are high in protein (22% w/w) and have immense potential for use by the food industry.The objective of this study was to compare the nutritional quality and bioactive properties between two yellow (C09052 & C05041) and two brown (CDC Calvi & CDC Bastia) hairless canaryseed cultivars and as compared to two common cereals (oat and wheat).Overall, canaryseed proteins have a well-balanced amino acid profile and the seeds are high in tryptophan (2.4-2.6 g/100g protein), an essential amino acid normally deficient in other cereal grains, but low in essential amino acid lysine (2.3-2.9 g/100g protein).The protein quality of canaryseed flours were evaluated by two protein quality scoring methods; the Protein Digestible Corrected Amino Acid Score (PDCAAS) and the Digestible Indispensable Amino Acid Score (DIAAS).The PDCAAS score was calculated from the overall digestibility (in vitro protein digestibility) of canaryseed protein and had scores of 25.4-32.4% for infants (0-6 months).These values were comparable to those of wheat (26%), but lower than those of oat (47%).The minimal and maximal in vitro total ileal amino acid digestibility values and DIAAS scores were determined by measuring the bioaccessibility of each individual amino acid.The total ileal digestibility for the four canaryseed varieties ranged from minimal values of 25 to 29 % to maximal values of 65 to 71%, with the yellow varieties showing higher digestibility values.These values were comparable to those of wheat (22 to 73%) and oat (32 to 69%).The DIAAS scores showed that lysine was the limiting essential amino acid, producing in vitro DIAAS scores of 7.9-9.5%,9.7-11.5%,11.5-13.7%for infants (0-6 months), children (6 months-3 years), and older children/adults, respectively.These results indicate that even though the canaryseeds are high in tryptophan, the quantity and digestibility of the limiting amino acid lysine remains low, therefore, as for other cereals, they must be complemented by other protein sources in order to meet dietary requirements of essential amino acids.Trypsin inhibitor activity (TIA), phytic acid, and total polyphenol content (TPC) were determined in canaryseed flours and isolates to evaluate the anti-nutritional components in the seeds and there iii was no significant difference between canaryseed cultivars.TIA in canaryseed flours (0.12-0.16 mg/g) were comparable to oat (0.14 mg/g) and wheat (0.11 mg/g) flours.The phytic acid content in canaryseeds (12 mg/g flour) was significantly higher than oat (6 mg/g flour) and wheat (3 mg/g flour), but comparable to levels found in other cereals and legumes.TPC of canaryseeds (1.4 mg FAE/g flour) was higher than wheat (0.6 mg FAE/g flour) but lower than oat (2.0 mg FAE/g flour).TPC was higher in canaryseed isolates than in the flours, most likely due to higher presence of free and polyphenols-protein complexes (bounded polyphenols) in the canary protein isolates.Finally, the health promoting effects of the four canaryseed varieties were also evaluated and compared to those of oat and wheat by measuring the potential antioxidant, (ORAC, DPPH, ABTS), chelation (Fe2+), antihypertensive (ACE), and antidiabetic (DPP-IV) activities of cereal flour hydrolysates after ultrafiltration with a 3K MWCO filter to obtain small and active peptides.Between canaryseed cultivars, there was no significant difference between brown and yellow canaryseeds except for the DPPH and Fe 2+ assays, where the brown varieties demonstrated superior activity (IC50 values of 77.96-96.38 µg/mL and 0.73-0.96mg/mL for DPPH and Fe 2+ assays, respectively) as compared to the yellow canaryseed cultivars (IC50 values of 638.75-1043.55µg/mL and 1.55-1.69mg/mL for DPPH and Fe 2+ assays, respectively), indicating brown cultivars may have better radical scavenging activity