Browsing by Author "Freitas, Victor de"
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- Deciphering the potential of orange peel polysaccharides for modulating black tea astringencyPublication . Vieira, Joana; Silva, Inês E.; Guerreiro, Carlos; Bravo, Carlo; Rinaldi, Alessandra; Ramos, Rui M.; Fernandes, Pedro A. R.; Coimbra, Manuel A.; Fernandes, Virgínia Cruz; Freitas, Victor de; Brandão, Elsa; Soares, Susana; Fernandes, VirgíniaAstringency: a complex oral sensation described as dryness, puckering, or tightening - limit consumer acceptance of polyphenol-rich products like black tea, with recognized health benefits. Traditional strategies, such as sugar addition or polyphenol removal, often compromise nutritional quality, highlighting the need for alternative approaches to modulate astringency. One promising strategy involves the use of pectic polysaccharides as modulators of polyphenol-oral constituents interactions. This study explored two pectic polysaccharides fractions (PPFs) from orange peels with different composition on the interactions between black tea polyphenols and oral constituents, using an advanced oral cell-based quaternary model and trained sensory panel. PPF1 had a high degree of methylesterification (88 %) and high molecular weight (1.004 kDa), while PPF2 had a low degree of methylesterification and low molecular weight (226 kDa). Both fractions exhibited high uronic acid content, 72–80 mol%, respectively. Results: showed that PPFs decreased black tea polyphenols-oral constituents interactions, particularly in the HSC- 3-Mu-SP model (HSC-3 tongue-derived cell line, mucosal pellicle, salivary proteins). Notably, PPF2 showed a greater effect (53 % reduction) of total polyphenols adsorbed (UV–Vis colorimetric assay) and decreased the adsorption of all individual polyphenols, with the stronger effect on theasinensin C (56 % reduction) (HPLC analysis). PPF2 also decreased cystatins–oral component interactions (64 % reduction). Conversely, PPF1 showed a reducing effect on theaflavin-3,3′-digallate adsorption (24 %) and on gRPPs/aPRPs precipitation (33–38 %). Sensory analysis corroborated that both PPFs reduced astringency perception of black tea and contributed to positive astringency subqualities: silkiness associated with high molecular weight and mouthcoating associated with high uronic acid content.
- Molecular Imprinting of Complex Matrices at Localized Surface Plasmon Resonance Biosensors for Screening of Global Interactions of Polyphenols and ProteinsPublication . Guerreiro, Joana Rafaela Lara; Bochenkov, Vladimir E.; Runager, Kasper; Aslan, Hüsnü; Dong, Mingdong; Enghild, Jan J.; Freitas, Victor de; Sales, M. Goreti F.; Sutherland, Duncan S.Molecular imprinting polymers (MIP) have been applied to capture and stabilize complex protein matrices at plasmonic sensor surfaces. Ultrathin MIP layers at the surface of gold nanodisks enable the label free quantification of global interactions of polyphenols with protein mixtures. Separate polyphenols (catechin, procyanidin B3- catechin dimer, and PGG-pentagalloyl glucose) give specific and different binding levels to the MIP supported saliva plasmonic sensor. The demonstrated biosensor has application to study bioavailability of polyphenols or evaluation of local retention of small drug molecules.
- Wine astringent compounds monitored by an electrochemical biosensorPublication . Costa, Joana J.; Moreira, Felismina; Soares, Susana; Brandão, Elsa; Mateus, Nuno; Freitas, Victor de; Sales, GoretiAn innovative approach for monitoring astringent polyphenols in beverages (wines) is described, consisting of an electrochemical biosensor constructed by adsorbing salivary α-amylase or proline-rich protein (PRP) onto amined gold screen-printed electrodes. Interaction with polyphenols was tested using pentagalloyl glucose (PGG) as a standard, an important representative element for astringency. The analytical properties of the resulting biosensors were evaluated by electrochemical impedance spectroscopy at different pHs. The PRP-biosensor was able to bind to PGG with higher sensitivity, displaying lower limit of the linear range of 0.6 μM. Wine samples were tested to prove the concept and the concentrations obtained ranged from 0.17 to 4.7 μM, as expressed in PGG units. The effects of side-compounds on PRP and on α-amylase binding to PGG were tested (gallic acid, catechin, ethanol, glucose, fructose and glycerol) and considered negligible. Overall, concentrations > 1.0 μM in PGG units are signaling electrochemical impedance, providing a quantitative monitoring of astringent compounds.