Structuring and texturing gluten‑free pasta: egg albumen or whey proteins?

The effects of adding egg albumen or whey proteins to pasta made from parboiled rice flour (PR) were investigated. Pasta quality was evaluated in terms of color, furosine content, and cooking properties (water absorption, cooking loss, and consistency at the optimal cooking time). The surface heterogeneity of the cooked and uncooked materials was studied, and some starch properties (pasting properties and starch susceptibility to \u3b1-amylase hydrolysis) were assessed, along with the features of the protein network as determined by conditional solubility studies and with ultrastructural features of the cooked products. Egg albumen improved pasta appearance and gave a product with low cooking loss, firmer, and nutritionally more valuable than the other ones. In albumen-enriched pasta, small starch granules appear homogeneously surrounded by a protein network. In the uncooked product, the protein network is stabilized mostly by hydrophobic interactions, but additional disulfide interprotein bonds form upon cooking. Thus, addition of 15 % liquid albumen to PR results in significant improvement of the textural and structural features of rice-based gluten-free pasta

Effect of High-Pressure Processing on the Features of Wheat Milling By-products

The ability of high hydrostatic pressure processing to promote changes in both the structural properties of fiber and the interaction of fiber with water were addressed. Both coarse and fine bran from milling of common wheat were considered. Treatment-induced morphological changes were most pronounced in fine bran, whereas treatment of coarse bran resulted in the largest change in water-holding capacity. The significance of the process-induced changes is discussed in terms of their practical relevance in the production of fiber-enriched foods

Concurrent structural and biophysical traits link with immunoglobulin light chains amyloid propensity

Light chain amyloidosis (AL), the most common systemic amyloidosis, is caused by the overproduction and the aggregation of monoclonal immunoglobulin light chains (LC) in target organs. Due to genetic rearrangement and somatic hypermutation, virtually, each AL patient presents a different amyloidogenic LC. Because of such complexity, the fine molecular determinants of LC aggregation propensity and proteotoxicity are, to date, unclear; significantly, their decoding requires investigating large sets of cases. Aiming to achieve generalizable observations, we systematically characterised a pool of thirteen sequence-diverse full length LCs. Eight amyloidogenic LCs were selected as responsible for severe cardiac symptoms in patients; five non-amyloidogenic LCs were isolated from patients affected by multiple myeloma. Our comprehensive approach (consisting of spectroscopic techniques, limited proteolysis, and X-ray crystallography) shows that low fold stability and high protein dynamics correlate with amyloidogenic LCs, while hydrophobicity, structural rearrangements and nature of the LC dimeric association interface (as observed in seven crystal structures here presented) do not appear to play a significant role in defining amyloid propensity. Based on the structural and biophysical data, our results highlight shared properties driving LC amyloid propensity, and these data will be instrumental for the design of synthetic inhibitors of LC aggregation

Antilisterial Bacteriocins for Food Security: The Case of Sakacin A

Sakacin A, a class IIa bacteriocin produced by Lactobacillus sakei, is a 41 amino acids peptide possessing a strong antilisterial activity, acting by permeabilizing cell membrane through the formation of pores. Due to its antimicrobial effectiveness, sakacin A possesses a significant potential as biopreservative. In the present chapter, different methods of applying bacteriocins to food are discussed: the direct use of the sakacin A-producing bacterium, as well as the addition of the purified or semi-purified peptide, even incorporated in an active packaging device to control its release during food storage

Effetto delle condizioni di pastificazione sulle caratteristiche macromolecolari di paste di riso

Attualmente, la produzione di pasta gluten-free si basa su approcci empirici, in cui ingredienti e/o condizioni di processo vengono variati senza conoscere come le modificazioni delle organizzazioni macromolecolari, ed in particolare dell\u2019amido, siano associabili al comportamento in cottura. Il presente lavoro ha previsto lo studio della struttura dell\u2019amido in paste di riso in funzione delle materie prime e del processo di pastificazione, indagando l'accessibilit\ue0 dell\u2019amido a specifici enzimi (\u3b1-amilasi e pullulanasi). I campioni di pasta sono stati preparti utilizzando farina di riso tal quale attraverso un processo di cottura-estrusione (Pasta A) e farina di riso parboiled mediante estrusione convenzionale (Pasta B) o cottura-estrusione (Pasta C). L\u2019accessibilit\ue0 dell\u2019amido \ue8 stata valutata sia quantitativamente come glucosio rilasciato dopo 1 e 24h di idrolisi, che qualitativamente valutando mediante Light Scattering e cromatografia di gel-permeazione le propriet\ue0 molecolari dei frammenti rilasciati. La suscettibilit\ue0 dell\u2019amido all\u2019\u3b1-amilasi aumenta sia per effetto del pretrattamento che del processo di pastificazione. La limitata quantit\ue0 di glucosio rilasciata dopo 24h di idrolisi del campione A, rispetto alla pasta B e C, suggerisce che la cottura-estrusione, se condotta sulla farina di riso tal quale, non permette la completa accessibilit\ue0 dell'amido. Il medesimo processo di cottura-estrusione su farina di riso parboiled (campione C) promuove la formazione di una struttura amilacea pi\uf9 compatta, meno accessibibile all\u2019\u3b1-amilasi (1h di idrolisi) e alla pullulanasi, giustificando l\u2019elevata consistenza (determinata con dinamometro) della pasta C dopo cottura al tempo ottimale. La pullulanasi rilascia in minor misura di- e trisaccaridi dal campione di Pasta A, indicando che parboiling e cottura-estrusione hanno effetti diversi sulla struttura dell\u2019amido. Da un punto di vista metodologico, l'approccio presentato sembra in grado di fornire indicazioni utili per migliorare la comprensione a livello molecolare degli effetti delle condizioni di pastificazione sulle propriet\ue0 dell\u2019amido e sulla qualit\ue0 in cottura della pasta. Questo lavoro \ue8 stato parzialmente supportato dalla Global Rice Science Partnership, Progetto "New Products"

