The structure of albumin 2 protein fraction of amaranth was investigated. It was formed by several major polypeptide subunits of molecular masses of 52.3 ± 0.8, 54 ± 2, and 56 ± 1 kDa. The former and the latter subunits were composed of a peptide of molecular mass between 31 and 38 kDa linked by S−S bonds with another peptide of molecular mass between 19 and 23 kDa. The 54 kDa subunit together with the 31−38 and 19−23 kDa subunits formed S−S-linked aggregated polypeptides. Lyophilized albumin 2 was highly polymerized, having a complex monomer component with a molecular mass of 300 ± 10 kDa. The polymers were partially stabilized by SS linkages. Because of these structural characteristics, albumin 2 was very similar to amarantin except for the presence of the 54 kDa subunit and its tendency to polymerize. Two components were obtained by gel filtration of globulin fraction. The major one exhibited heterogeneity of species and showed some common features with albumin 2. The minor component eluted at a lower volume and also showed heterogeneity, with a main species of 7S and a minor one of 12S. Their major peptides had molecular masses of 78, 72, 39, 30, and 20 kDa similar to the 7S type globulin. Its size, larger than that of amarantin, is different from a 7S type globulin, but the possibility of becoming polymerized or having a shape quite different from that of a sphere cannot be dismissed. Keywords: Amaranth; globulin; albumin 2; protein structure; gel filtration; electrophoresis

RuBisCO showed comparable or superior functional properties to those of currently used whey and soy protein isolates. These results highlight the high potential of sugar beet leaf protein isolate as a nutritious and functional food ingredient to face global food security and protein supply. © 2018 Society of Chemical Industry.

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The influence of pH and NaCl on the structure of globulin-P, the polymerizable amaranth 11S type globulin, was studied by differential scanning calorimetry, gel filtration, and gradient sedimentation. At μ = 0.54, the protein is stable for pH ranging from 5 to 9 but becomes rapidly unfolded as pH decreases below 5. For pH values above 9, globulin-P denatures more gradually than in acidic medium, and it also dissociates into subunits, which are possibly less thermostable. At pH 6.5 or 8.5 and low sodium chloride concentrations (μ ≤ 0.01), dialyzed globulin-P destabilizes, yielding species of lower thermal stability. The increase in NaCl concentration up to 0.1 M induces folding of globulin-P toward a more stable structure. Above 0.1 M NaCl, increasing the ionic strength up to μ = 0.5 elevates the denaturation temperature (T d) and denaturation enthalpy (ΔH). From μ = 0.1 to 0.5 the content of soluble globulin-P polymers decreases, possibly owing to protein insolubilization. Above 0.5 M, NaCl shows a stabilizing effect reflected by increasing T d, whereas ΔH stays constant; this effect is similar to that found by other authors in some storage proteins. Keywords: Amaranth; globulin; protein structure; gel filtration; ultracentrifugation; pH effect; ionic strength effect

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High-pressure treatment represents a potential method to stabilize microbiologically agricultural raw materials that are sensitive to heat treatments. Low-density lipoproteins (LDL), the main contributors to the exceptional emulsifying properties of yolk, are particularly sensitive to heat treatment. In this study, high-pressure treatments have been performed on LDL, and their impact on LDL physicochemical and emulsifying properties has been assessed. LDL dispersions at two pH levels (pH 3 and 8) were treated at different pressure levels: 200, 400, and 600 MPa at 20 degrees C. LDL dispersion characteristics (solubility, aggregation, and protein denaturation) and LDL emulsifying properties (o/w 30:70 emulsions: droplet size, flocculation, and protein adsorption) of nontreated and high-pressure treated dispersions were compared. Solubility is not altered by high-pressure treatment whatever the pH, whereas aggregation and protein denaturation are drastically enhanced, in particular at pH 8. The effects of these modifications on LDL emulsifying properties are mainly a diminution of the flocculation (depletion and bridging) at this same pH. Finally, it seems that high-pressure treatment combined with an alkaline pH decreases droplet flocculation of LDL dispersions.