Sainfoin leaf condensed tannins inhibited growth and protease activity in Butyrivibriofibrisolvens A38 and Streptococcus bovis 45S1 but had little effect on Prevotella ruminicola B14 or Ruminobacter amylophilus WP225. Tannins bound to cell coat polymers in all strains. implicated the cell wall as a target of tannin toxicity. Morphological changes in B. fibrisolvens and S. bovis Condensed tannins (CTs) are generally regarded as antinutritional for ruminants because of depression of feed intake and dry matter digestibility (13, 24), but their capacity to precipitate proteins reversibly at rumen pH may be nutritionally beneficial (14, 15, 20). When CT-containing herbage is masticated, insoluble CT-protein complexes are formed; these are stable over the pH range 3.5 to 7.0 but dissociate in the abomasum and anterior duodenum (11, 16). This protects the protein from microbial hydrolysis and deamination in the rumen and increases the proportion of plant amino acids available for postruminal absorption. Furthermore, the "bloatsafe" property of pasture legumes such as sainfoin (Onobrychis viciifolia Scop.) and birdsfoot trefoil (Lotus corniculatus L.) is correlated with CT content (14, 15). Most of the proteolytic activity of rumen contents resides with the bacterial fraction (3, 8, 17). Soluble plant proteins typically adsorb to the surface of proteolytic bacteria (21) and are hydrolyzed by constitutively expressed cell coat proteases (12, 22). Our objective was to determine some effects of CTs on growth and proteolysis by four strains of ruminal bacteria representing functionally important proteolytic species (23). The CTs used were purified (2) from leaves of sainfoin (cv. Melrose) and had a high protein-precipitating capacity compared with those of CTs from eight other forage legume sources (9). A single batch of sainfoin leaf CTs was used for all experiments. Effects of CTs on bacterial growth. Butyrivibrio fibrisolvens A38, Prevotella ruminicola B14, Ruminobacter amylophilus WP225, and Streptococcus bovis 45S1 were grown anaerobically (4) in a basal medium, which was the medium of Scott and
Canola is an economically important farm-gate crop in Canada. To further explore the potential of canola protein as value-added food and nutraceutical ingredients, a better understanding of fundamental properties of 2 major canola proteins is necessary. Two major protein components, cruciferin and napin, were isolated from defatted canola meal by Sephacryl S-300 gel filtration chromatography. SDS-PAGE showed that cruciferin consists of more than 10 polypeptides, and noncovalent links are more important than disulphide bonds in stabilizing the structural conformation. Napin consists of 2 polypeptides and is stabilized primarily by disulphide bonds. Purified cruciferin showed 1 major endothermic peak at 91 degrees C compared with that of 110 degrees C for napin. Emulsion prepared by cruciferin showed significant higher specific surface area and lower particle size than that of napin. The study indicated that the presence of napin could detrimentally affect the emulsion stability of canola protein isolates. Hydrolysates from cruciferin and napin showed potent angiotensin I-converting enzyme inhibitory activity (IC(50): 0.035 and 0.029 mg/mL, respectively), but weaker than that of canola protein isolate hydrolysate (IC(50): 0.015 mg/mL).
Abstract. In this study, the cellulose crystals, prepared by acid hydrolysis of flax fiber, consisted of slender rods with lengths ranging from 100 to 500 nm and diameters ranging from 10 to 30 nm, respectively. After mixing the suspension of flax cellulose nanocrystals (FCNs) and plasticized starch (PS), the nanocomposite films were obtained by the casting method. The effects of FCNs loading on the morphology, thermal behaviour, mechanical properties and water sensitivity of the films were investigated by means of wide-angle X-ray diffraction, differential scanning calorimetry, tensile testing, and water absorption testing. Scanning electron microscopy photographs of the failure surfaces clearly demonstrated a homogeneous dispersion of FCNs within the PS matrix and strong interfacial adherence between matrix and fillers, which led to an increase of glass transition temperature ascribed to the starch molecular chains in the starch-rich phase. In particular, these nanocomposite films exhibited a significant increase in tensile strength and Young's modulus from 3.9 to 11.9 MPa and from 31.9 to 498.2 MPa, respectively, with increasing FCNs content from 0 to 30 wt%. Also, with a loading of FCNs, the resulting nanocomposite films showed a higher water resistance. Therefore, FCNs played an important role in improving the mechanical properties and water resistance of the starch-based materials.
To identify simple screening tools for selecting condensed tannin (CT)-containing forages as candidate sources for further study, CT were isolated from nine legumes, and their molecular weights (MW), chromophore production, capacity to precipitate bovine serum albumin (BSA) and Fraction 1 protein (Rubisco) isolated from alfalfa, and inhibition of filter paper digestion were compared. Sources were as follows: leaves of sericea lespedeza (Lespedeza cuneata Dum.-Cours.), crown vetch (Coronilla varia L.), and sainfoin (Onobrychis viciifolia Scop.); stems of hedysarum (Hedysarum alpinum L.); seeds of alfalfa (Medicago sativa L.); and whole plants of birdsfoot trefoil (Lotus corniculatus var. corniculatus L.) and three varieties of big trefoil (Lotus pedunculatus Cav.), viz., Lotus uliginosus Schkuhr, L. uliginosus var. glabriusculus, and L. uliginosus var. villosus. Molecular weights and sizes (degrees of polymerization) of the CT varied considerably within and among plant species. Average MW ranged from 3036 Da (crown vetch) to 7143 Da (lespedeza). All CT exhibited greater capacity (w/w basis) to bind alfalfa Rubisco than BSA. Relative astringencies (microg CT required to precipitate 1 mg protein) against BSA ranged from 262.5 for CT from lespedeza to 435.5 for CT from L. corniculatus, and against Rubisco, from 49.6 (sainfoin) to 108.2 (alfalfa seed). Including CT at 300 microg/ml in cultures of Fibrobacter succinogenes reduced digestion of cellulose filter paper by 19.8% (sainfoin) to 92.4% (crown vetch) and increased the specific activity of cell-associated endoglucanase. There were no correlations between inhibitory effects of CT on filter paper digestion and (1) chromophore formation during CT assay by butanol-HCl, vanillin-HCl, or H2SO4; (2) precipitation of BSA or alfalfa Rubisco; and (3) MW of CT. The most inhibitory CT for cellulose digestion included those with broad and with narrow MW distributions. Sainfoin was the most desirable source of CT, as it had the highest capacity to bind alfalfa protein and was least inhibitory to cellulose digestion by F. succinogenes. This study suggests that these properties are not easily defined via chemical means, and that biological assays using rumen bacteria may help identify those CT with properties of nutritional interest.
Samples of commercially prepared white, whole wheat, flax, and multigrain breads were analyzed by a rapid RP-HPLC method for the presence of the lignan secoisolariciresinol diglucoside (SDG). SDG was detected only in products containing flax, with concentrations ranging from 0.06 to 1.98 microM/g of DW (19-602 microM/loaf). Full-fat flax meal, powdered aqueous alcohol extracts of flax seed, and SDG were added to a white bread mix and baked into loaves in a domestic bread maker. Quantitative recovery of SDG from the test breads was observed when SDG was added; however, when flax meal or aqueous alcohol extracts were added, only 73-75% of the theoretical yield of SDG was recovered. SDG was also detected in commercially prepared flax cookies, bagels, and muffins with concentrations ranging from 0.26 to 2.93 microM/g of DW. The extent of grinding of the flax seed was also shown to have a significant effect on the recovery of SDG from both flax meal breads and baked goods, with extraction of SDG from finely ground samples greater than that from course material.
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