Structural changes in emulsion-bound bovine beta-lactoglobulin affect its proteolysis and immunoreactivity

Adsorption on the surface of sub-micrometric oil droplets resulted in significant changes in the tertiary structure of bovine beta-lactoglobulin (BLG), a whey protein broadly used as a food ingredient and a major food allergen. The adsorbed protein had increased sensitivity to trypsin, and increased immunoreactivity towards specific monoclonal antibodies. In spite of the extensive tryptic breakdown of emulsion-bound BLG, some sequence stretches in BLG became trypsin-insensitive upon absorption of the protein on the fat droplets. As a consequence \u2013 at contrast with free BLG \u2013 proteolysis of emulsion-bound BLG did not decrease the immunoreactivity of the protein, and some of the large peptides generated by trypsinolysis of emulsion-bound BLG were still recognizable by specific monoclonal antibodies. Structural changes occurring in emulsion-bound BLG and their consequences are discussed in comparison with those occurring when the tertiary structure of BLG is modified by lipophilic salts, by urea, or upon interaction with solid hydrophobic surfaces. Such a comparison highlights the relevance of situation-specific structural modifications, that in turn may affect physiologically relevant features of the protein

Electrostatics of folded and unfolded bovine beta-lactoglobulin

We report on electrophoretic, spectroscopic, and computational studies aimed at clarifying, at atomic resolution, the electrostatics of folded and unfolded bovine beta-lactoglobulin (BLG) with a detailed characterization of the specific aminoacids involved. The procedures we used involved denaturant gradient gel electrophoresis, isoelectric focusing, electrophoretic titration curves, circular dichroism and fluorescence spectra in the presence of increasing concentrations of urea (up to 8 M), electrostatics computations and low-mode molecular dynamics. Discrepancy between electrophoretic and spectroscopic evidence suggests that changes in mobility induced by urea are not just the result of changes in gyration radius upon unfolding. Electrophoretic titration curves run across a pH range of 3.5-9 in the presence of urea suggest that more than one aminoacid residue may have anomalous pK (a) value in native BLG. Detailed computational studies indicate a shift in pKa of Glu44, Glu89, and Glu114, mainly due to changes in global and local desolvation. For His161, the formation of hydrogen bond(s) could add up to desolvation contributions. However, since His161 is at the C terminus, the end-effect associated to the solvated form strongly influences its pK (a) value with extreme variation between crystal structures on one side and NMR or low-mode molecular dynamics structures on the other. The urea concentration effective in BLG unfolding depends on pH, with higher stability of the protein at lower pH

Binding of Aflatoxin M1 to the different protein fractions in ovine and caprine milk

The affinity of aflatoxin M1 toward the main milk protein fractions in ewe and goat milk was investigated by using an ELISA. This study took into account the possible effects of common dairy processes such as ultrafiltration, acidic or rennet curding, and production of ricotta from acidic or rennet whey. Treatments that allowed the separation of casein from whey proteins under conditions that do not alter the physical or chemical status of the proteins (such as ultracentrifugation) were used as a reference. None of the treatments used in typical dairy processes caused significant release of the toxin, in spite of the relevant changes they induced in the interactions among proteins. Only the combined heat and acidic treatment used for production of ricotta cheese altered the structure of whey proteins to the point where they lost their ability to bind the toxin. This study also showed that, regardless of the physical state of the sample, a commercial electronic nose device, in combination with appropriate statistical tools, was able to discriminate among different levels of sample contamination

Prion protein structure is affected by pH-dependent interaction with membranes : a study in a model system

Interaction of full length recombinant hamster prion protein with liposomes mimicking lipid rafts or non-raft membrane regions was studied by circular dichroism, chemical cross-linking and sucrose gradient ultracentrifugation. At pH 7.0, the protein bound palmitoyloleoylphosphatidylcholine/cholesterol/sphingomyelin/monosialoganglioside GM1 (GM1) ganglioside liposomes but not palmitoyloleoylphosphatidylcholine alone (bound/free = 0.33 and 0.01, respectively), maintaining the native α-helical structure and monomeric form. At pH 5.0, though still binding to quaternary mixtures, in particular GM1, the protein bound also to palmitoyloleoylphosphatidylcholine (bound/free 0.35) becoming unfolded and oligomeric. The pH-dependent interaction with raft or non-raft membranes might have implication in vivo, by stabilizing or destabilizing the protein