1,720,966 research outputs found
Lysozyme immobilized on chitosan beads: Kinetic characterization and antimicrobial activity in white wines
No full textCatalytic properties of lipoxygenase extracted from different varieties of Pisum sativum and Lens culinaris
No full textLipoxygenase (LOX, E.C. 1.13.11.12), among its various roles, catalyzes the degradation of polyunsaturated fatty acids and it is considered to be one of the main causes of undesirable off-flavor developments in legumes. The role of LOX in postharvest physiology is particularly significant in seeds with high values of lipoxygenase and linoleic acid levels. This research aimed to study the biochemical properties of the LOX extracted from green pea (Pisum sativum L. var. Léda, Zeusz, Zsuzsi), dry pea (Pisum sativum L. var. Hanka, Irina, Lutra), and lentil (Lens culinaris L., var. Pinklevi, Rézi, Castelluccio), using linoleic acid as a substrate. The raw extracts showed different catalytic properties, with dry pea (var. Irina) that expressed the highest LOX activity, while lentil (var. Pinklevi) expressed the lowest activity. To complete the biochemical characterization of the crude LOX extracts, their optimal pH and temperature were also examined. The highest value of lipoxygenase activity in the pH range 6–7 was measured in all legumes. The optimal temperature for all extracts fell within the range of 30–60°C given the nutritional importance of legumes. This study will serve as a basis for further detailed investigation of the legumes LOX activity and its roles in food products related to legumes. Practical applications: This study investigated the biochemical properties of lipoxygenase (LOX) extracted from different varieties of lentil and pea, the two important leguminous crops serving as the main protein source for the population of humans worldwide. The biochemical properties of LOX extracted from legumes showed large differences in terms of kinetic properties. The results of this study revealed that the use of lipoxygenase can be a suitable index for managing stabilization techniques of lentil and pea, in order to inhibit the lipid oxidation in grain legume without compromising its nutritional value
Chitosan/clay nanocomposite films as supports for enzyme immobilization: an innovative green approach for winemaking applications
No full textEvolution of S-cysteinylated and S-glutathionylated thiol precursors during grape ripening of Vitis viniferaL. cvs Grechetto, Malvasia del Lazio and Sauvignon Blanc
No full textBackground and Aims: Varietal thiols, important odorous molecules in wine, have been identified in Vitis viniferaL. grapes as S-cysteinylated and S-glutathionylated odourless precursors. The aim of this paper is to investigate the presence of these precursor compounds during ripening of two Italian white grape cultivars, Grechetto and Malvasia del Lazio, in comparison with the well-characterised, reference cultivar Sauvignon Blanc. Methods and Results: Grapes were sampled and sorted according to density in order to obtain homogeneous samples at the TSS concentration of 16, 19 and 22°Brix, as a synthetic index of ripening stage. After sorting and processing the grapes, the concentration of thiol precursors contained in each sample of juice was determined by liquid chromatography-quadrupole MS. For the first time, S-3-(4-sulfanyl-4-methylpentan-2-ol)-glutathione was identified and quantified in the three cultivars as a glutathione-conjugated precursor. Both S-cysteinylated and S-glutathionylated precursors were ubiquitous in the three cultivars, although their concentration varied significantly. Conclusion: Thiol precursors increased with TSS during ripening in Sauvignon Blanc and Grechetto, while no variation of these odourless compounds was observed in Malvasia del Lazio, which also had a lower concentration of these precursors. Significance of the Study: This work contributes to defining the significance of these precursors to the varietal attributes of the resulting wines, as well as indicating the optimal harvest time of grapes for maximal expression of thiol varietal attributes in wine
Kinetic study of a hen-egg white lysozyme-based oenological preparation
No full textThe catalytic activity of a lysozyme-based oenological preparation toward the specific substrates i) glycol chitosan, as a non-cellular synthetic substrate, and ii) Oenococcus oeni, as a microbial substrate for muramidase activity, was investigated in wine-like acidic medium (tartaric buffer, pH 3.2). The good reproducibility and reliability of results revealed that both substrates are useful for lysozyme kinetics studies. Both the chitinolytic and muramidase activity of lysozyme were affected by uncompetitive substrate inhibition. However, the O. oeni effect occurred at very high concentration with respect to the typical wine bacterial content, even when microbial population reaches its maximum growth level during malolactic fermentation. The optimum pH and temperature for lysozyme activity were very far from the usual wine handling conditions, but residual enzyme activity was observed at pH 3.2 and 20°C, confirming that the oenological application of lysozyme is a useful practice
Thiol precursors in Grechetto grape juice and aromatic expression in wine
No full textThe contribution of cysteine and glutathione conjugates to the formation of thiol compounds in Grechetto wine has been evaluated for the first time, by the use of quantitative GC–MS analysis and odour activity values, as a function of the training system (either Royat cordon or simple Guyot) that was used for the vines. The concentration of conjugate precursors in the grape juice, in the case of both training systems, was found to increase significantly until 22°Brix, except for glutathionylated precursor of 4-methyl-4-sulfanyl-pentan-2-one. The amount of both thiol precursor forms was systematically higher for the Royat cordon system that seems to improve the accumulation of thiol precursors. However, this high juice concentration did not reveal an high content of volatile thiols in derived wine. 4-Methyl-4-sulfanyl-pentan-2-one (4MSP), 3-sulfanylhexan-1-ol (3SH) and 3-sulfanylhexyl acetate (3SHA) have been identified as aroma compounds in both two monovarietal white wines from Grechetto grape, but only the amounts of 4MSP and 3SHA turned out to be considerably higher than their respective perception thresholds. Considering the growing interest in the varietal wines characteristics on the part of consumers, the results of present work could be useful to improve the scientific knowledge about the relationships between the grape content and wine composition
Bromelain immobilization on microbial and animal source chitosan films, plasticized with glycerol, for application in wine-like medium: Microstructural, mechanical and catalytic characterisations
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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