as compared to the yellow cultivars.As compared to oat and wheat, the antioxidant activity of canaryseed proteins was equivalent or superior for each assay tested.For the ORAC assay, canaryseeds, oat, and wheat had an activity of 1.77-1.99µmol TE/mg protein, 1.31 µmol TE/mg protein, and 1.54 µmol TE/mg protein, respectively.For the ABTS assay, the yellow C09052 canaryseed protein had IC50 values 117.85 µg/mL, which was not significantly different than wheat (107.84 µg/mL), and lower than oat (176.01 µg/mL).The C09052, C05041, and Calvi canaryseed peptides had exceptional ACE inhibition activity with IC50 values of 333 µg/mL, 405 µg/mL, and 322 µg/mL, respectively, as compared to oat (570 µg/mL) and wheat (781 µg/mL).IC50 values for the DPP-IV inhibition assay were 1.0 mg/mL, 1.1 mg/mL, and 1.4 mg/mL for C09052, C05041, and Bastia peptides, respectively, and comparable to wheat (1.0 mg/mL).To identify potential antihypertensive peptides, the C09052 3K MWCO digest was further purified by size exclusion chromatography, which showed three main peaks, and these three peaks were vii de 1.77-1.99µmol TE/mg protéine, 1.31 µmol TE/mg protéine et 1.54 µmol TE/mg protéine, respectivement.Pour la méthode ABTS, les protéines des graines de l'alpiste des Canaries jaune C09052 avaient une valeur de l'IC50 de 117.85 µg/mL, ce qui n'est pas significativement différent du blé (107.84 µg/mL) et plus faible que l'avoine (176.01 µg/mL).Les peptides des graines d'alpiste des Canaries des cultivars C09052, C05041 et Calvi avaient une activité des inhibiteurs de l'angiotensine (ACE) exceptionnelle avec des valeurs IC50 de 333 µg/mL, 405 µg/mL et 322 µg/mL, respectivement, en comparaison avec l'avoine (570 µg/mL) et le blé (781 µg/mL).Les valeurs IC50 pour l'essai d'inhibition de la DPP-IV étaient de 1.0 mg/mL, 1.1 mg/mL et 1.4 mg/mL pour les peptides des cultivars C09052, C05041 et Bastia respectivement, des valeurs comparables à celles du blé (1.0 mg/mL).Afin d'identifier des peptides ayant un effet antihypertenseur potentiel, le digestat du cultivar C09052 ultrafiltré sur une membrane de 3K MWCO a été purifié par chromatographie d'exclusion stérique, ce qui a montré trois pics, et ces trois pics ont été récoltés et évalués à nouveau pour l'activité d'inhibition de l'angiotensine (ACE).Les fractions 1 et 2 présentaient une activité ACE similaire (32% and 29%, respectivement) à une concentration en peptides de 350 µg/mL, cependant, la fraction 1 a été choisie afin d'être davantage purifiée puisque celle-ci avait la teneur en protéine la plus élevée et une valeur d'inhibition ACE de 82% à une concentration protéique de 3 mg/mL.L'analyse par spectrométrie de masse (MS) de la fraction du cultivar C09052 a identifié 46 peptides appartenant à 18 protéines de la sous-famille des Pooideae.Parmi les 18 protéines identifiées, 14 étaient homologues aux protéines de l'orge, tandis que les autres étaient homologues au blé (3) et à l'égilope cylindrique (1).L'analyse in silico des peptides a démontré que l'ensemble des 46 peptides présentaient des activités potentielles d'inhibition de l'angiotensine (ACE) et d'inhibition de l'activité de la DPP-IV, alors que 20 avaient un pouvoir antioxydant potentiel, lequel a été validé à partir des études in vitro.Cependant, d'autres peptides pourraient avoir un potentiel d'activité hypotensive, anti-amnésique, immunostimulant, opioïde et neurologique ce qui reste encore à confirmer.Les résultats indiquent que les graines d'alpiste des Canaries ont une teneur élevée en protéine digestible et ont potentiellement des effets exceptionnellement bénéfiques sur la santé, particulièrement contre les maladies cardiovasculaires, et devraient être considérées comme un aliment ou un ingrédient fonctionnel.

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