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  1. Article ; Online: Rheological Behavior of Pectin Gels Obtained from Araçá ( Psidium cattleianum Sabine) Fruits

    Sarah da Costa Amaral / Denis Christophe D. Roux / François Caton / Marguerite Rinaudo / Shayla Fernanda Barbieri / Joana Léa Meira Silveira

    Polymers, Vol 14, Iss 16, p

    Influence of DM, Pectin and Calcium Concentrations

    2022  Volume 3285

    Abstract: In this work, purified pectins from Araçá fruits ( Psidium cattleianum Sabine) were obtained and characterized after partial demethylation. On each prepared sample, the carboxylic yield was obtained by titration, the degree of methylation (DM) by 1 H-NMR, ...

    Abstract In this work, purified pectins from Araçá fruits ( Psidium cattleianum Sabine) were obtained and characterized after partial demethylation. On each prepared sample, the carboxylic yield was obtained by titration, the degree of methylation (DM) by 1 H-NMR, and the molecular weight distribution by steric exclusion chromatography (SEC). Then, the gelation ability in the presence of calcium counterions was investigated and related to DM (59–0%); the pectin concentration (2–10 g L −1 ); and the CaCl 2 concentration (0.1–1 mol L −1 ) used for dialysis. The critical pectin concentration for homogeneous gelation was above 2 g L −1 when formed against 1 mol L −1 CaCl 2 . The elastic modulus (G′) increased with pectin concentration following the relationship G′~C 2.8 in agreement with rigid physical gel network predictions. The purified samples APP and APP-A with DM ≥ 40% in the same conditions released heterogeneous systems formed of large aggregates. Gels formed against lower concentrations of CaCl 2 down to 0.1 mol L −1 had a higher degree of swelling, indicating electrostatic repulsions between charged chains, thus, counterbalancing the Ca 2+ cross-linkage. Compression/traction experiments demonstrated that an irreversible change in the gel structure occurred during small compression with an enhancement of the G′ modulus.
    Keywords Araçá pectin ; de-esterification ; SEC characterization ; calcium gelation ; rheology ; Organic chemistry ; QD241-441
    Subject code 333
    Language English
    Publishing date 2022-08-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article: Accurate methodology to determine slip velocity, yield stress and the constitutive relation for molten chocolate

    Talansier, Emeline / Audrey Bacconnier / Carine Chastel / Denis C.D. Roux / Deniz Z. Gunes / François Caton / Lucy Costa

    Journal of food engineering. 2019 Mar., v. 244

    2019  

    Abstract: Concentrated soft materials like molten chocolate often has the ambiguity of behaving like a solid or a liquid depending on the external constraints. Determination of the constitutive relation is often unreliable and consequently the yield stress value ... ...

    Abstract Concentrated soft materials like molten chocolate often has the ambiguity of behaving like a solid or a liquid depending on the external constraints. Determination of the constitutive relation is often unreliable and consequently the yield stress value too. This difficulty of determining yield stress, particularly when using a standards protocol such as the IOCCC for chocolate, is a consequence of the presence of wall slip. Assessment of slip velocity using Yoshimura and Prud'homme's method most often leads to erroneous results. We propose to tackle this problem by using an easy and reliable methodology applied to a commercial chocolate in a melted state with, as equipment, a plate-plate rotational rheometer.This method allows precise determination of the yield stress value, the constitutive relation and the slip velocity versus the shear stress. Furthermore, it provides an explanation to the apparent Newtonian plateau and thickening behavior of the raw flow curve.
    Keywords chocolate ; equipment ; liquids ; melting ; protocols ; shear stress
    Language English
    Dates of publication 2019-03
    Size p. 220-227.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 622518-4
    ISSN 0260-8774
    ISSN 0260-8774
    DOI 10.1016/j.jfoodeng.2018.09.031
    Database NAL-Catalogue (AGRICOLA)

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